JP7569717B2 - Polishing liquid composition for silicon oxide film - Google Patents

Description

This disclosure relates to a polishing composition for silicon oxide films that contains cerium oxide particles, a method for manufacturing semiconductor substrates using the same, and a method for polishing substrates.

Chemical mechanical polishing (CMP) is a technique in which the surface of the substrate to be polished is brought into contact with a polishing pad, and a polishing liquid is supplied to the contact area while the substrate and polishing pad are moved relative to each other, chemically reacting with the uneven surface of the substrate to be polished and mechanically removing and flattening it.

Currently, CMP technology has become essential in the manufacturing process of semiconductor devices when performing operations such as planarizing interlayer insulating films, forming shallow trench isolation structures, and forming plugs and buried metal wiring. In recent years, semiconductor devices have become increasingly multi-layered and highly precise, and there is a demand for further improvements in the yield and throughput of semiconductor devices. Accordingly, there is a demand for scratch-free and faster polishing in the CMP process.

For example, Patent Document 1 discloses that the use of ceria particles having primary and secondary particle sizes and density within specific ranges achieves both a good polishing rate and a good surface finish.
Patent Document 2 discloses that the removal rate and the in-plane uniformity can be improved by mixing two types of abrasive particles in specific ranges and further containing functionalized pyridine, benzoic acid, or amino acid.

Special Publication No. 2011-545995 Special table 2016-538359 publication

In recent years, the semiconductor industry has become highly integrated, and there is a demand for more complex and finer wiring. For this reason, in CMP polishing, the grain size of the abrasive is reduced to reduce defects, but this causes a problem of a slower polishing speed, and there is a demand for an improvement in the polishing speed of silicon oxide films.

Therefore, the present disclosure provides a polishing composition for silicon oxide films that can improve the polishing speed of silicon oxide films, a method for polishing substrates using the same, and a method for manufacturing semiconductor substrates.

In one aspect, the present disclosure relates to a polishing liquid composition for silicon oxide films, which contains cerium oxide particles and an aqueous medium, the cerium oxide particles including cerium oxide particles (component A) having an average particle size of 15 nm or more and 50 nm or less and a density of 8 g/cm3 or ^more , and cerium oxide particles (component B) having an average particle size of 60 nm or more and 1 μm or less, a pH of 3 or more and 9 or less, and a D50/D99 value of 0.32 or less, where D50 and D99 are the particle sizes at which the cumulative frequency from the small particle size side is 50% and 99%, respectively, in a particle size distribution on a weight basis obtained by centrifugal sedimentation of a mixture of components A and B.

In another aspect, the present disclosure relates to a polishing method that includes a step of polishing a film to be polished using the polishing composition of the present disclosure, the film to be polished being a silicon oxide film formed during the manufacturing process of a semiconductor substrate.

In another aspect, the present disclosure relates to a method for manufacturing a semiconductor substrate, comprising a step of polishing a film to be polished using the polishing composition of the present disclosure.

According to one aspect of the present disclosure, a polishing composition for silicon oxide films that can improve the polishing speed of silicon oxide films can be provided.

In one aspect, the present disclosure is based on the finding that in a polishing composition containing cerium oxide (hereinafter also referred to as "ceria") particles as abrasive grains, small-diameter ceria with high density can contribute to improving the polishing rate by being mixed with large-diameter ceria under specified conditions.

Although the details of the mechanism by which the effects of the present disclosure are manifested are not clear, it is presumed as follows.
Ceria particles are generally used for polishing silicon oxide films. Usually, the cerium in the ceria particles is tetravalent, but occasionally an oxygen atom is lost to make it trivalent. It is believed that the trivalent cerium in the ceria particles weakens the Si-O bond in the silicon oxide film, weakening the silicon oxide film and facilitating polishing.
Data has been obtained that suggests that the amount of trivalent cerium present is large on the surface of high-density small-diameter ceria. It has also been found that the removal rate of high-density small-diameter ceria is significantly maximized at relatively high temperatures.
It is believed that the mixture of high-density small-diameter ceria with large-diameter ceria increases friction during polishing, resulting in high temperatures, allowing the small-diameter ceria to exert its functions and improve the polishing rate.
In addition, in the present disclosure, it is considered that the polishing rate is improved by the action of both the function of small-diameter ceria and the physical cutting of large-diameter ceria, since D50/D99 in the particle size distribution obtained by centrifugal sedimentation is 0.32 or less. It is known that the particle size distribution can usually be measured by centrifugal sedimentation, dynamic light scattering, etc., but in the present disclosure, the particle size distribution of ceria is measured by centrifugal sedimentation, which has a higher resolution than dynamic light scattering.
However, the present disclosure need not be construed as being limited to these mechanisms.

[Cerium oxide (ceria) particles]
The polishing liquid composition of the present disclosure contains, as polishing abrasive grains, cerium oxide particles of Component A and cerium oxide particles of Component B. Each of Component A and Component B may be one type or a combination of two or more types.

