TW201529819A - Polishing composition, and semiconductor-wafer production method - Google Patents

Abstract

The present invention addresses the problem of providing a stable polishing composition with which a sufficient polishing rate can be achieved, and which exhibits little change in performance even if used repeatedly. This polishing composition includes colloidal silica, a weak acid salt, and a quaternary ammonium compound, and is used to polish semiconductor wafers. The weak acid salt content is in the range of 1.0 x 10<SP>-7</SP> to 1.0 x 10<SP>-5</SP> mol/m2-SiO2 with respect to the total surface area of the colloidal silica. The quaternary ammonium compound content satisfies the relationship set forth in formula (1), namely Y0=A*X+B, and formula (2), namely -20 ≤ (Y-Y0)/Y0 ≤ 100(%), with the caveat that, in the formulae, A represents the theoretical buffer ratio of the weak acid salt to the quaternary ammonium compound, B represents the amount of the quaternary ammonium compound which is adsorbed on the colloidal silica, and which is not free in the polishing composition, Y represents the quaternary ammonium compound content, Y0 represents the optimum amount of the quaternary ammonium compound, and X represents the weak acid salt content.

Description

Polishing composition and method of manufacturing semiconductor wafer

The present invention relates to a polishing composition and a method of manufacturing a semiconductor wafer using the same for polishing a semiconductor wafer.

In the past, various polishing compositions have been proposed as components for polishing semiconductor wafers and the like.

For example, Patent Document 1 proposes a cerium oxide sol and a cerium oxide gel as a polishing composition. Further, Patent Document 2 discloses that the polishing rate is increased by setting the pH of the suspension to be in the range of 10.5 to 12.5.

However, these techniques are slow in processing speed and inefficient in production, and in addition, pH is mostly changed due to changes in external conditions and lacks processing stability. That is, these techniques are time-consuming and difficult processing methods, and there is a problem that it is difficult to call an appropriate method. However, in recent years, with the increase in the integration of electronic circuits and the increase in the size of the wafer itself, it is necessary to flatten the surface of the wafer and the surface of the wafer of the semiconductor device. Further, in order to improve production efficiency, a polishing composition and a polishing method which are fast in processing speed are desired.

To solve these problems, a grinding composition has been disclosed. The composition is characterized by comprising a colloidal solution of colloidal cerium oxide having an average primary particle diameter of 8 to 500 nm of 1 to 15% by weight, and the colloidal solution is added by adding a combination of tetramethylammonium hydroxide and potassium hydrogencarbonate. The buffer solution having a buffering effect between pH 9.5 and 10.6 is prepared, and the conductivity at 25 ° C is not less than 20 mS/m and not more than 101 mS per 1% by weight of cerium oxide as colloidal cerium oxide. m. In this way, by using the polishing composition as a buffer solution and increasing the conductivity, a polishing composition having a small pH change and a high polishing rate is formed. When the polishing composition of the present invention is used, it is revealed that the quality of the polishing surface of the silicon wafer or the semiconductor device wafer is not deteriorated, and high-speed polishing can be performed stably (Patent Document 3).

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] US Patent No. 3170273

[Patent Document 2] US Patent No. 3328141

[Patent Document 3] Japanese Patent No. 4163785

However, even with the technique of Patent Document 3, it is not possible to achieve a sufficient polishing speed, and it cannot be said that it is a composition for a stable polishing which can provide a low performance change after repeated use.

Therefore, the object of the present invention is to provide a composition for a stable polishing which achieves a sufficient polishing rate and which is low in performance even if repeated use is changed. Things.

The inventors of the present invention have conducted an active review on the reason that the polishing composition disclosed in Patent Document 3 is polished, the polishing rate is still poor, and the repeated use is unstable. On the other hand, attention is paid to the presence of a water-soluble quaternary ammonium hydroxide (quaternary ammonium compound) which is adsorbed by the colloidal cerium oxide in the polishing composition and is not released in the polishing composition. The present invention has been completed by taking into consideration the conventionally unrecognized quaternary ammonium compound to prepare a polishing composition.

That is, the problem to be solved by the present invention is solved by providing a polishing composition comprising a colloidal cerium oxide, a weak acid salt, and a quaternary ammonium compound for use in polishing a semiconductor wafer. In the polishing composition used, the content of the weak acid salt is 1.0×10 ^-7 to 1.0×10 ^-5 mol/m ² -SiO ₂ relative to the total surface area of the colloidal cerium oxide, and the content of the above-mentioned 4-grade ammonium compound The relationship of the following formulas (1) and (2) is satisfied.

[Number 1] Y ₀ = A * X + B (1) -20 ≦ (YY ₀ ) / Y ₀ ≦ 100 (%) (2)

A: theoretical buffer ratio of grade 4 ammonium compound to weak acid salt

B: the amount of the ammonium compound of 4 is adsorbed by the colloidal cerium oxide, and is not released in the composition for polishing.

Y: content of grade 4 ammonium compound

Y ₀ : optimum amount of grade 4 ammonium compound

X: content of weak acid salt.

Hereinafter, embodiments of the present invention will be described. Further, the present invention is not limited to the following embodiments. In this specification, the expression "X~Y" means "not less than X and not more than Y", and "weight" and "quality", "% by weight" and "% by mass" and "parts by weight" and "quality" "Parts" are considered synonymous. Moreover, unless otherwise indicated, the measurement of the operation, physical properties, and the like is carried out under the conditions of room temperature (20 to 25 ° C) / relative humidity of 40 to 50%.

The present invention relates to a polishing composition comprising colloidal cerium oxide, a weak acid salt and a quaternary ammonium compound, which is a polishing composition used for polishing a semiconductor wafer, wherein the content of the weak acid salt is relative to the colloid The total surface area of the cerium oxide is 1.0 × 10 ^-7 to 1.0 × 10 ^-5 mol / m ^{2 -} SiO ₂ , and the content of the above-mentioned quaternary ammonium compound satisfies the relationship of the following formulas (1) and (2).

