JP7209583B2 - Polishing liquid composition for silicon oxide film - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to a polishing liquid composition for silicon oxide films containing cerium oxide particles, a method for manufacturing a semiconductor substrate using the same, and a method for polishing a substrate.

A chemical mechanical polishing (CMP) technique is a technique in which the surface of a substrate to be polished and a polishing pad are brought into contact with each other, and a polishing liquid is supplied to the contact area between the substrate and the polishing pad. This is a technique for chemically reacting uneven portions on the surface of the substrate to be polished and mechanically removing and flattening the substrate by moving the substrate.

At present, when planarizing an interlayer insulating film, forming a shallow trench element isolation structure (hereinafter also referred to as an "element isolation structure"), forming plugs and embedded metal wiring, etc., in the manufacturing process of semiconductor devices, this CMP technology has become an essential technology. 2. Description of the Related Art In recent years, the number of layers of semiconductor elements and the increase in definition thereof have progressed dramatically, and there has been a demand for further improvement in the yield and throughput of semiconductor elements. Accordingly, in the CMP process as well, scratch-free polishing at a higher speed has been desired.

For example, Patent Document 1 describes a polishing liquid for CMP having a pH of about 1 to 6, comprising wet ceria particles, a functionalized heterocycle such as a functionalized nitrogen-containing heterocycle, a cationic polymer, a pH adjuster, and an aqueous carrier. A composition is proposed.
Patent Document 2 proposes a polishing liquid composition for CMP containing an abrasive, an amino compound, a radical-generating oxidizing agent, a radical scavenger, and an aqueous carrier. Examples of radical scavengers include hydroxyl-substituted heterocyclic aromatic compounds such as 2-hydroxypyridine and N-oxide compounds such as 1-(2-hydroxymethyl)piperazine-N-oxide (id. claim 2, paragraphs [0032], [0034], etc.).

Japanese Patent Publication No. 2018-513229 JP 2015-195391 A

2. Description of the Related Art In recent years, the field of semiconductors has progressed toward higher integration, and wiring has been required to become more complicated and finer. Therefore, in CMP polishing, the grain size of abrasive grains is reduced to reduce defects.
Furthermore, when polishing a concavo-convex pattern formed on a substrate, there is a problem that the polishing speed varies depending on the size (line width) of the convex portions, and the polishing speed of the convex portions largely depends on the line width. For example, when polishing a concave-convex pattern of a silicon oxide film 2 formed on a substrate 1 as shown in FIG. 1A, as shown in FIG. The convex portion of the region S1 with a small line width is preferentially polished, resulting in a poor finished flatness. Therefore, there is a demand for a polishing composition that has a small line width dependence of the polishing rate for convex portions and that can uniformly planarize all patterns.

Accordingly, the present disclosure provides a polishing liquid composition for a silicon oxide film that reduces the line width dependence of the polishing speed in an uneven pattern and is excellent in improving the polishing speed of a silicon oxide film, a method for manufacturing a semiconductor substrate using the same, and a method for polishing a semiconductor substrate. I will provide a.

The present disclosure, in one aspect, contains cerium oxide particles (component A), a water-soluble polymer (component B), an N-oxide compound (component C), and an aqueous medium, wherein component B comprises a first Containing a structural unit b1 containing at least one group selected from a class amino group, a secondary amino group, a tertiary amino group, a quaternary ammonium group, and salts thereof, and a nonionic structural unit b2 It is a water-soluble polymer, and component C is an N-oxide compound or a salt thereof containing a nitrogen-containing heteroaromatic ring skeleton in which at least one hydrogen atom is substituted with a hydroxyl group. .

The present disclosure, in another aspect, relates to a method for manufacturing a semiconductor substrate, including the step of polishing a film-to-be-polished using the polishing composition of the present disclosure.

The present disclosure, in another aspect, relates to a polishing method including the step of polishing a film-to-be-polished using the polishing composition of the present disclosure.

According to one aspect of the present disclosure, it is possible to provide a polishing liquid composition for a silicon oxide film that reduces the line width dependence of the polishing speed in an uneven pattern and is excellent in improving the polishing speed of a silicon oxide film.

FIG. 1 is a cross-sectional view showing an example of a process of polishing a concave-convex pattern of a silicon oxide film (2) formed on a substrate (1).

As a result of extensive studies by the present inventors, it was found that a specific water-soluble polymer and a specific N-oxide compound are added to a polishing liquid composition using cerium oxide (hereinafter also referred to as "ceria") particles as abrasive grains. This is based on the knowledge that the dependence of the polishing speed on the uneven pattern on the line width can be reduced, and the polishing speed for the silicon oxide film can be improved.