[Component A]
Component A is cerium oxide particles, preferably calcined cerium oxide particles, having an average particle size of 15 nm or more and 50 nm or less and a density of 8 g/cm ³ or more.
Here, the term "calcined cerium oxide particles" refers to cerium oxide particles (ceria particles) obtained by calcining a cerium compound. Examples of the calcined cerium oxide particles include calcined pulverized cerium oxide obtained by calcining and pulverizing a cerium compound. Examples of the cerium compound before calcination and oxidation include cerium carbonate and cerium nitrate. In one or more embodiments, the calcined cerium oxide particles may be referred to as calcined ceria. In one or more embodiments, the calcined pulverized cerium particles may be referred to as calcined pulverized ceria.

The shape of component A can be, for example, roughly spherical, polyhedral, or raspberry-shaped.

From the viewpoint of improving the polishing rate, the average particle size of component A is 15 nm or more, preferably 20 nm or more, and more preferably 22 nm or more, and from the same viewpoint, it is 50 nm or less, preferably 40 nm or less, and more preferably 30 nm or less. From the same viewpoint, the average particle size of component A is 15 nm or more and 50 nm or less, preferably 20 nm or more and 50 nm or less, more preferably 20 nm or more and 40 nm or less, and even more preferably 22 nm or more and 30 nm or less.

In the present disclosure, the "average particle size" refers to a particle size at which the cumulative frequency from the small diameter side is 50% in a particle size distribution calculated by weight obtained by centrifugal sedimentation.
In the present disclosure, the centrifugal sedimentation method, in one or more embodiments, is a method of classifying and detecting particles by size based on the difference in sedimentation velocity (disk centrifugal sedimentation light transmission method). The particle size distribution by the centrifugal sedimentation method can be measured, for example, using a disk centrifugal particle size distribution measuring device (CPS Disc Centrifuge). In the following description, the particle size distribution by the centrifugal sedimentation method is sometimes referred to as "particle size distribution by CPS measurement". The average particle size can be calculated by the measurement method described in the examples.

From the viewpoint of improving the polishing rate, the density of component A is 8 g/ ^cm3 or more, preferably 8.5 g/cm3 or ^more , and more preferably 8.7 g/cm3 or ^more , and from the same viewpoint, it is preferably 10 g/cm3 or ^less , and more preferably 9.8 g/cm3 or ^less . From the same viewpoint, the density of component A is preferably 8 g/cm3 or ^more and 10 g/cm3 ^or less, more preferably 8.5 g/cm3 ^{or more} and 10 g/cm3 or ^less , and even more preferably 8.7 g/cm3 or ^more and 9.8 g/cm3 or ^less .
In the present disclosure, "density" refers to a value measured by a pycnometer. The density can be measured by the method described in the Examples.

In one or more embodiments, component A can be produced using tetravalent ceria. For example, nanocrystalline ceria is produced from a tetravalent ceria precursor, and this is fired to grow crystals to obtain single-crystalline ceria (small-diameter ceria). This single-crystalline ceria is then pulverized to produce small-diameter, high-density fired ceria (component A). The average particle size and density of component A can be controlled by the size of the nanocrystalline ceria, the firing conditions, and the pulverization conditions. For example, the density can be increased by increasing the firing temperature.

From the viewpoint of improving the polishing rate, the content of component A in the polishing composition of the present disclosure is preferably 0.01 mass% or more, more preferably 0.05 mass% or more, even more preferably 0.07 mass% or more, and even more preferably 0.1 mass% or more, and from the same viewpoint, it is preferably 2 mass% or less, more preferably 1 mass% or less, even more preferably 0.5 mass% or less, and even more preferably 0.4 mass% or less. From the same viewpoint, the content of component A in the polishing composition of the present disclosure is preferably 0.01 mass% or more and 2 mass% or less, more preferably 0.05 mass% or more and 1 mass% or less, even more preferably 0.07 mass% or more and 0.5 mass% or less, and even more preferably 0.1 mass% or more and 0.4 mass% or less. When component A is a combination of two or more types of cerium oxide particles, the content of component A refers to the total content thereof.

[Component B]
Component B is cerium oxide particles having an average particle size of 60 nm to 1 μm. Component B has a larger average particle size than Component A.

There are no particular limitations on the manufacturing method, shape, and surface state of Component B. Examples of Component B 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. In one or more embodiments, colloidal ceria is an example of wet cerium oxide (hereinafter, also referred to as "wet ceria").
An example of the amorphous ceria is pulverized ceria. An example of the pulverized ceria is sintered pulverized cerium oxide obtained by sintering and pulverizing a cerium compound such as cerium carbonate or cerium nitrate. Another example of the pulverized ceria is single crystal pulverized ceria obtained by wet-pulverizing ceria particles in the presence of an inorganic acid or an organic acid. An example of the inorganic acid used in the wet-pulverization is nitric acid, and an example of the organic acid is an organic acid having a carboxyl group, specifically at least one selected from picolinic acid, glutamic acid, aspartic acid, aminobenzoic acid, and p-hydroxybenzoic acid. An example of the wet-pulverization method is wet-pulverization using a planetary bead mill or the like.
Examples of ceria-coated silica include composite particles having a structure in which at least a portion of the surface of silica particles is coated with granular ceria, as described in Examples 1 to 14 of JP2015-63451A or Examples 1 to 4 of JP2013-119131A. The composite particles can be obtained, for example, by depositing ceria on silica particles.

