Polishing composition

Abstract

This invention provides a grinding composition for silicon-germanium with sufficiently fast grinding speed and sufficiently high selectivity for grinding speed. The grinding composition of this invention comprises abrasive grains, an inorganic salt, and an oxidizing agent, wherein the abrasive grains have a silanol group number exceeding 0 per unit surface area per nm. 2 and 2.0 units / nm 2 or less, the pH value of the above-mentioned grinding composition is 6.0 or higher.

Description

[Technical Field]

[0001] This invention relates to a grinding composition. [Previous Technology]

[0002] As a technology to reduce power consumption or improve the performance (operational characteristics) of transistors, a channel using a high-mobility material (hereinafter also referred to as "high-mobility material") with a carrier mobility higher than that of Si is being researched. The improved carrier transport characteristics of the channel fabricated using this high-mobility material increase the drain current when a specified gate voltage is applied. This provides the advantages of obtaining a sufficiently high drain current and reducing the supply voltage. This advantage enables MOSFETs (metal oxide semiconductor field-effect transistors) to have higher performance at low power.

[0003] As a high-mobility material, the use of graphene and other materials containing only group III-V compounds, group IV compounds, Ge (germanium), and C (carbon) is expected. In particular, group III-V compounds containing As and group IV compounds containing Ge are being actively researched.

[0004] Channels using high-mobility materials can be formed by polishing a polishing object such as silicon-germanium (SiGe), which has: a portion containing high-mobility material (hereinafter also referred to as the high-mobility material portion); and a portion containing silicon material (hereinafter also referred to as the silicon material portion). For example, Japanese Patent Publication No. 2018-506176 (U.S. Patent Application Publication No. 2017 / 0369743) discloses a polishing composition for polishing a substrate containing germanium. [Summary of the Invention]

[0005] Recently, a semiconductor substrate containing both silicon germanium and other materials such as silicon nitride (SiN) and silicon oxide (SiO2) has been used. For this type of substrate, a new requirement has been placed: silicon germanium must be ground at a higher grinding speed, and silicon germanium must be ground selectively relative to other materials. No research has been conducted previously regarding this requirement.

[0006] Therefore, the object of the present invention is to provide a grinding composition having a sufficiently fast grinding speed for silicon and germanium and a sufficiently high selectivity ratio for the grinding speed of silicon and germanium.

[0007] In order to solve the above-mentioned new problems, the inventors conducted repeated and intensive research. As a result, it was found that the above problems could be solved by the following grinding composition, which includes abrasive particles, an inorganic salt, and an oxidant, wherein the number of silanol groups per unit surface area of ​​the abrasive particles is more than 0 / nm2 and less than 2.0 / nm2, and the pH value of the grinding composition is 6.0 or higher, thereby completing the present invention.

Implementation Method

[0008] One aspect of the present invention is a polishing composition comprising abrasive grains, an inorganic salt, and an oxidizing agent, wherein the number of silanol groups per unit surface area of ​​the abrasive grains is greater than 0 / nm² and less than 2.0 / nm², and the pH value of the polishing composition is 6.0 or higher. With this polishing composition, the polishing speed of silicon-germanium can be sufficiently improved, and the selectivity of the polishing speed of silicon-germanium can be sufficiently improved, that is, the selectivity of the polishing speed of silicon-germanium relative to the polishing speed of other materials (e.g., silicon nitride (SiN), silicon oxide (SiO₂)).

[0009] The mechanism by which the effects of the present invention as described above are believed to be achieved is as follows. However, the following mechanism is merely speculative, and the scope of the present invention is not limited thereto.

[0010] Because the number of silanol groups per unit surface area of ​​the abrasive grains exceeds 0 per nm² and is less than 2.0 per nm², the hydrophobicity of the abrasive grain surface becomes high. As a result, it is believed that the grinding speed of silicon-germanium oxidized by the action of the oxidant can be improved.

[0011] Furthermore, since the number of silanol units per unit surface area of ​​the abrasive particles is low, the amount of bound water between the abrasive particles and the surface of the silicon-germanium film is reduced. Therefore, it is believed that the abrasive particles become easier to contact the silicon-germanium film, and the grinding speed of silicon-germanium is increased.

[0012] Furthermore, since the polishing composition contains inorganic salts, the conductivity of the polishing composition increases. As a result, it is believed that the electrical double layer formed on the surface of the silicon-germanium film is compressed, the effect of the abrasive particles is enhanced, and the polishing speed of the silicon-germanium film increases.

[0013] Hereinafter, one embodiment of the present invention will be described. The present invention is not limited to the following embodiments.

[0014] In this specification, the range "X to Y" means "X or more and Y or less". Also, unless otherwise stated, the operation and physical properties are measured at room temperature (20 to 25°C) and relative humidity of 40 to 50%RH.

[0015] [Abrasive Composition] (Abrasive Particles) The abrasive composition of this form contains abrasive particles with a silanol group number of more than 0 per nm² and less than 2.0 per nm² per unit surface area. The abrasive particles have the function of mechanically abrading the object to be abraded, thereby increasing the speed of abrading the object using the abrasive composition.

[0016] Regarding the abrasive grains of this type, there are no particular limitations if the number of silanol groups per unit surface area of ​​the abrasive grains (hereinafter referred to as "silanol group density") exceeds 0 units / nm² and is less than 2.0 units / nm². If the silanol group density of the abrasive grains is within this range, the grinding speed of silicon-germanium can be sufficiently improved. The silanol group density of the abrasive grains is preferably more than 0.5 units / nm² and less than 2.0 units / nm², and more preferably more than 1.0 units / nm² and less than 2.0 units / nm².

[0017] The silanol basis per unit surface area of ​​the abrasive particles can be calculated using the Sears method of neutralization titration as described in GW Sears' Analytical Chemistry, vol.28, No.12, 1956, 1982-1983. The silanol basis is calculated using the following formula.

