JP2000001667A - Abrasive for producing semiconductor device and polishing therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device producing abrasive excellent in dispersion stability and removability from abraded surface and capable of obtaining the polished surface apart from flaws, dishing and residual particles by including a diketone compound and hydrogen peroxide together with vinyl compound polymer resin particles. SOLUTION: This abrasive, in the form of an aqueous emulsion, for applying a chemically mechanical polishing to a metal surface (e.g. copper-based metal) deposited on a silicone wafer, comprises; (A) vinyl compound polymer resin particles (having an average particle size of e.g. 0.05 to 0.5 μm) resulted from emulsion polymerization, (B) a β-diketone compound e.g. acetyl acetone and (C) hydrogen peroxide. The abrasive pref. comprises 0.5 to 20 wt.% of component A, 0.01 to 20 wt.% of component B and 0.05 to 10 wt.% of component C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an abrasive for manufacturing semiconductor devices and a polishing method using the abrasive. More specifically, the present invention relates to a technique for polishing a metal film coated on a silicon wafer by chemical mechanical polishing, which does not require a step of dispersing the abrasive particles in water. Has extremely good dispersibility,
Even after long-term storage, there is no aggregation or sedimentation of the abrasive particles, the particle size of the abrasive particles can be arbitrarily controlled during emulsion polymerization, and the shape is spherical, so that stable polishing characteristics can be obtained, and the surface to be polished has no scratches. Since there is no generation and the abrasive particles are resin, they can be completely removed from the surface of the film to be polished by burning with oxygen plasma or the like after polishing, and furthermore, the surface of the polishing film free of scratches, dishing, and residual particles. Can be obtained, so that a defect in semiconductor device manufacturing such as a decrease in reliability or a decrease in product yield due to residual abrasive particles does not occur, and further, a metal film can be polished at a polishing rate sufficient for semiconductor device production. The present invention relates to an abrasive for semiconductor production and a polishing method using the abrasive.

[0002]

2. Description of the Related Art In recent years, various microfabrication techniques have been researched and developed for high integration and high performance of LSI. Among them, a chemical mechanical polishing method (Chemical Mechanical Polishing, hereinafter abbreviated as CMP) has attracted attention. CM
P is a technology in which the chemical action between the abrasive and the object to be polished is combined with the mechanical action of the abrasive particles in the abrasive. It is an indispensable technique in formation and buried metal wiring formation.

From the viewpoint of increasing the speed of LSI, Al (aluminum) and Cu (copper) having low resistance are expected to be the mainstream metal used for metal wiring in the future. And buried wiring formation are being actively studied. Generally, in the CMP of such a metal film, an abrasive slurry composed of a mixture of inorganic particles such as alumina and silica and an oxidizing agent such as ferric nitrate and hydrogen peroxide is mainly studied. However, Al and Cu
Since the metal has low hardness, polishing with inorganic particles having high hardness such as alumina or silica may damage the surface of the metal film and make the surface rough, or abrasive particles may be embedded in the wiring metal film. In a region where the width of the wiring metal film embedded in the groove or the opening is large, dishing in which the thickness of the central portion is small occurs. When dishing occurs, abrasive particles tend to remain in that part,
In particular, this tendency is remarkable in metals having low hardness such as Al and Cu. Occurrence of scratches or dishing on the surface of the wiring metal film, residual abrasive particles, and the like increase wiring resistance and cause disconnection, resulting in lower reliability and lower product yield.

In addition, inorganic slurries tend to aggregate and precipitate, and if abrasive particles having a large specific gravity or a large particle size are used, they will settle to the bottom of the container during storage. When the agglomerated slurry is used for polishing as it is, particles having a large particle diameter due to agglomeration damage the surface of the metal film, and the concentration of the slurry becomes non-uniform, causing a problem in polishing stability.

[0005] As a method of improving such a problem,
In recent years, as described in JP-A-7-86216,
There has been proposed a method of using particles mainly composed of an organic polymer compound as abrasive particles. In this method, the PMM
A. Amethacrylic resin such as A, phenolic resin, melamine resin, polystyrene resin, organic polymer compounds such as polycarbonate resin or abrasive particles such as carbon black are dispersed in water together with a dispersant and subjected to polishing, thereby polishing the metal film. It has been proposed to suppress the generation of scratches and improve the stability of polishing.

