KR20200098547A - Polishing composition - Google Patents

Abstract

단, R¹, R², 및 R³은 각각 독립적으로 수소 원자 또는 유기기를 나타내고, X는 단결합 또는 결합쇄를 나타내고, R⁴, R⁵, 및 R⁶은 각각 독립적으로 수소 원자 또는 유기기를 나타낸다.A polishing composition capable of further reducing micro-defects and haze of a semiconductor wafer after polishing is provided. The polishing composition includes an abrasive grain, a basic compound, and a vinyl alcohol-based resin having a 1,2-diol structural unit represented by the following general formula (1), and the vinyl alcohol-based resin includes the following general formula (2) The molar concentration of the structural unit represented by is 2 mol% or more of the total structural units.

However, R ¹ , R ² , and R ³ each independently represent a hydrogen atom or an organic group, X represents a single bond or a bonded chain, and R ⁴ , R ⁵ , and R ⁶ each independently represent a hydrogen atom or an organic group. Show.

Description

Polishing composition

The present invention relates to a polishing composition.

In the polishing of a semiconductor wafer by CMP, high-precision smoothing and flattening are realized by performing three or four multi-step polishing. The finish polishing process performed in the final step aims at reducing micro-defects and haze (surface haze) as the main purpose.

A polishing composition used in a semiconductor wafer finish polishing step generally contains a water-soluble polymer such as hydroxyethylcellulose (HEC). The water-soluble polymer serves to hydrophilize the surface of the semiconductor wafer, and suppresses damage to the semiconductor wafer due to adhesion of abrasive grains to the surface, excessive chemical etching, aggregation of abrasive grains, and the like. Thereby, it is known that micro-defects and haze can be reduced.

Since HEC uses cellulose as a natural raw material as a raw material, water-insoluble impurities derived from cellulose may be contained. Therefore, in the polishing composition containing HEC, micro-defects may occur under the influence of this impurity. In addition, HECs are well used those having a molecular weight of about several hundred thousand to one million, but as the molecular weight increases, clogging of the filter is likely to occur, and in a filter having a small pore diameter, it becomes difficult to pass liquid. Therefore, when a water-soluble polymer having a large molecular weight is used, it becomes difficult to remove coarse particles. Moreover, since agglomeration of abrasive grains is liable to occur, there is also a concern about long-term stability of the polishing composition.

Japanese Patent Application Laid-Open No. 2012-216723 discloses a polishing composition comprising at least one water-soluble polymer selected from vinyl alcohol-based resins having 1,2-diol structural units. By containing a vinyl alcohol resin having a 1,2-diol structural unit in the polishing composition, it is possible to reduce micro-defects and surface roughness of the polished semiconductor wafer. This is considered to be because crystallization of polyvinyl alcohol is suppressed by introducing a modified group having steric hindrance (1,2-diol structure).

Initiation of the invention

In recent years, as the design rules of semiconductor devices have been refined, more stringent management has been demanded for minute defects and haze on the surface of semiconductor wafers.

An object of the present invention is to provide a polishing composition capable of further reducing micro-defects and haze of a semiconductor wafer after polishing.

A polishing composition according to an embodiment of the present invention comprises a vinyl alcohol resin having an abrasive grain, a basic compound, and a 1,2-diol structural unit represented by the following general formula (1), and the vinyl alcohol type The resin has a molar concentration of the structural unit represented by the following general formula (2) of 2 mol% or more of the total structural units.

However, R ¹ , R ² , and R ³ each independently represent a hydrogen atom or an organic group, X represents a single bond or a bonded chain, and R ⁴ , R ⁵ , and R ⁶ each independently represent a hydrogen atom or an organic group. Show.

According to the present invention, it is possible to further reduce micro-defects and haze of a semiconductor wafer after polishing.

The present inventors conducted various studies in order to solve the above problems. As a result, the following knowledge was obtained.

As described above, the water-soluble polymer is added to make the surface of the semiconductor wafer hydrophilic. For this purpose, since it is thought that the larger the number of hydroxyl groups, which is a hydrophilic group, is preferable, the vinyl alcohol-based resin added to the polishing composition is usually a completely saponified product (having a degree of saponification of 98 mol% or more).

However, as a result of investigation by the present inventors, it was found that in the case of a vinyl alcohol-based resin having a 1,2-diol structural unit, using a partial saponified product rather than a complete saponified product can further reduce micro-defects and haze.

