TWI798325B - abrasive composition - Google Patents

Abstract

其中，R¹ 、R² 、及R³ 分別獨立表示氫原子或有機基，X表示單鍵或結合鏈，R⁴ 、R⁵ 、及R⁶ 分別獨立表示氫原子或有機基。The invention provides a polishing composition which can further reduce the minor defects and haze of the polished semiconductor wafer. The polishing composition includes 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). Among the vinyl alcohol-based resins, the following general formula (2 ) The molar concentration of the structural unit represented by ) is 2 mol% or more in the total structural units.

Wherein, R ¹ , R ² , and R ³ 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 independently represent a hydrogen atom or an organic group.

Description

abrasive composition

The present invention relates to a polishing composition.

Polishing of semiconductor wafers by CMP is performed in three-stage or four-stage multi-stage polishing to achieve high-precision smoothing and planarization. The main purpose of the finishing step carried out in the final stage is to reduce microdefects or haze (surface cloudiness).

Generally, the polishing composition used in the fine polishing step of the semiconductor wafer contains a water-soluble polymer such as hydroxyethyl cellulose (HEC). Water-soluble polymers have the effect of making the surface of semiconductor wafers hydrophilic, and inhibit the damage to semiconductor wafers caused by abrasive grains adhering to the surface, excessive chemical etching, and agglomeration of abrasive grains. It is known that microdefects or haze can be reduced by this.

HEC uses natural cellulose as a raw material, and therefore may contain water-insoluble impurities derived from cellulose. Therefore, in the polishing composition containing HEC, slight defects may be generated due to the influence of the impurities. In addition, HEC mostly uses those with a molecular weight of hundreds of thousands to millions. The higher the molecular weight, the easier it is to cause clogging of the filter, and it is difficult for a filter with a smaller pore size to pass liquid. Therefore, when using a water-soluble polymer with a relatively large molecular weight, it is difficult to remove coarse particles. In addition, since it is easy to cause aggregation of abrasive grains, there is concern about the long-term stability of the polishing composition.

Japanese Patent Application Laid-Open No. 2012-216723 discloses a polishing composition containing at least one water-soluble polymer selected from vinyl alcohol-based resins having a 1,2-diol structural unit. When the polishing composition contains the vinyl alcohol-based resin having a 1,2-diol structural unit, microscopic defects or surface roughness of the polished semiconductor wafer can be reduced. The reason for this is considered to be that crystallization of polyvinyl alcohol is suppressed by introducing a modifying group (1,2-diol structure) having steric hindrance.

In recent years, along with the miniaturization of design rules of semiconductor devices, stricter management is also required for microscopic defects and haze on the surface of semiconductor wafers.

The object of the present invention is to provide a polishing composition that can further reduce microscopic defects and haze of a semiconductor wafer after polishing.

其中，R¹ 、R² 、及R³ 分別獨立表示氫原子或有機基，X表示單鍵或結合鏈，R⁴ 、R⁵ 、及R⁶ 分別獨立表示氫原子或有機基。A polishing composition according to an embodiment of the present invention includes 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). The above-mentioned vinyl alcohol-based resin Among them, the molar concentration of the structural unit represented by the following general formula (2) is 2 mol% or more in the total structural units. [chemical 1]

Wherein, R ¹ , R ² , and R ³ 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 independently represent a hydrogen atom or an organic group.

According to the present invention, the minute defects and haze of the polished semiconductor wafer can be further reduced.

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

As mentioned above, the water-soluble polymer is added to make the surface of the semiconductor wafer hydrophilic. For this purpose, it is considered that the greater the number of hydroxyl groups as hydrophilic groups, the better. Therefore, vinyl alcohol-based resins added to the polishing composition are usually fully saponified (those with a degree of saponification of 98 mol% or more).

