JP6978933B2 - Polishing composition - Google Patents

Description

The present invention relates to a polishing composition.

Polishing of semiconductor wafers by CMP realizes high-precision smoothing and flattening by performing three-step or four-step polishing. The final polishing process is primarily aimed at reducing microdefects and haze (surface fogging).

The polishing composition used in the finish polishing step of a semiconductor wafer generally contains a water-soluble polymer such as hydroxyethyl cellulose (HEC). The water-soluble polymer has a role of making the surface of the semiconductor wafer hydrophilic, 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. It is known that this can reduce minute defects and haze.

Since HEC is made from cellulose, which is a natural raw material, it may contain water-insoluble impurities derived from cellulose. Therefore, in the polishing composition containing HEC, minute defects may occur due to the influence of this impurity. Further, a HEC having a molecular weight of about several hundred thousand to one million is often used, but the higher the molecular weight, the more easily the filter is clogged, and the smaller the pore size, the more difficult it is to pass the liquid. Therefore, when a water-soluble polymer having a large molecular weight is used, it becomes difficult to remove coarse particles. In addition, since agglutination of abrasive grains is likely to occur, there is a concern about the long-term stability of the polishing composition.

Japanese Unexamined Patent Publication No. 2012-216723 discloses a polishing composition containing at least one kind of water-soluble polymer selected from vinyl alcohol-based resins having 1,2-diol structural units. By containing a vinyl alcohol-based resin having a 1,2-diol structural unit in the polishing composition, it is possible to reduce minute defects and surface roughness of the semiconductor wafer after polishing. It is considered that this is because the crystallization of polyvinyl alcohol is suppressed by introducing a modifying group (1,2-diol structure) having steric hindrance.

Japanese Unexamined Patent Publication No. 2012-216723

In recent years, with the progress of miniaturization of design rules for semiconductor devices, stricter control is required 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 minute defects and haze of a semiconductor wafer after polishing.

但し、Ｒ^１、Ｒ^２、及びＲ^３はそれぞれ独立して水素原子又は有機基を示し、Ｘは単結合又は結合鎖を示し、Ｒ^４、Ｒ^５、及びＲ^６はそれぞれ独立して水素原子又は有機基を示す。 The polishing composition according to one embodiment of the present invention contains abrasive grains, a basic compound, and a vinyl alcohol-based resin having a 1,2-diol structural unit represented by the following general formula (1). In the vinyl alcohol-based resin, the molar concentration of the structural unit represented by the following general formula (2) is 2 mol% or more in all the constituent units.

However, R ¹ , R ² , and R ³ independently indicate a hydrogen atom or an organic group, X indicates a single bond or a bond chain, and R ⁴ , R ⁵ , and R ⁶ independently indicate a hydrogen atom. Or indicates an organic group.

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

The present inventors have conducted various studies in order to solve the above-mentioned problems. As a result, the following findings were obtained.

As described above, the water-soluble polymer is added to hydrophilize the surface of the semiconductor wafer. For this purpose, it is considered preferable that the number of hydroxyl groups as hydrophilic groups is large. Therefore, the vinyl alcohol-based resin added to the polishing composition is usually a completely saponified product (saponification degree is 98 mol% or more). ) Is used.

However, as a result of the 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, microdefects and haze can be further reduced by using a partially saponified product rather than a completely saponified product. rice field.

This mechanism is not clear, but one factor is that the use of partially saponified products reduces hydrogen bonds between hydroxyl groups, and weakens the bonds between molecules, making the polymer more soluble in water and undissolved substances. And it is considered that the formation of gel-like foreign matter is suppressed. As another factor, it is considered that the content of the vinyl acetate group, which is a hydrophobic group, is increased, so that the hydrophobic interaction with the semiconductor wafer is strengthened and the protection property to the semiconductor wafer is increased.

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

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

As the abrasive grains, those commonly used in this field can be used, and examples thereof include colloidal silica, fumed silica, colloidal alumina, fumed alumina and ceria, and colloidal silica or fumed silica is particularly preferable. The particle size of the abrasive grains is not particularly limited, but for example, those having a secondary average particle size 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 diluted 10 to 40 times during polishing before use. The polishing composition according to the present embodiment is preferably diluted so that the concentration of the abrasive grains is 100 to 5000 ppm (mass ppm; the same applies hereinafter). The higher the concentration of the abrasive grains, the more the minute defects and haze tend to be reduced. 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 etches the surface of the semiconductor 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 hydroxide 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 alkali compound include alkali metal hydroxides, alkali metal salts, alkaline earth metal hydroxides, alkaline earth metal salts and the like. Specific examples of the inorganic alkaline compound include potassium hydroxide, sodium hydroxide, potassium hydrogencarbonate, potassium carbonate, sodium hydrogencarbonate, and sodium carbonate.

