TW201522596A - Polishing composition, polishing method, and method for producing substrate - Google Patents

Abstract

A polishing composition according to the present invention can be used for polishing an object of interest having a polysilicon-containing layer, comprises abrasives grain and an oxidizing agent, and has a pH value of 6 or more. It is preferred that colloidal silica is used as the abrasive grains. A polishing method according to the present invention is characterized by polishing an object of interest having a polysilicon-containing layer using the polishing composition. A substrate production method according to the present invention is characterized by comprising a polishing step of polishing a substrate having a polysilicon-containing layer by the polishing method.

Description

Polishing composition, polishing method, and method of manufacturing substrate

The present invention relates to a polishing composition for use in polishing an object to be polished, the object to be polished having a layer containing polycrystalline germanium, a polishing method, and a method for producing a substrate.

In the production of semiconductor devices which have been miniaturized and densified in recent years, very fine pattern forming techniques have been used. Due to factors such as multilayering of wiring, the surface structure of the semiconductor device becomes more complicated, and the initial step difference of the surface film also becomes larger. As a wide-area planarization technique for removing an initial step difference of a specific film formed on a substrate, a chemical mechanical polishing (CMP) step is used. In the CMP having a polishing target of a polycrystalline germanium film, there is a polishing composition using polycrystalline germanium.

When the polycrystalline germanium film having the initial step difference of X(Å) is polished at a polishing rate of V (Å/min), if only the upper portion (upper portion of the convex portion) of the step region can be selectively polished, X/ V (minute) grinding time can go In addition to the step difference. However, actually, the lower side portion (the bottom portion of the concave portion) of the step region is lower than the upper portion (the upper portion of the convex portion) of the same region due to the chemical etching in the CMP step, the bending of the polishing pad, and the like. But it will also be ground.

For the polishing composition for polycrystalline silicon, it is required to make the step elimination efficiency defined below close to 1, that is, to polish the upper side of the step portion (above the convex portion) as much as possible. The step elimination efficiency is a difference (Å) between the pre-grinding and the post-grinding of the step on a certain surface of the object to be polished when only the surface of the object to be polished of a specific thickness is polished (that is, the step caused by the grinding) The amount of elimination (Å) is divided by the value of the aforementioned specific thickness (Å). Further, when the step is formed by the adjacent convex portion and the concave portion, it may be referred to as the distance from the lowest portion of the concave portion to the highest portion of the convex portion. At this time, the specific thickness is equivalent to the difference between the height position of the highest portion of the convex portion before the polishing and the height position of the highest portion of the convex portion after the polishing.

Patent Document 1 discloses a polishing composition used for polishing a polycrystalline silicon film. The polishing composition of Patent Document 1 contains citric acid gel as an abrasive grain, tetramethylammonium hydroxide (TMAH) as a base, hydroxyethylcellulose as a water-soluble polymer, water, or the like.

[Previous Technical Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2004-266155

Further, the polishing composition of Patent Document 1 has a problem that the required performance regarding the polishing characteristics of the polycrystalline silicon, particularly the step elimination efficiency, has not been sufficiently satisfied.

An object of the present invention is to provide a polishing composition which is more suitable for use in polishing an object to be polished having a layer containing polycrystalline germanium, and a polishing method using the polishing composition and a method for producing a substrate.

In order to achieve the above object, in one aspect of the invention, there is provided a polishing composition characterized by being used for polishing an object to be polished, the object to be polished having a layer containing polycrystalline germanium, and the composition for polishing The material contains abrasive grains and an oxidizing agent, and has a pH of 6 or more.

The aforementioned abrasive particles are preferably citric acid gel. The average primary particle diameter of the abrasive grains is preferably 5 nm to 400 nm. The above oxidizing agent is preferably a peroxide. The polishing composition further contains at least one compound selected from the group consisting of a saccharide, a water-soluble polymer, and a surfactant, and a molecular weight of 100 or more. The object to be polished may also have a step on the surface. In the polishing composition, when the surface of the object to be polished having the step is polished under the polishing conditions of a polishing pressure of 15.2 kPa and a number of revolutions of 93 rpm, the step elimination efficiency at this time is preferably 0.4 or more.

