JP2004335689A - Slurry for polishing copper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide slurry for polishing copper which has a quick polishing speed and in which scratches are remarkably suppressed. <P>SOLUTION: The slurry for polishing copper is used to manufacture a semiconductor device using copper. The slurry contains organic particles having a functional group of 0.1 to 10 mmol/g which reacts with copper under the polishing condition of a semiconductor, an oxidizing agent, a complexing agent and water. The organic particles are preferably made of resin having at least one type of functional group or its neutralization object selected from the group consisting of a carboxyl group, a hydroxyl group, carbonyl group, aldehyde group, acetyl group, amino group, nitro group, amide group, cyano group, azo group, an imino group and a glycidyl group. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００５３】
【発明の効果】
本発明の研磨スラリーを用いることにより、有機粒子と銅との化学反応が促進され、配線加工された絶縁膜上の過剰な銅膜を早い速度で研磨することができる。さらに、被研磨物表面に、研磨過剰による傷やスクラッチを発生することなく研磨することができ、ディッシングやエロージョンなどの凹凸がなく平坦性が高い研磨が可能となる。
【００５４】
また、本発明の研磨用スラリーは、時間経過による分離（上澄み、沈殿の生成）、凝集体生成が起こらず、保存安定性に優れるので、常に安定した研磨速度が得られる。
【００５５】
さらに、本発明の研磨用スラリーは、固形分が絶縁膜よりも分解温度がかなり低い有機微粒子であるので、熱処理、プラズマ処理で、絶縁膜にダメージを与えず、研磨用スラリーの残存物の除去が可能である。その結果、研磨用スラリー中の固形分が絶縁膜上に残存するために起る、絶縁膜層全体の誘電率の上昇を防ぐことができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a polishing slurry used for polishing copper in the manufacture of wiring for semiconductor devices.
[0002]
[Prior art]
In recent years, in the wiring process of semiconductor device manufacturing, a groove for forming a wiring is formed on an insulating film, a copper film for the wiring is buried by a plating method, an excess copper film is removed, and an insulating film including a copper wiring is removed. (Chemical and Mechanical Polishing) has been used as a technique for flattening. This is a method of mechanically polishing with a slurry in which abrasive grains are dispersed.
[0003]
In the CMP technique, a slurry containing a metal oxide such as ceria or alumina or an inorganic abrasive such as silica has been used. However, these inorganic abrasive grains have high hardness, and when polishing a metal film having low hardness such as copper, polishing scratches on the metal surface called scratches are a major problem.
[0004]
At present, in order to improve the performance of semiconductors, the width of a half wiring on an insulating film has been further miniaturized from 130 nm to 90 nm and further to 65 nm, and the surface of the insulating film to be polished has a more complicated structure. Has become. As the wiring width becomes finer, polishing scratches on the metal surface due to scratches cause disconnections and short-circuits between wirings, significantly lowering the reliability of the semiconductor device and significantly lowering the yield.
[0005]
This scratch is caused by the hardness of the abrasive grains and partial overpolishing caused by the presence of aggregates of the abrasive grains.
[0006]
In order to solve these problems, a polishing solution for polishing the abrasive grains with inorganic silica, which is softer than alumina, is being developed. For example, when silica is used as abrasive grains, scratches are reduced as compared with alumina. However, when inorganic abrasive grains are used, generation of scratches, dishing, and erosion cannot be prevented, and is not a fundamental solution.
[0007]
Japanese Patent No. 3172008 describes a method in which particles of an organic polymer compound are used as abrasive grains. Since the organic polymer used here uses a component having no functional group such as methacrylic resin and polystyrene resin as abrasive grains, and does not contain an oxidizing agent that oxidizes the surface of a metal, the object to be polished is Does not work at all with the metal film, and a sufficient polishing rate required for the wiring process in the manufacture of semiconductor devices has not been obtained. In addition, when the organic polymer that is the abrasive particles does not have a functional group, poor dispersibility in a solvent used as a main component is poor, and occurrence of uneven polishing resulting from generation of an aggregate of particles partially, and Variations in the polishing rate pose a problem. Further, when the storage is performed for a long period of one week or more, there is a problem that precipitation occurs.
[0008]
[Problems to be solved by the invention]
The present invention has water as a main component, organic particles having a functional group that reacts with copper, an oxidizing agent, a copper polishing slurry containing a complexing agent, which promotes the reaction between the organic particles and copper, It is an object of the present invention to provide a polishing slurry that can increase the polishing rate and significantly suppresses the generation of scratches, which is a problem when inorganic particles are used as abrasive grains even when the polishing rate is increased.
