JP2018145261A - Polishing composition and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing composition having excellent performance of resolving protrusions around a hard laser mark.SOLUTION: A polishing composition contains an abrasive grain, a basic compound, water, and an oxidizing agent, and has a pH of 9-12.SELECTED DRAWING: None

Description

  The present invention relates to a polishing composition and a method for producing the polishing composition.

  Conventionally, precision polishing using a polishing composition has been performed on the surface of materials such as metals, metalloids, nonmetals, and oxides thereof. For example, the surface of a silicon wafer used as a component of a semiconductor product or the like is generally finished to a high-quality mirror surface through a lapping process and a polishing process (precision polishing process). The polishing process typically includes a preliminary polishing process (preliminary polishing process) and a final polishing process (final polishing process).

  For the purpose of identification or the like, a silicon wafer may be marked with a mark (hard laser mark) such as a bar code, a number, or a symbol by irradiating the front or back surface of the silicon wafer with laser light. Such a hard laser mark is generally applied after the lapping process of the silicon wafer is finished and before the polishing process is started.

  Usually, an altered layer is generated around the periphery of the hard laser mark by the irradiation of the laser beam for attaching the hard laser mark. When preliminary polishing such as primary polishing is performed in a state where a deteriorated layer is generated, the deteriorated layer is difficult to be polished, and thus a bulge is generated at the periphery of the hard laser mark and the flatness of the silicon wafer may be lowered. For example, Patent Document 1 discloses a polishing composition containing abrasive grains, a weak acid salt, and a quaternary ammonium compound, and the polishing composition suppresses pH fluctuations and maintains polishing efficiency. It is described that the bulge at the periphery of the hard laser mark can be eliminated.

JP2015-233031 A

  However, since the above-mentioned deteriorated layer portion is often hardened by being transformed into polysilicon or the like by the energy of the laser beam, it is still difficult to effectively eliminate the above bulge with the polishing composition as in Patent Document 1. It was insufficient.

  This invention is made | formed in view of this situation, Comprising: It aims at providing the polishing composition excellent in the performance which eliminates the protrusion of a hard laser mark periphery.

  Furthermore, this invention aims at providing the manufacturing method of the said polishing composition.

  The present inventors have found that the above problem can be solved by including an oxidizing agent in the polishing composition, and have completed the present invention.

  That is, the present invention relates to a polishing composition containing abrasive grains, a basic compound, water, and an oxidizing agent and having a pH of 9 to 12.

  Furthermore, this invention relates also to the manufacturing method of the said polishing composition.

  ADVANTAGE OF THE INVENTION According to this invention, the polishing composition excellent in the performance which eliminates the protrusion of a hard laser mark periphery is provided.

  Furthermore, according to this invention, the manufacturing method of the said polishing composition is provided.

  The polishing composition of the present invention contains abrasive grains, a basic compound, water, and an oxidizing agent, and has a pH of 9-12.

  According to the polishing composition of the present invention, it is possible to effectively eliminate the bulge at the periphery of the hard laser mark. In the present specification, to eliminate the protrusion of the peripheral edge of the hard laser mark means to reduce the height of the protrusion on the peripheral edge of the hard laser mark of the silicon wafer. The height of the protrusion on the periphery of the hard laser mark of the silicon wafer can be measured, for example, by the method described in Examples described later.

  The mechanism for obtaining such an effect is considered as follows. However, the following mechanism is just a guess, and the scope of the present invention is not limited thereby.

  In order to attach a hard laser mark to a silicon wafer, an irradiation process of laser light is performed. Therefore, a deteriorated layer is often generated in the single crystal silicon portion around the hard laser mark and is hardened. Therefore, when polishing a silicon wafer using a conventional polishing composition, the altered part of the periphery of the hard laser mark is less likely to be etched or mechanically polished by abrasive grains compared to other wafer parts, The polishing rate becomes slow. As a result, the ridges of the hard laser mark remain unresolved. On the other hand, when a silicon wafer is polished using the polishing composition of the present invention, the above-mentioned problems are solved. As a specific reason, when the oxidant described in the present invention is added, both the altered part of the periphery of the hard laser mark and the surface of the silicon wafer are changed to a Si oxide film by the oxidant, and therefore, the altered part and the other part are changed. It is considered that the difference in the polishing rate of the wafer portion becomes smaller and the raised height can be eliminated.