[Number 2] Y ₀ = A * X + B (1) -20 ≦ (YY ₀ ) / Y ₀ ≦ 100 (%) (2)

A: theoretical buffer ratio of grade 4 ammonium compound to weak acid salt

B: The fourth-order ammonium compound is adsorbed by colloidal cerium oxide, and is not released in the study. Amount in the grinding composition

Y: content of grade 4 ammonium compound

Y ₀ : optimum amount of grade 4 ammonium compound

X: content of weak acid salt.

According to the above configuration, a sufficient polishing speed can be achieved, and in particular, the initial polishing energy can be improved. Further, according to the polishing composition of the present invention, it is possible to provide a composition for a stable polishing which is low in repetitive use performance, and in particular, excellent in polishing rate retention.

The object to be polished which is polished by the polishing composition of the present invention is not particularly limited as long as it is a semiconductor wafer, and can be applied to a semiconductor wafer such as tantalum, aluminum, nickel, tungsten, copper, tantalum, titanium or stainless steel. Among them, the polishing composition of the present invention is suitable for polishing a germanium semiconductor wafer. Further, the shape of the object to be polished is not particularly limited. For example, it can be suitably applied to the polishing of a flat object to be polished such as a plate shape or a polyhedral shape. It may be an object to be polished which is composed of a plurality of materials of the above. Among them, the polishing composition of the present invention can be used for polishing a polishing object having a surface formed of a single crystal or a polycrystalline crucible.

The technical idea of the present invention will be described in detail below.

The polishing composition (especially the composition for double-side polishing) requires flatness controllability of the object to be polished, improvement of polishing energy, and cycle resistance. However, after the present invention is solved, it is possible to provide a sufficient polishing rate. In particular, it is a polishing composition having an initial polishing energy rate and having cycle resistance (that is, excellent polishing rate retention rate and stability). This cycle resistance means that when the polishing composition is circulated and polished, it can be reused plural times.

In a preferred embodiment of the invention, the polishing mechanism can be described as follows. That is, the polishing is performed by chemical etching by directly attacking the semiconductor wafer contained in the polishing composition. Further, as an effect other than the above, it is also important to operate by moving the alkali component onto the abrasive grains to the surface of the object to be polished. In the present invention, the polishing composition contains colloidal cerium oxide as the abrasive particles, but the "-OH" in the stanol group of the colloidal cerium oxide is extracted by the action of the alkali component, and becomes "-". O ^- ". It is considered that the polishing composition of the present invention contains a quaternary ammonium compound, and a cation derived from the quaternary ammonium compound (a preferred embodiment is tetramethylammonium ion) is adsorbed as a counter cation of "-O ^- ", and further Accelerate the grinding force.

Further, when the semiconductor wafer is provided with a surface formed of ruthenium, it is pulverized into a polishing solvent (colate derivative) by a polishing process, and is freed from a solvent constituting the polishing composition. The alkali component also has an effect of melting the polishing chips and suppressing clogging of the polishing pad. From the above viewpoints, when the polishing is effectively carried out, it is important that the alkali component is supplied to the abrasive grains, the substrate, and the polishing chips in a stable manner, that is, the pH is imparted.

In order to stabilize the pH of the polishing composition, that is, to supply "OH ^- " while maintaining "OH ^- ", the pH buffering action is utilized in the present invention.

For example, when buffering of carbonic acid (H ₂ CO ₃ ) and tetramethylammonium hydroxide (TMAOH) is considered, it can be understood from the following formula.

Carbonic acid (H ₂ CO ₃ ) and tetramethylammonium hydroxide (TMAOH) were considered to have the largest buffer at 1:2.

By maximizing the buffering action, even if the pH is lowered as the alkali component is supplied to the abrasive grains, the substrate, and the polishing chips during the polishing, the buffering can be quickly performed, so that the variation can be kept to a minimum. That is, based on the amount of the alkali component adsorbed on the surface of the abrasive particles, the buffer ratio of the alkali buffer component in the solvent of the polishing composition is set to be weak acid: strong base (mol ratio) = 1: A The present invention has been accomplished by the idea of obtaining maximum effect.

Considering the amount of non-adsorbed 4-grade ammonium compound (B) in the abrasive particles, and multiplying the weak acid salt content (X) by the theoretical buffer ratio (A) of the 4-grade ammonium compound and the weak acid salt, 4 The optimum value of the ammonium compound content (i.e., the optimum concentration) (Y ₀ ). Further, under active research by the present inventors, it has been found that if the content of the ammonium compound (Y) of the fourth-order ammonium is limited to the range of -20 to 100% of the optimum concentration (Y ₀ ), a sufficient polishing rate can be provided. In particular, the initial polishing energy rate can be improved, and even if the change in the performance of repeated use is low, in particular, the composition for a stable polishing which is excellent in the polishing rate retention rate.

Hereinafter, the description of each component contained in the polishing composition of the present invention will be carried out.

<colloidal cerium oxide>

The colloidal cerium oxide in the polishing composition has a physical effect on the surface to be polished, and is physically polished to the surface to be polished. There are also various types of abrasive grains. However, in the present invention, when colloidal cerium oxide is used, it is preferable in terms of reducing scratches on the surface of the semiconductor wafer due to polishing. These colloidal cerium oxides may be used singly or in combination of two or more. The colloidal cerium oxide used in the present invention is preferably produced by using an aqueous exchange method using water glass (Na).

The average primary particle diameter (BET particle diameter) of the colloidal cerium oxide in the polishing composition determined by the BET method is preferably not less than 10 nm, more preferably not less than 20 nm, more preferably not less than 30 nm, preferably not Less than 40 nm. The average primary particle diameter (BET particle diameter) obtained by determining the specific surface area of the colloidal cerium oxide by the BET method becomes such a size, and it is particularly easy to reduce the surface roughness or the step. Moreover, it is possible to improve, for example, the collapse of the edge of the wafer, and to improve the flatness of the wafer measured by GBIR, ESFQR, or the like. Further, by using a large abrasive grain of not less than 40 nm, there is an effect of improving the elimination of the protrusion locally present on the wafer.