[0009]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve the above problems, and as a result, completed the present invention. That is, the polishing slurry of the present invention,
(1) A polishing slurry used for manufacturing a semiconductor device having copper, wherein organic particles containing a functional group that reacts with copper in a semiconductor polishing condition at 0.1 mmol / g or more and 10 mmol / g or less, A slurry for polishing copper, comprising an oxidizing agent, a complexing agent, and water.
[0010]
(2) The organic particles are at least one functional group selected from carboxyl group, hydroxyl group, carbonyl group, aldehyde group, acetyl group, amino group, nitro group, amide group, cyano group, azo group, imino group or neutralization thereof. The slurry for copper polishing according to the above (1), comprising a resin having an object, is a preferred embodiment of the present invention.
[0011]
(3) The copper polishing slurry according to the above (1) or (2), wherein the organic particles are an acrylic emulsion resin dispersed in a water solvent, is a preferred embodiment of the present invention.
[0012]
(4) The complexing agent according to any one of (1) to (3), wherein the complexing agent is at least one compound selected from carboxylic acids, amines, amino acids, alcohols, ketones, and aldehydes. Is a preferred embodiment of the present invention.
[0013]
(5) The copper polishing slurry according to any one of (1) to (4), wherein the oxidizing agent is hydrogen peroxide, is a preferred embodiment of the present invention.
[0014]
(6) The copper polishing slurry according to any one of (1) to (5), wherein the average particle size of the organic particles is 0.01 to 5 μm, is a preferred embodiment of the present invention.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described specifically.
(Organic particles)
The organic particles have a functional group that reacts with copper under semiconductor polishing conditions. This reaction is a reaction to form a complex. Examples of the functional group capable of forming a complex with copper include a carboxyl group, a hydroxyl group, a carbonyl group, an aldehyde group, an acetyl group, an amino group, a nitro group, an amide group, a cyano group, an azo group, an imino group, and a glycidyl group. . Among these, a carboxyl group is particularly preferred.
[0016]
The content of the functional group is required to be 0.1 mmol or more and 10 mmol or less per 1 g of organic particles, and preferably 0.3 mmol or more and 8 mmol or less per 1 g of organic particles. Within this range, the reaction with copper proceeds, and a desired polishing rate can be obtained. On the other hand, if it is too much, it becomes soluble in water and cannot be present as particles.
[0017]
The organic particles can be produced, for example, by emulsion polymerization of an unsaturated carboxylic acid and a vinyl monomer copolymerizable therewith. Then, by adding an alkaline substance of 0.3 molar equivalent or more to the unsaturated carboxylic acid in the obtained copolymer emulsion, the carboxylic acid group is dissociated to make it easy to form a complex with copper. I do.
[0018]
Unsaturated carboxylic acids suitably used in the present invention include, for example, unsaturated monobasic acids such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, unsaturated dibasic acids such as maleic acid, and monocarboxylic acids thereof. One or more selected from esters are mentioned, and acrylic acid and methacrylic acid are particularly preferred.
[0019]
The amount of these unsaturated carboxylic acids to be used is preferably 1 to 50 parts by mass, more preferably 3 to 20 parts by mass, even more preferably 5 to 15 parts by mass based on 100 parts by mass of all the monomer components in the copolymer. is there. Within this range, the desired polishing rate can be obtained and the water resistance and the alkali resistance are excellent.
[0020]
Examples of the vinyl monomer copolymerizable with the unsaturated carboxylic acid include aromatic vinyl compounds such as styrene, α-methylstyrene and vinyltoluene, methyl (meth) acrylate, ethyl (meth) acrylate, (Meth) acrylates such as butyl (meth) acrylate, vinyl esters such as vinyl acetate and vinyl propionate, vinyl cyanide compounds such as (meth) acrylonitrile, and vinyl halide compounds such as vinyl chloride and vinylidene chloride. Can be used.
[0021]
In addition, as the functional group monomer, (meth) acrylamide or N-methylol (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, glycidyl (meth) acrylate, or the like can be used, if necessary, in addition to the unsaturated carboxylic acid. .
[0022]
The amount of the vinyl monomer to be used is 99 to 50% by mass, preferably 95 to 70% by mass, based on all the monomers to be polymerized.
[0023]
Such organic particles may or may not swell as a whole by adding an alkaline substance, and either of them may be used. The term “swelling” as used herein means that the average particle diameter of the primary particles is increased by including water and other water-soluble substances in the particles without decomposition or aggregation.