Moreover, in another aspect of the present invention, a grinding method is provided, It is characterized in that the object to be polished is polished by using the polishing composition, and the object to be polished has a layer containing polycrystalline germanium. Further, in still another aspect of the present invention, a method of manufacturing a substrate comprising a polishing step of polishing a substrate having a layer containing polycrystalline germanium by the polishing method is provided.

According to the present invention, it is possible to provide a polishing composition which is suitable for use in polishing an object to be polished, the object to be polished having a layer containing polycrystalline germanium.

[Formation of the Invention]

Hereinafter, an embodiment of the present invention will be described.

The polishing composition of the present embodiment is produced by mixing abrasive grains and an oxidizing agent, or the like, alone or in combination with other components, and then mixing them in water. The pH of the polishing composition thus obtained can be adjusted to a desired value of 6 or more by using a pH adjuster if necessary. The other component is preferably one having a molecular weight of 100 or more and at least one selected from the group consisting of a saccharide, a water-soluble polymer, and a surfactant. This polishing composition is used for polishing an object to be polished, and the object to be polished has a layer containing polycrystalline germanium.

Specific examples of the abrasive grains include cerium oxide, aluminum oxide, cerium oxide, zirconium oxide, titanium oxide, manganese oxide, cerium carbide, and cerium nitride. Among them, cerium oxide is preferred, and ceric acid or gas phase cerium oxide is more preferred. use In the case of such abrasive grains, a smoother polished surface can be obtained. The abrasive grains may be used singly or in combination of two or more.

When the citric acid gel is used, it may be any of a non-modified citric acid gel and a surface-modified phthalic acid gel. As the surface-modified citric acid gel, for example, a citric acid gel having an organic acid such as a sulfonic acid or a carboxylic acid immobilized on the surface, or a phthalic acid gel having a surface substituted with a metal oxide such as alumina may be used. The immobilization of the organic acid of the citric acid gel is carried out by chemically bonding the functional groups of the organic acid on the surface of the phthalic acid gel. The fixation of the sulfonic acid of the citric acid gel can be carried out, for example, by the method described in "Sulfonic acid-functionalized silica through quantitative oxidation of thiol groups", Chem. Commun. 246-247 (2003). Specifically, after coupling a decane coupling agent having a hydrogenthio group such as 3-hydrothiopropyltrimethoxydecane to a citric acid gel, sulfonate can be obtained by hydrogen peroxide to sulfonate the surface. Acidic acid gel. The immobilization of the carboxylic acid of the citric acid gum can be as described in, for example, "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). The method is carried out. Specifically, after coupling a decane coupling agent containing a photoreactive 2-nitrobenzyl ester to a citric acid gel, it is possible to obtain a citric acid gel having a carboxylic acid immobilized on the surface by light irradiation. Further, the substitution of the surface of the phthalic acid gel of alumina is carried out by adding and reacting an aluminum compound into the phthalic acid gel as described in JP-A-6-199515. Specifically, by adding an aluminate base to the citric acid gel and heating, a citric acid gel whose surface is substituted with alumina can be obtained.

The average primary particle diameter of the abrasive grains contained in the polishing composition is preferably 5 nm or more, more preferably 10 nm or more. As the average primary particle diameter of the abrasive grains increases, the polishing rate of the object to be polished by the polishing composition increases. Further, when the object to be polished having a stepped surface is polished, the step difference is more effectively eliminated.

The average primary particle diameter of the abrasive grains contained in the polishing composition is preferably 400 nm or less, more preferably 300 nm or less, still more preferably 200 nm or less. As the average primary particle diameter of the abrasive grains becomes smaller, it is easy to obtain a polished surface having a low defect and a small thickness.

Further, the average primary particle diameter of the abrasive grains can be calculated from the measured value of the specific surface area of the abrasive grains obtained by the nitrogen adsorption method (BET method).

