JP7316112B2 - Substrate cleaning method - Google Patents

Description

The present disclosure relates to a substrate cleaning method and a semiconductor device substrate manufacturing method.

2. Description of the Related Art In recent years, semiconductor devices such as semiconductor integrated circuits have been miniaturized along with improvement in processing capability. As miniaturization progresses, high accuracy of flatness is required in each layer of the substrate. Furthermore, from the standpoint of production efficiency, etc., it has been required to simultaneously planarize a plurality of types of surfaces having different hardnesses and properties on which wirings and the like are drawn.

Chemical mechanical polishing (CMP) is generally performed as a technique for ensuring the flatness of substrates for semiconductor devices. In CMP, a substrate surface is polished and planarized using a polishing pad while supplying an abrasive (slurry) containing abrasive grains. Silica slurries are widely used as abrasives, but cerium oxide particle (ceria) slurries are also used. Silica slurry is mainly used for polishing a substrate surface having a metal portion such as copper and a silicon dioxide (SiO ₂ ) portion, while ceria slurry mainly has an SiO ₂ portion and a silicon nitride (Si ₃ N ₄ ) portion. It is used for polishing the substrate surface. After CMP using silica slurry or ceria slurry, cleaning is necessary to remove polishing dust remaining on the substrate surface and foreign matter (particles) derived from abrasive grains.

For example, Patent Literature 1 proposes a cleaning liquid containing an anionic surfactant, water and a pH adjuster for cleaning a substrate after CMP processing.

JP 2017-103466 A

After CMP using ceria slurry, cleaning with hydrofluoric acid is usually performed for the purpose of removing ceria, which is polishing abrasive grains remaining on the substrate surface. On the other hand, in recent years, in the field of semiconductor devices, there is a tendency to narrow the wiring width for the purpose of miniaturization, so the influence of scratches and surface roughening of the underlying thermal oxide film such as silicon dioxide is increasing. Furthermore, hydrofluoric acid cleaning causes problems such as the generation of scratches and surface roughness due to its excessive solubility in thermal oxide films, which affects the post-cleaning process and reduces the yield and quality of semiconductor devices. I am inviting you. Therefore, instead of hydrofluoric acid, there is a demand for a cleaning agent that is excellent in cleaning property against ceria remaining on the substrate surface without lowering the flatness. However, the cleaning compositions disclosed in the above-mentioned patent documents are not sufficiently cleansing of ceria remaining on the surface of a substrate for semiconductor devices, the surface of which is partly made of silicon oxide.

Accordingly, the present disclosure provides a substrate cleaning method and a semiconductor device substrate manufacturing method that are excellent in cleaning performance against ceria remaining on the substrate surface of a semiconductor device substrate partly made of silicon oxide.

The present disclosure, in one aspect, relates to a substrate cleaning method including the following steps (1) and (2).
(1) A step of cleaning a substrate to be cleaned with a cleaning composition having a pH of 5 or less and containing water and a compound having two or more carboxyl groups in the molecule (component A).
(2) A step of cleaning the substrate obtained in step (1) with a cleaning composition having a pH of 10 or higher containing an alkaline agent and water.
However, the substrate to be cleaned is a semiconductor device substrate having a part of silicon oxide surface which is polished with a polishing composition containing cerium oxide particles.

In one aspect, the present disclosure relates to a method for manufacturing a semiconductor device substrate, including the step of cleaning a substrate to be cleaned using the cleaning method of the present disclosure.

According to the present disclosure, in one embodiment, it is possible to provide a method for cleaning a substrate that is excellent in cleaning performance against ceria remaining on the surface of a semiconductor device substrate whose surface is partly made of silicon oxide.

The present disclosure includes a compound (component A) having two or more carboxyl groups in the molecule of a substrate for a semiconductor device, the surface of which is partly made of silicon oxide and which has been polished using a polishing composition containing ceria. It is based on the knowledge that ceria remaining on the substrate surface can be efficiently washed by washing with an acidic cleaning composition and then washing with an alkaline cleaning composition.

