JP7349897B2 - Immersion liquid composition for semiconductor substrates - Google Patents

Description

The present disclosure relates to immersion liquid compositions for semiconductor substrates.

In recent years, the design rules for semiconductor devices have been becoming smaller due to the increasing demand for higher storage capacity of semiconductor memories. For this reason, the depth of focus in photolithography performed in the manufacturing process of semiconductor devices has become shallower, and requirements for reducing surface defects (LPD: light point defects) and surface roughness (haze) of silicon wafers (bare wafers) have become increasingly strict. It has become.

In order to improve the quality of silicon wafers, polishing of silicon wafers is performed in multiple stages. If particles derived from polishing debris or abrasive grains remain on the surface of a silicon wafer after polishing, they may cause surface defects. Typically, polished silicon wafers are transported to a cleaning process to remove particles remaining on the wafer surface, but until they are transported to the cleaning process, they are stored in an aqueous solution containing citric acid. This is because if silicon wafers are stored in the atmosphere, particles will stick to the wafer surface, making it difficult to remove them in a cleaning process.

As a method for removing particles remaining on the wafer surface after polishing, for example, Patent Document 1 describes a method for removing fine organic or inorganic foreign particles used when forming semiconductor elements on a semiconductor substrate such as a silicon wafer. As a cleaning composition with low foaming properties that is effective in removing oil and oil, at least one selected from acrylic acid, methacrylic acid, and maleic acid is used as a monomer component, and the monomer component is used in an amount of 20 mol of the total amount of monomer components used. % or more of a polycarboxylic acid compound having a weight average molecular weight of 500 to 150,000, a cleaning composition for semiconductor substrates or semiconductor elements is disclosed.

Japanese Patent Application Publication No. 11-181494

In recent years, as the performance of semiconductor devices has improved, the width of semiconductor wiring has become smaller. Accordingly, there is a need to further reduce the number of particles remaining on the surface of a semiconductor wafer (semiconductor substrate), and methods and compositions that more effectively remove particles remaining on the wafer surface are required.

Therefore, in one aspect, the present disclosure provides an immersion liquid composition that can improve wettability to a semiconductor substrate and reduce residue on a wafer surface, and a method for manufacturing a semiconductor substrate using the immersion liquid composition. .

In one aspect, the present disclosure relates to an immersion liquid composition for a semiconductor substrate, which includes the following polymer A (component A).
Polymer A: A polymer or a salt thereof containing a structural unit a1 derived from a monomer a1 represented by the following formula (I) or its anhydride, and a structural unit a2 derived from a monomer a2 represented by the following formula (II).
[In formula (I), R ¹ , R ² and R ³ each independently represent a hydrogen atom, a methyl group, or -(CH ₂ ) _p COOM ² , and M ¹ and M ² each independently represent a hydrogen atom , an alkali metal, an alkaline earth metal (1/2 atom), or an ammonium group, and p is an integer of 0 to 2. ]
[In formula (II), R ⁴ and R ⁵ each independently represent a hydrogen atom or a methyl group, r represents an integer of 0 to 2, and AO represents an alkyleneoxy group having 2 to 18 carbon atoms. , m is the average number of added moles of AO and is 1 to 300, and X is a hydrogen atom or an alkyl group having 1 to 18 carbon atoms. ]

In other aspects, the present disclosure relates to a method for manufacturing a semiconductor substrate, including the following steps (1) and (2).
(1) A step of immersing a polished semiconductor substrate in the immersion liquid composition of the present disclosure.
(2) A step of cleaning the semiconductor substrate obtained in step (1) using a cleaning composition.

According to the present disclosure, in one embodiment, it is possible to provide an immersion liquid composition that can improve wettability to a semiconductor substrate and reduce residue on a wafer surface.

In one aspect, the present disclosure provides that by immersing a polished semiconductor substrate in an immersion liquid composition containing a specific polymer, wettability can be improved and residues on the wafer surface that cause surface defects can be removed. Based on the knowledge that it can be reduced.

That is, in one aspect, the present disclosure relates to an immersion liquid composition for a semiconductor substrate (hereinafter also referred to as "the immersion liquid composition of the present disclosure") containing the polymer A (component A).

Although the details of the mechanism by which the effects of the present disclosure are expressed are not clear, it is inferred as follows.
Generally, in the manufacture of semiconductor substrates, a polishing machine and a cleaning machine are not integrated, so it is necessary to transport the polishing machine to the cleaning machine. In order to efficiently remove particles attached to the wafer surface with a cleaning machine, before cleaning, reduce the amount of residue attached to the wafer surface and make it easier for the residue to peel off from the wafer surface. It is possible that
In the present disclosure, both the alkyleneoxy group [-(CH ₂ ) _r O(AO) _m -X in formula (II)] and the carboxylic acid unit [COOM ¹ in formula (I)] in polymer A are attached to the wafer. It is thought that by adsorption, the wettability to the semiconductor substrate can be improved, and particles attached to the wafer surface can be easily peeled off. When the carboxylic acid units are dissociated in the immersion liquid composition, it is thought that re-adhesion of particles to the wafer surface can be suppressed due to charge repulsion by the dissociated carboxylic acid units. In this way, particles that cause surface defects are believed to be removed from the wafer surface.
However, the present disclosure does not need to be interpreted as being limited to these mechanisms.

In the present disclosure, "immersion liquid composition for semiconductor substrates" refers to an immersion liquid composition for immersing and storing substrates used in the manufacturing process of semiconductor substrates, and a polishing liquid composition for cleaning polished substrates. It may include an immersion liquid composition for immersing and storing before a process, or an immersion liquid composition for immersing and storing a substrate polished using the polishing liquid composition before performing inorganic cleaning. . In this disclosure, a "semiconductor substrate" is a single crystal silicon wafer or a polysilicon wafer in one or more embodiments.

[Polymer A (component A)]
The immersion liquid composition of the present disclosure contains the following polymer A (hereinafter also simply referred to as "component A") in one or more embodiments. Component A may be used alone or in combination of two or more.

