JP7157651B2 - Polishing composition - Google Patents

Description

The present invention relates to polishing compositions.

Polishing of silicon wafers for semiconductors by CMP achieves high-precision smoothing and planarization by performing multi-step polishing of three or four steps. In recent years, as demands for surface quality of wafers have become stricter, it has been required to obtain a higher level of smoothness and flatness even in secondary polishing.

It is known that the surface roughness of a wafer can be reduced by using an amine-free polishing composition or by adding a water-soluble polymer to the polishing composition (see, for example, Japanese Patent No. 5505987). .).

Japanese Patent No. 5505987

On the other hand, secondary polishing also requires a high polishing rate. Amine-free polishing compositions have the problem that a sufficient polishing rate cannot be obtained.

Further, the polishing composition is generally transported and stored in a concentrated state, and diluted to an optimum concentration for use during polishing. In order to reduce transportation and storage costs, it is preferable to make the concentration of the polishing composition as high as possible. However, if the concentration is too high, there is a problem that the abrasive grains in the polishing composition agglomerate and the storage stability deteriorates.

An object of the present invention is to provide a polishing composition which can provide a high polishing rate and which has good storage stability even at a high concentration.

A polishing composition according to one embodiment of the present invention comprises abrasive grains, a basic compound, and water, wherein the basic compound has 3 or 4 nitrogen atoms in its molecular structure and a first basic compound that is a nitrogen-containing basic compound having 2 to 9 nitrogen atoms, and a second basic compound that is a nitrogen-containing basic compound having 1 or 2 nitrogen atoms in the molecular structure; and the weight ratio of the abrasive grains and the basic compound is abrasive grains:basic compound=1:0.05 to 1:0.2.

Said first basic compound is preferably diethylenetriamine.

The second basic compound is preferably one selected from the group consisting of quaternary ammonium salts, N-(2-aminoethyl)-2-aminoethanol, ammonium hydroxide, and 2-hydroxyethylaminopropylamine. Seeds.

The polishing composition is preferably used for polishing silicon wafers.

ADVANTAGE OF THE INVENTION According to this invention, the polishing composition which can obtain a high polishing rate and has favorable storage stability even if it is high concentration is obtained.

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

A high polishing rate can be obtained by using an amine as the basic compound. In particular, a nitrogen-containing basic compound having 3 or 4 nitrogen atoms in the molecular structure and 2 to 9 carbon atoms (hereinafter referred to as the "first basic compound") has a particularly high polishing property. You get a rate. However, a polishing composition containing only the first basic compound as a basic compound has a problem in storage stability.

As a basic compound, in addition to the first basic compound, a nitrogen-containing basic compound having 1 or 2 nitrogen atoms in the molecular structure (hereinafter referred to as "second basic compound") is contained. , it is possible to improve the storage stability while achieving a high polishing rate. Also, the surface roughness and wafer shape can be made to be the same as the conventional performance.

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

A polishing composition according to one embodiment of the present invention comprises abrasive grains, a basic compound, and water. The polishing composition according to the present embodiment is suitably used for polishing silicon wafers, particularly for secondary polishing of silicon wafers.

Abrasive grains 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. Among these, colloidal silica is preferably used.

The content of abrasive grains is, but not limited to, 0.1 to 15% by weight of the entire polishing composition (undiluted solution). The content of abrasive grains is preferably large from the viewpoint of increasing the polishing rate, and preferably small from the viewpoint of reducing polishing scratches and remaining foreign matter. The lower limit of the content of abrasive grains is preferably 0.5% by weight, more preferably 1% by weight. The upper limit of the content of abrasive grains is preferably 12% by weight, more preferably 10% by weight.

The basic compound reacts efficiently with the wafer surface and contributes to the polishing properties of chemical mechanical polishing (CMP). Basic compounds are, for example, amine compounds, inorganic alkali compounds, and the like.