However, in the above method, a step of preparing an abrasive slurry by dispersing the abrasive particles in water together with a dispersant is necessary, and thus the dispersibility and stability of the particles in each batch vary during the preparation of the abrasive slurry. There is a problem that there is a possibility that the particle size of the abrasive particles cannot be arbitrarily controlled. It is said that the polishing rate required in a polishing step in actual semiconductor production is required to be 2,000 to 3,000 angstroms / min. However, in the polishing example of the present method, the polishing rate is described as 200 to 250 angstroms / min. Therefore, it cannot cope with the actual production of semiconductor devices.

[0007]

SUMMARY OF THE INVENTION In view of the above situation, an object of the present invention is a technique of polishing a metal film coated on a silicon wafer by chemical mechanical polishing. No need to disperse,
The dispersibility of the abrasive particles in the abrasive slurry is extremely good, there is no aggregation or sedimentation of the abrasive particles even when stored for a long time, the particle size of the abrasive particles can be arbitrarily controlled during emulsion polymerization, and the shape is spherical. Because of this, stable polishing characteristics are obtained, there is no scratch on the surface to be polished, and since the abrasive particles are resin, they can be completely removed from the surface of the film to be polished by burning with oxygen plasma or the like after polishing. It is possible to obtain a polishing film surface free of scratches, dishing, and residual particles, so that defects such as a decrease in reliability and a decrease in product yield due to the residual polishing particles do not occur in semiconductor device manufacturing. An object of the present invention is to provide a polishing slurry for semiconductor production which can be polished at a polishing rate sufficient for production of semiconductor devices, and a polishing method using the polishing slurry.

[0008]

That is, one aspect of the present invention is an abrasive for polishing a metal film coated on a silicon wafer by chemical mechanical polishing. The present invention relates to an abrasive for producing a semiconductor device, comprising an aqueous emulsion containing compound polymer resin particles and a β-diketone compound and hydrogen peroxide.

Another aspect of the present invention is a polishing method for polishing a metal film coated on a silicon wafer by chemical mechanical polishing, which relates to a polishing method using the above-mentioned abrasive as an abrasive. It is.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Examples of the vinyl compound forming a vinyl compound polymer include aromatic vinyl compounds such as styrene, vinyl toluene and α-methylstyrene; conjugated diene compounds such as butadiene and isoprene; vinyl chloride and vinylidene chloride Vinyl esters such as vinyl acetate, vinyl propionate, vinyl acetate, vinyl pivalate, vinyl laurate, and vinyl verti succinate; methyl (meth) acrylate, ethyl (meth) acrylate, (meth) ) Ester compounds of (meth) acrylic acid and alkyl alcohols having 1 to 18 carbon atoms, such as butyl acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, and stearyl (meth) acrylate; Esters, fumaric esters, Dicarboxylic acid vinyl esters such as itaconic acid esters; (meth) acrylonitrile, and the like. These vinyl compounds may be polymerized singly or may be copolymerized with one or more other vinyl compounds. Further, a functional vinyl monomer containing an amide group, a hydroxyl group, a methoxy group, a glycidyl group, etc., a monomer having an α, β-unsaturated bond,
It is also possible to use a polyfunctional monomer such as poly (meth) acrylate if necessary.

There is no particular limitation on the method of emulsion polymerization. For example, the method of adding the monomer may be polymerization by adding the entire amount of the monomer first, or may be performed by dividing addition or continuous addition. Similarly, the method of adding the initiator is not particularly limited.

As the emulsifier, water-soluble polymers, cationic, anionic, nonionic, amphoteric surfactants and the like usually used in emulsion polymerization can be used. Also, soap-free polymerization without using a surfactant may be used.

As the polymerization initiator, any compound capable of generating free radicals and ion dissociating can be used. Potassium persulfate, sodium persulfate, ammonium persulfate, 2,2-azobis (2-amidinopropane) hydrochloride or the like, or L- and D-
A redox system may be used in combination with a reducing agent such as ascorbic acid, sulfite, Rongalit, and ferrous sulfate.

The concentration of the polymerization initiator is set at 0.1 with respect to the monomer.
When the concentration of the polymerization initiator is too low, the stability of the particles deteriorates.