Polymer A is derived from a monomer a1 represented by the following formula (I) or its anhydride (hereinafter also simply referred to as "constituent unit a1") and a monomer a2 represented by the following formula (II). It is a polymer containing the structural unit a2 (hereinafter also simply referred to as "constituent unit a2") or a salt thereof. The structural unit a1 may be one type or a combination of two or more types. The structural unit a2 may be one type or a combination of two or more types.

(monomer a1)
Monomer a1 is a monomer represented by the following formula (I).

In formula (I), R ¹ , R ² and R ³ each independently represent a hydrogen atom, a methyl group, or -(CH ₂ ) _p COOM 2 , and M ¹ and ^{M 2 each} independently represent a hydrogen atom, It represents an alkali metal, an alkaline earth metal (1/2 atom), or an ammonium group, and p represents an integer of 0 or more and 2 or less.

In formula (I), R ¹ , R ² and R ³ are each independently at least one selected from a hydrogen atom, a methyl group and -(CH ₂ ) _p COOM ² , from the viewpoint of improving wettability, and From the viewpoint of reducing residue on the wafer surface, R ¹ and R ³ are preferably a hydrogen atom, R ² is preferably a hydrogen atom or a methyl group, and R ¹ and R ³ are preferably a hydrogen atom, and R ² is a methyl group.
In formula (I), M ¹ and M ² each independently represent a hydrogen atom, an alkali metal, an alkaline earth metal (1/2 atom), or an ammonium group, and from the viewpoint of improving wettability and on the wafer surface. From the viewpoint of reducing residue, alkali metals are preferred, and sodium and potassium are more preferred. Examples of the ammonium group include a group represented by "NH ₄ ⁺ " (ammonium group) and an organic ammonium group.
In formula (I), p is an integer of 0 or more and 2 or less, and is preferably 0 or 1, and more preferably 0, from the viewpoint of improving wettability and reducing residue on the wafer surface.

Monomer a1 represented by formula (I) may be anhydride.

Examples of the monomer a1 include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, their anhydrides, and salts thereof, from the viewpoint of improving wettability and reducing residue on the wafer surface. From this viewpoint, at least one selected from acrylic acid, methacrylic acid, maleic acid, and maleic anhydride is preferred, at least one of acrylic acid and methacrylic acid is more preferred, and acrylic acid is even more preferred. Examples of the salt include alkali metal salts, alkaline earth metal salts, ammonium salts, organic ammonium salts, etc. From the viewpoint of improving wettability and reducing residue on the wafer surface, alkali metal salts are preferable. More preferred are sodium and potassium salts.

(monomer a2)
Monomer a2 is a monomer represented by the following formula (II).

In formula (II), R ⁴ and R ⁵ each independently represent a hydrogen atom or a methyl group, r represents an integer of 0 to 2, AO represents an alkyleneoxy group having 2 to 18 carbon atoms, m is the average number of added moles of AO and is 1 to 300, and X is a hydrogen atom or an alkyl group having 1 to 18 carbon atoms.

In formula (II), AO represents an alkyleneoxy group having 2 or more and 18 or less carbon atoms, and the alkyleneoxy group may be in either a linear or branched form. AO may be one type or two or more types. When there are two or more types of AO, the addition format may be random or block. The number of carbon atoms in the alkyleneoxy group is 2 or more and 18 or less, and preferably 2 or more and 12 or less from the viewpoint of improving wettability and reducing residue on the wafer surface. Or 3 is more preferable. As AO, from the viewpoint of improving wettability and reducing residue on the wafer surface, at least one selected from oxyethylene (EO) group and oxypropylene (PO) group is preferable, and oxyethylene (EO) group is preferable. is more preferable.
In formula (II), m is 1 or more, preferably 5 or more, more preferably 10 or more, and even more preferably 15 or more, from the viewpoint of improving wettability and reducing residue on the wafer surface. , and is 300 or less, preferably 150 or less, more preferably 100 or less, and even more preferably 40 or less. More specifically, m is a number of 1 or more and 300 or less, preferably 5 or more and 150 or less, more preferably 10 or more and 100 or less, and even more preferably 15 or more and 40 or less.
In formula (II), X represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, and from the viewpoint of improving wettability and reducing residue on the wafer surface, X represents a hydrogen atom or an alkyl group having 1 or more carbon atoms. An alkyl group having 12 or less atoms is preferable, a hydrogen atom or an alkyl group having 1 or more and 3 or less carbon atoms is more preferable, and a hydrogen atom is even more preferable. The alkyl group may be in either a linear or branched form. Examples of the alkyl group having 1 to 18 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, etc. from the viewpoint of improving wettability and reducing residue on the wafer surface. .

As monomer a2, when r in formula (II) is 0, for example, polyethylene glycol vinyl ether, methoxypolyethylene glycol vinyl ether, ethoxypolyethylene glycol vinyl ether, propoxypolyethylene glycol vinyl ether, polypropylene glycol vinyl ether, methoxypolypropylene glycol vinyl ether, ethoxypolypropylene glycol. Examples include vinyl ether, propoxypolypropylene glycol vinyl ether, polyethylene glycol isopropenyl ether, polypropylene glycol isopropenyl ether, and the like.

As monomer a2, when r in formula (II) is 1, for example, polyethylene glycol allyl ether, methoxypolyethylene glycol allyl ether, ethoxypolyethylene glycol allyl ether, propoxypolyethylene glycol allyl ether, polypropylene glycol allyl ether, methoxypolypropylene glycol Allyl ether, ethoxypolypropylene glycol allyl ether, propoxypolypropylene glycol allyl ether, polyethylene glycol-2-methyl allyl ether, polypropylene glycol-2-methyl allyl ether, polyethylene glycol-2-butenyl ether, polypropylene glycol-2-butenyl ether etc.