Examples of the shape of component B include roughly spherical, polyhedral, and raspberry shapes.

From the viewpoint of improving the polishing rate, the average particle size of component B is 60 nm or more, preferably 70 nm or more, more preferably 80 nm or more, and even more preferably 90 nm or more. From the viewpoint of reducing polishing scratches, it is 1 μm or less, preferably 500 nm or less, more preferably 250 nm or less, and even more preferably 125 nm or less. From the same viewpoint, the average particle size of component B is 60 nm or more and 1 μm or less, preferably 70 nm or more and 500 nm or less, more preferably 80 nm or more and 250 nm or less, and even more preferably 90 nm or more and 125 nm or less.

From the viewpoint of improving the polishing rate, the density of component B is preferably less than 8 g/cm ³ , more preferably 7.8 g/cm ³ or less, and even more preferably 7.5 g/cm ³ or less. From the viewpoint of reducing polishing scratches, it is preferably 6 g/cm ³ or more, more preferably 6.3 g/cm ³ or more, and even more preferably 6.6 g/cm ³ or more. From the same viewpoint, the density of component B is preferably 6 g/cm ³ or more and less than 8 g/cm ³ , more preferably 6.3 g/cm ³ or more and 7.8 g/cm ³ or less, and even more preferably 6.6 g/cm ³ or more and 7.5 g/cm ³ or less. The density of component B obtained by the above method is usually less than 8 g/cm ³ .

From the viewpoint of improving the polishing rate, the content of component B in the polishing liquid composition of the present disclosure is preferably 0.01 mass% or more, more preferably 0.05 mass% or more, even more preferably 0.07 mass% or more, and even more preferably 0.1 mass% or more, and from the viewpoint of reducing polishing scratches, it is preferably 4 mass% or less, more preferably 3 mass% or less, even more preferably 2 mass% or less, and even more preferably 1.5 mass% or less. From the same viewpoint, the content of component B in the polishing liquid composition of the present disclosure is preferably 0.01 mass% or more and 4 mass% or less, more preferably 0.05 mass% or more and 3 mass% or less, even more preferably 0.07 mass% or more and 2 mass% or less, and even more preferably 0.1 mass% or more and 1.5 mass% or less. When component B is a combination of two or more types of cerium oxide particles, the content of component B refers to the total content thereof.

In the particle size distribution of the mixture of components A and B in the polishing liquid composition of the present disclosure, which is calculated by centrifugal sedimentation, the particle sizes at which the cumulative frequency from the small particle size side is 50% and 99% are D50 and D99, respectively. From the viewpoint of improving the polishing rate, the value of D50/D99 is 0.32 or less, preferably 0.3 or less, more preferably less than 0.3, and even more preferably 0.25 or less. From the viewpoint of reducing polishing scratches, the value of D50/D99 is preferably 0.01 or more, more preferably 0.05 or more, even more preferably 0.08 or more, and even more preferably 0.1 or more. From the same viewpoint, the value of D50/D99 in the polishing liquid composition of the present disclosure is preferably 0.01 or more and 0.32 or less, more preferably 0.05 or more and 0.3 or less, even more preferably 0.08 or more and less than 0.3, and even more preferably 0.1 or more and 0.25 or less.

The weight ratio (A/B) of the content of component A to the content of component B in the polishing liquid composition of the present disclosure is preferably 1/6 or more, more preferably 1/4 or more, and even more preferably 1/3 or more, from the viewpoint of reducing polishing scratches. From the viewpoint of improving the polishing speed, it is preferably 4/1 or less, more preferably 3/1 or less, and even more preferably 2/1 or less. From the viewpoint of improving the polishing speed, the weight ratio (A/B) in the polishing liquid composition of the present disclosure is preferably 1/6 or more and 4/1 or less, more preferably 1/4 or more and 3/1 or less, and even more preferably 1/3 or more and 2/1 or less.

From the viewpoint of improving the polishing rate, the total content of component A and the total content of component B in the polishing liquid composition of the present disclosure is preferably 0.05 mass% or more, more preferably 0.1 mass% or more, even more preferably 0.2 mass% or more, and even more preferably 0.3 mass% or more. From the viewpoint of reducing polishing scratches, it is preferably 6 mass% or less, more preferably 5 mass% or less, even more preferably 3 mass% or less, and even more preferably 2 mass% or less. From the same viewpoint, the total content of component A and the total content of component B in the polishing liquid composition of the present disclosure is preferably 0.05 mass% or more and 6 mass% or less, more preferably 0.1 mass% or more and 5 mass% or less, even more preferably 0.2 mass% or more and 3 mass% or less, and even more preferably 0.3 mass% or more and 2 mass% or less.

[Aqueous medium]
The aqueous medium contained in the polishing liquid 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. The above-mentioned solvent includes a solvent miscible with water (e.g., 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 is not particularly limited as long as the effect of the present disclosure is not hindered, and from the viewpoint of economy, for example, 95% by mass or more is preferable, 98% by mass or more is more preferable, and substantially 100% by mass is even more preferable. From the viewpoint of surface cleanliness of the polished substrate, the aqueous medium is preferably water, more preferably ion-exchanged water and ultrapure water, and even more preferably ultrapure water. The content of the aqueous medium in the polishing liquid composition of the present disclosure can be the remainder excluding component A, component B, and component C described below and optional components that are blended as necessary.