The average secondary particle diameter of the abrasive grains is preferably 10 nm or more, more preferably 15 nm or more, and still more preferably 20 nm or more. Further, the average secondary particle diameter of the abrasive grains is preferably 450 nm or less, more preferably 350 nm or less, and still more preferably 220 nm or less. When the value of the average secondary particle diameter of the abrasive grains is within such a range, the polishing rate of the object to be polished by the polishing composition can be further improved, and when the polishing composition is used for polishing, it can be suppressed more. At this time, the occurrence of surface defects on the surface of the object is polished. In addition, the term "secondary particle" as used herein means that the abrasive grains are aggregated in the polishing composition, and the average secondary particle diameter of the abrasive particles can be measured by, for example, dynamic light scattering.

The content of the abrasive grains in the polishing composition is preferably 0.1% by mass or more, more preferably 1% by mass or more. As the content of the abrasive grains increases, the polishing rate of the object to be polished by the polishing composition is further increased. Rise.

The content of the abrasive grains in the polishing composition is preferably 50% by mass or less, more preferably 40% by mass or less. As the content of the abrasive grains is reduced, in addition to the reduction in the production cost of the polishing composition, it is easy to obtain a surface having less defects obtained by polishing using the polishing composition. Further, as the content of the abrasive grains is reduced, the amount of the abrasive grains remaining on the surface after polishing is also lowered, and as a result, the washing and removing property of the residual abrasive grains is improved. Further, when the object to be polished having a stepped surface is polished, the step difference is more effectively eliminated.

The oxidizing agent contained in the polishing composition is subjected to chemical polishing of the surface of the polycrystalline silicon of the object to be polished in a pH range of 6 or more. In particular, it contributes to the elimination of the step difference when polishing an object to be polished having a step. Specific examples of the oxidizing agent include peroxide, periodic acid, periodate, permanganate, vanadate, hypochlorite, iron oxide, ozone, and the like. Specific examples of the peroxide include hydrogen peroxide, peracetic acid, percarbonate, urea peroxide, perchloric acid, perchlorate, and persulfate such as sodium persulfate, potassium persulfate, and ammonium persulfate. Wait. Among them, persulfate and hydrogen peroxide are preferred from the viewpoint of polishing rate, and hydrogen peroxide is particularly preferable from the viewpoint of stability in an aqueous solution and environmental burden. The oxidizing agent may be used alone or in combination of two or more.

The content of the oxidizing agent in the polishing composition is preferably 0.01% by mass or more, more preferably 0.03% by mass or more. As the content of the oxidizing agent increases, the defects of the polished surface obtained by the polishing composition are suppressed. Moreover, when grinding an object having a step difference, the step difference is more efficiently eliminate.

The content of the oxidizing agent in the polishing composition is preferably 15% by mass or less, more preferably 10% by mass or less. As the content of the oxidizing agent is reduced, the manufacturing cost of the polishing composition can be reduced, and the processing of the used polishing composition, that is, the burden of the waste liquid treatment, can be reduced. Further, when the object to be polished having a step is polished, the step is more effectively eliminated.

The polishing composition has a pH of 6 or more. The pH of the polishing composition is preferably 7 or more, more preferably 8 or more. The upper limit of the pH of the polishing composition is not particularly limited, but is preferably less than 12. By setting the pH of the polishing composition to such a weak acid to alkaline range, the polishing characteristics of the polycrystalline silicon produced by the polishing composition can be improved, specifically, the polishing rate of the polycrystalline silicon. Further, when the object to be polished having a step is polished, the step is more effectively eliminated.

The pH adjuster used for the adjustment of the pH of the polishing composition can be selected from conventional acids, bases or such salts.

