JPWO2020162144A1 - Polishing composition - Google Patents

Abstract

Provided is a polishing composition capable of achieving both a high polishing rate and an excellent ridge eliminating property of the HLM peripheral edge. The polishing composition provided by the present invention is used in the pre-polishing step of a silicon substrate. The polishing composition contains abrasive grains, a basic compound and a nitrogen-containing organic compound A, and the nitrogen-containing organic compound A has a π-conjugated structure in which at least one nitrogen atom contained in the nitrogen-containing organic compound A has a π-conjugated structure. It is a constituent compound.

Description

The present invention relates to a polishing composition. More specifically, the present invention relates to a polishing composition for pre-polishing a silicon substrate. This application claims priority under Japanese Patent Application No. 2019-18930 filed on February 5, 2019, the entire contents of which are incorporated herein by reference.

Conventionally, precision polishing using a polishing composition has been performed on the surface of a material such as a metal, a metalloid, a non-metal, or an oxide thereof. For example, the surface of a silicon substrate used as a component of a semiconductor product is generally finished into a high-quality mirror surface through a wrapping step and a polishing step. The polishing step typically includes a pre-polishing step (pre-polishing step) and a final polishing step (final polishing step). The pre-polishing step typically includes a rough polishing step (primary polishing step) and an intermediate polishing step (secondary polishing step). Patent Document 1 is mentioned as a technical document related to polishing of this type of silicon substrate.

Japanese Patent Application Publication No. 2015-19966

By the way, on the silicon substrate, marks such as barcodes, numbers and symbols (hard laser mark; hereinafter referred to as "HLM") are expressed by irradiating the front surface and the back surface of the silicon substrate with laser light for the purpose of identification and the like. May be attached.). The application of HLM is generally performed after the wrapping step of the silicon substrate is completed and before the polishing step is started. Usually, irradiation of a laser beam for attaching an HLM causes an altered layer on the surface of a silicon substrate on the periphery of the HLM. Although the HLM portion of the silicon substrate itself is not used in the final product, if the altered layer is not properly polished in the polishing step after HLM is applied, it may become raised and the yield may decrease more than necessary. .. However, since the altered layer is altered to polysilicon or the like by the energy of laser light and is difficult to be polished, the occurrence of the above-mentioned uplift is effectively suppressed in the conventional polishing composition for a general silicon substrate. It was difficult.

Further, when a silicon substrate to which HLM is applied is polished using a polishing composition showing a high polishing rate (amount of removing an object to be polished per unit time) in anticipation of improvement in polishing efficiency, the HLM peripheral edge is described. Other easily polished parts are selectively polished than the hard-to-polish parts of the HLM peripheral edge, and as a result, improvement in resolvability of the above-mentioned HLM peripheral edge ridge (hereinafter, also simply referred to as “ridge”) is achieved. It was sometimes difficult to do. Therefore, there is a demand for a polishing composition having excellent performance of eliminating ridges on the periphery of the HLM while satisfying a practical requirement level regarding the polishing rate.

The present invention has been made in view of these points, and is a polishing composition that can be used in a pre-polishing step of a silicon substrate and can achieve both a high polishing rate and excellent ridge elimination property of the HLM periphery. The purpose is to provide.

INDUSTRIAL APPLICABILITY According to the present invention, a polishing composition for use in a pre-polishing step of a silicon substrate is provided. The polishing composition contains abrasive grains, a basic compound and a nitrogen-containing organic compound A. Here, the nitrogen-containing organic compound A is a compound in which at least one nitrogen atom contained in the nitrogen-containing organic compound A constitutes a π-conjugated structure. According to the polishing composition having such a configuration, it can be used in the pre-polishing step of a silicon substrate, and can achieve both a practically sufficiently high polishing rate and excellent ridge elimination property of the HLM peripheral edge.

In the present specification, eliminating the ridge on the periphery of the HLM means reducing the height from the reference plane (reference plane) around the HLM of the silicon substrate to the highest point of the ridge. The height from the reference plane around the HLM of the silicon substrate to the highest point of the ridge can be measured, for example, by the method described in Examples described later.

In a preferred embodiment, the polishing composition is selected from the group consisting of an amidine derivative amine, a nitrogen-containing heterocyclic aromatic amine, a nitrogen-conjugated carboxy group-containing compound, and urea as the nitrogen-containing organic compound A. Includes one. According to the polishing composition containing the nitrogen-containing organic compound A, it is possible to more preferably eliminate the uplift of the HLM periphery while maintaining a sufficiently high polishing rate for practical use.

In a preferred embodiment, the basic compound is an organic basic compound (organic alkali). When an organic alkali is used as the basic compound, the dispersibility of the abrasive grains in the polishing composition is improved, and the polishing rate is likely to be improved.

The polishing composition according to another preferred embodiment contains a quaternary ammonium compound as the basic compound. According to the polishing composition having such a structure, the dispersibility of the abrasive grains in the polishing composition can be improved, and the polishing rate can be improved.

The polishing composition according to a preferred embodiment contains at least one of arginine, histidine and tryptophan as the nitrogen-containing organic compound A. According to the structure containing the nitrogen-containing organic compound A, the uplift of the HLM peripheral edge can be suitably eliminated while maintaining a sufficiently high polishing rate for practical use.

