JP7128005B2 - Polishing composition - Google Patents

Description

The present invention relates to polishing compositions.

2. Description of the Related Art In recent years, electronic devices such as computers have achieved high performance such as miniaturization, multifunctionality, and high speed due to high integration brought about by miniaturization of LSI manufacturing processes. A chemical mechanical polishing (CMP) method is used in a new microfabrication technique that accompanies such high integration of LSI. The CMP method is a technique frequently used in the LSI manufacturing process, especially in the planarization of an interlayer insulating film, the formation of a metal plug, and the formation of a buried wiring (damascene wiring) in a multilayer wiring formation process.

In recent years, CMP has been applied to each process in semiconductor manufacturing, and one aspect thereof is application to a gate forming process in manufacturing a transistor, for example.

Si-containing materials such as polycrystalline silicon (polysilicon), silicon oxide, and silicon nitride are sometimes polished during transistor fabrication, and it is required to control the polishing rate of each Si-containing material. For example, in Patent Document 1, a polishing composition capable of rapidly polishing a layer containing a silicon-based material other than polysilicon and selectively suppressing the polishing speed of a layer containing polysilicon has a negative zeta A polishing composition has been proposed which contains colloidal silica particles having an electric potential, phosphoric acid or a specific organic phosphonic acid compound, and a specific anionic surfactant.

JP 2011-216581 A

However, it was found that the selectivity of silicon nitride to polysilicon is not sufficient even with the composition described in Patent Document 1 above. It has also been found difficult to increase the selectivity of silicon nitride to silicon oxide.

Accordingly, the present invention has been made in view of the above circumstances, and provides a polishing composition capable of polishing an object to be polished containing silicon nitride with high selectivity to silicon oxide or polysilicon. With the goal.

The present inventors have conducted intensive research in order to solve the above problems. As a result, the inventors have found that the above problems can be solved by using a predetermined additive, and have completed the present invention.

That is, the above object is an abrasive grain,
at least one compound selected from the group consisting of compounds represented by the following formula (1) and salts thereof;
is achieved by a polishing composition comprising

(In formula (1), R ¹ is a substituted or unsubstituted hydrocarbon group having 6 to 30 carbon atoms, and R ² is a hydrogen atom or a substituted or unsubstituted carbon atom having 1 to 30 carbon atoms. is a hydrogen group, X is a single bond or —CO—, and Y is a divalent hydrocarbon group having 1 to 30 carbon atoms which may have a substituent.)

By using the polishing composition of the present invention, an object to be polished containing silicon nitride can be polished with high selectivity to silicon oxide or polysilicon.

The polishing composition of the present invention comprises abrasive grains,
at least one compound selected from the group consisting of compounds represented by the following formula (1) and salts thereof;
including.

(In formula (1), R ¹ is a substituted or unsubstituted hydrocarbon group having 6 to 30 carbon atoms, and R ² is a hydrogen atom or a substituted or unsubstituted carbon atom having 1 to 30 carbon atoms. is a hydrogen group, X is a single bond or —CO—, and Y is a divalent hydrocarbon group having 1 to 30 carbon atoms which may have a substituent.)
According to the polishing composition having the above structure, an object to be polished containing silicon nitride can be polished with high selectivity to silicon oxide or polysilicon.

Semiconductor wafers are composed of dissimilar materials such as, for example, polycrystalline silicon to form circuits, silicon oxide which is an insulating material, and silicon nitride to protect silicon dioxide surfaces which are not part of trenches or vias from damage during etching. be. In such patterned wafers, since the action of the polishing composition on each material is different, it is difficult to form a completely flat surface, and it is required to minimize steps between different materials.

One of the causes of the unevenness is that a material such as polycrystalline silicon or silicon oxide, which is relatively soft and readily reacts with an abrasive, is excessively shaved compared to the surrounding silicon nitride or the like.

The polishing composition described in Patent Document 1 contains phosphoric acid or a specific organic phosphonic acid compound in addition to abrasive grains. The phosphoric acid or certain organic phosphonic acid compounds can act as accelerators for silicon nitride to improve the polishing rate of silicon nitride.

However, according to the studies of the present inventors, even with the polishing composition of Patent Document 1, it is difficult to sufficiently increase the selectivity of silicon nitride to silicon oxide or polysilicon, and the polishing composition is composed of dissimilar materials. The current demand for planarization in patterned wafer polishing cannot be achieved satisfactorily. Further improvements are therefore required.