In one or more embodiments, the present disclosure contains cerium oxide particles (component A), a water-soluble polymer (component B), an N-oxide compound (component C), and an aqueous medium, and component B is a structural unit b1 containing at least one group selected from a primary amino group, a secondary amino group, a tertiary amino group, a quaternary ammonium group, and salts thereof, and a nonionic structural unit b2, and component C is an N-oxide compound or a salt thereof containing a nitrogen-containing heteroaromatic ring skeleton in which at least one hydrogen atom is substituted with a hydroxyl group. The present invention relates to a liquid composition (hereinafter also referred to as "polishing liquid composition of the present disclosure"). According to the polishing liquid composition of the present disclosure, it is possible to reduce the line width dependence of the polishing speed in the uneven pattern and improve the polishing speed of the silicon oxide film.

Although the details of the mechanism by which the effects of the present disclosure are manifested are not clear, it is speculated as follows.
Ceria particles are generally used for polishing a silicon oxide film. Normally, cerium in ceria particles is tetravalent, and in rare cases oxygen (O) is dropped to become trivalent. It is believed that the trivalent cerium in the ceria particles weakens the Si—O bond of the silicon oxide film, weakens the silicon oxide film, and promotes polishing.
In the present disclosure, by using ceria particles (component A) and a specific N-oxide compound (component C) in combination, the hydroxyl groups of component C convert tetravalent cerium present on the surface of the ceria particles to trivalent cerium. , and the ratio of trivalent cerium present in the ceria particles increases, which promotes the action of the silicon oxide film on the Si—O bonds, furthers the weakening of the silicon oxide film, and improves the polishing speed. It is thought that
Furthermore, in the present disclosure, a specific water-soluble polymer (component B) adsorbs to both the silicon oxide film and the cerium oxide particles, functions as a binder for the silicon oxide film and the cerium oxide, and is independent of the line width of the uneven pattern. , the polishing progresses uniformly, and the dependence of the polishing rate on the line width can be reduced.
However, the present disclosure need not be construed as being limited to these mechanisms.

[Cerium oxide (ceria) particles (component A)]
The polishing composition of the present disclosure contains ceria particles (hereinafter also simply referred to as “component A”) as abrasive grains. Component A may be of one type or a combination of two or more types.

The manufacturing method, shape, and surface state of Component A are not particularly limited. Examples of component A include colloidal ceria, amorphous ceria, and ceria-coated silica.
Colloidal ceria can be obtained by a build-up process, for example, by the method described in Examples 1 to 4 of JP-A-2010-505735.
Examples of amorphous ceria include pulverized ceria. An embodiment of the pulverized ceria includes, for example, calcined and pulverized ceria obtained by calcining and pulverizing a cerium compound such as cerium carbonate or cerium nitrate. Other embodiments of ground ceria include, for example, single crystal ground ceria obtained by wet grinding ceria particles in the presence of an inorganic acid or an organic acid. Examples of inorganic acids used for wet pulverization include nitric acid, and examples of organic acids include organic acids having a carboxyl group, specifically picolinic acid, glutamic acid, aspartic acid, and aminobenzoic acid. and p-hydroxybenzoic acid. Examples of wet pulverization methods include wet pulverization using a planetary bead mill or the like.
As ceria-coated silica, for example, at least a part of the silica particle surface is granular by the method described in Examples 1 to 14 of JP-A-2015-63451 or Examples 1-4 of JP-A-2013-119131. Composite particles having a structure coated with ceria can be mentioned, and the composite particles can be obtained, for example, by depositing ceria on silica particles.

Examples of the shape of component A include substantially spherical, polyhedral, and raspberry-like.

The average primary particle size of component A is preferably 5 nm or more, more preferably 10 nm or more, and even more preferably 20 nm or more, from the viewpoint of improving the polishing rate, and is preferably 300 nm or less, and 200 nm or more from the viewpoint of suppressing the occurrence of polishing scratches. The following are more preferable, and 150 nm or less is even more preferable. More specifically, the average primary particle size of component A is preferably 5 nm or more and 300 nm or less, more preferably 10 nm or more and 200 nm or less, and even more preferably 20 nm or more and 150 nm or less. In the present disclosure, the average primary particle size of component A is calculated using the BET specific surface area S (m ² /g) calculated by the BET (nitrogen adsorption) method. The BET specific surface area can be measured by the method described in Examples.