The polishing composition according to another preferred embodiment contains, as the nitrogen-containing organic compound A, at least one selected from the group consisting of imidazole, pyridine and derivatives thereof. According to the structure containing the nitrogen-containing organic compound A, both a high polishing rate and excellent uplift elimination property of the HLM periphery can be achieved at the same time.

The polishing composition according to another preferred embodiment contains urea as the nitrogen-containing organic compound A. According to the structure containing the nitrogen-containing organic compound A, both a high polishing rate and excellent uplift elimination property of the HLM periphery can be achieved at the same time.

In another preferred embodiment of the polishing composition disclosed herein, the abrasive grains are silica particles. In polishing using silica particles as abrasive grains, the effect of eliminating the uplift of the HLM periphery by the nitrogen-containing organic compound A can be more effectively exhibited.

Hereinafter, preferred embodiments of the present invention will be described. Matters other than those specifically mentioned in the present specification and necessary for carrying out the present invention can be grasped as design matters of those skilled in the art based on the prior art in the art. The present invention can be carried out based on the contents disclosed in the present specification and the common general technical knowledge in the art.
In the present specification, "X to Y" indicating a range means "X or more and Y or less".

In this specification, the average primary particle diameter of the abrasive grains is the average primary particle diameter (nm) = 6000 / (true density (g / cm ³ ) × BET from the specific surface area (BET value) measured by the BET method. The particle size calculated by the formula of the value (m ^{2 / g)).} For example, in the case of silica particles, the average primary particle diameter can be calculated from the ^{average primary particle diameter (nm) = 2727 / BET value (m 2 / g).} The specific surface area can be measured, for example, by using a surface area measuring device manufactured by Micromeritex, trade name "Flow Sorb II 2300".

In this specification, the aspect ratio of each particle constituting the abrasive grain is the length of the long side of the smallest rectangle circumscribing the image of the particle by a scanning electron microscope (SEM) and the length of the short side of the same rectangle. It can be obtained by dividing by.

In this specification, the circle-equivalent diameter of a particle means a value obtained by measuring the area of an image of the particle with a scanning electron microscope (SEM) and obtaining the diameter of a circle having the same area.

<Abrasion grain>
The polishing composition disclosed herein comprises abrasive grains. Abrasive grains serve to mechanically polish the surface of the object to be polished.

The material and properties of the abrasive grains are not particularly limited, and can be appropriately selected according to the purpose of use, the mode of use, and the like. As the abrasive grains, one type may be used alone, or two or more types may be used in combination. Examples of abrasive grains include inorganic particles, organic particles, and organic-inorganic composite particles. Specific examples of the inorganic particles include silicon compound particles such as silica particles, silicon nitride particles, and silicon carbide particles, and diamond particles. Specific examples of the organic particles include polymethylmethacrylate (PMMA) particles, polyacrylonitrile particles, and the like. Of these, inorganic particles are preferable.

Particularly preferable abrasive particles in the technique disclosed herein include silica particles. The technique disclosed herein may be preferably carried out, for example, in an embodiment in which the abrasive grains are substantially composed of silica particles. Here, "substantially" means 95% by weight or more (preferably 98% by weight or more, more preferably 99% by weight or more, and may be 100% by weight) of the particles constituting the abrasive grains. It means that it is a silica particle.

Specific examples of the silica particles include colloidal silica, fumed silica, precipitated silica and the like. The silica particles may be used alone or in combination of two or more. Colloidal silica is particularly preferable because it is less likely to cause scratches on the surface of the object to be polished and can exhibit good polishing performance (performance for reducing surface roughness, ridge eliminating property, etc.). As the colloidal silica, for example, colloidal silica produced from water glass (Na silicate) by an ion exchange method or alkoxide method colloidal silica can be preferably adopted. Here, the alkoxide method colloidal silica is colloidal silica produced by a hydrolysis condensation reaction of alkoxysilane. Colloidal silica can be used alone or in combination of two or more.

The true specific gravity of the silica constituting the silica particles is preferably 1.5 or more, more preferably 1.6 or more, still more preferably 1.7 or more. The polishing rate tends to increase due to the increase in the true specific gravity of silica. From this point of view, silica particles having a true specific gravity of 2.0 or more (for example, 2.1 or more) are particularly preferable. The upper limit of the true specific gravity of silica is not particularly limited, but is typically 2.3 or less, for example, 2.2 or less. As the true specific gravity of silica, a measured value by a liquid substitution method using ethanol as a substitution solution can be adopted.

The average primary particle size of the abrasive grains is not particularly limited, and can be appropriately selected from the range of, for example, about 10 nm to 200 nm. From the viewpoint of improving the ridge elimination property, the average primary particle size is preferably 20 nm or more, and more preferably 30 nm or more. In some embodiments, the average primary particle size may be, for example, greater than 40 nm, greater than 45 nm, or greater than 50 nm. Further, from the viewpoint of preventing the generation of scratches, the average primary particle size is usually preferably 150 nm or less, preferably 120 nm or less, and more preferably 100 nm or less. In some embodiments, the average primary particle size of the abrasive grains may be 75 nm or less, or 60 nm or less.

The shape (outer shape) of the abrasive grains may be spherical or non-spherical. Specific examples of the non-spherical particles include a peanut shape, that is, a peanut shell shape, a cocoon shape, a protrusiond shape such as a konpeito shape, and a rugby ball shape.

