Polishing composition

Abstract

To provide a polishing composition capable of more reducing minute defects and haze of a semiconductor after polishing.SOLUTION: A composition for semiconductor polishing includes a silica, hydroxyethyl cellulose, basic compound and water. The weight average molecular weight of hydroxyethyl cellulose is 2.0×105 or more but 1.0×106 or less. The average particle diameter D of particles included in the composition measured by a dynamic light scattering method in the concentration at which the content of silica becomes 0.2 mass% is more than 60nm but less than 100nm, and D-D2, which is a value in which the secondary particle diameter D2 of silica is subtracted from the average particle diameter D of particles is less than 12nm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polishing composition. [Background technology]

[0002] CMP polishing of semiconductor wafers involves multiple stages of polishing to achieve highly accurate smoothing and flattening. The main purpose of the final polishing process is to reduce micro-defects and haze (surface cloudiness).

[0003] Polishing compounds used in the final polishing process of semiconductor wafers generally contain water-soluble polymers such as hydroxyethyl cellulose (HEC). Water-soluble polymers have the role of making the semiconductor wafer surface hydrophilic, suppressing damage to the semiconductor wafer caused by abrasive grain adhesion to the surface, excessive chemical etching, and abrasive grain aggregation. This is known to reduce micro-defects and haze.

[0004] In order to reduce micro defects and haze, it is necessary to appropriately adjust the strength of the polishing action of the abrasive grains and the particles in the polishing composition (composite of abrasive grains and water-soluble polymer). Japanese Patent No. 6387032 describes a polishing composition containing a cellulose derivative and a nonionic surfactant, in which the average primary particle diameter D of the abrasive grains is P1 is 20 to 30 nm, and the average secondary particle diameter D P2 is 20 to 55 nm, and the volume average particle diameter D A A method for polishing silicon wafers using a polishing composition having a surface roughness of 20 to 60 nm is disclosed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6387032 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, as design rules for semiconductor devices have become increasingly finer, stricter control of micro-defects and haze on the surface of semiconductor wafers is required.

[0007] An object of the present invention is to provide a polishing composition that can further reduce microdefects and haze in a semiconductor after polishing. [Means for solving the problem]

[0008] A polishing composition according to one embodiment of the present invention is a polishing composition for polishing semiconductors, and comprises silica, hydroxyethyl cellulose, a basic compound, and water, wherein the weight-average molecular weight of the hydroxyethyl cellulose is 2.0×10 5 Over 1.0 x 10 6 The average particle diameter D of the particles contained in the polishing composition measured by dynamic light scattering at a concentration such that the silica content is 0.2 mass % is greater than 60 nm and less than 100 nm, and the value D-D2 obtained by subtracting the secondary particle diameter D2 of the silica from the average particle diameter D of the particles is less than 12 nm. [Effects of the Invention]

[0009] According to the present invention, microdefects and haze in a polished semiconductor can be further reduced. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present inventors have conducted various studies to solve the above problems. As a result, it has been found that the weight average molecular weight of hydroxyethyl cellulose is 2.0×10 5 Over 1.0 x 10 6It has been found that a polishing composition exhibiting superior polishing performance can be obtained when the average particle diameter D of the particles contained in the polishing composition measured by dynamic light scattering at a concentration such that the silica content is 0.2 mass% or less is more than 60 nm and less than 100 nm, and the value D-D2 obtained by subtracting the secondary particle diameter D2 of the silica from the average particle diameter D of the particles is less than 12 nm.

[0011] The present invention has been completed based on the above findings. A polishing composition according to one embodiment of the present invention will be described in detail below.

[0012] A polishing composition according to one embodiment of the present invention contains silica, hydroxyethyl cellulose (hereinafter referred to as "HEC"), a basic compound, and water.

[0013] The silica contained in the polishing composition according to this embodiment is, for example, colloidal silica or fumed silica, with colloidal silica being more preferred. Some silica particles are formed by agglomeration of primary particles. Generally, the particle size calculated from the BET specific surface area is referred to as the primary particle size, and the particle size measured by dynamic light scattering is referred to as the secondary particle size. Hereinafter, the primary particle size of the silica contained in the polishing composition according to this embodiment will be referred to as the "primary particle size D1," and the secondary particle size will be referred to as the "secondary particle size D2."

[0014] In the polishing composition according to this embodiment, the primary particle diameter D1 of silica is not particularly limited, and is, for example, 10 to 40 nm, although not limited thereto.

