TW202115234A - Hydrofluoroether-containing solvent and method for treating substrate using hydrofluoroether-containing solvent - Google Patents

Abstract

This solvent comprises a hydrofluoroether represented by formula (1). Rf1 and Rf2 are each independently a fluorine atom, C1-4 straight-chain perfluoroalkyl group, or C3-4 branched perfluoroalkyl group. R3 is a C1-4 straight-chain alkyl group, C3-4 branched alkyl group, C1-4 straight-chain fluoroalkyl group, or C3-4 branched fluoroalkyl group. At least one of Rf1 and Rf2 is the C1-4 straight-chain perfluoroalkyl group or C3-4 branched perfluoroalkyl group.

Description

Solvent containing hydrofluoroether and substrate processing method using solvent containing hydrofluoroether

One embodiment of the present invention relates to a solvent containing hydrofluoroether and a substrate processing method using the solvent containing hydrofluoroether.

The electronic equipment exemplified by the display device and the semiconductor elements contained therein are manufactured by stacking various patterned insulating films, conductive films, and semiconductor films on a glass substrate or a semiconductor substrate. The patterning of these semiconductor films, conductive films, and insulating films is performed by a photolithography process. The photolithography process usually includes: forming a film layer for patterning on a substrate, forming a photoresist film, forming a photoresist mask through the exposure and development of the photoresist film, and etching the film layer through the intermediate photoresist mask, and removing Photoresist film. In these series of steps, the substrate is subjected to various treatments such as removing impurities attached to the substrate, cleaning the film formed on the substrate, and removing etching residues. In such substrate processing, it is known that fluorine-containing ether (hereinafter referred to as hydrofluoroether), hydrofluorocarbon, fluorine-containing alcohol, etc. can be used as a cleaning agent (see Patent Documents 1 and 2).

『Patent Literature』 "Patent Document 1": Japanese Patent Publication No. 2011-187570 "Patent Document 2": Japanese Patent Publication No. 2017-92285

One aspect of the present invention is to provide a solvent containing hydrofluoroether that can be used in the processing of a substrate as one of the problems. Alternatively, one embodiment of the present invention is to provide a method for processing a substrate using this solvent as one of the subjects.

One embodiment of the present invention is a solvent. This solvent contains hydrofluoroether represented by the following formula (1).

"Hua 1"

Rf ¹ and Rf ² are each independently a fluorine atom, a linear perfluoroalkyl group having 1 to 4 carbon atoms, or a branched perfluoroalkyl group having 3 or 4 carbon atoms. R ³ is a straight-chain alkyl group with a carbon number of 1 to 4, a branched alkyl group with a carbon number of 3 or 4, a straight-chain fluoroalkyl group with a carbon number of 1 to 4, or a branched fluoroalkyl group with 3 or 4 carbons . At least one of Rf ¹ and Rf ² is a linear perfluoroalkyl group having a carbon number of 1 or more and 4 or less or a branched perfluoroalkyl group having a carbon number of 3 or 4.

One embodiment of the present invention is a substrate processing method. This substrate processing method includes: washing the substrate with an aqueous cleaning solution; replacing the aqueous cleaning solution attached to the substrate with a first solvent containing an alcohol with a carbon number of 1 or more and 5 or less; The second solvent of hydrofluoroether replaces the first solvent attached to the substrate; the hydrofluoroether in the second solvent attached to the substrate is converted into a supercritical state; and the hydrofluoroether in the supercritical state is removed.

"Hua 2"

Rf ¹ and Rf ² are each independently a fluorine atom, a linear perfluoroalkyl group having 1 to 4 carbon atoms, or a branched perfluoroalkyl group having 3 or 4 carbon atoms. R ³ is a straight-chain alkyl group with a carbon number of 1 to 4, a branched alkyl group with a carbon number of 3 or 4, a straight-chain fluoroalkyl group with a carbon number of 1 to 4, or a branched fluoroalkyl group with 3 or 4 carbons . At least one of Rf ¹ and Rf ² is a linear perfluoroalkyl group having a carbon number of 1 or more and 4 or less or a branched perfluoroalkyl group having a carbon number of 3 or 4.

One embodiment of the present invention is a substrate processing method. This substrate processing method includes: washing the substrate with an aqueous cleaning solution, replacing the aqueous cleaning solution adhering to the substrate with a first solvent containing an alcohol with a carbon number of 1 or more and 5 or less, and containing the following formula (1) The second solvent of hydrofluoroether replaces the first solvent attached to the substrate, replaces the second solvent attached to the substrate with a fluorine solvent, converts the fluorine solvent attached to the substrate into a supercritical state, and removes the fluorine solvent attached to the supercritical state .