[0018] [Number 1] ρ: Silanol number [number / nm2] c: Concentration of sodium hydroxide solution used for titration [mol / L] a: Volume of sodium hydroxide solution added at pH 4-9 [ml] NA: Avogadro number (6.022×1023 [number / mol]), C: Mass of silicon dioxide [g] S: BET (Brunauer-Emmett-Teller) specific surface area [nm2 / g]

[0019] The number of silanol units per unit surface area of ​​the abrasive grains can be controlled by selecting the manufacturing method of the abrasive grains, etc.

[0020] The abrasive particles preferably contain silicon dioxide, more preferably contain fuming silicon dioxide or colloidal silicon dioxide, and even more preferably contain colloidal silicon dioxide.

[0021] There are no particular limitations on the shape of the abrasive particles; they can be spherical or non-spherical. Specific examples of non-spherical shapes are not particularly limited and include: triangular prisms or quadrangular prisms, cylindrical shapes, pouch-shaped shapes where the central part of a cylinder expands compared to the end, annular shapes with a central part of a disc, plate-shaped shapes, cocoon-shaped shapes with a central part contraction, so-called associated spherical shapes formed by multiple particles integrated into one, so-called konpeito shapes with multiple protrusions on the surface, rugby ball shapes, and various other shapes.

[0022] When colloidal silicon dioxide is used as abrasive grains, the surface of the colloidal silicon dioxide can be modified by using silane coupling agents or the like.

[0023] As a method for surface modification of colloidal silica using a silane coupling agent, the following immobilization method can be cited as an example. For example, it can be carried out by the method described in "Sulfonic acid-functionalized silica through of thiol groups", Chem. Commun. 246-247 (2003). Specifically, a silane coupling agent having thiol groups, such as 3-mercaptopropyltrimethoxysilane, can be coupled with colloidal silica, and then the thiol groups can be oxidized using hydrogen peroxide, thereby obtaining colloidal silica with sulfonic acid immobilized on the surface.

[0024] Alternatively, for example, this can be carried out by the method described in "Novel Silane Coupling Agents Containing a Photolabile 2-Nitrobenzyl Ester for Introduction of a Carboxy Group on the Surface of Silica Gel", Chemistry Letters, 3, 228-229 (2000). Specifically, colloidal silica with carboxylic acid fixed on the surface can be obtained by photo-irradiation after coupling a silane coupling agent containing photoreactive 2-nitrobenzyl ester with colloidal silica.

[0025] The above describes colloidal silica with anionic groups (anionic modified colloidal silica), but colloidal silica with cationic groups (cationic modified colloidal silica) may also be used. As a colloidal silica with cationic groups, colloidal silica with amine groups fixed on the surface can be cited as an example. As a method for manufacturing colloidal silica with cationic groups, an example is the method described in Japanese Patent Application Publication No. 2005-162533, which involves fixing silane coupling agents with amino groups, such as aminoethyltrimethoxysilane, aminopropyltrimethoxysilane, aminoethyltriethoxysilane, aminopropyltriethoxysilane, aminopropyldimethylethoxysilane, aminopropylmethyldiethoxysilane, and aminobutyltriethoxysilane, onto the surface of colloidal silica. This method yields colloidal silica with amino groups fixed to its surface.

[0026] The average primary particle size of the abrasive grains is preferably 5 nm or more, more preferably 10 nm or more, and even more preferably 15 nm or more. As the average primary particle size of the abrasive grains increases, the grinding speed of the object being ground using the abrasive composition increases. Furthermore, the average primary particle size of the abrasive grains is preferably 120 nm or less, more preferably 80 nm or less, and even more preferably 50 nm or less. As the average primary particle size of the abrasive grains decreases, it becomes easier to obtain a surface with fewer defects by grinding using the abrasive composition. The average primary particle size of the abrasive grains can be calculated, for example, based on the specific surface area (SA) of the abrasive grains calculated according to the BET method, assuming the shape of the abrasive grains is a true sphere. In this specification, the average primary particle size of the abrasive grains is the value measured by the method described in the examples.

[0027] The average secondary particle size of the abrasive particles is preferably 30 nm or more, more preferably 40 nm or more, and even more preferably 50 nm or more. As the average secondary particle size of the abrasive particles increases, the resistance during the grinding process decreases, thereby enabling stable grinding. Furthermore, the average secondary particle size of the abrasive particles is preferably 250 nm or less, more preferably 200 nm or less, even more preferably 150 nm or less, and particularly preferably 100 nm or less. As the average secondary particle size of the abrasive particles decreases, the surface area per unit mass of the abrasive particles increases, the contact frequency with the object being ground increases, and the grinding speed is further increased. The average secondary particle size of the abrasive particles can be measured, for example, by dynamic light scattering methods, such as laser diffraction scattering. In this specification, the average secondary particle size of the abrasive particles is the value measured by the method described in the examples.

[0028] There is no particular limitation on the upper limit of the aspect ratio of the abrasive grains, but it is preferably less than 2.0, more preferably less than 1.8, and even more preferably less than 1.6. Within this range, defects on the surface of the object being polished can be further reduced. Furthermore, the aspect ratio is the average value obtained by dividing the length of the longer side of the smallest rectangle circumscribed by the image of the abrasive grains using a scanning electron microscope by the length of the shorter side of the same rectangle. This value can be determined using general image analysis software. There is no particular limitation on the lower limit of the aspect ratio of the abrasive grains in the polishing composition, but it is preferably 1.0 or higher.