As monomer a2, when r in formula (II) is 2, for example, polyethylene glycol-3-butenyl ether, methoxypolyethylene glycol-3-butenyl ether, ethoxypolyethylene glycol-3-butenyl ether, propoxypolyethylene Glycol-3-butenyl ether, polypropylene glycol-3-butenyl ether, methoxypolypropylene glycol-3-butenyl ether, ethoxypolypropylene glycol-3-butenyl ether, propoxypolypropylene glycol-3-butenyl ether, polyethylene glycol- 3-Methyl-3-butenyl ether, methoxypolyethylene glycol-3-methyl-3-butenyl ether, ethoxypolyethylene glycol-3-methyl-3-butenyl ether, propoxypolyethylene glycol-3-methyl-3-butenyl Ether, polypropylene glycol-3-methyl-3-butenyl ether, methoxypolypropylene glycol-3-methyl-3-butenyl ether, ethoxypolypropylene glycol-3-methyl-3-butenyl ether, propoxypolypropylene glycol-3-methyl -3-butenyl ether and the like.

The molar ratio (a1/a2) of the structural unit a1 to the structural unit a2 in all the structural units of component A is 50/50 or more from the viewpoint of improving wettability and reducing residue on the wafer surface. Preferably, 60/40 or more is more preferable, 65/35 or more is still more preferable, and from the same viewpoint, 99/1 or less is preferable, 95/5 or less is more preferable, and even more preferably 90/10 or less. More specifically, the molar ratio (a1/a2) is preferably 50/50 or more and 99/1 or less, more preferably 60/40 or more and 95/5 or less, and even more preferably 65/35 or more and 90/10 or less.

Component A can further contain other structural units other than structural unit a1 and structural unit a2. Examples of other structural units include (meth)acrylic acid alkyl esters, hydroxyethyl (meth)acrylates, acrylamides, vinyl acetate, styrene, olefins, vinyl alcohol, allyl alcohol, polyalkylene oxide adducts of allyl alcohol, etc. Examples include structural units derived from at least one selected compound. In the present disclosure, the total content of the structural unit a1 and the structural unit a2 in all the structural units of component A is preferably 85 mol% or more, more preferably 90 mol% or more, from the viewpoint of exerting the effects of the present disclosure. More preferably 97 mol% or more, still more preferably 99 mol% or more, even more preferably 100 mol%.

Component A can be obtained by a known method, such as by polymerizing a monomer mixture containing monomer a1 and monomer a2 by a solution polymerization method. Examples of solvents used in solution polymerization include water; aromatic hydrocarbons such as toluene and xylene; alcohols such as ethanol and 2-propanol; ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran and diethylene glycol dimethyl ether; and the like. . As the polymerization initiator used in the polymerization, known radical initiators can be used, such as ammonium peroxodisulfate (ammonium persulfate salt), hydrogen peroxide solution, sodium peroxodisulfate, and the like. During polymerization, a chain transfer agent can be further used, and examples thereof include thiol-based chain transfer agents such as 2-mercaptoethanol and β-mercaptopropionic acid; chain transfer agents and solvents such as 1,2-propanediol. . In the present disclosure, the content of each structural unit in all the structural units of component A can be considered as the ratio of the usage amount of each monomer to the total amount of monomers used for polymerization.

The arrangement of the constituent units constituting component A may be random, block, or grafted.

When component A has a salt-forming group (-COOH, -(CH ₂ ) _p COOH) derived from monomer a1, it can be used after being neutralized with a neutralizing agent. Examples of the neutralizing agent include sodium hydroxide, potassium hydroxide, and ammonia. Note that the neutralizing agent used here is different from the alkaline agent (component C) described later, and is not included in component C.

The weight average molecular weight of component A is 5,000 or more, preferably 10,000 or more, more preferably 20,000 or more, from the viewpoint of improving wettability and reducing residue on the wafer surface. It is more preferably 25,000 or more, and from the same point of view, it is 100,000 or less, preferably 80,000 or less, more preferably 70,000 or less, and even more preferably 60,000 or less. More specifically, the weight average molecular weight of component A is 5,000 or more and 100,000 or less, preferably 10,000 or more and 80,0000 or less, more preferably 20,000 or more and 70,000 or less, and 25 ,000 or more and 60,000 or less is more preferable. In the present disclosure, the weight average molecular weight is determined by gel permeation chromatography (in terms of polyethylene glycol), and specifically can be measured by the method described in Examples.

The content of component A in the immersion liquid composition of the present disclosure is preferably 0.001% by mass or more, and 0.005% by mass or more from the viewpoint of improving wettability and reducing residue on the wafer surface. More preferably, 0.01% by mass or more is still more preferred, and from the same viewpoint, 5% by mass or less is preferred, more preferably 3% by mass or less, even more preferably 2% by mass or less, even more preferably 1% by mass or less. , more preferably 0.5% by mass or less, and still more preferably 0.2% by mass or less. More specifically, the content of component A is preferably 0.001% by mass or more and 10% by mass or less, more preferably 0.005% by mass or more and 5% by mass or less, and 0.01% by mass or more and 2% by mass or less. is more preferably 0.01% by mass or more and 1% by mass or less, further preferably 0.01% by mass or more and 0.5% by mass or less, even more preferably 0.01% by mass or more and 0.2% by mass or less.

[Water (component B)]
The immersion liquid composition of the present disclosure contains water (hereinafter also referred to as "component B") in one or more embodiments. Examples of component B include ultrapure water, pure water, ion exchange water, distilled water, and the like. The content of component B in the immersion liquid composition of the present disclosure can be the remainder after removing component A and any optional components described below that are blended as necessary. Specifically, from the viewpoint of reducing residue on the wafer surface, the content of component B in the immersion liquid composition of the present disclosure is preferably 90% by mass or more, more preferably 95% by mass or more, and 99% by mass or more. is more preferable, and from the same viewpoint, it is preferably 99.99% by mass or less, more preferably 99.98% by mass or less, and even more preferably 99.97% by mass or less.

[Alkali agent (component C)]
In one or more embodiments, the immersion liquid composition of the present disclosure may further contain an alkaline agent (hereinafter also referred to as "component C") from the viewpoint of reducing residue on the wafer surface. In one or more embodiments, component C includes at least one selected from inorganic alkaline agents and organic alkaline agents. Examples of the inorganic alkali agent include ammonia; alkali metal hydroxides such as potassium hydroxide and sodium hydroxide; and the like. Examples of organic alkaline agents include hydroxyalkylamines, quaternary ammonium salts, and the like. Examples of hydroxyalkylamines include monoethanolamine, diethanolamine, triethanolamine, methylethanolamine, methyldiethanolamine, monopropanolamine, dipropanolamine, tripropanolamine, methylpropanolamine, methyldipropanolamine, and aminoethylethanol. Examples include amines. Examples of the quaternary ammonium salt include tetramethylammonium hydroxide and choline. Component C may be used alone or in combination of two or more.

