KR20070075455A - Aqueous polishing slurry for polishing metal circuits comprising porous alumina - Google Patents

Abstract

Provided is a chemical mechanical polishing composition for metal circuits, which has an excellent polishing efficiency for metal circuits and hardly causes scratch and erosion. The chemical mechanical polishing composition for metal circuits comprises porous alumina as an abrasive. The porous alumina has a specific surface area of 200-350m^2/g, a pore size of 2-20nm, and a porosity of 40-65%. The porous alumina is obtained by heat-treating aluminum hydroxides at 450-1100°C. The porous alumina is contained in an amount of 0.1-30wt% based on the weight of the polishing composition. The composition has a pH ranging from 2 to 12.

Description

Aqueous polishing slurry for metal wiring containing porous alumina {AQUEOUS POLISHING SLURRY FOR POLISHING METAL CIRCUITS COMPRISING POROUS ALUMINA}

1 is a schematic diagram showing the behavior of the metal wire polishing of the conventional alumina abrasive particles and porous alumina abrasive particles according to the present invention,

2A to 2C show wafer polishing (A (10,000 times) and B (50,000 times) using conventional alumina slurry (2a), conventional silica slurry (2b), and porous alumina slurry (2c) according to the present invention, respectively. ) And after polishing (C (10,000 times magnification) and D (50,000 times magnification), the abrasive particles were observed with a high magnification scanning electron microscope (FE-SEM).

The present invention relates to a polishing composition that can be used in a chemical mechanical polishing (CMP) process of a metal film.

In general, a semiconductor manufacturing process involves polishing a wafer using a polishing slurry to realize planarization of metal wiring layers such as tungsten, aluminum and copper, and insulating films such as silicon oxide (SiO ₂ ) and silicon nitride (Si ₃ N ₄ ). A chemical mechanical polishing (CMP) process is involved.

The polishing slurry used in the polishing process includes an abrasive, water, a dispersant, and an additive, and as the additive, an oxidizing agent, a complexing agent, a corrosion inhibitor, a pH adjusting agent, and the like are used. Among them, since the abrasive is polished by mechanical friction with the polishing target, the physical properties and hardness of the abrasive particles are important depending on the polishing target.

Conventional abrasives used for polishing insulating films have mainly used metal oxides having high particle hardness such as fumed alumina, fumed silica, ceria and zirconia to effectively remove the insulating film. In this case, since the film quality is softer and softer than the insulating film, metal oxides having relatively low hardness such as alumina have been used as an abrasive.

Copper wiring, which is recently attracting attention for the integration and performance of semiconductor products, is much lower in hardness than conventional metal wiring, so it is relatively harder than alpha alumina and produced at low temperature to prevent scratches. Transitional alumina such as gamma, theta, delta, and chi or silica was used, but in this case, it was difficult to form a stable dispersion system, such as unstable crystal phase and water hydration. As a result, it was not enough to solve the problem of conventional scratches.

In addition, a method of using an abrasive-free polishing composition has been attempted to solve such a scratch problem, but it is difficult to achieve sufficient polishing due to the absence of abrasive particles, and residues remain on the wafer. Several problems have arisen.

Accordingly, it is an object of the present invention to provide a polishing composition which is excellent in polishing efficiency for metal wiring and hardly generates scratches and erosions.

In accordance with the above object, the present invention provides a chemical mechanical polishing composition for metal wiring, comprising porous alumina as an abrasive.

Hereinafter, the present invention will be described in detail.

The composition according to the present invention is characterized by using a porous alumina as an abrasive, the porous alumina can be prepared by wet milling the transition alumina obtained by heat treatment of aluminum hydroxide at 450 to 1100 ℃, preferably 500 to 900 ℃ Preferably, the transition alumina may be prepared by wet milling using beads as a grinding medium in a water dispersion medium to obtain a suspension and diluting it.

At this time, the weight ratio of transition alumina to water is in the range of 1: 0.01 to 30, and the beads are zirconia, alumina, silica-alumina, silica, titania, yttria, ferrite having a particle diameter of 0.03 to 1.2 mm, preferably 0.03 to 0.5 mm. Or mixtures thereof, and may be filled to a volume of 50 to 90% based on the volume of the wet milling apparatus. In addition, the rotational speed of the milling apparatus in the wet milling may be 1000 to 5000 rpm, preferably 2500 to 4000 rpm.

The porous alumina abrasive particles contained in the aqueous slurry of the present invention produced as a result of the preferred wet milling have a spherical or near spherical shape and have a uniform particle size within the range of 10 to 300 nm, and the pore size is 2 to 20. Nm, specific surface area in the range from 200 to 350 m 2 / g, porosity in the range from 40% to 65%.

In addition, the porous alumina abrasive according to the present invention, while maintaining the polishing rate compared to the conventional abrasive, aggregated secondary particles are easily broken even at a low pressure of 3 psi or less to reduce scratches and erosion. Figure 1 shows a schematic diagram showing the behavior of the metal wire polishing of the existing spherical alumina abrasive particles and the porous alumina abrasive particles according to the present invention.

