WO2021200149A1

WO2021200149A1 - Polishing composition and polishing method

Info

Publication number: WO2021200149A1
Application number: PCT/JP2021/010796
Authority: WO
Inventors: 高見　信一郎
Original assignee: 株式会社フジミインコーポレーテッド
Priority date: 2020-03-30
Filing date: 2021-03-17
Publication date: 2021-10-07
Also published as: JPWO2021200149A1; TW202145332A

Abstract

The present invention provides a polishing composition including fumed silica, an oxidizing agent, and a metal salt. The polishing composition includes more than 10 mmol/L of the metal salt.

Description

Polishing composition and polishing method

The present invention relates to a polishing composition and a polishing method. More specifically, the present invention relates to a polishing composition and a polishing method suitable for polishing a high-hardness material having a Vickers hardness of 1500 Hv or more. This application claims priority based on Japanese Patent Application No. 2020-060913 filed on March 30, 2020, the entire contents of which are incorporated herein by reference.

The surface of materials such as metals, metalloids, non-metals, and oxides thereof is polished using a polishing composition. For example, a surface made of a compound semiconductor material such as silicon carbide, boron carbide, tungsten carbide, silicon nitride, titanium nitride, and gallium nitride is wrapped by supplying diamond abrasive grains between the surface and the polishing platen. Can be processed by. However, in wrapping using diamond abrasive grains, defects and distortions due to scratches, dents, residues, etc. are likely to occur. Therefore, polishing (polishing) using a polishing pad and a polishing composition after or instead of wrapping with diamond abrasive grains has been studied. Patent Document 1 is mentioned as a document that discloses the prior art of the polishing composition. In Patent Document 1, a composition for polishing tantalum is studied.

Japanese Patent Application Publication No. 2011-159998

In general, from the viewpoint of manufacturing efficiency and cost effectiveness, it is desirable that the polishing removal speed is sufficiently high for practical use. For example, in polishing a surface made of a high-hardness material such as silicon carbide, further improvement in polishing removal speed is desired. Examples of the polishing composition that can be expected to improve the polishing removal speed include a polishing composition containing fumed silica. Since fumed silica is more non-spherical than colloidal silica, it tends to have excellent processing power, but it is preferable because it is less likely to cause a problem of alumina residue (piercing or the like) on a polished surface such as alumina abrasive grains. Further, when the polishing composition contains an oxidizing agent, the oxidizing agent may change the surface of the substrate, and the polishing removal rate may be improved.

The present invention has been made in view of such circumstances, and an object of the present invention is to improve the polishing removal rate of a composition containing fumed silica and an oxidizing agent.

According to this specification, a polishing composition containing fumed silica, an oxidizing agent, and a metal salt is provided. This polishing composition is characterized by containing more than 10 mmol / L of metal salts. When the polishing composition contains more than 10 mmol / L of the metal salt, the polishing removal rate is improved in the composition containing fumed silica and an oxidizing agent. As will be described in detail later, the "metal salt" in the present specification is defined as a compound different from the above "oxidizing agent", and specifically, it is produced by neutralization of a strong acid and a strong base. Can be pure salt. The metal forming the metal salt includes lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium or barium.

In some preferred embodiments of the techniques disclosed herein (including polishing compositions, polishing methods, substrate manufacturing methods; the same shall apply hereinafter), the metal salt is a nitrate of an alkali metal and / or an alkaline earth metal. And / or hydrochloride. By using the above metal salt, the polishing removal rate is preferably improved.

In some preferred embodiments, the metal forming the metal salt is calcium. When the metal is calcium, the polishing removal rate is particularly preferably improved.

In some preferred embodiments, the metal forming the metal salt is potassium. When the metal is potassium, the polishing removal rate is particularly preferably improved.

In some preferred embodiments, the oxidizing agent comprises a composite metal oxide. When the composition containing the composite metal oxide as an oxidizing agent contains a metal salt in an amount of more than 10 mmol / L, the polishing removal rate can be easily improved.

In some preferred embodiments, the ratio (B / A) of the metal salt concentration B [mmol / L] to the oxidizing agent concentration A [mmol / L] is 0.01 or more and 10 or less. According to such a configuration, the effect of the technique disclosed herein is preferably exhibited.

In some preferred embodiments, the pH of the polishing composition is greater than 5.0 and less than 9.0. When the pH of the polishing composition is in the above range (a range close to the neutral range), the effects of the techniques disclosed herein are preferably exhibited.

The polishing composition disclosed herein is preferably used for polishing a material having a Vickers hardness of 1500 Hv or more. According to the above-mentioned polishing composition, the polishing removal rate for a high-hardness material can be improved. A preferable example of the high hardness material is silicon carbide. When polishing silicon carbide, the effects of the techniques disclosed herein are preferably exhibited.

