JP2020027834A - Composition for silicon wafer polishing - Google Patents

Abstract

To provide composition for polishing, capable of preferably reducing haze in the polishing of a silicon wafer.SOLUTION: In the formula, a composition for a silicon wafer polishing to be disclosed here, contains an abrasive grain, water, a water-soluble polymer compound, and a nitrogen-containing basic compound expressed by the following general formula (1). In the general formula, R, R, and Rare one of a group selected independently from an alkyl group of 1 to 15 of carbons and a hydroxyalkyl group of 1 to 15 of carbons, or two from R, R, and Rare the group that are coupled each other, and form a ring structure containing a nitrogen atom and a carbon atom coupled by them, and the residual one of them is the group selected from the alkyl group of 1 to 15 of carbons and the hydroxyalkyl group of 1 to 15 of carbons.SELECTED DRAWING: None

Description

  The present invention relates to a composition for polishing a silicon wafer.

  The surface of a silicon wafer used as a component of a semiconductor device or the like is generally finished to a high-quality mirror surface through a lapping step (rough polishing step) and a polishing step (precision polishing step). The polishing step typically includes a preliminary polishing step (preliminary polishing step) and a final polishing step (final polishing step). As a polishing method in the polishing step, a chemical mechanical polishing method in which a water-soluble polymer (a water-soluble polymer compound) represented by a cellulose derivative or the like is contained in a polishing liquid is known. In this method, the water-soluble polymer adsorbs or desorbs on the abrasive grains or the silicon wafer, thereby contributing to the reduction of defects and haze on the polished surface. As a technical document relating to a polishing composition for a silicon wafer, for example, Patent Document 1 is cited. Patent Document 1 discloses a polishing composition containing water, a water-soluble polymer compound, colloidal silica (abrasive grains), and an alkali compound (such as ammonia).

JP 2012-89662 A

  Patent Document 1 proposes to use a water-soluble polymer compound having a predetermined viscosity in order to improve the wettability of the surface of a semiconductor substrate and reduce minute defects such as adhesion of particles. However, in recent years, the demand for the surface quality of a polished silicon wafer has been further increased, and there has been a demand for a polishing composition that can more suitably reduce haze and contribute to further improving the quality of a silicon wafer.

  The present invention has been made in view of the above circumstances, and has as its object to provide a polishing composition capable of suitably reducing haze in polishing a silicon wafer.

  The present inventors conducted various experiments and studies in order to solve the above-mentioned problems, and as a result, by using a specific nitrogen-containing basic compound for pH adjustment of the polishing composition, an excellent haze reduction effect was obtained. The inventors have found that the present invention can be exerted, and have completed the present invention.

（式中、Ｒ^１，Ｒ^２，Ｒ^３は、それぞれ独立に、炭素数１〜１５のアルキル基および炭素数１〜１５のヒドロキシアルキル基からなる群から選択される基であるか、または、Ｒ^１、Ｒ^２、Ｒ^３のうち２つは互いに結合し、それらが結合している窒素原子および炭素原子を含む環構造を形成し、残りの一つは炭素数１〜１５のアルキル基および炭素数１〜１５のヒドロキシアルキル基からなる群から選択される基である。）；で表される。上記一般式（１）で表される含窒素塩基性化合物を含む構成の研磨用組成物によると、シリコンウェーハの研磨におけるヘイズを好適に低減することができる。 That is, according to the present specification, there is provided a silicon wafer polishing composition including abrasive grains, water, a water-soluble polymer compound, and a nitrogen-containing basic compound. The nitrogen-containing basic compound has the following general formula (1):

(Wherein, R ¹ , R ² , and R ³ are each independently a group selected from the group consisting of an alkyl group having 1 to 15 carbon atoms and a hydroxyalkyl group having 1 to 15 carbon atoms, or ^{Two of} R ¹ , R ² and R ³ are bonded to each other to form a ring structure containing a nitrogen atom and a carbon atom to which they are bonded, and the other one is an alkyl group having 1 to 15 carbon atoms and And a group selected from the group consisting of hydroxyalkyl groups having 1 to 15 carbon atoms.). According to the polishing composition having a configuration containing the nitrogen-containing basic compound represented by the general formula (1), haze in polishing a silicon wafer can be suitably reduced.

In a preferred embodiment of the polishing composition disclosed herein, each of R ¹ , R ² , and R ³ is an alkyl group having 2 to 6 carbon atoms. By using such a nitrogen-containing basic compound, haze can be suitably reduced with a small amount.

  In a preferred embodiment of the polishing composition disclosed herein, the nitrogen-containing basic compound is triethylamine. Triethylamine can be used particularly preferably from the viewpoint of cost, because the pH of the polishing composition can be appropriately adjusted in a small amount, and the haze can be appropriately reduced.

  In one preferred embodiment of the polishing composition disclosed herein, the pH is 8 to 12. By including a nitrogen-containing basic compound represented by the above general formula (1) so that the pH of the polishing composition is adjusted within this range, the polishing rate is improved and the haze is more suitably reduced. can do.

  In a preferred embodiment of the polishing composition disclosed herein, the water-soluble polymer compound contains at least one selected from the group consisting of polyvinyl alcohol and modified polyvinyl alcohol. Thereby, the haze reducing effect of the nitrogen-containing basic compound represented by the general formula (1) is more suitably exhibited.

  In a preferred embodiment of the polishing composition disclosed herein, the abrasive grains are silica particles. The haze reduction effect of the nitrogen-containing basic compound represented by the general formula (1) is suitably exerted in polishing using silica particles as abrasive grains.

  In a preferred embodiment of the polishing composition disclosed herein, the abrasive particles have an average primary particle diameter of 20 nm or more and 30 nm or less. In the polishing composition disclosed herein, when an abrasive having such an average primary particle diameter is used, a haze reduction effect can be more suitably exerted.

  Further, the polishing composition disclosed herein can be preferably applied to a final polishing step of a silicon wafer. Such a final polishing step is a polishing step performed at the end of the polishing step, and thereafter, since polishing is not performed, it is particularly preferable to apply the polishing composition disclosed herein having a haze reducing effect. it can.

  Further, according to the present specification, there is provided a silicon wafer rinsing composition comprising water, a water-soluble polymer compound, and a nitrogen-containing basic compound represented by the above general formula (1). Such a rinsing composition is, for example, polished in the presence of abrasive grains (typically, water, a water-soluble polymer compound, and a nitrogen-containing basic compound represented by the general formula (1)). Is preferably used as a rinse liquid used after polishing (polishing in the presence of abrasive grains) using a polishing composition containing According to the above-mentioned rinsing liquid, haze can be reduced by appropriately protecting the surface of the silicon wafer in rinsing for removing abrasive grains remaining on the silicon wafer.

  Hereinafter, preferred embodiments of the present invention will be described. It should be noted that matters other than matters 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 conventional techniques in the relevant field. The present invention can be implemented based on the contents disclosed in this specification and common technical knowledge in the field.

<Polishing composition>
The polishing composition disclosed herein contains abrasive grains, water, a water-soluble polymer, and a nitrogen-containing basic compound. Hereinafter, the contents of the polishing composition disclosed herein will be described.

<Abrasives>
The polishing composition disclosed herein contains abrasive grains. The material and properties of the abrasive grains are not particularly limited, and can be appropriately selected depending on the purpose of use, the manner of use, and the like. Examples of the abrasive include inorganic particles, organic particles, and organic-inorganic composite particles. Specific examples of the inorganic particles include oxide particles such as silica particles, alumina particles, cerium oxide particles, chromium oxide particles, titanium dioxide particles, zirconium oxide particles, magnesium oxide particles, manganese dioxide particles, zinc oxide particles, and red iron oxide particles; Nitride particles such as silicon nitride particles and boron nitride particles; carbide particles such as silicon carbide particles and boron carbide particles; diamond particles; and carbonates such as calcium carbonate and barium carbonate. Specific examples of the organic particles include polymethyl methacrylate (PMMA) particles and poly (meth) acrylic acid particles (here, (meth) acrylic acid means acrylic acid and methacrylic acid comprehensively). And polyacrylonitrile particles. Such abrasive grains may be used alone or in combination of two or more.

  As the above-mentioned abrasive grains, inorganic particles are preferred, and among them, particles composed of a metal or metalloid oxide are preferred. Particularly preferred abrasive grains in the technology disclosed herein include silica particles. The technology disclosed herein can be preferably implemented, for example, in a mode in which the abrasive grains substantially consist 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 refers to silica particles.