Further, the average primary particle diameter (BET particle diameter) of the colloidal cerium oxide in the polishing composition obtained by the specific surface area measured by the BET method is preferably not more than 80 nm, more preferably not more than 70 nm, and more preferably not more than 60 nm. When the average primary particle diameter (BET particle diameter) obtained by determining the specific surface area of the colloidal cerium oxide by the BET method is such a size, the colloidal cerium oxide storage stability in the polishing composition can be further maintained. The term "storage stability" as used herein means that the polishing composition is stored in a container for a certain period of time. The stability of the composition itself and the stability associated with the polishing characteristics of the composition used in the grinding. Moreover, it has the effect of alleviating the sedimentation of cerium oxide when the polishing composition is stored for a long period of time.

Further, the total surface area (a) of the colloidal cerium oxide contained per 1 kg of the polishing composition is preferably not less than 150 (m ² -SiO ₂ /kg-slurry), more preferably not less than 250 (m ² -SiO ₂ /kg- The slurry) is preferably not less than 500 (m ² -SiO ₂ /kg-slurry), preferably not less than 1500 (m ² -SiO ₂ /kg-slurry). When the total surface area of the colloidal cerium oxide contained per 1 kg of the polishing composition is such a size, the polishing property of the polishing composition is further maintained. Further, the total surface area (a) of the colloidal cerium oxide contained per 1 kg of the polishing composition is preferably not more than 50,000 (m ^{2 -} SiO ₂ /kg-slurry), more preferably not more than 25,000 (m ^{2 -} SiO ₂ /kg - The slurry) is preferably not more than 5000 (m ² -SiO ₂ /kg-slurry), preferably not more than 3,500 (m ² -SiO ₂ /kg-slurry). When the total surface area of the colloidal cerium oxide contained per 1 kg of the polishing composition is the same, the effect of retaining the stability of the colloidal cerium oxide in the polishing composition is further maintained. According to this, the content of the colloidal cerium oxide and the specific (a) relating to the particle diameter are adjusted to the above range, and the polishing property of the polishing composition is further maintained for a long period of time.

Further, the total surface area (a) of the colloidal cerium oxide can be measured by using a surface area measuring device manufactured by Micromeritics Co., Ltd. under the trade name "Flow Sorb II 2300".

The true specific gravity of the colloidal cerium oxide in the polishing composition is preferably not less than 1.7, more preferably not less than 2.0, and more preferably not less than 2.1. The larger the true specific gravity of the colloidal cerium oxide, the easier it is to obtain a high grinding speed. The effect of reducing surface roughness or step is more easily improved. Further, there is an effect of improving, for example, the collapse of the edge of the wafer, improving the flatness of the wafer measured by GBIR, ESFQR, etc., and improving the elimination of abnormal protrusions locally. Further, the true specific gravity of the colloidal cerium oxide is calculated from the weight when the particles of the colloidal cerium oxide are dried and the weight when the ethanol having a known capacity is filled in the colloidal cerium oxide particles. Further, the upper limit is not particularly limited, but is preferably not more than 2.3, more preferably not more than 2.2.

The content of the colloidal cerium oxide in the polishing composition is preferably not less than 0.3% by mass, more preferably not less than 0.5% by mass, and still more preferably not less than 1.0% by mass. The more the content of the colloidal cerium oxide, the easier it is to obtain a high grinding speed and the effect of reducing the surface roughness or the step.

Moreover, since the colloidal cerium oxide itself functions as a weak acid, an additional buffering effect is exhibited by the presence of a strong base. That is, the more the content of the colloidal cerium oxide is, the more the OH ^- group on the surface of the cerium oxide is, so that the buffering action with the weak acid salt or the quaternary ammonium compound described later becomes strong, and the composition for polishing is The pH is more stable. Further, the colloidal cerium oxide content in the polishing composition is preferably not more than 50% by mass, more preferably not more than 30% by mass, and still more preferably not more than 10% by mass. When the content of the colloidal cerium oxide is such a degree, it is economical to further maintain the storage stability of the polishing composition.

<weak acid salt>

The polishing composition of the present invention contains a weak acid salt.

If the damping composition of the present invention is listed As an example of the weak acid salt used in the product, the valence is not limited, and from the viewpoint of effectively exerting the desired effect of the present invention, it is preferably a divalent, preferably divalent carbonate. .

As the weak acid salt, the composition for polishing of the present invention is as follows. That is, as an anion component constituting a salt, a carbonate ion, a hydrogencarbonate ion, and a monocarboxylic acid ion (for example, an acetate ion), a dicarboxylic acid ion (for example, an oxalic acid ion, a maleic acid ion), and a tricarboxylic acid ion are exemplified. (eg, citrate ion), borate ion, phosphate ion, and the like.

The cation component constituting the salt is exemplified by potassium ion, sodium ion, calcium ion, magnesium ion, manganese ion, cobalt ion, tetraalkylammonium ion, and tetraalkylphosphorus ion.

Among them, the cation component is preferably potassium, sodium or the like from the viewpoint of an effect of increasing the pH value after adding a weak acid salt (hereinafter referred to as "base strength"). Further, potassium is more effective than sodium in terms of the storage stability of colloidal cerium oxide in the polishing composition (hereinafter also referred to as "cerium oxide dispersion stability").

When the acid dissociation constant (pKa) is selected to be close to the pH 10 of the polishing composition as the anion component, the buffering action of the polishing composition can be more effectively exhibited. Among them, the anion component is preferably a carbonate ion, a hydrogencarbonate ion or a dicarboxylic acid ion.

In view of the above, specific examples are, for example, sodium carbonate, potassium carbonate, sodium hydrogencarbonate, potassium hydrogencarbonate, sodium acetate, potassium acetate, sodium propionate, potassium propionate, calcium carbonate, calcium hydrogencarbonate, calcium acetate, calcium propionate, acetic acid. Magnesium, magnesium propionate, zinc propionate, manganese acetate, cobalt acetate, and the like. Among them, the alkali in the dissolution From the viewpoint of strength and dispersion stability of cerium oxide, potassium carbonate or potassium hydrogencarbonate is preferred.