However, as a result of investigation by the inventors of the present invention, it has been found that in the case of a vinyl alcohol-based resin having a 1,2-diol structural unit, using a partially saponified product can reduce microscopic defects or haze more than a fully saponified product.

The mechanism is not clear. As a reason, it is believed that by using partially saponified products, the hydrogen bonding between hydroxyl groups is reduced, and the bonding between molecules is weakened, so that the polymer is easily soluble in water, and undissolved substances or gels are suppressed. Formation of foreign matter. As another factor, it is considered that by increasing the content of vinyl acetate as a hydrophobic group, the hydrophobic interaction with the semiconductor wafer becomes stronger, and the protection of the semiconductor wafer becomes larger.

The present invention has been accomplished 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 abrasive grains, a basic compound, and a vinyl alcohol-based resin (hereinafter referred to as "modified PVA") having a 1,2-diol structural unit.

Abrasives commonly used in this field can be used, for example, colloidal silica, fumed silica, colloidal alumina, fumed alumina and cerium oxide, etc., especially preferably colloidal silica or fumed silica Silicon. The particle size of the abrasive grains is not particularly limited, 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, and 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 of the present embodiment is preferably diluted and used so that the concentration of the abrasive grains becomes 100 to 5000 ppm (ppm by mass. The same applies hereinafter). There is a tendency that the higher the concentration of abrasive grains, the lower the micro-defects or haze. The lower limit of the concentration of the diluted abrasive particles is preferably 1000 ppm, more preferably 2000 ppm. The upper limit of the concentration of the diluted abrasive grains is preferably 4000 ppm, more preferably 3000 ppm.

Alkaline compounds are used to etch the surface of semiconductor wafers for chemical polishing. The basic compound is, for example, an amine compound, an inorganic alkali compound, or the like.

Amine compounds are, for example, primary amines, secondary amines, tertiary amines, quaternary ammonium and hydroxides thereof, heterocyclic amines, and the like. Specifically, ammonia, tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrabutylammonium hydroxide (TBAH), methylamine, dimethylamine, trimethylammonium Baseamine, 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 -Methylpiperone, piperazine hydrochloride, guanidine carbonate, etc.

Examples of inorganic alkali compounds include hydroxides of alkali metals, salts of alkali metals, hydroxides of alkaline earth metals, salts of alkaline earth metals, and the like. Specifically, the inorganic alkali compound is potassium hydroxide, sodium hydroxide, potassium bicarbonate, potassium carbonate, sodium bicarbonate, sodium carbonate, or the like.

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

The content of the basic compound (the total amount when two or more are included) is not particularly limited. For example, in terms of mass ratio to abrasive grains, abrasive grain:basic compound=1:0.001˜1:0.10. The polishing composition of this embodiment is preferably used by diluting the concentration of the basic compound to 5-200 ppm

其中，R¹ 、R² 、及R³ 分別獨立表示氫原子或有機基，X表示單鍵或結合鏈，R⁴ 、R⁵ 、及R⁶ 分別獨立表示氫原子或有機基。Modified PVA is a vinyl alcohol-based resin having a 1,2-diol structural unit represented by the following general formula (1). [Chem 2]

Wherein, R ¹ , R ² , and R ³ 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 independently represent a hydrogen atom or an organic group.

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

[chemical 3]

In addition to the structural units represented by formulas (2) and (3), the modified PVA has a 1,2-diol structural unit represented by formula (1). Thereby, the crystallization of polyvinyl alcohol is suppressed, and the microscopic defects or haze of the semiconductor wafer after grinding can be further reduced. The modification amount of the 1,2-diol structural unit in the polymer is not particularly limited, for example, it is 1-20 mol%.

Most preferably, all of 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 hydrogen atoms, and X is a single bond.

The average polymerization degree of modified PVA is not specifically limited, For example, it is 200-3000. The average degree of polymerization of modified PVA can be measured based on JISK6726.