[0029] In the particle size distribution of the abrasive particles determined by laser diffraction, the lower limit of the ratio of the diameter of the particle (D90) when the cumulative particle weight from the microparticle side reaches 90% of the total particle weight to the diameter of the particle (D10) when it reaches 10% of the total particle weight, i.e., D90 / D10, is not particularly limited, but is preferably 1.1 or more, more preferably 1.2 or more, and even more preferably 1.3 or more. Furthermore, in the particle size distribution of the abrasive particles in the abrasive composition determined by laser diffraction, the upper limit of the ratio of the diameter of the particle (D90) when the cumulative particle weight from the microparticle side reaches 90% of the total particle weight to the diameter of the particle (D10) when it reaches 10% of the total particle weight, i.e., D90 / D10, is not particularly limited, but is preferably 2.04 or less. Within this range, defects on the surface of the object being abraded can be further reduced.

[0030] The size of the abrasive grains (average primary grain size, average secondary grain size, aspect ratio, D90 / D10, etc.) can be appropriately controlled by selecting the manufacturing method of the abrasive grains.

[0031] The content (concentration) of abrasive particles in the grinding composition is not particularly limited, but is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.3% by mass or more, relative to the total mass of the grinding composition. Furthermore, the upper limit of the abrasive particle content is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, relative to the total mass of the grinding composition. That is, the content of silicon dioxide is preferably 0.05% by mass or more and 20% by mass or less, more preferably 0.1% by mass or more and 10% by mass or less, and even more preferably 0.3% by mass or more and 5% by mass or less, relative to the total mass of the grinding composition. Within this range, the grinding speed of the object being ground can be increased while controlling costs. Furthermore, when the grinding composition contains two or more types of abrasive particles, the content of abrasive particles refers to their total amount.

[0032] (Inorganic Salt) The grinding composition of this form contains an inorganic salt. This inorganic salt increases the conductivity of the grinding composition and compresses the electrical double layer on the surface of silicon-germanium. Therefore, it can enhance the effect of the abrasive particles on the surface of silicon-germanium and increase the grinding speed of silicon-germanium.

[0033] As an inorganic salt, there are no particular restrictions. Examples include salts of monoprotic inorganic acids, salts of diprotic inorganic acids, and salts of triprotic inorganic acids.

[0034] Examples of monoprotic inorganic acids include hydrochloric acid, nitric acid, and nitrous acid. Examples of diprotic inorganic acids include sulfuric acid, carbonic acid, sulfurous acid, thiosulfate, and phosphonic acid. Examples of ternary inorganic acids include phosphoric acid, phosphomolybdic acid, phosphotungstic acid, and vanadic acid.

[0035] Examples of salts of monobasic inorganic acids, dibasic inorganic acids, and tribasic inorganic acids include lithium salts, sodium salts, potassium salts, calcium salts, magnesium salts, and ammonium salts.

[0036] More specific examples of inorganic salts include sodium nitrate, potassium nitrate, ammonium nitrate, magnesium nitrate, calcium nitrate, sodium nitrite, potassium nitrite, lithium carbonate, sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate, lithium bicarbonate, sodium bicarbonate, potassium bicarbonate, ammonium carbonate, sodium bicarbonate, sodium sulfate, potassium sulfate, ammonium sulfate, calcium sulfate, magnesium sulfate, sodium sulfite, potassium sulfite, calcium sulfite, magnesium sulfite, potassium thiosulfate, lithium sulfate, magnesium sulfate, sodium thiosulfate, sodium bisulfite, ammonium bisulfate, lithium bisulfate, sodium bisulfate, potassium bisulfate, trilithium phosphate, tripotassium phosphate, trisodium phosphate, triammonium phosphate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, diammonium hydrogen phosphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, and ammonium dihydrogen phosphate. These inorganic salts can be used alone or in combination of two or more.

[0037] In these, from the viewpoint of preventing metal contamination of the grinding object, the inorganic salt is preferably selected from at least one of the group consisting of ammonium nitrate, ammonium sulfate, ammonium bisulfate, triammonium phosphate, diammonium hydrogen phosphate and dihydrogen phosphate, more preferably selected from ammonium sulfate and triammonium phosphate, and even more preferably ammonium sulfate.

[0038] The content (concentration) of inorganic salts in the grinding composition is not particularly limited, but it is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and even more preferably 0.05% by mass or more, relative to the total mass of the grinding composition. Furthermore, the upper limit of the content of inorganic salts in the grinding composition used in this invention is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less, relative to the total mass of the grinding composition. If the content of inorganic salts is 0.01% by mass or more, the electrical double layer of the silicon-germanium film is sufficiently compressed, making it easier for the abrasive particles to contact the silicon-germanium film, thereby increasing the grinding speed of the silicon-germanium film. If the content of inorganic salts is less than 5% by mass, the increase in conductivity can be suppressed. This compresses the electrical double layer between the abrasive grains and the film other than silicon and germanium (e.g., silicon oxide film, silicon nitride film), making it difficult for the abrasive grains to contact the film other than silicon and germanium, thereby suppressing the increase in the abrasive grains' grinding speed. Furthermore, it can suppress the decrease in storage stability caused by the increase in conductivity.

[0039] Furthermore, when the grinding composition contains two or more inorganic salts, the content of the inorganic salts refers to their total amount.

[0040] (Oxidizing agent) The grinding composition of this form contains an oxidizing agent. The oxidizing agent has the effect of oxidizing the surface of silicon and germanium, which can further improve the grinding speed of silicon and germanium using the grinding composition.

[0041] Examples of oxidizing agents include hydrogen peroxide, sodium peroxide, barium peroxide, ozonated water, silver (II) salts, iron (III) salts, permanganic acid, chromic acid, dichromic acid, peroxydisulfuric acid, peroxyphosphoric acid, peroxysulfuric acid, peroxyboric acid, performic acid, peracetic acid, perbenzoic acid, perphthalic acid, hypochlorous acid, hypobromic acid, hypoiodic acid, chloric acid, chlorous acid, perchloric acid, bromic acid, iodic acid, periodic acid, persulfuric acid, dichloroisocyanuric acid, and their salts. These oxidizing agents can be used alone or in combination of two or more.