That is, in one aspect, the present disclosure relates to a substrate cleaning method (hereinafter also referred to as “cleaning method of the present disclosure”) including the following steps (1) and (2).
(1) A step of cleaning a substrate to be cleaned with a cleaning composition having a pH of 5 or less and containing water and a compound having two or more carboxyl groups in the molecule (component A).
(2) A step of cleaning the substrate obtained in step (1) with a cleaning composition having a pH of 10 or higher containing an alkaline agent and water.
However, the substrate to be cleaned is a semiconductor device substrate having a part of silicon oxide surface which is polished with a polishing composition containing cerium oxide particles.

Although the details of the action mechanism of the effect in the cleaning method of the present disclosure are partly unknown, it is presumed as follows.
After CMP using the ceria slurry, ceria, which is abrasive grains, remains on the substrate surface. In the cleaning method of the present disclosure, first, a substrate to which ceria has adhered is cleaned with a cleaning composition having a pH of 5 or less containing a compound (component A) having two or more carboxyl groups in the molecule, thereby cleaning the substrate. Component A is adsorbed on the attached ceria. Then, washing with a cleaning composition containing an alkaline agent and having a pH of 10 or higher dissociates the carboxylic acid groups of component A, presumably promoting the removal of ceria from the substrate surface.
However, the present disclosure may not be construed as being limited to this mechanism.

Details of the steps (1) and (2) are described below.

[Step (1): Acid washing step]
In step (1) of the cleaning method of the present disclosure, the substrate to be cleaned is treated with a cleaning composition having a pH of 5 or less containing water and a compound having two or more carboxyl groups in the molecule (component A) (hereinafter referred to as "the (also referred to as "acidic detergent composition"). Step (1), in one or more embodiments, can include the step of contacting the substrate to be cleaned with the acidic cleaning composition of the present disclosure. In one or more embodiments, step (1) can further include the step of contacting the substrate to be cleaned with the acidic cleaning composition of the present disclosure, rinsing with water, and drying.

<Substrate to be cleaned>
In one or a plurality of embodiments, the substrate to be cleaned is a semiconductor device substrate having a surface partially made of silicon oxide, which has been polished using a polishing composition containing cerium oxide particles (ceria). A semiconductor device substrate is a substrate used in manufacturing a semiconductor device substrate in one or more embodiments. A semiconductor device substrate having a part of the surface made of silicon oxide includes, for example, a silicon substrate having a silicon oxide film.

<Detergent composition used in step (1) (acidic detergent composition)>
The pH of the acidic detergent composition of the present disclosure during cleaning is 5 or less, preferably 4 or less, more preferably 3.5 or less, from the viewpoint of improving cleaning performance. In the present disclosure, the “pH during cleaning” is the pH at 25° C. during use of the cleaning composition, which can be measured using a pH meter. Specifically, it can be measured by the method described in Examples. Adjustment of pH includes, for example, inorganic acids such as nitric acid and sulfuric acid; organic acids such as oxycarboxylic acids, polyvalent carboxylic acids, aminopolycarboxylic acids, and amino acids; and metal salts and ammonium salts thereof, ammonia, sodium hydroxide, Basic substances such as potassium hydroxide and amines;

Component A contained in the acidic detergent composition of the present disclosure is, in one or more embodiments, a compound having two or more carboxyl groups in the molecule. Component A may be used alone or in combination of two or more.
One embodiment of Component A includes, for example, tartaric acid, citric acid, and the like.
Component A may be a polymer, and in one embodiment when Component A is a polymer, for example, polyacrylic acid; a structural unit a1 derived from an unsaturated carboxylic acid, and a functional group other than a carboxylic acid group (hereinafter also simply referred to as "a copolymer containing a structural unit a1 and a structural unit a2"); and the like. When the component A is polyacrylic acid, when the acidic detergent composition of the present disclosure is stored at a low temperature of room temperature or lower for a long period of time (for example, one month), the transmittance of the acidic detergent composition decreases and becomes cloudy. tend to On the other hand, when the component A is a copolymer containing the structural unit a1 and the structural unit a2, it is possible to suppress a decrease in transmittance of the acidic detergent composition even after long-term storage. Therefore, when component A is a polymer, component A is preferably a copolymer containing structural unit a1 and structural unit a2 from the viewpoint of storage stability. Examples of the unsaturated carboxylic acid, which is a monomer forming the structural unit a1, include at least one selected from acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, and salts thereof. Examples of the monomer forming the structural unit a2 include monomers having a phosphoric acid group, a phosphonic acid group, a sulfonic acid group and an oxyalkyl group in the molecule, specifically 2-acrylamido-2-methylpropane sulfonic acid, ethylene glycol allyl ether, (2-hydroxyethyl methacrylate) phosphate and the like. From the viewpoint of storage stability, the copolymer containing the structural unit a1 and the structural unit a2 includes a structural unit a1 derived from an unsaturated carboxylic acid, and a phosphate group, a phosphonic acid group, a sulfonic acid group and an oxy group in the molecule. A copolymer containing a structural unit a2 derived from a monomer having an alkyl group is preferred, and acrylic acid/2-acrylamido-2-methylpropanesulfonic acid copolymer (AA/AMPS) and acrylic acid/ethylene glycol allyl ether copolymer At least one selected from coalescence (AA/PEGAE) is more preferable.

