Polishing composition

Abstract

To provide a polishing composition that can achieve both a high polishing rate and excellent HLM peripheral ridge resolution.SOLUTION: A polishing composition provided by the present invention is used in the pre-polishing process 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 is a compound in which at least one nitrogen atom in the nitrogen-containing organic compound A constitutes a π conjugated system structure.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a polishing composition. Specifically, it relates to a polishing composition for pre-polishing a silicon substrate. This application claims priority based on Japanese Patent Application No. 2019-18930 filed on February 5, 2019, and the entire contents of that application are incorporated herein by reference.

Background Art

[0002] Conventionally, precision polishing has been performed using a polishing composition on the surface of materials such as metals, semi-metals, non-metals, and their oxides. For example, the surface of a silicon substrate used as a component of a semiconductor product is generally finished to a high-quality mirror surface through a lapping process and a polishing process. The above polishing process typically includes a pre-polishing process (preliminary polishing process) and a final polishing process (final polishing process). The above pre-polishing process typically includes a rough polishing process (primary polishing process) and an intermediate polishing process (secondary polishing process). As a technical document related to the polishing of this type of silicon substrate, Patent Document 1 can be cited.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Incidentally, for the purpose of identification or the like, marks such as barcodes, numbers, and symbols (hard laser marks; hereinafter sometimes referred to as "HLM") may be applied to the front or back surface of the silicon substrate by irradiating the surface with laser light. The application of HLM is generally carried out after the lapping process of the silicon substrate is completed and before the polishing process is started. Usually, a modified layer is formed on the surface of the silicon substrate at the periphery of the HLM by irradiating laser light for applying the HLM. Although the HLM portion itself of the silicon substrate is not used in the final product, if the modified layer is not properly polished in the polishing process after the HLM is applied, it may become raised and the yield may decrease more than necessary. However, since the modified layer is modified into polysilicon or the like by the energy of the laser light and becomes difficult to polish, it has been difficult to effectively suppress the generation of the above-mentioned raised portion with a conventional polishing composition for a general silicon substrate.

[0005] Also, when polishing a silicon substrate provided with HLM using a polishing composition having a high polishing rate (the amount of the object to be polished removed per unit time) in expectation of improving the polishing efficiency, the easily polished portions other than the periphery of the HLM are selectively polished more than the difficult-to-polish portion at the periphery of the HLM, and as a result, it has been difficult to achieve an improvement in the resolution of the raised portion (hereinafter also simply referred to as "raised portion") at the periphery of the HLM. For this reason, there is a demand for a polishing composition having excellent performance in eliminating the raised portion at the periphery of the HLM while satisfying the practical required level regarding the polishing rate.

[0006] The present invention has been made in view of such a point, and an object thereof is to provide a polishing composition that can be used in a preliminary polishing process of a silicon substrate and can achieve both a high polishing rate and excellent resolution of the raised portion at the periphery of the HLM.

Means for Solving the Problems

[0007] According to the present invention, there is provided a polishing composition for use in a preliminary polishing step of a silicon substrate. The polishing composition includes 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 forms a π-conjugated system structure. According to the polishing composition having such a configuration, when used in the preliminary polishing step of a silicon substrate, a practically sufficiently high polishing rate and excellent elimination property of the ridge at the HLM periphery can be achieved concurrently.

[0008] In addition, in this specification, eliminating the ridge at the HLM periphery means reducing the height from the reference plane (reference flat surface) 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 the examples below.

[0009] In a preferred embodiment, the polishing composition includes at least one selected from the group consisting of an amidine derivative amine, a nitrogen-containing heterocyclic aromatic amine, a nitrogen-conjugated system carboxy group-containing compound, and urea as the nitrogen-containing organic compound A. According to the polishing composition containing such a nitrogen-containing organic compound A, the ridge at the HLM periphery can be more preferably eliminated while maintaining a practically sufficiently high polishing rate.

[0010] 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.

[0011] The polishing composition according to another preferred embodiment includes a quaternary ammonium compound as the basic compound. According to the polishing composition having such a configuration, the dispersibility of the abrasive grains in the polishing composition is improved, and the polishing rate can be improved.

[0012] 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 configuration including such a nitrogen-containing organic compound A, while maintaining a practically sufficiently high polishing rate, the protrusion at the periphery of the HLM can be suitably eliminated.

[0013] The polishing composition according to another preferred embodiment contains at least one selected from the group consisting of imidazole, pyridine, and their derivatives as the nitrogen-containing organic compound A. According to the configuration including such a nitrogen-containing organic compound A, both a high polishing rate and excellent protrusion elimination property at the periphery of the HLM can be achieved compatibly.