[0042] In these, the oxidant is preferably one that does not contain halogen atoms, and more preferably hydrogen peroxide.

[0043] The lower limit of the content (concentration) of the oxidant in the grinding composition is preferably 0.001% by mass or more, and more preferably 0.01% by mass or more. By setting such a lower limit, the grinding speed of silicon and germanium can be further improved. Furthermore, the upper limit of the content of the oxidant in the grinding composition is preferably 5% by mass or less, and more preferably 3% by mass or less. By setting such an upper limit, the material cost of the grinding composition can be controlled, and the burden of wastewater treatment after grinding can be reduced. In addition, the risk of excessive oxidation of the surface of the object being ground due to the oxidant can also be reduced.

[0044] (Grinding accelerator) The grinding composition of this form may further include a grinding accelerator.

[0045] This type of polishing accelerator has the function of adsorbing onto the surface of the Ge oxide film and partially modifying the Ge oxide film. It is believed that the modified Ge oxide film has excellent processability and faster polishing speed, but it is not easy to dissolve and etching is suppressed.

[0046] This type of grinding accelerator preferably has an acid group. Examples of acid groups include carboxyl groups, phosphate groups, phosphonic acid groups, sulfuric acid groups, sulfonic acid groups, etc.

[0047] Specific examples of grinding accelerators include: ethylenediaminetetraacetic acid, aziridine triacetic acid, hydroxyethyl ethylenediaminetetraacetic acid, diethyltriaminepentaacetic acid, triethyltetraaminehexaacetic acid, N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid, ethylene glycol ether diaminetetraacetic acid, 1,3-propanediamine-N,N,N',N'-tetraacetic acid, 1,3-diamino-2-propanol-N,N,N',N'-tetraacetic acid, N-(2-hydroxyethyl)iminodiacetic acid, methyl phosphate, and ethyl phosphate. phosphate), ethylene glycol phosphate, isopropyl phosphate, phytic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotris(methylenephosphonic acid), diethyltriaminepenta(methylenephosphonic acid), aminopoly(methylenephosphonic acid), 2-aminoethylphosphonic acid, nitrotris(methylenephosphonic acid), N,N,N',N'-ethylenediaminetetra(methylenephosphonic acid), diethyltriaminepenta(methylenephosphonic acid), ethane-1,1-diphosphonic acid, ethane-hydroxy-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, methane-hydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, α-methylphosphonosuccinic acid, N,N-bis(2-hydroxyethyl)glycine, aspartic acid, glutamic acid, dicarboxymethylglutamic acid, (S,S)-ethylenediamine-N,N'-disuccinic acid, 2,3-dihydroxybenzoic acid, iminodiacetic acid, etidronic acid, maltodextrin, and salts thereof.

[0048] Grinding accelerators can be used alone or in combination of two or more. Furthermore, grinding accelerators can be synthetic products or commercially available products. Examples of commercially available grinding accelerators include CHELEST PH-430, CHELEST PH-540, CHELEST GA, CHELEST EDDS-4H, and CHELEST HA (all manufactured by CHELEST Co., Ltd.).

[0049] From the viewpoint that such grinding accelerators can independently increase the processing speed of silicon-germanium without changing the processing speed of other film types such as silicon oxide film or silicon nitride film, it is preferred to be at least one of the group consisting of N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid, N,N,N',N'-ethylenediaminetetra(methylenephosphonic acid), 2-phosphatidylbutane-1,2,4-tricarboxylic acid, N,N-bis(2-hydroxyethyl)glycine, aspartic acid, and (S,S)-ethylenediamine-N,N'-disuccinic acid, more preferably selected from N,N,N',N'-ethylenediaminetetra(methylenephosphonic acid) and 2-phosphatidylbutane-1,2,4-tricarboxylic acid, and even more preferably N,N,N',N'-ethylenediaminetetra(methylenephosphonic acid).

[0050] The content (concentration) of the grinding accelerator in the grinding composition is not particularly limited, but it is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.08% by mass or more, relative to the total mass of the grinding composition. Furthermore, the upper limit of the content of the grinding accelerator in the grinding composition is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less, relative to the total mass of the grinding composition. Within this range, the grinding speed of silicon and germanium can be further improved.

[0051] When the grinding composition contains two or more grinding accelerators, the content of the grinding accelerators refers to the total amount of them.

[0052] (pH adjuster) The grinding composition of this form may contain a pH adjuster to make the pH value 6.0 or higher.

[0053] There are no particular restrictions on pH adjusters, as long as they are compounds with pH adjusting function, and well-known compounds can be used. Examples of pH adjusters include acids and bases.

[0054] As an acid, either an inorganic acid or an organic acid may be used. There are no particular limitations on inorganic acids; examples include sulfuric acid, nitric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, and phosphoric acid. There are no particular limitations on organic acids; examples include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylvaleric acid, heptanoic acid, 2-methylhexanoic acid, octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, and lactic acid, as well as methanesulfonic acid, ethanesulfonic acid, and hydroxyethanesulfonic acid.

[0055] As a base, there are no particular limitations, and examples include alkali metal hydroxides such as potassium hydroxide, quaternary ammonium salts such as ammonia, tetramethylammonium and tetraethylammonium, amines such as ethylenediamine and piperidine, etc. Among these, ammonia is preferred.

[0056] pH adjusters can be used alone or in combination of two or more.

[0057] There is no particular limitation on the content of the pH adjuster, which can be adjusted appropriately to make the grinding composition have the required pH value.