The content of modified PVA (the total amount of two or more) is not particularly limited. For example, in terms of mass ratio to abrasive grains, abrasive grains:modified PVA=1:0.001～1:0.40. The lower limit of the mass ratio of modified PVA to abrasive grains is preferably 0.0050, more preferably 0.0070.

The polishing composition of this embodiment is preferably used when the concentration of the modified PVA is diluted to 10-200 ppm. The higher the concentration of the modified PVA after dilution, the more microscopic defects or haze tend to decrease. The lower limit of the concentration of the diluted modified PVA is preferably 20 ppm, more preferably 50 ppm.

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).

其中，R¹ 、R² 、及R³ 分別獨立表示氫原子或有機基，X表示單鍵或結合鏈，R⁴ 、R⁵ 、及R⁶ 分別獨立表示氫原子或有機基，R⁷ 、及R⁸ 分別獨立表示氫原子或R⁹ -CO-(R⁹ 為碳數1～4之烷基)。[chemical 4]

Among them, R ¹ , R ² , and R ³ independently represent a hydrogen atom or an organic group, X represents a single bond or a bonded chain, R ⁴ , R ⁵ , and R ⁶ independently represent a hydrogen atom or an organic group, 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 carbons).

In the polishing composition of this embodiment, the modified PVA is such that the molar concentration of the structural unit represented by the following general formula (2) is 2 mol% or more in the total structural units. [chemical 5]

The higher the molar concentration of the structural unit represented by formula (2) in the modified PVA, the more microscopic defects or haze of the polished semiconductor wafer can be 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, if the molar concentration of the structural unit represented by the formula (2) in the modified PVA is higher, the power to hydrophilize the semiconductor wafer is weakened. 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 (molar %) of the structural unit represented by formula (2) in the modified PVA can be considered to be equal to the value obtained by subtracting the degree of saponification (molar %) of the modified PVA from 100 molar %. In addition, the saponification degree of modified PVA was measured based on JISK6726 similarly to PVA.

The polishing composition of this embodiment may further contain a nonionic surfactant. By including a nonionic surfactant, microscopic defects and haze can be further reduced.

Nonionic surfactants suitable for the polishing composition of this embodiment are, for example, ethylenediamine tetrapolyoxyethylene polyoxypropylene (polyxamine), poloxamer, polyoxyalkylene alkyl ether, polyoxyethylene Oxyalkylene fatty acid esters, polyoxyalkylene alkylamines, polyoxyalkylene methyl glucosides, 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 methyl glucoside, polyoxyethylene methyl glucoside, polyoxypropylene methyl glucoside, etc. are mentioned, for example.

The content of the nonionic surfactant (the total amount when two or more of them are included) is not particularly limited, for example, the abrasive grain is calculated as the mass ratio of the abrasive grain: nonionic surfactant = 1: 0.0001～ 1:0.015. The polishing composition of this embodiment is preferably used by diluting the concentration of the nonionic surfactant to 0.5-30 ppm.

The polishing composition of this embodiment may further contain a pH adjuster. The pH of the polishing composition of this embodiment is preferably 8.0-12.0.

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

The polishing composition of this embodiment is prepared by mixing abrasive grains, basic compound, modified PVA and other formulation materials appropriately and adding water. The polishing composition of this embodiment may be prepared by sequentially mixing abrasive grains, basic compounds, modified PVA and other formulation materials in water. As a method of mixing these components, a method commonly used in the technical field of a polishing composition, such as a homogenizer, ultrasonic waves, etc., is used.

The polishing composition described above is diluted with water to an appropriate concentration, and then used for polishing semiconductor wafers.

The polishing composition of this embodiment can be used particularly preferably for fine polishing of silicon wafers. Example

Hereinafter, the present invention will be described more specifically by means of examples. The present invention is not limited to these Examples.

