KR101470977B1 - Slurry composition - Google Patents

Abstract

The present invention relates a slurry composition which increases a polishing rate of a nitride layer by applying the slurry composition exhibiting negative zeta potential of abrasive grains in a weak acidic or acidic region, is able to perform an automatic polishing stop function on an oxide film and is able to reduce defects since cleaning performance by ultra-pure water is excellent.

Description

Slurry composition {SLURRY COMPOSITION}

The present invention relates to a slurry composition.

The shallow trench isolation chemical mechanical polishing (STI CMP) process, which is one of the device isolation methods during the semiconductor manufacturing process, becomes more and more integrated as the devices become more diverse and highly integrated, As a process, it is emerging as a new technology that can solve the Bird's Beak phenomenon problem in LOCOS (Local Oxidation of Silicon) process. In the STI CMP process, as the minimum line width of the metal becomes increasingly strict, the width of the trench decreases and the thickness of the nitride film to be deposited becomes thinner, so that a slurry composition composition having a high polishing selectivity of the oxide film and the nitride film is required for the CMP process margin.

Conventional slurry compositions have generally been used to polish oxide films with negative zeta potentials in the weakly basic region and nitride films as polishing stop films. However, since the general CMP slurry of the CMP process as described above is generally polished 30 times faster than the nitride film, the oxide film is generally polished 30 times or more faster than the nitride film. Therefore, the dishing phenomenon is severely caused by the over- . The occurrence of such a dishing phenomenon adversely affects a subsequent photolithography or etching process, lowers the planarization property and reliability as a device isolation film, and deteriorates the electrical characteristics in the subsequent gate formation process due to the polymerization residue.

In the CMP process for a damascene gate process, which is essentially applied to a fabrication process of an ultra high density semiconductor having a design rule of the next generation of 0.05 μm or less, the design rule is reduced to 0.05 μm or less, The formation of the gate layer has become very careful. Particularly, through conventional etching and lithography processes, damage such as bridging of the metal layer occurred, and the yield was reduced. Conventional gate processes for depositing and etching polysilicon, ie, polysilicon, have recently been replaced by intaglio or damascene processes as devices become smaller and more integrated. Particularly, the speed of the device must be high, and there is a limit to increase the device speed by using the existing polysilicon. Recently, high-K materials have been found and gate formation using metal has been made. The damascene process is to form a metal layer in an engraved form at low temperature, unlike the conventional embossed metal layer formation. In this structure, there is a silver or copper gate electrode structure with an oxide between the barrier nitride film and the metal gate directly above the gate. Since silver or copper has a low melting point, it can be used in a damascene process. Thus, silver or copper is used after the high temperature activation of impurities in the source / drain regions and this process has a self-aligned relationship. Therefore, a damascene gate process, which is different from the conventional method, has begun to be used, thereby avoiding the complexity of the process and increasing the reliability of the wiring.

At this time, in the damascene process, a polishing slurry is first required to polish the nitride film and stop at the oxide film.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a slurry composition capable of enhancing a nitride film polishing rate by realizing a negative zeta potential in an acidic region and realizing an automatic polishing stop function in an oxide film .

However, the problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

The slurry composition according to the first aspect of the present invention comprises abrasive grains; An anionic polymer comprising polyacrylic acid; And an acidic substance having a pKa value of 1 to 4.

The abrasive grains may include at least one selected from the group consisting of silica, ceria, zirconia, alumina, titania, barium titania, germania, manganese, and magnesia.

The abrasive grains may be 0.1 wt% to 5 wt% of the slurry composition.

The abrasive grains may include primary particles of 5 nm to 100 nm and secondary particles of 50 nm to 300 nm.

The anionic polymer may include at least one selected from the group consisting of polyacrylic acid, polymethacrylic acid, polystyrene / acrylic acid copolymer, polyamide / acrylic acid copolymer, and polyacrylamide / acrylic acid copolymer.

The anionic polymer may be 0.05% by weight to 5% by weight of the slurry composition.

The acidic substance may be at least one selected from the group consisting of an inorganic acid, a carboxylic acid, an organic phosphonic acid, an acidic heterocyclic compound, and a salt thereof.

Wherein the carboxylic acid is selected from the group consisting of benzoic acid, phenylacetic acid, 1-naphthoic acid, 2-naphthoic acid, glycolic acid, formic acid, lactic acid, mandelic acid, oxalic acid, malonic acid, succinic acid, adipic acid, tartaric acid, At least one selected from the group consisting of aspartic acid, glutamic acid, phthalic acid, isophthalic acid, terephthalic acid, 1,2,3,4-butanetetracarboxylic acid and itaconic acid.

The acidic material may be 0.1 wt% to 1.0 wt% of the slurry composition.