[0024]
In the alkaline region, the organic particles may aggregate and settle due to swelling over time, so that the degree of swelling of the organic particles can be adjusted by adding an alkali. it can. Examples of the crosslinkable monomer include monomers containing two or more polymerizable unsaturated bonds in one molecule, such as divinylbenzene, ethylene glycol dimethacrylate, trimethylol aroban trimethacrylate, and ethylene glycol. Examples thereof include diacrylate, 1,3-butylene glycol dimethacrylate, and diacrylate. The amount of the crosslinkable monomer used is preferably 20% by mass or less, more preferably 10% by mass or less, based on all the monomers to be polymerized. It is appropriately adjusted depending on the type of the polymer and the like.
The organic particles may be used alone or in a combination of two or more.
[0025]
The content of the organic particles in the polishing slurry varies depending on the organic fine particles, but is usually preferably 0.1 to 20% by mass. Within this range, the effect of the organic particles is sufficiently exhibited, and the desired polishing rate can be achieved. If the content of the organic particles is too high, the viscosity of the polishing slurry increases, making it difficult to supply the slurry at a constant rate.
[0026]
(Dissociation of carboxylic acid in organic particles)
Examples of the alkaline substance used when the organic particles are used in a state in which the carboxylic acid group is partially or completely dissociated include inorganic substances such as sodium hydroxide, potassium hydroxide, calcium hydroxide, and sodium silicate. Alkaline substances, volatile alkaline substances such as ammonia, and organic alkaline substances such as dimethylethanolamine, triethylamine, and triethanolamine can be used.
[0027]
The amount used is preferably 0.1 equivalent or more and 10 equivalents or less with respect to 1 equivalent of the unsaturated carboxylic acid monomer unit contained in the copolymer constituting the organic particles.
[0028]
When the amount of the alkaline substance used is within this range, the amount of dissociated carboxylic acid groups is sufficient, and the complex formation reaction with the metal to be polished is carried out quickly, and the desired polishing ability is obtained.
[0029]
(Complexing agent)
Examples of complexing agents capable of forming a complex with copper include carboxylic acids such as acetic acid, oxalic acid, malic acid, tartaric acid, succinic acid, and citric acid; and amines such as methylamine, dimethylamine, triethylamine, ethylamine, diethylamine, and triethylamine. And amino acids such as glycine, aspartic acid, glutamic acid, and cysteine; ketones such as acetylacetone; and N-containing cyclic compounds such as imidazole. Of these, ammonia, oxalic acid, malic acid, and ethylamine are preferred, and ammonia and oxalic acid are particularly preferred.
[0030]
The content of the complexing agent varies depending on the type of the complexing agent, but is usually preferably in the range of 0.1 to 10% by mass in the polishing slurry. Within this range, the effect of the complexing agent can be sufficiently exerted, a desired polishing rate can be achieved, and dishing in which the metal to be polished out of the polishing target elutes can be suppressed.
[0031]
The copper of the object to be polished forms a complex with the functional group contained in the organic fine particles, and also forms a copper complex with the above-mentioned complexing agent, whereby good copper polishing is performed. The copper complex may be one in which the ligand is composed of organic fine particles and a complexing agent, or may be a state in which the formation of the organic fine particles-copper complex promotes the complexing agent-copper complex formation. Alternatively, the complexing agent-copper complex formation may promote organic fine particle-copper complex formation.
[0032]
(Oxidant)
As the oxidizing agent, hydrogen peroxide is preferably used. The content of the oxidizing agent in the polishing slurry is preferably in the range of 0.1 to 15% by mass, and particularly preferably in the range of 0.5 to 5% by mass. Within this range, the chemical reaction between the copper and the organic particles proceeds, and the oxide film formed on the copper surface does not passivate, so that the desired polishing rate can be achieved.
[0033]
(PH)
The polishing slurry of the present invention generally has a pH of 3 to 11, preferably 4 to 9. Within this range, the elution of copper can be suppressed, and there is no occurrence of a phenomenon called dishing, in which the copper film in the wiring portion is more polished at the center and formed in a concave shape. In addition, the insulating film is not dissolved or partially decomposed at the point where the semiconductor insulating film and the copper wiring, which are the final points of the copper film polishing, are on the same surface.
