WO2019180887A1

WO2019180887A1 - Polishing liquid, polishing liquid set, and polishing method

Info

Publication number: WO2019180887A1
Application number: PCT/JP2018/011464
Authority: WO
Inventors: 友洋岩野
Original assignee: 日立化成株式会社
Priority date: 2018-03-22
Filing date: 2018-03-22
Publication date: 2019-09-26
Also published as: WO2019181015A1; TW201940653A

Abstract

A polishing liquid that contains abrasive grains, a hydroxy acid, a polyol, and a liquid medium. The zeta potential of the abrasive grains is positive, and the hydroxy acid has one carboxyl group and 1–3 hydroxyl groups.

Description

Polishing liquid, polishing liquid set and polishing method

The present invention relates to a polishing liquid, a polishing liquid set, and a polishing method. In particular, the present invention relates to a polishing liquid, a polishing liquid set, and a polishing method that can be used in a planarization process of a substrate surface, which is a manufacturing technique of a semiconductor element. More specifically, the present invention relates to a polishing liquid that can be used in a planarization process of a shallow trench isolation (shallow trench isolation, hereinafter referred to as “STI”) insulating material, premetal insulating material, interlayer insulating material, etc. The present invention relates to a polishing liquid set and a polishing method.

In recent semiconductor device manufacturing processes, the importance of processing technology for higher density and miniaturization is increasing. CMP (Chemical Mechanical Polishing), which is one of the processing techniques, is used to form STI, planarize premetal insulating material or interlayer insulating material, plug or embedded metal wiring in the manufacturing process of semiconductor devices. This technology is essential for formation.

Examples of the most frequently used polishing liquid include silica-based polishing liquids containing silica (silicon oxide) particles such as fumed silica and colloidal silica as abrasive grains. The silica-based polishing liquid is characterized by high versatility, and a wide variety of materials can be polished regardless of insulating materials and conductive materials by appropriately selecting the abrasive content, pH, additives, and the like.

On the other hand, as a polishing liquid mainly for an insulating material such as silicon oxide, the demand for a polishing liquid containing cerium compound particles as an abrasive is also increasing. For example, a ceria-based polishing liquid containing ceria (cerium oxide) particles as abrasive grains can polish silicon oxide at high speed even with a lower abrasive grain content than a silica-based polishing liquid (see, for example, Patent Documents 1 and 2 below).

JP-A-10-106994 Japanese Patent Application Laid-Open No. 08-022970

By the way, when the polishing liquid containing abrasive grains is stored for a certain period, if the abrasive grains change due to aggregation of the abrasive grains, the polishing rate obtained using the polishing liquid may decrease. . Therefore, it is required for the polishing liquid containing abrasive grains to improve the dispersion stability of the abrasive grains.

The present invention is intended to solve the above-mentioned problems, and an object thereof is to provide a polishing liquid having excellent dispersion stability of abrasive grains. An object of the present invention is to provide a polishing liquid set for obtaining the polishing liquid. An object of the present invention is to provide a polishing method using the polishing liquid or the polishing liquid set.

The present inventor has found that although the polishing characteristics such as the polishing rate of the insulating material can be improved by using a polishing liquid containing polyol, the abrasive grains may aggregate in the polishing liquid. On the other hand, the present inventor uses abrasive grains having a positive zeta potential (cationic abrasive grains), a specific hydroxy acid, and a polyol in combination in a polishing liquid containing a polyol. It has been found that the dispersion stability of can be improved.

The polishing liquid according to the present invention contains abrasive grains, a hydroxy acid, a polyol, and a liquid medium, the abrasive grains have a positive zeta potential, and the hydroxy acid contains one carboxyl group and 1 to It has 3 hydroxyl groups.

The polishing liquid according to the present invention has excellent abrasive dispersion stability. According to such a polishing liquid, it is possible to suppress a decrease in the polishing rate even when the polishing liquid is stored for a certain period.

The hydroxy acid may contain a compound having one carboxyl group and one hydroxyl group, or may contain a compound having one carboxyl group and two hydroxyl groups.

The polyol preferably includes a polyether polyol.

The content of the hydroxy acid is preferably 0.01 to 1.0% by mass.

The content of the polyol is preferably 0.05 to 5.0% by mass.

One aspect of the present invention relates to the use of the polishing liquid for polishing a surface to be polished containing silicon oxide. That is, the polishing liquid according to the present invention is preferably used for polishing a surface to be polished containing silicon oxide.

In the polishing liquid set according to the present invention, the constituents of the polishing liquid are stored separately as a first liquid and a second liquid, and the first liquid includes the abrasive grains and a liquid medium. The second liquid includes the hydroxy acid, the polyol, and a liquid medium. According to the polishing liquid set concerning the present invention, the same effect as the polishing liquid concerning the present invention can be acquired.

The polishing method according to the present invention may comprise a step of polishing a surface to be polished using the polishing liquid, and is obtained by mixing the first liquid and the second liquid in the polishing liquid set. You may provide the process of grind | polishing a to-be-polished surface using the polishing liquid produced. According to these polishing methods, the same effect as the polishing liquid according to the present invention can be obtained by using the polishing liquid or the polishing liquid set.

One aspect of a polishing method according to the present invention is a method for polishing a substrate having an insulating material and silicon nitride, and includes a step of selectively polishing the insulating material with respect to silicon nitride using the polishing liquid. Alternatively, the method may include a step of selectively polishing the insulating material with respect to silicon nitride using a polishing liquid obtained by mixing the first liquid and the second liquid in the polishing liquid set. Good. According to these polishing methods, by using the polishing liquid or the polishing liquid set, the same effect as the polishing liquid according to the present invention is obtained when the insulating material is selectively polished with respect to silicon nitride. be able to.