  Therefore, by polishing using the polishing composition of the present invention, the altered portion of the periphery of the hard laser mark and the other portions are polished at a polishing rate close to that, and the partial bulge can be eliminated.

  Embodiments of the present invention will be described below. In addition, this invention is not limited only to the following embodiment.

  In the present specification, unless otherwise specified, measurement of operation and physical properties is performed under conditions of room temperature (20 to 25 ° C.) / Relative humidity 40 to 50% RH.

<Abrasive>
The polishing composition of the present invention contains abrasive grains. The abrasive grains contained in the polishing composition have an action of mechanically polishing the object to be polished.

  The abrasive used may be any of inorganic particles, organic particles, and organic-inorganic composite particles. Specific examples of the inorganic particles include particles made of metal oxides such as silica, alumina, ceria, titania, silicon nitride particles, silicon carbide particles, and boron nitride particles. Specific examples of the organic particles include polymethyl methacrylate (PMMA) particles. These abrasive grains may be used alone or in combination of two or more. The abrasive grains may be commercially available products or synthetic products.

  Among these abrasive grains, silica is preferable, and colloidal silica is particularly preferable.

  The lower limit of the average primary particle diameter of the abrasive grains is preferably 10 nm or more, more preferably 15 nm or more, further preferably 20 nm or more, and particularly preferably 30 nm or more. Further, the upper limit of the average primary particle diameter of the abrasive grains is preferably 200 nm or less, more preferably 150 nm or less, and further preferably 100 nm or less. Within such a range, the polishing rate of the object to be polished by the polishing composition is further improved, and the occurrence of defects on the surface of the object to be polished after polishing with the polishing composition is further suppressed. be able to. In addition, the average primary particle diameter of an abrasive grain is calculated based on the specific surface area of the abrasive grain measured by BET method, for example.

  The lower limit of the average secondary particle diameter of the abrasive grains is preferably 15 nm or more, more preferably 30 nm or more, further preferably 50 nm or more, and particularly preferably 70 nm or more. Further, the upper limit of the average secondary particle diameter of the abrasive grains is preferably 300 nm or less, more preferably 260 nm or less, and further preferably 220 nm or less. Within such a range, the polishing rate of the object to be polished by the polishing composition is further improved, and the occurrence of defects on the surface of the object to be polished after polishing with the polishing composition is further suppressed. be able to. The average secondary particle diameter of the secondary particles can be measured, for example, by a dynamic light scattering method.

  The content of abrasive grains in the polishing composition according to the present invention is not particularly limited. As will be described later, in the case of a polishing composition (typically a slurry-like polishing liquid, sometimes referred to as a working slurry or a polishing slurry) used for polishing an object to be polished as it is as a polishing liquid, The content of abrasive grains in use with respect to the polishing composition is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and 0.5% by mass or more. More preferably. By increasing the content of the abrasive grains, there is a tendency that higher bulge resolution is obtained. Further, from the viewpoint of preventing scratches, the content of the abrasive grains during use is usually suitably 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, and more preferably 1% by mass or less. Particularly preferred. Reducing the content of abrasive grains is also preferable from the viewpoint of economy. The polishing composition according to the present invention can exhibit practically sufficient uplifting properties even at such a low abrasive content.

  In addition, in the case of a polishing composition (that is, a concentrated solution) that is diluted and used for polishing, the content of abrasive grains is usually 30% by mass or less from the viewpoint of storage stability, filterability, and the like. It is suitable and it is more preferable that it is 15 mass% or less. Moreover, from the viewpoint of taking advantage of the concentrated liquid, the content of the abrasive is preferably 1% by mass or more, more preferably 5% by mass or more.