In contrast, the present invention is characterized by the use of a given compound having a long-chain hydrocarbon group ^R1 and a carboxyl group (carboxylate) or a salt thereof as an additive. According to this configuration, the polishing rate of the layer containing silicon oxide or polysilicon (the polishing object having the layer containing silicon oxide or polysilicon) can be suppressed, so that the layer containing silicon nitride can be polished at a relatively high rate. can be polished with Although the detailed mechanism that produces the above effect is unknown, it is considered as follows. Note that the following mechanism is speculation and does not limit the technical scope of the present invention. In chemical-mechanical polishing (CMP) of layers containing silicon oxide or polysilicon, the use of certain compounds or salts thereof having a long-chain hydrocarbon group ^R1 and a carboxyl group (carboxylate) as an additive reduces oxidation It was considered effective for suppressing the polishing rate of layers containing silicon and polysilicon. In detail, the carboxyl group (carboxylate) side of the additive has a high chemical or physical adsorption force to the surface of the layer containing silicon oxide and polysilicon of the polishing object, so the carboxyl group (carboxylate) is It is possible to form a strong protective film on the surface of the layer containing silicon oxide and polysilicon via. Furthermore, by having a long-chain hydrocarbon group as R ¹ , contact of abrasive grains in the polishing composition due to the steric hindrance effect of the long-chain hydrocarbon group can be suppressed. Additives are also adsorbed on the surfaces of the abrasive grains, and the additives having steric hindrance are adsorbed on both the abrasive grains and the silicon oxide or polysilicon. Contact can be further suppressed. It is believed that this suppresses polishing of the surface of the layer containing silicon oxide and polysilicon due to contact with abrasive grains.

Therefore, according to the polishing composition of the present invention, a layer containing silicon nitride can be polished at a high polishing rate while a layer containing silicon oxide and polysilicon can be polished at a low polishing rate.

Embodiments of the present invention will be described below. In addition, the present invention is not limited only to the following embodiments.

In this specification, "X to Y" indicating a range means "X or more and Y or less". In this specification, unless otherwise specified, operations and measurements of physical properties are performed under the conditions of room temperature (20 to 25° C.)/relative humidity of 40 to 50% RH.

[Object to be polished]
In the present invention, the object to be polished is not particularly limited, and includes a metal or a layer containing a metal, an object to be polished having oxygen atoms and silicon atoms, an object to be polished having silicon-silicon bonds, and an object to be polished having silicon-nitrogen bonds. etc.

Examples of metals include tungsten, copper, aluminum, cobalt, hafnium, nickel, gold, silver, platinum, palladium, rhodium, ruthenium, iridium, and osmium.

Polishing objects having oxygen atoms and silicon atoms include, for example, silicon oxide (SiO ₂ ), tetraethyl orthosilicate (TEOS), and the like.

Examples of objects to be polished having a silicon-silicon bond include polysilicon, amorphous silicon, single crystal silicon, n-type doped single crystal silicon, p-type doped single crystal silicon, and Si-based alloys such as SiGe.

Objects to be polished having silicon-nitrogen bonds include objects to be polished having silicon-nitrogen bonds such as silicon nitride films and SiCN (silicon carbonitride).

Since the polishing composition of the present invention has a high selectivity to materials having a silicon-nitrogen bond, particularly silicon nitride, the object to be polished may contain a material having a silicon-nitrogen bond, particularly silicon nitride. preferable.

In addition, the polishing composition of the present invention is preferably used for selectively polishing a material having a silicon-nitrogen bond in an object to be polished containing a material having a silicon-nitrogen bond and other materials containing silicon. can be In particular, it can be used to selectively polish silicon nitride with respect to polysilicon or silicon oxide.

Here, in the polishing composition according to one embodiment of the present invention, the lower limit of the ratio of the silicon nitride polishing rate (Å/min) to the silicon oxide polishing rate (Å/min) is preferably 28 or more, It is more preferably 30 or more. The upper limit of the ratio of the polishing rate (Å/min) of silicon nitride to the polishing rate (Å/min) of silicon oxide is preferably 100 or less, more preferably 85 or less.

The lower limit of the ratio of the polishing rate (Å/min) of silicon nitride to the polishing rate (Å/min) of polysilicon is preferably 7 or more, more preferably 10 or more, and 14 or more. is more preferred. The upper limit of the ratio of the polishing rate (Å/min) of silicon nitride to the polishing rate (Å/min) of silicon oxide is preferably 100 or less, more preferably 85 or less.

The object to be polished is preferably a substrate, more preferably a semiconductor substrate, and even more preferably a patterned wafer as a product form.

[Polishing composition]
The polishing composition of the present invention contains abrasive grains and predetermined additives. The constitution of the polishing composition of the present invention is described below.

(abrasive)
The polishing composition of the present invention essentially contains abrasive grains. The abrasive grains contained in the polishing composition have the effect of mechanically polishing the object to be polished, and improve the polishing rate of the object to be polished by the polishing composition.