Another aspect of the polishing method according to the present invention is a method for polishing a substrate having an insulating material and polysilicon, comprising the step of selectively polishing the insulating material with respect to polysilicon using the polishing liquid. And a step of selectively polishing the insulating material with respect to polysilicon using a polishing liquid obtained by mixing the first liquid and the second liquid in the polishing liquid set. Also good. According to these polishing methods, by using the polishing liquid or the polishing liquid set, the same effect as the polishing liquid according to the present invention can be obtained when the insulating material is selectively polished with respect to polysilicon. be able to.

According to the present invention, a polishing liquid having excellent dispersion stability of abrasive grains can be provided. According to the present invention, a polishing liquid set for obtaining the polishing liquid can be provided. According to the present invention, a polishing method using the polishing liquid or the polishing liquid set can be provided.

According to the present invention, it is possible to provide the use of the polishing liquid or the polishing liquid set for the planarization process of the substrate surface. According to the present invention, it is possible to provide the use of the polishing liquid or the polishing liquid set for the planarization process of the STI insulating material, the premetal insulating material, or the interlayer insulating material. ADVANTAGE OF THE INVENTION According to this invention, use of the polishing liquid or polishing liquid set for the grinding | polishing process which grind | polishes an insulating material selectively with respect to a stopper material can be provided.

Hereinafter, the polishing liquid, the polishing liquid set, and the polishing method using these according to the embodiment of the present invention will be described in detail.

<Definition>
In this specification, a numerical range indicated by using “to” indicates a range including the numerical values described before and after “to” as the minimum value and the maximum value, respectively. In the numerical ranges described stepwise in this specification, the upper limit value or the lower limit value of a numerical range in a certain step may be replaced with the upper limit value or the lower limit value of a numerical range in another step. In the numerical range described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the values shown in the examples. “A or B” only needs to include either A or B, and may include both. The materials exemplified in the present specification can be used singly or in combination of two or more unless otherwise specified. In the present specification, the content of each component in the composition is the total amount of the plurality of substances present in the composition unless there is a specific notice when there are a plurality of substances corresponding to each component in the composition. Means.

In this specification, “polishing liquid” is defined as a composition that touches the surface to be polished during polishing. The phrase “polishing liquid” itself does not limit the components contained in the polishing liquid. As will be described later, the polishing liquid according to the present embodiment contains abrasive grains. Abrasive grains are also referred to as “abrasive particles”, but are referred to herein as “abrasive grains”. The abrasive grains are generally solid particles, and the object to be removed is removed (removed) by the mechanical action of the abrasive grains and the chemical action of the abrasive grains (mainly the surface of the abrasive grains) during polishing. However, the present invention is not limited to this.

<Polishing liquid>
The polishing liquid according to this embodiment is, for example, a polishing liquid for CMP. The polishing liquid according to this embodiment contains abrasive grains, a hydroxy acid, a polyol, and a liquid medium. The abrasive grains have a positive zeta potential, and the hydroxy acid contains one carboxyl group and 1 With ~ 3 hydroxyl groups. The polishing liquid according to the present embodiment has excellent dispersion stability of abrasive grains. According to the polishing liquid according to the present embodiment, even when the polishing liquid is stored for a certain period (for example, 168 hours or more), it is possible to suppress a decrease in the polishing rate. In addition, according to the polishing liquid according to the present embodiment, the polishing speed decreases even when the polishing liquid is stored for a certain period (for example, 168 hours or more) while obtaining a high polishing speed immediately after the preparation of the polishing liquid. This can be suppressed.

The cause of the effect of obtaining excellent dispersion stability of the abrasive grains is not necessarily clear, but the present inventor presumes as follows.
That is, COO ⁻ generated by the dissociation of protons (H ⁺ ) from the carboxyl group of the hydroxy acid can be adsorbed to abrasive grains having a positive zeta potential. When a hydroxy acid having two or more carboxyl groups is used, the abrasive grains are likely to be aggregated because the abrasive grains are likely to be bonded to each other via COO ⁻ adsorbed on the abrasive grains. On the other hand, by keeping the number of carboxyl groups of the hydroxy acid to one in the polishing liquid containing polyol, it becomes difficult for the abrasive grains to bond with each other via COO 2 ⁻ and aggregation of the abrasive grains is easily suppressed.
Further, hydroxy acids can be bonded via a hydroxyl group. Therefore, if the number of hydroxyl groups of the hydroxy acid is large, the abrasive grains tend to aggregate through the hydroxyl group of the hydroxy acid adsorbed on the abrasive grains. In contrast, in the polishing liquid containing polyol, the number of hydroxyl groups of hydroxy acid is limited to 1 to 3, which makes it difficult for the abrasive grains to bond with each other via the hydroxyl group of hydroxy acid, thereby suppressing the aggregation of the abrasive grains. Cheap.
With these actions, the polishing liquid according to the present embodiment can achieve excellent dispersion stability of the abrasive grains.

(Abrasive grains)
The polishing liquid according to the present embodiment contains abrasive grains having a positive zeta potential in the polishing liquid as cationic abrasive grains. The abrasive preferably contains at least one selected from the group consisting of ceria, silica, alumina, zirconia, yttria, and tetravalent metal element hydroxide from the viewpoint of polishing the insulating material at a high polishing rate. It is more preferable to contain. An abrasive can be used individually by 1 type or in combination of 2 or more types.

The “tetravalent metal element hydroxide” is a compound containing a tetravalent metal (M ⁴⁺ ) and at least one hydroxide ion (OH ⁻ ). The hydroxide of the tetravalent metal element may contain anions other than hydroxide ions (for example, nitrate ions NO ₃ ⁻ and sulfate ions SO ₄ ²⁻ ). For example, a hydroxide of a tetravalent metal element may include an anion (for example, nitrate ion NO ₃ ⁻ and sulfate ion SO ₄ ²⁻ ) bonded to the tetravalent metal element. A hydroxide of a tetravalent metal element can be produced by reacting a salt (metal salt) of a tetravalent metal element with an alkali source (base).