[0014] The polishing composition according to another preferred embodiment contains urea as the nitrogen-containing organic compound A. According to the configuration including such a nitrogen-containing organic compound A, both a high polishing rate and excellent protrusion elimination property at the periphery of the HLM can be achieved compatibly.

[0015] In another preferred embodiment of the polishing composition disclosed herein, the abrasive grains are silica particles. In polishing using silica particles as the abrasive grains, the effect of eliminating the protrusion at the periphery of the HLM by the nitrogen-containing organic compound A can be more effectively exerted.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, preferred embodiments of the present invention will be described. Matters other than those specifically mentioned in this specification and necessary for the implementation of the present invention can be grasped as design matters of those skilled in the art based on the prior art in the relevant field. The present invention can be implemented based on the content disclosed in this specification and the common general knowledge in the relevant field. In this specification, "X to Y" indicating a range means "X or more and Y or less".

[0017] In this specification, the average primary particle diameter of the abrasive grains is calculated from the specific surface area (BET value) measured by the BET method, where the average primary particle diameter (nm) = 6000 / (true density (g / cm 3 ) × BET value (m 2The particle size calculated by the formula ( / g) is referred to. For example, in the case of silica particles, the average primary particle size (nm) = 2727 / BET value (m 2 The average primary particle size can be calculated by ( / g). The measurement of the specific surface area can be carried out, for example, using a surface area measuring device manufactured by Micromeritics, trade name "Flow Sorb II 2300".

[0018] In this specification, the aspect ratio of each particle constituting the abrasive grains can be obtained by dividing the length of the long side of the smallest rectangle circumscribing the image of the particle by the scanning electron microscope (SEM) by the length of the short side of the same rectangle.

[0019] In this specification, the equivalent circle diameter of a particle refers to a value obtained by measuring the area of the image of the particle by a scanning electron microscope (SEM) and obtaining the diameter of a circle having the same area.

[0020] <Abrasive grains> The polishing composition disclosed herein contains abrasive grains. The abrasive grains function to mechanically polish the surface of the object to be polished.

[0021] The material and properties of the abrasive grains are not particularly limited and can be appropriately selected according to the purpose of use, usage mode, etc. The abrasive grains may be used alone or in combination of two or more. Examples of the 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 polymethyl methacrylate (PMMA) particles and polyacrylonitrile particles. Among them, inorganic particles are preferred.

[0022] Particularly preferred abrasive grains in the technology disclosed herein include silica particles. The technology disclosed herein can be preferably implemented, for example, in an embodiment where the abrasive grains consist substantially of silica particles. Here, "substantially" means that 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 are silica particles.

[0023] Specific examples of silica particles include colloidal silica, fumed silica, precipitated silica, etc. Silica particles can be used alone or in combination of two or more. Colloidal silica is particularly preferred because it is less likely to cause scratches on the surface of the object to be polished and can exhibit good polishing performance (such as the performance of reducing surface roughness and the ability to eliminate protrusions). As colloidal silica, for example, colloidal silica prepared from water glass (sodium silicate) as a raw material by the ion exchange method or alkoxide method colloidal silica can be preferably adopted. Here, alkoxide method colloidal silica is colloidal silica produced by the hydrolysis and condensation reaction of alkoxysilane. Colloidal silica can be used alone or in combination of two or more.

[0024] The true specific gravity of silica constituting the silica particles is preferably 1.5 or more, more preferably 1.6 or more, and even more preferably 1.7 or more. With the increase in the true specific gravity of silica, the polishing rate tends to increase. From this perspective, silica particles with a true specific gravity of 2.0 or more (for example, 2.1 or more) are particularly preferred. 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, the measured value by the liquid displacement method using ethanol as the displacement liquid can be adopted.

[0025] The average primary particle size of the abrasive grains is not particularly limited and can be appropriately selected from, for example, the range of about 10 nm to 200 nm. From the viewpoint of improving the bulge elimination property, the average primary particle size is preferably 20 nm or more, more preferably 30 nm or more. In some embodiments, the average primary particle size may be, for example, more than 40 nm, more than 45 nm, or more than 50 nm. Also, from the viewpoint of preventing the occurrence of scratches, the average primary particle size is usually advantageously 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.

[0026] The shape (outer shape) of the abrasive grains may be spherical or non-spherical. Specific examples of non-spherical particles include peanut shapes, i.e., the shape of a peanut shell, cocoon shapes, shapes with protrusions such as sugar ball shapes, and rugby ball shapes.

