JP2015096619A - Polishing composition and polishing method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing composition capable of high-speed polishing of silicon nitride.SOLUTION: A polishing composition is used in polishing a to-be-polished object containing a material having a plus zeta potential at pH 6 or lower and contains colloidal silica of a pH of 6 or lower which is fixed with sulfonic acid and has a minus zeta potential.

Description

  The present invention relates to a polishing composition used in, for example, a semiconductor device manufacturing process and a polishing method using the same.

  In the semiconductor device manufacturing process, there is a demand for polishing silicon nitride having poor chemical reactivity at a high speed. Many of the polishing compositions conventionally used for polishing silicon nitride contain abrasive grains and acids. For example, Patent Document 1 discloses a polishing composition containing phosphoric acid or a phosphoric acid derivative. Patent Document 2 discloses a polishing composition having a pH of 2.5 to 5 containing colloidal silica and an organic acid having a sulfonic acid group or a phosphonic acid group. However, these conventional polishing compositions do not sufficiently satisfy the user's requirements regarding the polishing rate of silicon nitride.

Japanese Patent Laid-Open No. 06-124932 JP 2010-41037 A

  Therefore, an object of the present invention is to provide a polishing composition capable of polishing silicon nitride at a higher speed and a polishing method using the same.

  In order to achieve the above object, according to one embodiment of the present invention, there is provided a polishing composition used for polishing a polishing object including a material having a positive zeta potential at a pH of 6 or lower, wherein the pH is 6 Provided is a polishing composition containing colloidal silica, which is sulfonic acid fixed and has a negative zeta potential on the surface.

  The polishing object may be silicon nitride. Further, the polishing object may include polycrystalline silicon. The ratio of the polishing rate of silicon nitride to the polishing rate of polycrystalline silicon may be 2 or more. The polishing composition may have a pH of 4 or less. The polishing object may not include a metal film.

  In another aspect of the present invention, there is provided a polishing method for polishing a polishing object containing a material having a positive zeta potential at a pH of 6 or lower, using the polishing composition according to the above aspect.

  According to the present invention, a polishing composition capable of polishing silicon nitride at a high speed and a polishing method using the same are provided.

Hereinafter, an embodiment of the present invention will be described.
The polishing composition of the present embodiment is prepared by mixing colloidal silica having an organic acid immobilized thereon with water. Therefore, polishing composition contains the colloidal silica which fix | immobilized the organic acid. This polishing composition is mainly used for polishing silicon nitride, more specifically, for polishing a surface containing silicon nitride in an object to be polished such as a semiconductor wiring substrate.

  The organic acid is immobilized on the surface of the colloidal silica contained in the polishing composition by chemically bonding a functional group of the organic acid to the surface of the colloidal silica. If the colloidal silica and the organic acid are simply allowed to coexist, the organic acid is not fixed to the colloidal silica. If sulfonic acid, which is a kind of organic acid, is immobilized on colloidal silica, for example, a method described in “Sulfonic acid-functionalized silica through quantitative oxidation of thiol groups”, Chem. Commun. 246-247 (2003). It can be carried out. Specifically, a silane coupling agent having a thiol group such as 3-mercaptopropyltrimethoxysilane is coupled to colloidal silica, and then the sulfonic acid is immobilized on the surface by oxidizing the thiol group with hydrogen peroxide. The colloidal silica thus obtained can be obtained. Alternatively, if the carboxylic acid is immobilized on colloidal silica, for example, “Novel Silane Coupling Agents Containing a Photolabile 2-Nitrobenzyl Ester for Introduction of a Carboxy Group on the Surface of Silica Gel”, Chemistry Letters, 3, 228- 229 (2000). Specifically, colloidal silica having a carboxylic acid immobilized on the surface can be obtained by irradiating light after coupling a silane coupling agent containing a photoreactive 2-nitrobenzyl ester to colloidal silica. .

  The average primary particle diameter of colloidal silica in the polishing composition is preferably 5 nm or more, more preferably 7 nm or more, and further preferably 10 nm or more. As the average primary particle diameter of colloidal silica increases, there is an advantage that the polishing rate of silicon nitride by the polishing composition is improved.

  The average primary particle diameter of the colloidal silica in the polishing composition is also preferably 100 nm or less, more preferably 90 nm or less, and further preferably 80 nm or less. As the average primary particle size of the colloidal silica decreases, there is an advantage that it is possible to suppress the generation of scratches on the surface of the object to be polished after polishing with the polishing composition. In addition, the value of the average primary particle diameter of colloidal silica is computed based on the specific surface area of colloidal silica measured by BET method, for example.