According to this specification, a method for polishing a substrate is further provided. The polishing method includes a step of polishing a substrate using any of the polishing compositions disclosed herein. According to this polishing method, the polishing removal speed is improved.

Hereinafter, preferred embodiments of the present invention will be described. Matters other than those specifically mentioned in the present specification and necessary for carrying out the present invention can be grasped as design matters of those skilled in the art based on the prior art in the art. The present invention can be carried out based on the contents disclosed in the present specification and common general technical knowledge in the art.

<Polishing composition>
(Fumed silica)
The polishing composition disclosed herein comprises fumed silica. As the fumed silica, it can be appropriately selected and used from various known fumed silicas. The fumed silica may contain one of various known fumed silicas alone or in combination of two or more.

The average primary particle size of fumed silica is not particularly limited as long as the effect of the present invention is exhibited, and is preferably 10 nm or more, more preferably 15 nm or more, still more preferably 20 nm or more from the viewpoint of improving the polishing removal speed and the like. For example, it may be 30 nm or more. Higher polishing removal rates can be achieved by increasing the average primary particle size. From the viewpoint of surface quality after polishing, the average primary particle size is preferably 150 nm or less, more preferably 100 nm or less, still more preferably 80 nm or less, and may be, for example, 60 nm or less.

In the technique disclosed herein, the average primary particle size is the average primary particle size (nm) = 6000 / (true density (g / cm ³ ) × from the specific surface area (BET value) measured by the BET method. BET value (m ² / g)) means the particle size (BET particle size) calculated by the formula. The specific surface area can be measured, for example, by using a surface area measuring device manufactured by Micromeritex Co., Ltd., trade name "Flow Sorb II 2300".

The average secondary particle size of fumed silica is not particularly limited as long as the effect of the present invention is exhibited, for example, 15 nm or more is suitable, and from the viewpoint of improving the polishing removal speed, it is preferably 30 nm or more, more preferably. Is 60 nm or more, more preferably 80 nm or more, particularly preferably 100 nm or more (for example, 120 nm or more), and may be 150 nm or more. The average secondary particle size of the fumed silica can be, for example, 1000 nm or less. From the viewpoint of surface quality after polishing, the average secondary particle size is preferably 500 nm or less, and may be 300 nm or less. For example, fumed silica having an average secondary particle size of 120 nm or more and 220 nm or less can be preferably adopted.

In the technique disclosed herein, the average secondary particle size of fumed silica means the volume-based average particle size (50% volume average particle size) based on the dynamic light scattering method. The particle size measurement based on the dynamic light scattering method can be performed using, for example, "N4 Plus" manufactured by BECKMAN COULTER.

The aspect ratio of fumed silica is not particularly limited and may be, for example, 1.5 or more. From the viewpoint of improving the polishing removal speed, the aspect ratio of the fumed silica may be 2.0 or more, 2.5 or more, or 3.0 or more. Further, the upper limit of the aspect ratio is, for example, less than 8.0, and may be less than 6.0. In this specification, the "aspect ratio" of the fumed silica means the value of the ratio of the average secondary particle size / the average primary particle size of the fumed silica.

The content of fumed silica in the polishing composition (when a plurality of types of fumed silica are contained, the total content thereof) is not particularly limited as long as the effects of the present invention are exhibited, and for example, 0. It is 01% by weight or more, and may be 0.05% by weight or more. From the viewpoint of improving the polishing speed, it is appropriate to be 0.1% by weight or more, preferably 0.5% by weight or more, more preferably 0.8% by weight or more, and may be 1% by weight or more, 5% by weight. The above may be sufficient. Further, from the viewpoint of dispersibility of the polishing composition, stability over time, etc., the content of fumed silica is preferably 50% by weight or less, preferably 20% by weight or less, and 15% by weight. It may be 10% by weight or less, 8% by weight or less, 3% by weight or less, 1.5% by weight or less, for example, 0.3% by weight or less.

The polishing composition disclosed herein may contain silica abrasive grains other than fumed silica (hereinafter, also referred to as non-fumed silica abrasive grains) as long as the effects of the present invention are not impaired. Abrasive grains made of a material other than the above (hereinafter, also referred to as non-silica abrasive grains) may be contained. Examples of non-fumed silica abrasive grains include colloidal silica and precipitated silica. Examples of non-silica abrasive grains include oxide particles such as aluminum oxide particles, cerium oxide particles, chromium oxide particles, titanium dioxide particles, zirconium oxide particles, magnesium oxide particles, manganese oxide particles, zinc oxide particles, and 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; inorganic particles such as carbonates such as calcium carbonate and barium carbonate, and crosslinked or non-crosslinked polymethacryl Examples thereof include abrasive grains substantially composed of any of organic particles such as methyl acid, polyacrylonitrile, polystyrene, nylon and silicone.