This mechanism is not clear, but one factor is that the use of partial saponification products reduces hydrogen bonds between hydroxyl groups and weakens the bonds between molecules, making the polymer easier to dissolve in water. It is conceivable that production is suppressed. As another factor, it is conceivable that the increase in the content of the vinyl acetate group as a hydrophobic group increases the hydrophobic interaction with the semiconductor wafer and increases the protection properties for the semiconductor wafer.

The present invention has been completed based on these findings. Hereinafter, a polishing composition according to an embodiment of the present invention will be described in detail.

A polishing composition according to an embodiment of the present invention includes an abrasive grain, a basic compound, and a vinyl alcohol-based resin having a 1,2-diol structural unit (hereinafter referred to as "modified PVA").

The abrasive grains can be used commercially in this field, for example, colloidal silica, fumed silica, colloidal alumina, fumed alumina, ceria, etc., and colloidal silica or fumed silica is particularly preferred. Although the particle diameter of the abrasive grain is not particularly limited, for example, a secondary average particle diameter of 30 to 100 nm can be used.

The content of the abrasive grains is not particularly limited, but is, for example, 0.10 to 20% by mass of the entire polishing composition. The polishing composition is used after being diluted 10 to 40 times during polishing. The polishing composition according to the present embodiment is preferably diluted and used so that the concentration of the abrasive grains is 100 to 5000 ppm (ppm by mass. As the concentration of the abrasive grains is higher, there is a tendency that micro defects and haze decrease. The lower limit of the concentration of the abrasive grains after dilution is preferably 1000 ppm, more preferably 2000 ppm. The upper limit of the concentration of the abrasive grains after dilution is preferably 4000 ppm, more preferably 3000 ppm.

The basic compound is chemically polished by etching the surface of the semiconductor wafer. The basic compound is, for example, an amine compound and an inorganic alkali compound.

The amine compound is, for example, a primary amine, a secondary amine, a tertiary amine, a quaternary ammonium and its hydroxide, and a heterocyclic amine. 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-methyl piperazine, piperazine hydrochloride, guanidine carbonate, and the like.

Examples of the inorganic alkali compound include a hydroxide of an alkali metal, a salt of an alkali metal, a hydroxide of an alkaline earth metal, and a salt of an alkaline earth metal. Specifically, the inorganic alkali compound is potassium hydroxide, sodium hydroxide, potassium hydrogen carbonate, potassium carbonate, sodium hydrogen carbonate, sodium carbonate, and the like.

The above-described basic compound may be used alone or in combination of two or more. Among the basic compounds described above, alkali metal hydroxides, alkali metal salts, ammonia, amines, ammonium salts, and quaternary ammonium hydroxides are particularly preferred.

Although the content of the basic compound (when it contains two or more types, the total amount) is not particularly limited, it is, for example, in terms of mass ratio with the abrasive, and is abrasive: basic compound = 1:0.001 to 1:0.10. The polishing composition according to the present embodiment is preferably diluted and used so that the concentration of the basic compound is 5 to 200 ppm.

Modified PVA is a vinyl alcohol resin having a 1,2-diol structural unit represented by the following general formula (1).

However, R ¹ , R ² , and R ³ each independently represent a hydrogen atom or an organic group, X represents a single bond or a bonded chain, and R ⁴ , R ⁵ , and R ⁶ each independently represent a hydrogen atom or an organic group. Show.

"Vinyl alcohol resin" refers to a water-soluble polymer containing structural units represented by the following formulas (2) and (3).

Modified PVA has a 1,2-diol structural unit represented by Formula (1) in addition to the structural units represented by formulas (2) and (3). Thereby, crystallization of polyvinyl alcohol is suppressed, and minute defects and haze of the polished semiconductor wafer can be further reduced. The amount of modification of the 1,2-diol structural unit in the polymer is not particularly limited, but is, for example, 1 to 20 mol%.

It is most preferred that R ¹ to R ³ and R ⁴ to R ⁶ in the 1,2-diol structural unit represented by the general formula (1) are both hydrogen atoms and X is a single bond.

The average degree of polymerization of the modified PVA is not particularly limited, but is, for example, 200 to 3000. The average degree of polymerization of the modified PVA can be measured according to JIS K 6726.

The content of the modified PVA (in the case of containing two or more types, the total amount) is not particularly limited, but is, for example, a mass ratio with the abrasive grains: modified PVA = 1:0.001 to 1:0.40. The lower limit of the mass ratio of the modified PVA to the abrasive is preferably 0.0050, more preferably 0.0070.