[0027] The average aspect ratio of the abrasive grains is not particularly limited. The average aspect ratio of the abrasive grains is, in principle, 1.0 or more, and can be 1.05 or more, or 1.1 or more. With an increase in the average aspect ratio, the bulge elimination property generally tends to improve. Also, from the viewpoints of scratch reduction and improvement of polishing stability, etc., the average aspect ratio of the abrasive grains is preferably 3.0 or less, more preferably 2.0 or less. 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.

[0028] In some embodiments, as the abrasive grains, those in which the volume ratio of particles having a circular equivalent diameter of 50 nm or more and an aspect ratio of 1.2 or more is 50% or more can be adopted. The above volume ratio can also be 60% or more. When the value of the above volume ratio is 50% or more, and further, when it is 60% or more, the bulge elimination property by the mechanical action of the abrasive grains can be further improved because relatively many particles with sizes and aspect ratios particularly effective for bulge elimination are contained in the abrasive grains.

[0029] In some embodiments, the average equivalent circular diameter of the abrasive grains may be, for example, 25 nm or more, may be 40 nm or more, may be 55 nm or more, or may be 70 nm or more. Further, the average equivalent circular diameter of the abrasive grains may be, for example, 300 nm or less, may be 200 nm or less, may be 150 nm or less, or may be 100 nm or less. The polishing composition disclosed herein can be preferably implemented using abrasive grains having such an average equivalent circular diameter.

[0030] The content of the abrasive grains is not particularly limited and can be appropriately set according to the purpose. The content of the abrasive grains relative to the total weight of the polishing composition may be, for example, 0.01% by weight or more, may be 0.05% by weight or more, or may be 0.1% by weight or more. With an increase in the content of the abrasive grains, the bulge elimination property generally tends to improve. In some embodiments, the content of the abrasive grains may be 0.2% by weight or more, may be 0.5% by weight or more, may be 0.6% by weight or more, may be 0.7% by weight or more, may be 0.8% by weight or more, or may be 0.85% by weight or more. Further, from the viewpoints of scratch prevention and reduction in the amount of abrasive grains used, in some embodiments, the content of the abrasive grains may be, for example, 10% by weight or less, may be 5% by weight or less, may be 3% by weight or less, or may be 2% by weight or less. These contents can be preferably applied, for example, to the content in the polishing liquid (working slurry) supplied to the object to be polished.

[0031] <Nitrogen-containing organic compound A> The polishing composition disclosed herein contains 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 constitutes a π-conjugated system structure (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 bulge elimination property at the HLM periphery.

[0032] 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 technology disclosed herein, as the nitrogen-containing organic compound A, those containing 1 to 10 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 to 6, still more preferably 1 to 5, for example, 1 to 4.

[0033] Here, when the number of nitrogen atoms contained in the nitrogen-containing organic compound A is 2 or more, it is not necessary for all of the nitrogen atoms contained in the nitrogen-containing organic compound A to form a π-conjugated system structure. That is, at least one of the nitrogen atoms contained in the nitrogen-containing organic compound A may form a π-conjugated system structure. In a preferred embodiment of the technology disclosed herein, the number of nitrogen atoms forming the π-conjugated system structure contained in the nitrogen-containing organic compound A is 1 to 3, and more preferably 1 to 2.

[0034] In the technology disclosed herein, the structure in which a nitrogen atom forms a 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 nitrogen conjugated system structure, a structure in which a nitrogen atom constitutes a part of an alternately positioned single bond and multiple bond (for example, a nitrogen-containing unsaturated heterocyclic structure, etc.), a structure in which a non-bonding electron pair of a nitrogen atom forms a conjugated system with an atom adjacent to the nitrogen atom, etc. can be mentioned. Specific examples of the above nitrogen conjugated system structure include an amidine structure, a nitrogen-containing unsaturated heterocyclic structure, a urea (carbamide) structure, etc. According to a polishing composition containing a nitrogen-containing organic compound A having such a structure in the molecule, the performance of eliminating the ridges at the periphery of the HLM is likely to be improved.

[0035] The nitrogen-containing organic compound A disclosed herein is not particularly limited in terms of the structure of the portion other than the nitrogen conjugation system structure as long as the nitrogen atom forms a π-conjugation system. Specific examples of the nitrogen-containing organic compound A that can be preferably used in the technology disclosed herein include amidine derivative amines, nitrogen-containing heterocyclic aromatic amines, nitrogen-conjugation system carboxyl group-containing compounds, urea, and the like. Among them, from the viewpoint of the ridgeline elimination property at the periphery of HLM, one or more selected from the group consisting of nitrogen-containing heterocyclic aromatic amines, nitrogen-conjugation system carboxyl group-containing compounds, and urea can be preferably used. Here, the above-mentioned nitrogen-conjugation system carboxyl group-containing compound refers to a compound that contains at least one carboxyl group while containing a nitrogen-conjugation system structure in the molecule.