The polishing composition according to the present embodiment includes, as a basic compound, a nitrogen-containing basic compound having 3 or 4 nitrogen atoms in the molecular structure and 2 to 9 carbon atoms (first basic compounds), and nitrogen-containing basic compounds having one or two nitrogen atoms in the molecular structure (second basic compounds).

A nitrogen-containing basic compound (first basic compound) having 3 or 4 nitrogen atoms and 2 to 9 carbon atoms in its molecular structure particularly contributes to improving the polishing rate. In addition, a nitrogen-containing basic compound having 3 or 4 nitrogen atoms and 2 to 9 carbon atoms in the molecular structure contributes greatly to the polishing rate, but it is not effective for surface roughness and wafer shape. less adverse effects.

Nitrogen-containing basic compounds having 3 nitrogen atoms and 2 to 9 carbon atoms in the molecular structure include, for example, pentamethyldiethylenetriamine and N-(2-aminoethyl)piperazine (N-AEP). , 1-amino-4-methylpiperazine, bis(3-aminopropyl)amine, 1,1,3,3-tetramethylguanidine, diethylenetriamine (DETA) and the like.

Nitrogen-containing basic compounds having 4 nitrogen atoms and 2 to 9 carbon atoms in the molecular structure include, for example, triethylenetetramine (TETA) and arginine.

Among the groups of substances described above, the first basic compound is preferably a nitrogen-containing basic compound in which the number of nitrogen atoms in the molecular structure is 3 and the number of carbon atoms is 2 to 9. Nitrogen-containing basic compounds having 3 nitrogen atoms and 3 to 8 carbon atoms are more preferred, and DETA is particularly preferred.

A nitrogen-containing basic compound (second basic compound) having 1 or 2 nitrogen atoms in the molecular structure is included together with the above-described first basic compound to improve the storage stability of the polishing composition. noticeably improve sexuality.

Nitrogen-containing basic compounds having one nitrogen atom in the molecular structure include, for example, ammonium hydroxide, quaternary ammonium salts, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, butylamine, isobutylamine, tert -Butylamine, hexylamine, cyclohexylamine, monoethanolamine, diethanolamine, triethanolamine and the like. Examples of quaternary ammonium salts include tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrabutylammonium hydroxide (TBAH), ethyltrimethylammonium hydroxide, trimethyl-2-hydroxyethylammonium hydroxide, dimethylbis(2-hydroxyethyl)ammonium hydroxide and the like.

Nitrogen-containing basic compounds having two nitrogen atoms in the molecular structure include, for example, 1,4-diazabicyclo[2,2,2]octane, N-(2-hydroxyethyl)-1,3-propanediamine , N-(2-aminoethyl)-2-aminoethanol (AEEA), ethylenediamine, 1,3-propanediamine, 1,2-propanediamine, 1,4-butanediamine, hexamethylenediamine, dimethylaminopropylamine, diethylaminopropylamine, tetramethyl-1,3-diaminopropane, 1,5-diazabicyclo[4,3,0]non-5-ene, 1,8-diazabicyclo[5,4,0]undec-7-ene, 1-methylpiperazine, 2-methylpiperazine, anhydrous piperazine, piperazine hexahydrate, piperazine hydrochloride, homopiperazine and the like.

Among the substance groups described above, the second basic compound is particularly preferably a quaternary ammonium salt, N-(2-aminoethyl)-2-aminoethanol, ammonium hydroxide, and 2-hydroxyethylaminopropylamine. .

The polishing composition according to this embodiment may further contain other basic compounds in addition to the above-described first basic compound and second basic compound. That is, the polishing composition according to the present embodiment includes a nitrogen basic compound containing 5 or more nitrogen atoms in the molecular structure, or a nitrogen basic compound containing 3 or 4 nitrogen atoms in the molecular structure and the number of carbon atoms may contain 1 or 10 or more nitrogen-containing basic compounds or inorganic basic compounds.