"Hua 3"

Rf ¹ and Rf ² are each independently a fluorine atom, a linear perfluoroalkyl group having 1 to 4 carbon atoms, or a branched perfluoroalkyl group having 3 or 4 carbon atoms. R ³ is a straight-chain alkyl group with a carbon number of 1 to 4, a branched alkyl group with a carbon number of 3 or 4, a straight-chain fluoroalkyl group with a carbon number of 1 to 4, or a branched fluoroalkyl group with 3 or 4 carbons . At least one of Rf ¹ and Rf ² is a linear perfluoroalkyl group having a carbon number of 1 or more and 4 or less or a branched perfluoroalkyl group having a carbon number of 3 or 4.

With the implementation of the present invention, the substrate processing such as cleaning the substrate or the film formed on the substrate, removing the etching residue, etc. can be carried out with high efficiency. In addition, since the generation of fluoride ions can be suppressed during substrate processing, it is possible to prevent contamination or deterioration of the substrate or the film formed on the substrate, and the generation of defects caused by fluoride ions.

Hereinafter, various embodiments of the present invention will be described. However, the present invention can be implemented in various forms without departing from the scope of the gist thereof, and is not limited to the interpretation by the following examples of implementation forms and the contents of the examples. In addition, even if it is another action effect that is different from the action effect promoted by the following embodiment type or the embodiment, it is obvious to those who have general knowledge in the technical field of the invention from the description of this specification. Those who can be easily predicted should be understood as those facilitated by the present invention.

1. Hydrofluoroether

1-1. Structure

For cleaning the substrate or the film layer formed on the substrate, in the substrate processing method related to this embodiment, a solvent containing hydrofluoroether is used. The hydrofluoroether related to this embodiment is represented by the following formula (1).

"Hua 4"

In formula (1), Rf ¹ and Rf ² are each independently a fluorine atom, a linear perfluoroalkyl group having 1 to 4 carbon atoms, or a branched perfluoroalkyl group having 3 or 4 carbon atoms. Rf ¹ and Rf ² may be the same or different. R ³ is a straight-chain alkyl group with a carbon number of 1 to 4, a branched alkyl group with a carbon number of 3 or 4, a straight-chain fluoroalkyl group with a carbon number of 1 to 4, or a branched fluoroalkyl group with 3 or 4 carbons . Here, ^{at least one of Rf 1} and Rf ² is a linear perfluoroalkyl group having a carbon number of 1 or more and 4 or less or a branched perfluoroalkyl group having a carbon number of 3 or 4.

Examples of straight-chain perfluoroalkyl groups with a carbon number of 1 to 4 and branched perfluoroalkyl groups with a carbon number of 3 or 4 include: trifluoromethyl, pentafluoroethyl, heptafluoropropyl, and heptafluoroisopropyl Base, nonafluoro n-butyl, nonafluoro isobutyl, nonafluoro secondary butyl, nonafluoro tertiary butyl.

Examples of linear alkyl groups having 1 to 4 carbon atoms and branched alkyl groups having 3 or 4 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, di Grade butyl, tertiary butyl.

Examples of linear fluoroalkyl groups having 1 to 4 carbon atoms and branched fluoroalkyl groups having 3 or 4 carbon atoms include monofluoromethyl, difluoromethyl, trifluoromethyl, 1-fluoroethyl, 2-fluoroethyl, 1,2-difluoroethyl, 1,2,2-trifluoroethyl, 2,2,2-trifluoroethyl, 1,2,2,2-tetrafluoroethyl, 1,1,2,2,2-pentafluoroethyl, 2,2,3,3,3-pentafluoropropyl, 1,1,1,3,3,3-hexafluoroisopropyl, etc.

As a combination of Rf ¹ , Rf ² and R ³ , the following combinations can be exemplified. (A) Rf ¹ is a fluorine atom, Rf ² is a trifluoromethyl group, and R ³ is a methyl group; (b) Rf ¹ is a trifluoromethyl group, Rf ² is a trifluoromethyl group, and R ³ is a methyl group; (c) ) Rf ¹ is trifluoromethyl, Rf ² is pentafluoroethyl, R ³ is methyl; (d) Rf ¹ is trifluoromethyl, Rf ² is trifluoromethyl, R ³ is ethyl; and ( e) Rf ¹ is trifluoromethyl, Rf ² is pentafluoroethyl, R ³ is ethyl