Specific examples of the acid which can be used as the pH adjuster include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, and phosphoric acid, or formic acid, acetic acid, propionic acid, and butyl. Acid, valeric acid, methyl 2-butyrate, n-hexanoic acid, methyl 3,3-dibutyrate, ethyl 2-butyrate, 4-methylpentanoic acid, n-heptanoic acid, 2-methyl Caproic acid, n-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, horse Acid, phthalic acid, malic acid, tartaric acid, citric acid, lactic acid, glycolic acid, 2-furan An organic acid such as a carboxylic acid, 2,5-furandicarboxylic acid, 3-furancarboxylic acid, 2-tetrahydrofurancarboxylic acid, methoxyacetic acid, methoxyphenylacetic acid or phenoxyacetic acid. The acid may be used singly or in combination of two or more.

Specific examples of the base which can be used as the pH adjuster include an alkali metal hydroxide or a salt thereof, an alkaline earth metal hydroxide or a salt thereof, a quaternary ammonium hydroxide or a salt thereof, ammonia, and an amine. Wait. Specific examples of the alkali metal include potassium, sodium, and the like. Specific examples of the salt include a carbonate, a hydrogencarbonate, a sulfate, an acetate, and the like. Specific examples of the fourth-order ammonium hydroxide include tetramethylammonium hydroxide, tetramethylammonium hydroxide, and tetraethylammonium hydroxide. Specific examples of the amine include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N-(β-aminoethyl)ethanolamine, and hexa Methyldiamine, diethylenetriamine, triethylenetetramine, anhydrous piperazine, piperazine hexahydrate, 1-(2-aminoethyl)piperazine, N-methylpiperazine, anthracene, and the like. The bases may be used alone or in combination of two or more.

Among them, ammonia, an ammonium salt, an alkali metal hydroxide, an alkali metal salt, and a quaternary ammonium hydroxide compound are preferred as the base. More preferred are ammonia, potassium compounds, sodium hydroxide, quaternary ammonium hydroxide compounds, ammonium hydrogencarbonate, ammonium carbonate, sodium hydrogencarbonate, and sodium carbonate. More preferably, it is a potassium compound. Examples of the potassium compound include potassium hydroxide or a salt, and specific examples thereof include potassium hydroxide, potassium carbonate, potassium hydrogencarbonate, potassium sulfate, potassium acetate, and potassium chloride.

A salt such as an ammonium salt or an alkali metal salt described above may be used in place of or in combination with the above acid.

As described previously, the polishing composition may also contain a molecular weight of 100. It is at least one compound selected from the group consisting of a saccharide, a water-soluble polymer, and a surfactant. By including the related compound, the step elimination efficiency by the polishing composition can be further improved. Hereinafter, this compound is also referred to as a step elimination aid in convenience. The step-removal aid has a function of imparting hydrophilicity to the surface of the polycrystalline silicon after polishing, and has a function of improving the washing and removing property of foreign matter such as dirt adhering to the surface after polishing.

The term "saccharide" as used herein means a carbohydrate other than the water-soluble polymer to be described later, and specifically means a monosaccharide, a disaccharide, an oligosaccharide, and the like. Specific examples of the monosaccharide include a pentose sugar such as a four-carbon sugar, a pentose sugar such as ribose, xylose or arabinose, a hexose such as glucose, galactose, mannose or fructose, or a seven-carbon sugar. Heptose and so on. Specific examples of the disaccharide include trehalose, maltose (maltose), lactose (Lactose), invert sugar (sucrose), cellobiose, latex sugar, isomaltulose, and the like. Specific examples of the oligosaccharide include raffinose, gentiotriose, raffinose, fucosyllactose, sialyllactose, maltotriose, cellotriose, glucosyl trehalose, and the like. The third sugar and the four sugars such as stachyose, lactic acid-N-tetrasaccharide, and maltotetraose. The oligosaccharide obtained by the reaction of aldehydes can be mainly used. Specific examples of such oligosaccharides include xylooligosaccharides, oligofructose, lactic acid oligosaccharides, malto-oligosaccharides, isomalto-oligosaccharides, and inulin. Inulo-oligosaccharide, lactic acid invert sugar, lactulose oligosaccharide, agarooligosaccharide, and the like. Specific examples of the saccharide derivative include a sugar-reducing body and a sugar oxidant, and a compound such as a sugar, a glycoside, a sugar, and an amino acid to which a functional group is added, such as a cationized sugar. As a specific example of a derivative of a monosaccharide, there are An amine-based glucosamine or the like is added to the glucose. The saccharide may be used alone or in combination of two or more.