The polishing composition according to the present embodiment is preferably diluted and used so that the concentration of the modified PVA is 10 to 200 ppm. As the concentration of the modified PVA after dilution is higher, there is a tendency that micro defects and haze decrease. The lower limit of the concentration of the modified PVA after dilution is preferably 20 ppm, more preferably 50 ppm.

The modified PVA is produced, for example, by saponifying a copolymer of a vinyl ester monomer and a compound represented by the following general formula (4).

However, R ¹ , R ² , and R ³ each independently represent a hydrogen atom or an organic group, X represents a single bond or a bonded chain, and R ⁴ , R ⁵ , and R ⁶ each independently represent a hydrogen atom or an organic group. And R ⁷ and R ⁸ each independently represent a hydrogen atom or R ⁹ -CO- (R ⁹ is an alkyl group having 1 to 4 carbon atoms).

In the polishing composition according to the present embodiment, in the modified PVA, the molar concentration of the structural unit represented by the following general formula (2) is 2 mol% or more in the total structural units.

The higher the molar concentration of the structural unit represented by the formula (2) in the modified PVA, the more fine defects and haze of the polished semiconductor wafer can be reduced. The lower limit of the molar concentration of the structural unit represented by formula (2) in the modified PVA is preferably 5 mol%, and more preferably 10 mol%. On the other hand, the higher the molar concentration of the structural unit represented by the formula (2) in the modified PVA, the weaker the power to hydrophilize the semiconductor wafer. The upper limit of the molar concentration of the structural unit represented by formula (2) in the modified PVA is preferably 30 mol%, and more preferably 20 mol%.

The molar concentration (mol%) of the structural unit represented by formula (2) in the modified PVA may be regarded as the same as the value obtained by subtracting the saponification degree (mol%) of the modified PVA from 100 mol%. In addition, the saponification degree of the modified PVA shall be measured in accordance with JIS K 6726 like PVA.

The polishing composition according to the present embodiment may further contain a nonionic surfactant. By including a nonionic surfactant, micro-defects and haze can be further reduced.

Nonionic surfactants suitable for the polishing composition according to the present embodiment include, for example, ethylenediaminetetrapolyoxyethylenepolyoxypropylene (poloxamine), poloxamer, polyoxyalkylene alkyl ether, polyoxyalkylene fatty acid ester, Polyoxyalkylenealkylamine, polyoxyalkylenemethylglucoside, and the like.

As polyoxyalkylene alkyl ether, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, etc. are mentioned, for example. As polyoxyalkylene fatty acid ester, polyoxyethylene monolaurate, polyoxyethylene monostearate, etc. are mentioned, for example. As polyoxyalkylene alkylamine, polyoxyethylene laurylamine, polyoxyethylene oleylamine, etc. are mentioned, for example. As polyoxyalkylene glucoside, polyoxyethylene methyl glucoside, polyoxypropylene methyl glucoside, etc. are mentioned, for example.

The content of the nonionic surfactant (when it contains two or more types, the total amount) is not particularly limited, for example, in terms of mass ratio with the abrasive grain: nonionic surfactant = 1:0.0001 to 1:0.015. It is preferable that the polishing composition according to the present embodiment is diluted and used so that the concentration of the nonionic surfactant is 0.5 to 30 ppm.

The polishing composition according to the present embodiment may further contain a pH adjuster. The pH of the polishing composition according to the present embodiment is preferably 8.0 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 compositions.

The polishing composition according to the present embodiment is prepared by appropriately mixing an abrasive grain, a basic compound, a modified PVA and other blending materials, and adding water. The polishing composition according to the present embodiment is produced by sequentially mixing an abrasive grain, a basic compound, a modified PVA or other blending material with water. As a means for mixing these components, a means commonly used in the technical field of a polishing composition such as a homogenizer or ultrasonic wave is used.

The polishing composition described above is diluted with water to a suitable concentration and then used for polishing a semiconductor wafer.

The polishing composition according to the present embodiment can be particularly suitably used for finish polishing of a silicon wafer.

Example

Hereinafter, the present invention will be described in more detail by examples. The present invention is not limited to these examples.

[Polishing Example 1]

The polishing compositions of Examples 1-10 and Comparative Examples 1-4 shown in Table 1 were produced.

The contents in Table 1 are all contents after dilution. The abrasive grain used colloidal silica. "Particle diameter" in Table 1 shows the average secondary particle diameter of an abrasive grain. "NH ₄ OH" represents an aqueous ammonia solution. Modified PVAs A to D represent butenediol vinyl alcohol polymers with different degrees of polymerization and degrees of saponification, respectively. PVA A and B represent polyvinyl alcohols with different degrees of saponification.