[Additive (Component C)]
In one or a plurality of embodiments, the polishing liquid composition of the present disclosure may contain, from the viewpoint of improving the polishing rate, a compound (component C) having a reduction potential of 0.45 V or more and 0.95 V or less when a 10 ppm aqueous solution is measured by cyclic voltammetry (with an Ag/AgCl electrode as a reference).

From the viewpoint of improving the polishing rate, the reduction potential is preferably 0.45 V or more, more preferably 0.5 V or more, and even more preferably 0.55 V or more, and from the same viewpoint, it is preferably 0.95 V or less, more preferably 0.92 V or less, and even more preferably 0.89 V or less. The reduction potential can be measured by the method described in the Examples.

In one or more embodiments, from the viewpoint of improving the polishing rate, Component C is preferably a reducing compound containing a heteroaromatic ring skeleton. Examples of Component C include an N-oxide compound or a salt thereof that contains a nitrogen-containing heteroaromatic ring skeleton in which at least one hydrogen atom is substituted with a hydroxyl group. Component C may be one type or a combination of two or more types.

<N-oxide compound>
In one embodiment, Component C contained in the polishing liquid composition of the present disclosure is an N-oxide compound or a salt thereof, which contains a nitrogen-containing heteroaromatic ring skeleton in which at least one hydrogen atom of the nitrogen-containing heteroaromatic ring is substituted with a hydroxyl group. Examples of the salt include alkali metal salts, alkaline earth metal salts, organic amine salts, and ammonium salts. Component C may be used alone or in combination of two or more types.
Thus, in one aspect, the present disclosure relates to a polishing liquid composition for silicon oxide films, which contains cerium oxide particles (components A and B), an N-oxide compound (component C), and an aqueous medium, wherein component C is an N-oxide compound or a salt thereof that contains a nitrogen-containing heteroaromatic ring skeleton in which at least one hydrogen atom is substituted with a hydroxyl group.

In this aspect, in one or more embodiments, the N-oxide compound refers to a compound having an N-oxide group (N→O group). The N-oxide compound can have one or more N→O groups, and from the viewpoint of availability, the number of N→O groups is preferably one.
In this embodiment, the term "nitrogen-containing heteroaromatic ring skeleton in which at least one hydrogen atom is substituted with a hydroxyl group" refers to a structure in which at least one hydrogen atom of a nitrogen-containing heteroaromatic ring is substituted with a hydroxyl group.

In this embodiment, at least one nitrogen atom contained in the nitrogen-containing heteroaromatic ring skeleton of Component C forms an N-oxide. In one or more embodiments, the nitrogen-containing heteroaromatic ring contained in Component C may be a monocyclic or bicyclic fused ring. In one or more embodiments, the number of nitrogen atoms in the nitrogen-containing heteroaromatic ring contained in Component C may be 1 to 3, and from the viewpoint of improving the polishing rate, 1 or 2 is preferable, and 1 is more preferable.
In one or more embodiments, the nitrogen-containing heteroaromatic ring skeleton contained in Component C may be at least one selected from a pyridine N-oxide skeleton, a quinoline N-oxide skeleton, and the like. In the present disclosure, the pyridine N-oxide skeleton refers to a structure in which a nitrogen atom contained in a pyridine ring forms an N-oxide. The quinoline N-oxide skeleton refers to a structure in which a nitrogen atom contained in a quinoline ring forms an N-oxide.

In one or more embodiments, Component C may be at least one selected from an N-oxide compound having a pyridine ring in which at least one hydrogen atom is substituted with a hydroxyl group, an N-oxide compound having a quinoline ring in which at least one hydrogen atom is substituted with a hydroxyl group, and salts thereof. Among these, from the viewpoint of improving the polishing rate, Component C is preferably an N-oxide compound having a pyridine ring in which at least one hydrogen atom of the pyridine ring is substituted with a hydroxyl group, or a salt thereof.
In one or more embodiments, component C includes 2-hydroxypyridine N-oxide.

From the viewpoint of improving the polishing rate, the content of component C in the polishing liquid composition of the present disclosure is preferably 0.0001 mass% or more, more preferably 0.001 mass% or more, even more preferably 0.006 mass% or more, and even more preferably 0.01 mass% or more, and from the same viewpoint, it is preferably 1 mass% or less, more preferably 0.5 mass% or less, even more preferably 0.1 mass% or less, and even more preferably 0.06 mass% or less. The content of component C in the polishing liquid composition of the present disclosure is preferably 0.0001 mass% or more and 1 mass% or less, more preferably 0.001 mass% or more and 0.5 mass% or less, even more preferably 0.006 mass% or more and 0.1 mass% or less, and even more preferably 0.01 mass% or more and 0.06 mass% or less. When component C is a combination of two or more types, the content of component C refers to the total content thereof.