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

The content of the basic compound (when two or more kinds are contained, the total amount thereof) is not particularly limited, but for example, in terms of the mass ratio with the abrasive grains, the abrasive grains: the basic compound = 1: 0.001 to 1: 0. It is .10. The polishing composition according to this embodiment is preferably diluted so that the concentration of the basic compound is 5 to 200 ppm.

但し、Ｒ^１、Ｒ^２、及びＲ^３はそれぞれ独立して水素原子又は有機基を示し、Ｘは単結合又は結合鎖を示し、Ｒ^４、Ｒ^５、及びＲ^６はそれぞれ独立して水素原子又は有機基を示す。 The modified PVA is a vinyl alcohol-based resin having a 1,2-diol structural unit represented by the following general formula (1).

However, R ¹ , R ² , and R ³ independently indicate a hydrogen atom or an organic group, X indicates a single bond or a bond chain, and R ⁴ , R ⁵ , and R ⁶ independently indicate a hydrogen atom. Or indicates an organic group.

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

The modified PVA has a 1,2-diol structural unit represented by the formula (1) in addition to the structural units represented by the formulas (2) and (3). As a result, crystallization of polyvinyl alcohol is suppressed, and minute defects and haze of the semiconductor wafer after polishing 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 preferable that R 1 to} R ³ and R ^{4 to} R ⁵ in the 1,2-diol structural unit represented by the general formula (1) are all 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 (when two or more kinds are contained, the total amount thereof) is not particularly limited, but for example, in terms of the mass ratio with the abrasive grains, the abrasive grains: modified PVA = 1: 0.001 to 1: 0.40. Is. The lower limit of the mass ratio of the modified PVA to the abrasive grains is preferably 0.0050, more preferably 0.0070.

The polishing composition according to this embodiment is preferably diluted so that the concentration of the modified PVA is 10 to 200 ppm. The higher the concentration of modified PVA after dilution, the more likely it is that microdefects and haze will be reduced. The lower limit of the concentration of 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-based monomer and a compound represented by the following general formula (4).

但し、Ｒ^１、Ｒ^２、及びＲ^３はそれぞれ独立して水素原子又は有機基を示し、Ｘは単結合又は結合鎖を示し、Ｒ^４、Ｒ^５、及びＲ^６はそれぞれ独立して水素原子又は有機基を示し、Ｒ^７、及びＲ^８はそれぞれ独立して水素原子又はＲ^９−ＣＯ−（Ｒ^９は炭素数１〜４のアルキル基）を示す。

However, R ¹ , R ² , and R ³ independently indicate a hydrogen atom or an organic group, X indicates a single bond or a bonded chain, and R ⁴ , R ⁵ , and R ⁶ independently indicate a hydrogen atom. Alternatively, it indicates an organic group, and ^{R 7 and R 8} independently indicate 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, the modified PVA has a molar concentration of 2 mol% or more of the structural units represented by the following general formula (2) in all the constituent units.

The higher the molar concentration of the structural unit represented by the formula (2) in the modified PVA, the more the minute defects and haze of the semiconductor wafer after polishing can be further reduced. The lower limit of the molar concentration of the structural unit represented by the formula (2) in the modified PVA is preferably 5 mol%, 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 ability to hydrophilize the semiconductor wafer. The upper limit of the molar concentration of the structural unit represented by the formula (2) in the modified PVA is preferably 30 mol%, more preferably 20 mol%.

The molar concentration (mol%) of the structural unit represented by the formula (2) in the modified PVA may be regarded as equal to the value obtained by subtracting the saponification degree (mol%) of the modified PVA from 100 mol%. The saponification degree of the modified PVA shall be measured according to JIS K 6726 as in the case of PVA.

The polishing composition according to this embodiment may further contain a nonionic surfactant. By including a nonionic surfactant, microdefects and haze can be further reduced.

Suitable nonionic surfactants for the polishing composition according to this embodiment are, for example, ethylenediaminetetrapolyoxyethylene polyoxypropylene (poloxamin), poloxamer, polyoxyalkylene alkyl ether, polyoxyalkylene fatty acid ester, polyoxyalkylene alkyl. Amine, polyoxyalkylene methyl glucoside, etc.

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. Examples of the polyoxyalkylene methyl glucoside include polyoxyethylene methyl glucoside and polyoxypropylene methyl glucoside.