Such porous alumina abrasive may be included in the range of 0.1 to 30% by weight, preferably 0.3 to 5% by weight relative to the weight of the polishing composition of the present invention.

In addition, the slurry composition of the present invention may include a dispersant during wet milling to prevent the porous alumina on the abrasive particles from hydration to improve particle stability and to have long-term stable dispersibility. At this time, the dispersant may be an organic acid such as citric acid, phthalic acid and malic acid; Polymers such as polyacrylic acid, polymethacrylic acid and polyethylene glycol; Examples of the compound having strong acid functional groups such as sulfonic acid group, sulfonate group, phosphonic acid group, phosphonate group and phosphate group include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid (AMPS), and vinyl sulfonic acid. And copolymers of two or more monomers selected from vinylphosphonic acid and the like; And carboxyl group-containing compounds such as acrylic acid, methacrylic acid, maleic anhydride and alkyl acrylate, alkylene oxides such as ethylene oxide and propylene oxide, styrene, vinyl alcohol, vinylpyrrolidone and vinyl acetate Conventional surfactants such as vinyl-based compounds, and copolymers obtained by condensation polymerization of at least one monomer selected from amide compounds such as formamide, dimethylformamide, acetamide, benzamide, and acrylamide, and the like. To 20% by weight.

The polishing composition according to the present invention may further comprise an additive, and such additives include oxidizing agents, complexing agents (etching agents), corrosion inhibitors, pH adjusting agents and the like.

The oxidant serves to cause the metal wiring film to be polished to be oxidized to the corresponding oxide, hydroxide or ion. The oxidizing agent that can be used in the polishing composition of the present invention is not particularly limited, but for example, hydrogen peroxide (H ₂ O ₂ ), ferric nitrate (Fe (NO ₃ ) ₃ ) or peroxo commonly used in a CMP process. Potassium acid (KIO ₃ ) and the like can be used, and may be used in the range of 0.2 to 30% by weight, preferably 1.0 to 15% by weight based on the weight of the polishing composition.

The complexing agent (etching agent) simultaneously serves to remove the metal oxide formed on the surface of the metal wiring film by the oxidant, and forms a complex with the metal oxide to prevent further oxidation. Such complexing agents are known in the art and can be used as organic acids, carboxylic acids or amino acids as proton doners, wherein amino acids are glycine and the like, and carboxylic acids are citric acid, oxalic acid, succinic acid, maleic acid, malonic acid. , Tartaric acid, phthalic acid, malic acid, glutaric acid, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, acrylic acid, lactic acid, nicotinic acid and salts thereof, and the like, and are 0.2 in weight of the polishing composition. To 5% by weight, preferably 0.3 to 3% by weight.

The corrosion inhibitor forms a passivation layer or a dissolution inhibiting layer on the surface of the metal wiring film, and serves to improve the planarization by controlling the polishing rate. These corrosion inhibitors are benzotriazole (BTA), 1,2,4-triazole, benzofuroxan, 2,1,3-benzotriazole, o-phenylenediamine, m-phenylenediamine, cate In catechol, o-aminophenol, 2-mercaptobenzotriazole, 2-mercaptobenzimidazole, 2-mercaptobenzoziazole, melanin and derivatives thereof It may be selected and may be used in the range of 0.001 to 1.0% by weight, preferably 0.001 to 0.3% by weight relative to the total weight of the polishing composition. At this time, the content of the corrosion inhibitor may be changed depending on the amount of the complexing agent.

The pH adjuster serves to adjust the pH of the polishing composition. As the pH adjusting agent, any conventional acid, base or amine compound may be used, and for example, ammonium hydroxide and amine, nitric acid, sulfuric acid, phosphoric acid, organic acid, and the like may be used. The polishing composition may be added to have a pH of 2 to 11, preferably 6 to 10.

The polishing composition of the present invention thus obtained contains less than 10,000 large particles, preferably less than 2,000, per 1 ml of the macroparticles, while the aggregated secondary particles are easily broken at low pressure to reduce scratches and residual particles. Because it provides a low effect and excellent polishing efficiency, it can be usefully used in the chemical mechanical polishing process for planarization in semiconductor manufacturing.

Hereinafter, the present invention will be described in detail by way of examples.

However, the following examples are merely to illustrate the invention, but the content of the present invention is not limited to the following examples.

Example: Polishing Slurry Preparation

Gamma alumina obtained by heat-treating aluminum hydroxide Gibbsite (Al (OH) ₃ ) powder at 500 ° C. was supplied to a wet milling apparatus UAM-015 (Ultra Apex mill, Kotobuki, Japan) together with citric acid and water for wet milling. Was repeated 20 times. At this time, the amounts of gamma alumina, citric acid and water were adjusted to have a weight ratio of 1: 0.05: 19, respectively. The chamber volume of the wet milling apparatus was 150 ml and crushing media were used to fill 0.1% of zirconia (ZrO ₂ ) beads with 80% of the chamber volume. The rotational speed of the wet milling apparatus was 3000 rpm and the feed rate of the mixture of cerium oxide and water was 200 cc / min.