Specific examples of hydrofluoroether include: 1,2,2,2-tetrafluoro-1-methoxyethane, 1,2,2,2-tetrafluoro-1-ethoxyethane, 1 ,1,1,3,3,3-hexafluoro-2-methoxypropane, 1,1,1,3,3,3-hexafluoro-2-ethoxypropane, 1,1,1,3 ,3,3-hexafluoro-2-(1-fluoro)ethoxypropane, 1,1,1,3,3,3-hexafluoro-2-(2-fluoro)ethoxypropane, 1,1 ,1,3,3,3-hexafluoro-2-(1,2-difluoro)ethoxypropane, 1,1,1,3,3,3-hexafluoro-2-(1,2,2 -Trifluoro)ethoxypropane, 1,1,1,3,3,3-hexafluoro-2-(2,2,2-trifluoro)ethoxypropane, 1,1,1,3,3 ,3-hexafluoro-2-(1,2,2,2-tetrafluoro)ethoxypropane, 1,1,1,3,3,3-hexafluoro-2-n-propoxypropane, 1, 1,1,3,3,3-hexafluoro-2-isopropoxypropane, 1,1,1,3,3,3-hexafluoro-2-n-butoxypropane, 1,1,1, 3,3,3-hexafluoro-2-tertiary butoxypropane, 1,1,1,3,3,3-hexafluoro-2-fluoromethoxypropane, 1,1,1,3,3 ,4,4,4-octafluoro-2-methoxybutane, 1,1,1,3,3,4,4,4-octafluoro-2-ethoxybutane, 1,1,1 ,3,3,4,4,5,5,5-decafluoro-2-methoxypentane, 1,1,1,3,3,4,4,5,5,5-decafluoro-2 -Ethoxypentane, 1,1,1,3,3,4,4,5,5,6,6,6-dodecafluoro-2-methoxyhexane, 1,1,1,3 ,3,4,4,5,5,6,6,6-dodecafluoro-2-ethoxyhexane, etc. In one embodiment, although 1,1,1,3,3,3-hexafluoro-2-methoxypropane, 1,1,1,3,3,4,4,4-octafluoro- 2-Methoxybutane is one of the good examples of hydrofluoroether, but it is not limited to this.

1-2. Manufacturing method

The production method of the hydrofluoroether related to this embodiment is not limited, but by using the substitution reaction following the following reaction process, high-purity hydrofluoroether can be obtained with high yield under mild conditions. Specifically, it can be produced by reacting an easily available substituted alcohol (compound 2 in the reaction scheme) with a substituted alkane having a leaving group L or substituted fluoroalkane (compound 3 in the reaction scheme) in the presence of a base. Hydrofluoroether. The definitions of Rf ¹ , Rf ² and R ³ are the same as those in the above-mentioned hydrofluoroether.

"Hua 5"

Examples of the leaving group L include: trifluoromethanesulfonyl, methanesulfonyl, fluorosulfonyl, nonafluorobutanesulfonyl, chlorine, iodine, bromine, p-toluenesulfonyl and other conjugates with high pKa Acid residues. Among them, substituted alkanes or substituted fluoroalkanes having chlorine as the leaving group L are preferred because they can be obtained at relatively low prices.

The type of base is not limited, but examples include: sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, cesium carbonate, cesium bicarbonate, etc., carbonates or bicarbonates of alkali metals or group 2 elements exemplified ; Nitrogen-containing aromatic heterocyclic compounds such as pyridine or pyrrolidine; aromatic amines such as dialkylanilines; aliphatic tertiary amines such as trialkylamines or dialkyl piperidines and alkylpyrrolidines; etc.

The solvent used in the substitution reaction is also not limited. Examples include amine-based solvents such as N,N-dimethylformamide or N,N-dimethylacetamide, and sulfur-containing solvents such as dimethyl sulfoxide. , Ketones such as methyl ethyl ketone, ether solvents such as tetrahydrofuran or dioxane, etc. Among them, an amide-based solvent that is stable under weak alkaline conditions, has high polarity, and has a large difference in boiling point from hydrofluoroether is preferred.

An example of the procedure of the manufacturing method of hydrofluoroether is as follows. The substituted alcohol is added to the mixture of the solvent and the base, and the substituted alkane or substituted fluoroalkane having the leaving group L is dropped into the mixture in the same amount or a slight excess of the substituted alcohol. The reaction temperature can be selected from the range of 0°C or more and 50°C or less, 0°C or more and 40°C or less, or 10°C or more and 30°C or less. The dripping speed can be adjusted appropriately in a way that does not run out of control. Although the reaction time also depends on the reactivity of the substituted alcohol or alkane or fluoroalkane or the type of base, it can be selected from the range of, for example, 1 hour to 3 days, 4 hours to 1 day, and 10 hours to 20 hours. The progress of the reaction can be confirmed by monitoring the concentration of substituted alcohols using, for example, gas chromatography or ¹ H-nuclear magnetic resonance spectroscopy ( ¹ H-NMR) or ¹⁹ F-nuclear magnetic resonance spectroscopy ( ^{19 F-NMR).} .

After the completion of the reaction, the added alkali or the salt precipitated by the reaction is removed by filtration, and the residue is distilled under reduced pressure to obtain the desired hydrofluoroether. The pressure during distillation may be set to, for example, 10 kPa or more and 50 kPa or less. Further precision distillation can be carried out according to requirements.

1-3. Features

The hydrofluoroether related to this embodiment has a solubility of 0.03 g/100g or more and 0.2 g/100g or less, 0.05 g/100g or more and 0.2 g/100g or less, 0.06 g/100g or more and 0.2 The range of g/100g or less or 0.08 g/100g or more and 0.2 g/100g or less is preferable. The substrate processing method will be described later, but the hydrofluoroether whose water solubility is in the above range does not phase separate from a small amount of water, so it becomes possible to replace and adhere to the substrate with a solvent containing hydrofluoroether with high efficiency. The alcohol-containing solvent and the water-based cleaning solution it contains.