Further, the amount of the weak acid salt of the colloidal cerium oxide per 1 kg of the alkali metal (mol/kg-SiO ₂ ) in the polishing composition is preferably not less than 0.02 (mol/kg-SiO ₂ ), more preferably not less than 0.04 (mol) /kg-SiO ₂ ), more preferably not less than 0.07 (mol/kg-SiO ₂ ). If it is this amount, it is effective to stabilize the polishing energy rate when the slurry is recycled. Further, the amount of the colloidal cerium oxide in the polishing composition per 1 kg of the weak acid salt of the alkali metal (mol/kg-SiO ₂ ) is preferably not more than 2.0 (mol/kg-SiO ₂ ), more preferably not more than 1.0 (mol/ Kg-SiO ₂ ) is more preferably not more than 0.4 (mol/kg-SiO ₂ ). If it is this amount, it is effective with respect to the dispersion stability of cerium oxide.

Further, the molar concentration (b) (mol/kg-slurry) of the weak acid salt of the alkali metal contained per 1 kg of the polishing composition is preferably not less than 0.0001 (mol/kg-slurry), more preferably not less than 0.002 (mol/ Kg-slurry), more preferably not less than 0.003 (mol/kg-slurry). If it is this amount, it is effective for the stability of the polishing energy rate in grinding. Further, the molar concentration (b) (mol/kg-slurry) of the weak acid salt of the alkali metal contained per 1 kg of the polishing composition is preferably not more than 1.0 (mol/kg-slurry), more preferably not more than 0.1 (mol/ Kg-slurry), more preferably no more than 0.02 (mol/kg-slurry). If it is this amount, it is effective with respect to the dispersion stability of cerium oxide.

Herein, the content (X) of the weak acid salt can be obtained by dividing the molar concentration (b) of the weak acid salt of the alkali metal contained in the polishing composition by 1 kg per kg of the colloidal composition contained in the polishing composition. The total surface area (a) of cerium oxide was calculated. That is, the content (X) of the weak acid salt indicates the content (mol) of the weak acid salt relative to the total surface area (m ^{2 -} SiO ₂ ) of the colloidal cerium oxide. In the present invention, the content (X) of the weak acid salt is 1.0 × 10 ^-7 to 1.0 × 10 ^-5 mol / m ^{2 -} SiO ₂ . On the other hand, when the content (X) of the weak acid salt is less than 1.0 × 10 ^-7 , the optimum level of the ammonium compound of the fourth grade becomes small, and the pH of the polishing composition is lowered, so that the problem of insufficiently obtaining the polishing energy is caused. On the other hand, when it exceeds 1.0 × 10 ^-5 , the content of the optimum quaternary ammonium compound becomes large, and the pH of the polishing composition becomes high, so that dissolution or aggregation of cerium oxide occurs, and the content of the weak acid salt (X) When it is less than 1.0 × 10 ^-7 , the problem that the polishing energy rate cannot be sufficiently obtained is also generated.

According to this, when the weak acid salt content (X) contained in the polishing composition of the present invention is 1.0 × 10 ^-7 to 1.0 × 10 ^-5 mol / m ^{2 -} SiO ₂ , the desired effect of the present invention can be exerted. . It is preferably 1.0 × 10 ^-7 to 1.0 × 10 ^-5 mol / m ² -SiO ₂ , more preferably 2.0 × 10 ^-7 to 2.0 × 10 ^-5 mol / m ^{2 -} SiO ₂ , more preferably 5.0 × 10 ^-7 ~ 5.0 × 10 ^-5 mol / m ^{2 -} SiO ₂ .

<4-level ammonium compound>

The polishing composition of the present invention contains a quaternary ammonium compound.

The quaternary ammonium compound has a function of chemically polishing the surface to be polished, and an effect of improving the storage stability of the polishing composition.

The fourth-order ammonium compound is exemplified by tetramethylammonium hydroxide, hydroxyethyltrimethylammonium hydroxide (commonly referred to as "choline"), tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide. Ammonium, tetraamyl ammonium hydroxide, tetrahexylammonium hydroxide, and the like.

The amount of the colloidal cerium oxide per 1 kg of the quaternary ammonium compound (mol/kg-SiO ₂ ) is preferably not less than 0.1 (mol/kg-SiO ₂ ), more preferably not less than 0.3 (mol/kg-SiO ₂ ), and preferably not Less than 0.5 (mol/kg-SiO ₂ ). If it is this amount, there exists the effect which improves the grinding-energy rate in the grinding|polishing, and the grinding-energy rate is stabilized. The amount of the colloidal cerium oxide per 1 kg of the quaternary ammonium compound (mol/kg-SiO ₂ ) is preferably not more than 5.0 (mol/kg-SiO ₂ ), more preferably not more than 2.5 (mol/kg-SiO ₂ ), and preferably not More than 1.2 (mol/kg-SiO ₂ ). If it is this amount, it is effective with respect to the dispersion stability of cerium oxide.

Further, the molar concentration (c) (mol/kg-slurry) of the quaternary ammonium compound contained per 1 kg of the polishing composition is preferably not less than 0.0005 (mol/kg-slurry), more preferably not less than 0.005 (mol/kg- The slurry) is preferably not less than 0.02 (mol/kg-slurry). If it is this amount, there exists the effect which improves the grinding-energy rate in the grinding|polishing, and the grinding-energy rate is stabilized. The molar concentration (c) (mol/kg-slurry) of the quaternary ammonium compound contained per 1 kg of the polishing composition is preferably not more than 2.5 (mol/kg-slurry), more preferably not more than 1.2 (mol/kg-slurry). It is better not more than 0.6 (mol/kg-slurry). If it is this amount, it is effective with respect to the dispersion stability of cerium oxide.