It is generally advantageous that the ratio of fumed silica to the total abrasive grains used is high. For example, the proportion of fumed silica in the entire abrasive grains is preferably more than 50% by weight, preferably 70% by weight or more, more preferably 90% by weight or more, still more preferably 95% by weight or more, and is substantially. It may be 100% by weight.

In some embodiments, the polishing composition may be substantially free of diamond particles as abrasive grains. Since diamond particles have high hardness, they can be a limiting factor for improving smoothness. Moreover, since diamond particles are generally expensive, they cannot be said to be advantageous materials in terms of cost effectiveness, and from a practical point of view, the dependence on high-priced materials such as diamond particles may be low. Here, the fact that the abrasive grains do not substantially contain diamond particles means that the ratio of the diamond particles to the total abrasive grains is 1% by weight or less, more preferably 0.5% by weight or less, typically 0.1% by weight. % Or less, including the case where the ratio of diamond particles is 0% by weight. In such an embodiment, the effects of the techniques disclosed herein can be suitably exerted.

(Oxidant)
The polishing composition disclosed herein comprises an oxidizing agent. The oxidant can cause an oxidation reaction with the surface of the substrate during the polishing process to reduce the hardness of the surface and make the surface fragile. By using an oxidizing agent, the polishing removal rate can be effectively improved. The oxidizing agent is not particularly limited as long as it is a substance having a sufficient redox potential to exert an action of oxidizing the surface of the substrate. For example, the oxidizing agent can be a substance having a redox potential higher than the redox potential of the substrate material at the pH at which polishing is performed. Here, the pH at which the polishing is carried out is usually the same as the pH of the polishing composition. The redox potential of the substrate material is determined by dispersing the powder of the material in water to make a slurry, adjusting the slurry to the same pH as the polishing composition, and then using a commercially available redox potential meter to prepare the slurry. The value obtained by measuring the redox potential (oxidation-reduction potential with respect to the standard hydrogen electrode at a liquid temperature of 25 ° C.) is adopted. The oxidizing agent in the present specification does not include the metal salt described later.

Specific examples of the oxidizing agent include peroxides such as hydrogen peroxide; nitrates such as iron nitrate, silver nitrate and aluminum nitrate; persulfates such as persulfates such as peroxomonosulfate and peroxodisulfate; persulfates such as chloric acid and the like. Chloric acids; Perchloric acids such as perchloric acid; Bromic acids such as bromic acid; Iodic acids such as iodic acid; Perioic acids; Iron acids such as potassium iron acid; Manganic acids; Chromic acids such as potassium chromate and potassium dichromate; Vanazic acids such as ammonium vanadate, sodium vanadate and potassium vanadate; Luthenic acids such as perlutenic acid or salts thereof; Molybdic acid and salts thereof. Examples thereof include molybdenum acids such as ammonium molybdenum and disodium molybdenate; renic acids such as perlenic acid or salts thereof; tungonic acids such as disodium tungstate which is a salt thereof. One of these may be used alone, or two or more thereof may be used in combination as appropriate.

In some preferred embodiments, the polishing composition comprises a composite metal oxide as an oxidizing agent. Examples of the composite metal oxide include nitric acids, iron acids, permanganic acids, chromium acids, vanadic acids, ruthenic acids, molybdic acids, renic acids and tungsten acids. Among them, iron acids, permanganates and chromium acids are more preferable, and permanganates are even more preferable. One type of composite metal oxide may be used alone, or two or more types may be used in combination as appropriate.

The polishing composition disclosed here may or may not further contain an oxidizing agent other than the above-mentioned composite metal oxide. The technique disclosed herein can be preferably carried out in a manner in which an oxidizing agent (for example, hydrogen peroxide) other than the above-mentioned composite metal oxide is substantially not contained as an oxidizing agent.

It is appropriate that the concentration (content) of the oxidizing agent in the polishing composition is 0.001 mol / L or more. From the viewpoint of improving the polishing removal rate, in some embodiments, the concentration of the oxidizing agent is preferably 0.005 mol / L or more, more preferably 0.01 mol / L or more, and 0.05 mol / L or more. The above is more preferable. In some preferred embodiments, the concentration of oxidant is 0.10 mol / L or higher, may be 0.15 mol / L or higher, may be 0.20 mol / L or higher, eg, 0.25 mol / L or higher. Molar / L or more. From the viewpoint of surface quality after polishing, the concentration of the oxidizing agent is preferably 10 mol / L or less, preferably 5 mol / L or less, and 3 mol / L or less (for example, 1). It is more preferably mol / L or less, or 0.5 mol / L or less). In some embodiments, the concentration of oxidant may be 0.30 mol / L or less, 0.20 mol / L or less, 0.12 mol / L or less, 0.09 mol / L or less. It may be L or less.