The fluorine content of the hydrofluoroether is preferably 40% by weight or more and 70% by weight or less, 45% by weight or more and 66% by weight or less, or 50% by weight or more and 65% by weight or less. When the fluorine content meets this range, the surface tension can be maintained low, and the so-called pattern collapse can be prevented during the photolithography process. In addition, since the fluorine content in this range can ensure a relatively high solubility in water, it is possible to maintain high miscibility with the water-based cleaning solution. Furthermore, when the fluorine content is in the above range, the flammability of the hydrofluoroether is low. Here, the so-called fluorine content is calculated in the form of "(number of fluorine atoms x 19)/hydrofluoroether molecular weight" x 100 (%), for example, where Rf ¹ is trifluoromethyl, Rf ² When it is a trifluoromethyl group and R ³ is a methyl group (the molecular formula at this time is C ₄ H ₄ F ₆ O), the fluorine content is "(6×19)/182"×100=63% by weight.

The purity of the hydrofluoroether is preferably 99.0% or more and 100% or less, 99.5% or more and 100% or less, or 99.9% or more and 100% or less. The purity is calculated from the area ratio in the gas chromatogram, for example. By maintaining such high purity, the probability of defects in semiconductor components or electronic equipment can be greatly reduced. In order to ensure the purity in this range, the hydrofluoroether is highly purified by removing water, fluoride ions, metal elements, etc. by distillation purification or purification by contact treatment with ion exchange resin, activated carbon or hydrotalcite, etc. Turn into the best. Here, the so-called hydrotalcite is a kind of clay mineral represented ^{by the general formula [M 2+} _1−x M ³⁺ _x (OH) ₂ ] ^x+ [A ⁿ⁻ _x/n ·mH ₂ O] ^x−. M ²⁺ is a divalent metal ion such ^{as Mg 2+} or Zn ^{2+ , M 3+} is a ^{trivalent metal ion such as Al 3+} or Fe ³⁺ , and A ⁿ⁻ is CO ₃ ²⁻ , Cl ⁻ , NO ₃ ⁻ An anion with n-valence, X is greater than 0 and 0.33 or less.

The concentration of the fluoride ion in the hydrofluoroether is preferably 0 weight ppb or more and 40 weight ppb or less. The concentration of the metal element in the hydrofluoroether is preferably 0 weight ppb or more and 500 weight ppb or less. Here, as the above-mentioned metal element, iron or nickel, chromium, aluminum, zinc, copper, magnesium, lithium, potassium, sodium, calcium, etc. can be exemplified.

Considering the impact on the environment, hydrofluoroethers preferably have a global warming potential (GWP) of 0 or more and 500 or less. Examples of hydrofluoroethers having a GWP of 0 or more and 500 or less include 1,1,1,3,3,3-hexafluoro-2-methoxypropane (GWP 25), 1,1,1,3, 3,3-hexafluoro-2-ethoxypropane, 1,1,1,3,3,3-hexafluoro-2-n-propoxypropane, 1,1,1,3,3,3-hexa Fluoro-2-isopropoxypropane, 1,1,1,3,3,3-hexafluoro-2-n-butoxypropane, 1,1,1,3,3,3-hexafluoro-2- Tertiary butoxypropane, 1,1,1,3,3,4,4,4-octafluoro-2-methoxybutane, 1,1,1,3,3,4,4,4- Octafluoro-2-ethoxybutane and so on.

2. Substrate processing method

The following describes the substrate processing method related to this embodiment.

As the substrate to which the substrate processing method related to this embodiment can be applied, not only a substrate containing a semiconductor or compound semiconductor such as silicon or germanium, but also a substrate containing an insulator such as sapphire, quartz, or glass can be cited. The substrate may be unprocessed, or may be in a state where an insulating film, a semiconductor film, or a conductive film has already been formed. For example, it may be a substrate in which an insulating film, a semiconductor film, or a conductive film formed on the substrate has been etched.

The substrate processing method using the hydrofluoroether related to this embodiment is roughly divided into the following first substrate processing method and second substrate processing method.

2-1. The first substrate processing method

The flow of the first substrate processing method is disclosed in FIG. 1. As shown in Fig. 1, the first substrate processing method includes: (S1) permeating a water-based cleaning solution to clean the substrate, (S2) replacing the water-based cleaning solution attached to the substrate with an alcohol-containing solvent, and (S3) permeating a water-based cleaning solution containing hydrofluoroether. The solvent replaces the alcohol-containing solvent attached to the substrate, (S4) converts the hydrofluoroether attached to the substrate into a supercritical state, and (S5) removes the supercritical hydrofluoroether. Each process is described below.

(S1) Wash the substrate with water-based cleaning solution

As the water-based cleaning liquid, water can be mentioned. In the case of preventing contamination of the substrate or various film layers formed on the substrate, it is better to use high-purity water (such as ultrapure water) as an aqueous cleaning solution. For example, it is preferable that the content of the metal element in the water-based cleaning solution is 0 weight ppb or more and 500 weight ppb or less. Examples of methods for reducing the content of metal elements include distillation or filtration, treatment with ion exchange resins or activated carbon, and the like.