The slurry composition may have a pH of 2 to 6.

And the zeta potential of the surface of the slurry composition may have a negative zeta potential.

The zeta potential of the surface of the slurry composition may be -20 mV to -100 mV.

In the slurry composition, the polishing selectivity ratio of the oxide film to the nitride film may be 2: 1 to 10: 1.

The slurry composition may be one which polishes a nitride film and has an automatic polishing stop function in the oxide film.

The slurry composition of the present invention can improve the polishing rate of the nitride film and realize the automatic polishing stop function in the oxide film by using the slurry composition in which the negative zeta potential is realized in the weakly acidic or acidic region to the abrasive grains. Further, the cleaning property by the ultra-pure water is excellent, and the occurrence of defects can be reduced.

1 is a graph showing a nitride film polishing rate profile according to an embodiment of the present invention.
2 is a graph showing an oxide film removal rate profile according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. Also, terminologies used herein are terms used to properly represent preferred embodiments of the present invention, which may vary depending on the user, intent of the operator, or custom in the field to which the present invention belongs. Therefore, the definitions of these terms should be based on the contents throughout this specification. Like reference symbols in the drawings denote like elements.

Throughout the specification, when an element is referred to as "comprising ", it means that it can include other elements as well, without excluding other elements unless specifically stated otherwise.

Hereinafter, the slurry composition of the present invention will be specifically described with reference to examples and drawings. However, the present invention is not limited to these embodiments and drawings.

The slurry composition according to the first aspect of the present invention comprises abrasive grains; An anionic polymer comprising polyacrylic acid; And an acidic substance having a pKa value of 1 to 4.

The term "acidic material with a pKa value of 1 to 4" as used in the specification and claims in connection with the compositions and methods of the present invention includes one or more acidic hydrogens with a dissociation constant in the range of 1 to 4, Lt; / RTI > Thus, materials having two or more acidic hydrogens as well as materials having one acidic hydrogen are included within the range of acidic materials of the slurry composition. Substances with two or more acidic hydrogens (e.g., sulfuric acid, phosphoric acid, succinic acid, and citric acid, etc.) have a plurality of sequential pKa values corresponding to sequential dissociation of each acidic hydrogen. For example, phosphoric acid has three acidic hydrogens and has three pKa values corresponding to dissociation of each of the first, second, and third hydrogens (i.e., 2.1, 7.2, and 12.4). For materials with multiple acidic hydrogens, one of the pKa values should range from 1 to 4. The pKa value of any other acidic hydrogen in such a compound may range from 1 to 4, or less than 1, or may exceed 4.

The abrasive grains may include at least one selected from the group consisting of silica, ceria, zirconia, alumina, titania, barium titania, germania, manganese, and magnesia.

The abrasive grains may be 0.1 wt% to 5 wt% of the slurry composition. When the abrasive grains are less than 0.1% by weight of the slurry composition, the polishing rate by the abrasive grains is decreased. When the abrasive grains are more than 5% by weight, mechanical polishing by abrasive grains is dominant, The polishing rate of the oxide film is higher than that of the nitride film, so that it has a low polishing selectivity ratio, resulting in the occurrence of dishing and erosion, and the occurrence of defects due to abrasive grains.

The abrasive grains may include primary particles of 5 nm to 100 nm and secondary particles of 50 nm to 300 nm. If the particle size of the secondary particles in the slurry composition is too small, the polishing rate for planarizing the substrate will be reduced. If the particle size is too large, planarization will be difficult and a mechanical disadvantage such as a scratched polishing surface will occur , But it is not limited thereto. When the secondary particle size of the slurry composition is less than about 50 nm in average size of the secondary particles, deterioration of cleaning property occurs when small particles are generated due to milling, and when the particle size exceeds about 300 nm, There is a fear of surface defects such as scratches.

The anionic polymer may improve the adsorption performance on the surface of the nitride film to realize an automatic polishing stop function in the oxide film. For example, the anionic polymer may include polyacrylic acid, polymethacrylic acid, polystyrene / acrylic acid copolymer, and polyacrylamide / acrylic acid copolymer And at least one selected from the group consisting of

The anionic polymer may be 0.05% by weight to 10% by weight of the abrasive grains in the slurry composition. When the anionic polymer is less than 0.05 wt% in the slurry composition, it is difficult to realize a negative zeta potential in the acidic region, the dispersion stability is lowered and the slurry quality is lowered and it is difficult to realize the automatic polishing stop function in the oxide film. If it is more than 10% by weight, there is a problem that the slurry is reacted with the slurry composition to cause agglomeration phenomenon.

The acidic substance may increase the polishing rate of the nitride film and may include at least one selected from the group consisting of an inorganic acid, a carboxylic acid, an organic phosphonic acid, an acidic heterocyclic compound, and a salt thereof .