The mass ratio (A+B)/C (total content of components A and B/content of component C) of the total of components A and B in the polishing composition of the present disclosure is preferably 0.1 or more, more preferably 10 or more, even more preferably 25 or more, and even more preferably 50 or more, from the viewpoint of improving the polishing rate, and from the same viewpoint, is preferably 6000 or less, more preferably 600 or less, even more preferably 300 or less, and even more preferably 200 or less. The mass ratio A/B in the polishing composition of the present disclosure is preferably 0.1 or more and 6000 or less, more preferably 10 or more and 600 or less, even more preferably 25 or more and 300 or less, and even more preferably 50 or more and 200 or less.

[Optional ingredients]
The polishing liquid composition of the present disclosure may further contain optional components such as pH adjusters, surfactants, thickeners, dispersants, rust inhibitors, preservatives, basic substances, polishing rate enhancers, silicon nitride film polishing inhibitors, polysilicon film polishing inhibitors, and counter ions. 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 preferably 0.001 mass% or more, more preferably 0.0025 mass% or more, even more preferably 0.01 mass% or more, and preferably 1 mass% or less, more preferably 0.5 mass% or less, and even more preferably 0.1 mass% or less, from the viewpoint of improving the polishing rate. The content of the optional components in the polishing liquid composition of the present disclosure is preferably 0.001 mass% or more and 1 mass% or less, more preferably 0.0025 mass% or more and 0.5 mass% or less, and even more preferably 0.01 mass% or more and 0.1 mass% or less.

In one or more embodiments, the polishing composition of the present disclosure may not contain functionalized pyridine, benzoic acid, amino acid, or combinations thereof.

[Polishing 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, and an aqueous medium, and, if desired, the above-mentioned component C and any optional components, by a known method. For example, the polishing composition of the present disclosure can be produced by blending at least component A, component B, and an aqueous medium. When component A and/or component B are a combination of multiple types of cerium oxide particles, component A and/or component B can be obtained by blending multiple types of cerium oxide particles, respectively. 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, respectively.
In the present disclosure, "blending" includes mixing component A, component B, and the aqueous medium, and, if necessary, the above-mentioned component C and any optional components simultaneously or in sequence. 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, or a wet ball mill. The blending amount of each component in the method for producing the polishing liquid composition of the present disclosure can be the same as the content of each component in the above-mentioned polishing liquid composition of the present disclosure.

The embodiment of the polishing liquid composition of the present disclosure may be a so-called one-liquid type in which all components are supplied to the market in a premixed state, or a so-called two-liquid type in which the components are mixed at the time of use. One embodiment of a two-liquid type polishing liquid composition is composed of a first liquid containing component A and a second liquid containing component B, and the first liquid and the second liquid are mixed at the time of use. The first liquid and the second liquid may be mixed before being supplied to the surface to be polished, or they may be supplied separately and mixed on the surface of the substrate to be polished. The first liquid and the second liquid may each contain the above-mentioned component C and optional components as necessary.

From the viewpoint of improving the polishing rate, the pH of the polishing liquid composition of the present disclosure is 3 or more, preferably 3.5 or more, more preferably 4 or more, even more preferably 4.5 or more, and 9 or less, preferably 8.5 or less, more preferably 8 or less, even more preferably less than 8, even more preferably 7 or less, and even more preferably 6 or less. The pH of the polishing liquid composition of the present disclosure is 3 or more and 9 or less, preferably 3.5 or more and 9 or less, more preferably 4 or more and 8.5 or less, even more preferably 4.5 or more and 8 or less, even more preferably 4.5 or more and less than 8, even more preferably 4.5 or more and 7 or less, and even more preferably 4.5 or more and 6 or less. In the present disclosure, the pH of the polishing liquid composition is a value at 25°C, and can be measured using a pH meter and can be measured by the method described in the examples.

In the present disclosure, "the content of each component in the polishing liquid composition" refers to the content of each component at the time of polishing, i.e., at the time when the polishing liquid composition begins to be used for polishing. The polishing liquid 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 production and transportation costs can be reduced. This concentrated liquid can then be appropriately diluted with water as necessary for use in the polishing process. The dilution ratio is preferably 5 to 100 times.

[Film to be polished]
Examples of films to be 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 that require the polishing of silicon oxide films. That is, in one or more embodiments, the polishing composition of the present disclosure is a polishing composition (polishing composition for silicon oxide films) used for polishing silicon oxide films. In one or more embodiments, the polishing composition of the present disclosure can be suitably used for polishing silicon oxide films performed in a process for forming an element isolation structure of a semiconductor substrate, polishing silicon oxide films performed in a process for forming an interlayer insulating film, polishing silicon oxide films performed in a process for forming embedded metal wiring, or polishing silicon oxide films performed in a process for forming embedded capacitors. In one or more other embodiments, the polishing composition of the present disclosure can be suitably used for manufacturing three-dimensional semiconductor devices such as three-dimensional NAND-type flash memories.