The abrasive grains used may be inorganic particles, organic particles, or organic-inorganic composite particles. Specific examples of inorganic particles include particles of metal oxides such as silica, alumina, ceria, and titania, silicon nitride particles, silicon carbide particles, and boron nitride particles. Specific examples of organic particles include polymethyl methacrylate (PMMA) particles. The abrasive grains may be used alone or in combination of two or more. In addition, as the abrasive grains, commercially available products or synthetic products may be used.

Among these abrasive grains, silica is preferable from the viewpoint of excellent dispersion stability, easy availability, and cost. In addition, if the abrasive grains are silica, the additive of the above formula (1) is likely to be adsorbed on the surface of the abrasive grains. It is preferable because it can be further improved. Among them, colloidal silica is particularly preferred.

The abrasive grains may be surface-modified. Ordinary colloidal silica has a zeta potential value close to zero under acidic conditions, so silica particles do not electrically repel each other under acidic conditions and easily aggregate. In contrast, abrasive grains surface-modified to have a relatively large negative value of zeta potential even under acidic conditions strongly repel each other and are well dispersed even under acidic conditions. As a result, the storage stability of the polishing composition can be improved. Therefore, it is preferable to use abrasive grains surface-modified so that the zeta potential becomes a negative value at the pH of the polishing composition, especially under acidic conditions. Such surface-modified abrasive grains can be obtained, for example, by mixing metals such as aluminum, titanium or zirconium or oxides thereof with abrasive grains to dope the surfaces of the abrasive grains.

Among these, silica having an organic acid immobilized on its surface (also referred to as organically modified silica or organic acid-immobilized silica) is particularly preferred.

Silica having an organic acid immobilized on its surface includes fumed silica and colloidal silica, and colloidal silica is particularly preferred. The organic acid is not particularly limited, but includes sulfonic acid, carboxylic acid, phosphoric acid and the like, preferably sulfonic acid or carboxylic acid. In addition, on the surface of the silica having the organic acid contained in the polishing composition of the present invention fixed to the surface, acidic groups derived from the organic acid (for example, sulfo group, carboxyl group, phosphoric acid group, etc.) are present (in some cases (sometimes via a linker structure).

The method of introducing these organic acids onto the silica surface is not particularly limited. For example, in addition to the method of introducing onto the silica surface in the form of a mercapto group or an alkyl group and then oxidizing them into sulfonic acid or carboxylic acid, and a method in which a protecting group is bonded to the acidic group derived from the above organic acid and then introduced onto the silica surface, and then the protecting group is removed. In addition, the compound used for introducing the organic acid to the silica surface is not particularly limited, but has at least one functional group that can be an organic acid group, and further has a functional group that can be used for bonding with the hydroxyl group on the silica surface. groups, functional groups introduced to control hydrophobicity/hydrophilicity, functional groups introduced to control steric bulkiness, and the like.

As a specific synthesis method of silica having an organic acid immobilized on its surface, if sulfonic acid, which is a kind of organic acid, is immobilized on the surface of silica, for example, "Sulfonic acid-functionalized silica through quantitative oxidation of thiolgroups", Chem. Commun. 246-247 (2003). Specifically, sulfonic acid is immobilized on the surface by coupling a silane coupling agent having a thiol group such as 3-mercaptopropyltrimethoxysilane to silica and then oxidizing the thiol group with hydrogen peroxide. silica can be obtained. Alternatively, if the carboxylic acid is fixed to the surface of silica, for example, "Novel Silane Coupling Agents Containing a Photolabile 2-Nitrobenzyl Ester for Introduction of a Carboxy Group on the Surface of Silica Gel", Chemistry Letters, 3, 228- 229 (2000). Specifically, silica having a carboxylic acid immobilized on its surface can be obtained by coupling a silane coupling agent containing a photoreactive 2-nitrobenzyl ester to silica and then irradiating with light.

The average degree of association of abrasive grains is also, for example, less than 5.0, more preferably 3.0 or less, still more preferably 2.5 or less. As the average association degree of abrasive grains becomes smaller, the surface roughness caused by the shape of abrasive grains can be improved. The average association degree of abrasive grains is also preferably 1.0 or more, more preferably 1.05 or more. The average association degree is obtained by dividing the average secondary particle size of abrasive grains by the average primary particle size. As the average association degree of abrasive grains increases, there is an advantageous effect of improving the polishing rate of the object to be polished by the polishing composition.

The lower limit of the average primary particle size of the abrasive grains is preferably 5 nm or more, more preferably 10 nm or more. Also, the upper limit of the average primary particle size of the abrasive grains is preferably 200 nm or less, more preferably 150 nm or less, and even more preferably 100 nm or less. Within such a range, the polishing rate of the object to be polished by the polishing composition is improved, and the occurrence of surface defects on the surface of the object to be polished after polishing with the polishing composition is further suppressed. be able to. The average primary particle size of the abrasive grains is calculated based on the specific surface area of the abrasive grains measured by the BET method, for example.