The content of component A in the polishing composition of the present disclosure is 0.001% by mass or more from the viewpoint of improving the polishing rate, assuming that the total content of component A, component B, component C, and water is 100% by mass. is preferably 0.05% by mass or more, more preferably 0.07% by mass or more, further preferably 0.1% by mass or more, and from the viewpoint of suppressing the occurrence of polishing scratches, preferably 6% by mass or less, 1 mass % or less is more preferable, 0.7 mass % or less is still more preferable, and 0.5 mass % or less is still more preferable. More specifically, the content of component A is preferably 0.001% by mass or more and 6% by mass or less, more preferably 0.05% by mass or more and 1% by mass or less, and 0.07% by mass or more and 0.7% by mass. % or less, and more preferably 0.1 mass % or more and 0.5 mass % or less. When component A is a combination of two or more, the content of component A refers to their total content.

[Water-soluble polymer (component B)]
Component B contained in the polishing composition of the present disclosure contains at least one group selected from primary amino groups, secondary amino groups, tertiary amino groups, quaternary ammonium groups, and salts thereof. It is a water-soluble polymer containing a structural unit (hereinafter also referred to as "structural unit b1") containing a nonionic structural unit (hereinafter also referred to as "structural unit b2"). Component B may be used singly or in combination of two or more. In the present disclosure, “water-soluble” means having a solubility of 0.5 g/100 mL or more, preferably 2 g/100 mL or more, in water (20° C.).

Structural unit b1 is a structural unit containing at least one group selected from primary amino groups, secondary amino groups, tertiary amino groups, quaternary ammonium groups, and salts thereof, From the viewpoint of improvement and reduction of line width dependence, an amine compound having two allyl groups or a salt thereof is preferable, and a diallylalkylammonium salt is more preferable. Examples of salts include hydrochlorides, hydrobromides, acetates, sulfates, nitrates, sulfites, phosphates, amidosulfates, and methanesulfonates. Hydrochloride is preferred from the viewpoint of reduction of line width dependence. A specific example of the structural unit b1 is a structural unit derived from diallyldimethylammonium chloride.

Structural unit b2 is a nonionic structural unit. In the present disclosure, a nonionic structural unit refers to a structural unit that does not ionize in an aqueous solution. In one or a plurality of embodiments, the structural unit b2 is preferably a structural unit derived from an acrylamide compound, from the viewpoint of improving the polishing speed and reducing the line width dependence, such as acrylamide, N-methylacrylamide, N-(hydroxymethyl ) At least one acrylamide compound selected from acrylamide, N,N-dimethylacrylamide, N-ethylacrylamide, N,N-diethylacrylamide, N-(isopropyl)acrylamide, hydroxyethylacrylamide, dimethylaminopropylacrylamide, and acryloylmorpholine Structural units derived from acrylamide are more preferable, and structural units derived from acrylamide are still more preferable.

Component B is preferably a copolymer of diallylalkylammonium salt and acrylamide from the viewpoint of improving the polishing rate and reducing the line width dependence. A specific example of the copolymer of diallylalkylammonium salt and acrylamide is a copolymer of diallyldimethylammonium chloride and acrylamide.

The total content of structural unit b1 and structural unit b2 in all structural units of component B is preferably 90 to 100 mol %, more preferably 95 to 100 mol %, from the viewpoint of improving polishing rate and reducing line width dependence. is more preferred, and 99 to 100 mol % is even more preferred.

The molar ratio (a/b) of the structural unit a to the structural unit b in all the structural units of the component B is 90/10 to 10/, from the viewpoint of improving the polishing rate and reducing the line width dependence. 90 is preferred, 85/15 to 20/80 is more preferred, 80/20 to 30/70 is even more preferred, and 70/30 to 40/60 is even more preferred.

Component B may further have structural units other than structural units b1 and b2. Other structural units include structural units derived from ethylenically unsaturated sulfonic acid compounds, structural units derived from ethylenically unsaturated carboxylic acid compounds, structural units derived from ethylenically unsaturated phosphoric acid compounds, and hydrophobic unsaturated groups such as styrene. A saturated monomer etc. are mentioned.

The weight average molecular weight of component B is preferably 1,000 or more, more preferably 5,000 or more, still more preferably 10,000 or more, from the viewpoint of improving the polishing rate and reducing the line width dependence, and 3,000,000 or less is preferable, 2,000,000 or less is more preferable, and 1,000,000 or less is still more preferable. More specifically, the weight average molecular weight of component B is preferably 1,000 or more and 3,000,000 or less, more preferably 5,000 or more and 2,000,000 or less, and 10,000 or more and 1,000,000. More preferred are: The weight average molecular weight of component B can be measured using, for example, gel permeation chromatography (GPC).