Herein, the content (Y) of the quaternary ammonium compound can be obtained by dividing the molar concentration (c) of the quaternary ammonium compound contained per 1 kg of the polishing composition by the colloidal dioxide per 1 kg of the polishing composition. Calculated by the total surface area (a) of bismuth. That is, the content (Y) of the 4-grade ammonium compound means the content (mol) of the tertiary ammonium compound relative to the total surface area (m ^{2 -} SiO ₂ ) of the colloidal cerium oxide.

On the other hand, the optimum concentration (optimum value) (Y ₀ ) of the 4-grade ammonium compound can be calculated as follows according to the mechanism described at the outset.

The optimum value of Y: Y ₀ = A * X + B

A: theoretical buffer ratio of grade 4 ammonium compound to weak acid salt

B: The ammonium compound of the fourth order is adsorbed by the colloidal cerium oxide, and is not freed from the amount of the polishing composition (in other words, the amount of the ammonium quaternary compound adsorbed to the colloidal cerium oxide)

Further, by calculating (YY ₀ )/Y ₀ (%), it is possible to indicate how much the optimum concentration of the concentration of the quaternary ammonium compound contained in the polishing composition is deviated. In other words, if it is limited to -20 to 100%, the buffering effect can be efficiently performed, and the polishing composition is excellent in both "initial polishing energy rate" and "polishing energy rate retention rate".

The lower limit of the (YY ₀ )/Y ₀ (%) is preferably -10%, more preferably -8%, still more preferably -5%. Moreover, the upper limit of (YY ₀ )/Y ₀ (%) is preferably +80%, more preferably +50%, more preferably +20%, still more preferably +10%, and most preferably +5% .

In a preferred range, since a more desirable buffering action can be exerted, a sufficient polishing speed can be achieved, and in particular, an initial polishing energy rate can be improved. Further, according to the polishing composition of the present invention, it is possible to provide a composition for a stable polishing which is excellent in performance change even when it is repeatedly used, and particularly excellent in polishing rate retention.

From the above, the content (Y) of the quaternary ammonium compound can be set such that (YY ₀ )/Y ₀ (%) is limited to -20 to 100%, and the content of the weak acid salt (X) can be set. .

Next, the components contained in the polishing composition of the present invention will be described below.

<Nitrogen-containing water soluble polymer>

The polishing composition of the present invention may further contain a nitrogen-containing water-soluble polymer. By containing the nitrogen-containing water-soluble polymer, the flatness from the center to the end of the semiconductor wafer can be maintained.

The nitrogen-containing water-soluble polymer to be used preferably has one or more nitrogen atoms in the monomer unit, or one or more nitrogen atoms in one of the side chains, and for example, an amine, an imine or a guanamine may be used. The quinone imine, the carbodiimide, the hydrazide, the urethane compound, or the like may be in the form of a chain, a ring, a first, a second, or a third.

Further, it may be a nitrogen-containing water-soluble polymer having a structure in which a salt formed of a nitrogen atom is used as a cation. The nitrogen-containing water-soluble polymer having a salt structure is exemplified by, for example, a quaternary ammonium salt. Other nitrogen-containing water-soluble polymers are exemplified by polycondensation polyamines such as water-soluble nylon, polycondensation polyesters such as water-soluble polyesters, polyaddition polyamines, polyaddition polyimines, and polyadditions. A (meth)acrylamide, a water-soluble polymer having at least a part of an alkyl main chain and a water-soluble polymer having a nitrogen atom in at least a part of a side chain, and the like. Further, the water-soluble polymer having a nitrogen atom in the side chain also contains a water-soluble polymer having a quaternary nitrogen in a side chain.

Specific examples of the polyaddition-based nitrogen-containing water-soluble polymer include polyvinylimidazole, polyvinylcarbazole, polyvinylpyrrolidone, polyvinyl caprolactam, polyvinylpiperidine, and the like. And, nitrogen-containing water-soluble high score The sub-structure may have a hydrophilic structure partially having a vinyl alcohol structure, a methacrylic acid structure, a vinyl sulfonic acid structure, a vinyl alcohol carboxylate structure, or an oxyalkylene structure. Further, it may be a diblock type or a triblock type, a random type, or an interactive type of polymer having a plurality of configurations. The nitrogen-containing water-soluble polymer may be any one of a molecule having a part or all of a cation, an anion, an anion and a cation, and a nonionic group. These nitrogen-containing water-soluble polymers may be used alone or in combination of two or more.

Among the nitrogen-containing water-soluble polymers, from the viewpoint of satisfactorily functioning to control the workability of the end portion, it is preferably polyvinylpyrrolidone, a part of the structure comprising a copolymer of polyvinylpyrrolidone, and a polyvinyl group. The mesaconamine, a part of the structure, comprises a copolymer of polyvinyl caprolactam. Among these nitrogen-containing water-soluble polymers, polyvinylpyrrolidone is preferred.

The weight average molecular weight of the nitrogen-containing water-soluble polymer in the polishing composition is preferably less than 1.500000 in terms of polyethylene oxide, preferably less than 500,000, more preferably less than 100,000, and even less preferably less than 80,000. It is best not to reach 50,000. When the weight molecular weight of the nitrogen-containing water-soluble polymer is less than 1,500,000, it is easy to maintain the storage stability of the polishing composition.

Further, the weight average molecular weight of the nitrogen-containing water-soluble polymer in the polishing composition is preferably not less than 1,000, more preferably not less than 20,000. When the molecular weight of the nitrogen-containing water-soluble polymer is not less than 1,000, it is easier to maintain the shape of the end portion of the semiconductor wafer.

The content of the nitrogen-containing water-soluble polymer compound in the polishing composition is preferably not less than 0.0001% by mass. Nitrogen-containing water soluble polymer When the content of the substance is not less than 0.0001% by mass, it is easier to maintain the shape of the end portion of the semiconductor wafer.

Further, the content of the nitrogen-containing water-soluble polymer in the polishing composition is preferably less than 0.002% by mass, more preferably less than 0.001% by mass, even more preferably less than 0.0005% by mass. When the content of the nitrogen-containing water-soluble polymer is less than 0.002% by mass, it is easier to obtain a high polishing rate.