  The average secondary particle diameter of colloidal silica in the polishing composition is preferably 10 nm or more, more preferably 20 nm or more, and further preferably 30 nm or more. As the average secondary particle diameter of colloidal silica increases, there is an advantage that the polishing rate of silicon nitride by the polishing composition is improved.

  The average secondary particle diameter of the colloidal silica in the polishing composition is also preferably 150 nm or less, more preferably 120 nm or less, and still more preferably 100 nm or less. As the average secondary particle diameter of colloidal silica decreases, there is an advantage that it is possible to suppress the occurrence of scratches on the surface of the object to be polished after polishing with the polishing composition. In addition, the value of the average secondary particle diameter of colloidal silica can be measured by the light-scattering method using a laser beam, for example.

The shape of the colloidal silica in the polishing composition is preferably non-spherical. The non-spherical colloidal silica may be one in which two or more primary particles are associated.
The average degree of association of colloidal silica in the polishing composition is preferably 1.2 or more, more preferably 1.5 or more. As the average degree of association of colloidal silica increases, there is an advantage that the polishing rate of silicon nitride by the polishing composition is improved.

  The average degree of association of colloidal silica in the polishing composition is also preferably 4.0 or less, more preferably 3.0 or less, and even more preferably 2.5 or less. As the average degree of association of the colloidal silica decreases, there is an advantage that it is possible to suppress the occurrence of defects or increase in surface roughness on the surface of the object to be polished after polishing with the polishing composition.

  The content of colloidal silica in the polishing composition is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and further preferably 1% by mass or more. As the colloidal silica content increases, there is an advantage that the polishing rate of silicon nitride by the polishing composition is improved.

  The content of colloidal silica in the polishing composition is also preferably 20% by mass or less, more preferably 15% by mass or less, and further preferably 10% by mass or less. As the colloidal silica content decreases, there is an advantage that the material cost of the polishing composition can be suppressed, and the aggregation of the colloidal silica can be suppressed.

  The pH value of the polishing composition needs to be 6 or less. When the pH exceeds 6, it is difficult to polish silicon nitride at a high speed using the polishing composition. From the standpoint of further improving the polishing rate of silicon nitride by the polishing composition, the pH value of the polishing composition is preferably 5 or less, more preferably 4.5 or less, and even more preferably 4 or less. .

  The pH value of the polishing composition is also preferably 1 or more, more preferably 1.5 or more, still more preferably 2 or more, and particularly preferably 2.5 or more. As the pH of the polishing composition increases, the ratio of the polishing rate of silicon nitride to the polishing rate of polycrystalline silicon by the polishing composition increases, that is, polishing silicon nitride more preferentially than polycrystalline silicon. There is an advantage that can be.

  A pH adjusting agent may be used to adjust the pH of the polishing composition to a desired value. The pH adjusting agent used may be an inorganic acid or an organic acid, or may be a chelating agent.

  Specific examples of the inorganic acid that can be used as the pH adjuster include hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, and phosphoric acid. Of these, hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid are preferred.

  Specific examples of organic acids that can be used as a pH adjuster include, for example, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid , Adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, lactic acid, diglycolic acid, 2-furancarboxylic acid, 2,5-furandicarboxylic acid, 3-furancarboxylic acid, 2-tetrahydrofuran Carboxylic acid, methoxyacetic acid, methoxyphenylacetic acid and phenoxyacetic acid. Organic sulfuric acid such as methanesulfonic acid, ethanesulfonic acid and isethionic acid may be used. Of these, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, dicarboxylic acids such as phthalic acid, malic acid and tartaric acid, and tricarboxylic acids such as citric acid are preferred.

  Instead of an inorganic acid or an organic acid, or in combination with an inorganic acid or an organic acid, a salt such as an ammonium salt or an alkali metal salt of the inorganic acid or organic acid may be used as a pH adjuster. In the case of a weak acid and a strong base, a strong acid and a weak base, or a combination of a weak acid and a weak base, a pH buffering action can be expected.

  Specific examples of chelating agents that can be used as pH adjusters include, for example, hydroxyethyliminodiacetic acid, iminodiacetic acid, acetamidoiminodiacetic acid, nitrilotripropanoic acid, nitrilotrimethylphosphonic acid, nitrilotriacetic acid, diethylenetriaminepentaacetic acid and ethylenediamine. Tetraacetic acid is mentioned.

  The polishing composition can polish silicon nitride at a high speed, while polycrystalline silicon may not be polished at a high speed. Such performance may be required when the polishing composition is used for polishing the surface of an object to be polished containing not only silicon nitride but also polycrystalline silicon. In this case, the ratio of the polishing rate of silicon nitride to the polishing rate of polycrystalline silicon is preferably 2 or more, more preferably 4 or more, still more preferably 6 or more, and particularly preferably 8 or more.