[Polishing liquid kit]
In another aspect, the present disclosure relates to a kit for producing the polishing liquid composition of the present disclosure (hereinafter also referred to as the "polishing liquid kit of the present disclosure").
The polishing liquid kit of the present disclosure may be, for example, a polishing liquid kit (two-liquid type polishing liquid composition) that includes a polishing abrasive dispersion containing component A, component B, and an aqueous medium, and an aqueous solution containing other components (component C or optional components) in a mutually unmixed state. The polishing abrasive dispersion and the additive aqueous solution are mixed at the time of use, and diluted with an aqueous medium as necessary. The aqueous medium contained in the polishing abrasive dispersion may be the entire amount of the aqueous medium used to prepare the polishing liquid composition, or may be a part of it. The additive aqueous solution may contain a part of the aqueous medium used to prepare the polishing liquid composition. The polishing abrasive dispersion and the additive aqueous solution may each contain the above-mentioned optional components as necessary.
According to the polishing liquid kit of the present disclosure, a polishing liquid composition can be obtained that can improve polishing selectivity while ensuring the polishing rate.

[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") that includes a step of polishing a film to be polished using the polishing liquid composition of the present disclosure, the film to be polished being a silicon oxide film formed in the manufacturing process of a semiconductor substrate. By using the polishing method of the present disclosure, it is possible to improve the polishing speed of the silicon oxide film, and therefore it is possible to achieve an effect of improving the productivity of semiconductor substrates with improved quality. The polishing method and conditions in the polishing method of the present disclosure can be the same as those in the manufacturing method of a semiconductor substrate of the present disclosure described below.

[Method of manufacturing semiconductor substrate]
In one aspect, the present disclosure relates to a method for producing a semiconductor substrate, comprising a step of polishing a silicon oxide film with the polishing composition of the present disclosure (polishing step).
In one aspect, the present disclosure relates to a method for producing a semiconductor substrate, comprising a step of polishing a silicon oxide film using the polishing method of the present disclosure (polishing step).
In the present disclosure, the term "the method for manufacturing a semiconductor substrate according to the present disclosure" can refer to the above two aspects.
According to the method for manufacturing a semiconductor substrate of the present disclosure, it is possible to improve the polishing speed of a silicon oxide film, and therefore it is possible to achieve the effect of efficiently manufacturing semiconductor substrates with improved quality.

In one or more embodiments of the method for manufacturing a semiconductor substrate according to the present disclosure, first, a silicon dioxide layer is grown on the surface of a silicon substrate by exposing the silicon substrate to oxygen in an oxidation furnace, and then a polishing stopper film such as a silicon nitride (Si ₃ N ₄ ) film or a polysilicon film is formed on the silicon dioxide layer by, for example, a CVD method (chemical vapor deposition method). Next, a trench is formed by photolithography in 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 in which a polishing stopper film is formed on a silicon dioxide layer of the silicon substrate. Next, a silicon oxide (SiO ₂ ) film, which is a polishing film to be filled in the trench, is formed by, for example, a CVD method using silane gas and oxygen gas, to obtain a polishing substrate in which the polishing stopper film is covered with the polishing film (silicon oxide film). By forming the silicon oxide film, the trench is filled with silicon oxide of the silicon oxide film, and the surface of the polishing stopper film opposite to the surface on the silicon substrate side is covered with the silicon oxide film. The surface of the silicon oxide film formed in this manner opposite to the surface on the silicon substrate side has a step formed corresponding to the unevenness of the underlying layer. Next, the silicon oxide film is polished by a CMP method until at least the surface opposite to the surface on the silicon substrate side of the polishing stopper film is exposed, and more preferably, the silicon oxide film is polished until the surface of the silicon oxide film and the surface of the polishing stopper film are flush with each other. The polishing liquid composition of the present disclosure can be used in the step of performing polishing by this CMP method. The width of the convex portion formed corresponding to the unevenness of the underlying layer of the silicon oxide film is, for example, 0.5 μm or more and 5000 μm or less, and the width of the concave portion is, for example, 0.5 μm or more and 5000 μm or less.

In polishing by the CMP method, the surface of the substrate to be polished is brought into contact with a polishing pad, and the substrate to be polished and the polishing pad are moved relative to each other while the polishing liquid composition of the present disclosure is supplied to the contact site, thereby planarizing the uneven portions of the surface of the substrate to be polished.
In the semiconductor substrate manufacturing method of the present disclosure, another insulating film may be formed between the silicon dioxide layer of the silicon substrate and the polishing stopper film, or another insulating film may be formed between the film to be polished (e.g., a silicon oxide film) and the polishing stopper film (e.g., a silicon nitride film).

In the polishing step, the rotation speed of the polishing pad can be set to, for example, 30 to 200 r/min, the rotation speed of the substrate to be polished can be set to, for example, 30 to 200 r/min, the polishing load set in the polishing apparatus equipped with the polishing pad can be set to, for example, 20 to 500 gf/cm ² , and the supply rate of the polishing composition can be set to, for example, 10 to 500 mL/min or less. When the polishing composition is a two-liquid type polishing composition, the respective polishing rates of the polishing target film and the polishing stopper film, and the polishing rate ratio (polishing selectivity) between the polishing target film and the polishing stopper film can be adjusted by adjusting the respective supply rates (or supply amounts) of the first liquid and the second liquid.

In the polishing process, the polishing speed of the film to be polished (silicon oxide film) is preferably 50 nm/min or more, more preferably 80 nm/min or more, and even more preferably 90 nm/min or more, from the viewpoint of improving productivity.

The present disclosure will be described in more detail below with reference to examples, but these are merely illustrative and the present disclosure is not limited to these examples.