  Specific examples of the silica particles include colloidal silica, fumed silica, and precipitated silica. The silica particles can be used alone or in combination of two or more. Colloidal silica is particularly preferred because it is unlikely to cause scratches on the surface of the object to be polished and can exhibit good polishing performance (such as performance of reducing surface roughness). As the colloidal silica, for example, colloidal silica produced by using water glass (Na silicate) as a raw material by an ion exchange method, or colloidal silica produced by an alkoxide method (colloidal silica produced by a hydrolysis-condensation reaction of alkoxysilane) is preferably used. be able to. 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, and even more preferably 1.7 or more. As the true specific gravity of silica increases, the polishing rate tends to increase. From this viewpoint, silica particles having a true specific gravity of 1.8 or more (eg, 1.85 or more) are particularly preferable. The upper limit of the true specific gravity of silica is not particularly limited, but is typically 2.2 or less, for example, 2.1 or less. As the true specific gravity of silica, a value measured by a liquid replacement method using ethanol as a replacement liquid can be adopted.

  In the technology disclosed herein, the abrasive grains contained in the polishing composition may be in the form of primary particles, or may be in the form of secondary particles in which a plurality of primary particles are associated. Further, abrasive grains in the form of primary particles and abrasive grains in the form of secondary particles may be mixed. In a preferred embodiment, at least some of the abrasive grains are contained in the polishing composition in the form of secondary particles.

Abrasives disclosed herein is (typically silica particles) is not particularly limited average primary particle diameter D _P1 of, based on the viewpoint of suitably exhibit the effect of reducing haze due to the nitrogen-containing basic compound to be described later It is preferable to adjust appropriately. Typically, the average primary particle diameter _{D P1} is suitably at least 1 nm, preferably 5nm or more, more preferably 10nm or more, more preferably 15nm or more, and particularly preferably 20nm or more. The average primary particle diameter _{D P1} of the abrasive grains is appropriate to the extent 200nm or less, preferably 100nm or less, more preferably 50nm or less, more preferably 40nm or less, particularly preferably be a 30nm or less. In particular, the final polishing step, since it is required to reduce the haze at a high level, it is preferable that the average primary particle diameter D _P1 of the abrasive grains to 20 nm to 30 nm. Thereby, the haze reduction effect by the nitrogen-containing basic compound described later can be more suitably exerted.
It should be noted that the average primary particle diameter _{D P1} herein, the specific surface area measured by the BET method (BET value), BET diameter (nm) = 6000 / (true density (g / cm ³⁾ × BET value ( m ² / g)). For example, in the case of silica particles, the BET diameter can be calculated from the BET diameter (nm) = 2727 / BET value (m ² / g). The specific surface area can be measured using, for example, a surface area measuring device manufactured by Micromeritex Co., Ltd., trade name “Flow Sorb II 2300”.

But not limited abrasive grains having an average secondary particle diameter D _P2 in particular, from the viewpoint of polishing rate is preferably 15nm or more, and more preferably 25nm or more. In light of obtaining a higher polishing effect, the average secondary particle diameter _DP2 is preferably equal to or greater than 30 nm, and more preferably equal to or greater than 40 nm. From the viewpoint of storage stability (e.g., dispersion stability), average secondary particle diameter _{D P2} of the abrasive grains is appropriately 200nm or less, preferably 150nm or less, more preferably 100nm or less, more preferably 70nm or less , For example, 50 nm or less. Average abrasive grain of the secondary particle diameter D _P2, for example, can be measured by a dynamic light scattering method using a Nikkiso Co. Model "UPA-UT151".

The average secondary particle diameter D _P2 of the abrasive grains is generally equal to or greater than the average primary particle diameter D _P1 of the abrasive grains (D _P2 / D _P1 ≧ 1), and is typically larger than D _P1 (D _P2 / D _P1 > 1). Although not particularly limited, in view of the polishing effect and surface smoothness of the polished, _D P2 _{/ D P1} of the abrasive grains is suitably in the range of 1.05 to 3, 1.1 to A range of 2.5 is preferable, and a range of 1.2 to 2.4, for example, 1.3 to 2.3 is more preferable.

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

  Although not particularly limited, the average value (average aspect ratio) of the major axis / minor axis ratio of the primary particles of the abrasive grains is preferably 1.05 or more, more preferably 1.1 or more. A higher polishing rate can be achieved by such an increase in the average aspect ratio. Further, the average aspect ratio is preferably 3.0 or less, more preferably 2.0 or less, and still more preferably 1.5 or less, from the viewpoint of reducing scratches.

  The shape (outer shape) and average aspect ratio of the primary particles of the abrasive grains can be grasped, for example, by observation with an electron microscope. As a specific procedure for grasping the average aspect ratio, for example, using a scanning electron microscope (SEM), for a predetermined number (for example, 200) of silica particles capable of recognizing the shape of independent particles, each particle image Draw the smallest rectangle circumscribing the. Then, for the rectangle drawn for each particle image, the value obtained by dividing the length of the long side (the value of the long axis) by the length of the short side (the value of the short axis) is the long diameter / short diameter ratio (aspect ratio). ). By arithmetically averaging the aspect ratios of the predetermined number of particles, an average aspect ratio can be obtained.

  The content of abrasive grains in the polishing composition disclosed herein is not particularly limited, and is preferably 0.01% by weight or more, more preferably 0.05% by weight or more, and still more preferably 0.075% by weight or more. , For example, 0.1% by weight or more. A higher polishing rate can be achieved by increasing the abrasive content. In addition, from the viewpoint of removability from a polishing object, the content is appropriately 10% by weight or less, preferably 5% by weight or less, more preferably 1% by weight or less, and further preferably 0.5% by weight or less. %, For example, 0.25% by weight or less.

<Water>
The polishing composition disclosed herein contains water. As the water, ion-exchanged water (deionized water), pure water, ultrapure water, distilled water, or the like can be preferably used. The water used preferably has a total content of transition metal ions of, for example, 100 ppb or less, in order to avoid as much as possible the effects of other components contained in the polishing composition. 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 matter by a filter, and distillation. Further, 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, it is preferable that 90% by volume or more of the solvent contained in the polishing composition is water, and it is more preferable that 95% by volume or more (typically 99 to 100% by volume) is water. In this specification, the term “aqueous solvent” may be used as a generic term including the above-mentioned solvent and water.

<Water-soluble polymer compound>
The polishing composition disclosed herein contains a water-soluble polymer compound. Such a water-soluble polymer compound has a function of protecting the surface of the silicon wafer by adsorbing and desorbing on the abrasive grains and the silicon wafer. The kind of the water-soluble polymer compound contained in the polishing composition disclosed herein can be appropriately selected from water-soluble polymer species known in the field of the polishing composition. The water-soluble polymer compound can be used alone or in combination of two or more. Examples of the water-soluble polymer compound include a polymer containing an oxyalkylene unit, a polymer containing a nitrogen atom, a synthetic polymer such as a polyvinyl alcohol-based polymer, and a natural polymer such as a cellulose derivative and a starch derivative.

Examples of the polymer containing an oxyalkylene unit include polyethylene oxide (PEO), a block copolymer of ethylene oxide (EO) and propylene oxide (PO) or butylene oxide (BO), and a random copolymer of EO and PO or BO. Coalescence and the like are exemplified. Among them, a block copolymer of EO and PO or a random copolymer of EO and PO is preferable. The block copolymer of EO and PO may be a diblock or triblock containing a PEO block and a polypropylene oxide (PPO) block. Examples of the triblock include a PEO-PPO-PEO triblock and a PPO-PEO-PPO triblock. Among them, a PEO-PPO-PEO triblock is more preferable.
In the block copolymer or random copolymer of EO and PO, the molar ratio (EO / PO) of EO and PO constituting the copolymer is determined from the viewpoints of solubility in water and detergency. It is preferably larger than 1, more preferably 2 or more, and still more preferably 3 or more (for example, 5 or more).

  As the polymer containing a nitrogen atom, any of a polymer containing a nitrogen atom in a main chain and a polymer containing a nitrogen atom in a side chain functional group (pendant group) can be used. By using a polymer containing a nitrogen atom, the surface roughness of the substrate can be improved. Examples of the polymer containing a nitrogen atom in the main chain include homopolymers and copolymers of N-acylalkyleneimine type monomers. Specific examples of the N-acylalkyleneimine type monomer include N-acetylethyleneimine and N-propionylethyleneimine. Examples of the polymer having a nitrogen atom in the pendant group include a polymer containing an N-vinyl type monomer unit. For example, a homopolymer and a copolymer of N-vinylpyrrolidone may be employed. In the technology disclosed herein, at least one of a homopolymer and a copolymer of N-vinylpyrrolidone obtained by polymerizing N-vinylpyrrolidone at a ratio of 50 mol% or more is preferably used.