<Water>
The polishing composition according to the present invention contains water as a dispersion medium in order to disperse or dissolve each component. It is preferable that water does not contain impurities as much as possible from the viewpoint of inhibiting the contamination of the object to be cleaned and the action of other components. As such water, for example, water having a total content of transition metal ions of 100 ppb or less is preferable. Here, the purity of water can be increased by operations such as removal of impurity ions using an ion exchange resin, removal of foreign matters by a filter, distillation, and the like. Specifically, as the water, for example, deionized water (ion exchange water), pure water, ultrapure water, distilled water, or the like is preferably used.

  The dispersion medium may be a mixed solvent of water and an organic solvent for dispersing or dissolving each component. In this case, examples of the organic solvent used include acetone, acetonitrile, ethanol, methanol, isopropanol, glycerin, ethylene glycol, propylene glycol and the like, which are organic solvents miscible with water. Further, these organic solvents may be used without being mixed with water, and each component may be dispersed or dissolved and then mixed with water. These organic solvents can be used alone or in combination of two or more.

<Oxidizing agent>
The polishing composition according to the present invention contains an oxidizing agent. By including the oxidizing agent, both the altered portion of the hard laser mark periphery and the surface of the silicon wafer are changed to a Si oxide film, and the difference in the polishing rate between the altered portion of the hard laser mark periphery and the bulge can be eliminated. it is conceivable that.

Examples of oxidants that can be used in the present invention include hydrogen peroxide, peracetic acid, percarbonate, urea peroxide, sodium persulfate, potassium persulfate, ammonium persulfate, potassium persulfate and oxone, chlorous acid (HClO). ₂ ), bromic acid (HBrO ₂ ), iodic acid (HIO ₂ ), sodium chlorite (NaClO ₂ ), potassium chlorite (KClO ₂ ), sodium bromite (NaBrO ₂ ), potassium bromite Halogenous acid such as (KBrO ₂ ) or a salt thereof; sodium chlorate (NaClO ₃ ), potassium chlorate (KClO ₃ ), silver chlorate (AgClO ₃ ), barium chlorate (Ba (ClO ₃ ) ₂ ), bromine sodium acid (NaBrO _3), potassium bromate (KBrO _3), or halogen acids such as sodium periodate (NaIO ₃₎ Salt; perchlorate (HClO _4), perbromic acid (HBrO _4), periodic acid _(HIO 4), sodium periodate (NaIO _4), potassium periodate _(KIO 4), periodic acid tetrabutyl Perhalogen acids such as ammonium ((C ₄ H ₉ ) ₄ NIO ₄ ) or salts thereof; hypofluorite (HFO), hypochlorous acid (HClO), hypobromite (HBrO), hypoiodite ( Hypohalous acid such as HIO); lithium hypofluorite (LiFO), sodium hypofluorite (NaFO), potassium hypofluorite (KFO), magnesium hypofluorite (Mg (FO) ₂ ), calcium nitrite fluorine acid (Ca _{(FO) 2),} barium hypofluorite (Ba _{(FO) 2)} salt of hypophosphorous fluorine acid and the like; lithium hypochlorite (LiClO), hypochlorite sodium Beam (NaClO), potassium hypochlorite (KClO), magnesium hypochlorite (Mg _{(ClO) 2),} calcium hypochlorite (Ca _{(ClO) 2),} barium hypochlorite (Ba (ClO) ₂ ), t-butyl hypochlorite (t-BuClO), ammonium hypochlorite (NH ₄ ClO), triethanolamine hypochlorite ((CH ₂ CH ₂ OH) ₃ N · ClO), etc. Salts of chlorous acid; lithium hypobromite (LiBrO), sodium hypobromite (NaBrO), potassium hypobromite (KBrO), magnesium hypobromite (Mg (BrO) ₂ ), hypobromite Calcium (Ca (BrO) ₂ ), barium hypobromite (Ba (BrO) ₂ ), ammonium hypobromite (NH ₄ BrO), triethanolamine hypobromite ((CH ₂ Salts of hypobromite such as CH ₂ OH) ₃ N · BrO); lithium hypoiodite (LiIO), sodium hypoiodite (NaIO), potassium hypoiodite (KIO), magnesium hypoiodite (Mg (IO) ₂ ), calcium hypoiodite (Ca (IO) ₂ ), barium hypoiodite (Ba (IO) ₂ ), ammonium hypoiodite (NH ₄ IO), trihypohydousite Examples thereof include hypoiodic acid salts such as ethanolamine ((CH ₂ CH ₂ OH) ₃ N · IO). These oxidizing agents can be used alone or in combination of two or more.