When the abrasive grains contain ceria, the lower limit of the ceria content is preferably 50% by mass or more and more than 50% by mass on the basis of the entire abrasive grains from the viewpoint of further improving the polishing rate of the insulating material. Preferably, 60% by mass or more is more preferable, 70% by mass or more is particularly preferable, 80% by mass or more is very preferable, 90% by mass or more is very preferable, 95% by mass or more is even more preferable, and 98% by mass or more is more preferable. Preferably, 99 mass% or more is more preferable.

From the viewpoint of further improving the polishing rate of the insulating material, the lower limit of the average particle size of the abrasive grains in the slurry in the polishing liquid or the polishing liquid set described below is preferably 20 nm or more, more preferably 30 nm or more, and 40 nm or more. More preferably, 50 nm or more is particularly preferable, 100 nm or more is very preferable, 120 nm or more is very preferable, 150 nm or more is more preferable, 200 nm or more is more preferable, 250 nm or more is more preferable, and 300 nm or more is particularly preferable. The upper limit of the average grain size of the abrasive grains is preferably 1000 nm or less, more preferably 800 nm or less, still more preferably 600 nm or less, particularly preferably 500 nm or less, and particularly preferably 400 nm or less, from the viewpoint of further suppressing scratches on the surface to be polished. Is very preferred. From these viewpoints, the average grain size of the abrasive grains is more preferably 20 to 1000 nm.

The “average particle diameter” of the abrasive grains means the average secondary particle diameter of the abrasive grains. For example, the average particle diameter of the abrasive grains is a volume average particle diameter, and a light diffraction scattering type particle size distribution meter (for example, a product manufactured by Microtrack Bell Co., Ltd.) is used for a polishing liquid or a slurry in a polishing liquid set described later. Name: Microtrack MT3300EXII).

The zeta potential (surface potential) of the abrasive grains in the polishing liquid is positive from the viewpoint of obtaining excellent abrasive dispersion stability (the zeta potential exceeds 0 mV). The lower limit of the zeta potential of the abrasive is preferably 10 mV or more, more preferably 20 mV or more, still more preferably 25 mV or more, particularly preferably 30 mV or more, and particularly preferably 40 mV or more from the viewpoint of easily obtaining excellent abrasive dispersion stability. Preferably, 50 mV or more is very preferable. The upper limit of the zeta potential of the abrasive grains is not particularly limited, but is preferably 200 mV or less. From these viewpoints, the zeta potential of the abrasive grains is more preferably 10 to 200 mV.

The zeta potential of the abrasive grains can be measured using, for example, a dynamic light scattering type zeta potential measuring device (for example, trade name: DelsaNano C, manufactured by Beckman Coulter, Inc.). The zeta potential of the abrasive can be adjusted using an additive. For example, by bringing a monocarboxylic acid (for example, acetic acid) into contact with an abrasive containing ceria, an abrasive having a positive zeta potential can be obtained.

The lower limit of the abrasive content is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, based on the total mass of the polishing liquid, from the viewpoint of further improving the polishing rate of the insulating material. 0.02% by mass or more is more preferable, 0.03% by mass or more is particularly preferable, 0.04% by mass or more is very preferable, 0.05% by mass or more is very preferable, and 0.1% by mass or more is even more preferable. 0.15 mass% or more is more preferable. The upper limit of the abrasive content is preferably 20% by mass or less, more preferably 15% by mass or less, and more preferably 10% by mass based on the total mass of the polishing liquid from the viewpoint of easily obtaining excellent abrasive dispersion stability. The following is more preferable, 5% by mass or less is particularly preferable, 4% by mass or less is very preferable, 3% by mass or less is very preferable, 1% by mass or less is more preferable, 0.5% by mass or less is more preferable, 0 Is more preferably 3% by mass or less, particularly preferably 0.2% by mass or less. From these viewpoints, the content of the abrasive grains is more preferably 0.005 to 20% by mass based on the total mass of the polishing liquid.

(Additive)
The polishing liquid according to this embodiment contains an additive. Here, the “additive” refers to a substance contained in the polishing liquid in addition to the abrasive grains and the liquid medium. By using the additive, for example, polishing characteristics such as polishing speed and polishing selectivity; polishing liquid characteristics such as abrasive dispersion stability and storage stability can be adjusted.

[Hydroxy acid]
The polishing liquid according to this embodiment contains a hydroxy acid having one carboxyl group and 1 to 3 hydroxyl groups (hereinafter referred to as “specific hydroxy acid”) as an essential additive. In the specific hydroxy acid, the number of carboxyl groups is 1, and the number of hydroxyl groups is 1 to 3. The “hydroxyl group” does not include “—OH” in the carboxyl group.

The specific hydroxy acid may include a compound having one carboxyl group and one hydroxyl group, or may include a compound having one carboxyl group and two hydroxyl groups. A compound having a carboxyl group and three hydroxyl groups may be included. The said specific hydroxy acid can be used individually by 1 type or in combination of 2 or more types. The number of hydroxyl groups in the specific hydroxy acid is preferably 1 to 2 and more preferably 2 from the viewpoint of easily obtaining excellent abrasive dispersion stability.

Examples of the specific hydroxy acid include glycolic acid, glyceric acid, lactic acid (for example, DL-lactic acid), 2,2-bis (hydroxymethyl) propionic acid, 2,2-bis (hydroxymethyl) butyric acid, N, N-bis ( 2-hydroxyethyl) glycine, N- [2-hydroxy-1,1-bis (hydroxymethyl) ethyl] glycine, bicine, tricine, tyrosine, serine, threonine and the like. The specific hydroxy acid is lactic acid (for example, DL-lactic acid), 2,2-bis (hydroxymethyl) propionic acid, 2,2-bis (hydroxymethyl) butyric acid from the viewpoint of easily obtaining excellent abrasive dispersion stability. N, N-bis (2-hydroxyethyl) glycine and N- [2-hydroxy-1,1-bis (hydroxymethyl) ethyl] glycine are preferably included.