  In the technology disclosed herein, a polyvinyl alcohol (PVA) polymer can be particularly preferably used as the water-soluble polymer compound. When a PVA-based polymer is used as the water-soluble polymer compound, the interaction with the nitrogen-containing basic compound described below can be particularly suitably generated, so that the surface of the silicon wafer is suitably protected and excellent haze reduction is achieved. The effect can be demonstrated.

As the polyvinyl alcohol-based polymer, a water-soluble organic substance (typically, a water-soluble polymer) containing a vinyl alcohol unit as a repeating unit is used. Here, the vinyl alcohol unit (hereinafter, also referred to as “VA unit”) is a structural portion represented by the following chemical formula: —CH ₂ —CH (OH) —; The VA unit can be produced, for example, by hydrolyzing (saponifying) a repeating unit (—CH ₂ —CH (OCOCH ₃ ) —) having a structure in which vinyl acetate is vinyl-polymerized. In some aspects of the technology disclosed herein, PVA in which the degree of saponification of polyvinyl acetate is, for example, 95% or more, or 98% or more may be preferably used.

  The polyvinyl alcohol-based polymer may include only a VA unit as a repeating unit, or may include a repeating unit other than the VA unit (hereinafter, also referred to as a “non-VA unit”) in addition to the VA unit. In the embodiment in which the polyvinyl alcohol-based polymer contains a non-VA unit, the non-VA unit includes an oxyalkylene group, a carboxy group, a sulfo group, an amino group, a hydroxyl group, an amide group, an imide group, a nitrile group, an ether group, an ester group, and May be a repeating unit having at least one structure selected from salts of The polyvinyl alcohol-based polymer may be a random copolymer containing VA units and non-VA units, or may be a block copolymer or a graft copolymer. The polyvinyl alcohol-based polymer may include only one type of non-VA unit, or may include two or more types of non-VA units.

  The ratio of the mole number of the VA unit to the mole number of all the repeating units constituting the polyvinyl alcohol-based polymer may be, for example, 5% or more, 10% or more, 20% or more, or 30% or more. . Although not particularly limited, in some embodiments, the ratio of the number of moles of the VA unit may be 50% or more, 65% or more, 75% or more, or 80% or more, It may be 90% or more (for example, 95% or more, or 98% or more). Substantially 100% of the repeating units constituting the polyvinyl alcohol-based polymer may be VA units. Here, “substantially 100%” means that the polyvinyl alcohol-based polymer does not contain non-VA units at least intentionally. In some other aspects, the ratio of the number of moles of VA units to the number of moles of all repeating units constituting the polyvinyl alcohol-based polymer may be, for example, 95% or less, 90% or less, or 80% or less. Or 70% or less.

  The content of VA units (content on a weight basis) in the polyvinyl alcohol-based polymer may be, for example, 5% by weight or more, 10% by weight or more, 20% by weight or more, or 30% by weight or more. Although not particularly limited, in some embodiments, the content of the VA unit may be 50% by weight or more (for example, more than 50% by weight), 70% by weight or more, or 80% by weight or more ( For example, 90% by weight or more, or 95% by weight or more, or 98% by weight or more). Substantially 100% by weight of the repeating units constituting the polyvinyl alcohol-based polymer may be VA units. Here, “substantially 100% by weight” means that non-VA units are not contained at least intentionally as a repeating unit constituting the polyvinyl alcohol-based polymer. In some other embodiments, the content of VA units in the polyvinyl alcohol-based polymer may be, for example, 95% by weight or less, 90% by weight or less, 80% by weight or less, or 70% by weight or less. .

  The polyvinyl alcohol-based polymer may include a plurality of polymer chains having different contents of VA units in the same molecule. Here, the polymer chain refers to a portion (segment) constituting a part of one molecule of polymer. For example, a polyvinyl alcohol-based polymer has a polymer chain A having a content of VA units higher than 50% by weight and a content of VA units lower than 50% by weight (that is, a content of non-VA units is higher than 50% by weight). And) the polymer chain B may be contained in the same molecule.

  The polymer chain A may contain only VA units as repeating units, or may contain non-VA units in addition to VA units. The content of VA units in the polymer chain A may be 60% by weight or more, 70% by weight or more, 80% by weight or more, or 90% by weight or more. In some embodiments, the content of VA units in polymer chain A may be greater than or equal to 95 wt%, and may be greater than or equal to 98 wt%. Substantially 100% by weight of the repeating units constituting the polymer chain A may be VA units.

  The polymer chain B may include only a non-VA unit as a repeating unit, or may include a VA unit in addition to the non-VA unit. The content of the non-VA unit in the polymer chain B may be 60% by weight or more, 70% by weight or more, 80% by weight or more, or 90% by weight or more. In some embodiments, the content of non-VA units in polymer chain B may be greater than or equal to 95 wt%, and may be greater than or equal to 98 wt%. Substantially 100% by weight of the repeating units constituting the polymer chain B may be non-VA units.

  Examples of the polyvinyl alcohol-based polymer containing the polymer chains A and B in the same molecule include a block copolymer and a graft copolymer containing these polymer chains. The above graft copolymer may be a graft copolymer having a structure in which a polymer chain A (main chain) is grafted with a polymer chain B (side chain), and the polymer chain B (main chain) is connected to the polymer chain A (side chain). Chain) may be a graft copolymer having a grafted structure. In one embodiment, a polyvinyl alcohol-based polymer having a structure in which a polymer chain B is grafted to a polymer chain A can be used.

  Examples of the polymer chain B include a polymer chain having a repeating unit derived from an N-vinyl type monomer as a main repeating unit and a polymer having a repeating unit derived from an N- (meth) acryloyl type monomer as a main repeating unit. Chains. In addition, in this specification, the main repeating unit means a repeating unit contained in excess of 50% by weight, unless otherwise specified.

  A preferable example of the polymer chain B is a polymer chain having an N-vinyl type monomer as a main repeating unit, that is, an N-vinyl polymer chain. The content of the repeating unit derived from the N-vinyl type monomer in the N-vinyl polymer chain is typically more than 50% by weight, may be 70% by weight or more, and may be 85% by weight or more. And may be 95% by weight or more. Substantially all of the polymer chain B may be a repeating unit derived from an N-vinyl type monomer.

  Examples of the N-vinyl type monomer include a monomer having a nitrogen-containing heterocycle (for example, a lactam ring) and an N-vinyl chain amide. Specific examples of the N-vinyllactam type monomer include N-vinylpyrrolidone, N-vinylpiperidone, N-vinylmorpholinone, N-vinylcaprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl- 3,5-morpholinedione and the like. Specific examples of the N-vinyl chain amide include N-vinylacetamide, N-vinylpropionic amide, N-vinylbutyric amide, and the like. The polymer chain B is, for example, an N-vinyl-based polymer chain in which more than 50% by weight (for example, 70% by weight or more, 85% by weight or more, or 95% by weight or more) of the repeating units are N-vinylpyrrolidone units. obtain. Substantially all of the repeating units constituting the polymer chain B may be N-vinylpyrrolidone units.

  Another example of the polymer chain B is a polymer chain having a main repeating unit derived from an N- (meth) acryloyl-type monomer, that is, an N- (meth) acryloyl-based polymer chain. The content of the repeating unit derived from the N- (meth) acryloyl-type monomer in the N- (meth) acryloyl-based polymer chain is typically more than 50% by weight, and may be 70% by weight or more. % Or more, and may be 95% or more. Substantially all of the polymer chain B may be a repeating unit derived from an N- (meth) acryloyl-type monomer.

  Examples of the N- (meth) acryloyl-type monomer include a chain amide having an N- (meth) acryloyl group and a cyclic amide having an N- (meth) acryloyl group. Examples of the linear amide having an N- (meth) acryloyl group include (meth) acrylamide; N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, N-isopropyl ( N-alkyl (meth) acrylamides such as meth) acrylamide and Nn-butyl (meth) acrylamide; N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dipropyl (meth) ) N, N-dialkyl (meth) acrylamides such as acrylamide, N, N-diisopropyl (meth) acrylamide, N, N-di (n-butyl) (meth) acrylamide; Examples of the cyclic amide having an N- (meth) acryloyl group include N- (meth) acryloylmorpholine, N- (meth) acryloylpyrrolidine and the like.