Examples of nitrogen-containing basic compounds having 5 or more nitrogen atoms in the molecular structure include tetraethylenepentamine and pentaethylenehexamine.

Nitrogen-containing basic compounds having 3 or 4 nitrogen atoms and 1, 10 or more carbon atoms in the molecular structure are, for example, 1,4-bis(3-aminopropyl)piperazine, hexamethyltri Ethylene tetramine etc. are mentioned.

Inorganic basic compounds are, for example, alkali metal hydroxides, alkali metal carbonates, alkali metal hydrogen carbonates, alkaline earth metal hydroxides, alkaline earth metal carbonates, alkaline earth metal and the like. Examples of inorganic alkaline compounds include potassium hydroxide (KOH), sodium hydroxide, potassium hydrogen carbonate, potassium carbonate (K ₂ CO ₃ ), sodium hydrogen carbonate, sodium carbonate, and the like.

In the polishing composition according to the present embodiment, the weight ratio of abrasive grains to basic compound is abrasive grains to basic compound=1:0.05 to 1:0.20. The weight of the basic compound means the total amount of the first basic compound, the second basic compound, and other basic compounds in the polishing composition. If the weight ratio of the basic compound to the abrasive grains is less than 0.05, the effect of the basic compound cannot be sufficiently obtained when diluted to an appropriate concentration. On the other hand, if the weight ratio of the basic compound to the abrasive grains is greater than 0.20, the shape of the wafer after polishing deteriorates. The lower limit of the weight ratio of the basic compound to the abrasive grains is preferably 0.07. The upper limit of the weight ratio of the basic compound to the abrasive grains is preferably 0.18, more preferably 0.15.

The content of the basic compound is, but not limited to, 0.3 to 1.2% by weight of the entire polishing composition (undiluted solution).

The polishing composition according to this embodiment may further contain a water-soluble polymer. The water-soluble polymer adsorbs to the surface of the wafer and modifies the surface of the wafer. This improves polishing uniformity and reduces surface roughness.

Water-soluble polymers include, for example, celluloses such as hydroxyethylcellulose (HEC), hydroxyethylmethylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, cellulose acetate, and methylcellulose; vinyl polymers such as polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP); Glycosides (glycosides), polyethylene glycol, polypropylene glycol, polyglycerin, N,N,N',N'-tetrakis/polyoxyethylene/polyoxypropylene/ethylenediamine (poloxamine), poloxamer, polyoxyalkylene alkyl ether, poly Oxyalkylene fatty acid esters, polyoxyalkylenealkylamines, alkylene oxide derivatives of methylglucoside, polyhydric alcohol alkylene oxide adducts, polyhydric alcohol fatty acid esters, and the like can be mentioned.

The content of the water-soluble polymer is not limited to this, but for example, the weight ratio of the abrasive grains: water-soluble polymer = 1:0.0001 to 1:0.01, and the polishing composition ( Stock solution) 0.0001 to 0.1% by weight of the whole. If the content of the water-soluble polymer is too low, the effect cannot be sufficiently obtained. On the other hand, if the content of the water-soluble polymer is too high, the polishing rate will decrease and the shape of the wafer after polishing will deteriorate. The lower limit of the water-soluble polymer content is preferably 0.001% by weight, more preferably 0.002% by weight. The upper limit of the water-soluble polymer content is preferably 0.05% by weight, more preferably 0.03% by weight.

The polishing composition according to this embodiment may further contain a chelating agent. Chelating agents include, for example, aminocarboxylic acid chelating agents and organic phosphonic acid chelating agents.

Specific examples of aminocarboxylic acid-based chelating agents include ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetate, nitrilotriacetic acid, sodium nitrilotriacetate, ammonium nitrilotriacetate, hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetate, diethylenetriaminepentaacetic acid (DTPA), sodium diethylenetriaminepentaacetate, triethylenetetraminehexaacetic acid, sodium triethylenetetraminehexaacetate and the like.