The average aspect ratio of the abrasive grains is not particularly limited. The average aspect ratio of the abrasive grains is 1.0 or more in principle, and can be 1.05 or more, or 1.1 or more. Increasing the average aspect ratio generally tends to improve the ridge elimination property. The average aspect ratio of the abrasive grains is preferably 3.0 or less, more preferably 2.0 or less, from the viewpoint of reducing scratches and improving polishing stability. In some embodiments, the average aspect ratio of the abrasive grains may be, for example, 1.5 or less, 1.4 or less, or 1.3 or less.

In some embodiments, as the abrasive grains, those having a circle-equivalent diameter of 50 nm or more and an aspect ratio of 1.2 or more and a volume ratio of particles having an aspect ratio of 1.2 or more can be adopted. The volume ratio may be 60% or more. When the value of the volume ratio is 50% or more, more specifically, when it is 60% or more, particles having a size and aspect ratio particularly effective for eliminating ridges may be contained in the abrasive grains in a relatively large amount. For this reason, it is possible to further improve the ridge eliminating property due to the mechanical action of the abrasive grains.

In some embodiments, the average circle-equivalent diameter of the abrasive grains may be, for example, 25 nm or more, 40 nm or more, 55 nm or more, or 70 nm or more. The average circle-equivalent diameter of the abrasive grains may be, for example, 300 nm or less, 200 nm or less, 150 nm or less, or 100 nm or less. The polishing composition disclosed herein can be suitably carried out using abrasive grains having such an average circle-equivalent diameter.

The content of the abrasive grains is not particularly limited and may be appropriately set according to the purpose. The content of the abrasive grains with respect to the total weight of the polishing composition may be, for example, 0.01% by weight or more, 0.05% by weight or more, or 0.1% by weight or more. Increasing the content of abrasive grains generally tends to improve the ridge eliminating property. In some embodiments, the abrasive grain content may be 0.2% by weight or more, 0.5% by weight or more, 0.6% by weight or more, 0.7% by weight or more, 0. It may be 8.8% by weight or more, and may be 0.85% by weight or more. Further, from the viewpoint of preventing scratches and saving the amount of abrasive grains used, in some embodiments, the content of the abrasive grains may be, for example, 10% by weight or less, 5% by weight or less, or 3% by weight or less. It may be 2% by weight or less. These contents can be preferably applied to the content in the polishing liquid (working slurry) supplied to the polishing object, for example.

<Nitrogen-containing organic compound A>
The polishing composition disclosed herein comprises a nitrogen-containing organic compound A. Here, the nitrogen-containing organic compound A is an organic compound containing at least one nitrogen atom in the molecule, and at least one nitrogen atom contained in the nitrogen-containing organic compound A has a π-conjugated system structure (). It is a compound that constitutes (a structure in which π electrons are delocalized). According to the polishing composition containing such a nitrogen-containing organic compound A, it is easy to achieve both a high polishing rate and excellent ridge elimination property of the HLM periphery.

The number of nitrogen atoms contained in the nitrogen-containing organic compound A may be 1 or more, and is not particularly limited. In the technique disclosed herein, as the nitrogen-containing organic compound A, a compound containing 1 or more and 10 or less nitrogen atoms in the molecule can be preferably used. The number of nitrogen atoms contained in the nitrogen-containing organic compound A is more preferably 1 or more and 6 or less, still more preferably 1 or more and 5 or less, for example, 1 or more and 4 or less.

Here, when the number of nitrogen atoms contained in the nitrogen-containing organic compound A is 2 or more, it is not necessary that all the nitrogen atoms contained in the nitrogen-containing organic compound A form a π-conjugated system structure. That is, at least one nitrogen atom among the nitrogen atoms contained in the nitrogen-containing organic compound A may form a π-conjugated system structure. In a preferred embodiment of the technique disclosed herein, the number of nitrogen atoms constituting the π-conjugated structure contained in the nitrogen-containing organic compound A is 1 or more and 3 or less, more preferably 1 or more and 2 or less. Is.

In the technique disclosed herein, the structure of the structure in which the nitrogen atom constitutes the π-conjugated system structure (hereinafter, also referred to as “nitrogen conjugated system structure”) is not particularly limited. For example, as an example of the above-mentioned nitrogen-conjugated system structure, a structure in which a nitrogen atom constitutes a part of alternating single bonds and multiple bonds (for example, a nitrogen-containing unsaturated heterocyclic structure) or a non-shared structure having a nitrogen atom. Examples thereof include a structure in which an electron pair forms a conjugated system with an atom adjacent to the nitrogen atom. Specific examples of the nitrogen conjugated system structure include an amidine structure, a nitrogen-containing unsaturated heterocyclic structure, and a urea (carbamide) structure. According to the polishing composition containing the nitrogen-containing organic compound A having such a structure in the molecule, the performance of eliminating the uplift of the HLM peripheral edge is likely to be improved.