From the viewpoint of reducing residue on the wafer surface, component C is preferably at least one selected from alkali metal hydroxides, ammonia, hydroxyalkylamines, and quaternary ammonium salts, and at least one selected from ammonia and hydroxylamine. One type is more preferable, and at least one type selected from ammonia and monoethanolamine is even more preferable.

The content of component C in the immersion liquid composition of the present disclosure is preferably 0.00001% by mass or more, more preferably 0.0001% by mass or more, from the viewpoint of both reducing residue on the wafer surface and achieving wafer wettability. , more preferably 0.001% by mass or more, and from the same point of view, 2.0% by mass or less is preferred, more preferably 0.3% by mass or less, even more preferably 0.1% by mass or less, and 0.07% by mass or less. It is more preferably at most 0.05% by mass, even more preferably at most 0.05% by mass. More specifically, the content of component C is preferably 0.00001% by mass or more and 2.0% by mass or less, more preferably 0.00001% by mass or more and 0.3% by mass or less, and 0.00001% by mass or more. It is more preferably 0.1% by mass or less, even more preferably 0.00001% by mass or more and 0.07% by mass or less, even more preferably 0.00001% by mass or more and 0.05% by mass or less.

[Organic acid (component D)]
In one or more embodiments, the immersion liquid composition of the present disclosure can further contain an organic acid (hereinafter also referred to as "component D") from the viewpoint of reducing residue on the wafer surface.
Component D includes, for example, citric acid, malic acid, gluconic acid, maleic acid, acetic acid, itaconic acid, succinic acid, tartaric acid, malonic acid, methanesulfonic acid, formic acid, lactic acid, hydroxyethylidene diphosphonic acid (HEDP), amino At least one selected from trimethylphosphonic acid and phosphonobutanetricarboxylic acid is mentioned. Among these, from the viewpoint of reducing residue on the wafer surface, at least one selected from citric acid, malic acid, maleic acid, tartaric acid, and HEDP is preferable as component D; malic acid, maleic acid, and HEDP are preferred. At least one selected from the following is more preferred. Component D may be used alone or in combination of two or more.

In one or more embodiments, the content of component D in the immersion liquid composition of the present disclosure is preferably 0.00001% by mass or more, and 0.00005% by mass or more from the viewpoint of reducing residue on the wafer surface. It is more preferably 0.0001% by mass or more, still more preferably 0.1% by mass or less, more preferably 0.05% by mass or less, and even more preferably 0.03% by mass or less. More specifically, the content of component D is preferably 0.00001% by mass or more and 0.1% by mass or less, more preferably 0.00005% by mass or more and 0.05% by mass or less, and 0.0001% by mass or more. More preferably, it is 0.03% by mass or less. When component D is a combination of two or more types, the content of component D refers to their total content.

The mass ratio (A/D) between component A and component D in the immersion liquid composition of the present disclosure is preferably 0.01 or more, more preferably 0.03 or more, from the viewpoint of reducing residue on the wafer surface. It is more preferably 0.05 or more, and from the same viewpoint, it is preferably 1,000,000 or less, more preferably 1,000 or less, and even more preferably 10 or less. More specifically, the mass ratio (A/D) is preferably 0.01 or more and 1,000,000 or less, more preferably 0.03 or more and 1,000 or less, and even more preferably 0.05 or more and 10 or less.

The immersion liquid composition of the present disclosure can contain other components as long as the effects of the present disclosure are not impaired. Other components include, for example, pH adjusters, chelating agents, preservatives, alcohols, and the like.

The immersion liquid composition of the present disclosure, in one or more embodiments, is substantially free of sodium. That is, the content of sodium in the immersion liquid composition of the present disclosure is 1 ppm or less. For example, the sodium content in the immersion liquid composition can be adjusted to 1 ppm or less by bringing the immersion liquid composition containing sodium into contact with a cation exchange resin to perform metal removal treatment.

The immersion liquid composition of the present disclosure can be produced by blending component A, component B, and, if desired, the above-mentioned optional components (component C, component D, and other components) by a known method. That is, in other aspects, the present disclosure relates to a method for producing an immersion liquid composition, which includes a step of blending at least component A and water. When component A is a combination of multiple types of polymers, component A can be obtained by blending multiple types of polymers. Here, "blending" includes mixing component A, water, and optional components mentioned above 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, and a wet ball mill. In the present disclosure, the blending amount of each component in the method for producing an immersion liquid composition can be the same as the content of each component in the immersion liquid composition of the present disclosure described above.

In the present disclosure, "the content of each component in the immersion liquid composition" refers to the content of each component at the time of using the immersion liquid composition, for example, when the immersion liquid composition is used for dipping a semiconductor substrate. .

In one or more embodiments of the present disclosure, the immersion liquid composition is manufactured as a concentrate, and may be diluted as necessary at the time of use. The concentrate of the immersion liquid composition can be used by diluting it with water so that the content of each component becomes the above-mentioned content at the time of use. In one or more embodiments, "in use" of a concentrate of an immersion liquid composition in the present disclosure refers to a state in which the concentrate of an immersion liquid composition is diluted.

From the viewpoint of reducing residue on the wafer surface, the pH of the immersion liquid composition of the present disclosure is preferably 1 or more, more preferably 2 or more, and from the same viewpoint, it is preferably 11 or less, more preferably 10 or less. , 9 or less is more preferable, and 5 or less is even more preferable. More specifically, the pH of the immersion liquid composition of the present disclosure is preferably 1 or more and 11 or less, more preferably 1 or more and 10 or less, even more preferably 1 or more and 9 or less, even more preferably 2 or more and 9 or less, and 2 or more. It is more preferably 5 or less. In the present disclosure, the pH of the immersion liquid composition is a value at 25° C., and can be measured using a pH meter, specifically, by the method described in Examples.