<chelating agent>

The polishing composition of the present invention may contain a chelating agent. The chelating agent in the polishing composition serves to capture metal impurities in the polishing system to form a complex, and to suppress the residual of the metal impurities on the semiconductor wafer.

The chelating agent is exemplified by, for example, an aminocarboxylic acid-based chelating agent and an organic phosphonic acid-based chelating agent. Specific examples of the aminocarboxylic acid-based chelating agent include ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetate, nitrilo triacetic acid, sodium nitrilotriacetate, ammonium nitrilotriacetate, and hydroxyethylethylene glycol. Amine triacetic acid, sodium hydroxyethyl ethylenediamine triacetate, diethylidene triamine pentaacetic acid, sodium diethyltriamine pentaacetate, triethylammonium hexaacetate, triethylammonium hexaacetate Sodium and so on.

Specific examples of the organic phosphonic acid-based chelating agent are 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotris(ethylphosphonic acid), and ethylenediamine oxime. (methylene phosphonic acid), di-extension ethyltriamine penta (methylene phosphonic acid), tri-extension ethyltetramine hexa (methylene phosphonic acid), ethane-1,1-diphosphonic acid, B Alkane-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, methane hydroxyphosphine Acid, 2-phosphonium butane-1,2-dicarboxylic acid, 1-phosphonium butane-2,3,4-tricarboxylic acid, α-methylphosphonium succinic acid and the like. These chelating agents may be used alone or in combination of two or more.

The organic phosphonic acid-based chelating agent is preferably used in the chelating agent, more preferably ethylenediamine oxime (methylene phosphonic acid).

The content of the chelating agent in the polishing composition is preferably not less than 0.0001% by mass, more preferably not less than 0.0005% by mass. As the content of the chelating agent is increased, the effect of suppressing residual metal impurities of the semiconductor wafer is enhanced.

Further, the content of the chelating agent in the polishing composition is preferably less than 0.01% by mass, more preferably less than 0.005% by mass. As the content of the chelating agent is reduced, the preservation stability of the polishing composition can be further ensured.

<water>

The polishing composition of the present invention preferably contains water.

The water in the polishing composition has a function of dissolving or dispersing other components. In order to avoid obstructing the action of other components as much as possible, it is preferred to use water in which the total content of the transition metal ions is not more than 100 ppb. For example, ion exchange resin can be used to remove impurity ions, filter to remove foreign matter, and distillation to increase the purity of water. Specifically, for example, ion-exchanged water, pure water, ultrapure water, distilled water or the like is preferably used.

The pH of the polishing composition is preferably in the range of 8 to 12, more preferably in the range of 9 to 11.

The above-mentioned polishing composition can be prepared by, for example, wing stirring Mixing and mixing devices such as a mixer, an ultrasonic disperser, and a homogenizer. The raw materials of the polishing composition may be simultaneously mixed, and the mixing order may be appropriately set.

Next, the polishing method of the semiconductor wafer using the polishing composition of the present invention will be described together with the action of the polishing composition. That is, a method of manufacturing a semiconductor wafer including a polishing step of polishing a semiconductor wafer using a polishing composition will be described.

When the surface of the semiconductor wafer is polished using the polishing composition, the polishing composition is applied to the surface of the semiconductor wafer while the polishing pad is pressed against the surface of the semiconductor wafer to rotate the semiconductor wafer and the polishing pad. The polishing apparatus uses, for example, a double-sided polishing apparatus that simultaneously polish both sides of a semiconductor wafer. In particular, in the pre-polishing, a double-sided polishing apparatus is preferably used from the viewpoint of improving flatness.

Further, in the present invention, the composition of the polishing is prepared by taking into account the presence of the colloidal cerium oxide adsorbed in the composition for polishing and the hydroxide of the water-soluble quaternary ammonium which is not liberated in the polishing composition. Since the idea of the object, the single-side and double-side polishing can improve the initial polishing energy rate, and the effect is low even if the repeated use performance is changed, and in particular, the polishing rate is excellent. Therefore, the single-side polishing or the double-side polishing may be performed in accordance with the actual situation.

The polishing step of grinding the two sides or one side of the semiconductor wafer has a plurality of stages including a first polishing step including an initial polishing step, a second polishing step performed after the polishing step, and a final polishing step performed as a final modification. In the grinding step, after the second grinding step In the polishing step, single-side polishing of one side of the semiconductor wafer is performed.

The polishing composition of the present invention is a polishing composition for use in polishing a semiconductor wafer comprising a colloidal cerium oxide, a weak acid salt, and a quaternary ammonium compound, and the content of the weak acid salt is relative to the colloidal The total surface area of cerium oxide is 1.0 × 10 ^-7 to 1.0 × 10 ^-5 mol / m ^{2 -} SiO ₂ , and the content of the quaternary ammonium compound satisfies the polishing composition of the following formulas (1) and (2).

[Number 3] Y ₀ = A * X + B (1) -20 ≦ (YY ₀ ) / Y ₀ ≦ 100 (%) (2)

A: theoretical buffer ratio of grade 4 ammonium compound to weak acid salt

B: the amount of the ammonium compound of 4 is adsorbed by the colloidal cerium oxide, and is not released in the composition for polishing.

Y: content of grade 4 ammonium compound

Y ₀ : optimum amount of grade 4 ammonium compound

X: content of weak acid salt.

By having such a configuration, the polishing composition of the present invention can achieve a sufficient polishing rate, and even if it is repeatedly used, the performance change is low and stable. This is generally required by the first grinding step and the second grinding step described above, and is in turn the required performance that is primarily required in the first grinding step. Therefore, the present invention is preferably used for a first polishing step or a second polishing step of a semiconductor wafer, and is preferably a first polishing step of the semiconductor wafer, and more preferably The semiconductor wafer is subjected to two-side polishing by a silicon wafer having a first polishing step of a size of not less than 300 mm. The reason for this is that in the order of the second polishing step, the single polishing of the first polishing step, and the polishing of both surfaces of the first polishing step, the required polishing rate becomes high, and the amount of enthalpy removed by one polishing increases. At this time, the amount of ruthenium dissolved in the polishing composition is increased, and the ruthenium ion is contained in the polishing composition. At this time, it acts in a direction in which the pH of the polishing composition is lowered. In the present invention, even in this case, the pH fluctuation at the time of recycling of the polishing composition can be suppressed.

