JP7002354B2 - Polishing composition - Google Patents

Description

The present disclosure relates to a polishing composition, and more particularly to a polishing composition suitable for a silicon wafer.

Polishing of a silicon wafer by CMP (Chemical Mechanical Polishing) is performed in three or four stages, thereby achieving high-precision flattening. Especially in the final stage of finish polishing, a water-soluble polymer such as hydroxyethyl cellulose (HEC) is generally used as the slurry in order to reduce surface defects of the silicon wafer and impart wettability to the wafer surface. Has been done.

Japanese Patent No. 6029895 (Patent Document 1) has a weight average molecular weight of 1,000,000 or less and a molecular weight distribution represented by weight average molecular weight (Mw) / number average molecular weight (Mn) of 5.0 or more, 8.0 or more. Disclosed is a composition for polishing a silicon substrate, which can easily exhibit both the effect of increasing the polishing speed and the effect of increasing the wettability of the polished surface by containing the following water-soluble polymer. However, the publication makes no mention of its effect on surface defects (LPD) and surface roughness (haze).

WO2012 / 102144 (Patent Document 2) is a polishing composition containing a composition (A) containing hydroxyethyl cellulose, ammonia, abrasive grains and water, and at least one selected from an organic acid and an organic acid salt. The present invention discloses a polishing composition in which the electric conductivity of the polishing composition is 1.2 times or more and 8 times or less the electric conductivity of the composition (A). According to this polishing composition, by adding an organic acid to a polishing liquid containing hydroxyethyl cellulose (HEC), the electric conductivity is increased and the hydrophilicity of the polished surface is improved, but the haze of the substrate surface is deteriorated. There is. In addition, HEC having a large molecular weight has a small effect of reducing LPD and haze, and cannot sufficiently meet the recent demand level for surface quality after polishing. The publication does not mention any water-soluble polymers other than HEC (polyvinyl alcohol (PVA), carboxymethyl cellulose, etc.).

Japanese Patent No. 6029895 International Publication WO2012 / 102144 Gazette

An object of the present disclosure is to provide a polishing composition capable of sufficiently reducing LPD and haze.

The polishing composition according to the present embodiment includes abrasive grains, a basic compound, polyvinyl alcohols having a weight average molecular weight of 100,000 or less and a structural unit represented by the following chemical formula (1), or 100,000 or less. A water-soluble polymer containing polyglycerins having a weight average molecular weight and a structural unit represented by the following chemical formula (2), one or more selected from the group consisting of organic acids and organic acid salts, and water. including.

The polishing composition according to this embodiment can sufficiently reduce LPD and haze.

The polishing composition according to the present embodiment includes abrasive grains, a basic compound, polyvinyl alcohols having a weight average molecular weight of 100,000 or less and a structural unit represented by the following chemical formula (1), or 100,000 or less. A water-soluble polymer containing polyglycerins having a weight average molecular weight and a structural unit represented by the following chemical formula (2), one or more selected from the group consisting of organic acids and organic acid salts, and water. include.

Since the polishing composition according to the present embodiment contains a water-soluble polymer having a weight average molecular weight of 100,000 or less and an organic acid or an organic acid salt, the hydrophilicity of the wafer surface is improved, and the nano cannot be solved by HEC. The LPD and haze of the scale can be reduced.

The polishing composition may further contain a nonionic surfactant. By adding a nonionic surfactant as a subpolymer, LPD and haze can be further reduced while maintaining the hydrophilicity of the wafer surface.

As the abrasive grains, those commonly used in this field can be used. Abrasive grains are, for example, colloidal silica, fumed silica, colloidal alumina, fumed alumina, cerium oxide, silicon carbide, silicon nitride and the like. Of these, colloidal silica is preferably used.