When component A is a copolymer containing structural unit a1 and structural unit a2, the content (parts by moles) of structural unit a1 in all structural units of component A is 10 mol parts or more is preferable, 50 mol parts or more is more preferable, and 80 mol parts or more is still more preferable, and from the same viewpoint, 99 mol parts or less is Preferably, 95 mol parts or less is more preferable, and 90 mol parts or less is even more preferable. More specifically, the content (mol parts) of the structural unit a1 is preferably 10 mol parts or more and 99 mol parts or less, and 50 mol parts or more and 95 mol parts, relative to all the structural units (100 mol parts) of component A. Parts or less is more preferable, and 80 to 90 molar parts is even more preferable.

When component A is a copolymer containing structural unit a1 and structural unit a2, the content (parts by moles) of structural unit a2 in all structural units of component A is 1 mol part or more is preferable, 3 mol parts or more is more preferable, 5 mol parts or more is still more preferable, and from the same viewpoint, 90 mol parts or less is Preferably, 50 mol parts or less is more preferable, and 10 mol parts or less is even more preferable. More specifically, the content (mol parts) of the structural unit a2 is preferably 1 mol part or more and 90 mol parts or less, and 3 mol parts or more and 50 mol parts, with respect to all the structural units (100 mol parts) of the component A. Part or less is more preferable, and 5 to 10 mol parts is even more preferable.

When component A is a copolymer containing structural unit a1 and structural unit a2, the molar ratio (a1/a2) of structural unit a1 to structural unit a2 in all structural units of component A is important for storage stability and washing. From the viewpoint of improving properties, 10/90 or more is preferable, 50/50 or more is more preferable, 60/40 or more is still more preferable, 90/10 or more is still more preferable, and from the same viewpoint, 99/1 or less is preferable. , 98/2 or less, more preferably 97/3 or less, and even more preferably 95/5 or less. More specifically, the molar ratio (a1/a2) is preferably 10/90 or more and 99/1 or less, more preferably 50/50 or more and 98/2 or less, and even more preferably 60/40 or more and 98/2 or less. 90/10 or more and 95/5 or less are more preferable.

When component A is a copolymer containing structural unit a1 and structural unit a2, the total content (mole parts) of structural units a1 and a2 in all structural units of component A is From the viewpoint, it is preferably 10 mol parts or more, more preferably 50 mol parts or more, and even more preferably 80 mol parts or more, relative to all structural units (100 mol parts) of component A.

When component A is a copolymer containing structural units a1 and a2, component A may further contain structural units other than structural units a1 and a2. Other structural units include, for example, hydrophobic monomers containing a benzene ring, an alkyl chain, or the like in the molecule.

When component A is a copolymer containing structural unit a1 and structural unit a2, component A can be obtained by a known method such as, for example, polymerizing a monomer mixture containing monomer a1 and monomer a2 by solution polymerization. can. 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; . As a polymerization initiator used for polymerization, a known radical initiator can be used, and examples thereof include ammonium persulfate. A chain transfer agent can be further used in the polymerization, and examples thereof include thiol chain transfer agents such as 2-mercaptoethanol and β-mercaptopropionic acid. In the present disclosure, the content of each structural unit in all structural units of component A can be regarded as the ratio of the amount of each monomer used to the total amount of monomers used for polymerization.