Specific examples of organic phosphonic acid-based chelating agents include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri(methylenephosphonic acid), ethylenediaminetetrakis(methylenephosphonic acid), diethylenetriaminepenta (methylene phosphonic acid), ethane-1,1,-diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, ethane-1-hydroxy-1,1, 2-triphosphonic acid, ethane-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid, and α-methylphosphonosuccinic acid.

Although the content of the chelating agent is not limited to this, for example, the weight ratio of the abrasive grains to the chelating agent is 1:0.0001 to 1:0.01, and the entire polishing composition (undiluted solution) is 0.001 to 0.10% by weight of the

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 can optionally contain compounding agents generally known in the field of polishing compositions.

The polishing composition according to the present embodiment is produced by appropriately mixing abrasive grains, a basic compound and other compounding materials and adding water. Alternatively, the polishing composition according to the present embodiment is produced by sequentially mixing abrasive grains, a basic compound and other compounding materials with water. As 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 used for polishing silicon wafers after being diluted with water to an appropriate concentration. The dilution ratio is, for example, 10 to 60 times. It is preferable to dilute and use the basic compound so that the concentration of the diluted basic compound is 0.01 to 0.2% by weight.

EXAMPLES The present invention will be described in more detail below with reference to examples. The invention is not limited to these examples.

Polishing compositions of Examples 1 to 40 and Comparative Examples 1 to 17 shown in Tables 1 to 7 were prepared.

Table 8 summarizes the number of carbon atoms and the number of nitrogen atoms in each basic compound.

The polishing compositions in Tables 1 to 7 contained colloidal silica having an average secondary particle size of 70 nm as abrasive grains and DTPA as a chelating agent. Also, some of the polishing compositions contained HEC with a weight average molecular weight of 500,000. All the contents described in Tables 1 to 7 are before dilution, and the balance of the polishing composition is water.

Using the polishing compositions of these Examples and Comparative Examples, the surface of a P-type silicon wafer (100) with a diameter of 300 mm was polished. SPP800S manufactured by Okamoto Machine Tool Co., Ltd. was used as a polishing apparatus. A non-woven fabric polishing pad was used as the polishing pad. The polishing composition was diluted 20 times (10 times only in Comparative Example 1) and supplied at a supply rate of 0.6 L/min. Polishing was performed for 4 minutes at a surface plate rotation speed of 33 rpm, a head rotation speed of 30 rpm, a load on the guide of 0.016 MPa, and a load on the wafer of 0.011 MPa.

After polishing, the surface roughness Ra of the silicon wafer was measured using a non-contact surface roughness measuring machine (Wyco NT9300, manufactured by Veeco).

The wafer shape and polishing rate were evaluated as follows using a wafer flatness inspection device (Nanometro 300TT-A, manufactured by Kuroda Seiko Co., Ltd.).

The wafer shape was evaluated based on the flatness of the outer periphery of the wafer measured by Nanometro 300TT-A. The flatness of the wafer outer periphery is calculated from the average of the radial analysis data of the specified range of the wafer outer periphery, and the difference in flatness of the wafer outer periphery before and after polishing (before polishing - after polishing) is 0. , the shape of the outer peripheral portion of the wafer before polishing is maintained. The specified range of the wafer outer periphery is a range obtained by further dividing the wafer outer periphery 114 mm to 149 mm when the wafer center is 0 into 72 cells at a division angle of 5 °. The flatness is the average value of the values of each cell divided by 72.

The polishing rate was obtained by measuring the thickness profile of the silicon wafer before and after polishing and dividing the average value of the difference by the polishing time.

The storage stability was evaluated by allowing the polishing composition to stand in an atmosphere of 50°C for 30 days and measuring the difference between the initial average particle size and the average particle size after 30 days at 50°C. The average particle size is the average particle size measured using a dynamic light scattering method. The average particle size was measured using a particle size measurement system "ELS-Z2" manufactured by Otsuka Electronics Co., Ltd.