[0015] The polymerization temperature is usually 30 to 100 ° C, preferably 40 to 80 ° C.

The particle size and particle size distribution of the resin particles can be controlled by controlling the concentration of the initiator, the monomer composition, the method of adding the monomer, and the stirring conditions. The average particle size of the resin particles is preferably 0.05 to 0.5 μm. If the average particle size is too small, the particles may aggregate and scratches may occur on the surface to be polished, while if the average particle size is too large, scratches may occur on the surface to be polished and dishing may increase. there is a possibility. Further, the abrasive particles in the abrasive slurry tend to settle, which is not suitable for long-term storage.

In consideration of use in a semiconductor device manufacturing process, it is preferable that a raw material such as an initiator added to the polymerization system is not a metal salt.

The concentration of the resin particles in the abrasive is 0.5
-20% by weight is preferred. If the concentration is too low, a sufficient polishing rate may not be obtained in some cases. On the other hand, if the concentration is further increased, a corresponding improvement in the polishing rate may not be obtained.

In the present invention, an aqueous emulsion containing vinyl compound polymer resin particles obtained by emulsion polymerization is used. However, without using the present invention, when an ordinary abrasive mainly composed of silica or alumina is used. In addition, scratches occur on the surface to be polished during polishing, which is inconvenient.

The abrasive of the present invention contains a β-diketone compound and hydrogen peroxide.

The β-diketone compound is a compound in which two carbonyl groups contained in the molecule are bonded to the 1- and 3-position carbon atoms in the molecule. β-diketone compounds include acetylacetone, trifluoroacetylacetone,
There are propionylacetone, benzoylacetone, benzoyltrifluoroacetone, dibenzoylmethane and the like, and among them, acetylacetone is most suitable in that it is easily available industrially. The concentration of acetylacetone in the abrasive is preferably in the range of 0.01 to 20% by weight,
0.5 to 10% by weight is more preferred. If the concentration is too low, it may not be possible to obtain a sufficient polishing rate. On the other hand, if the concentration is too high, the polishing rate will increase, but acetylacetone is an organic solvent and poses a safety problem.

On the other hand, the concentration of hydrogen peroxide in the abrasive is 0.1%.
The range is preferably from 0.05 to 10% by weight, and more preferably from 0.1 to 5% by weight.
Is more preferred. When the hydrogen peroxide concentration is changed by making the acetylacetone concentration in the polishing agent the same, if the hydrogen peroxide concentration is too low, Cu is hardly polished, but if the hydrogen peroxide concentration is too high, the polishing rate conversely increases with the increase in the hydrogen peroxide concentration. Decrease. As a result of intensive studies, we have found that when acetylacetone is added to the polishing agent, the polishing rate is maximized at a hydrogen peroxide concentration of around 0.5% by weight.

The action of hydrogen peroxide in the polishing of Cu in the present invention is considered to be the same mechanism as that described in JP-A-7-233485. That is, when the concentration of hydrogen peroxide is low, Cu is ionized to generate a hydrate of Cu, and acetylacetone reacts with the hydrate to form a complex and Cu is etched. On the other hand, when the concentration of hydrogen peroxide is increased, an oxide layer of Cu is formed on the surface of the Cu film to hinder etching.

As a method for obtaining the abrasive of the present invention, an aqueous emulsion containing vinyl compound polymer resin particles may be obtained by emulsion polymerization, and acetylacetone and hydrogen peroxide may be added to the aqueous emulsion and mixed.

The polishing method of the present invention is a polishing method for polishing a metal film coated on a silicon wafer by chemical mechanical polishing, and is a polishing method using the above-mentioned polishing agent as a polishing agent. Other than using the agent, a usual method can be used.

Examples of the metal film to be polished by the abrasive of the present invention include copper-based metals. In particular, the polishing agent of the present invention has an excellent feature that it can efficiently polish a copper-based metal, which has been difficult to quickly and sufficiently polish with a conventional polishing agent. Examples of the copper-based metal include a pure copper film and a copper alloy film.