The content of component B in the polishing composition of the present disclosure is such that the total content of component A, component B, component C, and the aqueous medium is 100% by mass, from the viewpoint of improving the polishing rate and line width dependence. From the viewpoint of minimizing the , 1% by mass or less is preferable, 0.5% by mass or less is more preferable, 0.3% by mass or less is still more preferable, and 0.1% by mass or less is even more preferable. More specifically, the content of Component B is preferably 0.0005% by mass or more and 1% by mass or less, more preferably 0.001% by mass or more and 0.5% by mass or less, and 0.002% by mass or more and 0.5% by mass or less. 3% by mass or less is more preferable, and 0.005% by mass or more and 0.1% by mass or less is even more preferable. When component B is a combination of two or more, the content of component B refers to the total content thereof.

[N-oxide compound (component C)]
Component C contained in the polishing composition of the present disclosure is an N-oxide compound or a salt thereof containing a nitrogen-containing heteroaromatic ring skeleton in which at least one hydrogen atom is substituted with a hydroxyl group. Examples of the above salts include alkali metal salts, alkaline earth metal salts, organic amine salts, ammonium salts and the like. Component C may be used singly or in combination of two or more.

In the present disclosure, an N-oxide compound refers, in one or more embodiments, to a compound having an N-oxide group (N→O group). The N-oxide compound can have one or more N→O groups, and one N→O group is preferred from the standpoint of availability.

In the present disclosure, at least one nitrogen atom contained in the nitrogen-containing heteroaromatic skeleton forms an N-oxide. In one or more embodiments, the nitrogen-containing heteroaromatic ring contained in Component C includes a monocyclic or bicyclic condensed ring. In one or more embodiments, the number of nitrogen atoms in the nitrogen-containing heteroaromatic ring contained in component C is 1 to 3, and from the viewpoint of improving the polishing rate and reducing the line width dependence, Alternatively, two are preferred, and one is more preferred.
The nitrogen-containing heteroaromatic ring skeleton contained in component C, in one or more embodiments, includes at least one selected from pyridine N-oxide skeleton, quinoline N-oxide skeleton, and the like. In the present disclosure, the pyridine N-oxide skeleton indicates a structure in which the nitrogen atoms contained in the pyridine ring form an N-oxide. A quinoline N-oxide and skeleton indicates a configuration in which a nitrogen atom contained in the quinoline ring forms an N-oxide.

Component C, in one or more embodiments, is an N-oxide compound having a pyridine ring in which at least one hydrogen atom is substituted with a hydroxy group, and a quinoline ring in which at least one hydrogen atom is substituted with a hydroxy group. At least one selected from N-oxide compounds and salts thereof. Among these, an N-oxide compound having a pyridine ring in which at least one hydrogen atom is substituted with a hydroxy group or a salt thereof is preferable as component C from the viewpoint of improving the polishing rate and reducing the line width dependence. .

Specific examples of component C include 2-hydroxypyridine N-oxide, 3-hydroxypyridine N-oxide, 8-hydroxyquinoline N-oxide and the like.

The content of component C in the polishing composition of the present disclosure is such that the total content of component A, component B, component C, and the aqueous medium is 100% by mass, from the viewpoint of improving the polishing rate and line width dependence. From the viewpoint of reducing the , 1% by mass or less is preferable, 0.5% by mass or less is more preferable, 0.3% by mass or less is still more preferable, and 0.1% by mass or less is even more preferable. More specifically, the content of Component B is preferably 0.0005% by mass or more and 1% by mass or less, more preferably 0.001% by mass or more and 0.5% by mass or less, and 0.002% by mass or more and 0.5% by mass or less. 3% by mass or less is more preferable, and 0.005% by mass or more and 0.1% by mass or less is even more preferable. When component C is a combination of two or more, the content of component C refers to the total content thereof.

The mass ratio B/C (content of component B/content of component C) of component B and component C in the polishing composition of the present disclosure is, from the viewpoint of improving the polishing rate and reducing line width dependence, 0.01 or more is preferable, 0.05 or more is more preferable, 0.1 or more is more preferable, 0.5 or more is still more preferable, and 100 or less is preferable, 20 or less is more preferable, and 10 or less is more preferable, 5 or less is more preferable. More specifically, the mass ratio B/C is preferably 0.01 or more and 100 or less, more preferably 0.05 or more and 20 or less, still more preferably 0.1 or more and 10 or less, and further preferably 0.5 or more and 5 or less. preferable.