When component A is a copolymer containing structural units a1 and a2, the arrangement of each structural unit constituting component A may be random, block, or graft.

When component A is a polymer, the weight average molecular weight of component A is preferably 1,000 or more, more preferably 5,000 or more, still more preferably 10,000 or more, from the viewpoint of improving washability. From the viewpoint, it is preferably 1,000,000 or less, more preferably 100,000 or less, and even more preferably 50,000 or less. More specifically, the weight average molecular weight of component A is preferably 1,000 or more and 1,000,000 or less, more preferably 5,000 or more and 100,000 or less, and even more preferably 10,000 or more and 50,000 or less. . In the present disclosure, the weight-average molecular weight of component A is determined by gel permeation chromatography (converted to polyethylene glycol), and can be specifically measured by the method described in Examples.

The content of component A during cleaning with the acidic detergent composition of the present disclosure is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, more preferably 0.1% by mass, from the viewpoint of improving cleaning performance. The above is more preferable, and from the viewpoint of improving the cleaning property and reducing the wastewater treatment load, the content is preferably 1% by mass or less, more preferably 0.75% by mass or less, and even more preferably 0.5% by mass or less. More specifically, the content of Component A is preferably 0.01% by mass or more and 1% by mass or less, more preferably 0.05% by mass or more and 0.75% by mass or less, and 0.1% by mass or more and 0.1% by mass or less. 5% by mass or less is more preferable. When component A is a combination of two or more, the content of component A is their total content.

As the water contained in the acidic detergent composition of the present disclosure, ion-exchanged water, RO water, distilled water, pure water, and ultrapure water can be used. The content of water during washing with the detergent composition of the present disclosure can be the remainder after removing the component A of the present disclosure and optional components described later that are blended as necessary.

The acidic detergent composition of the present disclosure can contain other components, if necessary, in addition to component A and water described above. Other components include acids other than component A, pH adjusters, chelating agents, solubilizers, preservatives, rust inhibitors, bactericides, antibacterial agents, silicone antifoaming agents, antioxidants, esters, and alcohols. and the like. The content of other components during cleaning with the acidic detergent composition of the present disclosure is preferably 0% by mass or more and 2% by mass or less, and 0% by mass or more and 1.5% by mass, from the viewpoint of not impairing the effects of the present disclosure. The following are more preferable, and 0% by mass or more and 1% by mass or less are even more preferable.

The acidic detergent composition of the present disclosure can be produced, for example, by blending the component A, water and, if necessary, other components by a known method. Accordingly, the present disclosure relates, in one aspect, to a method of making a cleaning composition comprising combining at least said component A and water. In the present disclosure, "blending" includes mixing component A, water and optionally other ingredients simultaneously or in any order. In the method for producing the acidic detergent composition of the present disclosure, the blending amount of each component can be the same as the content of each component of the acidic detergent composition of the present disclosure described above.

In the present disclosure, the “content of each component during cleaning of the cleaning composition” is, in one or more embodiments, used in the cleaning step, i.e., at the time of starting use for cleaning (at the time of use) means the content of each component of the detergent composition in

The acidic detergent composition of the present disclosure may be prepared as a concentrate in which the amount of water is reduced to the extent that separation, precipitation, etc. do not occur and storage stability is not impaired. The concentrate of the acidic detergent composition of the present disclosure is preferably a concentrate with a dilution rate of 10 times or more and 100 times or less from the viewpoint of transportation and storage and storage stability. The concentrate of the acidic detergent composition of the present disclosure can be used by diluting with water so that each component has the above-described content (that is, the content at the time of washing) at the time of use. Concentrates of acidic detergent compositions of the present disclosure can also be used by adding each component separately at the time of use. In the present disclosure, "at the time of use" or "at the time of washing" of the concentrate of the cleaning composition refers to the state in which the concentrate of the cleaning composition is diluted. When the acidic cleaning composition of the present disclosure is a concentrate, the cleaning method of the present disclosure can further include a dilution step of diluting the concentrate of the acidic cleaning composition.