  Among these oxidizing agents, hydrogen peroxide or sodium hypochlorite is preferable from the viewpoint of obtaining good bulge resolution.

  In the case of a polishing composition used for polishing an object to be polished as it is as a polishing liquid, the content of the oxidizing agent at the time of use is preferably 0.0001% by mass or more with respect to the polishing composition. More preferably, it is 0.001 mass% or more. As the oxidizer content increases, the Si oxidation of the hard laser mark periphery and the silicon wafer part tends to proceed, so if the oxidizer content is above the above range, the difference between both polishing rates will be reduced. It can be reduced sufficiently. In addition, the content of the oxidizing agent during use is usually suitably 0.5% by mass or less, more preferably 0.05% by mass or less, and particularly preferably 0.01% by mass or less. . When content of an oxidizing agent is below the said range, the fall of a grinding | polishing rate is suppressed.

  Further, in the case of a polishing composition (ie, a concentrated solution) that is diluted and used for polishing, the content of the oxidizing agent is usually 1% by mass or less from the viewpoint of storage stability, filterability, and the like. It is appropriate, more preferably 0.5% by mass or less, and particularly preferably 0.1% by mass or less. Further, from the viewpoint of taking advantage of the concentrated liquid, the content of the oxidizing agent is preferably 0.001% by mass or more, more preferably 0.01% by mass or more. Moreover, when using in combination of 2 or more types of oxidizing agents, the said content points out the total content of 2 or more types of oxidizing agents.

<Basic compound>
The polishing composition according to the present invention contains a basic compound. Here, the basic compound refers to a compound having a function of increasing the pH of the composition when added to the polishing composition. The basic compound serves to chemically polish the surface to be polished, and can contribute to an improvement in the polishing rate. In addition, the basic compound can be useful for improving the dispersion stability of the polishing composition.

  As the basic compound, an organic or inorganic basic compound containing nitrogen, an alkali metal or alkaline earth metal hydroxide, various carbonates, bicarbonates, or the like can be used. For example, alkali metal hydroxide, quaternary ammonium hydroxide or a salt thereof, ammonia, amine and the like can be mentioned. Specific examples of the alkali metal hydroxide include potassium hydroxide and sodium hydroxide. Specific examples of the carbonate or bicarbonate include ammonium bicarbonate, ammonium carbonate, potassium bicarbonate, potassium carbonate, sodium bicarbonate, sodium carbonate and the like. Specific examples of the quaternary ammonium hydroxide or a salt thereof include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide and the like. Specific examples of amines include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N- (β-aminoethyl) ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, anhydrous piperazine , Piperazine hexahydrate, 1- (2-aminoethyl) piperazine, N-methylpiperazine, guanidine, azoles such as imidazole and triazole, and the like.

  Preferred basic compounds from the viewpoint of improving the polishing rate include ammonia, potassium hydroxide, sodium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, ammonium hydrogen carbonate, ammonium carbonate, potassium hydrogen carbonate, potassium carbonate, hydrogen carbonate. Sodium and sodium carbonate are mentioned. Of these, ammonia, potassium hydroxide, sodium hydroxide, tetramethylammonium hydroxide, and tetraethylammonium hydroxide are more preferable. More preferred are potassium carbonate and tetramethylammonium hydroxide. Such basic compounds can be used singly or in combination of two or more. When using 2 or more types in combination, for example, a combination of potassium carbonate and tetramethylammonium hydroxide is preferable.