[Aqueous medium]
The aqueous medium contained in the polishing composition of the present disclosure includes water such as distilled water, ion-exchanged water, pure water and ultrapure water, or a mixed solvent of water and a solvent. Examples of the solvent include water-miscible solvents (for example, alcohol such as ethanol). When the aqueous medium is a mixed solvent of water and a solvent, the ratio of water to the entire mixed medium may not be particularly limited as long as the effects of the present disclosure are not hindered. , is preferably 95% by mass or more, more preferably 98% by mass or more, and even more preferably substantially 100% by mass. From the viewpoint of surface cleanliness of the substrate to be polished, the aqueous medium is preferably water, more preferably ion-exchanged water or ultrapure water, and still more preferably ultrapure water. The content of the aqueous medium in the polishing composition of the present disclosure can be the remainder after removing component A, component B, component C, and optional components described later that are blended as necessary.

[Optional component]
The polishing liquid composition of the present disclosure contains a pH adjuster, a water-soluble polymer other than component B, a surfactant, a thickener, a dispersant, a rust inhibitor, an antiseptic, a basic substance, a polishing rate improver, a nitriding agent, Optional components such as silicon film polishing inhibitors and polysilicon film polishing inhibitors can be further contained. When the polishing liquid composition of the present disclosure further contains optional components, the content of the optional components in the polishing liquid composition of the present disclosure is 0.5 to 0.5 from the viewpoint of improving the polishing speed and reducing the line width dependence. 001% by mass or more, more preferably 0.0025% by mass or more, still more preferably 0.01% by mass or more, and preferably 1% by mass or less, more preferably 0.5% by mass or less, and 0.1% by mass % or less is more preferable. More specifically, the content of the optional component is preferably 0.001% by mass or more and 1% by mass or less, more preferably 0.0025% by mass or more and 0.5% by mass or less, and 0.01% by mass or more and 0.5% by mass or less. 1% by mass or less is more preferable.

[Polishing liquid composition]
The polishing composition of the present disclosure can be produced, for example, by a production method including a step of blending Component A, Component B, Component C, an aqueous medium, and optionally the optional components described above by a known method. For example, the polishing composition of the present disclosure can be made by blending at least component A, component B, component C and an aqueous medium. When component A is a combination of multiple types of ceria particles, component A can be obtained by blending multiple types of ceria particles. When component B is a combination of multiple types of water-soluble polymers, component B can be obtained by blending multiple types of water-soluble polymers. When Component C is a combination of multiple types of N-oxide compounds, Component C can be obtained by blending multiple types of N-oxide compounds. In the present disclosure, "blending" includes mixing component A, component B, component C, an aqueous medium, and optionally the optional components described above simultaneously or in order. The order of mixing is not particularly limited. The blending can be performed using a mixer such as a homomixer, a homogenizer, an ultrasonic disperser, and a wet ball mill. The blending amount of each component in the method for producing the polishing composition of the present disclosure can be the same as the content of each component in the polishing composition of the present disclosure described above.

Embodiments of the polishing composition of the present disclosure may be a so-called one-component type in which all components are premixed and supplied to the market, or a so-called two-component type in which they are mixed at the time of use. There may be. An embodiment of a two-part type polishing composition comprises a first liquid containing a component A and a second liquid containing a component B and a component C. When used, the first liquid and the second liquid are mixed. Those that are mixed are included. The first liquid and the second liquid may be mixed before being supplied to the surface to be polished, or they may be separately supplied and mixed on the surface of the substrate to be polished. The first liquid and the second liquid can each contain the optional components described above as necessary.

From the viewpoint of improving the polishing rate, the pH of the polishing composition of the present disclosure is preferably 3.5 or higher, more preferably 4 or higher, still more preferably 4.5 or higher, and preferably 9 or lower, and 8.5 or lower. is more preferred, and 8 or less is even more preferred. More specifically, the pH is preferably 3.5 or more and 9 or less, more preferably 4 or more and 8.5 or less, and even more preferably 4.5 or more and 8 or less. In the present disclosure, the pH of the polishing composition is a value at 25° C. and can be measured using a pH meter, specifically by the method described in Examples.