The lower limit of the average secondary particle size of the abrasive grains is preferably 15 nm or more, more preferably 20 nm or more, and even more preferably 30 nm or more. The upper limit of the average secondary particle size of the abrasive grains is preferably 300 nm or less, more preferably 260 nm or less, and even more preferably 220 nm or less. Within such a range, the polishing rate of the object to be polished by the polishing composition is improved, and the occurrence of surface defects on the surface of the object to be polished after polishing with the polishing composition is further suppressed. be able to. The secondary particles here refer to particles formed by association of abrasive grains in the polishing composition, and the average secondary particle diameter of the secondary particles is measured, for example, by a dynamic light scattering method. be able to.

The upper limit of the aspect ratio of the abrasive grains in the polishing composition is, for example, less than 2.0, preferably 1.8 or less, more preferably 1.5 or less. Within such a range, the surface roughness caused by the shape of the abrasive grains can be improved. In addition, the aspect ratio is a value obtained by taking the smallest rectangle circumscribing the image of the abrasive grain with a scanning electron microscope and dividing the length of the long side of the rectangle by the length of the short side of the same rectangle. , and can be determined using common image analysis software. The lower limit of the aspect ratio of the abrasive grains in the polishing composition is 1.0 or more. The closer to this value, the better the surface roughness caused by the shape of the abrasive grains.

In the abrasive grains in the polishing composition, the particle diameter (D90) and the total particle weight of all particles when the cumulative particle weight from the fine particle side reaches 90% of the total particle weight in the particle size distribution determined by the laser diffraction scattering method The lower limit of D90/D10, which is the ratio of the particle diameter (D10) when reaching 10%, is, for example, 1.1 or more, preferably 1.2 or more, and 1.3 or more is more preferred. In addition, in the abrasive grains in the polishing composition, in the particle size distribution determined by the laser diffraction scattering method, the particle diameter (D90) and the total weight of all particles when the accumulated particle weight from the fine particle side reaches 90% of the total particle weight Although the upper limit of the ratio D90/D10 to the particle diameter (D10) when reaching 10% of the particle weight is not particularly limited, it is preferably 2.04 or less. Within such a range, the surface roughness caused by the shape of the abrasive grains can be improved.

The lower limit of the content of abrasive grains in the polishing composition is preferably 0.0005% by mass or more, more preferably 0.001% by mass or more, still more preferably 0.005% by mass or more, and even more preferably 0.005% by mass or more. It is preferably 0.01% by mass or more, and particularly preferably 0.1% by mass or more. As the content of abrasive grains increases, the polishing rate of the object to be polished with the polishing composition is further improved. The content of abrasive grains in the polishing composition is preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 1% by mass or less, and even more preferably 0.5% by mass. % by mass or less, and particularly preferably 0.3% by mass or less. Within such a range, silicon nitride can be polished more selectively. Moreover, it is preferable because erosion to the stopper film can be suppressed. Furthermore, the cost of the polishing composition can be suppressed, and the occurrence of surface defects on the surface of the object to be polished after polishing with the polishing composition can be further suppressed.

(acid)
The polishing composition of the present invention preferably contains an acid in order to adjust the pH of the polishing composition to a desired value. In this specification, the compound represented by formula (1) or a salt thereof as an additive is treated as being different from an acid as a pH adjuster.

The acid is not particularly limited, and may be either an inorganic acid or an organic acid. Examples of organic acids include formic acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, oleic acid, linoleic acid, linolenic acid, and arachidonic acid. , docosahexaenoic acid, eicosapentaenoic acid, isophthalic acid, terephthalic acid, gallic acid, mellitic acid, cinnamic acid, fumaric acid, maleic acid, aconitic acid, nitrocarboxylic acid, citric acid, succinic acid, malonic acid, tartaric acid, lactic acid, malic acid, acetic acid, phthalic acid, glycolic acid, crotonic acid, valeric acid, 2-hydroxybutyric acid, γ-hydroxybutyric acid, 2-hydroxyisobutyric acid, 3-hydroxyisobutyric acid, glyceric acid, benzoic acid, leucic acid, propionic acid , butyric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethyl carboxylic acids such as hexanoic acid, salicylic acid, oxalic acid, glutaric acid, adipic acid, pimelic acid and mandelic acid; Sulfonic acids such as taurine can be mentioned. Inorganic acids such as carbonic acid, hydrochloric acid, nitric acid, phosphoric acid, hypophosphorous acid, phosphorous acid, phosphonic acid, sulfuric acid, boric acid, hydrofluoric acid, orthophosphoric acid, pyrophosphoric acid, polyphosphoric acid, metaphosphoric acid, and hexametaphosphoric acid acid. These acids can be used alone or in combination of two or more.