  In the case of a polishing composition that is used as it is as a polishing liquid for polishing an object to be polished, the content of the basic compound in use with respect to the polishing composition is preferably 0 from the viewpoint of promoting the polishing rate. It is 0.01 mass% or more, More preferably, it is 0.05 mass% or more, More preferably, it is 0.09 mass% or more. Stability can also be improved by increasing the content of the basic compound. The upper limit of the content of the basic compound during use is suitably 1% by mass or less, and preferably 0.5% by mass or less from the viewpoint of surface quality and the like. Moreover, when using 2 or more types in combination, the said content refers to the total content of 2 or more types of basic compounds.

  In the case of a polishing composition (ie, concentrated solution) that is diluted and used for polishing, the content of the basic compound is usually 10% by mass or less from the viewpoint of storage stability, filterability, and the like. Is suitable, and it is more preferable that it is 5 mass% or less. Further, from the viewpoint of taking advantage of the concentrated liquid, the content of the basic compound is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and further preferably 0.9% by mass or more. It is.

<Other ingredients>
The polishing composition according to the present invention is a polishing composition such as a chelating agent, a water-soluble polymer, a surfactant, an antiseptic, or an antifungal agent (typically) within a range that does not significantly impair the effects of the present invention. Specifically, a known additive that can be used in a polishing composition used in a polishing process of a silicon wafer may be further contained as necessary.

  Examples of chelating agents that can be included in the polishing composition include aminocarboxylic acid chelating agents and organic phosphonic acid chelating agents. Examples of aminocarboxylic acid chelating agents include ethylenediaminetetraacetic acid, ethylenediaminetetraacetic acid sodium, nitrilotriacetic acid, nitrilotriacetic acid sodium, nitrilotriacetic acid ammonium, hydroxyethylethylenediaminetriacetic acid, hydroxyethylethylenediamine sodium triacetate, diethylenetriaminepentaacetic acid Diethylenetriamine sodium pentaacetate, triethylenetetramine hexaacetic acid and sodium triethylenetetramine hexaacetate. Examples of organic phosphonic acid chelating agents include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid), ethylenediaminetetrakis (methylenephosphonic acid), diethylenetriaminepenta (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-methylphospho Nosuccinic acid is included. Of these, organic phosphonic acid chelating agents are more preferred. Of these, ethylenediaminetetrakis (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid) and diethylenetriaminepentaacetic acid are preferable. Particularly preferred chelating agents include ethylenediaminetetrakis (methylenephosphonic acid) and diethylenetriaminepenta (methylenephosphonic acid). A chelating agent can be used individually by 1 type or in combination of 2 or more types.

  In the case of a polishing composition that is used as it is as a polishing liquid for polishing an object to be polished, the content of the chelating agent in use with respect to the polishing composition is preferably 0.0001% by mass or more, more preferably It is 0.001 mass% or more, More preferably, it is 0.005 mass% or more. The upper limit of the content of the chelating agent in use is preferably 1% by mass or less, more preferably 0.5% by mass or less, further preferably 0.3% by mass or less, It is particularly preferably 15% by mass or less.

  In the case of a polishing composition (ie, a concentrated solution) that is diluted and used for polishing, the content of the chelating agent is usually 5% by mass or less from the viewpoint of storage stability, filterability, and the like. It is suitable, it is more preferable that it is 3 mass% or less, and it is especially preferable that it is 1.5 mass% or less. Further, from the viewpoint of taking advantage of the concentrated liquid, the content of the chelating agent is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and further preferably 0.05% by mass or more. is there.

  Examples of antiseptics and fungicides that can be included in the polishing composition if necessary include 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one. And the like, isothiazoline-based preservatives such as paraoxybenzoates, and phenoxyethanol. These antiseptics and fungicides may be used alone or in combination of two or more.