Examples of the cleaning method of step (1) include brush cleaning and cleaning using a pad.
In one or more embodiments, brush cleaning is cleaning the substrate surface by pressing a cleaning brush against the substrate surface and moving the substrate and the cleaning brush relative to each other while supplying a cleaning agent composition to the substrate surface. The method. Examples of cleaning brushes include roll brushes and pencil brushes.
Cleaning using a pad, in one or more embodiments, refers to pressing the pad against the substrate surface and moving the substrate and the pad relatively while supplying a cleaning composition between the substrate and the pad. This is a method for cleaning the substrate surface. Examples of the pad include polyurethane foam pads, non-woven fabrics, fluororesins, suede pads (buffs), etc., which are used in general CMP polishing. Cleaning using a suede pad is also called buff cleaning.
In addition to the brush cleaning and pad cleaning described above, for example, immersion cleaning, ultrasonic cleaning, rocking cleaning, spray cleaning, and cleaning using rotation of a spinner or the like can be used.
The cleaning methods described above may be implemented singly or in combination.

[Step (2): Alkali cleaning step]
In the step (2) of the cleaning method of the present disclosure, the substrate obtained in the step (1) is treated with a cleaning composition having a pH of 10 or higher containing an alkaline agent and water (hereinafter also referred to as the “alkaline cleaning composition of the present disclosure”). (Alkaline cleaning step). Step (2), in one or more embodiments, can comprise contacting the substrate obtained in step (1) with the alkaline cleaner composition of the present disclosure. In one or more embodiments, step (2) may further include a step of contacting the substrate obtained in step (1) with the alkaline detergent composition of the present disclosure, followed by rinsing with water and drying. good.

<Detergent composition used in step (2) (alkaline detergent composition)>
From the viewpoint of cleaning performance, the alkaline detergent composition of the present disclosure has a pH at 25° C. of 10 or higher, preferably 10.5 or higher, more preferably 11 or higher, and even more preferably 12 or higher.

The alkali agent contained in the alkaline detergent composition of the present disclosure includes at least one of inorganic alkali and organic alkali. Examples of inorganic alkalis include ammonia, potassium hydroxide, sodium hydroxide, and the like. Examples of organic alkalis include dimethylamine and tetramethylammonium hydroxide (TMAH). These alkaline agents may be used singly or in combination of two or more.

The content of the alkaline agent during cleaning with the alkaline detergent composition of the present disclosure is preferably 0.01% by mass or more, more preferably 0.03% by mass or more, and more preferably 0.05% by mass, from the viewpoint of improving cleaning performance. The above is more preferable, and 1% by mass or less is preferable, 0.5% by mass or less is more preferable, and 0.1% by mass or less is even more preferable. More specifically, the content of the alkali agent is preferably 0.01% by mass or more and 1% by mass or less, more preferably 0.05% by mass or more and 0.5% by mass or less, and 0.05% by mass or more and 0.5% by mass or less. 1% by mass or less is more preferable. When the alkali chemicals are a combination of two or more, the content of the alkali chemicals refers to their total content.

As the water contained in the alkaline detergent composition of the present disclosure, ion-exchanged water, RO water, distilled water, pure water, and ultrapure water can be used. The content of water during washing with the detergent composition of the present disclosure can be the remainder after removing the alkaline agent of the present disclosure and the optional components described later that are blended as necessary.

In addition to the alkaline agent and water described above, the alkaline detergent composition of the present disclosure may contain surfactants, chelating agents, ether carboxylates, fatty acids, antifoaming agents, alcohols, preservatives, antioxidants and the like. may contain ingredients. The content of other components during cleaning with the alkaline detergent composition of the present disclosure is preferably 0% by mass or more and 2% by mass or less, and 0% by mass or more and 1.5% by mass, from the viewpoint of not impairing the effects of the present disclosure. The following are more preferable, and 0% by mass or more and 1% by mass or less are even more preferable.