[0034]
The substance used for adjusting the pH of the polishing slurry is not particularly limited. Examples of the alkaline substance include ammonia, amines such as triethylamine, diethylamine, ethylamine, trimethylamine, dimethylamine and methylamine, and inorganic substances such as NaOH and KOH. And the like. Examples of the acidic substance include inorganics such as hydrochloric acid and nitric acid, and organic acids such as acetic acid, oxalic acid, and citric acid. These pH adjusters may also serve as complexing agents which can serve as the copper ligands described above. In addition, these substances may be used in combination of two or more kinds.
[0035]
(Method of manufacturing polishing slurry)
Preparation of the polishing slurry is performed by mixing organic fine particles, a complexing agent, and water and adjusting the pH. Although this production method is not particularly limited, a preferred method is to add an aqueous solution of a complexing agent capable of forming a ligand with a pH-adjusted copper to a pH-adjusted resin emulsion, and mix well. Thereafter, the oxidizing agent is gradually added, followed by stirring and mixing. After the final adjustment of pH and concentration, a method of removing undissolved substances and aggregates by filter paper filtration to obtain a polishing slurry can be mentioned.
[0036]
(Other additives)
In addition, halides containing chlorine, fluorine, and iodine as polishing accelerators, and nitrogen-containing heterocyclic compounds such as benzotriazole and quinaldic acid as protective films for copper wiring in portions where polishing and corrosion are to be avoided, and polyacrylic Substances such as acids, polyvinyl alcohol, water-soluble polymers such as polyethylene glycol and glucose, and surfactants may be added alone or in combination of two or more. The amount and type of addition are not particularly limited as long as the object of the present invention can be achieved.
[0037]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples. In the examples, parts and% represent parts by mass and% by mass, respectively, unless otherwise specified.
[0038]
The particle size distribution of the organic particles in the polishing slurry was measured by the following method.
<Organic particle size distribution measurement>
Particle size distribution measurement method using laser dynamic light scattering principle.
Measuring device: MICROTRAC UPA MODEL: 9230 (manufactured by Leeds & Northrup),
Concentration conditions: sample stock solution,
Measurement time: 900 seconds.
[0039]
The evaluation of the polishing slurry was performed by the following method.
1. Polishing rate polishing slurry: polishing slurry of the present invention,
Object to be polished: Thermal oxide film (5000 Å) formed by sputtering method, Ta film (300 Å) formed by CVD method, seed copper film for plating (1500 銅) and copper film (15000 Å) formed by plating method. 8 inch silicon wafers stacked in this order,
Polishing device: Ekomet 3, Automet 2 (manufactured by BUEHLER),
Polishing pad: 8 inch IC-1000 / suba400 grid,
Polishing load: 750 g / cm ² ,
Polishing time: 10 min,
Slurry supply rate: 13 cc / min,
Platen rotation speed: 50 rpm,
Number of rotations on the substrate side: 60 rpm.
[0040]
<Polishing rate calculation>
After the object to be polished was washed with ultrapure water and ultrasonic cleaning, it was dried, and the film thickness before and after polishing was measured at three places by sheet resistance measurement using a four-terminal probe. The average polishing rate was calculated from the change in the average film thickness and the polishing time.
[0041]
2. After the object to be polished after the surface defect polishing was washed and dried with ultrapure water, the surface was observed at three times with a differential interference microscope at a magnification of 2500 times. Incidentally, scratches on the surface having a length of 0.1 μm or more were judged as scratches. The symbols in Table 1 are based on the following criteria.
：: 5 or less scratches and scratches on average
X: The number of scratches and scratches exceeds 5 on average.
[0042]
3. Evaluation of Storage Stability The polishing slurry was allowed to stand at atmospheric pressure and room temperature for 6 hours. Thereafter, the state of the abrasive was visually observed. The symbols in Table 1 are based on the following criteria.
：: No formation of supernatant or precipitate,
×: Formation of supernatant or precipitate.
[0043]
(Example 1)
(A) Production of Organic Particles As a first step, 100 parts of water and 0.05 part of sodium lauryl sulfate were charged into a separa flask equipped with a stirrer, a thermometer, and a reflux condenser, and the temperature was raised to 70 ° C. while purging with nitrogen while stirring. did. While maintaining the internal temperature at 70 ° C., 0.8 part of potassium persulfate was added as a polymerization initiator, and after confirming that the mixture was dissolved, a mixed monomer of 4 parts of methyl methacrylate, 4 parts of butyl acrylate, and 2 parts of methacrylic acid was added. The mixture was reacted for 2 hours.
[0044]
The obtained emulsion had a solid content of about 9%, and its particle diameter was measured by an electron microscope to be about 0.05 μm.