<Polishing composition>
The polishing composition according to the present invention is typically supplied to a polishing object in the form of a polishing liquid containing the polishing composition, and used for polishing the polishing object. The polishing composition according to the present invention may be used, for example, as a polishing liquid after being diluted (typically diluted with water), or may be used as a polishing liquid as it is. Good. That is, the concept of the polishing composition in the technology according to the present invention is used for polishing by being diluted with a polishing composition (working slurry) that is supplied to the polishing object and used for polishing the polishing object. Both concentrates (working slurry stock solutions) are included. The concentration ratio of the concentrated liquid can be, for example, about 2 to 100 times on a volume basis, and usually about 5 to 50 times is appropriate.

  In the case of a polishing composition that is used as it is as a polishing liquid for polishing an object to be polished, the pH of the polishing composition is 9.0 or more, preferably 9.5 or more, more preferably 10.0 or more, Preferably it is 10.2 or more, for example 10.5 or more. When the pH of the polishing liquid is less than 9.0, there is a tendency that the bulge eliminating property cannot be sufficiently obtained. On the other hand, the pH of the polishing liquid is 12.0 or less, preferably 11.8 or less, and more preferably 11.5 or less. When the pH of the polishing liquid exceeds 12.0, dissolution of the abrasive grains occurs, and the mechanical polishing action by the abrasive grains may be reduced.

  Further, in the case of a polishing composition (that is, a concentrated liquid) diluted and used for polishing, the pH of the polishing composition is 9.5 or higher, preferably 10.0 or higher, more preferably 10.2 or higher. It is. The pH of the polishing composition is suitably 12.0 or less, and preferably 11.5 or less.

  In addition, pH of polishing composition uses the pH meter (For example, the glass electrode type hydrogen ion concentration indicator (model number F-23) by Horiba, Ltd.), standard buffer (phthalate pH buffer solution pH: 4.01 (25 ° C), neutral phosphate pH buffer pH: 6.86 (25 ° C), carbonate pH buffer pH: 10.01 (25 ° C)) It can be grasped by putting the glass electrode into the polishing composition and measuring the value after 2 minutes or more has been stabilized.

<Method for producing polishing composition>
The manufacturing method of the polishing composition which concerns on this invention is not specifically limited. For example, it can be obtained by stirring and mixing abrasive grains, an oxidizing agent, a basic compound, and other additives as required. From the viewpoint of the storage stability of the oxidizing agent, the abrasive grains, the basic compound and other additives as necessary are stirred and mixed in water to obtain a mixture, and then the oxidizing agent is added to the mixture immediately before polishing. Then, a method for producing a polishing composition by mixing them is preferred.

  That is, a method for producing a polishing composition according to a preferred embodiment of the present invention includes a step of mixing abrasive grains and a basic compound in water to obtain a mixture, and an oxidizing agent is added to the mixture immediately before polishing. And mixing.

  Here, the term “immediately before polishing” means that polishing is performed as soon as possible after mixing the oxidizer. Specifically, it means within 180 minutes before polishing, and within 60 minutes before polishing. Preferably, it is within 30 minutes before polishing, and particularly preferably within 10 minutes before polishing.

  The temperature at the time of mixing in the step of obtaining the above mixture and the step of adding and mixing the oxidizing agent is not particularly limited, but is preferably 10 to 40 ° C. and may be heated to increase the dissolution rate. Further, the mixing time is not particularly limited as long as uniform mixing can be performed. As the stirring device, for example, a well-known mixing device such as a blade-type stirrer, an ultrasonic disperser, or a homomixer is used. The aspect which mixes these components is not specifically limited, For example, all the components may be mixed at once and may be mixed in the order set suitably.

<Polishing method>
The polishing composition according to the present invention can be used for polishing a polishing object, for example, in an embodiment including the following operations.