As long as the nitrogen-containing organic compound A disclosed herein includes a structure in which a nitrogen atom constitutes a π-conjugated system, the configuration (structure, substituent, etc.) of a portion other than the nitrogen-conjugated system structure is not particularly limited. .. Specific examples of the nitrogen-containing organic compound A that can be suitably used in the technique disclosed herein include an amidine derivative amine, a nitrogen-containing heterocyclic aromatic amine, a nitrogen-conjugated carboxy group-containing compound, and urea. Among them, one or more selected from the group consisting of a nitrogen-containing heterocyclic aromatic amine, a nitrogen-conjugated carboxy group-containing compound, and urea can be preferably used from the viewpoint of eliminating the uplift of the HLM periphery. Here, the nitrogen-conjugated carboxy group-containing compound refers to a compound containing at least one carboxy group while containing a nitrogen-conjugated structure in the molecule.

Examples of the above-mentioned amidine derivative amine include an amine having an amidine moiety (for example, a heterocyclic amine having a partial structure of amidine). Specific examples thereof include 1,8-diazabicyclo [5.4.0] undec-7-en (DBU) and 1,5-diazabicyclo [4.3.0] -5-nonene (DBN). Of these, DBU is preferable from the viewpoint of eliminating uplift on the periphery of HLM.

The nitrogen-containing heterocyclic aromatic amine refers to an amine containing at least one aromatic heterocycle containing a nitrogen atom in the molecule. Here, the size of the aromatic heterocycle is not particularly limited. In a preferred embodiment of the technique disclosed herein, the aromatic heterocycle is preferably a 6-membered ring or less, more preferably a 5-membered ring or a 6-membered ring. The nitrogen-containing heterocyclic aromatic amine may have two or more unsaturated heterocycles (typically aromatic heterocycles) in the molecule. Preferably, the nitrogen-containing heterocyclic aromatic amine has one or two nitrogen-containing unsaturated heterocycles in the molecule.

Examples of the above-mentioned nitrogen-containing heterocyclic aromatic amine include nitrogen-containing 6-membered ring aromatic amine and nitrogen-containing 5-membered ring aromatic amine. Pyridine and its derivatives are preferred examples of the nitrogen-containing 6-membered ring aromatic amine. Preferable examples of the pyridine derivative include 4-aminopyridine, picolinic acid, pyridine and the like. Among them, pyridine can be preferably used. Preferable examples of the nitrogen-containing five-membered ring aromatic amine include imidazole and its derivatives. Preferable examples of the imidazole derivative include 1- (3-aminopropyl) imidazole, 2-methylimidazole and the like. Of these, 1- (3-aminopropyl) imidazole can be preferably used.

Non-limiting examples of the nitrogen-conjugated carboxy group-containing compound include guanidine derivatives such as guanidine benzoic acid, guanidinoglutaric acid, guanidine succinic acid, guanidine acetic acid, creatine, and guanidinopropionic acid, and imidazole derivatives such as 1-imidazole acetic acid. , Picolinic acid and the like.

Further, examples of the nitrogen-conjugated carboxy group-containing compound include nitrogen-conjugated amino acids. The nitrogen-conjugated amino acid refers to an amino acid in which at least one nitrogen atom in the molecule constitutes a π-conjugated structure. The nitrogen-conjugated amino acid can be preferably used from the viewpoint of eliminating uplift on the periphery of HLM. Specific examples of the nitrogen-conjugated amino acid include arginine, histidine, tryptophan and the like.

The nitrogen-containing organic compound A in the technique disclosed herein may be any one of the above-mentioned compounds, or may be a mixture of two or more.

The content of the nitrogen-containing organic compound A in the polishing composition (the total amount thereof when a plurality of types of nitrogen-containing organic compounds A are contained) is not particularly limited, and is desired according to the purpose of use, the mode of use, and the like. It can be appropriately set so that the effect of is obtained. In a preferred embodiment, the content of the nitrogen-containing organic compound A in the polishing composition can be, for example, 0.0001% by weight or more, and 0.001% by weight or more from the viewpoint of better exhibiting the uplift eliminating effect. Also, 0.003% by weight or more is preferable, and 0.004% by weight or more is more preferable. Further, the content of the nitrogen-containing organic compound A in the polishing composition can be, for example, 0.5% by weight or less, and may be 0.1% by weight or less from the viewpoint of polishing efficiency and the like, and 0.05% by weight. % Or less, more preferably 0.03% by weight or less, still more preferably 0.02% by weight or less. These contents can be preferably applied to the content in the polishing liquid (working slurry) supplied to the polishing object, for example.

Although not particularly limited, the content of the nitrogen-containing organic compound A in the polishing composition disclosed herein can be 0.01 part by weight or more with respect to 100 parts by weight of the abrasive grains, and is uplifted. From the viewpoint of better exerting the eliminating effect, the content may be 0.05 parts by weight or more, preferably 0.1 parts by weight or more, more preferably 0.3 parts by weight or more, still more preferably 0.5 parts by weight or more. be. Further, the content of the nitrogen-containing organic compound A in the polishing composition can be 20 parts by weight or less with respect to 100 parts by weight of the abrasive grains, and may be 15 parts by weight or less from the viewpoint of polishing efficiency and the like, which is preferable. Is 10 parts by weight or less, more preferably 5 parts by weight or less, still more preferably 3 parts by weight or less (for example, 2.5 parts by weight or less).

<Basic compound>
The polishing composition according to the present invention contains a basic compound. Here, the basic compound refers to a compound having a function of raising the pH of the composition by being added to the polishing composition. The basic compound functions to chemically polish the surface to be polished and can contribute to the improvement of the polishing rate. In the present invention, the basic compound does not include the nitrogen-containing organic compound A in which the nitrogen atom constitutes a π-conjugated system structure.