[0015] In the polishing composition according to this embodiment, the secondary particle diameter D2 of silica is not particularly limited. However, as will be described later in this embodiment, the average particle diameter D of the particles formed by silica and HEC must be greater than 60 nm and less than 100 nm. If the secondary particle diameter D2 is significantly outside this range, it may be difficult to achieve an average particle diameter D of the particles formed by silica and HEC greater than 60 nm and less than 100 nm. The secondary particle diameter D2 is preferably 40 to 95 nm. The lower limit of the secondary particle diameter D2 is more preferably 50 nm, and even more preferably 60 nm. The upper limit of the secondary particle diameter D2 is more preferably 90 nm, and even more preferably 85 nm.

[0016] The silica contained in the polishing composition according to this embodiment is, but is not limited to, a silica having a surface silanol group density of 3.0 OH / nm 2 It is preferable that the density of silanol groups on the surface is 3.0 OH / nm or less. 2 The haze can be further reduced by using the following silica: The upper limit of the density of silanol groups on the surface is preferably 2.5 OH / nm 2 and more preferably 2.0 OH / nm 2 The lower limit of the density of silanol groups on the surface is not particularly limited, but is, for example, 1.0 OH / nm 2 is.

[0017] The content of silica is not particularly limited, but is, for example, 0.20 to 20 mass% of the total polishing composition (undiluted). The polishing composition is, for example, diluted 10 to 100 times before use during polishing. The polishing composition according to this embodiment is preferably diluted so that the silica content is 100 to 5000 ppm (ppm by mass; the same applies hereinafter).

[0018] The HEC contained in the polishing composition according to this embodiment has a weight average molecular weight of 2.0 × 10 5 Over 1.0 x 10 6 The weight average molecular weight of HEC is 2.0 × 10 5 Even if it is less than 1.0 × 10 6If the weight average molecular weight of HEC exceeds 2.5×10, micro defects on the polished wafer increase. 5 and more preferably 3.0 × 10 5 and more preferably 3.5 × 10 5 and more preferably 4.0 × 10 5 The upper limit of the weight average molecular weight of HEC is preferably 8.0 × 10 5 and more preferably 6.0 × 10 5 is.

[0019] The content of HEC is not particularly limited, but is, for example, 0.01 to 1.2 mass % of the total polishing composition (undiluted).

[0020] The basic compound reacts efficiently with the wafer surface and contributes to the polishing performance of chemical mechanical polishing (CMP). Examples of the basic compound include ammonia, ammonium compounds, amine compounds, and inorganic alkali compounds.

[0021] Examples of ammonium compounds include ammonium salts, quaternary ammonium hydroxides, etc. Specific examples include tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrabutylammonium hydroxide (TBAH), etc.

[0022] Examples of the amine compound include primary amines, secondary amines, tertiary amines, heterocyclic amines, and salts thereof. Specific examples include 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, and guanidine carbonate.

[0023] Examples of inorganic alkali compounds include alkali metal hydroxides, alkali metal salts, alkaline earth metal hydroxides, alkaline earth metal salts, etc. Specific examples of inorganic alkali compounds include potassium hydroxide, sodium hydroxide, potassium bicarbonate, potassium carbonate, sodium bicarbonate, sodium carbonate, etc.

[0024] The basic compounds may be used alone or in combination of two or more. Among the basic compounds, alkali metal hydroxides, alkali metal salts, ammonia, ammonium salts, and quaternary ammonium hydroxides are particularly preferred.

[0025] The content of the basic compound (when two or more types are contained, the total amount) is not particularly limited, but is, for example, 0.01 to 1.5 mass % of the entire polishing composition (undiluted solution).

[0026] In the polishing composition of this embodiment, the average particle diameter D of the particles contained in the polishing composition measured by dynamic light scattering at a concentration such that the silica content is 0.2 mass % is more than 60 nm and less than 100 nm.

[0027] In polishing compositions containing HEC and silica, a portion of the HEC may be adsorbed onto the surface of the silica, forming particles (hereinafter simply referred to as "particles") consisting of a composite of HEC and silica. When the size of these particles in the polishing composition is measured by dynamic light scattering, the measured value may be larger than the secondary particle size of the silica.

[0028] In this embodiment, the average particle diameter D measured by dynamic light scattering at a concentration where the silica content in the polishing composition is 0.2 mass % is used as an index of the particle size.

[0029] By setting the average particle diameter D of the particles to be more than 60 nm and less than 100 nm, microdefects and haze after polishing can be reduced. The lower limit of the average particle diameter D of the particles is preferably 65 nm or more, and more preferably 70 nm or more. The upper limit of the average particle diameter D of the particles is preferably 90 nm or less, and more preferably 85 nm or less.