Further, the polishing composition of the present invention can maximize the buffering effect by taking into account the fourth-order ammonium adsorbed by the colloidal cerium oxide which has not been noticed in the past. Thereby, a sufficient polishing speed can be achieved, and in particular, the initial polishing energy rate can be improved, and even if it is repeatedly used, the performance change is small, and in particular, the polishing energy rate retention rate is excellent, thereby contributing to high flatness or low defect performance of the wafer. Therefore, the surface of the semiconductor wafer can be stably ground and polished, so that the performance of the semiconductor wafer is stabilized, and the user who uses the polishing composition is also very reliable. Further, since the polishing composition of the present invention has a stable pH, it is also very suitable for long-term storage.

Embodiments of the present invention can also be modified as follows.

‧ The polishing composition may contain a conventional additive such as a preservative or an antifungal agent as needed. Specific examples of the preservative and the antifungal agent include an isothiazoline compound, a paraben, a phenoxyethanol, and the like.

‧ The polishing composition may be a single dosage form or a multiple dosage form consisting of two or more doses.

‧ The polishing composition can also be prepared by diluting a stock solution of the polishing composition with water. For example, after the stock solution of the polishing composition is stored or transported, it is diluted at the time of use to prepare a polishing composition.

‧ The polishing composition can also be used in a single polishing process for re-polishing. When the used polishing composition is used for the regrind, an insufficient component may be added to the polishing composition.

‧ The polishing pad used for polishing the polishing composition is not particularly limited, and any of polyurethane, non-woven fabric, suede, abrasive-containing particles, and abrasive-free particles can be used.

[Examples]

Next, the above embodiments will be more specifically described by way of examples and comparative examples. However, it is needless to say that the present invention is not limited to the following embodiments.

The colloidal cerium oxide (SiO ₂ ) (true specific gravity: 2.1 to 2.2), the weak acid salt of an alkali metal, and the tertiary ammonium compound are added to the ion-exchanged water, and stirred and mixed at room temperature for about 30 minutes at about 25 ° C for about 30 minutes. Example ‧ The polishing composition (2 kg) of the comparative example. The details of the polishing compositions of the respective examples are shown in Table 1. Further, Comparative Example 1 and Comparative Example 2 correspond to the experimental number 1 and the experimental number 2 of the first embodiment disclosed in Patent Document 3, respectively.

Further, the colloidal cerium oxide is produced by a water exchange method using water glass (Na citrate) as a raw material.

The "BET particle diameter (nm)" in Table 1 indicates the average primary particle diameter calculated from "BET specific surface area (m ² /g-SiO ₂ )" measured by "Flow Sorb II 2300" manufactured by Micromeritics Co., Ltd. Specifically, the colloidal cerium oxide of the polishing composition of Comparative Example 1 and Comparative Example 2 has a BET particle diameter of 15.0 nm, and the colloidal cerium oxide of the polishing compositions of Examples 1 to 6 and Comparative Examples 3 to 5 It has a BET particle size of 55.0 nm.

Further, the pHs of Examples 1 to 6 and Comparative Examples 1 to 5 were 10.32, 10.35, 10.30, 10.34, 10.33, 10.36, 9.82, 9.88, 10.04, 10.15, and 10.28, respectively. Further, the pH was measured at room temperature of 25 ° C using a model F-23 manufactured by Horiba, Ltd.

Further, the "concentration (wt%)" in the column of "SiO ₂ " in Table 1 indicates the concentration (% by weight) of colloidal cerium oxide in the polishing composition. Specifically, the polishing composition of each example also prepared the concentration of colloidal cerium oxide to 5% by weight.

Further, in the column of "SiO ₂ " in Table 1, "the surface area (a) (m ^{2 -} SiO ₂ / kg - slurry) per 1 kg of the cerium oxide of the slurry" means the colloid 2 contained per 1 kg of the polishing composition. Total surface area of cerium oxide (a).

The category "K ₂ CO ₃ " in the column of "content of weak alkali acid salt of alkali metal" in Table 1 represents potassium carbonate, and "KHCO ₃ " represents potassium hydrogencarbonate.

Further, in the column of "content of II acid weak acid salt of alkali metal" in Table 1, "molar concentration of molahydrate (mol/kg-SiO ₂ ) of divalent acid salt per 1 kg of alkali metal of cerium oxide" means colloid The amount of weak acid salt of cerium oxide per 1 kg of alkali metal (mole).

Further, in the column of "the content of the II acid weak acid salt of the alkali metal" in Table 1, the "molar concentration of the II-acid weak acid salt per mol of the alkali metal of the slurry (mol/kg-slurry)" means the composition for polishing. The molar concentration of the weak acid salt of the alkali metal contained in 1 kg (b).

Further, "X (= (b) / (a)) (mol / m ^{2 -} SiO ₂ )" in the column of "content of II acid weak acid salt of alkali metal" in Table 1 is by (b) Calculated by dividing by (a). That is, it indicates the content (mol) of the weak acid salt of the alkali metal relative to the total surface area (m ² ) of the colloidal cerium oxide. Also, "E" in the table indicates the index, and "E-06" means "10 ^-6 ". The same as below.

The category "TMAOH" in the column of "Content of 4-grade ammonium compound" in Table 1 means tetramethylammonium hydroxide.

Further, in the column of "the content of the ammonium compound of the fourth order" in Table 1, "the molar concentration of the quaternary ammonium salt per mol of the ammonium salt (mol/kg-SiO ₂ )" indicates that the colloidal cerium oxide is level 4 per kg. The amount of ammonium compound (mole).