In the present disclosure, "the content of each component in the polishing composition" refers to the content of each component at the time of polishing, that is, when the polishing composition is started to be used for polishing. The polishing composition of the present disclosure may be stored and supplied in a concentrated state to the extent that its stability is not impaired. In this case, it is preferable in that manufacturing and transportation costs can be reduced. This concentrated solution can be diluted with water as necessary and used in the polishing process. The dilution ratio is preferably 5 to 100 times.

[Film to be Polished]
Examples of films to be polished that are polished using the polishing composition of the present disclosure include silicon oxide films. Therefore, the polishing composition of the present disclosure can be used in processes requiring polishing of silicon oxide films. In one or more embodiments, the polishing composition of the present disclosure is used to polish a silicon oxide film in the step of forming an element isolation structure of a semiconductor substrate, and polish a silicon oxide film in the step of forming an interlayer insulating film. It can be suitably used for polishing a silicon oxide film in a process of forming an embedded metal wiring, or polishing a silicon oxide film in a process of forming an embedded capacitor. In one or more other embodiments, the polishing composition of the present disclosure can be suitably used for manufacturing a three-dimensional semiconductor device such as a three-dimensional NAND flash memory.

[Polishing liquid kit]
In another aspect, the present disclosure relates to a kit for producing the polishing composition of the present disclosure (hereinafter also referred to as "polishing liquid kit of the present disclosure").
As an embodiment of the polishing liquid kit of the present disclosure, for example, a polishing kit containing an abrasive dispersion containing component A and an aqueous medium and an additive aqueous solution containing component B and component C in a state in which they are not mixed with each other Liquid kits (two-component polishing liquid compositions) can be mentioned. The abrasive dispersion and the additive aqueous solution are mixed at the time of use, and diluted with an aqueous medium if necessary. The aqueous medium contained in the abrasive dispersion may be the total amount of water used to prepare the polishing composition, or may be a part thereof. The aqueous additive solution may contain a part of the aqueous medium used for preparing the polishing composition. The abrasive dispersion and the additive aqueous solution may each contain the optional components described above, if necessary.
According to the polishing liquid kit of the present disclosure, it is possible to obtain a polishing liquid composition capable of reducing the line width dependence of the polishing rate in the uneven pattern and improving the polishing rate of the silicon oxide film.

[Method for manufacturing semiconductor substrate]
In one aspect of the present disclosure, a semiconductor substrate comprising a step of polishing a silicon oxide film using a polishing composition of the present disclosure (hereinafter also referred to as a “polishing step using the polishing composition of the present disclosure”). (hereinafter also referred to as “method for manufacturing a semiconductor substrate of the present disclosure”). According to the method for manufacturing a semiconductor substrate of the present disclosure, it is possible to reduce the line width dependence of the polishing speed in the concave-convex pattern and improve the polishing speed of the silicon oxide film, so that it is possible to efficiently manufacture a semiconductor substrate with improved quality. effect can be achieved.

As a specific example of the method for manufacturing a semiconductor substrate of the present disclosure, first, a silicon substrate is exposed to oxygen in an oxidation furnace to grow a silicon dioxide layer on its surface, and then a silicon nitride (Si A polishing stopper film such as a ₃ N ₄ ) film or a polysilicon film is formed by, for example, a CVD method (chemical vapor deposition method). Next, a substrate including a silicon substrate and a polishing stopper film disposed on one main surface side of the silicon substrate, for example, a substrate having a polishing stopper film formed on a silicon dioxide layer of a silicon substrate is subjected to a photolithographic technique. is used to form trenches. Next, a silicon oxide (SiO ₂ ) film, which is a film to be polished for embedding trenches, is formed by, for example, a CVD method using silane gas and oxygen gas, and the polishing stopper film is covered with the film to be polished (silicon oxide film). A substrate to be polished is obtained. By forming the silicon oxide film, the trench is filled with the silicon oxide of the silicon oxide film, and the surface of the polishing stopper film opposite to the silicon substrate side is covered with the silicon oxide film. The surface of the silicon oxide film thus formed opposite to the surface facing the silicon substrate has steps formed corresponding to the unevenness of the lower layer. Next, the silicon oxide film is polished by a CMP method until at least the surface of the polishing stopper film opposite to the silicon substrate side is exposed, and more preferably, the surface of the silicon oxide film and the surface of the polishing stopper film are flush with each other. Polish the silicon oxide film until it becomes The polishing liquid composition of the present disclosure can be used in this step of polishing by the CMP method. The width of the protrusion formed corresponding to the unevenness of the lower layer of the silicon oxide film is, for example, 0.5 μm or more and 5000 μm or less, and the width of the recess is, for example, 0.5 μm or more and 5000 μm or less.