  Another example of the polymer chain B is a polymer chain containing an oxyalkylene unit as a main repeating unit, that is, an oxyalkylene-based polymer chain. The content of the oxyalkylene unit in the oxyalkylene-based polymer chain is typically more than 50% by weight, may be 70% by weight or more, may be 85% by weight or more, and may be 95% by weight or more. There may be. Substantially all of the repeating units contained in the polymer chain B may be oxyalkylene units.

  Examples of the oxyalkylene unit include an oxyethylene unit, an oxypropylene unit, and an oxybutylene unit. Each such oxyalkylene unit may be a repeating unit derived from the corresponding alkylene oxide. The number of oxyalkylene units contained in the oxyalkylene-based polymer chain may be one, or two or more. For example, it may be an oxyalkylene polymer chain containing a combination of oxyethylene units and oxypropylene units. In the oxyalkylene-based polymer chain containing two or more types of oxyalkylene units, the oxyalkylene units may be a random copolymer of the corresponding alkylene oxide, a block copolymer or a graft copolymer. Is also good.

  Other examples of the polymer chain B include an alkyl vinyl ether unit, a structural unit obtained by acetalizing polyvinyl alcohol and an aldehyde, and the like. Among them, vinyl ether units having an alkyl group having 1 to 10 carbon atoms (alkyl vinyl ether units), vinyl ester units derived from monocarboxylic acids having 1 to 7 carbon atoms (monocarboxylic acid vinyl ester units), In addition, it is preferable to be selected from the group consisting of structural units obtained by acetalizing polyvinyl alcohol and an aldehyde having an alkyl group having 1 to 7 carbon atoms.

  Examples of the vinyl ether unit having an alkyl group having 1 to 10 carbon atoms include a propyl vinyl ether unit, a butyl vinyl ether unit, and a 2-ethylhexyl vinyl ether unit. Examples of vinyl ester units derived from a monocarboxylic acid having 1 to 7 carbon atoms include vinyl propanoate units, vinyl butanoate units, vinyl pentanoate units, and vinyl hexanoate units.

  The polyvinyl alcohol-based polymer used in the polishing composition disclosed herein may be unmodified PVA (unmodified PVA), or modified PVA which is a copolymer containing VA units and non-VA units. It may be. Unmodified PVA and modified PVA may be used in combination. For example, the content of the modified PVA is preferably less than 50% by weight, more preferably 30% by weight or less, still more preferably 10% by weight or less, and 5% by weight or less based on the total amount of PVA. And may be 1% by weight or less. In some embodiments of the polishing composition disclosed herein, as the polyvinyl alcohol-based polymer, PVA containing only unmodified PVA can be preferably used.

  In addition, as the water-soluble polymer compound disclosed herein, a natural polymer such as a cellulose derivative or a starch derivative can be used in addition to the synthetic polymer described above. The cellulose derivative is a polymer containing a β-glucose unit as a main repeating unit, and examples thereof include methylcellulose, ethylcellulose, hydroxyethylcellulose (HEC), and methylhydroxyethylcellulose. The starch derivative is a polymer containing an α-glucose unit as a main repeating unit, and includes pregelatinized starch, pullulan, carboxymethyl starch, cyclodextrin and the like. However, since these are derived from natural products, it is difficult to highly reduce local disorder of the polymer structure, mixing of foreign substances, and the like. Therefore, it is preferable that the polishing composition disclosed herein does not substantially contain a natural polymer from the viewpoint of controlling the quality of the wafer surface at a high level. In addition, not including a natural polymer substantially means not including a natural polymer at least intentionally. Therefore, although a water-soluble polymer compound other than a natural polymer is used, a polishing composition containing a trace amount of a natural polymer inevitably derived from raw materials and manufacturing methods, etc. It can be included in the concept of a polishing composition that is substantially free. For example, when the content of the natural polymer is 0.001 wt% or less, preferably 0.0005 wt% or less, more preferably 0.0001 wt% or less, and particularly preferably 0.00001 wt% or less, the natural polymer is substantially contained. Not included in the concept of polishing composition.

In the technology disclosed herein, the molecular weight of the water-soluble polymer compound is not particularly limited, but the preferable range of the molecular weight of the water-soluble polymer compound may vary depending on the type of the polymer used. For example, the weight average molecular weight (Mw) of the polymer containing an oxyalkylene unit, the polymer containing a nitrogen atom, and the polyvinyl alcohol-based polymer can be 100 × 10 ⁴ or less, and preferably 60 × 10 ⁴ or less. is there. From the viewpoint of concentration efficiency and the like, the Mw may be 30 × 10 ⁴ or less, preferably 20 × 10 ⁴ or less, for example, 10 × 10 ⁴ or less, and typically 8 × 10 ⁴ or less. Good. Further, from the viewpoint of suitably protecting the surface of the silicon wafer and reducing the haze, Mw may be, for example, 2000 or more, and usually preferably 5000 or more. In some embodiments, Mw is suitably at least 1.0 × 10 ⁴ , preferably at least 1.5 × 10 ⁴ , more preferably at least 2 × 10 ⁴ , even more preferably at least 3 × 10 ⁴ , for example 4 × 10 ⁴ or more, typically 5 × 10 ⁴ or more.

In the present specification, as the weight average molecular weight (Mw) of the water-soluble polymer compound and the surfactant, a value based on aqueous gel permeation chromatography (GPC) (aqueous, in terms of polyethylene oxide) can be adopted. . As the GPC measuring device, a model name “HLC-8320GPC” manufactured by Tosoh Corporation may be used. The measurement conditions may be as follows. The same method is adopted for the embodiments described later.
[GPC measurement conditions]
Sample concentration: 0.1% by weight
Column: TSKgel GMPWXL
Detector: Differential refractometer Eluent: 100 mM sodium nitrate aqueous solution / acetonitrile = 10-8 / 0-2
Flow rate: 1 mL / min Measurement temperature: 40 ° C
Sample injection volume: 200 μL

  The content of the water-soluble polymer compound in the polishing composition is suitably 0.0005% by weight or more, for example, 0.0025% by weight or more, from the viewpoint of improving polishing performance and surface quality. Is 0.005% by weight or more, for example, 0.0075% by weight or more. The upper limit of the content of the water-soluble polymer compound in the polishing composition can be, for example, 0.05% by weight or less. From the viewpoints of stability at the concentrated liquid stage, polishing rate, detergency, etc., the content of the water-soluble polymer compound is preferably 0.035% by weight or less, more preferably 0.025% by weight or less, and further preferably It is at most 0.02% by weight, particularly preferably at most 0.015% by weight, for example at most 0.0125% by weight, typically at most 0.01% by weight.

  Further, the content of the water-soluble polymer compound in the polishing composition disclosed herein can also be specified by the relative relationship with the abrasive grains. Specifically, the content of the water-soluble polymer compound in the polishing composition can be 0.01 part by weight or more based on 100 parts by weight of the abrasive grains. From the viewpoint of haze reduction and the like, the amount is suitably 0.1 part by weight or more, preferably 0.5 part by weight or more, more preferably 1 part by weight or more, and still more preferably 3 parts by weight or more. . Further, the content of the water-soluble polymer compound relative to 100 parts by weight of the abrasive grains may be 50 parts by weight or less, and can be 30 parts by weight or less. From the viewpoints of stability and polishing rate, the amount is suitably 15 parts by weight or less, preferably 10 parts by weight or less, more preferably 8 parts by weight or less, and even more preferably 7 parts by weight or less.

<Nitrogen-containing basic compound>
The polishing composition disclosed herein contains a nitrogen-containing basic compound represented by the following general formula (1). In the formula, R ¹ , R ² , and R ³ may each independently be a group selected from the group consisting of an alkyl group having 1 to 15 carbon atoms and a hydroxyalkyl group having 1 to 15 carbon atoms. The polishing composition disclosed herein may contain one kind of the nitrogen-containing basic compound represented by the following general formula (1) alone, or may contain two or more kinds in combination. May be.

  By polishing a silicon wafer using the polishing composition containing the nitrogen-containing basic compound represented by the general formula (1), haze can be suitably reduced. Although not interpreted as being particularly limited, the reason why such an effect is obtained is considered as follows, for example. As described above, the polishing composition contains a water-soluble polymer compound, and the water-soluble polymer compound adsorbs or desorbs on the abrasive grains or the silicon wafer, thereby protecting the surface of the silicon wafer. . In the polishing composition disclosed herein, the nitrogen-containing basic compound represented by the general formula (1) interacts with the water-soluble polymer compound, and the surface protection performance of the water-soluble polymer compound is improved. Therefore, it is considered that haze can be suitably reduced.