In order to efficiently remove substances attached to the substrate, additives can also be added to the water-based cleaning solution to improve the solubility of the substances to be removed. Examples of additives include organic solvents, hydrogen peroxide, ozone, acids, alkalis, surfactants, and the like. In this case, in order to prevent damage to the substrate, the aqueous cleaning solution preferably contains 80% by weight or more and 100% by weight of water.

In the cleaning by permeating the water-based cleaning liquid, the water-based cleaning liquid in a liquid state can be supplied to the substrate, or the water-based cleaning liquid can be vaporized into vapor and supplied to the substrate. In the former case, the substrate is cleaned by injecting an aqueous cleaning solution onto the substrate through an intermediate nozzle, immersing the substrate in the aqueous cleaning solution, or dropping the aqueous cleaning solution on the substrate and then rotating the substrate. In the latter case, the substrate may be cleaned by exposing the substrate to the vapor of the water-based cleaning liquid. An inert gas such as nitrogen or argon can also be added to the vapor of the water-based cleaning liquid as a diluent gas. The substrate can be cleaned one by one (single-chip), or multiple substrates can be cleaned at a time (batch-type).

Through the above cleaning process, the target that should be removed from the substrate will be removed, and the water-based cleaning solution will adhere to the substrate.

(S2) Replace the water-based cleaning solution adhering to the substrate with an alcohol-containing solvent

In this step, the water-based cleaning solution adhering to the substrate is replaced with a solvent (first solvent) containing an alcohol having a carbon number of 1 or more and 5 or less. Here, a solvent containing an alcohol having a carbon number of 1 or more and 5 or less is referred to as an alcohol-containing solvent.

In order to replace the water-based cleaning liquid with high efficiency, it is preferable that the alcohol-containing solvent is compatible with water in any ratio. Therefore, as the alcohol-containing solvent, an alcohol having a carbon number of 1 or more and 5 or less or a mixed liquid of an alcohol having a carbon number of 1 or more and 5 or less and other organic solvents is used.

Examples of alcohols with a carbon number of 1 to 5 include: methanol, ethanol, n-propanol, 2-propanol, 1-butanol, isobutanol, secondary butanol, tertiary butanol, and propylene glycol monomethyl Base ether. It is preferable that these can be obtained at a low price and with high purity. Among these alcohols, 2-propanol, which has a moderate boiling point and viscosity, and exhibits high miscibility with water, is preferred. One kind or two or more kinds of these alcohols can be used.

The content of the metal elements mentioned above in the alcohol-containing solvent is preferably low. Specifically, the content of each metal element is preferably 0 weight ppb or more and 500 weight ppb or less. By satisfying the above range, the substrate or various film layers formed on the substrate can be prevented from being contaminated, and as a result, the probability of occurrence of defects in semiconductor devices or electronic devices can be greatly reduced. In order to reduce the content of metal elements, the alcohol-containing solvent can also be purified by distillation or filtration, treatment with ion exchange resin or activated carbon, etc.

In the case of using other organic solvents, the other organic solvents may be selected from ketones such as acetone or methyl ethyl ketone. One type or two or more types of other organic solvents can be used.

The "replacement of the water-based cleaning solution with an alcohol-containing solvent" can be performed by the same method as the above-mentioned "washing of the substrate with the water-based cleaning solution", so the detailed description will be omitted. The water contained in the aqueous cleaning solution has a high boiling point and lacks volatility. In addition, since water exhibits high solubility for various electrolytes, once the water remains on the substrate, the electrolyte existing around the substrate will dissolve, and as a result, the substrate will be contaminated. However, by replacing the water with an alcohol-containing solvent with high water miscibility, the water on the substrate can be quickly removed, and the adhesion of impurities caused by the residual water can be suppressed.

Through the above cleaning process, the aqueous cleaning solution will be almost removed from the substrate, and the alcohol-containing solvent will adhere to the substrate.

(S3) Replace the alcohol-containing solvent attached to the substrate by the solvent containing hydrofluoroether

In this step, the alcohol-containing solvent adhering to the substrate and the water derived from the aqueous cleaning solution are replaced with a solvent (second solvent) containing hydrofluoroether represented by formula (1). Hereinafter, this second solvent is referred to as a hydrofluoroether solvent.

The content of the hydrofluoroether in the hydrofluoroether solvent is preferably 90% by weight or more and 100% by weight or less, 95% by weight or more and 100% by weight or less, or 97% by weight or more and 100% by weight or less. The hydrofluoroether may contain one type or two or more types. As described later, in the substrate processing method related to this embodiment, the hydrofluoroether is transformed into a supercritical state. By adjusting the content of the hydrofluoroether in the hydrofluoroether solvent to the above-mentioned range, the stability of the supercritical state of the hydrofluoroether can be improved.