The immersion liquid composition of the present disclosure can be used in a semiconductor substrate manufacturing process in one or more embodiments. For example, the immersion liquid composition of the present disclosure is used, in one or more embodiments, for surface treatment of a polished semiconductor substrate. The immersion liquid composition of the present disclosure, in one or more embodiments, is not used as a cleaning or rinsing agent. Examples of the semiconductor substrate include a single crystal silicon wafer or a polysilicon wafer. That is, the immersion liquid composition of the present disclosure is, in one or more embodiments, an immersion liquid composition for single-crystal silicon wafers or polysilicon wafers.

[Method for manufacturing semiconductor substrate]
In other aspects, the present disclosure relates to a method for manufacturing a semiconductor substrate (hereinafter also referred to as "the method for manufacturing a semiconductor substrate of the present disclosure") including the following steps (1) and (2).
(1) A step of immersing a polished semiconductor substrate in the immersion liquid composition of the present disclosure (hereinafter also referred to as "immersion step").
(2) A step of cleaning the semiconductor substrate obtained in step (1) using a cleaning composition (hereinafter also referred to as a "cleaning step").

[Step (1): Soaking step]
Step (1) is a step (immersion step) of immersing the polished semiconductor substrate in the immersion liquid composition of the present disclosure. In one or more embodiments, step (1) may be a step of immersing a polished semiconductor substrate in the immersion liquid composition of the present disclosure and storing it until it is transported to step (2). Therefore, the immersion liquid composition of the present disclosure can be used, in one or more embodiments, to store polished semiconductor substrates.

In step (1), the temperature of the immersion liquid composition (immersion temperature) is preferably 10°C or higher, more preferably 13°C or higher, even more preferably 15°C or higher, and 18°C or higher, from the viewpoint of reducing residue on the wafer surface. It is more preferably higher than 0.degree. C., and from the same point of view, it is preferably 40.degree. C. or lower, more preferably 30.degree. C. or lower, and even more preferably 25.degree. C. or lower. More specifically, the immersion temperature is preferably 10°C or more and 40°C or less, preferably 13°C or more and 40°C or less, even more preferably 15°C or more and 40°C or less, even more preferably more than 18°C and 40°C or less, and 18°C It is more preferably more than 30°C, and even more preferably more than 18°C and not more than 25°C.

In step (1), the immersion time of the polished semiconductor substrate in the immersion liquid composition is preferably 0.1 minutes or more, more preferably 1 minute or more, and 5 minutes or more, from the viewpoint of reducing residue on the wafer surface. The above is more preferable, 10 minutes or more is even more preferable, and from the same viewpoint, 1440 minutes or less is preferable, 720 minutes or less is more preferable, 360 minutes or less is preferable, and 180 minutes or less is still more preferable. More specifically, the immersion time is preferably 0.1 minutes or more and 1440 minutes or less, more preferably 5 minutes or more and 720 minutes or less, even more preferably 10 minutes or more and 360 minutes or less, and even more preferably 10 minutes or more and 180 minutes or less. .

[Step (2): Washing step]
Step (2) is a step (cleaning step) of cleaning the semiconductor substrate obtained in step (1) using a cleaning composition. In one or more embodiments, the cleaning composition preferably does not substantially contain organic compounds from the viewpoint of reducing residue on the wafer surface. Here, when the cleaning composition is substantially free of organic compounds, the content of organic compounds in the cleaning composition is 0.1% by mass or less, preferably 0.05% by mass or less, more preferably It means that it is substantially 0% by mass. One embodiment of the cleaning composition used in step (2) includes, for example, an inorganic cleaning agent containing at least one selected from hydrogen peroxide, ammonia, hydrochloric acid, sulfuric acid, hydrofluoric acid, and ozone water.

The cleaning in step (2) is preferably inorganic cleaning from the viewpoint of reducing residue on the wafer surface, and for example, commonly used RCA cleaning or SCROD cleaning can be used.
Here, RCA cleaning basically includes SC1 cleaning used to remove particles attached to the wafer surface and SC2 cleaning used to remove heavy metals attached to the wafer surface, and as necessary. This includes SPM cleaning, which is used to remove organic matter adhering to the wafer surface, and DHF cleaning, which is used to remove unnecessary oxide films from the wafer surface. SCROD cleaning is used to remove particles and heavy metals. Examples of cleaning methods for RCA cleaning and SCROD cleaning include immersion cleaning and single wafer cleaning.
In SC1 cleaning, for example, a cleaning composition consisting of ammonia, hydrogen peroxide, and water is used. In the SC2 cleaning, for example, a cleaning composition consisting of hydrochloric acid, hydrogen peroxide, and water is used. In SPM cleaning, for example, a cleaning composition consisting of sulfuric acid and hydrogen peroxide is used. In DHF cleaning, for example, a cleaning composition consisting of hydrofluoric acid and water is used. SCROD cleaning uses ozone water and hydrofluoric acid.
After each washing step of the above-mentioned washing, a step of rinsing with water and drying may be included.

In one or more embodiments, the semiconductor substrate manufacturing method of the present disclosure can include a step of polishing the semiconductor substrate using a polishing liquid composition (polishing step) before the dipping step. In one or more embodiments, the polishing step is preferably a final polishing step and/or a final polishing step. One embodiment of the polishing liquid composition includes a polishing liquid composition containing abrasive grains such as silica.

Hereinafter, the present disclosure will be explained in more detail with reference to Examples, but these are merely illustrative and the present disclosure is not limited to these Examples.

1. Preparation of Polymers A1 to A6 (Component A or Non-Component A) The following raw materials were used to prepare Polymers A1 to A6 shown in Table 1.

<Monomer a1>
MAA: Methacrylic acid (manufactured by Tokyo Chemical Industry Co., Ltd.)
AA: Acrylic acid (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.)