Hereinafter, the polishing composition represented by the general formula (1) will be described. As described above, R ¹ , R ² , and R ³ in the general formula (1) are each independently an alkyl group having 1 to 15 carbon atoms or a hydroxyalkyl group. In other words, each of R ¹ , R ² , and R ³ has a structure represented by (CH ₂ ) _n -X, wherein X is a methyl group or a hydroxy group, and n is 1 ~ 15. R ¹ , R ² , R ³ can be, for example, linear. Specifically, R ¹ , R ² , and R ³ are a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a nonyl group, a decyl group, an isooctyl group, or one of hydrogen atoms in these groups. It may be a group having a structure in which a moiety is substituted with a hydroxy group, and the like. Further, R ¹ , R ² , and R ³ may have a branch. Specifically, it may be an i-butyl group, an s-butyl group, a t-butyl group, or a group having a structure in which a part of hydrogen atoms in these groups is substituted with a hydroxy group. Further, the carbon number of R ¹ , R ² and R ³ is preferably 1 to 8, more preferably 2 to 6, and more preferably 2 to 4. The number of substitution by a hydroxy group is preferably 1 or 2, and is typically 1. Preferred examples of R ¹ , R ² , and R ³ include a straight-chain alkyl group having 2 to 6 carbon atoms, and one hydrogen atom at the end of the straight-chain alkyl group having 2 to 6 carbon atoms substituted with a hydroxy group. Hydroxyalkyl groups.

One preferred example of the nitrogen-containing basic compound is a tertiary amine in which all of R ¹ , R ² and R ³ are alkyl groups. For example, all of R ¹ , R ² , and R ³ are preferably an alkyl group having 1 to 8 carbon atoms, and more preferably an alkyl group having 2 to 6 carbon atoms. Specific examples of such a nitrogen-containing basic compound include trimethylamine, triethylamine, tripropylamine, tributylamine, tripentylamine, trihexylamine, triheptylamine, trioctylamine, N, N-dimethylethylamine, N, N -Diethylmethylamine, N, N-dimethylpropylamine, N, N-diethylpropylamine, N, N-dimethylbutylamine, N, N-diethylbutylamine, N, N-dimethylpentylamine, N, N-diethylpentylamine , N, N-dimethylhexylamine, N, N-diethylhexylamine, N-ethyl-N-methyl-1-propanamine, N, N-diisopropylethylamine; and the like. When these are used as the nitrogen-containing basic compounds, the pH of the polishing composition can be appropriately adjusted by a small amount of addition, and the haze can be appropriately reduced. Among these, triethylamine can be preferably used from the viewpoint of cost because the amount of addition required for adjusting the pH of the polishing composition can be particularly reduced.

Another preferred example of the nitrogen-containing basic compound is a compound in which all of R ¹ , R ² , and R ³ are hydroxyalkyl groups. For example, all of R ¹ , R ² , and R ³ are preferably a hydroxyalkyl group having 1 to 8 carbon atoms, and more preferably a hydroxyalkyl group having 2 to 6 carbon atoms. Specific examples of such a nitrogen-containing basic compound include trimethanolamine, triethanolamine, tripropanolamine, tributanolamine, tripentanolamine, trihexanolamine, triheptinolamine, and trioctynolamine. Is exemplified. Among them, triethanolamine can be preferably used because haze can be appropriately reduced.

Other examples of the nitrogen-containing basic compound include compounds in which R ¹ and R ² are an alkyl group and R ³ is a hydroxyalkyl group. At this time, the number of carbon atoms of each of the alkyl group and the hydroxyalkyl group is preferably 1 to 8, and more preferably 2 to 6. Specific examples of such a nitrogen-containing basic compound include dimethylmethanolamine, dimethylethanolamine, dimethylpropanolamine, dimethylbutanolamine, dimethylpentanolamine, dimethylhexanolamine, dimethylheptinolamine, dimethyloctynolamine, and diethylamine. Methanolamine, diethylethanolamine, diethylpropanolamine, diethylbutanolamine, diethylpentanolamine, diethylhexanolamine, diethylheptinolamine, diethyloctynolamine, dipropylmethanolamine, dipropylethanolamine, dipropylpropanolamine, Dipropylbutanolamine, dipropylpentanolamine, dipropylhexanolamine, dipropyl Tinolamine, dipropyloctynolamine, dibutylmethanolamine, dibutylethanolamine, dibutylpropanolamine, dibutylbutanolamine, dibutylpentanolamine, dibutylhexanolamine, dibutylheptinolamine, dibutyloctynolamine; and the like. .

Another example of the nitrogen-containing basic compound is a compound in which R ¹ is an alkyl group and R ² and R ³ are hydroxyalkyl groups. Similarly to the above, the number of carbon atoms of each of the alkyl group and the hydroxyalkyl group at this time is preferably 1 to 8, and more preferably 2 to 6. Specific examples of such a nitrogen-containing basic compound include methyldimethanolamine, methyldiethanolamine, methyldipropanolamine, methyldibutanolamine, methyldipentanolamine, methyldihexanolamine, ethyldimethanolamine, ethyldiethanolamine, Ethyldipropanolamine, ethyldibutanolamine, ethyldipentanolamine, ethyldihexanolamine, propyldimethanolamine, propyldiethanolamine, propyldipropanolamine, propyldibutanolamine, propyldipentanolamine, propyldihexanolamine, Butyldimethanolamine, butyldiethanolamine, butyldipropanolamine, butyldibutanolamine, butyldipentanol Amine, butyl di hexanolamine; and the like.

Further, the nitrogen-containing basic compound disclosed herein has a ring in which ^{two of} R ¹ , R ² , and R ³ are bonded to each other and the nitrogen atom (N) and the carbon atom (C) to which they are bonded. The remaining one may be a group selected from the group consisting of an alkyl group having 1 to 15 carbon atoms and a hydroxyalkyl group having 1 to 15 carbon atoms. The cyclic structure in this case is a hetero ring containing a carbon atom and a nitrogen atom as ring constituent atoms. The number of ring-constituting atoms of the hetero ring is not particularly limited, but is usually 3 to 9, typically 4 to 8, for example, 5 to 7. A preferred example of such a hetero ring is a pyrrole ring. Specific examples of such a nitrogen-containing basic compound include 1-methylpyrrolidine, 1-ethylpyrrolidine, 1-propylpyrrolidine, 1-butylpyrrolidine, 1-pentylpyrrolidine, 1-hexylpyrrolidine; and the like. Even when a nitrogen-containing basic compound having such a cyclic structure is used, an interaction with a water-soluble polymer compound can be caused to reduce haze.

  In the technology disclosed herein, the pH of the polishing composition is adjusted to a desired value using the nitrogen-containing basic compound represented by the above formula (1). At this time, the pH of the polishing composition is adjusted to at least 8 or more. Further, from the viewpoint of haze reduction, it is preferably 8.5 or more, more preferably 9 or more, particularly preferably 9.5 or more, and typically 10 or more. On the other hand, the upper limit of the pH of the polishing composition is preferably 12 or less, more preferably 11.5 or less, particularly preferably 11 or less, and typically 10.5 or less. . By adjusting the pH of the polishing composition in this way, the polishing rate can be improved. In the technology disclosed herein, the pH of a liquid composition (polishing composition, polishing liquid, rinsing composition, etc.) is measured using a pH meter (for example, a glass electrode type hydrogen ion concentration indicator manufactured by Horiba, Ltd.). (Model No. F-23)), using standard buffers (phthalate pH buffer pH: 4.01 (25 ° C.), neutral phosphate pH buffer pH: 6.86 (25 ° C.), carbonic acid After three-point calibration using a salt pH buffer (pH: 10.01 (25 ° C.)), the glass electrode is placed in the composition to be measured, and the value is measured after 2 minutes or more and stabilized. It can be understood by doing.

  For example, when using triethylamine as the nitrogen-containing basic compound and adjusting the pH of the polishing composition within the range of 8 to 12, the content of triethylamine is 0.00025 mol / L or more, preferably 0.00035 mol / L. The above is particularly preferably set to 0.0004 mol / L or more. The upper limit of the content of triethylamine is preferably 0.0015 mol / L or less, more preferably 0.001 mol / L or less, and even more preferably 0.0009 mol / L or less. As a result, the polishing rate can be improved, and the haze can be suitably reduced. On the other hand, when the pH of the polishing composition is adjusted within the range of 8 to 12 using triethanolamine, the content of triethanolamine is 0.005 mol / L or more, preferably 0.015 mol / L. The above is particularly preferably set to 0.02 mol / L or more. Further, the upper limit of the content of triethanolamine is preferably 0.25 mol / L or less, more preferably 0.175 mol / L or less, and particularly preferably 0.125 mol / L or less. In addition, as described above, triethylamine can appropriately adjust the pH of the polishing composition with a smaller amount than other nitrogen-containing basic compounds, and can reduce haze even with a small amount. It can be particularly preferably used from the viewpoint of.