The content of the abrasive grains is not particularly limited, but is, for example, 0.1 to 10% by weight of the entire polishing composition. The content of the abrasive grains is preferably high from the viewpoint of increasing the polishing speed, and preferably low from the viewpoint of reducing polishing scratches and foreign matter residue. The lower limit of the content of the abrasive grains is preferably 0.5% by weight, more preferably 1% by weight. The upper limit of the content of the abrasive grains is preferably 8% by weight, more preferably 5% by weight.

The basic compound etches the surface of the wafer and chemically polishes it. The basic compound is, for example, an amine compound, an inorganic alkaline compound, or the like.

The amine compound is, for example, a primary amine, a secondary amine, a tertiary amine, a quaternary ammonium and a salt thereof, a heterocyclic amine and the like. Specifically, ammonia, tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrabutylammonium hydroxide (TBAH), methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, hexylamine, Cyclohexylamine, ethylenediamine, hexamethylenediamine, diethylenetriamine (DETA), triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, monoethanolamine, diethanolamine, triethanolamine, N- (β-aminoethyl) ethanolamine, anhydrous piperazine , Piperazine hexahydrate, 1- (2-aminoethyl) piperazine, N-methylpiperazine, piperazine hydrochloride, guanidine carbonate and the like.

Examples of the inorganic alkaline compound include alkali metal hydroxides, alkali metal carbonates, alkali metal hydrogen carbonates, alkaline earth metal hydroxides, alkaline earth metal carbonates, and alkaline earth metal carbonates. Examples include hydrogen salts. Specific examples of the inorganic alkaline compound include potassium hydroxide (KOH), sodium hydroxide, potassium hydrogencarbonate, potassium carbonate (K2 CO ₃ ) _, sodium hydrogencarbonate, sodium carbonate and the like.

The above-mentioned basic compounds may be used alone or in combination of two or more. The total content of the basic compound is not particularly limited, but is, for example, 0.1 to 5% by weight of the entire polishing composition. The lower limit of the content of the basic compound is preferably 0.5% by weight. The upper limit of the content of the basic compound is preferably 3% by weight.

The water-soluble polymer is, for example, polyvinyl alcohol having a structural unit represented by the above chemical formula (1) in its molecular structure. Examples of polyvinyl alcohols include polyvinylpyrrolidone, polyvinylcaprolactam, polyvinylformamide, polyvinyl alcohol (PVA), modified PVA and the like.

The modified PVA has a 1,2-diol structural unit represented by the following chemical formula (3) in addition to the structural unit represented by the above chemical formula (1).

In the chemical formula (3), R ¹ , R ² , and R ³ independently represent a hydrogen atom or an organic group, X indicates a single bond or a bond chain, and R ⁴ , R ⁵ , and R ⁶ are independent, respectively. To indicate a hydrogen atom or an organic group.

Alternatively, the water-soluble polymer is a polyglycerin having a structural unit represented by the above chemical formula (2) in its molecular structure. Examples of polyglycerins include polyglycerin fatty acid esters and polyglycerin alkyl ethers. Examples of the polyglycerin fatty acid ester include polyglycerin lauric acid ester, polyglycerin caprylic acid ester, polyglycerin myristic acid ester, polyglycerin stearate ester, polyglycerin oleic acid ester and the like. Examples of the polyglycerin alkyl ether include polyglyceryl 4 lauryl ether and the like.

Polyglycerin may have a structural unit represented by the following chemical formula (4) in addition to the structural unit represented by the above chemical formula (2).

In the chemical formula (4), R represents a hydrogen atom or an organic group.

The water-soluble polymer may be blended alone or in combination of two or more. However, hydroxyethyl cellulose (HEC) is not included.

The organic acid is an organic compound containing carbon as a main component and has acidity, and is, for example, lactic acid, aminobutyric acid, apple acid, citric acid, or hydroxyproline.

The organic acid salt is a compound formed by binding an organic acid and a metal ion, and is, for example, ammonium acetate.