As the basic compound, an organic or inorganic basic compound containing nitrogen, a hydroxide of an alkali metal or an alkaline earth metal, or the like can be used. For example, examples of the basic compound include hydroxides of alkali metals, quaternary ammonium hydroxides or salts thereof, ammonia, amines and the like. Specific examples of alkali metal hydroxides include potassium hydroxide and sodium hydroxide. Specific examples of the quaternary ammonium hydroxide or a salt thereof include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide and the like. Specific examples of amines include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N- (β-aminoethyl) ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, and anhydrous piperazine. , Piperazine hexahydrate, 1- (2-aminoethyl) piperazine, N-methylpiperazine and the like. When the basic compound in which the nitrogen atom does not form a π-conjugated structure is used in combination with the nitrogen-containing organic compound A, both the improvement of the polishing rate and the improvement of the uplift elimination property of the HLM periphery are achieved at the same time. Cheap.

Examples of the basic compound preferably used in the technique disclosed herein include an organic basic compound (organic alkali). When an organic alkali is used as the basic compound, the dispersibility of the abrasive grains is improved and the polishing rate tends to be improved.

A quaternary ammonium compound can be mentioned as a preferable basic compound from the viewpoint of improving the ridge elimination property. As the quaternary ammonium compound, a quaternary ammonium salt (typically a strong base) such as a tetraalkylammonium salt or a hydroxyalkyltrialkylammonium salt can be preferably used. The anionic component in such a quaternary ammonium salt can be, for example, OH ⁻ , F ⁻ , Cl ⁻ , Br ⁻ , I ⁻ , ClO ₄ ⁻ , BH ₄ ^{− and the} like. Among them, a preferable example is a ^{quaternary ammonium salt having an anion of OH −,} that is, a quaternary ammonium hydroxide. Specific examples of the quaternary ammonium hydroxide include hydroxylation of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetrapentylammonium hydroxide and tetrahexylammonium hydroxide. Tetraalkylammonium; hydroxyalkyltrialkylammonium hydroxide such as 2-hydroxyethyltrimethylammonium (also referred to as choline); and the like. Particularly preferably used is tetraalkylammonium hydroxide (eg, tetramethylammonium hydroxide). The above basic compounds may be used alone or in combination of two or more.

The content of the basic compound with respect to the total amount of the polishing composition is preferably 0.01% by weight or more, more preferably 0.02% by weight or more, still more preferably 0.03% by weight or more from the viewpoint of promoting the polishing rate. Is. Increasing the content of the basic compound may also improve the dispersion stability of the polishing composition. The content of the basic compound is preferably 1% by weight or less, preferably 0.5% by weight or less, and more preferably 0.1% by weight or less from the viewpoint of surface quality and the like. .. When two or more basic compounds are used in combination, the above content refers to the total content of two or more basic compounds. These contents can be preferably applied to the content in the polishing liquid (working slurry) supplied to the polishing object, for example.

Although not particularly limited, the content of the basic compound in the polishing composition disclosed herein can be 0.01 part by weight or more with respect to 100 parts by weight of the abrasive grains, and the polishing rate can be adjusted. From the viewpoint of promotion, it may be 0.05 parts by weight or more, preferably 0.1 parts by weight or more, more preferably 0.3 parts by weight or more, and further preferably 0.5 parts by weight or more. Further, the content of the basic compound in the polishing composition can be 20 parts by weight or less with respect to 100 parts by weight of the abrasive grains, and may be 15 parts by weight or less from the viewpoint of surface quality and the like, preferably 15 parts by weight or less. It is 12 parts by weight or less, more preferably 10 parts by weight or less. For example, the content of the basic compound may be 8 parts by weight or less with respect to 100 parts by weight of the abrasive grains, or may be 5 parts by weight or less. When two or more basic compounds are used in combination, the above content refers to the total content of two or more basic compounds.

<Water>
In a preferred embodiment, the polishing composition disclosed herein comprises water. As the water, ion-exchanged water (deionized water), pure water, ultrapure water, distilled water and the like can be preferably used. The water used preferably has, for example, a total content of transition metal ions of 100 ppb or less in order to avoid hindering the action of other components contained in the polishing composition as much as possible. For example, the purity of water can be increased by operations such as removal of impurity ions by an ion exchange resin, removal of foreign substances by a filter, and distillation.
The polishing composition disclosed herein may further contain an organic solvent (lower alcohol, lower ketone, etc.) that can be uniformly mixed with water, if necessary. Usually, 90% by volume or more of the solvent contained in the polishing composition is preferably water, and 95% by volume or more (typically 99 to 100% by volume) is more preferably water.

<Other ingredients>
The polishing composition disclosed herein is a polishing composition containing a water-soluble polymer, a surfactant, an acid, a chelating agent, a preservative, an antifungal agent, etc., to the extent that the effects of the present invention are not significantly impaired. If necessary, a known additive that can be used (typically, a polishing composition used in a polishing step of a silicon substrate) may be further contained.