[0036] Examples of the above-mentioned amidine derivative amine include amines having an amidine moiety (for example, heterocyclic amines having a partial structure of amidine). Specifically, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]-5-nonene (DBN), and the like can be mentioned. Among them, from the viewpoint of the ridgeline elimination property at the periphery of HLM, DBU is preferable.

[0037] The above-mentioned nitrogen-containing heterocyclic aromatic amine refers to an amine that contains at least one aromatic heterocycle containing a nitrogen atom in the molecule. Here, the size of the above-mentioned aromatic heterocycle is not particularly limited. In a preferred embodiment of the technology disclosed herein, the above-mentioned aromatic heterocycle is preferably a six-membered ring or less, more preferably a five-membered ring or a six-membered ring. The above-mentioned nitrogen-containing heterocyclic aromatic amine may have two or more unsaturated heterocycles (typically aromatic heterocycles) in the molecule. Preferably, the above-mentioned nitrogen-containing heterocyclic aromatic amine has one or two nitrogen-containing unsaturated heterocycles in the molecule.

[0038] Examples of the above nitrogen-containing heterocyclic aromatic amines include nitrogen-containing six-membered ring aromatic amines, nitrogen-containing five-membered ring aromatic amines, and the like. Preferred examples of the above nitrogen-containing six-membered ring aromatic amines include pyridine and its derivatives. Preferred examples of pyridine derivatives include 4-aminopyridine, picolinic acid, pyridine, and the like. Among them, pyridine can be preferably used. Preferred examples of the above nitrogen-containing five-membered ring aromatic amines include imidazole and its derivatives. Preferred examples of imidazole derivatives include 1-(3-aminopropyl)imidazole, 2-methylimidazole, and the like. Among them, 1-(3-aminopropyl)imidazole can be preferably used.

[0039] Non-limiting examples of the above nitrogen-conjugated carboxy group-containing compounds include guanidine derivatives such as guanidinobenzoic acid, guanidinoglutaric acid, guanidinosuccinic acid, guanidinoacetic acid, creatine, guanidinopropionic acid, imidazole derivatives such as 1-imidazoleacetic acid, picolinic acid, and the like.

[0040] Furthermore, examples of the above nitrogen-conjugated carboxy group-containing compounds include nitrogen-conjugated amino acids. The above nitrogen-conjugated amino acids refer to amino acids in which at least one nitrogen atom in the molecule constitutes a π-conjugated structure. The above nitrogen-conjugated amino acids can be preferably used from the viewpoint of eliminating the protrusion at the periphery of HLM. Specific examples of the above nitrogen-conjugated amino acids include arginine, histidine, tryptophan, and the like.

[0041] The nitrogen-containing organic compound A in the technology disclosed herein may be any one of the above-described compounds or a mixture of two or more thereof.

[0042] The content of the nitrogen-containing organic compound A in the polishing composition (when containing a plurality of types of nitrogen-containing organic compounds A, the total amount thereof) is not particularly limited and can be appropriately set according to the purpose of use, the mode of use, etc. so as to obtain a desired effect. 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 may be 0.001% by weight or more from the viewpoint of more effectively exhibiting the effect of eliminating protrusions, preferably 0.003% by weight or more, and more preferably 0.004% by weight or more. Also, 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, etc., preferably 0.05% by weight or less, more preferably 0.03% by weight or less, and still more preferably 0.02% by weight or less. These contents can be preferably applied, for example, to the content in the polishing liquid (working slurry) supplied to the object to be polished.

[0043] 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 may be 0.05 part by weight or more from the viewpoint of more effectively exhibiting the effect of eliminating protrusions, preferably 0.1 part by weight or more, more preferably 0.3 part by weight or more, and still more preferably 0.5 part by weight or more. Also, 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, etc., preferably 10 parts by weight or less, more preferably 5 parts by weight or less, and still more preferably 3 parts by weight or less (for example, 2.5 parts by weight or less).

[0044] <Basic compound> The polishing composition according to the present invention contains a basic compound. Here, the basic compound refers to a compound that has a function of increasing the pH of the composition when added to the polishing composition. The basic compound chemically polishes the surface to be polished and can contribute to an improvement in the polishing rate. In the present invention, the basic compound does not include the nitrogen-containing organic compound A in which a nitrogen atom constitutes a π-conjugated system structure.