<Monomer a2>
(Monomer a2-1)
Methoxypolyethylene glycol allyl ether (average molecular weight 1500, average number of added moles of EO 32), Uniox PKA-5010 (manufactured by NOF Corporation)
(Monomer a2-2)
Polyethylene glycol-3-methyl-3-butenyl ether (average number of added moles of EO 50)
(Monomer a2-3)
Polyethylene glycol allyl ether (EO average added mole number 25)

<Polymerization chain transfer agent>
2-Mercaptoethanol (manufactured by Tokyo Chemical Industry Co., Ltd.)
β-Mercaptopropionic acid (manufactured by Tokyo Chemical Industry Co., Ltd.)
<Polymerization chain transfer agent and solvent>
1,2-propanediol (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.)
<Polymerization initiator>
Ammonium peroxodisulfate (ammonium persulfate) (manufactured by Nacalai Tesque Co., Ltd.)
Hydrogen peroxide solution (30-35.5% by mass aqueous solution, manufactured by Nacalai Tesque Co., Ltd.)
Sodium peroxodisulfate (manufactured by Nacalai Tesque Co., Ltd.)
<Neutralizing agent>
Sodium hydroxide (48% by mass NaOH, manufactured by Asahi Glass Co., Ltd.)
Note that component C does not include sodium hydroxide used as a neutralizing agent.

[Production example of polymer A1]
90.5 g (5.0 mol) of water was placed in a reaction vessel equipped with a stirrer, and the atmosphere was replaced with nitrogen while stirring, and the temperature was raised to 75° C. in a nitrogen atmosphere. MAA: 63.7 g (0.65 mol), monomer a2-1: 525 g (0.35 mol) (mass ratio = 11/89, molar ratio = 65/35), water: 161 g (8.9 mol). The mixed solution and 37.0 g of a 10% by mass ammonium persulfate aqueous solution were each simultaneously added dropwise to the reaction system over 2 hours. Next, 14.8 g of a 10% by mass ammonium persulfate aqueous solution was added dropwise over 30 minutes, and the mixture was aged at the same temperature (75° C.) for 3 hours. After aging, add 108g of 48% by mass aqueous sodium hydroxide solution to neutralize, then fill the column with 100ml of cation exchange resin (ion exchange resin: DIAION SK1BH manufactured by Mitsubishi Chemical), and add the neutralized product after aging. Polymer A1 with a sodium content of 1 ppm or less (30 mass% Aqueous solution) was obtained.

[Production example of polymer A2]
234 g (13.0 mol) of water and 546 g (0.24 mol) of monomer a2-2 were placed in a reaction vessel equipped with a stirrer, and the atmosphere was replaced with nitrogen while stirring, and the temperature was raised to 65°C in a nitrogen atmosphere to add peroxide. 8.6 g of hydrogen water was added dropwise. Next, a mixture of 54.4 g (0.76 mol) of AA and 45.6 g (2.5 mol) of water, 8.0 g of β-mercaptopropionic acid, 3.3 g of L-ascorbic acid, and A mixed solution of 38.8 g of water was simultaneously added dropwise to the reaction system over 2 hours. Thereafter, it was aged for 1 hour at the same temperature (65°C). After the ripening, 62.9 g of 48% by mass aqueous sodium hydroxide solution was added to neutralize it, and then 100 ml of cation exchange resin (ion exchange resin: DIAION SK1BH manufactured by Mitsubishi Chemical) was filled in the column. Polymer A2 (30% by weight) with a sodium content of 1 ppm or less was obtained by diluting the hydrate with water to a solid concentration of 30% by mass and subjecting it to ion exchange treatment under conditions such that the space velocity SV value was 4.0. % aqueous solution) was obtained (AA/monomer a2-2 mass ratio = 9/91, molar ratio = 76/24).

[Production example of polymer A3]
In a reaction vessel equipped with a stirrer, water: 193 g (10.7 mol), 1,2-propanediol: 295 g (3.9 mol), AA: 5.0 g (0.069 mol), monomer a2-3: 150 g (0 .13 mol) was charged, the atmosphere was replaced with nitrogen while stirring, and the temperature was raised to 85° C. in a nitrogen atmosphere. A mixed solution of 49.7 g (0.69 mol) of AA, 150 g (0.13 mol) of monomer a2-3, and 50.3 g (2.8 mol) of water, and 5. sodium peroxodisulfate. A mixed solution of 3 g and 21.2 g of water was simultaneously added dropwise to the reaction system over 75 minutes. Next, a mixed solution of 45.1 g (0.63 mol) of AA, 4.8 g of sodium peroxodisulfate, and 30.3 g of water was simultaneously added dropwise to the reaction system over 135 minutes. Thereafter, it was aged at the same temperature (85°C) for 3 hours. After the aging, 52.2g of 48% by mass aqueous sodium hydroxide solution was added to neutralize, and then 100ml of cation exchange resin (ion exchange resin: DIAION SK1BH manufactured by Mitsubishi Chemical) was filled in the column. Polymer A3 (20%) with a sodium content of 1 ppm or less was obtained by diluting the hydrate with water to a solid concentration of 20% by mass and subjecting it to ion exchange treatment under conditions such that the space velocity SV value was 4.0. A mass% solution) was obtained (AA/monomer a2-3 mass ratio = 25/75, molar ratio = 84/16).

[Polymer A4]
Acrylic acid/polyethylene glycol acrylic ester (EO average added mole number 5, weight average molecular weight 3,000, manufactured by Kao Corporation)
[Polymer A5]
Polyacrylic acid (weight average molecular weight 20,000, manufactured by Nacalai Tesque)
[Polymer A6]
Polyethylene glycol (weight average molecular weight 20,000, manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.)

[Measurement of weight average molecular weight]
The weight average molecular weight of the polymer was measured using gel permeation chromatography (hereinafter also referred to as "GPC") under the following conditions. The measurement results are shown in Table 1.
[GPC conditions]
Column: G4000PWXL+G2500PWXL (manufactured by Tosoh Corporation)
Eluent: 0.2M phosphate buffer/CH ₃ CN = 9/1 (volume ratio)
Flow rate: 1.0mL/min
Column temperature: 40℃
Detection: RI
Sample size: 0.5mg/mL
Standard substance: polyethylene glycol equivalent

2. Preparation of dipping liquid composition The components shown in Tables 2 and 3 were mixed to prepare dipping liquid compositions for Examples 1 to 10 and Comparative Examples 1 to 6. Citric acid and ammonia were used for pH adjustment. The content of each component in Tables 2 and 3 is the content (% by mass, effective content) of each component when the immersion liquid composition is used. The sodium content in the prepared dipping liquid compositions of Examples 1 to 10 and Comparative Example 3 was 1 ppm or less.