1. Method for measuring each parameter (1) pH of polishing composition
The pH value of the polishing composition at 25° C. was measured using a pH meter (manufactured by Toa Denpa Kogyo Co., Ltd., "HM-30G"), and was the value measured one minute after the electrode of the pH meter was immersed in the polishing composition.

(2) Measurement method of D50 and D99 of cerium oxide particles by centrifugal sedimentation (CPS measurement) Cerium oxide particles were diluted with ion-exchanged water to prepare a dispersion containing 0.4 mass% of cerium oxide particles as a sample, and the particle size distribution was measured by centrifugal sedimentation using the following measuring device. The particle sizes at which the cumulative frequency from the small diameter side in the particle size distribution in weight conversion obtained by centrifugal sedimentation was 50% and 99%, respectively, were defined as D50 and D99. The D50 of component A and component B were defined as their average particle sizes.
<Measurement conditions>
Measuring device: "CPS DC24000 UHR" manufactured by CPS Instruments. Measurement range: 0.02 to 3 μm.
Particle extinction coefficient: 0.1
Particle shape factor: 1.2 or 1.0
Revolutions per minute: 17,000 rpm
Calibration standard particle size: 0.476μm
Standard particle density: 1.0465 (13%, 34°C)
Density gradient solution: sucrose aqueous solution (8%, 24%)
Solvent viscosity: 1.16 cp (13%, 34° C.)
Refractive index of solvent: 1.3592 (18%, 34°C)
Measurement temperature: 15-45℃
Measurement time: 3 to 420 minutes

(3) Density of cerium oxide particles The cerium oxide particles were dried for 2 hours at 400° C. using a hot stirrer (CERAMIC HOT PLATE CHP-170DF, manufactured by AS ONE Co., Ltd.), and then baked for 1 hour at 650° C. using an electric furnace (FT-101, manufactured by Furutech Co., Ltd.). Next, the density of the sample was measured using a fully automatic pycnometer (ULTRAPYC 1200e, manufactured by Quantachrome Corporation).

(4) Reduction Potential and Oxidation Potential 1) An aqueous solution of sodium sulfate used as a supporting electrolyte is prepared with ultrapure water to a concentration of 0.1 mol/L, and nitrogen replacement is carried out for 3 hours or more.
2) Weigh out 9.9 mL of an aqueous sodium sulfate solution into a glass vial (20 mL).
3) The surface of the glassy carbon working electrode is polished sufficiently by pressing the electrode vertically with a 1 μm polishing diamond and a diamond polishing pad (both manufactured by BAS Co., Ltd.) to draw a figure 8. Then, using a 0.05 μm alumina and an alumina polishing pad (both manufactured by BAS Co., Ltd.), the electrode surface is polished sufficiently by drawing a figure 8 until it becomes a mirror surface. After that, the electrode surface is washed with ultrapure water and dried.
4) A glassy carbon electrode, a silver/silver-silver chloride reference electrode, and a platinum counter electrode are connected to an ALS electrochemical analyzer (Model 611D) and immersed in an aqueous sodium sulfate solution to assemble a three-electrode electrochemical cell.
5) Set the cyclic voltammetry parameters as follows: high potential 1 V, low potential 1 V, scan rate 0.1 V/s, sweep segment 5 w, and display potential-current data points on the monitor.
6) After thoroughly replacing the nitrogen gas in the glass vial by inserting a Teflon tube into the vial, the measurement is carried out using only the supporting electrolyte. If the nitrogen replacement is insufficient, a peak due to dissolved oxygen will be detected.
7) A measurement sample (additive: 1000 ppm) was prepared in ultrapure water and thoroughly substituted with nitrogen. After that, 0.1 mL of the measurement sample was added to 9.9 mL of an aqueous sodium sulfate solution in a glass vial to obtain a 10 ppm aqueous solution of the additive.
8) Measure the Open Circuit Potential, set it as the initial potential of the cyclic voltammetry variables, and perform the measurement. At this time, it is confirmed that no peaks derived from dissolved oxygen are detected, and the redox potential is confirmed from the cyclic voltammogram derived from the measurement sample.

2. Preparation of polishing compositions (Examples 1 to 7 and Comparative Examples 1 to 13)
Cerium oxide particles (component A, component B), an additive (component C), and water were mixed to obtain polishing liquid compositions of Examples 1 to 7 and Comparative Examples 1 to 13. The contents of each component in the polishing liquid compositions are as shown in Tables 1 to 3. The content of water is the remainder excluding components A, B, and C. The pH of the polishing liquid compositions of Examples 1 to 7 and Comparative Examples 1 to 13 was 5. The pH was adjusted using ammonia or nitric acid.