Specific examples of the water-soluble polymer include polysulfonic acids such as polycarboxylic acids, polycarboxylates, polycarboxylates, polyphosphonic acids, and polystyrenesulfonic acids, polysaccharides, and cellulose derivatives. A water-soluble polymer such as an ethylene oxide polymer, a vinyl polymer or a cationic polymer, and a copolymer, such as a salt or a derivative thereof. Specific examples of the polycarboxylic acid, the polycarboxylate, the polycarboxylate or the polycarboxylate include polyaspartic acid, polyglutamic acid, polylysine, polymalic acid, and polymethyl. Acrylic acid, ammonium polymethacrylate, polymethyl methacrylate, polymaleic acid, polymethylene succinic acid, polybutyric acid, poly(p-styrene carboxylic acid), polyacrylic acid, polyacrylamide , Amino polyacrylamide, polymethyl acrylate, polyethyl acrylate, ammonium polyacrylate, sodium polyacrylate, poly phthalic acid, ammonium polyamide, sodium polyamide, polyglyoxylic acid Wait. Specific examples of the polysaccharide include hepatic sugar, alginic acid, pectin, pectic acid, starch, amylose, amylopectin, cold weather, carterin, pullan, ancient gum, and sputum. Mannose, carrageenan, Damarin gum, Sanxian gum, etc. Specific examples of the cellulose derivative include carboxymethylcellulose and hydroxyethylcellulose. Specific examples of the vinyl polymer include polyvinyl alcohol, polyvinyl pyridine, polyvinyl pyrrolidone, and polyacrylaldehyde. Specific examples of the cationic polymer include a cationized cellulose derivative, a cationic starch, a cationized ancient gum derivative, a diallyl quaternary ammonium salt/acrylamide copolymer, and a four-stage polymerization. A polyvinylpyrrolidone derivative, a dicyandiamide-diethylenetriamine condensate. The water-soluble polymer may be used alone or in combination of two or more. use.

Specific examples of the surfactant include an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant.

The anionic surfactant is classified into, for example, a sulfuric acid type surfactant, a sulfonic acid type surfactant, a phosphate type surfactant, a phosphonic acid type surfactant, and a carboxylic acid type surfactant. Specific examples of the anionic surfactant include alkyl sulfate, polyoxyethylene alkyl sulfate, polyoxyethylene alkyl sulfate, alkyl sulfuric acid, alkyl ether sulfate, higher alcohol sulfate, and alkyl group. Phosphate ester, alkyl benzene sulfonate sulfonic acid, α-olefin sulfonic acid, alkyl sulfonic acid, polystyrene sulfonic acid, alkyl naphthalene sulfonic acid, alkyl diphenyl ether disulfonic acid, polyoxyethylene alkyl ether Acetic acid, polyoxyethylene alkyl ether phosphate, polyoxyethylene alkyl phosphate, polyoxyethylene sulfosuccinic acid, alkyl sulfosuccinic acid, or the like, a taurine surfactant, creatinine It is a surfactant, an isethionate surfactant, an N-mercapto acid amino acid surfactant, a higher fatty acid salt, a deuterated polypeptide, and the like. Specific examples of the alkylsulfonic acid or a salt thereof include dodecylsulfonic acid and dodecylsulfonate.

The cationic surfactant is classified into, for example, a polyoxyethylene alkylamine type surfactant, an alkyl alkanoate type surfactant, an alkylamine salt type surfactant, an amine oxide type surfactant, and a fourth stage. Ammonium salt type surfactant and tertiary guanamine type surfactant. Specific examples of the cationic surfactant include coconutamine acetate, stearylamine acetate, lauryl dimethylamine oxide, dimethylaminopropyl decylamine stearate, and alkyl trimethacrylate. Alkyl ammonium salt, alkyl dimethyl ammonium salt, alkyl dimethyl benzyl ammonium salt, and the like.