The organic acid or organic acid salt used in this embodiment forms a chelate complex with a 1- to tetravalent metal ion (potassium ion, sodium ion, calcium ion, iron ion, magnesium ion, nickel ion, etc.) to form a carboxylic acid. , Sodium carboxylate or phosphonic acid, and does not contain chelating agents containing tertiary amines. This is because when a chelating agent is added, the abrasive grains tend to aggregate.

Examples of the chelating agent not contained in the organic acid or the organic acid salt include ethylenediamine tetraacetic acid, ethylenediamine tetraacetate, nitrilo triacetic acid, sodium nitrilo triacetate, ammonium nitrilo triacetate, hydroxyethyl ethylenediamine triacetic acid, and hydroxyethyl ethylenediamine tri. Sodium acetate, diethylenetriaminepentaacetic acid, diethylenetriaminepentaacetate, triethylenetetraminehexacetic acid, triethylenetetraminehexaacetate, 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid) , Ethylenediaminetetrakis (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid), ethane-1,1,-diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid , Etan-1-hydroxy-1,1,2-triphosphonic acid, ethane-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1- Phosphonobtan-2,3,4-tricarboxylic acid, α-methylphosphonosuccinic acid and the like can be mentioned.

Examples of the nonionic surfactant include polyhydric alcohols. A polyhydric alcohol is an alcohol containing two or more hydroxy groups in one molecule. Examples of the polyhydric alcohol include glycosides (glycosidic bonds) in which sugars and organic compounds other than sugars are glycosidic bonded, glycerin and its derivatives (glycerin fatty acid ester, polyoxyalkylene polyglyceryl ether), propylene glycol, polyethylene glycol and the like. Can be mentioned. The polyhydric alcohol includes a polyhydric alcohol fatty acid ester in which a polyhydric alcohol such as a glycoside (glycoside), glycerin, propylene glycol, and polyethylene glycol is ester-bonded with a fatty acid, and a polyhydric alcohol to which an alkylene oxide is added. Valuable alcohol alkylene oxide adducts and the like are also included. Examples of the glycoside include an alkylene oxide derivative of methylglucoside (polyoxyalkylene methylglucoside) and the like.

Examples of the alkylene oxide derivative of methylglucoside (polyoxyalkylene methyl glucoside) include polyoxyethylene methyl glucoside and polyoxypropylene methyl glucoside. Among these compounds, polyoxypropylene methylglucoside is particularly suitable.

The weight average molecular weight of the polyhydric alcohol is not particularly limited, but is, for example, 100 to 30,000. The lower limit of the weight average molecular weight of the polyhydric alcohol is preferably 200, more preferably 500. The upper limit of the weight average molecular weight of the polyhydric alcohol is preferably 10,000, more preferably 1000. One type of polyhydric alcohol may be blended alone, or two or more kinds may be blended.

The content of the polyhydric alcohol is not particularly limited, but is, for example, 0.003 to 0.3% by weight of the entire polishing composition. The lower limit of the content of the polyhydric alcohol is preferably 0.005% by weight, more preferably 0.01% by weight. The upper limit of the content of the polyhydric alcohol is preferably 0.25% by weight, more preferably 0.15% by weight.

Examples of the glycerin derivative (glycerin fatty acid ester, polyoxyalkylene polyglyceryl ether) include diglycerin monocaprylate, polyoxypropylene polyglyceryl ether, polyoxyethylene polyglyceryl ether and the like. Among these compounds, polyoxyethylene polyglyceryl ether is particularly suitable.

The weight average molecular weight of the polyhydric alcohol is not particularly limited, but is, for example, 100 to 30,000. The lower limit of the weight average molecular weight of the polyhydric alcohol is preferably 200, more preferably 500. The upper limit of the weight average molecular weight of the polyhydric alcohol is preferably 10,000, more preferably 2000. One type of polyhydric alcohol may be blended alone, or two or more kinds may be blended.