The specific hydroxy acid preferably contains an aliphatic hydroxy acid from the viewpoint of easily obtaining excellent abrasive dispersion stability. The specific hydroxy acid may contain a hydroxy acid containing a nitrogen atom or may contain a hydroxy acid containing no nitrogen atom.

The upper limit of the hydroxyl value of the specific hydroxy acid is preferably 1500 or less, more preferably 1300 or less, still more preferably 1100 or less, particularly preferably 1000 or less, and particularly preferably 900 or less from the viewpoint of easily obtaining excellent abrasive dispersion stability. Is very preferred. The lower limit of the hydroxyl value of the specific hydroxy acid is preferably 50 or more, more preferably 150 or more, further preferably 250 or more, particularly preferably 500 or more, and 600 or more from the viewpoint of easily obtaining excellent abrasive dispersion stability. Is very preferable, and 650 or more is very preferable. From these viewpoints, the hydroxyl value of the specific hydroxy acid is more preferably 50 to 1500. The “hydroxyl value” is a numerical value that serves as an index of the number of hydroxyl groups contained in the hydroxy acid, and is calculated from the following formula (1).
Hydroxyl value = 56110 × number of hydroxyl groups / molecular weight (1)

The lower limit of the content of the specific hydroxy acid is preferably 0.01% by mass or more, preferably 0.03% by mass or more, based on the total mass of the polishing liquid, from the viewpoint of easily obtaining excellent abrasive dispersion stability. More preferably, 0.05% by mass or more is further preferable, 0.08% by mass or more is particularly preferable, and 0.1% by mass or more is extremely preferable. The upper limit of the content of the specific hydroxy acid is preferably 1.0% by mass or less, more preferably 0.8% by mass or less, based on the total mass of the polishing liquid, from the viewpoint of easily obtaining an appropriate polishing rate of the insulating material. Preferably, 0.5% by mass or less is more preferable, 0.4% by mass or less is particularly preferable, 0.3% by mass or less is extremely preferable, and 0.2% by mass or less is very preferable. From these viewpoints, the content of the specific hydroxy acid is more preferably 0.01 to 1.0% by mass based on the total mass of the polishing liquid.

The polishing liquid according to this embodiment may contain a hydroxy acid other than the specific hydroxy acid. Examples of such a hydroxy acid include a hydroxy acid having 2 or more carboxyl groups, a hydroxy acid having 4 or more hydroxyl groups, and the like. Specific examples include glucuronic acid, gluconic acid, citric acid, tartaric acid and the like.

The lower limit of the content of the specific hydroxy acid in the polishing liquid according to the present embodiment is 50% by mass based on the total mass of hydroxy acid contained in the polishing liquid from the viewpoint of easily obtaining excellent abrasive dispersion stability. The above is preferable, 70% by mass or more is more preferable, 90% by mass or more is further preferable, 95% by mass or more is particularly preferable, 97% by mass or more is very preferable, and 99% by mass or more is very preferable.

[Polyol]
The polishing liquid according to this embodiment contains a polyol (excluding a compound corresponding to a hydroxy acid) as an essential additive. A polyol is a compound having two or more hydroxyl groups in the molecule.

Polyols include polyglycerin, polyvinyl alcohol, polyalkylene glycol, polyoxyalkylene glycol, polyoxyalkylene sorbitol ether (polyoxypropylene sorbitol ether, etc.), polyoxyalkylene condensates of ethylenediamine (ethylenediamine tetrapolyoxyethylene polyoxypropylene, etc.) ), 2,2-bis (4-polyoxyalkylene-oxyphenyl) propane, polyoxyalkylene glyceryl ether, polyoxyalkylene diglyceryl ether, polyoxyalkylene trimethylolpropane ether, polyoxyalkylene pentaerythritol ether, polyoxyalkylene And methyl glucoside.

Polyols are polyglycerin, polyoxyalkylene glycol, polyoxyalkylene sorbitol ether, polyoxyalkylene glyceryl ether, polyoxyalkylene trimethylol propane ether, and polyoxyalkylene from the viewpoint of easily obtaining excellent abrasive dispersion stability. It is preferable to include at least one selected from the group consisting of pentaerythritol ether, and it is more preferable to include polyoxyalkylene trimethylolpropane ether. The polyol preferably contains a polypole having no aromatic group from the viewpoint of easily obtaining excellent abrasive dispersion stability.

As a polyol, it is easy to form a protective layer on the surface to be polished and adjust the polishing rate gently, so overpolishing of the recesses is easily suppressed, and it is easy to finish the polished wafer flat From this viewpoint, polyether polyol (polyol having a polyether structure) is preferable.

The polyether polyol preferably has a polyoxyalkylene structure. This makes it easier to form a protective layer on the surface to be polished and adjust the polishing rate gently, so that overpolishing of the recesses can be more easily suppressed and the polished wafer can be finished flat. It is even easier. The number of carbon atoms of the oxyalkylene group (structural unit) in the polyoxyalkylene structure is preferably 1 or more and more preferably 2 or more from the viewpoint of easily obtaining excellent abrasive dispersion stability. The number of carbon atoms of the oxyalkylene group (structural unit) in the polyoxyalkylene structure is preferably 5 or less, more preferably 4 or less, and even more preferably 3 or less from the viewpoint of easily obtaining excellent abrasive dispersion stability. From these viewpoints, the carbon number is preferably 1 to 5. The polyoxyalkylene chain may be a homopolymer chain or a copolymer chain. The copolymer chain may be a block polymer chain or a random polymer chain.

Polyols can be used singly or in combination of two or more.