The content of the nonionic surfactant (when two or more kinds are contained, the total amount thereof) is not particularly limited, but for example, in terms of the mass ratio with the abrasive grains, the abrasive grains: the nonionic surfactant = 1: 0. It is .0001 to 1: 0.015. The polishing composition according to this embodiment is preferably diluted so that the concentration of the nonionic surfactant is 0.5 to 30 ppm.

The polishing composition according to this embodiment may further contain a pH adjuster. The pH of the polishing composition according to this 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 composition.

The polishing composition according to this embodiment is prepared by appropriately mixing abrasive grains, a basic compound, modified PVA and other compounding materials, and adding water. The polishing composition according to this embodiment is also prepared by sequentially mixing abrasive grains, a basic compound, a modified PVA 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 semiconductor wafer.

The polishing composition according to this embodiment can be particularly preferably used for finish polishing of a silicon wafer.

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

[Polishing example 1]
The polishing compositions of Examples 1 to 10 and Comparative Examples 1 to 4 shown in Table 1 were prepared.

The contents in Table 1 are all the contents after dilution. Colloidal silica was used as the abrasive grains. The "particle size" in Table 1 represents the average secondary particle size of the abrasive grains. "NH ₄ OH" represents an aqueous ammonia solution. The modified PVAs A to D represent butenediol vinyl alcohol polymers having different degrees of polymerization and saponification, respectively. PVA A and B represent polyvinyl alcohols having different saponification degrees.

A 12-inch silicon wafer was polished using the polishing compositions of these Examples and Comparative Examples. The conductive type of the silicon wafer was P type, and the resistivity was 0.1 Ωcm or more and less than 100 Ω cm. The polished surface was set to <100> surface. As the polishing device, an SPP800S single-sided polishing device manufactured by Okamoto Machinery Works Co., Ltd. was used. A suede pad was used as the polishing pad. The polishing composition was diluted 31-fold and supplied at a feed rate of 1 L / min. The surface plate rotation speed was 40 rpm, the carrier rotation speed was 39 rpm, and the polishing load was 100 gf / cm ² , and polishing was performed for 2 minutes. Prior to polishing with the polishing compositions of Examples and Comparative Examples, preliminary polishing was carried out for 3 minutes using a polishing slurry NP7050S (manufactured by Nitta Hearth Co., Ltd.).

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

From the comparison between Example 1 and Comparative Example 1 and the comparison between Example 3 and Comparative Example 2, if the other conditions are constant, the higher the molar concentration of the structural unit represented by the formula (2), the smaller the concentration. It can be seen that defects and haze tend to be reduced.

From the comparison between Example 2 and Example 4, and the comparison of Examples 7, 9 and 10, it can be seen that, if the other conditions are constant, the higher the concentration of the modified PVA, the more the microdefects tend to be reduced. ..

From the comparison between Example 2 and Example 3 and the comparison between Example 7 and Example 8, if the other conditions are constant, the higher the concentration of the abrasive grains, the more the minute defects tend to be reduced. I understand.

From the comparison of Examples 4 to 6, it can be seen that, if the other conditions are constant, the lower the concentration of the basic compound, the more the microdefects and haze tend to decrease.

From the comparison between Comparative Example 3 and Comparative Example 4, in the case of normal PVA, unlike the case of modified PVA, the molar concentration of the structural unit represented by the formula (2) is increased, so that microdefects and haze increase. I understand.

[Polishing example 2]
The polishing compositions of Examples 11 to 26 and Comparative Examples 5 to 8 shown in Tables 2 and 3 were prepared.

The contents in Tables 2 and 3 are all the contents after dilution. "Poroxamine" is ethylenediamine tetrapolyoxyethylene polyoxypropylene having a weight average molecular weight of 7240, "polyhydric alcohol A" is polyoxypropylene methyl glucoside having a weight average molecular weight of 775, and "polyhydric alcohol B" is polyoxy having a weight average molecular weight of 1075. Represents ethylene methyl glucoside. Others are the same as in Table 1.

Using the polishing compositions of Examples 11 to 26 and Comparative Examples 5 to 8, the 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, if the other conditions are constant, the higher the molar concentration of the structural unit represented by the formula (2), the smaller the minute defects and haze. It turns out that there is a tendency.

From the comparison between Examples 1 to 10 and Examples 11 to 26, it can be seen that the inclusion of the nonionic surfactant can significantly reduce microdefects and haze.

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)

Abrasive grains and
Basic compounds and
It contains a vinyl alcohol-based resin having a 1,2-diol structural unit represented by the following general formula (1).
The vinyl alcohol-based resin is a polishing composition in which the molar concentration of the structural unit represented by the following general formula (2) is 2 mol% or more in all the constituent units.

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