The content of the oxidant can also be specified by the relative relationship with the abrasive grains (typically fumed silica). Although not particularly limited, in some embodiments, the content of the oxidizing agent with respect to 100 parts by weight of the abrasive grains can be, for example, 0.01 mol or more, and the effect of using the oxidizing agent is effectively exhibited. From the viewpoint, it is appropriate to set it to 0.05 mol or more, and it may be 0.10 mol or more, 0.5 mol or more, 1 mol or more, 2.5 mol or more, and 5 mol. The above may be sufficient. The content of the oxidizing agent with respect to 100 parts by weight of the abrasive grains can be, for example, 50 mol or less (for example, 30 mol or less), and 10 mol or less from the viewpoint of effectively exerting the mechanical polishing force of the abrasive grains. It may be 6 mol or less, 3 mol or less, 1 mol or less, 0.3 mol or less (for example, 0.1 mol or less).

(Metal salt)
The polishing composition disclosed herein comprises a metal salt. By containing a predetermined amount or more of the metal salt, the polishing removal rate is improved. Specifically, the oxidizing agent contained in the polishing composition disclosed herein alters the surface of the substrate (particularly the surface of the substrate of a high-hardness material such as silicon carbide), and the altered layer is removed by polishing. .. The metal salt exhibits an action of promoting or assisting its alteration and removal, and is considered to contribute to the improvement of the polishing removal rate. It should be noted that the improvement in polishing removal speed by the technique disclosed herein is not limited to the above mechanism. The "metal salt" disclosed herein is a compound different from the above-mentioned "oxidizing agent", and specifically, it may be a positive salt produced by neutralization of a strong acid and a strong base. The metal salt preferably contains an element belonging to an alkali metal and / or an alkaline earth metal, and is preferably lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), or magnesium. More preferably, it contains any one or more of (Mg), calcium (Ca), cesium (Sr), and barium (Ba). Among them, a metal salt containing any one of Na, K, Ca and Sr is preferable, and a metal salt containing any one of K and Ca is particularly preferable.

The type of salt in the above metal salt is not particularly limited, and may be an inorganic acid salt or an organic acid salt. For example, examples of the inorganic acid salt include salts of hydrohalic acid (for example, hydrochloric acid, hydrobromic acid, hydrofluoric acid), nitric acid, sulfuric acid, carbonic acid, silicic acid, boric acid, phosphoric acid and the like. Examples of the organic acid salt include carboxylic acids (for example, formic acid, acetic acid, propionic acid, benzoic acid, glycic acid, butyric acid, citric acid, tartaric acid, and trifluoroacetic acid) and organic sulfonic acids (for example, methanesulfonic acid and trifluoromethane). Examples thereof include salts of sulfonic acid, benzenesulfonic acid, toluenesulfonic acid), organic phosphonic acid (eg, methylphosphonic acid, benzenephosphonic acid, toluenephosphonic acid), organic phosphoric acid (eg, ethylphosphoric acid) and the like. Of these, inorganic acid salts are preferable, hydrochlorides and nitrates are more preferable, and nitrates are particularly preferably used.

Specific examples of the metal salt include chlorides such as lithium chloride, sodium chloride, potassium chloride, magnesium chloride, calcium chloride, strontium chloride and barium chloride; sodium bromide, potassium bromide, magnesium bromide, calcium bromide and the like. Bromide; fluorides such as lithium fluoride, sodium fluoride, potassium fluoride, magnesium fluoride, calcium fluoride, strontium fluoride, barium fluoride; lithium nitrate, sodium nitrate, potassium nitrate, magnesium nitrate, calcium nitrate, strontium nitrate , Nitrate such as barium nitrate; sulfates such as lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, strontium sulfate, barium sulfate; potassium carbonate, potassium hydrogencarbonate, sodium carbonate, sodium hydrogencarbonate, magnesium carbonate, carbonic acid Substantial from any of carbonates such as calcium, strontium carbonate, barium carbonate; carboxylates such as potassium acetate, sodium acetate, calcium acetate, strontium acetate, sodium benzoate, calcium benzoate, sodium citrate, calcium citrate; A metal salt composed of sodium can be mentioned. One type of metal salt may be used alone, or two or more types may be used in combination.