[0045] As the above basic compound, an organic or inorganic basic compound containing nitrogen, a hydroxide of an alkali metal or an alkaline earth metal, etc. can be used. For example, as the above basic compound, a hydroxide of an alkali metal, a quaternary ammonium hydroxide or its salt, ammonia, an amine, etc. can be mentioned. Specific examples of the hydroxide of an alkali metal include potassium hydroxide, sodium hydroxide, etc. Specific examples of the quaternary ammonium hydroxide or its salt include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, etc. Specific examples of the amine include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N-(β-aminoethyl)ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, piperazine anhydride, piperazine hexahydrate, 1-(2-aminoethyl)piperazine, N-methylpiperazine, etc. When such a basic compound in which a nitrogen atom does not constitute a π-conjugated system structure is combined with the nitrogen-containing organic compound A and used, it is easy to achieve both an improvement in the polishing rate and an improvement in the ridging elimination property at the HLM periphery.

[0046] In the technology disclosed herein, the preferably used basic compound includes 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.

[0047] From the viewpoint of favorable properties such as flatness elimination and improvement, quaternary ammonium compounds are preferable as basic compounds. As quaternary ammonium compounds, quaternary ammonium salts such as tetraalkylammonium salts and hydroxyalkyltrialkylammonium salts (typically strong bases) can be preferably used. The anion component in such quaternary ammonium salts can be, for example, OH - , F - , Cl - , Br - , I - , ClO4 - , BH4 - and the like. Among them, as a preferable example, a quaternary ammonium salt in which the anion is OH - , that is, quaternary ammonium hydroxide can be mentioned. Specific examples of quaternary ammonium hydroxide include tetraalkylammonium hydroxides such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetrapentylammonium hydroxide, and tetrahexylammonium hydroxide; hydroxyalkyltrialkylammonium hydroxides such as 2-hydroxyethyltrimethylammonium hydroxide (also called choline); and the like. Particularly preferably used is tetraalkylammonium hydroxide (for example, tetramethylammonium hydroxide). The above basic compounds can be used alone or in combination of two or more.

[0048] The content of the basic compound relative 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. By increasing the content of the basic compound, the dispersion stability of the polishing composition can also be improved. It is appropriate that the content of the basic compound is 1% by weight or less, preferably 0.5% by weight or less, 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 the two or more basic compounds. These contents can be preferably applied, for example, to the content in the polishing liquid (working slurry) supplied to the object to be polished.

[0049] 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, may be 0.05 part by weight or more from the viewpoint of promoting the polishing rate, is preferably 0.1 part by weight or more, more preferably 0.3 part by weight or more, still more preferably 0.5 part by weight or more. Also, 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, may be 15 parts by weight or less from the viewpoint of surface quality and the like, is preferably 12 parts by weight or less, more preferably 10 parts by weight or less. For example, with respect to 100 parts by weight of the abrasive grains, the content of the basic compound may be 8 parts by weight or less, and can also 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 the two or more basic compounds.

[0050] <Water> In a preferred embodiment, the polishing composition disclosed herein contains water. As the water, ion-exchanged water (deionized water), pure water, ultrapure water, distilled water, etc. can be preferably used. In order to avoid inhibiting the functions of other components contained in the polishing composition as much as possible, for example, the total content of transition metal ions is preferably 100 ppb or less. For example, the purity of water can be increased by removing impurity ions with an ion-exchange resin, removing foreign substances with a filter, or operations such as distillation. The polishing composition disclosed herein may further contain an organic solvent (such as a lower alcohol or a lower ketone) that can be uniformly mixed with water, if necessary. Usually, it is preferable that 90 volume% or more of the solvent contained in the polishing composition is water, and more preferably 95 volume% or more (typically 99 - 100 volume%) is water.

[0051] <Other components> The polishing composition disclosed herein may further contain, if necessary, known additives that can be used in a polishing composition (typically, a polishing composition used in the polishing process of a silicon substrate), such as a water-soluble polymer, a surfactant, an acid, a chelating agent, a preservative, and a fungicide, as long as the effects of the present invention are not significantly impaired.