Wherein the carboxylic acid is selected from the group consisting of benzoic acid, phenylacetic acid, 1-naphthoic acid, 2-naphthoic acid, glycolic acid, formic acid, lactic acid, mandelic acid, oxalic acid, malonic acid, succinic acid, adipic acid, tartaric acid, At least one selected from the group consisting of aspartic acid, glutamic acid, phthalic acid, isophthalic acid, terephthalic acid, 1,2,3,4-butanetetracarboxylic acid and itaconic acid.

The carboxylic acid may react with the surface of the abrasive particles to maintain the dispersion stability of the slurry composition.

The acidic material may be 0.1 wt% to 1.0 wt% of the slurry composition. When the acidic substance is less than 0.1% by weight of the slurry composition, the polishing rate may be significantly reduced. When the acidic substance is more than 1.0% by weight of the slurry composition, the dispersion stability is lowered. There is a concern.

The slurry composition may have a pH of 2 to 6. When the pH is low, the polishing rate is decreased. When the pH is high, the polishing rate is increased. However, when the pH is more than 6, the dispersion stability is rapidly lowered and coagulation occurs.

The surface of the slurry composition may have a negative zeta potential, for example, from -20 mV to -100 mV. This is because, when the zeta potential shows a value of zero or positive, the dispersion stability of the slurry is lowered to coagulate and the polishing stop function in the oxide film does not appear.

When the zeta potential in the slurry composition is higher than -20 ° C, the polishing rate of the nitride film tends to be slightly lower or the polishing rate of the oxide film tends to be slightly higher, even at a negative value. Therefore, the zeta potential of the surface of the slurry composition may be -20 ㎷ or less.

In the slurry composition, the polishing selectivity ratio of the oxide film to the nitride film may be 2: 1 to 10: 1.

The slurry composition may be one which polishes a nitride film and has an automatic polishing stop function in the oxide film.

According to a second aspect of the present invention, there is provided a method of polishing a nitride film, comprising: forming an oxide film on a substrate; Forming a nitride film on the oxide film; And polishing the nitride film using a slurry composition comprising abrasive grains, an anionic polymer including polyacrylic acid, and an acidic material having a pKa value of 1 to 4.

The step of polishing the nitride film may be a polishing stop in the oxide film during the polishing of the nitride film.

The slurry composition of the present invention can improve the polishing rate of the nitride film and realize the automatic polishing stop function in the oxide film by using the slurry composition in which the negative zeta potential is realized in the weakly acidic or acidic region to the abrasive grains. Further, the cleaning property by the ultra-pure water is excellent, and the occurrence of defects can be reduced.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

[Comparative Example 1-1]

A commercially available 150 nm ceria slurry was diluted with ultrapure water to prepare a 0.1 wt% slurry.

[Example 1-1]

2.5 wt% of polyacrylic acid as an anionic polymer was added to a commercially available 150 nm ceria slurry, pH adjusted with an acid solution having a pKa value of 1 to 4, and then diluted with ultrapure water to prepare a slurry of 0.1 wt% . The slurry was then filtered to remove aggregated particles.

[Example 2-1]

A powder with a ceria primary particle size of 25 nm prepared by the calcination process was prepared. The dispersion was prepared by adding 2.5 wt% of polyacrylic acid as an anionic polymer to the abrasive grains and adjusting the pH of the dispersion with an acid solution having a pKa value of 1 to 4. Powder was added to the prepared dispersion and pre-mixed for 30 minutes. In addition, a ball mill dispersion was performed by filling 30% of beads having a size of 0.3 mm. When the particle size reached 150 nm, ball milling was stopped and filtering was performed to remove the agglomerated particles.

[Example 2-2]

A powder with a ceria primary particle diameter of 40 nm prepared by a calcination process was prepared. The dispersion was prepared by adding 2.5 wt% of polyacrylic acid as an anionic polymer to the abrasive grains and adjusting the pH of the dispersion with an acid solution having a pKa value of 1 to 4. Powder was added to the prepared dispersion and premixed for 30 minutes. In addition, ball mill dispersion was performed by filling 30% beads of 0.3 mm size. When the particle size reached 150 nm, ball milling was discontinued and filtering was performed to remove the agglomerated particles.

[Example 2-3]

A powder with a ceria primary particle size of 60 nm prepared by the calcination process was prepared. The dispersion was prepared by adding 2.5 wt% of polyacrylic acid as an anionic polymer to the abrasive grains and adjusting the pH of the dispersion with an acid solution having a pKa value of 1 to 4. Powder was added to the prepared dispersion and premixed for 30 minutes. In addition, ball mill dispersion was performed by filling 30% beads of 0.3 mm size. When the particle size reached 150 nm, ball milling was discontinued and filtering was performed to remove the agglomerated particles.