The content of the polyhydric alcohol is not particularly limited, but is, for example, 0.003 to 0.3% by weight of the entire polishing composition. The lower limit of the content of the polyhydric alcohol is preferably 0.005% by weight, more preferably 0.05% by weight. The upper limit of the content of the polyhydric alcohol is preferably 0.25% by weight, more preferably 0.15% by weight.

Specific examples of the polyhydric alcohol include N, N, N', N'-tetrakis, polyoxyethylene, polyoxypropylene, ethylenediamine (poloxamine), poloxamer, polyalkylene glycol, polyoxyalkylene alkyl ether, and polyoxy. Examples thereof include alkylene fatty acid esters and polyoxyalkylene alkylamines.

Examples of the polyoxyalkylene alkyl ether include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, and polyoxyethylene stearyl ether. Examples of the polyoxyalkylene fatty acid ester include polyoxyethylene monolaurate and polyoxyethylene monostearate. Examples of the polyoxyalkylene alkylamine include polyoxyethylene laurylamine and polyoxyethylene oleylamine. The weight average molecular weight of the nonionic surfactant is not particularly limited, but is, for example, 1000 to 30,000. The lower limit of the weight average molecular weight of the nonionic surfactant is preferably 5000, more preferably 6000. The upper limit of the weight average molecular weight of the nonionic surfactant is preferably 10,000, more preferably 9000. The content of the nonionic surfactant is not particularly limited, but is, for example, 0.003 to 0.3% by weight of the entire polishing composition. The lower limit of the content of the nonionic surfactant is preferably 0.005% by weight, more preferably 0.01% by weight. The upper limit of the content of the nonionic surfactant is preferably 0.25% by weight, more preferably 0.15% by weight. The nonionic surfactant may be blended alone or in combination of two or more.

The polishing composition according to this embodiment may further contain a pH adjuster. Examples of the compound for adjusting the polishing composition to the basic side include the above-mentioned basic compounds. Examples of the compound for adjusting the polishing composition to the acidic side include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and the like. The pH of the polishing composition according to this embodiment is preferably 9.0 to 12.0.

In addition to the above, the polishing composition according to the present embodiment may optionally contain a compounding agent generally known in the field of polishing composition.

The polishing composition according to the present embodiment is prepared by appropriately mixing abrasive grains, a nonionic surfactant, and other compounding materials and adding water. The polishing composition according to the present embodiment is also prepared by sequentially mixing abrasive grains, nonionic surfactant silica, and other compounding materials with water. As a means for mixing these components, means commonly used in the technical field of polishing compositions such as homogenizers and ultrasonic waves are used.

The polishing composition described above is diluted with water to an appropriate concentration and then used for polishing a silicon wafer.

Hereinafter, in order to confirm the effect of this embodiment, the polishing compositions of Examples 1 to 15 and Comparative Examples 1 to 9 shown in Tables 1 to 5 are prepared, diluted 31-fold with ultrapure water, and polished. Evaluation was performed.

Examples 1 to 4 and Comparative Example 1 contain modified PVA as a water-soluble polymer. The modified PVA has a structural unit represented by the above chemical formula (1) and a 1,2-diol structural unit represented by the above chemical formula (3). However, in the chemical formula (3), R1 to R6 are all hydrogen atoms, and X is a single bond. The denaturation rate (= number of 1,2-diol structural units / total number of structural units) is 10% or less. The same applies to Examples 5 to 12 and Comparative Examples 2 and 3 described later.