The metal salt may be dissolved in the polishing composition or may be dispersed as a solid. That is, the metal salt may be water-soluble or water-insoluble. Further, a part of the metal salt may be dissolved in the polishing composition, and the rest may be dispersed as a solid. In some preferred embodiments, the metal salt is a water-soluble salt. By using a water-soluble metal salt, a good surface with few defects such as scratches can be efficiently formed. In some preferred embodiments, the metal salt is a salt that dissolves in water and exhibits a neutral range, and can be specifically a normal salt produced by neutralization of a strong acid and a strong base. By using a metal salt in which the aqueous solution exhibits a neutral range (for example, pH 6 to 8, preferably pH 6.5 to 7.5), a high quality surface can be efficiently formed. Examples of the metal salt in which the aqueous solution is neutral include chlorides such as sodium chloride, potassium chloride, calcium chloride and strontium chloride, and nitrates such as sodium nitrate, potassium nitrate, calcium nitrate and strontium nitrate. Of these, potassium chloride, sodium chloride, calcium chloride, strontium chloride, potassium nitrate, calcium nitrate and strontium nitrate are preferable because they can efficiently form a good surface. Among them, potassium chloride, calcium chloride, potassium nitrate and calcium nitrate are particularly preferable.

In the polishing composition disclosed herein, the concentration (content) of the metal salt is more than 10 mmol / L. This improves the polishing removal rate in the composition containing the fumed silica and the oxidizing agent. In some embodiments, the concentration of the metal salt is preferably 12 mmol / L or higher, more preferably 20 mmol / L or higher, 30 mmol / L or higher, or 50 mmol / L or higher. In some other embodiments, the concentration of the metal salt is preferably 80 mmol / L or higher, preferably 150 mmol / L or higher, 250 mmol / L or higher, 500 mmol / L or higher. But it may be.

The upper limit of the concentration of the metal salt is not particularly limited, and it is appropriate to set it to 10 mol / L or less. When the concentration of the metal salt is in a predetermined range, the polishing removal rate on the surface of the substrate material (particularly the high hardness material) can be improved at a higher level. From the viewpoint of improving the polishing removal speed, the above concentration is preferably 5 mol / L or less, more preferably 3 mol / L or less, further preferably 1000 mmol / L or less, and even if it is 600 mmol / L or less. It may be 400 mmol / L or less, or 200 mmol / L or less. In some embodiments, the concentration of the metal salt may be 100 mmol / L or less, 70 mmol / L or less, or 25 mmol / L or less (eg, 20 mmol / L or less).

The concentration ratio of the oxidizing agent and the metal salt is not particularly limited as long as the effect of the present invention is exhibited. Estimating the effect of the present invention, it is considered preferable to set the amount of the metal salt in a predetermined range with respect to the amount of the oxidizing agent. From this point of view, the ratio (B / A) of the metal salt concentration B [mmol / L] to the oxidizing agent concentration A [mmol / L] is, for example, 0.01 or more from the viewpoint of improving the polishing removal speed. Yes, 0.05 or more is appropriate, 0.07 or more, or 0.10 or more (for example, 0.15 or more). In some embodiments, the ratio (B / A) may be 0.30 or higher, 1.0 or higher, or 3.0 or higher (eg 6.0 or higher). The upper limit of the ratio (B / A) is not particularly limited, and may be, for example, 15 or less. From the viewpoint of polishing removal speed, 10 or less is appropriate, preferably 5.0 or less, and more preferably. It is 1.0 or less, more preferably 0.50 or less (for example, 0.20 or less), and may be 0.12 or less.

(Dispersion medium)
The dispersion medium used in the polishing composition is not particularly limited as long as it can disperse fumed silica, an oxidizing agent and a metal salt. The dispersion medium in the present specification is a liquid (a liquid medium at 23 ° C.) generally referred to as a dispersion medium or a solvent, and includes those which can be a solvent for an oxidizing agent or a metal salt. Water is preferably used as the dispersion medium. As the water, for example, ion-exchanged water (deionized water), pure water, ultrapure water, distilled water and the like can be preferably used. 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. It is preferable that 90% by volume or more of the solvent contained in the polishing composition is water, and more preferably 95% by volume or more (typically 99 to 100% by volume) of water.