The hydrofluoroether solvent may also contain other ingredients. The other components may be one type or two or more types. As other components, any one that can dissolve in hydrofluoroether is sufficient, and an organic solvent is preferred. As an organic solvent, the ketones etc. mentioned above are mentioned, for example. Fluorine-containing alcohols such as hexafluoroisopropanol can also be used as the organic solvent. Since the fluorine-containing alcohol is non-flammable, it can maintain the low non-flammability of the hydrofluoroether solvent. The concentration of other components in the hydrofluoroether solvent is preferably higher than 0% by weight and 10% by weight or less.

Like the alcohol-containing solvent, the content of the aforementioned metal elements in the hydrofluoroether solvent is preferably low. Specifically, the content of each metal element is preferably 0 weight ppb or more and 500 weight ppb or less. By satisfying the above range, the substrate or various film layers formed on the substrate can be prevented from being contaminated, and as a result, the probability of occurrence of defects in semiconductor devices or electronic devices can be greatly reduced. In order to reduce the content of metal elements, it is also possible to purify the hydrofluoroether solvent by distillation, filtration, extraction, treatment with ion exchange resin or activated carbon, etc.

The "replacement of the alcohol-containing solvent with the hydrofluoroether solvent" can be performed by the same method as the above-mentioned "washing of the substrate with an aqueous cleaning solution", so the detailed description will be omitted. Compared with water, the alcohol contained in the alcohol-containing solvent has a lower boiling point and higher volatility, but the evaporation rate at the external environmental temperature (for example, room temperature) may not be high. Therefore, if the alcohol remains on the substrate for a long time, impurities existing around the substrate will be absorbed and dissolved in the alcohol, and as a result, the substrate will be contaminated. However, since the hydrofluoroether and alcohol related to this embodiment have high mutual solubility, by treating the substrate with a hydrofluoroether solvent, the alcohol can be removed with high efficiency. Furthermore, the alcohol-containing solvent adhering to the substrate may contain water derived from an aqueous cleaning solution. However, since the hydrofluoroether related to this embodiment has high water miscibility, this process can also be highly efficient Remove the water from the water-based cleaning solution.

Through the above cleaning process, the alcohol-containing solvent will be removed from the substrate, and the hydrofluoroether solvent will adhere to the substrate.

(S4) Transform the hydrofluoroether attached to the substrate into a supercritical state

In this process, the hydrofluoroether contained in the hydrofluoroether solvent attached to the substrate is transformed into a supercritical state. That is, the substrate is transported into the chamber and the temperature and pressure in the chamber are set above the critical point of hydrofluoroether, thereby converting the hydrofluoroether into a supercritical fluid.

The structure of the chamber is not limited, and it has a pressurizing mechanism for pressurizing the inside by introducing an inert gas such as a hydrofluoroether solvent, hydrofluoroether, and/or nitrogen or argon into the inside while the substrate is accommodated. And/or a heating mechanism for heating the substrate. The pressurizing mechanism is constructed in such a way that the partial pressure of the hydrofluoroether in the chamber can be set to a pressure higher than the critical pressure of the hydrofluoroether. For example, the pressurizing mechanism can be configured to pressurize the chamber to a pressure selected from the range of 0.5 MPa or more and 10 MPa or less, 1 MPa or more and 10 MPa or less, or 1 MPa or more and 5 MPa or less. The heating mechanism may be a heater that can heat the entire interior of the chamber, or a stage supporting the substrate may be installed inside the chamber and a heating element such as a sheathed heater mounted in the stage may be used as the heating mechanism. The heating mechanism is configured to heat the chamber or the substrate at a temperature above the critical temperature of the hydrofluoroether. Specifically, the heating mechanism is configured to heat the chamber or the substrate at a temperature selected from the range of 30°C or more and 500°C or less, 100°C or more and 300°C or less, or 120°C or more and 200°C or less.

The chamber may also be equipped with a gas inlet for introducing the hydrofluoroether solvent, hydrofluoroether and/or inert gas into the chamber, a gas supply source connected to it, and an exhaust for exhausting the gas inside the chamber The valve and the exhaust device or gas processing device connected to it can be configured as arbitrary structures. Furthermore, a transport mechanism such as a transport robot or a conveyor for carrying in and out of the substrate may be mounted or connected to the chamber.

"Converting the hydrofluoroether into a supercritical state" is to use a heating mechanism to heat the chamber or the substrate after the substrate treated with the hydrofluoroether solvent is transported into the chamber. Alternatively, hydrofluoroether, hydrofluoroether solvent and/or inert gas can also be introduced into the chamber to pressurize the inside of the chamber. Alternatively, a heating mechanism can also be used to heat the chamber or the substrate, while at the same time introducing hydrofluoroether, hydrofluoroether solvent and/or inert gas into the chamber. The partial pressure of the hydrofluoroether in the chamber and the temperature in the substrate or the chamber are adjusted in such a way that the pressure and temperature are above the critical point of the hydrofluoroether.