In Comparative Example 1, 9.5% by weight of silica abrasive grains, 0.27% by weight of an aqueous ammonia solution, and 0.07% by weight of modified PVA as a water-soluble polymer (weight average molecular weight of 20,000; hereinafter the same). ), 0.01% by weight of polyhydric alcohol A (polyoxyethylene methyl glucoside) as a nonionic surfactant, and 0.01% by weight of polyhydric alcohol B (polyoxyethylene methyl glucoside) as a nonionic surfactant. Polyoxypropylene methyl glucoside) and. In Examples 1 to 3, ammonium acetate was added as an organic acid salt to Comparative Example 1. The contents of ammonium acetate in Examples 1 to 3 are 1.0% by weight, 0.1% by weight, and 0.02% by weight, respectively. In Example 4, 0.1% by weight of lactic acid was added as an organic acid to Comparative Example 1. The balance of each of the examples and comparative examples is water (hereinafter, the same applies).

In Comparative Example 2, 3.5% by weight of silica abrasive grains, 0.05% by weight of an aqueous ammonia solution, 0.05% by weight of modified PVA as a water-soluble polymer, and 0.05% by weight of a nonionic surfactant were used. 0.0075% by weight polyhydric alcohol B and 0.0113% by weight polyhydric alcohol D (poroxamine; N, N, N', N'-tetrax polyoxyethylene poly as a nonionic surfactant Oxypropylene / ethylenediamine) and included. On the other hand, in Examples 5 to 8, lactic acid, aminobutyric acid, malic acid, and hydroxyproline were added as organic acids instead of the polyhydric alcohol D to Comparative Example 2, respectively. The content of the organic acid of Examples 5 to 8 is 0.0113% by weight, which is the same as that of the polyhydric alcohol D of Comparative Example 2.

In Example 9, 0.0113% by weight of ammonium acetate was added as an organic acid salt to Comparative Example 2. In Examples 10 and 11, 0.0113% by weight of lactic acid and 0.0113% by weight of aminobutyric acid were added as organic acids to Comparative Example 2, respectively. Comparative Example 3 contains 9.5% by weight of silica abrasive grains, 0.17% by weight of an aqueous ammonia solution, 0.07% by weight of modified PVA as a water-soluble polymer, and a nonionic surfactant. It contains 0.01% by weight of polyhydric alcohol A, 0.01% by weight of polyhydric alcohol B, and 0.01% by weight of polyhydric alcohol C (polyoxyethylene polyglyceryl ether). In Example 12, 0.2% by weight of citric acid was added as an organic acid to Comparative Example 3.

Examples 13 to 15 and Comparative Examples 4 to 6 contain polyglycerin as a water-soluble polymer instead of modified PVA. Polyglycerin has a structural unit represented by the above chemical formula (2) and a structural unit represented by the above chemical formula (4). However, in the chemical formula (4), R is a hydrogen atom.

Comparative Example 4 shows 0.3% by weight of silica abrasive grains, 0.005% by weight of an aqueous ammonia solution, and 1.8% by weight of polyglycerin as a water-soluble polymer (manufactured by Sakamoto Yakuhin Kogyo Co., Ltd .: weight average). It contains 0.045% by weight of polyhydric alcohol B as a nonionic surfactant (molecular weight 2000). On the other hand, in Example 13, 0.045% by weight of aminobutyric acid was added as an organic acid to Comparative Example 4.

Comparative Example 5 contains 0.3% by weight of silica abrasive grains, 0.045% by weight of an aqueous ammonia solution, and 1.8% by weight of polyglycerin as a water-soluble polymer. However, Comparative Example 5 does not contain a surfactant (polyhydric alcohol). Comparative Example 6 is obtained by adding 0.045% by weight of the polyhydric alcohol B as a surfactant to Comparative Example 5.

On the other hand, in Example 14, 0.045% by weight of ammonium acetate was added as an organic acid salt to Comparative Example 5. In Example 15, 0.045% by weight of aminobutyric acid was added as an organic acid to Comparative Example 6.

Comparative Example 7 contains 3.5% by weight of silica abrasive grains, 0.05% by weight of an aqueous ammonia solution, and 0.05% by weight of HEC (weight average molecular weight: 1 million) as a water-soluble polymer. .. Comparative Example 8 is obtained by adding 0.0113% by weight of ammonium acetate as an organic acid salt to Comparative Example 7. Comparative Example 9 is obtained by adding 0.0113% by weight of lactic acid as an organic acid to Comparative Example 7.