[0030] Furthermore, the polishing composition according to this embodiment has a value D-D2 (hereinafter simply referred to as "D-D2") obtained by subtracting the secondary particle diameter D2 of silica from the average particle diameter D of the particles, which is less than 12 nm. D-D2 can be considered an index of the thickness of the organic protective layer on the silica surface. If the protective layer is too thick, aggregation of particles is likely to occur, increasing the number of micro-defects. Furthermore, if the protective layer is too thick, when particles are pressed against the wafer during polishing, the probability that the hard silica surface not covered by the protective layer will come into direct contact with the wafer decreases, making it difficult to eliminate micro-irregularities and making it impossible to reduce haze.

[0031] D-D2 is preferably 10 nm or less, more preferably 8 nm or less, even more preferably 5 nm or less, and even more preferably 3 nm or less.

[0032] D-D2 can be adjusted by the density of silanol groups on the surface of the silica, the type of HEC, the compounding ratio of silica to HEC, the content of the basic compound, and the like.

[0033] For example, as the number of silanol groups on the surface of secondary silica particles increases, the number of points on which HEC can be adsorbed increases, and D-D2 tends to increase.

[0034] The higher the weight-average molecular weight of HEC, the larger D-D2 tends to be. Furthermore, the higher the amount of HEC blended relative to the amount of silica blended, the larger D-D2 tends to be. Furthermore, D-D2 can be altered by changing the structure of HEC, particularly the degree of ethylene oxide substitution (an indicator showing how many of the three hydroxyl groups per glucose ring are substituted with ethylene oxide) and the degree of addition (the number of ethylene oxides added per glucose ring).

[0035] Increasing the content of basic compounds tends to suppress the adsorption of HEC to silica, resulting in a smaller D-D2. Furthermore, the selection of a nonionic surfactant, as described below, can also suppress the adsorption of HEC to silica, potentially reducing D-D2.

[0036] The average particle size D of the particles can be adjusted by the secondary particle size D2 of the silica and the above-mentioned D - D2. The larger the secondary particle size D2 of the silica, the larger the average particle size D of the particles tends to be. The secondary particle size D2 of the silica and the number of silanol groups can be adjusted by the silica synthesis conditions (solvent, catalyst composition, reaction temperature, reaction time, etc.).

[0037] The polishing composition according to this embodiment may further contain a nonionic surfactant.

[0038] Examples of nonionic surfactants suitable for the polishing composition of this embodiment include ethylenediaminetetrapolyoxyethylenepolyoxypropylene (poloxamine), poloxamer, polyoxyalkylene alkyl ether, polyoxyalkylene fatty acid ester, polyoxyalkylene alkylamine, polyoxyalkylene methyl glucoside, etc.

[0039] Examples of ethylenediaminetetrapolyoxyethylenepolyoxypropylene include N,N,N',N'-tetrakispolyoxyethylenepolyoxypropyleneethylenediamine. Examples of polyoxyalkylene alkyl ethers include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, etc. Examples of polyoxyalkylene fatty acid esters include polyoxyethylene monolaurate, polyoxyethylene monostearate, etc. Examples of polyoxyalkylene alkylamines include polyoxyethylene laurylamine, polyoxyethylene oleylamine, etc. Examples of polyoxyalkylene methylglucosides include polyoxyethylene methylglucoside, polyoxypropylene methylglucoside, etc.

[0040] The content of the nonionic surfactant (when two or more types are contained, the total amount) is not particularly limited, but is, for example, 0.1 to 1000 ppm of the entire polishing composition (undiluted solution).

[0041] 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 to 12.0.

[0042] The balance of the polishing composition according to this embodiment is mainly water. In addition to the above, the polishing composition according to this embodiment can optionally contain compounding ingredients generally known in the field of polishing compositions.

[0043] The polishing composition according to this embodiment is prepared by appropriately mixing silica, HEC, a basic compound, and other compounding ingredients and adding water. Alternatively, the polishing composition according to this embodiment can be prepared by sequentially mixing silica, HEC, a basic compound, and other compounding ingredients with water. These components can be mixed using a homogenizer, ultrasonic waves, or other means commonly used in the technical field of polishing compositions. It is preferable that each component contained in the polishing composition is filtered through a filter immediately before production.

[0044] The polishing composition described above is used for polishing semiconductors after being diluted with water to an appropriate concentration. The polishing composition according to this embodiment is suitable for polishing silicon wafers (bare wafers), particularly for finish polishing. [Example]

[0045] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0046] Several polishing compositions were prepared by varying the type of silica and HEC in the formulations shown in Table 1. All HEC solutions were filtered through a filter with a mesh size of 0.65 μm before use. The contents in Table 1 are those before dilution (undiluted solution), and the remainder is water.