The lower limit of the polyol content is preferably 0.05% by mass or more based on the total mass of the polishing liquid from the viewpoint of easily obtaining excellent dispersion stability of the abrasive grains and the viewpoint of further improving the flatness. 0.1% by mass or more is more preferable, 0.2% by mass or more is further preferable, 0.3% by mass or more is particularly preferable, 0.4% by mass or more is very preferable, and 0.5% by mass or more is very preferable. . The upper limit of the polyol content is preferably 5.0% by mass or less, more preferably 3.0% by mass or less, based on the total mass of the polishing liquid, from the viewpoint of easily obtaining an appropriate polishing rate of the insulating material. 0.0 mass% or less is more preferable, and 1.0 mass% or less is particularly preferable. From these viewpoints, the polyol content is more preferably 0.05 to 5.0% by mass based on the total mass of the polishing liquid.

[Optional additives]
The polishing liquid according to this embodiment may further contain any additive (except for the compound corresponding to the hydroxy acid and the compound corresponding to the polyol). Optional additives include amino acids, water-soluble polymers, oxidizing agents (eg, hydrogen peroxide) and the like. Each of these additives can be used alone or in combination of two or more.

The amino acid has the effect of stabilizing the pH of the polishing liquid, the viewpoint of easily obtaining excellent dispersion stability of the abrasive grains, and the effect of further improving the polishing rate of the insulating material. As amino acids, arginine, lysine, aspartic acid, glutamic acid, asparagine, glutamine, histidine, proline, tryptophan, glycine, α-alanine, β-alanine, methionine, cysteine, phenylalanine, leucine, valine, isoleucine, glycylglycine, glycine Examples include silalanine.

The water-soluble polymer has flatness, in-plane uniformity, polishing selectivity of silicon oxide with respect to silicon nitride (silicon oxide polishing rate / silicon nitride polishing rate), polishing selectivity of silicon oxide with respect to polysilicon (of silicon oxide) This has the effect of adjusting polishing characteristics such as (polishing rate / polysilicon polishing rate). Here, the “water-soluble polymer” is defined as a polymer that dissolves 0.1 g or more in 100 g of water.

The water-soluble polymer is not particularly limited, and polyacrylic acid polymers such as polyacrylic acid, polyacrylic acid copolymer, polyacrylic acid salt, and polyacrylic acid copolymer salt; polymethacrylic acid, polymethacrylic acid Polymethacrylic acid polymers such as salts; polyacrylamide; polydimethylacrylamide; polysaccharides such as alginic acid, pectic acid, carboxymethylcellulose, agar, curdlan, dextrin, cyclodextrin, pullulan; vinyl polymers such as polyvinylpyrrolidone and polyacrolein Polyethylene glycol and the like. A water-soluble polymer can be used individually by 1 type or in combination of 2 or more types.

In the case of using an amino acid or an oxidizing agent, the content is preferably 0.0001 to 10% by mass based on the total mass of the polishing liquid from the viewpoint of obtaining the additive effect while suppressing sedimentation of the abrasive grains. .

When using a water-soluble polymer, the lower limit of the content of the water-soluble polymer is based on the total mass of the polishing liquid from the viewpoint of obtaining the effect of adding the water-soluble polymer while suppressing sedimentation of abrasive grains. 0.0001 mass% or more is preferable, 0.001 mass% or more is more preferable, and 0.01 mass% or more is still more preferable. The upper limit of the content of the water-soluble polymer is preferably 10% by mass or less, preferably 5% by mass based on the total mass of the polishing liquid from the viewpoint of obtaining the effect of adding the water-soluble polymer while suppressing sedimentation of the abrasive grains. % Or less is more preferable, 1 mass% or less is further more preferable, and 0.5 mass% or less is particularly preferable.

(Liquid medium)
The liquid medium in the polishing liquid according to this embodiment is not particularly limited, but water such as deionized water or ultrapure water is preferable. The content of the liquid medium may be the remainder of the polishing liquid excluding the content of other components and is not particularly limited.

(Polishing liquid characteristics)
The lower limit of the pH of the polishing liquid according to the present embodiment is preferably 2.0 or more, more preferably 2.5 or more, still more preferably 3.0 or more, from the viewpoint of easily obtaining excellent abrasive dispersion stability. 3.2 or higher is particularly preferable, 3.5 or higher is extremely preferable, and 4.0 or higher is very preferable. The upper limit of the pH is preferably 7.0 or less, more preferably 6.5 or less, still more preferably 6.0 or less, and particularly preferably 5.0 or less, from the viewpoint of easily obtaining excellent abrasive dispersion stability. From these viewpoints, the pH of the polishing liquid is more preferably 2.0 to 7.0. The pH of the polishing liquid is defined as the pH at a liquid temperature of 25 ° C.

The pH of the polishing liquid can be adjusted by an acid component such as an inorganic acid or an organic acid; an alkali component such as ammonia, sodium hydroxide, tetramethylammonium hydroxide (TMAH), imidazole, or alkanolamine. A buffer may be added to stabilize the pH. Moreover, you may add a buffer as a buffer (liquid containing a buffer). Examples of such a buffer include acetate buffer and phthalate buffer.

The pH of the polishing liquid according to this embodiment can be measured with a pH meter (for example, model number PHL-40 manufactured by Toa DKK Corporation). Specifically, for example, after calibrating two pH meters using a phthalate pH buffer solution (pH: 4.01) and a neutral phosphate pH buffer solution (pH: 6.86) as standard buffers, Then, the pH meter electrode is put into the polishing liquid, and the value after 2 minutes has passed and stabilized is measured. The temperature of the standard buffer solution and the polishing solution are both 25 ° C.

The polishing liquid according to the present embodiment may be stored as a one-part polishing liquid containing at least abrasive grains, the specific hydroxy acid, a polyol, and a liquid medium, and added with a slurry (first liquid). The components of the polishing liquid are mixed into a slurry and an additive liquid so as to become the polishing liquid by mixing the liquid (second liquid) and stored as a multi-liquid type (for example, two-component type) polishing liquid set. May be. The slurry includes, for example, at least abrasive grains and a liquid medium. The additive liquid includes, for example, at least a hydroxy acid, a polyol, and a liquid medium. The specific hydroxy acid, polyol, optional additive, and buffering agent are preferably contained in the additive liquid among the slurry and the additive liquid. The constituents of the polishing liquid may be stored as a polishing liquid set divided into three or more liquids.