  Note that the polishing composition disclosed herein contains another basic compound for pH adjustment as long as the nitrogen-containing basic compound represented by the general formula (1) is predominantly contained. You may go out. Examples of the other basic compound include ammonia, potassium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide and the like. However, from the viewpoint of suitably exhibiting the haze reduction effect of the nitrogen-containing basic compound, it is preferable that other basic compounds are not substantially contained. Specifically, the content of the other basic compound is 0.1 times or less, preferably 0.05 times or less, more preferably the nitrogen-containing basic compound represented by the general formula (1). Is 0.01 times or less, particularly preferably 0.005 times or less, for example, 0.001 times or less.

<Other ingredients>
The polishing composition disclosed herein is a surfactant, a buffer, a chelating agent, an organic acid, an organic acid salt, an inorganic acid, an inorganic acid salt, a preservative, as long as the effects of the present invention are not significantly impaired. If necessary, a known additive that can be used for a polishing composition (typically, a polishing composition used in a final polishing step of a silicon wafer), such as a fungicide, may be further contained. .

  For example, the polishing composition disclosed herein may include a surfactant. The addition of a surfactant to the polishing composition can contribute to a reduction in haze. As the surfactant, any of anionic, cationic, nonionic and amphoteric surfactants can be used. Usually, an anionic or nonionic surfactant can be preferably used. Nonionic surfactants are more preferable from the viewpoints of low foaming properties 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 alkylamine, polyoxyethylene fatty acid ester, polyoxyethylene glyceryl ether fatty acid Esters, polyoxyalkylene derivatives such as polyoxyethylene sorbitan fatty acid esters (eg, polyoxyalkylene adducts); copolymers of a plurality of oxyalkylenes (eg, diblock copolymers, triblock copolymers, Nonionic surfactants such as random copolymers and alternating copolymers). The surfactants can be used alone or in combination of two or more.

  Specific examples of the nonionic surfactant include a block copolymer of ethylene oxide (EO) and propylene oxide (PO) (diblock copolymer, PEO (polyethylene oxide) -PPO (polypropylene oxide) -PEO type Triblock, PPO-PEO-PPO triblock copolymer, etc.), random copolymer of EO and PO, polyoxyethylene glycol, polyoxyethylene propyl ether, polyoxyethylene butyl ether, polyoxyethylene pentyl ether , Polyoxyethylene hexyl ether, polyoxyethylene octyl ether, polyoxyethylene-2-ethylhexyl ether, polyoxyethylene nonyl ether, polyoxyethylene decyl ether, polyoxyethylene isodecyl Ether, polyoxyethylene tridecyl ether, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene isostearyl ether, polyoxyethylene oleyl ether, polyoxyethylene phenyl ether, polyoxyethylene octyl Phenyl ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene laurylamine, polyoxyethylene stearylamine, polyoxyethylene oleylamine, polyoxyethylene monolaurate, polyoxyethylene monolaurate Oxyethylene monostearate, polyoxyethylene disteary Acid ester, polyoxyethylene monooleate, polyoxyethylene dioleate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopartimate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, Polyoxyethylene sorbitan trioleate, polyoxyethylene sorbite tetraoleate, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, and the like. Among them, as preferred surfactants, block copolymers of EO and PO (particularly, PEO-PPO-PEO type triblock copolymers), random copolymers of EO and PO, and polyoxyethylene alkyl ethers ( For example, polyoxyethylene decyl ether) can be mentioned.

  The weight average molecular weight (Mw) of the surfactant is typically less than 2000, and is preferably 1900 or less (for example, less than 1800) from the viewpoint of filterability, detergency and the like. Further, the Mw of the surfactant is usually suitably 200 or more from the viewpoint of surface activity, and preferably 250 or more (for example, 300 or more) from the viewpoint of the effect of lowering the haze level. The more preferable range of Mw of the surfactant may vary depending on the type of the surfactant. For example, when polyoxyethylene alkyl ether is used as the surfactant, its Mw is preferably 1500 or less, and may be 1000 or less (for example, 500 or less). When a PEO-PPO-PEO-type triblock copolymer is used as a surfactant, its Mw is, for example, 500 or more, 1000 or more, or 1200 or more. As the Mw of the surfactant, a value (aqueous, converted to polyethylene glycol) determined by GPC can be adopted.

When the polishing composition disclosed herein contains a surfactant, the content thereof is not particularly limited as long as the effect of the present invention is not significantly impaired. Usually, from the viewpoint of detergency and the like, it is appropriate to set the content of the surfactant to 100 parts by weight or less based on 100 parts by weight of the abrasive grains, preferably 15 parts by weight or less, and more preferably 10 parts by weight or less (for example, 6 parts by weight). Part or less) is more preferable. From the viewpoint of better exhibiting the effect of use of the surfactant, the surfactant content relative to 100 parts by weight of the abrasive is suitably 0.001 part by weight or more, preferably 0.005 part by weight or more, and 0.01% by weight or more. It is more preferable that the amount is not less than 0.1 part by weight (for example, not less than 0.1 part by weight).
When the polishing composition disclosed herein contains a surfactant, the weight ratio (w1 / w2) between the content w1 of the water-soluble polymer and the content w2 of the surfactant is not particularly limited, For example, it can be in the range of 0.01 to 100, preferably in the range of 0.05 to 50, and more preferably in the range of 0.1 to 30.
Alternatively, from the viewpoint of simplification of the composition and the like, the polishing composition disclosed herein can be preferably practiced in an embodiment substantially not containing a surfactant.

  The chelating agent functions to suppress the contamination of the object to be polished by the metal impurities by forming and trapping complex ions with metal impurities that may be contained in the polishing composition. The chelating agents may be used alone or in combination of two or more. 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 nitrilotriacetate, hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetate, and diethylenetriaminepentaacetic acid. , Sodium diethylene triamine pentaacetate, triethylene tetramine hexaacetic acid and sodium triethylene tetramine hexaacetate. Examples of the organic phosphonic acid chelating agent include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid), ethylenediaminetetrakis (methylenephosphonic acid), and diethylenetriaminepenta (methylenephosphonic acid). 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-methylphosphonic acid Includes nosuccinic acid. Of these, organic phosphonic acid-based chelating agents are more preferred, and particularly preferred are aminotri (methylenephosphonic acid), ethylenediaminetetrakis (methylenephosphonic acid) and diethylenetriaminepenta (methylenephosphonic acid).

Examples of organic acids include formic acid, acetic acid, fatty acids such as propionic acid, benzoic acid, aromatic carboxylic acids such as phthalic acid, citric acid, oxalic acid, tartaric acid, malic acid, maleic acid, fumaric acid, succinic acid, and organic acids. Sulfonic acid, organic phosphonic acid and the like can be mentioned. Examples of the organic acid salts include alkali metal salts (sodium salts, potassium salts, etc.) and ammonium salts of organic acids. Examples of inorganic acids include sulfuric acid, nitric acid, hydrochloric acid, carbonic acid and the like. Examples of the inorganic acid salt include an alkali metal salt (sodium salt, potassium salt, etc.) and an ammonium salt of an inorganic acid. The organic acids and salts thereof, and the inorganic acids and salts thereof can be used alone or in combination of two or more.
Examples of preservatives and fungicides include isothiazoline compounds, paraoxybenzoates, phenoxyethanol and the like.

It is preferable that the polishing composition disclosed herein does not substantially contain an oxidizing agent. If an oxidizing agent is contained in the polishing composition, the surface of the silicon wafer is oxidized to form an oxide film, which increases the required polishing time. Specific examples of the oxidizing agent mentioned here include hydrogen peroxide (H ₂ O ₂ ), sodium persulfate, ammonium persulfate, sodium dichloroisocyanurate, and the like. In addition, that the polishing composition does not substantially contain an oxidizing agent means that the oxidizing agent is not contained at least intentionally. Therefore, a trace amount (for example, the molar concentration of the oxidizing agent in the polishing composition is 0.0005 mol / L or less, preferably 0.0001 mol or less, more preferably 0.00001 mol / L, particularly preferably 0.000001 mol / L or less) is unavoidably contained in the polishing composition which is included in the concept of the polishing composition substantially containing no oxidizing agent. Can be done.