[0052] 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, pullulan, random copolymers and block copolymers of ethylene oxide and propylene oxide, polyvinyl alcohol, polyisoprene sulfonic acid, polyvinyl sulfonic acid, polyallyl sulfonic acid, polyisoamylene sulfonic acid, polystyrene sulfonate, polyacrylate, polyvinyl acetate, polyethylene glycol, polyvinyl imidazole, polyvinyl carbazole, polyvinyl pyrrolidone, polyvinyl caprolactam, polyvinyl piperidine, and the like. The water-soluble polymer can be used alone or in combination of two or more. The polishing composition disclosed herein can also be preferably implemented in an embodiment substantially free of the water-soluble polymer, that is, an embodiment in which the water-soluble polymer is not intentionally contained at least.

[0053] In the polishing composition disclosed herein, as an optional component, a surfactant (typically, a water-soluble organic compound having a molecular weight of less than 1×10 4 can be included). By using the surfactant, the dispersion stability of the polishing composition can be improved. The surfactant can be used alone or in combination of two or more. As the surfactant, an anionic or nonionic one can be preferably employed. From the viewpoints of low foaming property and ease of pH adjustment, a nonionic surfactant is more preferable. For example, oxyalkylene polymers such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; polyoxyalkylene adducts such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkylamine, polyoxyethylene fatty acid ester, polyoxyethylene glyceryl ether fatty acid ester, and polyoxyethylene sorbitan fatty acid ester; copolymers of a plurality of types of oxyalkylene (diblock type, triblock type, random type, alternating type); and the like of nonionic surfactants. The amount of the surfactant used is preferably 5 g or less, more preferably 2 g or less, and even more preferably 1 g or less per 1 kg of abrasive grains. The polishing composition disclosed herein can also be preferably implemented in an embodiment substantially free of the surfactant.

[0054] Examples of the acid include inorganic acids such as hydrochloric acid, phosphoric acid, sulfuric acid, phosphonic acid, nitric acid, phosphinic acid, and boric acid; organic acids such as acetic acid, itaconic acid, succinic acid, tartaric acid, citric acid, maleic acid, glycolic acid, malonic acid, methanesulfonic acid, formic acid, malic acid, gluconic acid, alanine, glycine, lactic acid, hydroxyethylidene diphosphonic acid (HEDP), nitrilotris[methylene phosphonic acid] (NTMP), and phosphonobutane tricarboxylic acid (PBTC); and the like. The acid may be used in the form of a salt of the acid. The salts of the above acids can be, for example, alkali metal salts such as sodium salts and potassium salts, and ammonium salts.

[0055] Examples of the chelating agent include aminocarboxylic acid-based chelating agents and organic phosphonic acid-based chelating agents. Examples of aminocarboxylic acid-based chelating agents include ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetate, nitrilotriacetic acid, sodium nitrilotriacetate, ammonium nitrilotriacetate, hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetate, diethylenetriaminepentaacetic acid, sodium diethylenetriaminepentaacetate, triethylenetetraminehexaacetic acid, and sodium triethylenetetraminehexaacetate. Examples of organic phosphonic acid-based chelating agents include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotris(methylenephosphonic acid), ethylenediaminetetrakis(methylenephosphonic acid), diethylenetriaminepentakis(methylenephosphonic acid), ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, ethane-1-hydroxy-1,1,2-triphosphonic acid, ethane-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid, and α-methylphosphonosuccinic acid. Among these, organic phosphonic acid-based chelating agents are more preferred. Particularly preferred are ethylenediaminetetrakis(methylenephosphonic acid), diethylenetriaminepentakis(methylenephosphonic acid), and diethylenetriaminepentaacetic acid. Particularly preferred chelating agents include ethylenediaminetetrakis(methylenephosphonic acid) and diethylenetriaminepentakis(methylenephosphonic acid). The chelating agent can be used alone or in combination of two or more. The amount of the chelating agent used can be set, for example, so that 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, but is not limited thereto. The polishing composition disclosed herein can also be preferably used in an embodiment without a chelating agent.

[0056] Examples of the above-mentioned preservatives and fungicides include isothiazoline compounds, paraoxybenzoic acid esters, phenoxyethanol, and the like.

[0057] The polishing composition disclosed herein preferably does not substantially contain an oxidizing agent. This is because if an oxidizing agent is contained in the polishing composition, the surface of the silicon substrate may be oxidized to form an oxide film when the composition is supplied, which may result in a decrease in the polishing rate. Here, the polishing composition not substantially containing an oxidizing agent means that the oxidizing agent is not intentionally formulated, and it is acceptable that a trace amount of oxidizing agent is inevitably contained due to raw materials, manufacturing methods, etc. 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, particularly preferably 0.000001 mol / L or less). The polishing composition according to a preferred embodiment does not contain an oxidizing agent. The polishing composition disclosed herein can be preferably implemented in a form that does not contain, for example, hydrogen peroxide, sodium persulfate, ammonium persulfate, and sodium dichloroisocyanurate.