The alkaline detergent composition of the present disclosure can be produced, for example, by blending an alkaline agent, water and, if necessary, other ingredients by a known method. Also, the alkaline detergent composition of the present disclosure may be prepared as a concentrate with a reduced amount of water to the extent that storage stability is not impaired. The dilution rate of the concentrate of the alkaline detergent composition is, for example, 10 to 100 times. The concentrate of the alkaline detergent composition can be used by diluting with water so that each component has the above-described content (that is, the content at the time of washing) at the time of use. When the alkaline cleaner composition of the present disclosure is a concentrate, the cleaning method of the present disclosure can further comprise a dilution step of diluting the concentrate of the alkaline cleaner composition.

As the cleaning method of the step (2), the same cleaning method as the above-described step (1) can be used.

[Method for manufacturing substrate for semiconductor device]
In one aspect, the present disclosure relates to a method for manufacturing a semiconductor device substrate (hereinafter also referred to as "substrate manufacturing method of the present disclosure"), which includes a cleaning step of cleaning a substrate to be cleaned using the cleaning method of the present disclosure. . As the substrate to be cleaned, the substrates described above can be used. The cleaning method and cleaning conditions in the cleaning step of the substrate manufacturing method of the present disclosure can be the same as those of the cleaning method of the present disclosure described above. In one or more embodiments, the substrate manufacturing method of the present disclosure includes a step of performing CMP using a polishing composition containing ceria, and a step of cleaning the substrate to be cleaned using the cleaning method of the present disclosure. can be done.

Here, a specific example of the process of performing CMP is shown below.
First, a silicon substrate is exposed to oxygen in an oxidation furnace to form a silicon substrate including a silicon dioxide layer. Next, a silicon nitride (Si ₃ N ₄ ) film is formed on the silicon dioxide layer side of the silicon substrate, eg, on the silicon dioxide layer, eg, by CVD (chemical vapor deposition). Next, a substrate including the silicon substrate thus obtained and a silicon nitride film arranged on one main surface side of the silicon substrate, for example, a silicon substrate and a silicon substrate arranged on one main surface of the silicon substrate. A substrate containing a silicon nitride film, or a substrate consisting of a silicon substrate and a silicon nitride film disposed on one main surface of the silicon substrate is formed with a photolithography technique by forming a groove penetrating the silicon nitride film and having a silicon bottom. A trench is formed that extends into the substrate. Next, a silicon oxide (SiO ₂ ) film for embedding trenches is formed by, for example, a CVD method using silane gas and oxygen gas, the trenches are filled with silicon oxide, and the trenches and the silicon nitride film are covered with the silicon oxide film. A substrate to be polished is obtained. By forming the silicon oxide film, the trench is filled with the silicon oxide of the silicon oxide film, and the surface of the silicon nitride film opposite to the silicon substrate side is covered with the silicon oxide film. The surface of the silicon oxide film thus formed opposite to the surface facing the silicon substrate has steps formed corresponding to the unevenness of the lower layer. Next, the silicon oxide film is polished with ceria slurry by CMP until at least the surface of the silicon nitride film opposite to the silicon substrate side surface is exposed. The silicon oxide film is polished until the surface becomes flat.

The substrate manufacturing method of the present disclosure uses the cleaning method of the present disclosure for cleaning the substrate to be cleaned, thereby reducing foreign matter such as abrasive grains and polishing dust remaining on the substrate surface after CMP, thereby preventing foreign matter from remaining. Since the occurrence of defects in the post-process caused by this is suppressed, it is possible to manufacture highly reliable substrates for semiconductor devices. Furthermore, by performing the cleaning method of the present disclosure, cleaning of residues such as abrasive grains and polishing dust on the substrate surface after CMP is facilitated, so that the cleaning time can be shortened and the manufacturing efficiency of substrates for semiconductor devices can be improved. can improve.

EXAMPLES The present disclosure will be specifically described below with reference to Examples, but the present disclosure is not limited by these Examples.

1. Preparation of acidic detergent composition and alkaline detergent composition (Examples 1 to 17 and Comparative Examples 1 to 8)
The component A or non-component A shown in Table 1 is blended with water and mixed, and the pH is adjusted as necessary to achieve the pH shown in Table 1, and the acidity of Examples 1 to 17 and Comparative Examples 1 to 8. A cleaning composition was prepared. A 1% nitric acid aqueous solution was used for pH adjustment. The content of component A or non-component A shown in Table 1 is % by mass and is shown as an effective component.
Alkaline detergent compositions of Examples 1 to 17 and Comparative Examples 1 to 8 were prepared by blending and mixing the alkaline agents shown in Table 1 with water. The content of the alkaline agent shown in Table 1 is % by mass, and is shown as an effective component.
The pH in Table 1 is the pH of the cleaning composition at 25° C., measured using a pH meter (HM-30G manufactured by Toa DKK Co., Ltd.), and the electrode was immersed in the cleaning composition for 1 minute. It is the later numerical value.