The amphoteric surfactant is classified into an alkylbenzyl base surfactant, an alkyl amine oxide surfactant, and the like. Specific examples of the amphoteric surfactant include cocoa base, lauryl propyl benzyl base, cocoamphetamine benzyl base, sodium lauroamphoacetate, cocoa succinic acid sodium acetate, and coconut oil decylamine. Propyl benzyl base, lauryl benzyl base (lauryl dimethylamine acetate benzyl base) and the like.

Specific examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether, sucrose fatty acid ester, sorbitan fatty acid ester, glycerin fatty acid ester, and polyoxyethylene fatty acid ester. , polyoxyethylene alkylamine, alkyl alkanolamine, and the like.

The surfactant may be used singly or in combination of two or more.

The molecular weight of the step elimination aid is preferably 100 or more, more preferably 200 or more, still more preferably 300 or more. When the molecular weight of the step elimination aid is 100 or more, the step elimination efficiency by the polishing composition is improved. The upper limit of the molecular weight of the step elimination aid is not particularly limited, but is preferably 500,000 or less, more preferably 400,000 or less, still more preferably 300,000 or less. When the molecular weight of the step elimination aid is 500,000 or less, the dispersibility of the step elimination aid in the aqueous solution is improved. Further, the molecular weight referred to herein is a mass average molecular weight when the step elimination aid is a polymer having a repeating structure of a single body. The measurement of the mass average molecular weight can be carried out by a conventional method, for example, by a GPC-MALS method. The mass average molecular weight of the water-soluble polymer having a relatively low molecular weight can also be determined by an NMR method.

In the polishing composition, the content of the step elimination aid is preferably 0.0001% by mass or more (1 ppm), more preferably 0.001% by mass (10 ppm) or more. As the content of the step elimination aid increases, the efficiency of the step elimination by the polishing composition is further improved.

In the polishing composition, the content of the step elimination aid is preferably 5% by mass or less, more preferably 0.5% by mass or less. As the content of the step elimination aid is reduced, the polishing rate by the polishing composition is further increased.

The polishing composition used in the present embodiment may further contain other additives as necessary insofar as the effects of the present invention are not impaired. Examples of other additives include a pH stabilizer (buffer), a dispersing medium or a solvent, a preservative, an antifungal agent, a rust preventive, a chelating agent, a dispersing agent for improving the dispersibility of the abrasive grains, and an easy abrasive grain. Agglomerate redispersible dispersing aids, etc.

The pH stabilizer may, for example, be a combination salt of a weak acid and a strong base, or a combination salt of a weak acid and a weak base. Specific examples of the pH stabilizer include potassium carbonate and the like.

The dispersing medium or solvent is used to disperse or dissolve each component in the polishing composition. The dispersing medium or solvent is preferably water. It is preferred to use water which is as free as possible from impurities, without damaging other components. Specific examples of such water include pure water or ultrapure water or distilled water obtained by removing impurity ions using an ion exchange resin and removing foreign matter through a sieve.

Specific examples of the preservative and the antifungal agent include 2-methyl-4-isothiazolin-3-one or 5-chloro-2-methyl-4-isothiazolin-3-one. Thiazole A porphyrin preservative, a paraben, a phenoxyethanol, or the like. The preservative and the antifungal agent may be used alone or in combination of two or more.

Next, the polishing method and the method of manufacturing the substrate of the present embodiment will be described.