In the CMP method, while the surface of the substrate to be polished and the polishing pad are in contact with each other, the substrate to be polished and the polishing pad are relatively moved while supplying the polishing liquid composition of the present disclosure to the contact area. As a result, uneven portions on the surface of the substrate to be polished are flattened.
In the method of manufacturing a semiconductor substrate according to the present disclosure, another insulating film may be formed between the silicon dioxide layer of the silicon substrate and the polishing stopper film. Another insulating film may be formed between the polishing stopper film (for example, silicon nitride film).

In the polishing step using the polishing composition of the present disclosure, the rotational speed of the polishing pad is, for example, 30 to 200 rpm/min, and the rotational speed of the substrate to be polished is, for example, 30 to 200 rpm/min. The polishing load set in the polishing apparatus can be set to, for example, 20 to 500 gf/cm ² , and the supply rate of the polishing liquid composition can be set to, for example, 10 to 500 mL/min or less. When the polishing liquid composition is a two-component polishing liquid composition, the respective polishing speeds of the film-to-be-polished and the polishing stopper film can be adjusted by adjusting the supply speed (or supply amount) of each of the first and second liquids. Also, the polishing rate ratio (polishing selectivity) between the film to be polished and the polishing stopper film can be adjusted.

In the polishing step using the polishing composition of the present disclosure, the polishing rate of the film to be polished (silicon oxide film) is preferably 50 nm/min or more, more preferably 80 nm/min or more, and 90 nm from the viewpoint of improving productivity. / minute or more is more preferable.

[Polishing method]
In one aspect, the present disclosure relates to a polishing method (hereinafter also referred to as the polishing method of the present disclosure), which includes polishing a film-to-be-polished using the polishing composition of the present disclosure. By using the polishing method of the present disclosure, it is possible to improve the polishing speed of the silicon oxide film, so that it is possible to improve the productivity of semiconductor substrates with improved quality. The specific polishing method and conditions can be the same as those of the semiconductor substrate manufacturing method of the present disclosure described above.

1. Preparation of polishing composition (Examples 1 to 8, Comparative Examples 1 to 2 and Reference Example 3)
Ceria particles (Component A), water-soluble polymer (Component B or non-Component B), N-oxide compound (Component C) and water were mixed to obtain Examples 1 to 8, Comparative Examples 1 to 2 and Reference Example 3. A polishing liquid composition was obtained. The contents of components A to C in the polishing liquid composition (% by mass, active ingredients) are as shown in Table 1, respectively, and the contents of water are is the remainder excluding . pH adjustments were performed using ammonia or nitric acid.

Component A, component B, non-component B, and component C used in the preparation of the polishing composition are shown below.
(Component A)
Ground ceria [average primary particle size: 26.9 nm, BET specific surface area: 30.8 m ² /g]
(Component B)
B1: Acrylamide-diallyldimethylammonium chloride copolymer [Unisense FCA1000L: manufactured by Senka Co., Ltd.]
(Non-component B)
B2: Polydimethylammonium chloride [Unisense FCA100L: manufactured by Senka Co., Ltd.]
(Component C)
C1: 2-hydroxypyridine N-oxide [manufactured by Tokyo Chemical Industry Co., Ltd.]
C2: 3-hydroxypyridine N-oxide [manufactured by Tokyo Chemical Industry Co., Ltd.]

2. Measurement method of each parameter (1) pH of polishing composition
The pH value of the polishing composition at 25° C. is a value measured using a pH meter (“HM-30G” manufactured by Toa Denpa Kogyo Co., Ltd.). It is the number after minutes. Table 1 shows the results.

( ² ) Average Primary Particle Size of Ceria Particles (Component A) was used, and the true density of the ceria particles was calculated as 7.2 g/cm ³ .

(3) BET Specific Surface Area of Ceria Particles (Component A) The specific surface area was obtained by drying a ceria dispersion liquid with hot air at 120° C. for 3 hours and then pulverizing it finely with an agate mortar. After drying for 15 minutes in an atmosphere of 120 ° C. immediately before the measurement, it was measured by the nitrogen adsorption method (BET method) using a specific surface area measuring device (Micromeritic automatic specific surface area measuring device "Flowsorb III 2305", manufactured by Shimadzu Corporation). .