The amount of the acid to be added is not particularly limited, and the amount to be added may be appropriately selected so as to achieve the desired pH range.

The above acids may be used singly or in the form of a mixture of two or more.

Although the content of the acid in the polishing composition is not particularly limited, it is preferably an amount such that the pH of the polishing composition is 1 or more and less than 5. A polishing composition having such a pH is excellent in storage stability. Moreover, handling of the polishing composition is easy. In addition, the polishing speed of the object to be polished can be improved.

(Additive)
The additive adsorbs to the surface of the polysilicon film or the silicon oxide film, and suppresses the contact of abrasive grains due to the steric hindrance effect, thereby acting to suppress the polishing rate of these surfaces. The polishing composition of the present invention contains a compound represented by the following formula (1) or a salt thereof.

In formula (1), R ¹ is a substituted or unsubstituted hydrocarbon group having 6 to 30 carbon atoms, and R ² is a hydrogen atom or a substituted or unsubstituted hydrocarbon group having 1 to 30 carbon atoms. is a group, X is a single bond or -CO-, and Y is a divalent hydrocarbon group having 1 to 30 carbon atoms which may have a substituent.

If the number of carbon atoms in R ¹ is 5 or less, it is difficult to obtain the effect of steric hindrance by R ¹ on the surface of the object to be polished that includes a silicon oxide film or a polysilicon film. polished to As a result, high selectivity in polishing silicon nitride films cannot be obtained. On the other hand, when the number of carbon atoms in R ¹ exceeds 30, the water-solubility is lowered, so the dispersion stability of the compound of formula (1) or its salt may be lowered. The number of carbon atoms in R ¹ is preferably 6 or more and 22 or less, more preferably 10 or more and 20 or less, and particularly preferably 12 or more and 18 or less. .

The hydrocarbon group is not particularly limited, but may be an alkyl group, an alkenyl group, an alkadienyl group, an alkatrienyl group, an alkynyl group, a cycloalkyl group, an aryl group, etc., preferably an alkyl group or an alkenyl group.

The alkyl group may be linear or branched, and may be a hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group (cetyl group), heptadecyl group, octadecyl group (stearyl group), nonadecyl group, icosyl group, eicosyl group, heneicosyl group, heneicosyl group, docosyl group, tricosyl group, tetracosyl group, pentacosyl group, hexacosyl group, heptacosyl group, octacosyl group, nonacosyl group, isohexyl group, 2-ethylhexyl group and the like. Among them, linear ones can be preferably used. Among these, decyl group, undecyl group, dodecyl group and heptadecyl group are preferable, and dodecyl group and heptadecyl group are more preferable.

Examples of alkenyl groups include hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, octadecenyl, and octadecatrienyl. (5Z,8Z,11Z,14Z)-nonadeca-5,8,11,14-tetraenyl group, icosenyl group, henicosenyl group, docosenyl group, triacontenyl group and the like. Among them, linear ones can be preferably used. Among these, nonenyl group, decenyl group, undecenyl group, dodecenyl group and heptadecenyl group are preferred.

The alkadienyl group includes, for example, a hexadienyl group, a heptadienyl group, an octadienyl group, a 1-ethylpentadienyl group, a 2-methylpentadienyl group and the like.

Examples of alkatrienyl groups include hexatrienyl, heptatrienyl, octatrienyl, 1-methylhexatrienyl, and 2-methylhexatrienyl groups.

Examples of substituents include, but are not limited to, halogen atoms (fluorine, chlorine, bromine, or iodine atoms), hydroxyl groups, nitro groups, carbonyl groups, and the like.

In Formula (1), R ² is a hydrogen atom or a substituted or unsubstituted hydrocarbon group having 1 to 30 carbon atoms. Examples of the substituted or unsubstituted hydrocarbon group having 1 to 30 carbon atoms include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, tert-butyl group, and pentyl. group, isopentyl group, tert-pentyl group, neopentyl group, hexyl group, heptyl group, octyl group, isohexyl group, 2-ethylhexyl group and the like. R ² is preferably a hydrogen atom or a linear or branched alkyl group having 1 to 10 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, particularly preferably is a hydrogen atom or a methyl group. As the substituent for R ² , the same substituents as those exemplified for R ¹ can be used.

Y is an optionally substituted divalent hydrocarbon group having 1 to 30 carbon atoms. Substituents similar to those described above can be used.