(PH)
It is appropriate that the pH of the polishing composition is about 2 to 12. When the pH is in the above range, a practical polishing removal rate is likely to be achieved when polishing the substrate. In some embodiments, the pH may be 2.5 or higher, 3.0 or higher, 4.0 or higher, 5.0 or higher, or 5.5 or higher. The upper limit of the pH is not particularly limited, and in some embodiments, the pH may be 12.0 or less, 10.0 or less, 9.0 or less, 8.0 or less, 7.5 or less. It may be less than or equal to, 7.0 or less, or 6.5 or less. In some preferred embodiments, the pH of the polishing composition is greater than 5.0 and less than 9.0, for example less than 8.0 or less than 7.0. When the pH is within the above range, a higher polishing removal rate can be achieved. Although not particularly limited, it is considered that both cations and anions in the metal salt contribute to the improvement of the polishing removal rate. Further, when the pH of the polishing composition is within the above range, there is an advantage that damage to the polishing apparatus is small, for example.

(Other ingredients)
The polishing composition disclosed herein is a chelating agent, a thickener, a dispersant, a surface protectant, a wetting agent, and a pH adjuster (organic acid, inorganic acid, basic) as long as the effects of the present invention are not impaired. Known that can be used in polishing compositions (for example, compositions for polishing high-hardness materials, preferably compositions for polishing silicon carbide substrates) such as compounds), surfactants, rust preventives, preservatives, and antifungal agents. Additives may be further included as needed. The content of the additive may be appropriately set according to the purpose of the addition and does not characterize the present invention, and thus detailed description thereof will be omitted.

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

The polishing composition disclosed here may be a one-dosage form or a multi-dosage form including a two-dosage form. For example, the liquid A containing a part of the constituent components of the polishing composition and the liquid B containing the remaining components are stored separately, and the liquid A and the liquid B are mixed when polishing the substrate. It may be configured to be used.

<Concentrate>
The polishing composition disclosed herein may be in a concentrated form (ie, in the form of a concentrated solution of a polishing solution) before being used for polishing. The polishing composition in such a concentrated form is advantageous from the viewpoint of convenience and cost reduction in production, distribution, storage and the like.

<Board>
The substrate to be polished using the polishing composition disclosed herein is not particularly limited. For example, the polishing composition disclosed herein can be applied to polish a substrate having a surface made of a compound semiconductor material, that is, a compound semiconductor substrate. The constituent materials of the compound semiconductor substrate are not particularly limited, and are, for example, II-VI group compound semiconductors such as cadmium tellurate, zinc selenium, cadmium sulfide, cadmium telluride mercury, and cadmium zinc telluride; gallium phosphide and gallium arsenide. Group III-V compound semiconductors such as gallium phosphide, indium phosphide, aluminum gallium arsenide, gallium arsenide, indium gallium arsenide, and gallium phosphide indium; IV-IV such as silicon carbide and germanium silicate. Group compound semiconductor; etc. Of these, a substrate having a surface made of a plurality of materials may be used. In some preferred embodiments, the polishing compositions disclosed herein can be applied to polish a substrate having a surface composed of a non-oxide (ie, non-oxide) compound semiconductor material. When polishing a substrate having a surface made of a non-oxide compound semiconductor material, the polishing promoting effect of the oxidizing agent contained in the polishing composition disclosed herein is likely to be suitably exhibited.

The polishing composition disclosed herein can be preferably used, for example, for polishing the surface of a substrate having a Vickers hardness of 500 Hv or more. The Vickers hardness is preferably 700 Hv or higher, for example 1000 Hv or higher, and in some preferred embodiments 1500 Hv or higher. The Vickers hardness of the substrate material may be 1800 Hv or more, 2000 Hv or more, or 2200 Hv or more. The upper limit of the Vickers hardness of the substrate surface is not particularly limited, and may be, for example, approximately 7,000 Hv or less, 5000 Hv or less, or 3000 Hv or less. In this specification, the Vickers hardness can be measured based on JIS R 1610: 2003. The international standard corresponding to the above JIS standard is ISO 14705: 2000.

Examples of the material having a Vickers hardness of 1500 Hv or more include silicon carbide, silicon nitride, titanium nitride, gallium nitride and the like. The substrate in the techniques disclosed herein may have a single crystal surface of the above material that is mechanically and chemically stable. Among them, the surface of the substrate is preferably composed of either silicon carbide or gallium nitride, and more preferably composed of silicon carbide. Silicon carbide is expected as a compound semiconductor substrate material with low power loss and excellent heat resistance, and the practical advantage of efficiently smoothing and flattening the surface thereof is particularly great. The techniques disclosed herein may be particularly preferably applied to polishing the single crystal surface of silicon carbide.