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

[Table 1]

The contents in Table 1 are all diluted contents. The abrasive grain system uses colloidal silicon dioxide. "Particle size" in Table 1 represents the average secondary particle size of abrasive grains. "NH ₄ OH" means ammonia solution. Modified PVA A~D represent butylene glycol 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 is P-type, and the resistivity is above 0.1 Ωcm and less than 100 Ωcm. The grinding surface is the <100> surface. As a polishing device, a SPP800S single-side polishing device manufactured by Okamoto Machine Tool Works Co., Ltd. was used. The abrasive pad system uses a suede pad. The polishing composition was diluted 31 times and supplied at a supply rate of 1 L/min. The rotation speed of the table was 40 rpm, the rotation speed of the carrier was 39 rpm, and the grinding load was 100 gf/cm ² , and grinding was performed for 2 minutes. Furthermore, before polishing with the polishing compositions of Examples and Comparative Examples, preliminary polishing was performed for 3 minutes using polishing slurry NP7050S (manufactured by Nittahaas Co., Ltd.).

Determination of minor defects and haze of polished silicon wafers. Minor 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 "defects" and "haze" columns of Table 1 above.

According to the comparison between Example 1 and Comparative Example 1, and the comparison between Example 3 and Comparative Example 2, it can be known that if other conditions are constant, the higher the molar concentration of the structural unit represented by formula (2), the more micro-defects and Haze tendency.

According to the comparison of Example 2 and Example 4, and the comparison of Examples 7, 9 and 10, it can be seen that if other conditions are constant, the higher the concentration of modified PVA, the lower the tendency of micro defects.

According to the comparison between Example 2 and Example 3, and the comparison between Example 7 and Example 8, it can be seen that if other conditions are constant, the higher the concentration of abrasive grains, the lower the tendency of micro-defects.

According to the comparison of Examples 4-6, it can be seen that if other conditions are constant, the lower the concentration of the basic compound, the lower the tendency of micro-defects and haze.

According to the comparison of Comparative Example 3 and Comparative Example 4, it can be seen that in ordinary PVA, unlike the case of modified PVA, the molar concentration of the structural unit represented by formula (2) increases, thereby increasing microdefects and haze.

[Grinding example 2] The polishing compositions of Examples 11-26 and Comparative Examples 5-8 shown in Table 2 and Table 3 were produced.

[Table 2]

[table 3]

The contents in Table 2 and Table 3 are all diluted contents. "Polyxamine" means ethylenediaminetetrapolyoxyethylene polyoxypropylene with a weight average molecular weight of 7240, "polyol A" means polyoxypropylene methyl glucoside with a weight average molecular weight of 775, and "polyol B" means a weight average molecular weight 1075 polyoxyethylene methyl glucoside. Others are the same as 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 microdefects and haze were measured.

According to the comparison of Example 11, Example 12 and Comparative Example 5, it can be seen that if other conditions are constant, the higher the molar concentration of the structural unit represented by formula (2), the lower the tendency of micro-defects and haze.

From the comparison of Examples 1 to 10 and Examples 11 to 26, it can be seen that microdefects and haze can be significantly reduced by including a nonionic surfactant.

The embodiments of the present invention have been described above. The above-described embodiments are merely examples for implementing the present invention. Therefore, the present invention is not limited to the above-mentioned embodiments, and the above-mentioned embodiments can be appropriately modified and implemented within a range not departing from the gist.

Claims (3)

A polishing composition comprising 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). Among the above-mentioned vinyl alcohol-based resins, the following The molar concentration of the structural unit represented by general formula (2) is more than 2 mol% in the total structural unit,

Wherein, R ¹ , R ² , and R ³ 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 independently represent a hydrogen atom or an organic group. The polishing composition according to claim 1, further comprising a nonionic surfactant. The polishing composition according to claim 1 or 2, wherein the basic compound is selected from the group consisting of alkali metal hydroxides, alkali metal salts, ammonia, amines, ammonium salts, and quaternary ammonium hydroxides One or more of them.