Y is preferably an alkylene group having 1 to 4 carbon atoms or a group represented by the following formula (2). With the above configuration, the effects of the present invention can be obtained more remarkably.

In formula (2), Z is an alkylene group having 1 or more and 3 or less carbon atoms. Examples of the alkylene group having 1 to 3 carbon atoms include methylene group, ethylene group, n-propylene group and the like. Preferably Z is a methylene group or an ethylene group. The alkylene group having 1 or more and 3 or less carbon atoms may have a substituent, and the same substituents as those described above can be used as the substituent.

The salt of the compound represented by the above formula (1) is not particularly limited, but examples thereof include alkali metal salts such as sodium salts and potassium salts, Group 2 element salts such as calcium salts, amine salts, and ammonium salts. be done. Of these, sodium salts are preferred.

Specific examples of the compound represented by formula (1) or a salt thereof include N-oleoylsarcosine, N-lauroylsarcosine, N-oleoylglutamic acid, N-lauroylglutamic acid, N-oleoylaspartic acid, N- lauroyl aspartic acid, N-oleoyl-N-methylalanine, N-lauroyl-N-methylalanine, and salts thereof.

One of the compounds represented by formula (1) or a salt thereof may be used alone, or two or more of them may be used in combination.

The content (concentration) of the additive represented by the formula (1) or a salt thereof in the polishing composition is not particularly limited. For example, the lower limit of the content (concentration) of the additive is preferably 0.0001% by mass or more, more preferably 0.0001% by mass or more, with respect to the final polishing composition, and 0 More preferably, it is at least 0.001% by mass. Within this range, it is possible to suppress the polishing rate of a silicon oxide film or a polysilicon film and selectively polish an object having a silicon-nitrogen bond such as a silicon nitride film. Moreover, it is possible to suppress the deterioration of the surface condition such as roughening of the polished surface. The upper limit of the content (concentration) of the additive is preferably 1% by mass or less, more preferably 0.1% by mass or less, relative to the final polishing composition. Within this range, an excellent polishing rate can be obtained for an object to be polished having silicon-nitrogen bonds such as a silicon nitride film. Moreover, it is preferable from the viewpoint of storage stability and cost. When two or more of the compounds represented by formula (1) or salts thereof are used in combination, the total content is preferably within the above range.

(dispersion medium)
The polishing composition of the present invention preferably contains a dispersion medium for dispersing or dissolving each component. Here, the dispersion medium is not particularly limited, but water is preferred. From the viewpoint of suppressing the inhibition of the actions of other components, water containing as few impurities as possible is more preferable. Pure water, ultrapure water, or distilled water is preferred.

(pH)
The polishing composition according to one aspect of the present invention preferably contains a dispersion medium and has a pH of 1 or more and less than 5. A polishing composition having such a pH is excellent in storage stability. Moreover, handling of the polishing composition is easy. When the pH of the polishing composition is less than 5, the positive charge on the surface of the object to be polished is reduced, and abrasive grains having a negatively charged surface (for example, silica having an organic acid fixed to the surface) are used. Sometimes it becomes easier to polish the object to be polished at high speed. From the viewpoint of polishing the object to be polished with the polishing composition at a sufficient polishing rate, the pH of the polishing composition is more preferably 4 or less, and particularly preferably 3 or less. From the viewpoint of safety, the lower limit of the pH value of the polishing composition is preferably 1 or more, more preferably 1.5 or more.

(other ingredients)
The polishing composition according to one embodiment of the present invention comprises, in addition to the compound represented by formula (1) or a salt thereof, which is an abrasive grain and an additive, a compound represented by formula (1) or its salt, if necessary. In addition to salts, other components such as complexing agents, preservatives, antifungal agents, reducing agents, surfactants, and water-soluble polymers may be contained. Complexing agents, preservatives, antifungal agents, reducing agents, surfactants, and water-soluble polymers are not particularly limited, and known ones used in the field of polishing compositions can be used. On the other hand, however, the polishing composition according to the present invention preferably does not substantially contain an oxidizing agent. When the polishing composition contains an oxidizing agent, when the composition is supplied to a silicon film or the like as an object to be polished, the surface of the object to be polished is oxidized to form an oxide film, When this is scraped off by the abrasive grains, the polishing selectivity can be lowered. The oxidizing agent referred to here can promote the formation of an oxide film on the surface of the silicon film, and specific examples of the oxidizing agent include hydrogen peroxide (H ₂ O ₂ ), hydrogen peroxide, peracetic acid, and percarbonic acid. salt, urea peroxide, sodium persulfate, potassium persulfate, ammonium persulfate, potassium monopersulfate, oxone, sodium dichloroisocyanurate and the like. Here, the fact that the polishing composition does not substantially contain an oxidizing agent means that it does not contain an oxidizing agent at least intentionally. Therefore, a trace amount (for example, the molar concentration of the oxidizing agent in the polishing composition is 0.0005 mol/L or less, preferably 0.0001 mol or less, more preferably 0.00001 mol/L) due to the raw material, manufacturing method, etc. L or less, particularly preferably 0.000001 mol/L or less) of the oxidizing agent is inevitably included in the concept of the polishing composition substantially free of the oxidizing agent. can be