  That is, a working slurry containing the polishing composition according to the present invention is prepared. Next, the polishing composition is supplied to the object to be polished and polished by a conventional method. For example, a polishing object is set in a general polishing apparatus, and the polishing composition is supplied to the surface (polishing object surface) of the polishing object through a 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 both are relatively moved (for example, rotated). The polishing of the object to be polished is completed through this polishing step.

  The polishing pad used in the polishing step is not particularly limited. For example, any of polyurethane foam type, non-woven fabric type, suede type, those containing abrasive grains, and those not containing abrasive grains may be used. Further, as the polishing apparatus, a double-side polishing apparatus that simultaneously polishes both surfaces of an object to be polished, or a single-side polishing apparatus that polishes only one surface of the object to be polished may be used.

  Once used for polishing, the polishing composition may be used in a disposable form (so-called “flowing”), or may be used repeatedly in circulation. As an example of a method of circulating and using the polishing composition, there is a method of collecting a used polishing composition discharged from the polishing apparatus in a tank and supplying the recovered polishing composition to the polishing apparatus again. . When the polishing composition is used in a circulating manner, the environmental load can be reduced by reducing the amount of the used polishing composition to be treated as a waste liquid, compared with the case of using the polishing composition by pouring. Moreover, cost can be suppressed by reducing the usage-amount of polishing composition.

<Application>
The polishing composition according to the present invention is excellent in the performance (uplift-removing property) for eliminating the uplift of the peripheral edge of the hard laser mark. Taking advantage of such features, the polishing composition can be preferably applied to polishing a polishing object including a surface with a hard laser mark. Examples of the polishing object include a substrate on which an inorganic insulating film such as a silicon oxide film and a silicon nitride film is formed, a substrate on which a polycrystalline silicon film is formed, a silicon single crystal substrate (silicon wafer), and the like. . Of these, a silicon wafer is preferable. That is, the polishing composition according to the present invention is suitable as a polishing composition used in a preliminary polishing step of a silicon wafer having a hard laser mark. It is desirable to eliminate the bulge around the hard laser mark at the beginning of the polishing process. For this reason, the polishing composition according to the present invention can be particularly preferably used in the first polishing step (primary polishing step) after applying the hard laser mark. The first polishing step is typically performed as a double-side polishing step in which both sides of a silicon wafer are simultaneously polished. The polishing composition according to the present invention can be preferably used in such a double-side polishing step.

  Therefore, the present invention also provides a silicon wafer having a hard laser mark using a polishing composition containing abrasive grains, a basic compound, water, and an oxidizing agent and having a pH of 9 to 12. A method for improving the flatness of the film is also provided.

  The polishing composition according to the present invention can also be used for polishing a surface to be polished that does not have a hard laser mark. For example, the present invention can be preferably applied to preliminary polishing of a lapped silicon wafer regardless of the presence or absence of a hard laser mark.

  The present invention will be described in further detail using the following examples and comparative examples. However, the technical scope of the present invention is not limited only to the following examples. Unless otherwise specified, “%” and “part” mean “% by mass” and “part by mass”, respectively. In the following examples, unless otherwise specified, the operation was performed under conditions of room temperature (25 ° C.) / Relative humidity 40 to 50% RH.

<Preparation of polishing composition>
(Polishing composition A1)
The content of colloidal silica (average primary particle size 55 nm) is 9% by mass, the content of potassium carbonate (K ₂ CO ₃ ) is 1.7% by mass, and the content of tetramethylammonium hydroxide (TMAH) is 2.5%. The components and ion-exchanged water were stirred and mixed at about room temperature (25 ° C.) for about 30 minutes so that the content of ethylenediaminetetrakis (methylenephosphonic acid) (EDTPO) was 0.1% by mass. Subsequently, these were diluted 10 times with water, and hydrogen peroxide was added so that the content was 0.003% by mass immediately before polishing, thereby preparing a polishing composition A1.