When the hydrofluoroether reaches a critical point in the chamber, it will act as a supercritical fluid. Therefore, hydrofluoroether has high diffusivity, and the surface of the substrate is covered by supercritical fluid. As a result, the capillary force that acts when the hydrofluoroether in the form of liquid between adjacent patterns evaporates does not exist, and the occurrence of pattern collapse due to capillary force can be prevented.

(S5) Remove the hydrofluoroether in supercritical state

In this process, the hydrofluoroether in the supercritical state is removed from the substrate without turning it into a liquid state. More specifically, the heating mechanism is used to maintain the chamber or the substrate at a temperature higher than the boiling point of the alcohol contained in the hydrofluoroether and the alcohol-containing solvent, and the hydrofluoroether is discharged from the chamber. The exhaust may be performed using an exhaust valve or the like provided in the chamber. Thereby, the hydrofluoroether in the supercritical state can be transformed into a gas state without returning to a liquid state, and removed from the substrate. Therefore, the substrate can be dried and the pattern collapse caused by the liquid hydrofluoroether can be prevented. After that, the substrate is taken out from the chamber.

Hydrofluoroether is known to decompose when heated due to its structure, and generate by-product fluoride ions in the form of decomposition products. For example, 1,1,2,2-tetrafluoro-2-(2,2,2-trifluoro)ethoxyethane (CF ₃ CH ₂ OCF ₂ CHF ₂ , hereinafter written as HFE-347pc-f) It is known that it is decomposed by heating when it is transformed into a supercritical state, and a by-product fluoride ion is generated. The generated fluoride ions cause damage to the silicon oxide contained in the substrate or the silicon oxide-containing film formed on the substrate, and therefore have a bad influence on the patterning in the photolithography process.

However, as shown in the examples, the hydrofluoroether related to an embodiment of the present invention is not easily decomposed even if it is heated in order to transform into a supercritical state, and does not generate fluoride ions or generates a very small amount. Therefore, in substrate processing, even if the hydrofluoroether of this embodiment is used in a supercritical state, it will not affect the substrate or various films formed on the substrate. Therefore, the substrate processing method using the hydrofluoroether and/or the hydrofluoroether solvent containing the hydrofluoroether according to one embodiment of the present invention can be said to be suitable for ultra-fine processing on the substrate.

2-2. The second substrate processing method

The flow of the second substrate processing method is disclosed in FIG. 2. As shown in Fig. 2, the second substrate processing method includes: (S11) permeating a water-based cleaning solution to clean the substrate, (S12) replacing the water-based cleaning solution attached to the substrate with an alcohol-containing solvent, and (S13) permeating a hydrofluoroether solvent Replace the alcohol-containing solvent attached to the substrate, (S14) replace the hydrofluoroether solvent attached to the substrate through the fluorine solvent, (S15) convert the fluorine solvent attached to the substrate into a supercritical state, and (S16) convert the supercritical state The fluorine solvent is removed. Since the steps (S11) to (S13) can be performed in the same way as the steps (S1) to (S3) of the first substrate processing method, the description is reluctantly omitted. The steps (S14) to (S16) will be described below.

(S14) Replace the hydrofluoroether solvent attached to the substrate by the fluorine solvent

In this step, the fluorine solvent is used to replace the hydrofluoroether solvent remaining after cleaning the substrate with the hydrofluoroether solvent. Specifically, a fluorine solvent in a liquid state is supplied to the substrate, or the fluorine solvent is vaporized and supplied to the substrate in the form of vapor. In the former case, the substrate is cleaned by injecting a fluorine solvent from an intermediate nozzle, immersing the substrate in the fluorine solvent, or dropping the fluorine solvent on the substrate and then rotating the substrate. In the latter case, cleaning can be performed by exposing the substrate to the vapor of a fluorine solvent. It is also possible to add inert gas such as nitrogen or argon to the vapor of the fluorine solvent as a diluent gas. The substrate can be cleaned one by one (single-chip), or multiple substrates can be cleaned at a time (batch-type).

The fluorine solvent is not limited, but specific fluorine solvents include: CF ₃ CF ₂ CH ₂ OCHF ₂ , CF ₃ CF ₂ OCH ₂ CF ₃ , CF ₃ CF ₂ CF ₂ OCH ₃ , (CF ₃ ) ₂ CFOCH ₃ , CF ₃ CF ₂ CF ₂ CF ₂ OCH ₃ , (CF ₃ ) ₂ CFCF ₂ OCH ₃ , CF ₃ CF ₂ (CF ₃ )CFOCH ₃ , (CF ₃ ) ₃ COCH ₃ , CF ₃ CF ₂ CF ₂ CF ₂ OCH ₂ CH ₃ , (CF ₃ ) ₂ CFCF ₂ OCH ₂ CH ₃ , CF ₃ CF ₂ (CF ₃ )CFOCH ₂ CH ₃ , (CF ₃ ) ₃ COCH ₂ CH ₃ , (CF ₃ ) ₂ CFCF(OCH ₃ )CF ₂ CF ₃ , CHF ₂ CF ₂ OCH ₂ CF ₃ , C ₄ F ₉ H, C ₅ F ₁₁ H, C ₆ F ₁₃ H, C ₄ F ₉ CH ₂ CH ₃ , C ₆ F ₁₃ CH ₂ CH ₃ , CF ₃ CH ₂ CF ₂ CH ₃ , cC ₅ F ₇ H ₃ , CF ₃ CF ₂ CHFCHFCF ₃ , CF ₃ CH ₂ CHF ₂ , (CF ₃ CF ₂ CF ₂ CF ₂ ) ₃ N and perfluorohexane. One type or two or more types of fluorine solvents can be used.