According to the present embodiment, the following advantages can be obtained.
-Polishing composition of this embodiment contains the colloidal silica which fixed organic acids, such as a sulfonic acid and carboxylic acid, and pH is 6 or less. Under pH 6 or less, the zeta potential of colloidal silica immobilized with an organic acid is negative. On the other hand, the zeta potential of silicon nitride is positive under the same pH of 6 or less. Therefore, if the polishing composition has a pH of 6 or less, the colloidal silica in the polishing composition does not electrically repel silicon nitride. Therefore, according to this polishing composition, silicon nitride can be polished at a high speed.

  When the average primary particle diameter of colloidal silica in the polishing composition is 5 nm or more, more specifically, when it is 7 nm or more or 10 nm or more, the polishing rate of silicon nitride by the polishing composition is further improved. Can do.

  When the average primary particle diameter of colloidal silica in the polishing composition is 100 nm or less, more specifically, when the average primary particle diameter is 90 nm or less or 80 nm or less, the polishing object after polishing with the polishing composition The occurrence of scratches on the surface can be satisfactorily suppressed.

  When the average secondary particle diameter of colloidal silica in the polishing composition is 10 nm or more, more specifically 20 nm or more or 30 nm or more, the polishing rate of silicon nitride by the polishing composition is further improved. be able to.

  When the average secondary particle size of colloidal silica in the polishing composition is 150 nm or less, more specifically, 120 nm or less or 100 nm or less, the polishing object after polishing with the polishing composition It is possible to satisfactorily suppress the occurrence of scratches on the surface.

  When the average degree of association of colloidal silica in the polishing composition is 1.2 or more, more specifically 1.5 or more, the polishing rate of silicon nitride by the polishing composition is further improved. Can do.

-When the shape of the colloidal silica in the polishing composition is non-spherical, the polishing rate of silicon nitride by the polishing composition can be further improved.
When the average degree of association of colloidal silica in the polishing composition is 4.0 or less, more specifically 3.0 or less or 2.5 or less, after polishing with the polishing composition It is possible to satisfactorily suppress the occurrence of defects on the surface of the polishing object and the increase in surface roughness.

  When the content of colloidal silica in the polishing composition is 0.05% by mass or more, more specifically, 0.1% by mass or more, or 1% by mass or more, silicon nitride by the polishing composition The polishing rate can be further improved.

  -When the content of colloidal silica in the polishing composition is 20% by mass or less, more specifically, when the content is 15% by mass or less or 10% by mass or less, the material cost of the polishing composition can be suppressed. In addition to this, it is possible to suppress the occurrence of colloidal silica aggregation.

  -When the pH value of the polishing composition is 5 or less, more specifically 4.5 or less or 4 or less, the polishing rate of silicon nitride by the polishing composition can be further improved.

  -When the polishing composition has a pH value of 1 or more, more specifically, 1.5 or more, 2 or more, or 2.5 or more, nitriding of the polishing composition with respect to the polishing rate of polycrystalline silicon. The ratio of the polishing rate of silicon can be increased.

  When the ratio of the polishing rate of silicon nitride to the polishing rate of polycrystalline silicon by the polishing composition is 2 or more, more specifically 4 or more, 6 or more, or 8 or more, silicon nitride and polycrystalline silicon When the polishing composition is used for polishing the surface of an object to be polished containing silicon nitride, it is possible to polish silicon nitride more preferentially than polycrystalline silicon.

The embodiment may be modified as follows.
-The polishing composition of the said embodiment may further contain another abrasive grain in addition to the colloidal silica which fix | immobilized the organic acid.

  -The polishing composition of the said embodiment may further contain water-soluble polymer. In addition to being able to adsorb on the surface of the colloidal silica or the surface of the object to be polished, the water-soluble polymer can control the polishing rate of the object to be polished by the polishing composition, and insoluble components generated during polishing Also has a function of stabilizing in the polishing composition. Examples of water-soluble polymers that can be used include compounds having a polyoxyalkylene chain, more specifically, polyethylene glycol, polypropylene glycol, polyoxyethylene alkyl ether, polyoxyethylene lauryl ether sulfate, polyoxyethylene lauryl ether. Examples include acetates, polyoxyethylene alkyl phosphates, and silicone oils having a polyoxyalkylene chain. Of these, polyethylene glycol and polypropylene glycol are preferred.

  -When the polishing composition of the said embodiment contains water-soluble polymer, it is preferable that content of the water-soluble polymer in polishing composition is 0.001 g / L or more, More preferably, it is 0.00. 005 g / L or more, more preferably 0.01 g / L or more. As the water-soluble polymer content increases, the ratio of the polishing rate of silicon nitride to the polishing rate of polycrystalline silicon by the polishing composition increases, that is, polishing silicon nitride more preferentially than polycrystalline silicon. There are advantages that can be made.