<Preparation of polishing composition>
The method for producing the polishing composition disclosed herein is not particularly limited. For example, the components 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 manner in which these components are mixed is not particularly limited. For example, all components may be mixed at once, or may be mixed in an appropriately set order.

  The polishing composition disclosed herein may be of a one-part type or a multi-part type including a two-part type. For example, a liquid A containing a part of components of the polishing composition (typically, components other than the aqueous solvent) and a liquid B containing the remaining components are mixed to form a polishing object. It may be configured to be used for polishing. When the multi-drug type is adopted, it is preferable that the nitrogen-containing basic compound and the water-soluble polymer compound are contained in the same agent. Thereby, the interaction between the nitrogen-containing basic compound and the water-soluble polymer compound can be suitably generated, and the haze reducing effect can be suitably exerted.

<Polishing liquid>
The polishing composition disclosed herein is typically supplied on the surface of a polishing object in the form of a polishing liquid containing the polishing composition, and is used for polishing the polishing object. The polishing liquid may be, for example, one prepared by diluting (typically, diluting with water) any of the polishing compositions disclosed herein. Alternatively, the polishing composition may be used as a polishing liquid as it is. That is, the concept of the polishing composition in the technology disclosed herein includes a polishing liquid (working slurry) supplied to an object to be polished and used for polishing the object to be polished, and used as a polishing liquid after dilution. Both of a concentrated solution (a stock solution of a polishing solution) are included.

<Concentrate>
As described above, the polishing composition disclosed herein may be in a concentrated form before being supplied to the object to be polished (that is, in the form of a concentrated polishing solution). The polishing composition in such a concentrated form is advantageous from the viewpoints of convenience, cost reduction, and the like during production, distribution, storage, and the like. The concentration ratio can be, for example, about 2 to 60 times in terms of volume.

  The polishing composition in the form of a concentrated solution as described above can be used by diluting it at a desired timing to prepare a polishing solution, and supplying the polishing solution to an object to be polished. The dilution can be typically performed by adding the above-mentioned aqueous solvent to the concentrated solution and mixing. When the aqueous solvent is a mixed solvent, only a part of the components of the aqueous solvent may be added and diluted, and a mixture containing these components at a different ratio from the aqueous solvent may be used. It may be diluted by adding a solvent. In addition, as described later, in a multi-part polishing composition, a polishing liquid may be prepared by diluting some of them and then mixing with other parts to prepare a polishing liquid. The polishing liquid may be prepared by diluting the mixture later.

  The content of the abrasive grains in the concentrated liquid can be, for example, 25% by weight or less. From the viewpoints of stability of the polishing composition (eg, dispersion stability of abrasive grains) and filterability, the content is usually preferably 20% by weight or less, more preferably 15% by weight or less. . In a preferred embodiment, the content of the abrasive grains may be 10% by weight or less, or 5% by weight or less. From the viewpoints of convenience, cost reduction, and the like during production, distribution, storage, and the like, the content of abrasive grains in the concentrated solution can be, for example, 0.1% by weight or more, and preferably 0.5% by weight. % Or more, more preferably 0.7% by weight or more, and still more preferably 1% by weight or more.

<Application>
The technology disclosed herein is applied to polishing of a silicon wafer as a polishing target. A typical example of the silicon wafer mentioned here is a silicon single crystal wafer, for example, a silicon single crystal wafer obtained by slicing a silicon single crystal ingot. The surface to be polished in the technology disclosed herein is typically a surface made of silicon.

  Prior to the polishing step (polishing step) using the polishing liquid disclosed herein, the silicon wafer may be subjected to general processing that can be performed on the silicon wafer in a step upstream of the polishing step, such as lapping or etching. May be applied. Further, in the technology disclosed herein, in the polishing step, a preliminary polishing step (coarse polishing step) and a final polishing step (final polishing step) can be performed, and after the final polishing step, the surface of the silicon wafer has high quality. Finished with a mirror finish. Note that the final polishing step refers to the last polishing step in the manufacturing process of the object (that is, a step in which no further polishing is performed after that step). Since the polishing composition disclosed herein has a haze reducing effect, it can be preferably applied to a final polishing step in which the surface state after polishing is particularly required to be high quality.

<Polishing>
The polishing composition disclosed herein can be used for polishing a silicon wafer, for example, in a mode including the following operation. Hereinafter, a preferred embodiment of a method for polishing a silicon wafer using the polishing composition disclosed herein will be described. That is, a polishing liquid (typically a slurry-like polishing liquid, sometimes referred to as a polishing slurry) containing any of the polishing compositions disclosed herein is prepared. Preparing the polishing liquid may include preparing a polishing liquid by adding operations such as concentration adjustment (for example, dilution) and pH adjustment to the polishing composition. Alternatively, the above polishing composition may be used as a polishing liquid as it is. In addition, in the case of a multi-part polishing composition, preparing the above polishing liquid involves mixing those agents, diluting one or more agents before the mixing, and after the mixing. Diluting the mixture, and the like.

  Next, the polishing liquid is supplied onto a silicon wafer and polished by an ordinary method. For example, when performing a final polishing process on a silicon wafer, the silicon wafer that has undergone the lapping process and the preliminary polishing process is set in a general polishing apparatus, and the surface of the silicon wafer (the surface to be polished) is passed through a polishing pad of the polishing apparatus. ) Is supplied with a polishing liquid. Typically, while continuously supplying the polishing liquid, a polishing pad is pressed against the surface of the silicon wafer to relatively move (for example, rotate) the two. The polishing of the object to be polished is completed through the final polishing step. The polishing pad used in the above step is not particularly limited. For example, any of a nonwoven fabric type, a suede type, a material containing abrasive grains, and a material not containing abrasive grains may be used.

<Rinse composition>
The silicon wafer polished using the polishing composition can be rinsed using a rinsing liquid containing the same components as the polishing composition except that it does not contain abrasive grains. In other words, the technique disclosed herein may include a step of rinsing the silicon wafer using a rinsing liquid containing the same components as the above polishing composition except that it does not contain abrasive grains (rinsing step). By the rinsing step, residues such as abrasive grains which cause defects and haze on the surface of the silicon wafer can be reduced. The rinsing step may be performed between the polishing steps, or may be performed after the final polishing step and before the cleaning step described later. Such a rinsing liquid is typically a composition for rinsing a silicon wafer containing a water-soluble polymer compound, a nitrogen-containing basic compound, and water (specifically, a composition used for rinsing silicon wafers; rinsing. Also referred to as a composition for use.) By including the nitrogen-containing basic compound represented by the general formula (1) in the rinsing composition, rinsing can be performed while suitably protecting the surface of the silicon wafer. The composition of the silicon wafer rinsing composition and the like are basically the same as the above-described silicon wafer polishing composition except that they do not contain abrasive grains, and thus description thereof will not be repeated here.

<Washing>
A polished object polished using the polishing composition disclosed herein is typically washed after polishing (and, if necessary, after rinsing). This washing can be performed using an appropriate washing solution. The cleaning liquid to be used is not particularly limited, and for example, a SC-1 cleaning liquid (ammonium hydroxide (NH ₄ OH), hydrogen peroxide (H ₂ O ₂ ), and water (H ₂ O) commonly used in the field of semiconductors and the like is used. Hereinafter, washing with an SC-1 washing solution is referred to as “SC-1 washing”), SC-2 washing solution (mixed solution of HCl, H ₂ O ₂ and H ₂ O), and the like. Can be used. The temperature of the cleaning liquid can be, for example, about room temperature to about 90 ° C. From the viewpoint of improving the cleaning effect, a cleaning liquid at about 50 ° C to 85 ° C can be preferably used.

  Hereinafter, some examples of the present invention will be described, but the present invention is not intended to be limited to those shown in the examples. In the following description, “parts” and “%” are based on weight unless otherwise specified.

≪Test A≫
<Preparation of polishing composition>
(Example 1A)
A polishing composition was prepared by mixing abrasive grains, a water-soluble polymer, deionized water, and a nitrogen-containing basic compound. Colloidal silica (average primary particle size: 25 nm, average secondary particle size: 46 nm) was used as the abrasive, and the content was 3.5%. Polyvinyl alcohol (PVA) was used as the water-soluble polymer. PVA having a weight average molecular weight (Mw) of about 70000 and a degree of saponification of 98% or more was used, and the content was 0.175%. In this example, triethylamine was used as the nitrogen-containing basic compound, and the content was 0.012 mol / L. These were diluted 20 times with deionized water, and the pH of the polishing composition was adjusted to 10.2. Table 1 shows the content of each component in the polishing composition.