3. Evaluation of polishing liquid compositions (Examples 1 to 8, Comparative Examples 1 to 2 and Reference Example 3) [evaluation samples]
As a sample for evaluation, a commercially available wafer for CMP characteristics evaluation (“T-TEOS MIT864 PT wafer” manufactured by Advantec, diameter 200 mm) was prepared and cut into 40 mm×40 mm. In this evaluation sample, a silicon nitride film with a thickness of 150 nm as a first layer and a silicon oxide film with a thickness of 450 nm as a second layer are arranged as convex portions on a silicon substrate, and concave portions are also formed with a thickness of 450 nm. A silicon oxide film is disposed, and a linear concave-convex pattern is formed by etching such that the step between the convex portion and the concave portion is 350 nm. The silicon oxide film is made of P-TEOS, and the projections and recesses each having a line width of 25 μm (pattern a) and 500 μm (pattern b) were used as measurement targets.

[Polishing conditions]
Polishing device: Single-sided polishing machine [Technorise "TR15M-TRK1", surface plate diameter 380 mm]
Polishing pad: Hard urethane pad ["IC-1000/Suba400" manufactured by Nitta Haas]
Surface plate rotation speed: 90 rpm
Head rotation speed: 90rpm
Polishing load: 300g weight/cm ²
Amount of polishing liquid supplied: 50 mL/min Polishing time: 1 minute

[Polishing speed and polishing speed ratio]
Using each of the polishing liquid compositions of Examples 1 to 8, Comparative Examples 1 and 2, and Reference Example 3, patterned substrates were polished under the above polishing conditions. After polishing, the sample was washed with ultrapure water and dried, and the test piece was used as an object to be measured by an optical interference type film thickness measuring device described later.
Before and after polishing, the film thickness of the silicon oxide film was measured using an optical interference film thickness measuring device (“VM-1230” manufactured by SCREEN Semiconductor Solutions Co., Ltd.). The polishing rate of the silicon oxide film was calculated by the following formula. Further, the ratio of the polishing speed of pattern b to the polishing speed of pattern a (polishing speed ratio b/a) was calculated. These calculation results are shown in Table 1.
Polishing rate of silicon oxide film (nm/min)
= [silicon oxide film thickness before polishing (nm) - silicon oxide film thickness after polishing (nm)]/polishing time (minutes)

As shown in Table 1, Examples 1 to 8 in which component B and component C were used in combination compared to Comparative Examples 1 to 2 and Reference Example 3 in which component B and/or component C were not used, the oxidation of pattern a The polishing speed of the silicon film was improved. Moreover, in Examples 1 to 8, compared with Comparative Example 1 and Reference Example 3, the polishing rate of the silicon oxide film of pattern b was improved. Furthermore, since the values of the polishing rate ratio b/a of Examples 1 to 8 are closer to 1 than those of Comparative Examples 1 to 2 and Reference Example 3, the polishing liquid compositions of Examples 1 to 8 are line width dependent. was found to be decreasing.

The polishing composition of the present disclosure is useful in methods of manufacturing semiconductor substrates for high density or high integration.

1 substrate 2 silicon oxide film

Claims (8)

Containing cerium oxide particles (component A), a water-soluble polymer (component B), an N-oxide compound (component C), and an aqueous medium,
Component B comprises a structural unit b1 containing at least one group selected from a primary amino group, a secondary amino group, a tertiary amino group, a quaternary ammonium group, and salts thereof, and a nonionic A water-soluble polymer containing a structural unit b2,
Component C is a polishing liquid composition for silicon oxide films, which is an N-oxide compound or a salt thereof containing a nitrogen-containing heteroaromatic ring skeleton in which at least one hydrogen atom is substituted with a hydroxyl group. 2. The polishing composition according to claim 1, wherein component B is a copolymer of diallylalkylammonium salt and acrylamide. Component C is an N-oxide compound having a pyridine ring in which at least one hydrogen atom is substituted by a hydroxyl group, an N-oxide compound having a quinoline ring in which at least one hydrogen atom is substituted by a hydroxyl group, and salts thereof 3. The polishing composition according to claim 1, which is at least one selected from. 4. The polishing composition according to any one of claims 1 to 3, wherein the content of component B is 0.0005% by mass or more and 1% by mass or less. 5. The polishing composition according to any one of claims 1 to 4, wherein the content of component C is 0.0005% by mass or more and 1% by mass or less. The polishing composition according to any one of claims 1 to 5, wherein the content of component A is 0.001% by mass or more and 6% by mass or less. A method for manufacturing a semiconductor substrate, comprising the step of polishing a film-to-be-polished using the polishing composition according to any one of claims 1 to 6. A polishing method comprising the step of polishing a film-to-be-polished using the polishing composition according to any one of claims 1 to 6.

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