  -When the polishing composition of the said embodiment contains water-soluble polymer, it is preferable that content of the water-soluble polymer in polishing composition is 10 g / L or less, More preferably, it is 5 g / L or less. More preferably, it is 1 g / L or less. As the content of the water-soluble polymer decreases, there is an advantage that the polishing rate of polycrystalline silicon by the polishing composition is improved.

-The polishing composition of the said embodiment may further contain oxidizing agents, such as hydrogen peroxide.
-Polishing composition of the said embodiment may further contain well-known additives, such as antiseptic | preservative and a fungicide, as needed. Specific examples of the antiseptic and antifungal agent include, for example, isothiazoline preservatives such as 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one, and paraoxybenzoic acid. Examples include acid esters and phenoxyethanol.

The polishing composition of the above embodiment may be a one-component type or a multi-component type including a two-component type.
-The polishing composition of the said embodiment may be prepared by diluting the undiluted | stock solution of polishing composition 10 times or more using diluents, such as water.

-The polishing composition of the said embodiment may be used for uses other than grind | polishing silicon nitride.
Next, examples and comparative examples of the present invention will be described.

  In Examples 1 to 14 and Comparative Examples 1 to 4, colloidal silica was mixed with water, and a polishing composition was prepared by appropriately adding a pH adjuster. In Comparative Example 5, water adjusted to pH 2 using a pH adjuster was prepared as a polishing composition. Table 1 shows the details of the colloidal silica and the pH adjuster in the polishing composition of each example, and the results of measuring the pH of each polishing composition.

  In the “Colloidal silica” column of Table 1, “A” represents colloidal silica in which sulfonic acid is immobilized, and “B” represents ordinary colloidal silica in which no organic acid is immobilized. The average degree of association of the colloidal silica used in any of the examples was 2.

  Using the polishing composition of each example, the polishing rate when polishing the surfaces of a silicon nitride film blanket wafer and a polysilicon film blanket wafer with a diameter of 200 mm for 60 seconds under the polishing conditions shown in Table 2 is shown in Table 1. It is shown in the “Polishing rate” column. The value of the polishing rate is obtained by dividing the difference in wafer thickness before and after polishing measured by using the optical interference film thickness measuring device “Lambda Ace VM-2030” of Dainippon Screen Mfg. Co., Ltd. by the polishing time. It was. The values obtained by dividing the polishing rate of silicon nitride by the polishing composition of each example obtained in this way by the polishing rate of polycrystalline silicon by the same polishing composition are shown in Table 1, “Silicon polishing rate / multiple of silicon nitride”. It is shown in the column “Polishing rate of crystalline silicon”.

As shown in Table 1, when the polishing compositions of Examples 1 to 14 were used, silicon nitride could be polished at a polishing rate exceeding 30 nm / min. In contrast, in the case of the polishing compositions of Comparative Examples 1 to 3 that do not contain colloidal silica immobilized with an organic acid, and those that contain colloidal silica immobilized with sulfonic acid, the pH is higher than 6. In the case of the polishing composition of Example 4, the value obtained for the polishing rate of silicon nitride was low. Further, in the case of the polishing composition of Comparative Example 5 which did not contain colloidal silica, silicon nitride could not be polished at all.

Next, technical ideas that can be grasped from the above-described embodiments, modified examples, and examples will be described below.
In the polishing composition, the colloidal silica in which the organic acid is immobilized is obtained by fixing a sulfonic acid obtained by oxidizing a thiol group after coupling a silane coupling agent having a thiol group to the colloidal silica. Colloidal silica.

Claims (7)

A polishing composition for use in polishing a polishing object containing a material having a positive zeta potential at a pH of 6 or less,
A polishing composition comprising colloidal silica having a pH of 6 or less, immobilizing sulfonic acid, and having a negative zeta potential on the surface.   The polishing composition according to claim 1, wherein the polishing object is silicon nitride.   Furthermore, the polishing composition according to claim 2, wherein the polishing object contains polycrystalline silicon.   The polishing composition according to claim 3, wherein a ratio of a polishing rate of silicon nitride to a polishing rate of the polycrystalline silicon is 2 or more.   Polishing composition as described in any one of Claims 1-4 whose pH of the said polishing composition is 4 or less.   The polishing composition according to claim 1, wherein the polishing object does not include a metal film.   A polishing method for polishing an object to be polished containing a material having a positive zeta potential at a pH of 6 or lower using the polishing composition according to claim 1.