<Polishing method>
The polishing composition disclosed herein can be used when polishing a substrate, for example, in an embodiment including the following operations.
That is, a polishing liquid (slurry) containing any of the polishing compositions disclosed herein is prepared. To prepare the above polishing liquid, the polishing liquid is prepared by adjusting the concentration of the polishing composition (for example, diluting the polishing composition), adjusting the pH of the polishing composition, or the like. Can be included. Alternatively, the above-mentioned polishing composition may be used as it is as a polishing liquid. Further, in the case of a multi-dosage type polishing composition, the above-mentioned polishing liquid is prepared by mixing the agents, diluting one or more agents before the mixing, and after the mixing. Diluting the mixture, etc. may be included.
The polishing liquid is then supplied to the polishing surface and polished by a conventional method performed by those skilled in the art. For example, it is a method in which a substrate is set in a general polishing apparatus and the polishing liquid is supplied to a polishing surface of the substrate through a polishing pad of the polishing apparatus. Typically, while continuously supplying the polishing liquid, the polishing pad is pressed against the polishing surface of the substrate to move the two relative to each other (for example, rotational movement). Polishing of the substrate is completed through such a polishing step.

According to this specification, a polishing method for polishing a substrate and a method for manufacturing a substrate using the polishing method are provided. The polishing method is characterized by including the step of polishing the substrate with the polishing composition disclosed herein. The polishing method according to some preferred embodiments includes a step of performing preliminary polishing (preliminary polishing step) and a step of performing finish polishing (finish polishing step). In some preferred embodiments, the pre-polishing step is a polishing step that is placed immediately prior to the finishing polishing step. The preliminary polishing step may be a one-step polishing step, or may be a plurality of two or more steps of polishing steps. Further, the finish polishing step referred to here is a step of performing finish polishing on a substrate on which preliminary polishing has been performed, and is the last of the polishing steps performed using a polishing slurry containing abrasive grains (that is, that is). It refers to the polishing process that is arranged (on the most downstream side). As described above, in the polishing method including the preliminary polishing step and the finishing polishing step, the polishing composition disclosed herein may be used in one step of the preliminary polishing step or may be used in the finishing polishing step. , May be used in both the pre-polishing step and the finishing polishing step.

Preliminary polishing and finish polishing can be performed by either a single-sided polishing device or a double-sided polishing device. In a single-sided polishing device, a substrate is attached to a ceramic plate with wax, the substrate is held by a holder called a carrier, and a polishing pad is pressed against one side of the substrate while supplying a polishing composition to make the two relative to each other. One side of the object to be polished is polished by moving it. The movement is, for example, a rotational movement. In the double-sided polishing device, the substrate is held by a holder called a carrier, and while the polishing composition is supplied from above, the polishing pads are pressed against the facing surfaces of the substrate and rotated in the relative direction of the substrate. Polish both sides at the same time.

The polishing pad used in each polishing process disclosed here is not particularly limited. For example, any of non-woven fabric type, suede type, rigid polyurethane foam type, those containing abrasive grains, those containing no abrasive grains and the like may be used. In some embodiments, a non-woven fabric type or a rigid foamed polyurethane type polishing pad containing no abrasive grains can be preferably adopted.

Substrates polished by the methods disclosed herein are typically cleaned after polishing. This cleaning can be performed using a suitable cleaning solution. The cleaning solution to be used is not particularly limited, and known and commonly used cleaning solutions can be appropriately selected and used.

Note that the polishing method disclosed herein may include any other steps in addition to the preliminary polishing step and the finishing polishing step. Examples of such a step include a mechanical polishing step and a wrapping step performed before the preliminary polishing step. In the mechanical polishing step, the substrate is polished using a liquid in which diamond abrasive grains are dispersed in a solvent. In some preferred embodiments, the dispersion is oxidant-free. The lapping step is a step of pressing the surface of a polishing surface plate, for example, a cast iron surface plate, against a substrate to polish it. Therefore, the polishing pad is not used in the wrapping process. The wrapping step is typically performed by supplying abrasive grains between the polishing surface plate and the substrate. The abrasive grains are typically diamond abrasive grains. Further, the polishing method disclosed herein may include an additional step before the preliminary polishing step or between the preliminary polishing step and the finishing polishing step. The additional steps are, for example, a cleaning step and a polishing step.

<Manufacturing method of substrate>
The techniques disclosed herein may include a method of making a substrate that includes a polishing step by any of the polishing methods described above and the provision of a substrate made by that method. The method for manufacturing the substrate is, for example, a method for manufacturing a silicon carbide substrate. That is, according to the techniques disclosed herein, a method of manufacturing a substrate, including polishing any of the substrates disclosed herein by any of the methods disclosed herein, and a substrate produced by that method. Is provided. According to the above manufacturing method, a substrate having improved surface quality, for example, a silicon carbide substrate can be efficiently provided.