Examples of the water-soluble polymer include cellulose derivatives, starch derivatives, polymers containing oxyalkylene units, polymers containing nitrogen atoms, vinyl alcohol-based polymers, and the like. Specific examples of the water-soluble polymer include hydroxyethyl cellulose, purulan, a random copolymer of ethylene oxide and propylene oxide, a block copolymer, polyvinyl alcohol, polyvinyl alcohol, polyvinyl sulfonic acid, and polyallyl sulfonic acid. Examples thereof include polyisoamylene sulfonic acid, polystyrene sulfonate, polyacrylic acid salt, vinyl acetate, polyethylene glycol, polyvinyl imidazole, polyvinyl carbazole, polyvinyl pyrrolidone, polyvinyl caprolactam, polyvinyl piperidine and the like. The water-soluble polymer may be used alone or in combination of two or more. The polishing composition disclosed herein may be preferably carried out in an embodiment that does not substantially contain a water-soluble polymer, that is, at least intentionally does not contain a water-soluble polymer.

The polishing compositions disclosed herein, as an optional component, (typically, molecular weight 1 × 10 water-soluble organic compounds of less than ⁴⁾ a surfactant may be included. The use of a surfactant can improve the dispersion stability of the polishing composition. The surfactant may be used alone or in combination of two or more.
As the surfactant, anionic or nonionic surfactants may be preferably adopted. Nonionic surfactants are more preferable from the viewpoint of low foaming property and ease of pH adjustment. For example, oxyalkylene polymers such as polyethylene glycol, polypropylene glycol and polytetramethylene glycol; polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl amine, polyoxyethylene fatty acid ester, polyoxyethylene glyceryl ether fatty acid. Polyoxyalkylene adducts such as esters and polyoxyethylene sorbitan fatty acid esters; nonionic surfactants such as copolymers of multiple oxyalkylenes (diblock type, triblock type, random type, alternating type); Be done.
The amount of the surfactant used is preferably 5 g or less per 1 kg of abrasive grains, preferably 2 g or less, and more preferably 1 g or less. The polishing composition disclosed herein can also be preferably carried out in an embodiment that is substantially free of a surfactant.

Examples of the above acids are inorganic acids such as hydrochloric acid, phosphoric acid, sulfuric acid, phosphonic acid, nitric acid, phosphinic acid and boric acid; acetic acid, itaconic acid, succinic acid, tartrate acid, citric acid, maleic acid, glycolic acid and malonic acid. , Methanesulfonic acid, formic acid, malic acid, gluconic acid, alanine, glycine, lactic acid, hydroxyethylidene diphosphonic acid (HEDP), nitrilotris [methylene phosphonic acid] (NTMP), organic acids such as phosphonobutane tricarboxylic acid (PBTC); Be done. The acid may be used in the form of a salt of the acid. The salt of the acid may be, for example, an alkali metal salt such as a sodium salt or a potassium salt, an ammonium salt or the like.

Examples of the chelating agent include an aminocarboxylic acid-based chelating agent and an organic phosphonic acid-based chelating agent. Examples of aminocarboxylic acid-based chelating agents include ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetate, nitrilotriacetic acid, sodium nitrilotriacetate, ammonium nitrilotriacetic acid, hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetic acid, and diethylenetriaminepentaacetic acid. , Diethylenetriamine pentaacetate sodium, triethylenetetramine hexaacetic acid and triethylenetetramine hexaacetate sodium. Examples of organic phosphonic acid chelating agents include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid), ethylenediaminetetrakis (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphon). Acid), Etan-1,1-diphosphonic acid, Etan-1,1,2-triphosphonic acid, Etan-1-hydroxy-1,1-diphosphonic acid, Etan-1-hydroxy-1,1,2-triphosphonic acid , Etan-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid and α-methylphospho Contains succinic acid. Of these, organic phosphonic acid-based chelating agents are more preferable. Of these, ethylenediaminetetrakis (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid) and diethylenetriaminepentaacetic acid are preferable. Particularly preferred chelating agents include ethylenediamine tetrakis (methylenephosphonic acid) and diethylenetriaminepenta (methylenephosphonic acid). The chelating agent may be used alone or in combination of two or more. The amount of the chelating agent used is, for example, the content of the chelating agent in the working slurry is about 0.0001 to 1% by weight, about 0.001 to 0.5% by weight, or about 0.005 to 0.1% by weight. Can be set, but is not limited to this. The polishing composition disclosed herein may also be preferably used in aspects that do not contain a chelating agent.

Examples of the preservatives and fungicides include isothiazolinone compounds, paraoxybenzoic acid esters, phenoxyethanol and the like.

The polishing composition disclosed herein preferably contains substantially no oxidant. If the polishing composition contains an oxidizing agent, the supply of the composition may oxidize the surface of the silicon substrate to form an oxide film, which may reduce the polishing rate. Because. Here, the fact that the polishing composition does not substantially contain an oxidizing agent means that the oxidizing agent is not added at least intentionally, and a trace amount of the oxidizing agent is inevitably contained due to the raw material, the manufacturing method, or the like. Can be tolerated. The above-mentioned trace amount means that the molar concentration of the oxidizing agent in the polishing composition is 0.0005 mol / L or less (preferably 0.0001 mol / L or less, more preferably 0.00001 mol / L or less, and particularly preferably 0. It means that it is 0000001 mol / L or less). The polishing composition according to a preferred embodiment does not contain an oxidizing agent. The polishing composition disclosed herein may be preferably carried out in an embodiment containing, for example, hydrogen peroxide, sodium persulfate, ammonium persulfate and sodium dichloroisocyanurate.