Further, this copolymer emulsion was adjusted to pH 8.8 (at room temperature) using ammonia. At that time, the solid content concentration was 8.0%, and the average particle size was 0.5 μm.
[0045]
(B) Production of Polishing Slurry A 10% solution of oxalic acid was adjusted to pH 8.6 using ammonia. This solution, the pH-adjusted emulsion obtained in (A), pure water, and 35% hydrogen peroxide were thoroughly mixed, and the organic particles (solid content) concentration was 3.0 wt%, the hydrogen peroxide was 2.0 wt%, A polishing slurry was prepared so that oxalic acid was 1.0 wt% and pH was 8.8 (pH was adjusted using ammonia).
[0046]
As a result of the evaluation by the polishing method, it is possible to polish at a constant speed, and since there is no surface defect even if the polishing time is long, this polishing slurry is stable against a physical load during polishing. Yes, it was confirmed that scratches did not occur on the object to be polished. Table 1 shows the results.
The functional group content in the table is a value calculated from the charged amount of the monomer.
[0047]
(Example 2)
The same operation was performed as in Example 1, except that the mixed monomers used for producing the organic particles were changed to 4.8 parts of methyl methacrylate and 1.2 parts of methacrylic acid. Table 1 shows the evaluation results.
[0048]
(Example 3)
The same operation was performed as in Example 1, except that the mixed monomers used for producing the organic particles were 4.5 parts of methyl methacrylate, 5 parts of butyl acrylate, and 0.5 part of methacrylic acid. Table 1 shows the evaluation results.
[0049]
(Comparative Example 1)
The same operation as in Example 1 was performed, except that the organic fine particles of Example 1 were replaced with commercially available colloidal silica (PL-1 manufactured by Fuso Chemical Co., Ltd.), and evaluation was performed. Table 1 shows the results.
[0050]
(Comparative Example 2)
Evaluation was performed in the same manner as in Example 1 except that the mixed monomer used for the production of the organic particles was changed to 5 parts of methyl methacrylate and 5 parts of butyl acrylate. Table 1 shows the results.
[0051]
(Comparative Example 3)
In the same manner as in Example 1, except that the mixed monomer used for producing the organic particles was changed to 10 parts of methyl methacrylate and 90 parts of methacrylic acid. In this example, the polishing test could not be performed because the organic particles were dissolved in water. Table 1 shows only the storage stability.
[0052]
[Table 1]

[0053]
【The invention's effect】
By using the polishing slurry of the present invention, a chemical reaction between the organic particles and copper is promoted, and an excess copper film on the wiring-processed insulating film can be polished at a high speed. Further, the surface of the object to be polished can be polished without generating scratches and scratches due to excessive polishing, and polishing with high flatness without irregularities such as dishing and erosion can be performed.
[0054]
In addition, the polishing slurry of the present invention does not cause separation (the formation of a supernatant or a precipitate) or the formation of aggregates over time and has excellent storage stability, so that a stable polishing rate can always be obtained.
[0055]
Furthermore, since the polishing slurry of the present invention is organic fine particles whose solid content is much lower in decomposition temperature than the insulating film, heat treatment and plasma treatment do not damage the insulating film and remove the residue of the polishing slurry. Is possible. As a result, it is possible to prevent the dielectric constant of the entire insulating film layer from increasing due to the solid content in the polishing slurry remaining on the insulating film.

Claims (6)

A polishing slurry used for manufacturing a semiconductor device having copper, comprising an organic particle containing a functional group that reacts with copper in a semiconductor polishing condition at 0.1 mmol / g or more and 10 mmol / g or less; A slurry for copper polishing, comprising a complexing agent and water. The organic particles are at least one functional group selected from a carboxyl group, a hydroxyl group, a carbonyl group, an aldehyde group, an acetyl group, an amino group, a nitro group, an amide group, a cyano group, an azo group, an imino group and a glycidyl group, or neutralization thereof The slurry for copper polishing according to claim 1, comprising a resin having a substance. 3. The slurry for copper polishing according to claim 1, wherein the organic particles are an acrylic emulsion resin dispersed in an aqueous solvent. The complexing agent according to any one of claims 1 to 3, wherein the complexing agent comprises at least one compound selected from carboxylic acids, amines, amino acids, alcohols, ketones, and aldehydes. Slurry for copper polishing. The slurry for polishing copper according to any one of claims 1 to 4, wherein the oxidizing agent is hydrogen peroxide. The slurry for copper polishing according to any one of claims 1 to 5, wherein the average particle size of the organic particles is 0.01 to 5 µm.