[0058] (Dispersion Medium) The grinding composition of this form may include a dispersion medium for dispersing the components. Examples of dispersion media include: water; alcohols such as methanol, ethanol, and ethylene glycol; ketones such as acetone; or mixtures thereof. Among these, water is preferred as the dispersion medium. That is, according to a more preferred form of the invention, the dispersion medium comprises water. According to a further preferred form of the invention, the dispersion medium is substantially composed of water. Furthermore, the above "substantially" is intended to mean that a dispersion medium other than water may be included, as long as the objective effect of the invention can be achieved. More specifically, it is preferably composed of 90% to 100% by mass of water and 0% to 10% by mass of a dispersion medium other than water, more preferably composed of 99% to 100% by mass of water and 0% to 1% by mass of a dispersion medium other than water. Most preferably, the dispersion medium is water.

[0059] From the viewpoint of not hindering the function of the components contained in the grinding composition, the dispersion medium is preferably water that is as free of impurities as possible. Specifically, it is more preferably pure water or ultrapure water, or distilled water, after removing impurity ions by using an ion exchange resin and removing foreign matter by a filter.

[0060] (Other Ingredients) This grinding composition may also contain other ingredients such as chelating agents, preservatives, and fungicides, as needed. The content of other ingredients may be appropriately set according to their purpose. The preservatives and fungicides, which are other ingredients, will be described below.

[0061] Examples of preservatives and fungicides include isothiazolin-based preservatives such as 2-methyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, 1,2-benzisothiazolin-3-one, and 2-n-octyl-4-isothiazolin-3-one, as well as parabens, o-phenylphenol, and phenoxyethanol. These preservatives and fungicides can be used alone or in combination of two or more.

[0062] (pH value of the abrasive composition) Regarding the pH value of the abrasive composition of this form, there are no particular limitations if it is 6.0 or higher, and it can be appropriately adjusted according to the combination of abrasive grains, inorganic salts, and oxidants used. The lower limit of the pH value is preferably 7.0 or higher, more preferably 8.0 or higher, and even more preferably 9.0 or higher. The upper limit of the pH value is, for example, 13.0 or lower, more preferably 12.0 or lower, and even more preferably 11.0 or lower. When the pH value is below 6.0, the etching reaction of silicon and germanium deteriorates, and the abrasive speed decreases significantly. When the pH value exceeds 13, the stability of the abrasive composition cannot be maintained.

[0063] The pH value of the grinding composition can be measured by a pH meter (manufactured by Horiba Manufacturing Co., Ltd., model: LAQUA).

[0064] (Method for Manufacturing Grinding Composition) There are no particular limitations on the method for manufacturing the grinding composition of this form. For example, grinding particles, inorganic salts, oxidizing agents, and other additives can be stirred and mixed in a dispersion medium (e.g., water) as needed to obtain the grinding composition of this form. Details of each component are as described above. Therefore, the present invention provides a method for manufacturing a grinding composition, comprising the step of mixing grinding particles, inorganic salts, and an oxidizing agent.

[0065] There are no particular restrictions on the temperature when mixing the components, but it is preferably between 10°C and 40°C. Heating can also be used to increase the dissolution rate. Furthermore, there are no particular restrictions on the mixing time, as long as the components are mixed evenly.

[0066] (Application) The grinding composition of this form is preferably used for grinding a grinding object containing silicon and germanium. The germanium content in the silicon and germanium of the grinding object is preferably 10% by mass or more.

[0067] Regarding the grinding object of this embodiment, if it contains silicon germanium, it may also contain other silicon-containing materials. Examples of silicon-containing materials include elemental silicon and silicon compounds. Furthermore, examples of elemental silicon include monocrystalline silicon, polycrystalline silicon (Poly-Si), and amorphous silicon. Examples of silicon compounds include silicon nitride (SiN), silicon oxide (SiO2), and silicon carbide. Materials containing silicon also include those with low dielectric constants, such as those with a relative permittivity of 3 or less.

[0068] Examples of films containing silicon oxide include TEOS (Tetraethyl Orthosilicate) type silicon oxide films (hereinafter also referred to as "TEOS films") generated using tetraethyl orthosilicate as a precursor, HDP (High Density Plasma) films, USG (Undoped Silicate Glass) films, PSG (Phosphorus Silicate Glass) films, BPSG (Boron-Phospho Silicate Glass) films, and RTO (Rapid Thermal Oxidation) films.

[0069] [Grinding Method and Semiconductor Substrate Manufacturing Method] One aspect of the present invention is a grinding method, which includes the step of grinding an object to be ground using the above-mentioned grinding composition.

[0070] Furthermore, one aspect of the present invention is a method for manufacturing a semiconductor substrate, which includes a step of polishing the semiconductor substrate by the above-mentioned polishing method.

[0071] In the polishing method of this embodiment, a general polishing device can be used as the polishing apparatus. It is equipped with a support for holding a substrate with the object to be polished, a motor that can change the rotation speed, and a polishing pressure plate that can attach a polishing pad (polishing cloth).

[0072] There are no particular limitations on the type of abrasive pad; common non-woven fabrics, polyurethane, and porous fluoropolymers can be used. Preferably, the abrasive pad is grooved to store the abrasive fluid.

[0073] Regarding the polishing conditions, for example, the rotational speed of the polishing pad is preferably 10 rpm (0.17 s⁻¹) or more and 500 rpm (8.3 s⁻¹) or less. The pressure applied to the substrate with the object to be polished (polishing pressure) is preferably 0.5 psi (3.4 kPa) or more and 10 psi (68.9 kPa) or less. There are no particular limitations on the method of supplying the polishing composition to the polishing pad, for example, a continuous supply method using a pump or the like can be used. There are no limitations on the supply amount, but it is preferable that the surface of the polishing pad is always covered by the polishing composition of the present invention.

[0074] After grinding, the substrate is washed with running water and dried by removing water droplets adhering to the substrate using a rotary dryer or the like, thereby obtaining a substrate with a metal layer.