[0058] <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 polishing composition 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 a polishing liquid as it is. That is, the concept of the polishing composition in the technology disclosed herein includes both the working slurry supplied to the object to be polished and used for polishing the object to be polished, and the concentrated liquid (stock solution) of such a working slurry. The concentration ratio of the above-mentioned concentrated liquid may be, for example, about 2 to 100 times based on volume, and usually about 5 to 50 times is appropriate.

[0059] 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 ability to eliminate protrusions tend to improve. On the other hand, from the viewpoint of preventing the dissolution of abrasive grains (e.g., silica particles) and suppressing the decrease in the mechanical polishing action by the abrasive grains, the pH of the polishing liquid is usually suitably 12.0 or lower, preferably 11.8 or lower, more preferably 11.5 or lower, and still more preferably 11.0 or lower. These pH values can be preferably applied to both the pH of the polishing liquid (working slurry) supplied to the object to be polished and its concentrated liquid.

[0060] Incidentally, the pH of the polishing composition can be determined by using a pH meter (e.g., a glass electrode type hydrogen ion concentration indicator (model number F-23) manufactured by Horiba, Ltd.), performing three-point calibration using standard buffer solutions (phthalate pH buffer solution pH: 4.01 (25 °C), neutral phosphate pH buffer solution pH: 6.86 (25 °C), carbonate pH buffer solution pH: 10.01 (25 °C)), putting the glass electrode into the polishing composition, and measuring the value after at least 2 minutes have elapsed and it has stabilized.

[0061] The polishing composition disclosed herein may be of a single-agent type or a multi-agent type including a two-agent type. For example, it may be configured such that a part A containing at least abrasive grains and a part B containing the remaining components are mixed and diluted at an appropriate timing as necessary to prepare the polishing liquid.

[0062] The manufacturing method of the polishing composition disclosed herein is not particularly limited. For example, well-known mixing devices such as a blade stirrer, an ultrasonic disperser, and a homomixer may be used to mix each component contained in the polishing composition. The mode of mixing these components is not particularly limited. For example, all components may be mixed at once, or they may be mixed in an appropriately set order.

[0063] <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. Next, 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 apparatus, and the polishing composition is supplied to the surface (polishing target surface) of the object to be polished through the polishing pad of the polishing apparatus. Typically, while continuously supplying the polishing composition, the polishing pad is pressed against the surface of the object to be polished and the two are relatively moved (for example, rotationally). Through such a polishing process, the polishing of the object to be polished is completed.

[0064] The polishing pad used in the above polishing process is not particularly limited. For example, any of a foamed polyurethane type, a non-woven fabric type, a suede type, those containing abrasive grains, those not containing abrasive grains, etc. may be used. Further, as the above polishing apparatus, a double-sided polishing apparatus for polishing both sides of the object to be polished simultaneously may be used, or a single-sided polishing apparatus for polishing only one side of the object to be polished may be used.

[0065] The above polishing composition may be used in a disposable manner (so-called "pouring and flushing") once used for polishing, or may be circulated and reused. As an example of a method of circulating and using the polishing composition, a method of collecting the used polishing composition discharged from the polishing apparatus into a tank and supplying the collected polishing composition to the polishing apparatus again can be mentioned. When the polishing composition disclosed herein is circulated and used, new components, components decreased by use, or components that it is desirable to increase may be added to the polishing composition during use at any timing. For example, as an aspect of adding components, aspects such as adding only the above nitrogen-containing organic compound A, adding only the above basic compound, or adding both of these to the polishing composition during circulation and use can be mentioned.

[0066] <Use> The polishing composition disclosed herein is excellent in the performance of eliminating the protrusions at the periphery of the HLM (protrusion elimination property). Taking advantage of such a feature, the above polishing composition can be preferably applied to the polishing of a surface to be polished including the surface provided with the HLM. The polishing composition disclosed herein can be particularly preferably used in a preliminary polishing step, that is, the first polishing step (primary polishing step) or the subsequent intermediate polishing step (secondary polishing step) in the polishing step (polishing step).

[0067] The polishing composition disclosed herein is preferably used for polishing a silicon substrate. Before the polishing step using the polishing composition disclosed herein, the silicon substrate may be subjected to general treatments applicable to the silicon substrate, such as lapping, etching, and application of the above-described HLM. The above 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 use in the application of polishing a silicon single crystal wafer provided with HLM. In addition, the polishing composition disclosed herein can also be preferably used for polishing a polishing object having no HLM.