(Polishing composition A2, Polishing composition A3)
Polishing composition A2 and polishing composition A3 were prepared in the same manner as the polishing composition A1, except that the content of the oxidizing agent was changed as shown in Table 1.

(Polishing composition A4, Polishing composition A5, Polishing composition C1)
Polishing composition A4 and polishing composition A5 were prepared in the same manner as the polishing composition A1, except that the type and content of the oxidizing agent were changed as shown in Table 1. A polishing composition C1 was prepared in the same manner as the polishing composition A1, except that no oxidizing agent was used.

<Polishing of silicon wafer>
Each polishing composition was used as a polishing liquid (working slurry), and the surface of a polishing object (test piece) was polished under the following conditions to obtain Examples 1 to 5 and Comparative Example 1. As a test piece, a commercially available silicon etched wafer (Bare Si P- <100>, thickness: 545 μm) having a diameter of 4 inches (100 mm) after lapping was used. On this wafer, a hard laser mark based on the SEMI M1 (T7) standard is imprinted on the polished surface.

(Polishing conditions)
Polishing apparatus: Nippon Engis Co., Ltd. single-side polishing machine, model “EJ-380IN”
Polishing pressure: 12.0kPa
Slurry flow rate: 100 ml / min
Plate rotation speed: 50 rpm
Head rotation speed: 40rpm
Polishing amount: 5 μm
Polishing pad: Nitta Haas Co., Ltd., trade name “MH-S15A”
Polishing environment temperature: 20 ° C
Polishing time: adjusted to a polishing time of 4 μm for each level.
About the silicon wafer after grinding | polishing, the height of the protrusion was measured using SURFCOM 1500DX (made by Tokyo Seimitsu Co., Ltd.), and the protrusion elimination property was evaluated. Specifically, the needle was run directly on the peripheral edge of the silicon wafer, and the level difference (projection height) from the portion without protrusion was calculated. The larger the protrusion height is, the lower the bulge resolution is. The results obtained by the above measurement are shown in Table 1.

<Polishing efficiency>
Table 1 below shows the polishing efficiency obtained by performing polishing for 20 minutes using the polishing liquids of each Example and Comparative Example, measuring the weight of the object to be polished before and after polishing, and calculating from the difference in weight before and after polishing. Indicated.

  As Table 1 showed, according to the polishing composition of Examples 1-5, all showed the favorable ridge elimination property. On the other hand, Comparative Example 1 to which no oxidizing agent was added was inferior to the bulge eliminating property as compared with the Examples. This is because when the oxidizer is included, both the altered portion of the hard laser mark periphery and the surface of the silicon wafer are changed to Si oxide films, so the difference in polishing efficiency between the two is small, and thus the difference in height between the two is small. It is thought. On the other hand, in the case of the comparative example 1 which does not contain an oxidizing agent, the polishing rate of the silicon wafer is higher than the polishing rate of the denatured portion at the periphery of the hard laser mark, and it is considered that the difference in height between the two is widened.

  Specific examples of the present invention have been described in detail above, but these are merely examples 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 (8)

  A polishing composition comprising abrasive grains, a basic compound, water, and an oxidizing agent, and having a pH of 9 to 12.   The polishing composition according to claim 1, wherein the oxidizing agent is hydrogen peroxide.   The polishing composition according to claim 1, wherein the oxidizing agent is sodium hypochlorite.   Polishing composition of any one of Claims 1-3 whose content of the said oxidizing agent at the time of use is 0.0001 mass% or more and 0.5 mass% or less.   Polishing composition of any one of Claims 1-4 whose content of the said abrasive grain at the time of use is 0.01 mass% or more and 10 mass% or less.   Polishing composition of any one of Claims 1-5 whose average primary particle diameter of the said abrasive grain is 10-200 nm.   The polishing composition according to any one of claims 1 to 6, further comprising a chelating agent. A step of mixing abrasive grains and a basic compound in water to obtain a mixture, and a step of adding an oxidizer to the mixture immediately before polishing and mixing the mixture,
The manufacturing method of polishing composition containing this.