Next, the polishing compositions of Examples 1 to 15 and Comparative Examples 1 to 9 were used, and polishing was performed under the following conditions 1 or 2.

[Polishing condition 1]
Polishing equipment: SPP800S (manufactured by Okamoto Machinery Works Co., Ltd.)
Wafer: Diameter 300 mm; P-type silicon wafer (100) surface Polishing pad: SUPREME (registered trademark) RN-H (manufactured by Nitta Hearth Co., Ltd.)
Polishing time: 4 minutes Surface plate rotation speed: 40 rpm
Head rotation speed: 39 rpm
Supply speed of polishing composition: 0.6 L / min

[Polishing condition 2]
Polishing equipment: SPP800S (manufactured by Okamoto Machinery Works Co., Ltd.)
Wafer: Diameter 300 mm; P-type silicon wafer (100) surface Polishing pad: IK2010H (manufactured by Dow Chemical Company)
Polishing time: 3 minutes Surface plate rotation speed: 40 rpm
Head rotation speed: 39 rpm
Supply speed of polishing composition: 0.6 L / min

After polishing, the number of defects on the surface of the silicon wafer was measured using a wafer defect inspection / review device (“MAGICS M5640” manufactured by Lasertec Co., Ltd.) for the above examples and comparative examples. The sensitivity at the time of measurement was set to the highest D37 mV. In addition, the haze value of the silicon wafer surface was measured using a wafer surface inspection device (“LS6600” manufactured by Hitachi Engineering Co., Ltd.). The measured number of defects and the haze value are shown in the columns of "Defect" and "Haze" in Tables 1 to 5, respectively. In addition, the number of defects and the haze value of the examples are shown by the ratio when the comparative example is “1”. However, in Comparative Examples 5 to 7, the wafer after polishing became completely water repellent, and when the number of defects was measured by "MAGICS", the number of defects was excessive and overflow (OF) occurred.

The reason why the number of defects and the haze are reduced by using the examples is not always clear, but it is probably as follows.

By adding the organic acid, the carboxy group possessed by the organic acid is ionized and H + is generated. Therefore, the pH tends to decrease, and the zeta potential of the abrasive grains in the polishing composition changes. As a result, it is considered that the abrasive grains are more likely to come close to the wafer and the polishing is more likely to proceed.

Further, under basic conditions, water molecules form hydrogen bonds in the lone electron pair of the oxygen atom of C = O of the carboxy group. Therefore, the hydrophilicity is improved by increasing the water retention capacity on the polishing pad or the wafer. As a result, the number of defects and haze are reduced due to the synergistic effect with the polymer protective effect of the polishing composition. Although the subpolymer alone has the effect of reducing the number of defects and haze, it may be deteriorated due to water repellency because the weight average molecular weight is small and the water retention capacity is low.

The embodiment of the present invention has been described above. The embodiments described above are merely examples for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and the above-described embodiment can be appropriately modified and implemented within a range that does not deviate from the gist thereof.

Claims (3)

Colloidal silica abrasive grains and
Basic compounds and
Polyvinyl alcohols having a weight average molecular weight of 100,000 or less and a structural unit represented by the following chemical formula (1), or poly having a weight average molecular weight of 100,000 or less and a structural unit represented by the following chemical formula (2). Water-soluble polymers containing glycerins and
One or more selected from the group consisting of organic acids and organic acid salts,
Including water
A composition for polishing a silicon wafer having a pH of 9.0 to 12.0 .

The silicon wafer polishing composition according to claim 1, further comprising.
A composition for polishing a silicon wafer , which comprises a nonionic surfactant. The composition for polishing a silicon wafer according to claim 2.
The nonionic surfactant is a composition for polishing a silicon wafer , which contains a polyhydric alcohol.