Using the polishing compositions of these Examples and Comparative Examples, a 12-inch silicon wafer was polished. The conductivity type of the silicon wafer was P-type, and a resistivity of 0.1 Ωcm or more and less than 100 Ωcm was used. The polished surface was set to a <100> surface. As the polishing apparatus, an SPP800S single-side polishing apparatus manufactured by Okamoto Machine Tools Co., Ltd. was used. As the polishing pad, a suede pad was used. The polishing composition was diluted 31 times and supplied at a feed rate of 1 L/min. The rotation speed of the surface plate was 40 rpm, the rotation speed of the carrier was 39 rpm, and the polishing load was 100 gf/cm ² , and polishing was performed for 2 minutes. In addition, before polishing with the polishing compositions of Examples and Comparative Examples, preliminary polishing for 3 minutes was performed using polishing slurry NP7050S (manufactured by Nita Haas Corporation).

Micro defects and haze of the polished silicon wafer were measured. The minute defects were measured using a wafer surface inspection apparatus MAGICS M5640 (manufactured by Lasertec Corporation). Haze was measured using a wafer surface inspection device LS6600 (manufactured by Hitachi Engineering Co., Ltd.). The results were shown in the "Defect" and "Haze" columns in Table 1 above.

From the comparison of Example 1 and Comparative Example 1, and the comparison of Example 3 and Comparative Example 2, if other conditions are constant, the higher the molar concentration of the structural unit represented by the formula (2), the lower the micro defects and haze. I could see that there was a tendency.

From the comparison of Example 2 and Example 4, and the comparison of Examples 7, 9 and 10, it was found that when other conditions were constant, the higher the concentration of the modified PVA, the more the micro defects tended to decrease.

From the comparison between Example 2 and Example 3, and between Example 7 and Example 8, it was found that when other conditions were constant, as the concentration of the abrasive grains increased, the micro-defect tends to decrease.

From the comparison of Examples 4 to 6, it was found that when the other conditions were constant, the lower the concentration of the basic compound, the more the micro-defects and haze tended to decrease.

From the comparison between Comparative Example 3 and Comparative Example 4, it was found that in the normal PVA, unlike the case of the modified PVA, the molar concentration of the structural unit represented by the formula (2) increased, thereby increasing the micro-defects and haze.

[Polishing Example 2]

Polishing compositions of Examples 11 to 26 and Comparative Examples 5 to 8 shown in Tables 2 and 3 were prepared.

The contents of Table 2 and Table 3 are both contents after dilution. "Poloxamine" is ethylenediaminetetrapolyoxyethylene polyoxypropylene having a weight average molecular weight of 7240, "polyhydric alcohol A" is a polyoxypropylene methyl glucoside having a weight average molecular weight of 775, and "polyhydric alcohol B" is a polyhydric alcohol having a weight average molecular weight of 1075. It represents an oxyethylene methyl glucoside. Others are shown in Table 1.

Using the polishing compositions of Examples 11 to 26 and Comparative Examples 5 to 8, a silicon wafer was polished in the same manner as in Polishing Example 1, and minute defects and haze were measured.

From the comparison of Example 11, Example 12, and Comparative Example 5, it can be seen that when the other conditions are constant, the higher the molar concentration of the structural unit represented by the formula (2), the more the micro-defects and haze tend to decrease. there was.

From the comparison between Examples 1 to 10 and Examples 11 to 26, it was found that by containing a nonionic surfactant, micro-defects and haze can be remarkably reduced.

In the above, embodiments of the present invention have been described. The above-described embodiments are only examples for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiments, and it is possible to appropriately modify and implement the above-described embodiments within a range not departing from the spirit thereof.

Claims (3)

Abrasive,
A basic compound,
It includes a vinyl alcohol-based resin having a 1,2-diol structural unit represented by the following general formula (1),
The vinyl alcohol-based resin, the molar concentration of the structural unit represented by the following general formula (2), 2 mol% or more of the total structural units, a polishing composition.

However, R ¹ , R ² , and R ³ each independently represent a hydrogen atom or an organic group, X represents a single bond or a bonded chain, and R ⁴ , R ⁵ , and R ⁶ each independently represent a hydrogen atom or an organic group. Show. The method according to claim 1,
A polishing composition further comprising a nonionic surfactant. The method according to claim 1 or 2,
The basic compound is at least one selected from the group consisting of alkali metal oxides, alkali metal salts, ammonia, amines, ammonium salts, and quaternary ammonium hydroxides.