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

<Preparation of polishing composition>
(Example 1)
Fumed silica, potassium permanganate (KMnO ₄ ) as an oxidizing agent, calcium nitrate as a metal salt, and deionized water were mixed to prepare the polishing composition of this example. The concentration of fumed silica was 1%, the concentration of potassium permanganate was 260 mmol / L, and the concentration of calcium nitrate was 15 mmol / L. The pH of the polishing composition is as shown in Table 1. As the fumed silica, one having an average primary particle size of 30 nm and an average secondary particle size of 150 nm was used.

(Examples 2 to 3)
The polishing composition of each example was prepared in the same manner as in Example 1 except that the concentration of calcium nitrate was set to the concentration shown in Table 1.

(Examples 4 to 6)
The polishing composition of each example was prepared in the same manner as in Example 1 except that the concentration of the oxidizing agent was 80 mmol / L and the concentration of calcium nitrate was the concentration shown in Table 1.

(Examples 7 to 8)
The polishing compositions of each example were prepared in the same manner as in Example 4 except that the types and concentrations of the metal salts were shown in Table 1.

(Examples 9 to 11)
The polishing compositions of each example were prepared in the same manner as in Example 4 except that the concentration of calcium nitrate was 15 mmol / L and the concentration of fumed silica was the concentration shown in Table 1.

(Examples 12 to 13)
The polishing compositions of each example were prepared in the same manner as in Example 4 except that the types and concentrations of the metal salts were shown in Table 1.

(Comparative Examples 1 and 2)
The polishing composition of each example was prepared in the same manner as in Example 4 except that the concentration of calcium nitrate was set to the concentration shown in Table 1.

(Comparative Examples 3 to 4)
The polishing compositions of each example were prepared in the same manner as in Example 4 except that the types and concentrations of the metal salts were shown in Table 1.

<Evaluation of polishing removal speed>
Preliminary polishing was performed in advance using a polishing liquid containing alumina abrasive grains. The surface of the pre-polished SiC wafer was polished under the following conditions using the polishing compositions of each example as they were as a polishing liquid. Then, the polishing rate was calculated according to the following calculation formulas (1) and (2). The results are shown in the corresponding columns of Table 1.
(1) Polishing allowance [cm] = difference in weight of SiC wafer before and after polishing [g] / SiC density [g / cm ³ ] (= 3.21 ^{g / cm 3} ) / polishing target area [cm ² ] ( = 19.62 cm ² )
(2) polishing rate [nm / h] = grinding allowance [cm] × 10 ⁷ / polishing time (= 1 hour)
[Policing conditions]
Polishing device: Single-sided polishing device manufactured by Nippon Engis, model "EJ-380IN-CH"
Polishing pad: "SUBA800XY" manufactured by Nitta Haas
Polishing pressure: 29.4 kPa
Surface plate rotation speed: 80 rotations / minute Head rotation speed: 40 rotations / minute Polishing liquid supply rate: 20 mL / minute (flowing)
Abrasive temperature: 25 ° C
Polishing time: 1 hour Polishing object: SiC wafer (conduction type: n type, crystal type 4H-SiC, off angle of main surface (0001) with respect to C axis: 4)
2 inches x 3 sheets

As shown in Table 1, according to the polishing compositions of Examples 1-13, which contained fumed silica and an oxidizing agent and contained a metal salt in a proportion of more than 10 mmol / L, the metal salt content was 10. The polishing rate was improved as compared with Comparative Examples 1 to 4 having a millimole / L or less.

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

Claims

Contains fumed silica, an oxidant, and a metal salt,
A polishing composition having a metal salt content of more than 10 mmol / L.
The polishing composition according to claim 1, wherein the metal salt is a nitrate and / or hydrochloride of an alkali metal and / or an alkaline earth metal.
The polishing composition according to claim 1 or 2, wherein the metal forming the metal salt is potassium.
The polishing composition according to claim 1 or 2, wherein the metal forming the metal salt is calcium.
The polishing composition according to any one of claims 1 to 4, wherein the oxidizing agent contains a composite metal oxide.
Any one of claims 1 to 5, wherein the ratio (B / A) of the concentration B [mmol / L] of the metal salt to the concentration A [mmol / L] of the oxidizing agent is 0.01 or more and 10 or less. The polishing composition according to.
The polishing composition according to any one of claims 1 to 6, wherein the pH is greater than 5.0 and less than 9.0.
The polishing composition according to any one of claims 1 to 7, which is used for polishing a material having a Vickers hardness of 1500 Hv or more.
The polishing composition according to any one of claims 1 to 8, which is used for polishing silicon carbide.
A method for polishing a substrate, which comprises a step of polishing the substrate using the polishing composition according to any one of claims 1 to 9.