The polishing composition of the present invention does not substantially contain the di-quaternary compound described in, for example, JP-A-2013-42131. Moreover, it is preferable that the polishing composition of the present invention does not substantially contain an iodine compound (eg, potassium iodate) that can trigger generation of iodine gas. Specifically, the content of the compound is preferably 10% by mass or less (lower limit: 0% by mass), and 5% by mass or less (lower limit: 0% by mass) with respect to the polishing composition. is more preferable.

As additives other than the compound represented by the above formula (1) or a salt thereof, additives used particularly for improving the polishing rate of a silicon nitride film relative to a silicon oxide film or a polysilicon film include: When the surface of the abrasive grains in the polishing composition is negatively charged, it is preferable not to contain those having a sulfo group. A sulfo group may be dissociated and ionized in a dispersion medium such as water, adsorbed to the surface of a positively charged silicon nitride film, and reversed negatively. At this time, both the surface of the abrasive grains and the surface of the silicon nitride film are negatively charged, which may reduce the polishing rate of the silicon nitride film.

[Method for producing polishing composition]
The method for producing the polishing composition of the present invention is not particularly limited. For example, it can be obtained by stirring and mixing in water). The details of each component are as described above. Accordingly, the present invention provides a method for producing the polishing composition of the present invention, comprising mixing the abrasive grains and the predetermined additive.

The temperature at which each component is mixed is not particularly limited, but is preferably 10 to 40° C., and may be heated to increase the dissolution rate. Also, the mixing time is not particularly limited as long as uniform mixing can be achieved.

[Polishing Method and Substrate Manufacturing Method]
As described above, the polishing composition of the present invention is suitably used for polishing a layer (object to be polished) containing silicon nitride. Accordingly, the present invention also provides a polishing method for polishing an object having a layer containing silicon nitride with the polishing composition of the present invention. The present invention also provides a substrate manufacturing method including the step of polishing a layer (object to be polished) containing silicon nitride by the polishing method.

As a polishing apparatus, a holder that holds a substrate having an object to be polished and a motor that can change the number of rotations are attached, and a polishing surface plate to which a polishing pad (abrasive cloth) can be attached is generally used. Polishing equipment can be used.

As the polishing pad, general non-woven fabric, polyurethane, porous fluororesin, and the like can be used without particular limitation. It is preferable that the polishing pad is grooved so that the polishing liquid is accumulated.

As for the polishing conditions, for example, the rotation speed of the polishing platen is preferably 10 to 500 rpm. The pressure (polishing pressure) applied to the substrate having the object to be polished is preferably 0.5 to 10 psi. The method of supplying the polishing composition to the polishing pad is also not particularly limited, and, for example, a method of continuously supplying it using a pump or the like is employed. The amount supplied is not limited, but it is preferred that the surface of the polishing pad is always covered with the polishing composition of the present invention.

After polishing, the substrate is washed in running water, water droplets adhering to the substrate are removed by a spin dryer or the like, and the substrate is dried to obtain a substrate having a layer containing silicon nitride.

The polishing composition of the present invention may be of a one-component type or a multi-component type such as a two-component type. Also, the polishing composition of the present invention may be prepared by diluting a stock solution of the polishing composition with a diluent such as water, for example, 10-fold or more.

The present invention will be described in more detail with the following examples and comparative examples. However, the technical scope of the present invention is not limited only to the following examples. Unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass" respectively. In the following examples, unless otherwise specified, the operations were carried out under the conditions of room temperature (25° C.)/relative humidity of 40 to 50% RH.

[Example 1]
(Preparation of polishing composition)
In pure water, 0.01% by mass of N-oleoyl sarcosine with respect to the final polishing composition, 0.35% by mass of maleic acid with respect to the final polishing composition, abrasive grains (sulfonic acid fixed colloidal A polishing composition was prepared by adding silica (average primary particle size: 14 nm, average secondary particle size: 40 nm) in an amount of 0.25% by mass relative to the final polishing composition. The pH of the polishing composition (liquid temperature: 25° C.) was confirmed with a pH meter (manufactured by HORIBA, Ltd., model number: LAQUA) and found to be 1.9.

[Examples 2 to 5 and Comparative Examples 1 to 5]
(Preparation of polishing composition)
Polishing compositions of Examples and Comparative Examples were prepared in the same manner as in Example 1, except that the type and content of each component were changed as shown in Tables 1 to 3 below.