[0047] [Table 1]

[0048] Each polishing composition was diluted so that the silica content was 0.2 mass %, and then the average particle diameter D of the particles in the polishing composition was measured using ELS-Z manufactured by Otsuka Electronics Co., Ltd.

[0049] These polishing compositions were used to polish 12-inch silicon wafers. The polishing apparatus used was a single-sided polishing apparatus with a platen having an outer diameter of 31.5 inches. A nap pad was used as the polishing pad. The polishing composition was diluted 21 times and supplied at a supply rate of 600 mL / min. Polishing was performed under the following conditions: platen rotation speed: 52 rpm, carrier rotation speed: 50 rpm, guide load: 16 kPa, and wafer load: 12 kPa. Prior to polishing with the polishing compositions of the Examples and Comparative Examples, preliminary polishing was performed for 2.5 minutes using a polishing slurry, Nanopure (registered trademark) NP7050S (manufactured by Nitta DuPont Co., Ltd.).

[0050] The micro-defects and haze of the polished silicon wafers were measured. Micro-defects were measured using a wafer surface inspection system MAGICS M5640 (manufactured by Lasertec). Haze was measured using a wafer surface inspection system Surfscan SP2 (manufactured by KLA Tencor).

[0051] The results are shown in Table 2. The values in the "Defect" and "Haze" columns in Table 2 are relative values when the number of microdefects and the haze value of Comparative Example 1 are set to 100, respectively. As an overall evaluation, samples in which both the microdefects and the haze were improved compared to Comparative Example 1 were evaluated as "passable," and samples in which both the microdefects and the haze were improved by 10% or more compared to Comparative Example 1 were evaluated as "excellent." Samples in which either the microdefects or the haze were worse than those of Comparative Example 1 were evaluated as "fail."

[0052] [Table 2]

[0053] Comparative Example 1 is a polishing composition that was adjusted based on Japanese Patent No. 6387032 so that 20 nm≦D1≦30 nm, 20 nm≦D2≦55 nm, and 20 nm≦D≦60 nm.

[0054] As shown in Table 2, all of the polishing compositions of Examples 1 to 6 exhibited superior polishing performance to that of Comparative Example 1. In particular, when the weight average molecular weight of HEC was 3.0 × 10 5 Over 1.0 x 10 6 The density of silanol groups on the surface of the silica is 3.0 OH / nm 2 The polishing compositions of Examples 1 to 3, which were as follows, showed improvements of 10% or more in both microdefects and haze compared to the polishing composition of Comparative Example 1.

[0055] The polishing performance of the polishing composition of Comparative Example 2 was inferior to that of Comparative Example 1 in terms of both microdefects and haze. This is thought to be because D-D2 was too large.

[0056] The polishing performance of the polishing composition of Comparative Example 3 was superior in terms of haze to that of Comparative Example 1, but inferior in terms of microdefects. This is thought to be because the average particle diameter D was too large.

[0057] The polishing performance of the polishing composition of Comparative Example 4 was comparable in terms of haze to that of Comparative Example 1, but was inferior in terms of microdefects. This is thought to be because the weight-average molecular weight of HEC was too large.

[0058] The polishing performance of the polishing composition of Comparative Example 5 was comparable in terms of haze to that of Comparative Example 1, but was inferior in terms of microdefects. This is thought to be because the weight-average molecular weight of HEC was too small.

[0059] 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 embodiments, and the above-described embodiments can be appropriately modified and carried out without departing from the spirit of the present invention.

Claims

1. A polishing composition for semiconductor polishing, comprising: Silica and Hydroxyethyl cellulose, a basic compound; Water and a nonionic surfactant, The weight average molecular weight of the hydroxyethyl cellulose is 2.0 × 10 ５ Above 1.0 x 10 ６ is as follows: the average particle diameter D of particles contained in the polishing composition measured by a dynamic light scattering method at a concentration such that the silica content is 0.2 mass% is more than 60 nm and less than 100 nm; the value D-D2 obtained by subtracting the secondary particle diameter D2 of the silica from the average particle diameter D of the particles is 5 nm or less, A polishing composition wherein the density of silanol groups on the surface of the silica is 3.0 OH / nm 2 or less.

2. The polishing composition according to claim 1, The weight average molecular weight of the hydroxyethyl cellulose is 3.0 × 10 ５ Above 1.0 x 10 ６ A polishing composition comprising:

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