[0075] The grinding composition used in the grinding method of this embodiment can be a single-liquid type, or a two-liquid type or a multi-liquid type. Furthermore, the grinding composition used in the grinding method of this embodiment can be prepared by diluting the stock solution of the grinding composition to, for example, more than 10 times using a diluent such as water.

[0076] When grinding silicon and germanium using the grinding method of this embodiment, the grinding speed is preferably 280 Å / min or higher, more preferably 300 Å / min or higher, and even more preferably 400 Å / min or higher. Furthermore, when grinding silicon and germanium using the grinding method of this embodiment, the etching depth of silicon and germanium is preferably 80 Å or less, more preferably 60 Å or less. Moreover, the grinding speed and etching depth can be measured using the methods described in the embodiments.

[0077] The grinding method of this embodiment can also be applied to grinding objects containing germanium silicon and other materials. In this case, it is possible to obtain an effect where the ratio of the grinding speed of germanium silicon to the grinding speed of other materials is sufficiently high (i.e., the selectivity ratio is sufficiently high). For example, when the other material is silicon nitride, the ratio of the grinding speed of germanium silicon to the grinding speed of silicon nitride ([grinding speed of germanium silicon] / [grinding speed of silicon nitride]) is preferably 15 or more, more preferably 20 or more, and even more preferably 25 or more. Furthermore, when the other material is silicon oxide, the ratio of the grinding speed of germanium silicon to the grinding speed of silicon oxide ([grinding speed of germanium silicon] / [grinding speed of silicon oxide]) is preferably 10 or more, more preferably 13 or more. [Example]

[0078] The present invention will be further described using the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples. Furthermore, unless otherwise stated, "%" and "parts" refer to "mass %" and "parts by mass," respectively. Also, in the following examples, unless otherwise stated, the operation was carried out at room temperature (20-25°C) and relative humidity 40-50%RH.

[0079] (Example 1) Colloidal silica (average primary particle size 29 nm, average secondary particle size 61 nm, silanol group density 1.50 units / nm², aspect ratio 1.55) was added as abrasive particles at a content of 0.5% by mass relative to the entire grinding composition. Ammonium sulfate was added as an inorganic salt at a content of 0.1% by mass, and hydrogen peroxide was added as an oxidant at a content of 0.16% by mass. These components were stirred and mixed in pure water (mixing temperature: approximately 25°C, mixing time: approximately 10 minutes). The pH was adjusted to 10.4 using ammonia as a pH adjuster to prepare the grinding composition.

[0080] (Example 2) Except that ammonium sulfate was replaced with triammonium phosphate, the grinding composition was prepared in the same manner as in Example 1.

[0081] (Example 3) Except that the content of colloidal silicon dioxide was changed to 1.0% by mass, the grinding composition was prepared in the same manner as in Example 1.

[0082] (Example 4) Except that the content of ammonium sulfate was changed to 0.2% by mass, the grinding composition was prepared in the same manner as in Example 1.

[0083] (Example 5) Except that the pH value was adjusted to 9.2, the grinding composition was prepared in the same manner as in Example 1.

[0084] (Example 6) The grinding composition was prepared in the same manner as in Example 1, except that the hydrogen peroxide content was changed to 0.40% by mass.

[0085] (Example 7) Abrasive particles (average primary particle size 29 nm, average secondary particle size 61 nm, silanol group density 1.50 units / nm², aspect ratio 1.55) were added at 0.5% by mass relative to the entire grinding composition. Ammonium sulfate was added at 0.1% by mass as an inorganic salt, hydrogen peroxide at 0.16% by mass as an oxidant, and N,N,N',N'-ethylenediaminetetra(methylenephosphonic acid) (EDTMP) at 0.1% by mass as a grinding accelerator. These components were mixed in pure water by stirring (mixing temperature: approximately 25°C, mixing time: approximately 10 minutes). The pH was adjusted to 10.4 using ammonia as a pH adjuster to prepare the grinding composition.

[0086] (Example 8) Abrasive particles (average primary particle size 29 nm, average secondary particle size 61 nm, silanol group density 1.50 units / nm², aspect ratio 1.55) were added at 0.5% by mass relative to the entire grinding composition. Triammonium phosphate was added at 0.1% by mass as an inorganic salt, hydrogen peroxide at 0.16% by mass as an oxidant, and 2-phosphatidylbutane-1,2,4-tricarboxylic acid (PBTC) at 0.1% by mass as a grinding accelerator. These components were mixed in pure water by stirring (mixing temperature: approximately 25°C, mixing time: approximately 10 minutes). The pH was adjusted to 9.2 using ammonia as a pH adjuster to prepare the grinding composition.

[0087] (Comparative Example 1) Colloidal silica (average primary particle size 34 nm, average secondary particle size 70 nm, silanol group density 5.71 groups / nm², aspect ratio 1.19) was added as abrasive particles at a content of 0.5% by mass relative to the entire grinding composition, and hydrogen peroxide was added as an oxidant at a content of 0.16% by mass. These components were mixed in pure water by stirring (mixing temperature: approximately 25°C, mixing time: approximately 10 minutes). The pH was adjusted to 9.2 using ammonia as a pH adjuster to prepare the grinding composition.

[0088] (Comparative Example 2) Abrasive silica (average primary particle size 34 nm, average secondary particle size 70 nm, silanol group density 5.71 groups / nm², aspect ratio 1.19) was added at 0.5% by mass as abrasive particles, ammonium sulfate at 0.1% by mass as an inorganic salt, and hydrogen peroxide at 0.16% by mass as an oxidant. These components were mixed in pure water by stirring (mixing temperature: approximately 25°C, mixing time: approximately 10 minutes). The pH was adjusted to 9.2 using ammonia as a pH adjuster to prepare the abrasive composition.

[0089] (Comparative Example 3) Except that the pH value was adjusted to 10.4, the grinding composition was prepared in the same manner as in Comparative Example 2.