In the polishing liquid set, the slurry and additive liquid are mixed immediately before or during polishing to prepare a polishing liquid. Further, the one-component polishing liquid may be stored as a polishing liquid storage liquid in which the content of the liquid medium is reduced, and may be diluted with the liquid medium during polishing. The multi-liquid type polishing liquid set may be stored as a slurry storage liquid and an additive liquid storage liquid with a reduced content of the liquid medium, and may be diluted with the liquid medium during polishing.

In the case of a one-component polishing liquid, the polishing liquid is supplied onto the polishing surface plate by directly supplying the polishing liquid; supplying the polishing liquid storage liquid and the liquid medium through separate pipes. , A method of supplying them by merging and mixing them; a method of supplying the polishing liquid stock solution and the liquid medium by mixing them in advance, and the like.

When storing as a multi-liquid type polishing liquid set divided into slurry and additive liquid, the polishing rate can be adjusted by arbitrarily changing the composition of these liquids. In the case of polishing using a polishing liquid set, there are the following methods for supplying the polishing liquid onto the polishing surface plate. For example, a method in which slurry and additive liquid are sent through separate pipes, and these pipes are combined and mixed to supply; a slurry storage liquid, a storage liquid for additive liquid, and a liquid medium are sent through separate pipes. , A method of supplying them by mixing and mixing them; a method of supplying the slurry and the additive solution after mixing them; a method of supplying the slurry storage solution, the additive solution storage solution and the liquid medium after mixing them in advance, etc. Can be used. Further, it is possible to use a method of supplying the slurry and the additive liquid in the polishing liquid set onto the polishing surface plate, respectively. In this case, the surface to be polished is polished using a polishing liquid obtained by mixing the slurry and the additive liquid on the polishing surface plate.

The polishing liquid set according to the present embodiment may be divided into a polishing liquid containing at least the essential component and an additive liquid containing at least an optional component such as an oxidizing agent (for example, hydrogen peroxide). In this case, polishing is performed using a mixed liquid obtained by mixing the polishing liquid and the additive liquid (the mixed liquid also corresponds to the “polishing liquid”). Further, the polishing liquid set according to this embodiment is a polishing liquid set divided into three or more liquids, a liquid containing at least a part of the essential component, a liquid containing at least the remainder of the essential component, and at least arbitrary. The aspect divided into the addition liquid containing a component may be sufficient. Each liquid constituting the polishing liquid set may be stored as a storage liquid in which the content of the liquid medium is reduced.

<Polishing method>
The polishing method (substrate polishing method or the like) according to this embodiment may include a polishing step of polishing a surface to be polished (surface to be polished of the substrate or the like) using the one-part polishing liquid. You may provide the grinding | polishing process which grind | polishes a to-be-polished surface (surface to be polished etc. of a base | substrate) using the polishing liquid obtained by mixing the slurry and additive liquid in a liquid set.

The polishing method according to the present embodiment may be a method for polishing a substrate having an insulating material and silicon nitride. For example, the one-part polishing liquid or a slurry and an additive liquid in the polishing liquid set are mixed. A polishing step of selectively polishing the insulating material with respect to silicon nitride may be provided using the polishing liquid obtained in this manner. In this case, the base may have, for example, a member containing an insulating material and a member containing silicon nitride.

Further, the polishing method according to the present embodiment may be a method for polishing a substrate having an insulating material and polysilicon. For example, the one-part polishing liquid or the slurry and additive liquid in the polishing liquid set are used. You may provide the grinding | polishing process of selectively grind | polishing an insulating material with respect to polysilicon using the polishing liquid obtained by mixing. In this case, the base may have, for example, a member containing an insulating material and a member containing polysilicon.

“Selectively polishing material A with respect to material B” means that the polishing rate of material A is higher than the polishing rate of material B under the same polishing conditions. More specifically, for example, the material A is polished at a polishing rate ratio of the polishing rate of the material A to the polishing rate of the material B of 80 or more.

In the polishing step, for example, the polishing liquid is supplied between the material to be polished and the polishing pad in a state where the material to be polished of the substrate having the material to be polished is pressed against the polishing pad (polishing cloth) of the polishing surface plate. The surface to be polished of the material to be polished is polished by relatively moving the substrate and the polishing surface plate. In the polishing step, for example, at least a part of the material to be polished is removed by polishing.

Examples of the substrate to be polished include a substrate to be polished. Examples of the substrate to be polished include a substrate in which a material to be polished is formed on a substrate related to semiconductor element manufacturing (for example, a semiconductor substrate on which an STI pattern, a gate pattern, a wiring pattern, etc. are formed). Examples of materials to be polished include insulating materials such as silicon oxide; stopper materials such as polysilicon and silicon nitride. The material to be polished may be a single material or a plurality of materials. When a plurality of materials are exposed on the surface to be polished, they can be regarded as materials to be polished. The material to be polished may be in the form of a film (film to be polished), and may be a silicon oxide film, a polysilicon film, a silicon nitride film, or the like.

By polishing the material to be polished (such as an insulating material such as silicon oxide) formed on such a substrate with the polishing liquid and removing the excess portion, unevenness on the surface of the material to be polished is eliminated, A smooth surface can be obtained over the entire surface of the material to be polished. The polishing liquid according to this embodiment is preferably used for polishing a surface to be polished containing silicon oxide.

In this embodiment, in a base body having an insulating material containing at least silicon oxide on the surface, a stopper (polishing stop layer) disposed under the insulating material, and a substrate (semiconductor substrate or the like) disposed under the stopper The insulating material can be polished. The stopper material constituting the stopper is a material whose polishing rate is lower than that of the insulating material, and polysilicon, silicon nitride and the like are preferable. In such a base, since the polishing is stopped when the stopper is exposed, the insulating material can be prevented from being excessively polished, so that the flatness of the insulating material after polishing can be improved.