In the polishing method and the method for producing a substrate of the present embodiment, the surface of the substrate having the layer containing polycrystalline germanium is polished using the polishing composition described above. At this time, the polycrystalline silicon can be polished well. In particular, when polishing a substrate having a step caused by multilayering of wiring or the like on the surface, the step can be effectively eliminated. As described above, when only the surface of the object to be polished of a specific thickness is polished, the difference (Å) between the grinding before and after the grinding of the step on the surface of the object is divided by the specific thickness (Å). The step difference elimination efficiency of the value is closer to 1, and the upper side portion (above the convex portion) indicating the region of the step can more effectively eliminate the step difference by selective grinding. The step elimination efficiency is preferably 0.4 or more, more preferably 0.5 or more, under the polishing conditions of a polishing pressure of 15.2 kPa and a plate rotation number of 93 rpm.

The reason why the step on the polycrystalline germanium film can be efficiently removed by using the polishing composition of the present embodiment is not clear, but it is presumed as follows. In general, in the pH range from weakly acidic to alkaline, since the dissolution of polycrystalline germanium occurs, not only the upper portion of the region of the step (above the convex portion) but also the lower portion of the same region (the bottom of the concave portion) It will continue to be removed, so the result is that the efficiency of the step elimination is low. However, since the polycrystalline ruthenium film is oxidized by the oxidizing agent in the polishing composition, it is hard to be dissolved even in a pH range from weakly acidic to basic. And think that this is by making According to the polishing composition of the present embodiment, the reason for the step elimination efficiency can be improved.

Further, when a stepwise elimination aid having a molecular weight of 100 or more and at least one compound selected from the group consisting of a saccharide, a water-soluble polymer, and a surfactant is added, the step elimination aid is adsorbed by hydrogen bonding or hydrophobic interaction. On the oxidized portion of the polysilicon, a protective film is thereby formed. As a result, it is possible to further prevent the lower portion (the bottom portion of the concave portion) of the region of the step from being dissolved and removed. Therefore, the step elimination efficiency obtained by the polishing composition is further improved by using the step elimination aid.

Moreover, the mechanism for eliminating the above-described step difference is presumed, and the present invention is not limited to any of the above mechanisms.

According to the above embodiment, the following effects can be obtained.

(1) By using the polishing composition of the above embodiment, the polycrystalline silicon can be polished well. Specifically, when the layer containing polycrystalline germanium is polished by using the polishing composition of the above embodiment, a high polycrystalline silicon removal rate can be obtained, and the step on the surface of the layer containing the polycrystalline germanium can be efficiently eliminated. Therefore, the polishing composition of the above embodiment can be suitably used for the purpose of polishing a layer containing polycrystalline germanium, and is particularly suitable for use in polishing and removing a step on the surface of a layer containing polycrystalline germanium.

(2) When the polishing composition of the above embodiment contains the step elimination aid, the step elimination efficiency can be further improved.

Further, the above embodiment may be modified as follows.

. The polishing composition of the above embodiment can also be diluted by water The grinding is prepared using a stock solution of the composition.

. The object to be polished which is polished by using the polishing composition of the above embodiment may have a layer other than polycrystalline silicon as long as it has a layer containing polycrystalline germanium.

. The polishing composition of the above embodiment may be prepared by supplying a component of the polishing composition other than the oxidizing agent and the polishing composition to a polishing apparatus, and mixing them in a polishing apparatus. The components of the polishing composition other than the oxidizing agent and the polishing composition may be mixed in the polishing composition supply tank attached to the polishing apparatus.

. The surface of the object to be polished which is polished by using the polishing composition of the above embodiment may be flat or have a step. The size of the step is not particularly limited as long as it is a step of the same size as that generated by the pattern forming technique of a general semiconductor device. The polishing composition can be used for polishing an object to be polished having a step of, for example, 100 Å or more and further 1000 Å or more on the surface.

[Examples]

Next, the present invention will be further specifically described by way of examples and comparative examples.

In Examples 1 to 9, after adding a pH adjuster and water to the abrasive grains, an oxidizing agent was further added to prepare a polishing composition. In Examples 10 to 20, after adding a pH adjuster and water to the abrasive grains, an oxidizing agent and a step elimination aid or other additives were added to prepare a polishing composition. in In Comparative Examples 1 to 5, a pH adjuster and water were added to the abrasive grains to prepare a polishing composition. The results of the detailed components in the polishing compositions of the examples and the pH values of the polishing compositions of the respective examples are shown in Table 1.