0.7% by weight of porous alumina (pore size: 20 nm, specific surface area: 250 m 2 / g) relative to the total slurry weight by adding an additive and ultrapure water to the porous gamma alumina particle suspension having an average particle diameter of 130 nm obtained above. The polishing slurry was prepared to contain 0.7% by weight, 1.4% by weight of glycine and 0.7% by weight of benzotriazole (BTA).

Test Example: Comparison of Polishing Properties

In order to confirm the polishing properties of the polishing composition according to the present invention, a conventional slurry containing the polishing slurry obtained in the above example, conventional alumina (complex phase of theta and delta transition alumina) abrasive particles (manufacturer : Cabot, porosity: 55%, pore size: 22.2 nm, specific surface area: 70 m 2 / g) and conventional colloidal silica slurry (manufacturer: Fujimi, porosity: 35%, pore size: 11.2 nm, specific surface area: 44 m 2) / g) was used to perform a comparative test as follows.

Polishing was performed using the slurries on a 200 mm copper Cu blanket wafer, and a copper wafer sample was taken after the slurry treatment, before polishing and after cleaning, respectively, to remove the remaining abrasive particles on the substrate surface. Shape, size and frequency were analyzed by high magnification scanning electron microscopy (FE-SEM). The grinding machine used IPEC 472 (novellus), the rotation speed of the head and pad was 60 rpm, the down force was 2.3 psi, and the slurry feed rate was 150 cc / min.

As a result, as shown in Fig. 2, the photograph before each polishing (A (10,000 times magnification) and B (50,000 times magnification) and the after polishing (C (10,000 times magnification) and D (50,000 times magnification)) of each figure were In comparison, conventional alumina abrasive slurry (FIG. 2A) or colloidal silica slurry (FIG. 2B) does not change the size of the aggregated particles even after polishing, whereas the porous alumina slurry according to the present invention (FIG. 2C) It can be seen that the size of the abrasive grains remaining in the post Cu film is significantly smaller than the size of the abrasive grains present on the slurry before polishing. In addition, the conventional alumina slurry or silica slurry has more abrasive particles on the copper wafer surface after polishing than due to the continuous slurry supply during the polishing process, whereas the porous alumina slurry of the present invention has almost no large secondary particles. Of course, it was confirmed that the number of residual particles also decreased rather than before grinding.

Therefore, the porous alumina slurry according to the present invention can be expected to produce less scratches and erosions than the existing alumina or silica slurry, as well as hardly any residual particles.

As described above, the polishing composition comprising the porous alumina abrasive according to the present invention, the aggregated secondary particles are easily broken even at low pressure to reduce scratches and the like, the residual particles are left, and the polishing efficiency is also excellent. It can be usefully used in the chemical mechanical polishing process for planarization in semiconductor manufacturing.

Claims (14)

A chemical mechanical polishing composition for metallization, comprising porous alumina as an abrasive. The method of claim 1, Polishing composition, characterized in that the porous alumina has a specific surface area of 200 to 350 m 2 / g. The method of claim 1, Polishing composition, characterized in that the pore size of the porous alumina ranges from 2 to 20 nm. The method of claim 1, Polishing composition, characterized in that the porosity of the porous alumina ranges from 40 to 65%. The method of claim 1, Porous alumina is a polishing composition, characterized in that obtained by heat treatment of aluminum hydroxide at 450 to 1100 ℃. The method of claim 5, Polishing composition, characterized in that obtained by wet milling after heat treatment. The method of claim 6, Abrasive composition characterized by the use of beads as grinding media in milling The method of claim 7, wherein And a bead is selected from the group consisting of zirconia, alumina, silica-alumina, silica, titania, yttria, ferrite and mixtures thereof. The method of claim 8, Polishing composition, characterized in that the beads have a particle diameter of 0.03 to 1.2 mm. The method of claim 1, Polishing composition, characterized in that the porous alumina is contained in 0.1 to 30% by weight based on the weight of the polishing composition. The method of claim 1, Organic acid; Polyacrylic acid, polymethacrylic acid and polyethylene glycol; Copolymers of two or more compounds having an acid functional group selected from sulfonic acid group, sulfonate group, phosphonic acid group, phosphonate group and phosphate; And a dispersant selected from a copolymer obtained by condensation polymerization of the compound having an acid functional group with at least one selected from a carboxyl group-containing compound, an alkylene oxide, a vinyl compound, and an amide compound. Slurry. The method of claim 1, Polishing composition, characterized in that the pH ranges from 2 to 12. The method of claim 1, Polishing composition, characterized in that less than 10,000 abrasive grains having a particle size of 1 μm or more per unit volume of the composition. The method of claim 1, Polishing composition, characterized in that the metal wiring is copper wiring.

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