(Example 2A)
In this example, triethanolamine was used instead of triethylamine. In other respects, the polishing composition of this example was prepared in the same manner as in Example 1A.

(Comparative Example 1A)
In this example, ammonia (NH ₃ ) was used instead of triethylamine. In other respects, the polishing composition of this example was prepared in the same manner as in Example 1A.

(Comparative Examples 2A to 6A)
In Comparative Examples 2A to 6A, the amines shown in Table 1 were used instead of triethylamine. The content of the amine in each comparative example is as shown in Table 1. The other points were the same as in Example 1A.

<Silicon wafer polishing>
In this test, a polishing step including a preliminary polishing step and a final polishing step was performed, and the silicon wafer was polished. As the silicon wafer, a COP (Crystal Originated Particle) -free silicon wafer having a diameter of 200 mm, a conduction type of P type, and a crystal orientation of <100> was used.

  In the preliminary polishing step, polishing was performed under the following conditions using a preliminary polishing liquid in which abrasive grains (colloidal silica having an average primary particle diameter of 35 nm), potassium hydroxide (KOH), and deionized water were mixed. The content of abrasive grains in the preliminary polishing liquid was 0.95%, and the content of potassium hydroxide was 0.065%.

(Conditions for the preliminary polishing process)
Polishing equipment: Single wafer polishing equipment manufactured by Okamoto Machine Tool Works, Ltd. Model "PNX-322"
Polishing load: 15kPa
Platen rotation speed: 30 rpm
Head (carrier) rotation speed: 30 rpm
Polishing pad: Fujibo Ehime Co., Ltd. Product name "FP55"
Supply rate of preliminary polishing liquid: 550 mL / min
Pre-polishing liquid temperature: 20 ° C
Surface plate cooling water temperature: 20 ° C
Polishing time: 3min

  Next, in the final polishing step, the polishing composition according to each example was used as a polishing liquid, and the surface of the silicon wafer was polished under the following conditions.

(Final polishing process conditions)
Polishing equipment: Single wafer polishing equipment manufactured by Okamoto Machine Tool Works, Ltd. Model "PNX-322"
Polishing load: 15kPa
Platen rotation speed: 30 rpm
Head (carrier) rotation speed: 30 rpm
Polishing pad: Fujibo Ehime Co., Ltd. Product name "POLYPAS27NX"
Polishing liquid supply rate: 400 mL / min
Polishing liquid temperature: 20 ° C
Surface plate cooling water temperature: 20 ° C
Polishing time: 4min

Then, the polished silicon wafer was cleaned (SC-1 cleaning). In this step, first, two cleaning tanks containing the cleaning liquid were prepared, and the temperature of the cleaning liquid in each of the cleaning tanks was maintained at 60 ° C. Next, the silicon wafer after the final polishing step was immersed in the first cleaning tank for 6 minutes, and then subjected to ultrasonic treatment using an ultrasonic oscillator while immersed in ultrapure water. Then, after being immersed in the second cleaning tank for 5 minutes, it was dried using a spin drier. In this step, ammonium hydroxide (NH ₄ OH), aqueous hydrogen peroxide (H ₂ O ₂ ), and deionized water (DIW) were mixed at a ratio of 1: 1: 15 by volume as a cleaning liquid. The mixed solution used was used.

<Haze measurement>
The haze (ppm) of the cleaned silicon wafer surface was measured in a DWO mode using a wafer inspection apparatus manufactured by KLA-Tencor Co., Ltd., trade name “Surfscan SP2 ^XP ”. The obtained results are shown in Table 1 in terms of a relative value (haze ratio) with the haze value of Comparative Example 1A being 100%. When the haze ratio is less than 100%, the haze reduction effect can be significantly confirmed.

  As shown in Table 1, the haze of Examples 1A and 2A using triethylamine or triethanolamine as the nitrogen-containing basic compound was lower than Comparative Examples 1A to 6A using other nitrogen-containing basic compounds. Was. From this result, according to the polishing using the polishing composition containing the nitrogen-containing basic compound represented by the above general formula (1) such as triethylamine or triethanolamine, the generation of haze on the silicon wafer surface after polishing is reduced. It can be seen that it can be reduced suitably. In particular, in Example 1A, a sufficient haze reduction effect was exhibited even though the content of the nitrogen-containing basic compound was reduced. From this, it can be seen that among the nitrogen-containing basic compounds represented by the general formula (1), triethylamine is preferable from the viewpoint of cost because haze can be suitably reduced even with a small content. .

≪Test B≫
<Preparation of polishing composition>
(Examples 1B to 3B)
In Examples 1B to 3B, a polishing composition was prepared under the same conditions as in Example 1A of Test A above, except that the target pH of the polishing composition was changed to vary the content of triethylamine. . The target pH and the content of triethylamine in each example are as shown in Table 2.

(Examples 4B to 6B)
In Examples 4B to 6B, except that the target pH of the polishing composition was changed and the content of triethanolamine was changed, the polishing composition was used under the same conditions as in Example 2A of Test A above. Prepared. The target pH and the content of triethanolamine in each example are as shown in Table 2.

(Comparative Example 1B)
For comparison, a polishing composition was prepared under the same conditions as in Comparative Example 1A of Test A.

<Silicon wafer polishing>
The final polishing step of the silicon wafer was performed using the polishing compositions of Examples 1B to 6B and Comparative Example 1B as a polishing liquid. Note that the polishing conditions and the cleaning conditions are the same as those in the above-described test A, and thus description thereof is omitted here.

<Haze measurement>
The haze of the surface of the silicon wafer on which the final polishing step was performed using the polishing composition of each example was measured in the same procedure as in the test A described above. The obtained results are shown in Table 2 in terms of a relative value (haze ratio) with the haze value of Comparative Example 1B being 100%. When the haze ratio is less than 100%, the haze reduction effect can be significantly confirmed.

  As shown in Table 2, in all of Examples 1B to 6B, it was confirmed that the haze reduction effect was properly exhibited. From this, it can be seen that the haze of the silicon wafer can be suitably reduced even when the target pH of the polishing composition is set to a value different from the above-mentioned test A and the content of the nitrogen-containing basic compound is changed. .

  As described above, the specific examples of the present invention have been described in detail. However, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples illustrated above.

Claims (9)

Abrasive grains, water, a water-soluble polymer compound, and a nitrogen-containing basic compound,
The nitrogen-containing basic compound has the following general formula (1):

(Wherein, R ¹ , R ² , and R ³ are each independently a group selected from the group consisting of an alkyl group having 1 to 15 carbon atoms and a hydroxyalkyl group having 1 to 15 carbon atoms, or ^{Two of} R ¹ , R ² and R ³ are bonded to each other to form a ring structure containing a nitrogen atom and a carbon atom to which they are bonded, and the other one is an alkyl group having 1 to 15 carbon atoms and A group selected from the group consisting of hydroxyalkyl groups having 1 to 15 carbon atoms.); Wherein ^{R 1,} R 2, each ^{R 3} is an alkyl group having 2 to 6 carbon atoms, a silicon wafer polishing composition according to claim 1.   The composition for polishing a silicon wafer according to claim 2, wherein the nitrogen-containing basic compound is triethylamine.   The composition for polishing a silicon wafer according to any one of claims 1 to 3, wherein the composition has a pH of 8 to 12.   The composition for polishing a silicon wafer according to any one of claims 1 to 4, wherein the water-soluble polymer compound includes at least one selected from the group consisting of polyvinyl alcohol and modified polyvinyl alcohol.   The composition for polishing a silicon wafer according to any one of claims 1 to 5, wherein the abrasive grains are silica particles.   The composition for polishing a silicon wafer according to any one of claims 1 to 6, wherein the abrasive particles have an average primary particle diameter of 20 nm or more and 30 nm or less.   The silicon wafer polishing composition according to any one of claims 1 to 7, which is used in a final polishing step of a silicon wafer. Including water, a water-soluble polymer compound, and a nitrogen-containing basic compound,
The nitrogen-containing basic compound has the following general formula (1):

(Wherein, R ¹ , R ² , and R ³ are each independently a group selected from the group consisting of an alkyl group having 1 to 15 carbon atoms and a hydroxyalkyl group having 1 to 15 carbon atoms, or ^{Two of} R ¹ , R ² and R ³ are bonded to each other to form a ring structure containing a nitrogen atom and a carbon atom to which they are bonded, and the other one is an alkyl group having 1 to 15 carbon atoms and A group selected from the group consisting of hydroxyalkyl groups having 1 to 15 carbon atoms.);