The following components were used for the preparation of the acidic detergent compositions and alkaline detergent compositions of Examples 1 to 17 and Comparative Examples 1 to 8 shown in Table 1.
(Component A)
Polyacrylic acid [weight average molecular weight 21000, manufactured by Kao]
AA/AMPS copolymer (molar ratio 90/10) [weight average molecular weight 2000, manufactured by Toagosei]
AA/AMPS copolymer (molar ratio 75/25) [weight average molecular weight 2000, manufactured by Toagosei]
AA/AMPS copolymer (molar ratio 55/45) [weight average molecular weight 1500, manufactured by Toagosei]
AA/AMPS copolymer (molar ratio 15/85) [weight average molecular weight 1500, manufactured by Toagosei]
AA/PEGAE copolymer (molar ratio 84/16) [weight average molecular weight 22000, manufactured by Kao]
L(+)-tartaric acid [manufactured by Fujifilm Wako Pure Chemical]
Citric acid [manufactured by Fuji Film Wako Pure Chemical]
(Non-component A)
Hydrochloric acid [manufactured by Kanto Chemical Co., Ltd.]
Acetic Acid [Made by Fuji Film Wako Pure Chemical]
Lactic acid [manufactured by Fuji Film Wako Pure Chemical]
(Alkaline agent)
TMAH [manufactured by Tama Chemical Industry Co., Ltd.]
Dimethylamine [manufactured by Fujifilm Wako Pure Chemical]
NH ₃ : Ammonia [manufactured by Kanto Chemical Co., Ltd.]
KOH: Potassium hydroxide [manufactured by Fuji Film Wako Pure Chemical]
NaOH: sodium hydroxide [manufactured by Fuji Film Wako Pure Chemical]
(water)
Ultrapure water produced using a continuous pure water production system (Pure Conti PC-2000VRL type) and a subsystem (Macace KC-05H type) manufactured by Kurita Water Industries Ltd.

[Measurement of weight average molecular weight]
The weight average molecular weight of the polymer is determined using liquid chromatography (L-6000 high performance liquid chromatography manufactured by Hitachi, Ltd.) and gel permeation chromatography (hereinafter also referred to as "GPC") under the following conditions. It was measured. Table 1 shows the measurement results.
<GPC conditions>
Column: G4000PWXL + G2500PWXL (manufactured by Tosoh Corporation)
Eluent: 0.2 M phosphate buffer/CH ₃ CN=9/1 (volume ratio)
Flow rate: 1.0 mL/min
Column temperature: 40°C
Detection: RI
Sample concentration: 0.5 mg/mL
Standard substance: Polyethylene glycol conversion

2. Evaluation of Detergent Compositions The acidic detergent compositions and alkaline detergent compositions prepared in Examples 1 to 17 and Comparative Examples 1 to 8 were used for the following evaluations.

[Preparation of test piece for cleaning evaluation]
Positively charged ceria (average primary particle size: 45 nm) and 2-hydroxypyridine-N-oxide were mixed with water, and the pH was adjusted to 5 using ammonia water, and each concentration was 0.15% by mass. A polishing composition of 0.015% by mass was prepared. As a pre-polishing test piece, a silicon oxide film test piece of 40 mm×40 mm was cut from a silicon wafer (12 inches) on one side of which a silicon oxide film having a thickness of 2000 nm was formed by the TEOS-plasma CVD method was used. . The polishing apparatus used was Technorise's "R15M-TRK1" with a platen diameter of 380 mm, and the polishing pad was a laminated pad "IC1000/SUBA400" manufactured by Nitta Haas. A polishing pad was affixed to the surface plate of the polishing apparatus, and the test piece was set in a holder so that the silicon oxide film-formed surface of the test piece faced downward, that is, the silicon oxide film was in contact with the polishing pad. The holder was placed on the polishing pad. Furthermore, a weight was placed on the holder so that the load applied to the test piece was 300 g/cm ² , and the polishing liquid composition was dripped at a rate of 50 mL/min onto the center of the surface plate on which the polishing pad was attached. , the surface plate and the holder were rotated in the same direction at 90 revolutions/minute for 30 seconds to polish the silicon oxide film test piece to prepare a cleaning evaluation test piece.