In the preparation of the immersion liquid composition, the polymers (component A or non-component A) used were as described above. For component B, component C, and component D, the following were used.
(Component B)
Water: Ultrapure water (component C)
NH ₃ : Ammonia [manufactured by Kanto Kagaku Co., Ltd., 29% by mass ammonia water]
MEA: Monoethanolamine [manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.]
(Component D)
Citric acid [manufactured by Fuso Chemical Industry Co., Ltd.]
Malic acid [manufactured by Fuso Chemical Industry Co., Ltd.]
Maleic acid [manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.]

[pH of immersion liquid composition]
The pH value of the immersion liquid composition at 25°C is the value measured using a pH meter (manufactured by Toa Denpa Kogyo Co., Ltd., "HM-30G"). This is the number after minutes.

[Sodium content in immersion liquid composition]
The sodium content in the immersion liquid composition was determined using an internal standard method using an ICP mass spectrometer (manufactured by Agilent, model name: 7700s, ICP-MS), and subtracting the blank value from the simultaneous operation. The content was determined.

3. Evaluation by immersion [removability by immersion (Si elution amount)]
Using the following silicon wafer for evaluation, the removability of residue on the wafer surface by immersion was evaluated as follows.
<Silicon wafer for evaluation>
Single-crystal silicon wafer [silicon single-sided mirror wafer with a diameter of 200 mm, conductivity type: P, crystal orientation: 100, resistivity: 0.1 Ω·cm or more and less than 100 Ω·cm]
A SiO ₂ film of 4400 Å was deposited on a polysilicon wafer [silicon single-sided mirror wafer with a diameter of 200 mm, conductivity type: P, crystal orientation: 100, resistivity: 0.1 Ω·cm or more and less than 100 Ω·cm by plasma CVD method. , followed by a wafer on which a polysilicon film of 8000 Å was deposited using the same plasma CVD method]
<Evaluation method of removability by immersion>
(1) A silicon wafer for evaluation cut into 4 cm x 4 cm was subjected to silicon water repellent treatment with a 1% by mass hydrofluoric acid aqueous solution.
(2) Silica particles (colloidal silica, average secondary particle diameter 70 nm, "PL-3" manufactured by Fuso Chemical Co., Ltd.), HEC (weight average molecular weight 800,000, "CF-V" manufactured by Sumitomo Seika Co., Ltd.), ammonia and ultrapure water were mixed to prepare a polishing liquid composition. The content of each component in the polishing liquid composition is 0.3% by mass of silica particles, 0.015% by mass of HEC, 0.015% by mass of ammonia, and the remainder is ultrapure water. The pH of the polishing liquid composition was 10.7.
(3) A silicon wafer treated with silicon water repellent was immersed in 100 mL of the prepared polishing liquid composition (temperature: 25° C.) for 1 minute.
(4) The silicon wafer was pulled out of the polishing liquid composition and washed with running water for 5 seconds.
(5) A washed silicon wafer (surface area: 0.0016 m ² ) was immersed in 0.1 L of each of the prepared immersion liquid compositions (temperature: 25° C.) for 30 minutes.
(6) The silicon wafer was gently taken out from the immersion liquid composition, and the Si concentration (ppb) in the immersion liquid composition was measured using an inductively coupled plasma mass spectrometer (ICP-MS, manufactured by Agilent, 7700S). . The measurement results are shown in Tables 2 and 3. Note that Table 2 shows the evaluation results of the removability of the residue on the surface of the single crystal silicon wafer, and Table 3 shows the evaluation results of the removability of the residue on the surface of the polysilicon wafer. It can be determined that the higher the Si concentration in the immersion liquid composition, the more residue is removed from the wafer surface, and the more the residue on the wafer surface is reduced.

[Wettability by immersion]
When the wettability of each immersion liquid composition to silicon wafers was visually confirmed, the immersion liquid compositions of Examples 1 to 10 were compared to systems containing no component A (water only and Comparative Examples 1 to 4). It was confirmed that the wettability to silicon wafers was improved.