Further, in the column of "the content of the ammonium compound of the fourth order" in Table 1, "the molar concentration (c) (mol/kg-slurry) of the ammonium salt per gram of the slurry of 1 kg" means that the composition for polishing is contained per 1 kg. Molar concentration of the 4-grade ammonium compound (c).

Further, "Y (= (c) / (a)) (mol / m ^{2 -} SiO ₂ )" in the column of "content of the ammonium compound of the fourth order" in Table 1 is obtained by dividing (c) by (a) The value, that is, the content (mole) of the total surface area (m ² ) of the quaternary ammonium compound relative to the colloidal cerium oxide.

"Y ₀ (mol/m ^{2 -} SiO ₂ )" in the column "Optimum value of Y" in Table 1 represents the optimum concentration of TMAOH. More specifically, it is calculated by the following formula.

The optimum value of TMAOH: Y ₀ = A * X + B

A: Theoretical buffer ratio of TMAOH to weak acid salt (=2)

B: TMAOH is adsorbed by colloidal cerium oxide, and is not free from the amount of the polishing composition (=8.0×10 ^-6 mol/m ² -SiO ₂ )

In addition, "B" is a value calculated by dividing "the amount of adsorption of the fourth-order ammonium compound measured by TOC on the abrasive grains" by the "specific surface area of the cerium oxide abrasive grains measured by the BET measurement method", and water glass (矽) The acid Na) raw material cerium oxide is a fixed value. More specifically, the polishing composition is subjected to centrifugation, and the organic substance (i.e., carbon) of the supernatant liquid is measured. That is, since the amount of organic carbon measured by TOC is quantitative, it can be measured by how much the ammonium compound is reduced by the amount of the ammonium compound fed.

"(YY ₀ )/Y ₀ (%)" in the column of "Difference from the optimum value of Y" in Table 1 indicates how much the optimum concentration of the concentration of the quaternary ammonium compound contained in the polishing composition is deviated. If it is limited to -20 to 100%, it will be described as a polishing composition which is excellent in both "initial polishing energy rate" and "polishing energy rate retention rate".

Then, 600 ml of the polishing composition of each example was recycled, and EJ-380IN manufactured by ENGIS, Inc., using a small-sized grinding machine, was used to carry out the polishing process of the silicon wafer under the polishing conditions described in Table 2. In addition, the germanium wafer is 60mm × 60mm, the conductive type is P type, the crystal orientation is <100>, and the resistivity is not less than 0.1Ω. Cm and less than 1000Ω. Cm. The polishing performance was evaluated by "initial polishing rate" and "grinding rate retention rate".

<Grinding energy rate (μm/min) at the time of cumulative removal grinding>

In Table 1, the "grinding energy rate (μm/min) in the case of cumulative removal grinding" The "10 μm" column means the average polishing energy rate at the time of polishing 10 μm from the start of polishing, that is, how much is polished per minute (grinding energy rate) from the start of polishing to the polishing of 10 μm. Similarly, the "20 μm" column indicates how much grinding per minute (grinding energy rate) in the interval of cumulative removal of 10 to 20 μm. The columns "30 μm", "40 μm", and "50 μm" are also the same.

<Initial Grinding Energy Rate>

The "initial polishing energy rate" in Table 1 means the polishing energy rate of the cumulative removal amount of 10 μm, that is, the same as the "10 μm" column, the higher the polishing energy rate, the better, and the "0" is performed on the basis shown in Table 1. The 6-stage evaluation of "5".

<grinding rate maintenance rate>

The "grinding rate maintenance rate" in Table 1 is a percentage indicating the difference between the cumulative removal amount of 50 μm ("50 μm" column) and the cumulative removal amount of 10 μm ("10 μm" column) based on the initial polishing energy rate. The larger the value, the better, and the six-stage evaluation of "0" to "5" is performed on the basis shown in the table below.

In the recycling of the polishing composition (slurry), both the initial polishing energy rate and the maintenance property (the polishing energy retention rate) are both obtained as characteristics. Therefore, the comprehensive evaluation is based on the "initial polishing energy rate" and the "grinding energy rate". The average of the maintenance rate was evaluated.

[Table 2]

[grinding conditions]

Grinder: ENGIS EJ-380IN

Grinding pressure: 51.6kPa

Platen speed: 50rpm

Carrier disk revolutions: 50rpm

Abrasive cloth: MH S-15A

Grinding composition flow rate: 100ml/min

Naked 矽P-<100>60mm×60mm

Grinding environment temperature: 25 ° C

In addition, the present application is based on Japanese Patent Application No. 2014-000554, filed on Jan.

Claims (5)

A polishing composition comprising colloidal cerium oxide, a weak acid salt, and a quaternary ammonium compound, which is a polishing composition used for polishing a semiconductor wafer, and the content of the aforementioned weak acid salt is relative to colloidal oxidation The total surface area of the crucible is 1.0×10 ^-7 to 1.0×10 ⁻⁵ mol/m ² —SiO ₂ , and the content of the 4-grade ammonium compound satisfies the relationship of the following formulas (1) and (2), [1] Y ₀ =A * X+B (1) -20≦(YY ₀ )/Y ₀ ≦100(%) (2) A: Theoretical buffer ratio of grade 4 ammonium compound to weak acid salt B: grade 4 ammonium compound is colloidal II The amount of yttrium oxide adsorbed and not free in the polishing composition Y: the content of the 4-grade ammonium compound Y ₀ : the optimum amount of the 4-grade ammonium compound X: the content of the weak acid salt. The polishing composition of claim 1, wherein the weak acid salt is a divalent weak acid salt. The polishing composition of claim 1 or 2, wherein the aforementioned weak acid salt is a carbonate or a dicarboxylic acid salt. The polishing composition according to any one of claims 1 to 3, wherein the fourth ammonium compound is selected from the group consisting of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide. Ammonium, tetraammonium hydroxide And a group consisting of tetrahexylammonium hydroxide. A method of manufacturing a semiconductor wafer, comprising the step of polishing a semiconductor wafer using the polishing composition according to any one of claims 1 to 4.