[Evaluation of washability]
First, a test piece for washing evaluation is immersed in an acidic detergent composition, stirred with a magnetic stirrer at a rotation speed of 500 rpm for 30 seconds, and rinsed with water. Then, it is immersed in an alkaline detergent composition, stirred with a magnetic stirrer at a rotation speed of 500 rpm for 30 seconds, and rinsed with water.
After that, the test piece is immersed in a mixed solution containing 20% by mass of sulfuric acid and 12% by mass of hydrogen peroxide (immersion temperature: 60° C., immersion time: 12 hours). Then, the cerium (Ce) ion concentration in the mixed solution is measured using an ICP emission spectrometer ("Afilent 5110" manufactured by Agilent Technologies). The ceria (CeO ₂ ) dissolution amount (ppb) is calculated from the measured cerium ion concentration. Table 1 shows the calculation results. Detergency can be evaluated from the amount of dissolved ceria. The smaller the amount of ceria dissolved, the better the washability.

[Evaluation of storage stability]
100 mL of a 200-fold concentrated solution of the acidic detergent composition was sealed in a 100 mL glass bottle and stored at a low temperature (1° C.) for 1 week. The transmittance of the acidic detergent composition before and after storage was measured. A UV-vis transmittance measuring device (“UV-2550” manufactured by Shimadzu Corporation) was used to measure the transmittance. And it evaluated based on the following evaluation criteria. In A, the acidic cleaning composition did not become cloudy and storage stability was judged to be good, and in B, the acidic cleaning composition became cloudy and storage stability was judged to be poor. Table 1 shows the results.
<Evaluation Criteria>
A: difference in transmittance before and after storage is 10% or less B: difference in transmittance before and after storage is more than 10%

As shown in Table 1, the cleaning methods of Examples 1-17 were superior to the cleaning methods of Comparative Examples 1-8 in cleaning performance against ceria. Moreover, the acidic detergent compositions used in Examples 5 to 11 had good storage stability.

The cleaning method of the present disclosure makes it possible to shorten the cleaning process for substrates to which ceria has adhered and to improve the performance and reliability of manufactured semiconductor device substrates, thereby improving the productivity of semiconductor devices.

Claims (5)

A substrate cleaning method including the following steps (1) and (2).
(1) A step of cleaning a substrate to be cleaned with a cleaning composition having a pH of 5 or less and containing water and a compound having two or more carboxyl groups in the molecule (component A).
(2) A step of cleaning the substrate obtained in step (1) with a cleaning composition having a pH of 10 or higher containing an alkaline agent and water.
However, the substrate to be cleaned is a semiconductor device substrate having a part of silicon oxide surface which is polished with a polishing composition containing cerium oxide particles.
Component A comprises a structural unit a1 derived from an unsaturated carboxylic acid, and a structural unit a2 derived from a monomer having at least one selected from a phosphoric acid group, a phosphonic acid group, a sulfonic acid group and an oxyalkyl group in the molecule. is a copolymer containing
The molar ratio (a1/a2) of the structural unit a1 and the structural unit a2 in all the structural units of the component A is 60/40 or more and 98/2 or less,
The alkaline agent is an organic alkali. The cleaning method according to claim 1 , wherein the weight average molecular weight of component A is 1,000 or more. The cleaning method according to claim 1 or 2, wherein the organic alkali is at least one of dimethylamine and tetramethylammonium hydroxide. The cleaning method according to any one of claims 1 to 3, wherein the content of the alkaline agent is 0.01% by mass or more and 1% by mass or less. 5. A method of manufacturing a semiconductor device substrate, comprising the step of cleaning a substrate to be cleaned using the cleaning method according to any one of claims 1 to 4 .