<Polishing composition>
The polishing composition disclosed herein is typically supplied to an object to be polished in the form of a polishing liquid (working slurry) containing the composition for polishing, and is used for polishing the object to be polished. The polishing composition disclosed herein may be, for example, diluted (typically diluted with water) and used as a polishing liquid, or may be used as it is as a polishing liquid. May be good. That is, the concept of the polishing composition in the technique disclosed herein includes both a working slurry supplied to the polishing object and used for polishing the polishing object and a concentrated solution (stock solution) of the working slurry. Is included. The concentration ratio of the concentrate may be, for example, about 2 to 100 times on a volume basis, and usually about 5 to 50 times is appropriate.

The pH of the polishing composition is typically 8.0 or higher, preferably 8.5 or higher, more preferably 9.0 or higher, still more preferably 9.5 or higher, for example 10.0 or higher. As the pH increases, the polishing rate and the ridge eliminating property tend to improve. On the other hand, from the viewpoint of preventing the dissolution of abrasive grains (for example, silica particles) and suppressing the deterioration of the mechanical polishing action due to the abrasive grains, it is usually appropriate that the pH of the polishing liquid is 12.0 or less. , 11.8 or less, more preferably 11.5 or less, and even more preferably 11.0 or less. These pHs can be preferably applied to either the pH of the polishing liquid (working slurry) supplied to the object to be polished and the concentrated liquid thereof.

For the pH of the polishing composition, a pH meter (for example, a glass electrode type hydrogen ion concentration indicator (model number F-23) manufactured by Horiba Seisakusho) was used, and a standard buffer solution (phthalate pH buffer solution pH:: After three-point calibration using 4.01 (25 ° C), neutral phosphate pH buffer pH: 6.86 (25 ° C), carbonate pH buffer pH: 10.01 (25 ° C)) , The glass electrode can be grasped by putting it in the polishing composition and measuring the value after it has stabilized after 2 minutes or more.

The polishing composition disclosed herein may be a one-dosage form or a multi-dosage form including a two-dosage form. For example, the polishing liquid may be prepared by mixing at least part A containing abrasive grains and part B containing the remaining components and diluting them at an appropriate timing as needed.

The method for producing the polishing composition disclosed herein is not particularly limited. For example, each component contained in the polishing composition may be mixed using a well-known mixing device such as a blade type stirrer, an ultrasonic disperser, or a homomixer. The mode in which these components are mixed is not particularly limited, and for example, all the components may be mixed at once, or may be mixed in an appropriately set order.

<Polishing>
The polishing composition disclosed herein can be used for polishing an object to be polished, for example, in an embodiment including the following operations.
That is, a working slurry containing any of the polishing compositions disclosed herein is prepared. Then, the polishing composition is supplied to the object to be polished and polished by a conventional method. For example, the object to be polished is set in a general polishing device, and the polishing composition is supplied to the surface of the object to be polished (the surface to be polished) through the polishing pad of the polishing device. Typically, while continuously supplying the polishing composition, the polishing pad is pressed against the surface of the object to be polished to relatively move (for example, rotationally move) the two. The polishing of the object to be polished is completed through such a polishing step.

The polishing pad used in the above polishing step is not particularly limited. For example, any of foamed polyurethane type, non-woven fabric type, suede type, those containing abrasive grains, those containing no abrasive grains and the like may be used. Further, as the polishing device, a double-sided polishing device that simultaneously polishes both sides of the object to be polished may be used, or a single-sided polishing device that polishes only one side of the object to be polished may be used.

The polishing composition may be used in a form of being disposable once used for polishing (so-called “flowing”), or may be circulated and used repeatedly. As an example of the method of circulating the polishing composition, there is a method of collecting the used polishing composition discharged from the polishing device in a tank and supplying the collected polishing composition to the polishing device again. .. When the polishing composition disclosed herein is used in a circulating manner, even if a new component, a component decreased by use, or a component desired to be increased by use is added to the polishing composition in use at an arbitrary timing. good. For example, as an embodiment of adding the component, only the nitrogen-containing organic compound A is added to the polishing composition during circulation use, only the basic compound is added, or any of these is added. Can be mentioned.

<Use>
The polishing composition disclosed herein is excellent in the ability to eliminate the ridge on the periphery of the HLM (raise elimination property). Taking advantage of these features, the polishing composition can be preferably applied to polishing a surface to be polished including a surface to which HLM is attached. The polishing composition disclosed herein may be particularly preferably used in a pre-polishing step, i.e., a first polishing step (primary polishing step) in a polishing step or a subsequent intermediate polishing step (secondary polishing step).

The polishing composition disclosed herein is suitably used for polishing a silicon substrate. Prior to the polishing step using the polishing composition disclosed herein, the silicon substrate is subjected to general treatments that can be applied to the silicon substrate, such as wrapping, etching, and application of the above-mentioned HLM. It is also good.
The silicon substrate typically has a surface made of silicon. A typical example of such a silicon substrate is a silicon single crystal wafer, for example, a silicon single crystal wafer obtained by slicing a silicon single crystal ingot. The polishing composition disclosed herein is suitable for polishing a silicon single crystal wafer to which an HLM is attached.
Further, the polishing composition disclosed herein can be suitably used for polishing an object to be polished that does not have HLM.