In Table 1, A represents a tannic acid gel having an average primary particle diameter of 30 nm and an average secondary particle diameter of 62 nm, and B represents a tannic acid gel having an average primary particle diameter of 10 nm and an average secondary particle diameter of 25 nm, and C represents A tannic acid gel having an average primary particle diameter of 90 nm and an average secondary particle diameter of 180 nm.

The molecular weight in Table 1 indicates the mass average molecular weight of the step-eliminating aid or other additive when it is a polymer having a repeating structure of a monomer.

The column of "grinding rate of polycrystalline tantalum film" in Table 1 shows the rate of polysilicon removal when a polycrystalline tantalum film having a diameter of 200 mm was coated on the surface of the wafer by using the polishing composition of each example under the conditions shown in Table 2. The value of the removal rate of the polysilicon is: the difference in thickness of each substrate before and after the polishing measured by the light interference type film thickness measuring device "LAMBDA ACE VM-2030" manufactured by Dainippon SCREEN Co., Ltd., divided by the polishing time (60 seconds) Determined.

The column of "segment elimination efficiency" in Table 1 indicates that the surface of the polycrystalline ruthenium pattern wafer having a diameter of 200 mm and an initial step of 2000 Å was used, and the polishing composition of each example was used, and only the conditions shown in Table 2 were used. The step difference elimination efficiency at a thickness of 1000 Å. The value of the step elimination efficiency is obtained by dividing the step difference (Å) of the difference between the initial step difference and the step remaining after the polishing by the thickness (Å) (1000 Å). In addition, the step difference was measured using an atomic force microscope (AFM).

As shown in Table 1, in Examples 1 to 9, the polishing rate of the polycrystalline silicon which can be practically satisfied can be obtained. Moreover, a higher step elimination efficiency can also be obtained. In Examples 10 to 19 in which the polishing composition containing the step difference eliminating aid was used, it was confirmed that the step elimination efficiency can be further improved. On the other hand, in Comparative Examples 1 and 2 in which the polishing composition having a pH of less than 6 was used, the polishing rate of polycrystalline silicon which was practically satisfactory could not be obtained. Further, in Comparative Examples 3 to 5 in which the polishing composition containing no oxidizing agent was used, there was a result that the step elimination efficiency was inferior.

Claims (10)

A polishing composition for use in polishing an object to be polished, the object to be polished having a layer containing polycrystalline germanium, and the polishing composition comprising abrasive grains and an oxidizing agent, and having a pH of 6 or more. The polishing composition according to claim 1, wherein the abrasive grains are citric acid gel. The polishing composition according to claim 1 or claim 2, wherein the abrasive particles have an average primary particle diameter of 5 nm to 400 nm. The polishing composition according to claim 1 or claim 2, wherein the oxidizing agent is a peroxide. The polishing composition according to claim 1 or claim 2, further comprising at least one compound selected from the group consisting of a saccharide, a water-soluble polymer, and a surfactant, having a molecular weight of 100 or more. The polishing composition according to claim 1 or claim 2, which further contains a hydroxide of an alkali metal as a pH adjuster. The polishing composition according to claim 1 or claim 2, wherein the polishing object has a step on the surface. The polishing composition according to claim 7, wherein when the surface of the object to be polished having the step is polished under the polishing conditions of a polishing pressure of 15.2 kPa and a number of rotations of the disk of 93 rpm, the step elimination efficiency at this time is 0.4 or more. A polishing method characterized by polishing an object to be polished using a polishing composition according to claim 1 or claim 2, the polishing object having a layer containing polycrystalline germanium. A method of manufacturing a substrate, comprising the step of polishing a substrate by a polishing method according to claim 9, the substrate having a layer comprising polycrystalline germanium.