Components A, B, and C used in preparing the polishing compositions of Examples 1 to 7 and Comparative Examples 1 to 13 are shown below.
[Component A]
Cerium oxide particles a1: particle size 26 nm, density 9 g/cm ³ , calcined cerium oxide Cerium oxide particles a2: particle size 53 nm, density 7.6 g/cm ³ , wet cerium oxide (colloidal ceria), "HC-30" manufactured by Solvay SpecialChem Japan Ltd.
Cerium oxide particles a3: particle size 76 nm, density 7.9 g/cm ³ , calcined cerium oxide [component B]
Cerium oxide particles b1: particle size 97 nm, density 7.4 g/cm ³ , calcined cerium oxide Cerium oxide particles b2: particle size 111 nm, density 6.9 g/cm ³ , wet cerium oxide (colloidal ceria), "HC-60" manufactured by Solvay SpecialChem Japan
[Component C]
2-Hydroxypyridine N-oxide (Tokyo Chemical Industry Co., Ltd., reduction potential: 0.87 V)

The calcined cerium oxide particles a1, a3, and b1 were produced by calcining a cerium compound. The shapes of the calcined cerium oxide particles a1, a3, and b1 were observed with a scanning electron microscope (SEM), and as a result, the particles a1 and a3 were polyhedral, and the particle b1 was irregular.

Wet Cerium Oxide The wet cerium oxide particles a2 and b2 were found to have a polyhedral shape as a result of observation with a scanning electron microscope (SEM).

3. Evaluation of polishing composition [Measurement of polishing rate]
As an object to be polished, a plain film substrate was prepared in which a SiO ₂ film was formed on the entire surface of an 8-inch silicon wafer to a thickness of 2000 nm.
A polishing machine (Ebara Corporation, F-REX200) and polishing pads (Nitta Haas, upper layer: IC1000, lower layer: SUBA400) were used.
The polishing conditions were: processing pressure: 3 psi (288 gf/cm ² ), polishing composition flow rate: 200 ml/min, polishing head rotation speed: 107 rpm, platen rotation speed: 100 rpm, polishing time: 60 seconds.
Next, the polishing rate (polishing speed) per minute was determined from the amount of reduction in thickness of the workpiece before and after polishing using an optical interference film thickness measuring device (Nanospec 6100 manufactured by Nanometrics).

The results of polishing using a polishing composition in which the total concentration of cerium oxide particles (component A and component B) in the polishing composition is 0.5 mass % are shown in Tables 1 and 2.

Table 3 shows the results of polishing using a polishing composition in which the total concentration of cerium oxide particles (component A and component B) in the polishing composition is 1.5 mass %.

As shown in Table 1, the polishing compositions of Examples 1 and 2 had improved removal rates compared to the polishing compositions of Comparative Examples 1 to 6.
As shown in Table 2, the polishing compositions of Examples 3 and 4 had improved removal rates compared to the polishing compositions of Comparative Examples 7 to 9.
As shown in Table 3, the polishing compositions of Examples 5 to 7 had improved polishing rates compared to the polishing compositions of Comparative Examples 10 to 13. Furthermore, the polishing compositions of Examples 6 and 7, which contained the additive (component C), had improved polishing rates compared to the polishing composition of Example 5, which did not contain the additive (component C).

The polishing composition disclosed herein is useful in a method for manufacturing semiconductor substrates for high density or high integration.

Claims (11)

A polishing composition for silicon oxide films, comprising cerium oxide particles and an aqueous medium,
As cerium oxide particles,
The cerium oxide particles (component A) have an average particle size of 15 nm or more and 50 nm or less and a density of 8 g/cm3 or ^more , and the cerium oxide particles (component B) have an average particle size of 60 nm or more and 1 μm or less,
The pH is 3 or more and 9 or less,
A polishing liquid composition, in which when D50 and D99 are the particle sizes at which the cumulative frequency from the small particle size side is 50% and 99%, respectively, in a particle size distribution in weight conversion obtained by centrifugal sedimentation of a mixture of components A and B, the value of D50/D99 is 0.32 or less. 2. The polishing composition according to claim 1, wherein component A is cerium oxide particles having an average particle size of 20 nm or more and 50 nm or less and a density of 8.5 g/cm ³ or more and 10 g/cm ³ or less. The polishing composition according to claim 1 or 2, wherein component A is calcined cerium oxide particles. The polishing composition according to any one of claims 1 to 3, wherein the weight ratio (A/B) of the content of component A to the content of component B in the polishing composition is 1/6 or more and 4/1 or less. 5. The polishing composition according to claim 1, wherein component B has a density of 6 g/ ^cm3 or more and less than 8 g/ ^cm3 . The polishing composition according to any one of claims 1 to 5, wherein the total content of component A and component B in the polishing composition is 0.3 mass% or more and 2 mass% or less. The polishing composition according to any one of claims 1 to 6, wherein the value of D50/D99 is 0.1 or more and 0.25 or less. The polishing composition according to any one of claims 1 to 7 further contains a compound (component C) whose reduction potential is 0.45 V or more and 0.95 V or less when a 10 ppm aqueous solution is measured by cyclic voltammetry (Ag/AgCl electrode standard). The polishing composition according to claim 8, wherein component C is at least one selected from an N-oxide compound having a pyridine ring in which at least one hydrogen atom is substituted with a hydroxyl group, an N-oxide compound having a quinoline ring in which at least one hydrogen atom is substituted with a hydroxyl group, and salts thereof. A polishing method comprising a step of polishing a film to be polished using the polishing composition according to any one of claims 1 to 9, the film to be polished being a silicon oxide film formed during the manufacturing process of a semiconductor substrate. A method for manufacturing a semiconductor substrate, comprising a step of polishing a film to be polished using the polishing composition according to any one of claims 1 to 9.