[0090] (Comparative Example 4) Abrasive silica (average primary particle size 34 nm, average secondary particle size 70 nm, silanol group density 5.71 groups / nm², aspect ratio 1.19) was added at 0.5% by mass as abrasive particles, potassium sulfate at 0.1% by mass as an inorganic salt, and hydrogen peroxide at 0.16% by mass as an oxidant. These components were mixed in pure water by stirring (mixing temperature: approximately 25°C, mixing time: approximately 10 minutes). The pH was adjusted to 10.4 using ammonia as a pH adjuster to prepare the abrasive composition.

[0091] (Comparative Example 5) Colloidal silica (average primary particle size 29 nm, average secondary particle size 61 nm, silanol group density 1.50 units / nm², aspect ratio 1.55) was added as abrasive particles at a content of 0.5% by mass relative to the entire grinding composition, and hydrogen peroxide was added as an oxidant at a content of 0.16% by mass. These components were stirred and mixed in pure water (mixing temperature: approximately 25°C, mixing time: approximately 10 minutes). The pH was adjusted to 10.4 using ammonia as a pH adjuster to prepare the grinding composition.

[0092] (Comparative Example 6) Except that the content of colloidal silicon dioxide was changed to 4.0% by mass, the grinding composition was prepared in the same manner as in Comparative Example 5.

[0093] [Determination of pH value of grinding composition] The pH value of grinding composition (liquid temperature: 25°C) was determined by pH meter (manufactured by Horiba Manufacturing Co., Ltd., model: LAQUA).

[0094] [Determination of average primary particle size and average secondary particle size] The average primary particle size of the abrasive particles was calculated based on the specific surface area and density of the abrasive particles measured by the BET method using the "Flow Sorb II 2300" manufactured by Micromeritics.

[0095] The average secondary particle size of the abrasive particles was measured using a dynamic light scattering particle size / particle size distribution device UPA-UTI151 manufactured by Nikkiso Co., Ltd.

[0096] [Determination of Silanol Density] The number of silanol groups per unit surface area of ​​the abrasive particles (silanol density) was calculated using the Sears method of neutralization titration, as described in GW Sears' Analytical Chemistry, vol.28, No.12, 1956, 1982-1983. The number of silanol groups was calculated using the following formula.

[0097] [Number 2] ρ: Silanol number [number / nm2] c: Concentration of sodium hydroxide solution used for titration [mol / L] a: Volume of sodium hydroxide solution added at pH 4-9 [ml] NA: Avogadro number (6.022×1023 [number / mol]), C: Mass of silicon dioxide [g] S: BET specific surface area [nm2 / g]

[0098] The composition of the grinding composition prepared above is shown in Table 1.

[0099] [Table 1] Table 1 Grinding composition abrasive particles Inorganic salts Oxidizing agent Grinding accelerator pH adjuster pH value Average primary particle size [nm] Average secondary particle size [nm] Silane alcohol density [units / nm] 2 ] concentration [quality%] type concentration [quality%] type concentration [quality%] type concentration [quality%] type Example 1 29 61 1.50 0.5 ammonium sulfate 0.1 hydrogen peroxide 0.16 - - ammonia 10.4 Example 2 29 61 1.50 0.5 Triammonium phosphate 0.1 hydrogen peroxide 0.16 - - ammonia 10.4 Example 3 29 61 1.50 1.0 ammonium sulfate 0.1 hydrogen peroxide 0.16 - - ammonia 10.4 Example 4 29 61 1.50 0.5 ammonium sulfate 0.2 hydrogen peroxide 0.16 - - ammonia 10.4 Example 5 29 61 1.50 0.5 ammonium sulfate 0.1 hydrogen peroxide 0.16 - - ammonia 9.2 Example 6 29 61 1.50 0.5 ammonium sulfate 0.1 hydrogen peroxide 0.40 - - ammonia 10.4 Example 7 29 61 1.50 0.5 ammonium sulfate 0.1 hydrogen peroxide 0.16 EDTMP 0.1 ammonia 10.4 Example 8 29 61 1.50 0.5 Triammonium phosphate 0.1 hydrogen peroxide 0-16 PBTC 0.1 ammonia 9.2 Comparative Example 1 34 70 5.71 0.5 - - hydrogen peroxide 0.16 - - ammonia 9.2 Comparative Example 2 34 70 5.71 0.5 ammonium sulfate 0.1 hydrogen peroxide 0.16 - - ammonia 9.2 Comparative Example 3 34 70 5.71 0.5 ammonium sulfate 0.1 hydrogen peroxide 0.16 - - ammonia 10.4 Comparative Example 4 34 70 5.71 0.5 potassium sulfate 0.1 hydrogen peroxide 0.16 - - potassium hydroxide 10.4 Comparative Example 5 29 61 1.50 0.5 - - hydrogen peroxide 0.16 - - ammonia 10.4 Comparative Example 6 29 61 1.50 4.0 - - hydrogen peroxide 0.16 - - ammonia 10.4 EDTMP: N,N,N',N'-ethylenediaminetetra(methylenephosphonic acid) PBTC: 2-phosphatidylbutane-1,2,4-tricarboxylic acid

[0100] [Grinding Speed] The following wafers are prepared as grinding objects: Silicon-germanium (SiGe) wafer: A silicon wafer (300 mm, unpatterned wafer, manufactured by Advanced Materials Technologies Inc.) with a silicon-germanium film with a thickness of 1500 Å formed on its surface. Silicon oxide (TEOS) wafer: A silicon wafer (300 mm, unpatterned wafer, manufactured by Advantech Inc.) with a silicon oxide film with a thickness of 10000 Å formed on its surface. Silicon nitride (SiN) wafer: A silicon wafer (300 mm, unpatterned wafer, manufactured by Advantech Inc.) with a silicon nitride film with a thickness of 3500 Å formed on its surface.