Hereinafter, some examples of the present invention will be described, but the present invention is not intended to be limited to those shown in such examples.

<Preparation of polishing composition>
(Example 1)
The content of colloidal silica (average primary particle size: 55 nm) as abrasive grains is 0.9% by weight, the content of tetramethylammonium hydroxide (TMAH) is 0.04% by weight, and L as the nitrogen-containing organic compound A. -The polishing composition according to Example 1 was prepared by stirring and mixing each of the above components and ion-exchanged water at room temperature of about 25 ° C. for about 30 minutes so that the content of arginine was 0.016% by weight. ..

(Examples 2 to 6)
The polishing composition according to Examples 2 to 6 was prepared in the same manner as the polishing composition according to Example 1 except that the type and content of the nitrogen-containing organic compound A were changed to those shown in Table 1. did.

(Example 7)
The polishing composition according to Example 7 was prepared in the same manner as the polishing composition according to Example 1 except that the nitrogen-containing organic compound A was not used.

(Examples 8 to 11)
The polishing compositions according to Examples 8 to 11 were prepared in the same manner as the polishing compositions according to Example 1 except that the types and contents of the nitrogen-containing organic compounds were changed to those shown in Table 1. ..

<Polishing of silicon substrate>
The polishing liquid according to each example was used as it was as a working slurry, and the surface of the object to be polished (test piece) was polished under the following conditions. The test piece is a commercially available silicon single crystal wafer with a diameter of 100 mm that has been wrapped and etched (thickness: 525 μm, conduction type: P type, crystal orientation: <100>, resistivity: 0.1 Ω · cm or more, 100 Ω · cm. Less than) was used. HLM is attached to the wafer.

(Polishing conditions)
Polishing device: Single-sided polishing device manufactured by Nippon Engis Co., Ltd., model "EJ-380IN"
Polishing pressure: 12 kPa
Surface plate rotation speed: 50 rpm
Head rotation speed: 45 rpm
Polishing pad: Made by Nitta Hearth, trade name "SUBA800"
Abrasive liquid supply rate: 100 mL / min (using flowing water)
Holding temperature of polishing environment: 25 ° C
Polishing allowance: 4 μm

<Evaluation of ridge elimination>
For the polished silicon wafer, the surface shape of the site including HLM was measured using a stylus type surface roughness shape measuring machine (SURFCOM 1500DX, manufactured by Tokyo Seimitsu Co., Ltd.), and the highest uplift from the reference surface around the HLM. The height to the point was measured. The larger the height of the ridge, the worse the evaluation result is that the ridge elimination property is poor. The obtained results are shown in the "Uplift height" column of Table 1. Further, the obtained uplift height of each example was converted into a relative value (relative uplift height) with the uplift height of Example 7 as 100%. The obtained results are shown in the "Relative uplift height" column of Table 1.
<Abrasion rate evaluation>
The polishing rate [nm / min] in each example was calculated based on the time required for the above polishing, that is, the time required for the polishing allowance to reach 4 μm. The obtained result was converted into a relative value (relative polishing rate) with the polishing rate of Example 7 as 100%. The obtained results are shown in the "Relative polishing rate" column of Table 1.

The abbreviations in Table 1 mean the following compounds.
Arg: L-arginine His: L-histidine Trp: L-tryptophan APP: 1- (3-aminopropyl) imidazole Py: pyridine TEA: triethylamine AEP: N- (2-aminoethyl) piperazin

As shown in Table 1, according to the polishing compositions according to Examples 1 to 6 containing the nitrogen-containing organic compound A in which the nitrogen atom constitutes a π-conjugated system structure, the example 7 containing no nitrogen-containing organic compound A Compared with the polishing composition of No. 1, the polishing rate was maintained at a sufficiently high level, and the uplift eliminating property was significantly improved.

On the other hand, the polishing compositions of Examples 8 to 11 which do not contain the nitrogen-containing organic compound A and instead contain the nitrogen-containing organic compound in which the nitrogen atom does not form a π-conjugated system structure contain the nitrogen-containing organic compound A. Compared with the polishing composition according to Examples 1 to 6, the uplift eliminating property was deteriorated.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The techniques described in the claims include various modifications and modifications of the specific examples exemplified above.

Claims (8)

A polishing composition for use in the pre-polishing process of a silicon substrate.
Contains abrasive grains, basic compounds and nitrogen-containing organic compounds A
The nitrogen-containing organic compound A is a composition for polishing, which is a compound in which at least one nitrogen atom contained in the nitrogen-containing organic compound A constitutes a π-conjugated system structure. The polishing composition according to claim 1, wherein the basic compound is an organic alkali. The polishing composition according to claim 2, wherein the organic alkali contains a quaternary ammonium compound. The polishing composition according to any one of claims 1 to 3, wherein the nitrogen-containing organic compound A is a nitrogen-conjugated carboxy group-containing compound. The polishing composition according to claim 4, wherein the nitrogen-containing organic compound A contains at least one of arginine, histidine and tryptophan. The polishing composition according to any one of claims 1 to 3, wherein the nitrogen-containing organic compound A contains at least one selected from the group consisting of imidazole, pyridine and derivatives thereof. The polishing composition according to any one of claims 1 to 3, which contains urea as the nitrogen-containing organic compound A. The polishing composition according to any one of claims 1 to 7, wherein the abrasive grains are silica particles.