[0068] Hereinafter, several examples of the present invention will be described, but the present invention is not intended to be limited to those shown in such examples.

[0069] <Preparation of Polishing Composition> (Example 1) The above components and ion-exchanged water were stirred and mixed at about room temperature of 25 ° C for about 30 minutes so that the content of colloidal silica (average primary particle size: 55 nm) as abrasive grains was 0.9% by weight, the content of tetramethylammonium hydroxide (TMAH) was 0.04% by weight, and the content of L-arginine as nitrogen-containing organic compound A was 0.016% by weight, thereby preparing the polishing composition according to Example 1.

[0070] (Examples 2 to 6) The polishing compositions according to Examples 2 to 6 were 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 described in Table 1.

[0071] (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.

[0072] (Examples 8 to 11) The polishing compositions according to Examples 8 to 11 were 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 were changed to those described in Table 1.

[0073] <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 polishing object (test piece) was polished under the following conditions. As the test piece, a commercially available silicon single crystal wafer with a diameter of 100 mm (thickness: 525 μm, conductivity type: P-type, crystal orientation: <100>, resistivity: 0.1 Ω·cm or more and less than 100 Ω·cm) that had been lapped and etched was used. The above wafer was attached with HLM.

[0074] (Polishing Conditions) Polishing apparatus: Single-sided polishing apparatus manufactured by Nippon Engis Co., Ltd., model "EJ-380IN" Polishing pressure: 12 kPa Platen rotation speed: 50 rpm Head rotation speed: 45 rpm Polishing pad: Manufactured by Nitta Haas Co., Ltd., trade name "SUBA800" Polishing liquid supply rate: 100 mL / min (using flooding) Holding temperature of the polishing environment: 25 °C Polishing stock removal: 4 μm

[0075] <Evaluation of Ridge Elimination Property> For the polished silicon wafer, the surface shape of the site including HLM was measured using a stylus type surface roughness and shape measuring machine (SURFCOM 1500DX, manufactured by Tokyo Seimitsu Co., Ltd.), and the height from the reference plane around HLM to the highest point of the protrusion was measured. The larger the protrusion height, the worse the evaluation result of the protrusion elimination property. The obtained results are shown in the column of "Protrusion Height" in Table 1. In addition, the protrusion height of each obtained example was converted into a relative value (relative protrusion height) with the protrusion height of Example 7 as 100%. The obtained results are shown in the column of "Relative Protrusion Height" in Table 1. <Polishing Rate Evaluation> Based on the time required for the above polishing, that is, the time required until the polishing allowance reaches 4 μm, the polishing rate [nm / min] in each example was calculated. The obtained results were converted into relative values (relative polishing rates) with the polishing rate of Example 7 as 100%. The obtained results are shown in the column of "Relative Polishing Rate" in Table 1.

[0076]

Table 1

[0077] In addition, 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)piperazine

[0078] 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, compared with the polishing composition of Example 7 not containing the nitrogen-containing organic compound A, the polishing rate was maintained at a sufficiently high level while the protrusion elimination property was significantly improved.

[0079] 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 a nitrogen-containing organic compound in which a nitrogen atom does not form a π-conjugated system structure, had deteriorated bulge elimination properties compared to the polishing compositions according to Examples 1 to 6 containing the nitrogen-containing organic compound A.

[0080] As described above, specific examples of the present invention have been described in detail, but these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

Claims

1. A polishing composition for use in a pre-polishing step of a silicon substrate, comprising: The method comprises the steps of: The polishing composition, wherein the nitrogen-containing organic compound A is a compound in which at least one nitrogen atom contained in the nitrogen-containing organic compound A forms a π-conjugated structure.

2. The polishing composition according to claim 1 , wherein the basic compound is an organic alkali.

3. The polishing composition according to claim 2 , wherein the organic alkali comprises a quaternary ammonium compound.

4. The polishing composition according to claim 1 , wherein the nitrogen-containing organic compound A is a nitrogen-conjugated carboxy group-containing compound.

5. 5. The polishing composition according to claim 4, wherein the nitrogen-containing organic compound A comprises at least one of arginine, histidine and tryptophan.

6. The polishing composition according to claim 1 , wherein the nitrogen-containing organic compound A comprises at least one selected from the group consisting of imidazole, pyridine, and derivatives thereof.

7. The polishing composition according to claim 1 , wherein the nitrogen-containing organic compound A contains urea.

8. The polishing composition according to claim 1 , wherein the abrasive grains are silica grains.

Images