4. Evaluation of surface defects after polishing process, dipping process and cleaning process [Cleanliness (LPD)]
Using the silicon wafer for evaluation described below, surface defects (LPD) on the wafer surface were evaluated as follows.
<Silicon wafer for evaluation>
Single-crystal silicon wafer [silicon single-sided mirror wafer with a diameter of 200 mm, conductivity type: P, crystal orientation: 100, resistivity: 0.1 Ω·cm or more and less than 100 Ω·cm]
A SiO ₂ film of 4400 Å was deposited on a polysilicon wafer [silicon single-sided mirror wafer with a diameter of 200 mm, conductivity type: P, crystal orientation: 100, resistivity: 0.1 Ω·cm or more and less than 100 Ω·cm by plasma CVD method. , followed by a wafer on which a polysilicon film of 8000 Å was deposited using the same plasma CVD method]
<Final polishing process>
Silica particles (colloidal silica, average secondary particle diameter 70 nm, "PL-3" manufactured by Fuso Chemical Co., Ltd.), HEC (weight average molecular weight 800,000, "CF-V" manufactured by Sumitomo Seika Co., Ltd.), ammonia and ultra-pure A polishing liquid composition for final polishing was prepared by mixing water. The content of each component in the polishing liquid composition is 0.3% by mass of silica particles, 0.015% by mass of HEC, 0.015% by mass of ammonia, and the remainder is ultrapure water. The pH of the polishing liquid composition for final polishing was 10.5.
Using the prepared final polishing liquid composition, a silicon wafer for evaluation was subjected to final polishing under the following final polishing conditions. Prior to the final polishing, the silicon wafer for evaluation was subjected to rough polishing using a commercially available polishing liquid composition. The surface roughness (Haze) of the silicon wafer subjected to final polishing after rough polishing was 5.13 ppm (DWO) and 9.77 ppm (DNN). The measured value of Haze was measured using the same method as for measuring surface defects, which will be described later.
(Final polishing conditions)
Grinding machine: Single-sided 8-inch grinding machine "GRIND-X SPP600s" (manufactured by Okamoto Kosaku)
Polishing pad: Suede pad (manufactured by Toray Cortex, Asker hardness: 64, thickness: 1.37mm, nap length: 450um, opening diameter: 60um)
Silicon wafer polishing pressure: 100g/cm ²
Surface plate rotation speed: 60 rpm
Polishing time: 5 minutes Supply rate of polishing liquid composition: 150g/cm ²
Temperature of polishing liquid composition: 23°C
Carrier rotation speed: 62rpm
<Soaking process>
A silicon wafer having a diameter of 200 mm after the polishing process was immersed in 5 L of each of the prepared immersion liquid compositions (temperature: 25° C.) for 30 minutes.
<Cleaning process>
After the immersion process, the silicon wafer was subjected to ozone cleaning and dilute hydrofluoric acid cleaning as described below. In ozone cleaning, an aqueous solution containing 20 ppm of ozone was sprayed from a nozzle at a flow rate of 1 L/min toward the center of the silicon wafer rotating at 600 rpm for 3 minutes. At this time, the temperature of the ozonated water was set to room temperature. Next, dilute hydrofluoric acid cleaning was performed. In dilute hydrofluoric acid cleaning, an aqueous solution containing 0.5% by mass ammonium hydrogen fluoride (special grade, Nacalai Tesque Co., Ltd.) is sprayed from a nozzle at a flow rate of 1 L/min toward the center of the silicon wafer rotating at 600 rpm for 6 seconds. did. A total of two sets of the above ozone cleaning and dilute hydrofluoric acid cleaning were performed as one set, and finally spin drying was performed. In spin drying, the silicon wafer was rotated at 1,500 rpm.
<Measurement of surface defects (LPD)>
Measuring equipment: Surface roughness measuring device “Surfscan SP1-DLS” (manufactured by KLA Tencor)
Evaluation: Evaluation was made by measuring the number of particles having a particle size of 45 nm or more on the wafer surface after cleaning. The evaluation results for surface defects (LPD) indicate that the smaller the value, the fewer surface defects and the better the cleanliness. Surface defects (LPD) were measured on three silicon wafers, and the average value was calculated for each. Table 2 shows the evaluation results for surface defects (LPD) on the surface of single crystal silicon wafers, and Table 3 shows the evaluation results for surface defects (LPD) on the surface of polysilicon wafers. In Table 2, the results of Examples 1 to 9 and Comparative Examples 1 to 4 are relative values with Comparative Example 1 as 100. In Table 3, the results of Example 10 and Comparative Examples 5 to 6 are shown as relative values with Comparative Example 6 as 100.

As shown in Table 2, Examples 1 to 9 using the immersion liquid composition containing Polymer A (Component A) were polished less than Comparative Examples 1 to 4 that did not contain Polymer A (Component A). The ability to remove residue on the surface of single-crystal silicon wafers was improved. Furthermore, surface defects (LPD) were reduced.
As shown in Table 3, Example 10, which used the immersion liquid composition containing Polymer A (Component A), was more effective than Comparative Examples 5 and 6, which did not contain Polymer A (Component A). The ability to remove residue on the silicon wafer surface was improved. Furthermore, surface defects (LPD) were reduced.

According to the present disclosure, residues on the surface of a polished silicon wafer can be reduced, so silicon wafers with reduced surface defects can be manufactured, which is useful in mass production of semiconductor substrates.

Claims (11)

An immersion liquid composition for semiconductor substrates comprising the following polymer A (component A) ,
An immersion liquid composition, wherein the immersion liquid composition for a semiconductor substrate is an immersion liquid composition for a single crystal silicon wafer or a polysilicon wafer .
Polymer A: A polymer or a salt thereof containing a structural unit a1 derived from a monomer a1 represented by the following formula (I) or its anhydride, and a structural unit a2 derived from a monomer a2 represented by the following formula (II).

[In formula (I), R ¹ , R ² and R ³ each independently represent a hydrogen atom, a methyl group, or -(CH ₂ ) _p COOM ² , and M ¹ and M ² each independently represent a hydrogen atom , an alkali metal, an alkaline earth metal (1/2 atom), or an ammonium group, and p is an integer of 0 to 2. ]

[In formula (II), R ⁴ and R ⁵ each independently represent a hydrogen atom or a methyl group, r represents an integer of 0 to 2, and AO represents an alkyleneoxy group having 2 to 18 carbon atoms. , m is the average number of added moles of AO and is 1 to 300, and X is a hydrogen atom or an alkyl group having 1 to 18 carbon atoms. ] The immersion liquid composition according to claim 1, wherein the molar ratio (a1/a2) of the structural unit a1 to the structural unit a2 in all the structural units of component A is 50/50 or more and 99/1 or less. The immersion liquid composition according to claim 1 or 2, wherein the total content of the structural unit a1 and the structural unit a2 in all the structural units of component A is 85 mol% or more. 4. The immersion liquid composition according to claim 1, wherein component A has a weight average molecular weight of 5,000 or more and 100,000 or less. The immersion liquid composition according to any one of claims 1 to 4, having a sodium content of 1 ppm or less. The immersion liquid composition according to any one of claims 1 to 5 , further comprising an alkaline agent (component C). The immersion liquid composition according to claim 1, wherein the content of component A is 0.001% by mass or more and 10% by mass or less . The immersion liquid composition according to any one of claims 1 to 7 , having a pH of 1 or more and 5 or less. The immersion liquid composition according to any one of claims 1 to 8 , further comprising an organic acid (component D). A method for manufacturing a semiconductor substrate, including the following steps (1) and (2).
(1) A step of immersing a polished semiconductor substrate in the immersion liquid composition according to any one of claims 1 to 9 .
(2) A step of cleaning the semiconductor substrate obtained in step (1) using a cleaning composition. The semiconductor substrate according to claim 10 , wherein the cleaning composition used in step (2) is an inorganic cleaning agent containing at least one selected from hydrogen peroxide, ammonia, hydrochloric acid, sulfuric acid, hydrofluoric acid, and ozone water. manufacturing method.