Examples of a method for producing a material to be polished by the polishing liquid according to this embodiment include a low pressure CVD method, a quasi-atmospheric pressure CVD method, a plasma CVD method, and other CVD methods; a spin coating method in which a liquid material is applied to a rotating substrate. Etc.

Hereinafter, the polishing method according to this embodiment will be described by taking a polishing method of a substrate (for example, a substrate having an insulating material formed on a semiconductor substrate) as an example. In the polishing method according to the present embodiment, as a polishing apparatus, a general polishing apparatus having a holder capable of holding a substrate having a surface to be polished and a polishing surface plate to which a polishing pad can be attached can be used. Each of the holder and the polishing surface plate is provided with a motor capable of changing the rotation speed. As a polishing apparatus, for example, a polishing apparatus: Reflexion manufactured by APPLIED MATERIALS can be used.

As the polishing pad, general nonwoven fabric, foam, non-foam, etc. can be used. The material of the polishing pad is polyurethane, acrylic resin, polyester, acrylic-ester copolymer, polytetrafluoroethylene, polypropylene, polyethylene, poly-4-methylpentene, cellulose, cellulose ester, polyamide (for example, nylon (trade name)) And aramid), polyimide, polyimide amide, polysiloxane copolymer, oxirane compound, phenol resin, polystyrene, polycarbonate, epoxy resin and the like. The material of the polishing pad is preferably at least one selected from the group consisting of foamed polyurethane and non-foamed polyurethane, particularly from the viewpoint of further improving the polishing rate and flatness. It is preferable that the polishing pad is grooved so that the polishing liquid accumulates.

Although there are no limitations on the polishing conditions, the upper limit of the rotation speed of the polishing platen is preferably 200 min ⁻¹ or less so that the substrate does not pop out, and the upper limit of the polishing pressure (working load) applied to the substrate causes polishing scratches. From the viewpoint of sufficiently suppressing this, 15 psi or less is preferable. During polishing, it is preferable to continuously supply the polishing liquid to the polishing pad with a pump or the like. Although there is no restriction | limiting in this supply amount, it is preferable that the surface of a polishing pad is always covered with polishing liquid.

The substrate after polishing is preferably washed well under running water to remove particles adhering to the substrate. For cleaning, dilute hydrofluoric acid or ammonia water may be used in addition to pure water, and a brush may be used in combination to increase cleaning efficiency. In addition, after washing, it is preferable to dry the substrate after removing water droplets attached to the substrate using a spin dryer or the like.

The polishing liquid, the polishing liquid set and the polishing method according to this embodiment can be suitably used for forming STI. In order to form STI, it is preferable that the lower limit of the polishing rate ratio of the insulating material (for example, silicon oxide) to the stopper material (for example, silicon nitride and polysilicon) is 80 or more. When the polishing rate ratio is less than 80, the polishing rate of the insulating material with respect to the polishing rate of the stopper material is small, and it tends to be difficult to stop polishing at a predetermined position when forming the STI. On the other hand, if the polishing rate ratio is 80 or more, it is easy to stop polishing, which is more suitable for formation of STI. The lower limit of the polishing rate of the insulating material (for example, silicon oxide) is preferably 70 nm / min or more, more preferably 100 nm / min or more, further preferably 150 nm / min or more, particularly preferably 180 nm / min or more, and 200 nm / min or more. Highly preferred. The upper limit of the polishing rate of the stopper material (for example, silicon nitride and polysilicon) is preferably 10 nm / min or less, more preferably 7 nm / min or less, and further preferably 5 nm / min or less.

The polishing liquid, the polishing liquid set and the polishing method according to this embodiment can also be used for polishing a premetal insulating material. As the premetal insulating material, for example, phosphorus-silicate glass or boron-phosphorus-silicate glass is used in addition to silicon oxide, and silicon oxyfluoride, fluorinated amorphous carbon, and the like can also be used.

The polishing liquid, the polishing liquid set, and the polishing method according to this embodiment can be applied to materials other than insulating materials such as silicon oxide. Examples of such materials include high dielectric constant materials such as Hf-based, Ti-based, and Ta-based oxides; semiconductor materials such as silicon, amorphous silicon, SiC, SiGe, Ge, GaN, GaP, GaAs, and organic semiconductors; GeSbTe Inorganic conductive materials such as ITO; Polymer resins such as polyimides, polybenzoxazoles, acrylics, epoxies, and phenols.

The polishing liquid, the polishing liquid set, and the polishing method according to this embodiment are not only film-like objects to be polished, but also various types composed of glass, silicon, SiC, SiGe, Ge, GaN, GaP, GaAs, sapphire, plastic, and the like. It can also be applied to substrates.

The polishing liquid, the polishing liquid set, and the polishing method according to the present embodiment are not only for manufacturing semiconductor elements, but also for image display devices such as TFTs and organic ELs; optical parts such as photomasks, lenses, prisms, optical fibers, and single crystal scintillators Optical elements such as optical switching elements and optical waveguides; light emitting elements such as solid-state lasers and blue laser LEDs; and magnetic storage devices such as magnetic disks and magnetic heads.

Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited to the following examples.

<Preparation of ceria powder>
40 kg of commercially available cerium carbonate hydrate was placed in an alumina container and baked in air at 830 ° C. for 2 hours to obtain 20 kg of yellowish white powder. Phase identification of this powder was performed by X-ray diffraction to confirm that ceria powder was obtained. 20 kg of the obtained ceria powder was dry pulverized using a jet mill to obtain ceria powder containing ceria particles.

<Preparation of polishing liquid for CMP>
After mixing the ceria powder (ceria particles) prepared above and deionized water, the polyols listed in Table 1 or Table 2 (manufactured by Nippon Emulsifier Co., Ltd., trade name: TMP-60, polyoxyethylene trimethylolpropane) ) And hydroxy acid. Then, ultrasonic dispersion is performed while stirring, and CMP containing 0.18% by mass of ceria particles, 0.50% by mass of polyol, and 0.10% by mass of hydroxy acid based on the total mass of the polishing slurry for CMP. A polishing liquid was obtained. The ultrasonic dispersion was performed at an ultrasonic frequency of 400 kHz and a dispersion time of 30 minutes.