For each polishing composition obtained above, the removal rate (Å/min) was evaluated according to the following method. The results are also shown in Table 1 below.

<Polishing test>
(Polishing equipment and polishing conditions)
In Examples 1 to 5 and Comparative Examples 1 to 5, each polishing composition was used to polish the surface of an object to be polished under the following conditions. A silicon wafer having a diameter of 200 mm and a SiN film (silicon nitride film) having a thickness of 2500 Å, a TEOS film (silicon oxide film) having a thickness of 10000 Å, or a polysilicon film having a thickness of 4000 Å was formed on the surface of the object to be polished was used.

Polishing device: Single-sided CMP polishing machine for 200 mm wafer (Mirra manufactured by Applied Materials)
Pad: Supreme RN-H (manufactured by Dow Chemical Company)
Polishing pressure: 2 psi
Polishing surface plate rotation speed: 93 rpm
Carrier rotation speed: 87 rpm
Supply amount of polishing composition: 150 mL/min
Polishing time: 60 sec.

Ex-situ dressing 15s.

<Measurement of Removal Rate>
The polishing speed (polishing rate) (Å/min) was calculated by the following formula (1).

The film thicknesses of silicon nitride (SiN), polysilicon (poly-Si), and silicon oxide (TEOS) are obtained by an optical interferometric film thickness measurement device, and evaluated by dividing the difference in film thickness before and after polishing by the polishing time. did.

According to the results in Table 1 above, by using the polishing compositions of Examples 1 to 5 containing specific additives, compared to Comparative Examples 1 to 5, the silicon nitride film was polished at a high speed, and , the polishing rate of the silicon oxide film and the polysilicon film can be suppressed.

When the additive does not have a long-chain hydrocarbon group, as in Comparative Example 1, or when it does not have an amino group, as in Comparative Examples 3 to 5, the silicon oxide film or polysilicon film , the effect of selectively polishing the silicon nitride film cannot be sufficiently obtained. Moreover, when the additive contains a sulfo group as in Comparative Example 4, the sulfo group is dissociated in water, ionized, and adsorbed on the surface of the positively charged silicon nitride film, causing negative conversion. It is considered that the negative charging of both the abrasive grains and the silicon nitride film inhibits the development of the polishing rate of the silicon nitride film. Also, polysilicon and silicon oxide are similarly suppressed in the polishing rate, so it is considered that selectivity cannot be obtained.

Claims (12)

abrasive grains;
at least one compound selected from the group consisting of compounds represented by the following formula (1) and salts thereof;
a dispersion medium;
including
The content of the abrasive grains is 0.5% by mass or less,
A polishing composition having a pH of 1 or more and less than 5 .

(In formula (1), R ¹ is a substituted or unsubstituted hydrocarbon group having 6 to 30 carbon atoms, and R ² is a hydrogen atom or a substituted or unsubstituted carbon atom having 1 to 30 carbon atoms. is a hydrogen group, X is a single bond or —CO—, and Y is a divalent hydrocarbon group having 1 to 30 carbon atoms which may have a substituent.) 2. The polishing composition according to claim 1, wherein Y in formula (1) is an alkylene group having 1 to 4 carbon atoms, or a group represented by formula (2) below.

(In formula (2), Z is an alkylene group having 1 to 3 carbon atoms.) The polishing composition according to claim 1 or 2, wherein R1 in formula ( ¹ ) is a substituted or unsubstituted hydrocarbon group having 6 to 22 carbon atoms. The polishing composition according to any one of claims 1 to 3, wherein R ² in formula (1) is an alkyl group having 1 to 3 carbon atoms. The polishing composition according to any one of claims 1 to 4, wherein the abrasive grains are silica. 6. The polishing composition according to claim 5, wherein the abrasive grains are organic acid-fixed silica. The polishing composition according to any one of claims 1 to 6 , which is used for selective polishing of silicon nitride with respect to polysilicon or silicon oxide. The polishing composition according to any one of claims 1 to 7 , which is substantially free of oxidizing agents. The polishing composition according to any one of claims 1 to 8, wherein the content of the compound represented by formula (1) or a salt thereof is 0.0001% by mass or more and 0.1% by mass or less. Any one of claims 1 to 9, comprising mixing the abrasive grains with at least one compound selected from the group consisting of the compound represented by the formula (1) and salts thereof. A method for producing the described polishing composition. A polishing method comprising polishing an object having a layer containing silicon nitride with the polishing composition according to any one of claims 1 to 9. A method for manufacturing a substrate, comprising polishing an object having a layer containing silicon nitride by the polishing method according to claim 11 .