[0101] For silicon-germanium wafers, silicon oxide wafers, and silicon nitride wafers, the polishing compositions of Examples 1-8 and Comparative Examples 1-6 were used to polish for a fixed time under the polishing conditions shown in Table 2 below, and the polishing speed was determined at that time. The silicon-germanium wafers, silicon oxide wafers, and silicon nitride wafers were used by cutting a 300 mm substrate into 60 mm × 60 mm pieces.

[0102] [Table 2] Table 2 (Grinding Apparatus and Grinding Conditions) Grinding Apparatus: Single-sided CMP grinder, model EJ380IN (manufactured by Engels Inc., Japan) Grinding Pad: Trade name H804-CZM (manufactured by Fuji Spinning Ehime Co., Ltd.) Grinding Pressure: 1.8 psi (1 psi = 6894.76 Pa) Platen (Plate) Rotation Speed: 93 rpm Grinding Head (Carrier) Rotation Speed: 50 rpm Supply of Grinding Composition: Flowing grinding composition supply rate: 100 mL / min Grinding Time: 60 sec

[0103] Grinding speed (grinding rate) is calculated by the following formula.

[0104] [Number 3]

[0105] The film thickness of silicon oxide and silicon nitride was determined using an optical interferometric film thickness measuring device, Lambda ACE VM-2030, manufactured by SCREEN Semiconductor Solutions Inc. The difference in film thickness before and after grinding was divided by the grinding time for evaluation.

[0106] The thickness of silicon-germanium film was determined using a scanning fluorescence X-ray analysis device ZSX Primus 400 manufactured by Rigaku Corporation. The difference in film thickness before and after grinding was divided by the grinding time for evaluation.

[0107] The selection ratio of grinding speed is determined by calculating the grinding speed of germanium silicon / the grinding speed of silicon oxide, and the grinding speed of germanium silicon / the grinding speed of silicon nitride respectively.

[0108] [Etching Amount] A silicon-germanium wafer (Si:Ge = 50:50 mass ratio) with a size of 30 mm × 30 mm was immersed in a polishing composition that was rotated at 300 rpm by a stir bar at 43°C for 1 hour. The amount of dissolution (etching amount) was calculated based on the difference in film thickness before and after immersion.

[0109] The evaluation results are shown in Table 3 below.

[0110] [Table 3] Table 3 Grinding speed [Å / min] Grinding speed selectivity SiGe Etching amount [Å] SiGe SiN TEOS SiGe / SiN SiGe / TEOS Example 1 407 15 31 27.1 13.1 52 Example 2 387 18 29 21.5 13.4 55 Example 3 814 twenty four 48 33.9 17.0 60 Example 4 801 twenty two 51 36.4 15.7 75 Example 5 316 12 twenty three 26.3 13.7 47 Example 6 574 19 35 30.2 16.6 73 Example 7 1020 27 43 37.8 23.7 20 Example 8 613 12 32 51.1 19.2 twenty four Comparative Example 1 25 2 2 14.8 12.4 twenty three Comparative Example 2 155 5 5 29.1 31.0 twenty three Comparative Example 3 274 14 30 19.5 9.1 52 Comparative Example 4 164 15 32 11.0 5.1 52 Comparative Example 5 37 2 2 14.9 16.7 twenty three Comparative Example 6 232 63 74 3.7 3.1 25

[0111] As can be seen from Table 3 above, the grinding speed of the silicon-germanium in the grinding composition of the examples is sufficiently fast compared to the grinding composition of the comparative examples. Furthermore, it can be seen that the ratio (selectivity ratio) of the grinding speed of silicon-germanium to the grinding speed of silicon oxide or silicon nitride is also sufficiently high.

[0112] This application is based on Japanese Patent Application No. 2020-158993, filed on September 23, 2020, the entire contents of which are disclosed herein are incorporated by reference.

Claims

1. A grinding composition comprising abrasive particles, an inorganic salt, and an oxidizing agent, wherein the abrasive particles comprise colloidal silicon dioxide, the number of silanol groups per unit surface area of ​​the abrasive particles is more than 0 / nm² and less than 2.0 / nm², the inorganic salt is selected from at least one of the group consisting of ammonium sulfate, ammonium bisulfate, triammonium phosphate, diammonium hydrogen phosphate, and ammonium dihydrogen phosphate, the oxidizing agent is selected from at least one of the group consisting of hydrogen peroxide, sodium peroxide, barium peroxide, ozone water, permanganic acid, chromic acid, dichromic acid, peroxydisulfuric acid, peroxyphosphoric acid, peroxysulfuric acid, peroxyboric acid, performic acid, peracetic acid, perbenzoic acid, perphthalic acid, persulfuric acid, and salts thereof, the content of the oxidizing agent is 0.001% by mass or more and 5% by mass or less, the grinding composition is used for grinding abrasive objects containing silicon and germanium, and the pH value is 6.0 or more.

2. The grinding composition of claim 1, wherein the inorganic salt is ammonium sulfate.

3. The grinding composition of claim 1 or 2, wherein the oxidant is hydrogen peroxide.

4. The grinding composition of claim 1 or 2 further comprises a grinding accelerator.

5. The grinding composition of claim 4, wherein the grinding accelerator is selected from at least one of the group consisting of N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid, N,N,N',N'-ethylenediaminetetra(methylenephosphonic acid), 2-phosphatidylbutane-1,2,4-tricarboxylic acid, N,N-bis(2-hydroxyethyl)glycine, aspartic acid, and (S,S)-ethylenediamine-N,N'-disuccinic acid.

6. A grinding method comprising the step of grinding an object to be ground using a grinding composition as claimed in any one of claims 1 to 5.

7. A method for manufacturing a semiconductor substrate, comprising the step of polishing the semiconductor substrate by a polishing method as described in claim 6.