The average size and content and pH conditions of the primary and secondary particles in the slurry compositions of the respective Examples are shown in Tables 1 and 2 below.

[Comparative Examples 1-1 to 1-2]

Other conditions were the same as those of Examples 1-1 to 1-2, except that the polishing rate of the nitride film and the oxide film was measured by varying the pH of the slurry composition as shown in Table 1 below.

[Polishing condition]

The slurry compositions of Comparative Example 1 and Example 1 were polished under the following polishing conditions.

1. Grinder: UNIPLA 231 (Doosan Mechatech)

2. Pad: IC-1010 (Rohm & Hass)

3. Polishing time: 60 s blanket wafer

4. Platen RPM: 24

5. Head RPM: 90.

6. Flow rate: 200 ml / min

7. Wafers used:

- 8 inch SiO ₂ blanket wafer (PE-TEOS)

    - 8 inch Si3N4 blanket wafer (Nitride)

8. Pressure: 4.0 psi

division Slurry properties Polishing rate Abrasive selection ratio
(Nitride film / oxide film) Primary particle Secondary particles content pH Nitride film Oxide film Comparative Example 1-1 25 nm 150 nm 0.1% 9.0 746 2826 0.3 Example 1-1 25 nm 150 nm 0.1% 2.8 156 16 9.8

division Slurry properties Polishing rate Abrasive selection ratio
(Nitride film / oxide film) Primary particle Secondary particles content pH Nitride film Oxide film Example 2-1 25 nm 150 nm 0.5% 4.5 368 75 4.9 Example 2-2 40 nm 150 nm 0.5% 4.5 431 62 6.9 Example 2-3 60 nm 150 nm 0.5% 4.5 696 128 5.4

FIG. 1 is a graph showing a nitride film polishing rate profile according to an embodiment of the present invention, and FIG. 2 is a graph showing a polishing rate profile of an oxide film according to an embodiment of the present invention.

As can be seen from Table 1, it was confirmed that the nitride film / oxide film selection ratio in Example 1-2 of the present invention was superior to that of Comparative Example 1-2 in the same conditions.

As can be seen from Table 2, FIG. 1 and FIG. 2, it was confirmed that the nitride film / oxide film selection ratio was excellent in Examples 2-1, 2-2 and 2-3 of the present invention under the same conditions.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. This is possible. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by the equivalents of the claims, as well as the claims.

Claims (14)

Abrasive particles;
An anionic polymer comprising polyacrylic acid; And
an acidic substance having a pKa value of 1 to 4;
/ RTI >
The abrasive grains are ceria abrasive grains,
Has a negative zeta potential,
Wherein the polishing layer is polished and has an automatic polishing stop function in the oxide film.
Slurry composition.
delete The method according to claim 1,
Wherein the abrasive grains are from 0.1 wt% to 5 wt% of the slurry composition.
The method according to claim 1,
Wherein the abrasive particles comprise primary particles of 5 nm to 100 nm and secondary particles of 50 nm to 300 nm.
The method according to claim 1,
Wherein the anionic polymer comprises at least one selected from the group consisting of polyacrylic acid, polymethacrylic acid, polystyrene / acrylic acid copolymer, and polyacrylamide / acrylic acid copolymer.
The method according to claim 1,
Wherein the anionic polymer is 0.05% to 5% by weight of the slurry composition.
The method according to claim 1,
Wherein the acidic substance comprises at least any one selected from the group consisting of an inorganic acid, a carboxylic acid, an organic phosphonic acid, an acidic heterocyclic compound and salts thereof.
8. The method of claim 7,
Wherein the carboxylic acid is selected from the group consisting of benzoic acid, phenylacetic acid, 1-naphthoic acid, 2-naphthoic acid, glycolic acid, formic acid, lactic acid, mandelic acid, oxalic acid, malonic acid, succinic acid, adipic acid, tartaric acid, Wherein the slurry composition contains at least any one selected from the group consisting of aspartic acid, glutamic acid, phthalic acid, isophthalic acid, terephthalic acid, 1,2,3,4-butanetetracarboxylic acid and itaconic acid.
The method according to claim 1,
Wherein the acidic material is 0.1% to 1.0% by weight of the slurry composition.
The method according to claim 1,
Wherein the slurry composition has a pH of from 2 to 6.
delete The method according to claim 1,
Wherein the zeta potential of the surface of the slurry composition is from -20 mV to -100 mV.
The method according to claim 1,
Wherein the slurry composition has a polishing selectivity ratio of the oxide film to the nitride film is from 2: 1 to 10: 1.
delete

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