(Zeta potential of abrasive grains)
An appropriate amount of a polishing slurry for CMP was put into Delsa Nano C manufactured by Beckman Coulter Co., Ltd., and the measurement was performed twice at 25 ° C. The average value of the displayed zeta potential was obtained as the zeta potential. The results are shown in Tables 1 and 2.

(PH of polishing liquid for CMP)
The pH of the polishing liquid for CMP was evaluated under the following conditions. The results are shown in Tables 1 and 2.
[PH]
Measurement temperature: 25 ° C
Measuring device: manufactured by Toa DKK Corporation, model number PHL-40
Measurement method: Two-point calibration using a standard buffer (phthalate pH buffer, pH: 4.01 (25 ° C.); neutral phosphate pH buffer, pH: 6.86 (25 ° C.)) Thereafter, the electrode was put into a polishing slurry for CMP, and the pH after being stabilized for 2 minutes or more was measured with the measuring device.

<Evaluation of dispersion stability>
As an evaluation of dispersion stability (particle size stability), the particle size change rate was calculated by measuring the particle size (MV: volume average particle size) of ceria particles in the CMP polishing solution before and after storage of the CMP polishing solution. . The particle size change rate was calculated based on the following formula. The CMP polishing liquid immediately after preparation was stored at 25 ° C. for 168 hours. The particle size before and after storage was measured using a laser diffraction / scattering particle size distribution analyzer (trade name: Microtrack MT3300EXII, manufactured by Microtrack Bell Co., Ltd.). The results are shown in Tables 1 and 2.
Change rate of particle size (%) = | particle size after storage (nm) −particle size before storage (nm) | / particle size before storage (nm) × 100

As the polishing evaluation, the polishing rate was calculated by polishing the silicon oxide film under the following conditions using the respective CMP polishing liquids before and after storage, and the rate of change of the polishing rate was calculated. The rate of change of the polishing rate was calculated based on the following formula. The CMP polishing liquid immediately after preparation was stored at 25 ° C. for 168 hours. The results are shown in Tables 1 and 2.
Rate of change in polishing rate (%) = | polishing rate after storage (nm / min) −polishing rate before storage (nm / min) | / polishing rate before storage (nm / min) × 100
[Polishing]
A φ200 mm silicon wafer on which a silicon oxide film was formed was set on a holder to which a suction pad for attaching a substrate was attached in a polishing apparatus (manufactured by APPLIED MATERIALS, product name: Reflexion). A holder was placed on a surface plate with a porous urethane resin pad attached so that the silicon oxide film faces the pad. The substrate was pressed against the pad with a polishing load of 20 kPa while supplying the polishing slurry for CMP onto the pad at a supply rate of 200 mL / min. At this time, polishing was performed by rotating the platen at 78 min ⁻¹ and the holder at 98 min ⁻¹ for 1 min. The polished wafer was thoroughly washed with pure water and dried. The change in film thickness before and after polishing of the silicon oxide film was measured using an optical interference type film thickness measuring device to determine the polishing rate.

As shown in Tables 1 and 2, by using abrasive grains having a positive zeta potential, a specific hydroxy acid, and a polyol in combination, the dispersion stability of the abrasive grains in the polishing liquid containing the polyol is improved. It is confirmed that it can be improved.

Claims

Containing abrasive grains, hydroxy acid, polyol, and liquid medium,
The abrasive grain has a positive zeta potential;
A polishing liquid, wherein the hydroxy acid has one carboxyl group and 1 to 3 hydroxyl groups.
The polishing liquid according to claim 1, wherein the hydroxy acid contains a compound having one carboxyl group and one hydroxyl group.
The polishing liquid according to claim 1 or 2, wherein the hydroxy acid contains a compound having one carboxyl group and two hydroxyl groups.
The polishing liquid according to any one of claims 1 to 3, wherein the polyol contains a polyether polyol.
The polishing liquid according to any one of claims 1 to 4, wherein the hydroxy acid content is 0.01 to 1.0 mass%.
The polishing liquid according to any one of claims 1 to 5, wherein the content of the polyol is 0.05 to 5.0 mass%.
The polishing liquid according to any one of claims 1 to 6, which is used for polishing a surface to be polished containing silicon oxide.
The constituents of the polishing liquid according to any one of claims 1 to 7 are stored separately in a first liquid and a second liquid, and the first liquid contains the abrasive grains, a liquid medium, And the second liquid contains the hydroxy acid, the polyol, and a liquid medium.
A polishing method comprising a step of polishing a surface to be polished using the polishing liquid according to any one of claims 1 to 7.
A polishing method comprising a step of polishing a surface to be polished using a polishing liquid obtained by mixing the first liquid and the second liquid in the polishing liquid set according to claim 8.
A method for polishing a substrate comprising an insulating material and silicon nitride,
A polishing method comprising a step of selectively polishing the insulating material with respect to the silicon nitride using the polishing liquid according to any one of claims 1 to 7.
A method for polishing a substrate comprising an insulating material and silicon nitride,
A step of selectively polishing the insulating material with respect to the silicon nitride using a polishing liquid obtained by mixing the first liquid and the second liquid in the polishing liquid set according to claim 8. A polishing method provided.
A method for polishing a substrate comprising an insulating material and polysilicon,
A polishing method comprising a step of selectively polishing the insulating material with respect to the polysilicon using the polishing liquid according to any one of claims 1 to 7.
A method for polishing a substrate comprising an insulating material and polysilicon,
A step of selectively polishing the insulating material with respect to the polysilicon using a polishing liquid obtained by mixing the first liquid and the second liquid in the polishing liquid set according to claim 8. A polishing method provided.