[0027]

EXAMPLES The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

<Preparation of aqueous emulsion>
Ultrapure water 3200 in a 5 liter reactor with stirrer
g, 32 g of ammonium persulfate as a polymerization initiator was added, the temperature was raised to 80 ° C., and the inside of the reactor was replaced with nitrogen gas. Thereafter, a mixed solution of 800 g of methyl methacrylate and 32 g of divinylbenzene was supplied as a monomer to the reactor at a constant rate over 4 hours to obtain a resin emulsion in which copolymer particles of methyl methacrylate / divinylbenzene were dispersed. Thereafter, 12 g of ammonium persulfate was further supplied and aged at 80 ° C. for 2 hours.

The particle concentration of the methyl methacrylate / divinylbenzene copolymer in the obtained emulsion was 21.0.
% By weight. By microscopic observation, the resin particles were spherical with an average particle diameter of 0.3 μm, and no aggregate of the resin particles was observed.

<Polishing of Copper> The above resin emulsion was used as abrasive particles, and a slurry obtained by adding acetylacetone and hydrogen peroxide to the slurry was used as a slurry. PRE
It was polished with SI company, MECAPOL E-460). The polishing conditions were as follows.
00-300 g / cm ² , polishing slurry flow rate 100 ml
/ Min, and the polishing time was 1 minute. Table 1 shows the results.

In Examples 1 to 3 and Comparative Example 1, an abrasive whose resin concentration was adjusted to 5% by weight was used.
Comparative Example 2 shows the result of polishing with an aqueous solution in which acetylacetone and hydrogen peroxide were dissolved without using a resin emulsion.

[0032]

[Table 1]

* 1 The concentration in the abrasive * 2 An aqueous solution was used instead of the aqueous emulsion

In Examples 1 to 3, polishing was carried out while changing the polishing pressure and the number of revolutions of the platen. In all cases, good results were obtained at 2000 ° / min or more. As shown in Comparative Example 1, the slurry obtained by adding only acetylacetone to the resin emulsion was hardly polished. Further, as shown in Comparative Example 2, when polishing was performed only with an aqueous solution in which acetylacetone and hydrogen peroxide were dissolved without using a resin emulsion, the Cu film was polished but at a low level.

[0035]

As described above, according to the present invention, a technique for polishing a metal film coated on a silicon wafer by chemical mechanical polishing, which does not require a step of dispersing abrasive particles in water, The dispersibility of the abrasive particles in the slurry is extremely good, there is no aggregation or sedimentation of the abrasive particles even after long-term storage, and the particle size of the abrasive particles can be arbitrarily controlled during emulsion polymerization, and the shape is spherical. Stable polishing characteristics are obtained, there is no scratch on the surface to be polished, and the polishing particles are resin. Therefore, by burning with oxygen plasma or the like after polishing, it can be completely removed from the surface of the film to be polished. In addition, since a polishing film surface free from scratches, dishing, and residual particles can be obtained, defects in semiconductor device manufacturing such as a reduction in reliability and a decrease in product yield due to residual polishing particles may occur. Without further was able to provide a polishing method using a polishing agent for a semiconductor manufacturing that can be polished at a sufficiently can respond polishing rate in the production of semiconductor devices, and the abrasive.

Claims (8)

[Claims] An abrasive for polishing a metal film coated on a silicon wafer by chemical mechanical polishing, comprising:
An abrasive for manufacturing a semiconductor device, comprising an aqueous emulsion containing vinyl compound polymer resin particles obtained by emulsion polymerization and containing a β-diketone compound and hydrogen peroxide. 2. The abrasive according to claim 1, wherein the average particle diameter of the vinyl compound polymer resin particles is 0.05 to 0.5 μm. 3. The method according to claim 1, wherein the concentration of the resin particles in the abrasive is 0.5-2.
The abrasive according to claim 1, which is 0% by weight. 4. The polishing agent according to claim 1, wherein the β-diketone compound is acetylacetone. 5. The abrasive according to claim 1, wherein the concentration of the β-diketone compound in the abrasive is 0.01 to 20% by weight. 6. The hydrogen peroxide concentration in the abrasive is 0.05.
The abrasive according to claim 1, wherein the amount is 10 to 10% by weight. 7. The polishing agent according to claim 1, wherein the metal film coated on the silicon wafer is a metal film of a copper-based metal. 8. A polishing method for polishing a metal film coated on a silicon wafer by chemical mechanical polishing, wherein the polishing agent according to claim 1 is used as the polishing agent.