Tables 1 to 7 show the polishing rate, surface roughness Ra, difference in flatness of the outer periphery of the wafer, and variation in average particle size. The numerical values of the polishing rate and the surface roughness Ra are relative values when Comparative Example 1 is set to 100. In this evaluation, the targets were a polishing rate of 120 or higher, a surface roughness of 110 or lower, a flatness difference of ±0.05 μm or less at the outer periphery of the wafer, and a variation of average particle size of ±5 nm or less.

As shown in Tables 1 to 7, the polishing compositions of Examples 1 to 40 all satisfied the above evaluation criteria.

The polishing compositions of Comparative Examples 2-7 did not contain a second basic compound. Therefore, the storage stability was poor. The polishing composition of Comparative Example 8 did not contain the first basic compound, and the difference in the flatness of the outer periphery of the wafer was unfavorable. The polishing composition of Comparative Example 9 had a low basic compound content and a poor polishing rate. The polishing composition of Comparative Example 10 did not contain the first basic compound and had a poor polishing rate. The polishing compositions of Comparative Examples 11 to 17 contained too much basic compound, and the difference in the flatness of the outer periphery of the wafer was unfavorable.

From the above results, by containing appropriate amounts of the first basic compound and the second basic compound, a high polishing rate and a good wafer shape can be obtained, and good storage stability can be achieved even at high concentrations. It was confirmed that a polishing composition having

The embodiments of the present invention have been described above. The above-described embodiments are merely examples for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and can be implemented by appropriately modifying the above-described embodiment without departing from the spirit of the present invention.

Claims (4)

abrasive grains;
a basic compound;
including water;
The basic compound is
a first basic compound which is a nitrogen-containing basic compound whose molecular structure has 3 or 4 nitrogen atoms and 2 to 9 carbon atoms;
and a second basic compound that is a nitrogen-containing basic compound having one or two nitrogen atoms in the molecular structure,
The weight ratio of the abrasive grains and the basic compound is abrasive grains:basic compound=1:0.05 to 1: 0.08 ,
The first basic compound includes pentamethyldiethylenetriamine, N-(2-aminoethyl)piperazine, 1-amino-4-methylpiperazine, bis(3-aminopropyl)amine, 1,1,3,3-tetra One selected from the group consisting of methylguanidine, diethylenetriamine, triethylenetetramine, and arginine,
The second basic compound is ammonium hydroxide, quaternary ammonium salt, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, butylamine, isobutylamine, tert-butylamine, hexylamine, cyclohexylamine, monoethanolamine. , diethanolamine, triethanolamine, 1,4-diazabicyclo[2,2,2]octane, N-(2-hydroxyethyl)-1,3-propanediamine, N-(2-aminoethyl)-2-aminoethanol , ethylenediamine, 1,3-propanediamine, 1,2-propanediamine, 1,4-butanediamine, hexamethylenediamine, dimethylaminopropylamine, diethylaminopropylamine, tetramethyl-1,3-diaminopropane, 1,5 -diazabicyclo[4,3,0]non-5-ene, 1,8-diazabicyclo[5,4,0]undec-7-ene, 1-methylpiperazine, 2-methylpiperazine, anhydrous piperazine, piperazine hexahydrate A polishing composition which is one selected from the group consisting of a compound, piperazine hydrochloride and homopiperazine . The polishing composition according to claim 1,
The polishing composition, wherein the first basic compound is diethylenetriamine. The polishing composition according to claim 1 or 2,
The second basic compound is one selected from the group consisting of quaternary ammonium salts, N-(2-aminoethyl)-2-aminoethanol, ammonium hydroxide, and 2-hydroxyethylaminopropylamine. , polishing composition. The polishing composition according to any one of claims 1 to 3,
The polishing composition is a polishing composition used for polishing a silicon wafer.