Like the alcohol-containing solvent or the hydrofluoroether solvent, the content of the aforementioned metal elements in the fluorine solvent is preferably low. Specifically, the content of each metal element is preferably 0 weight ppb or more and 500 weight ppb or less. By satisfying the above range, the substrate or various film layers formed on the substrate can be prevented from being contaminated, and as a result, the probability of occurrence of defects in semiconductor devices or electronic devices can be greatly reduced. In order to reduce the content of metal elements, the fluorine solvent can also be purified by distillation, filtration, extraction, treatment with ion exchange resin or activated carbon, etc.

Through this cleaning process, the hydrofluoroether solvent will be removed from the substrate, and the fluorine solvent will adhere to the substrate.

(S15) Turn the fluorine solvent attached to the substrate into a supercritical state

In this process, the fluorine solvent attached to the substrate is transformed into a supercritical state. That is, the substrate is transported into the chamber, and the temperature in the chamber and the partial pressure of the fluorine solvent are set to be above the critical point of the fluorine solvent, thereby converting the fluorine solvent into a supercritical fluid. The specific method is the same as the process (S4), so the explanation is reluctantly omitted.

(S16) Removal of fluorine solvent in supercritical state

In this process, the fluorine solvent in the supercritical state is removed from the substrate without turning it into a liquid state. Specifically, following the step (S5), the heating mechanism is used to maintain the chamber or the substrate at a temperature higher than the boiling point of the alcohol contained in the fluorine solvent, hydrofluoroether, and alcohol-containing solvent, and the fluorine solvent is removed from the chamber. discharge. Thereby, the fluorine solvent in the supercritical state can be converted into a gas state without returning to the liquid state, and removed from the substrate. Therefore, it can prevent the pattern from collapsing caused by the fluorine solvent in the liquid state. After that, the substrate is taken out from the chamber.

"Example"

1. Example 1

In this example, the result of evaluating the miscibility of hydrofluoroether with water related to one embodiment of the present invention is described. The miscibility with water is evaluated by the solubility of water in hydrofluoroether.

1,1,1,3,3,3-hexafluoro-2-methoxypropane (purity 99.9%, hereinafter referred to as HFE-356) is used as a hydrofluoroether related to one embodiment of the present invention. Put 20 g of HFE-356 and 1 g of ultrapure water into a 50 mL glass sample container, mix well, and then let it stand at 20°C. After the solution is separated into two phases, a Karl-Fisher moisture meter (manufactured by Kyoto Electronics Industry Co., Ltd., MKC-610) is used to measure the moisture concentration of the lower organic layer. Each measurement was carried out 3 times.

Novec (registered trademark) 7200, Novec (registered trademark) 7300, Novec (registered trademark) 7500, and HFE-347pc manufactured by 3M Corporation using hydrofluoroethers that are "hydrofluoroethers that are not an embodiment of the present invention" -f (ASAHIKLIN (registered trademark) AE-3000 manufactured by AGC) As a comparative example, the same measurement was performed. The structural formulas of Novec (registered trademark) 7200, Novec (registered trademark) 7300, and Novec (registered trademark) 7500 are C ₄ F ₉ OC ₂ H ₅ , C ₂ F ₅ CF (OCH ₃ ) C ₃ F ₇ , C ₃ F ₇ CF(OC ₂ H ₅ )CF(CF ₃ ) ₂ , the structural formula of HFE-347pc-f is CF ₃ CH ₂ OCF ₂ CF ₂ H. The weight of water in 100 g of hydrofluoroether calculated from the results of each measurement is summarized in Table 1.

"Table 1" Table 1 Evaluation of the mutual solubility of hydrofluoroether and water Fluoroether Water content (mg/100g) Average (mg/100 g) 1st 2nd the 3rd time HFE-356 81.87 81.94 82.44 82.08 Novec 7200 12.03 11.99 12.38 12.13 Novec 7300 7.44 7.66 7.86 7.65 Novec 7500 5.58 5.34 5.69 5.54 HFE-347pc-f 86.34 85.68 83.79 85.27

It can be seen from Table 1 that compared with Novec (registered trademark) 7200, Novec (registered trademark) 7300, and Novec (registered trademark) 7500, HFE-356 has significantly higher water solubility at 20°C, and the amount of water dissolved is as much as About 7 to 15 times. In addition, it can be seen that the miscibility of HFE-356 with water is the same level as HFE-347pc-f, which has a relatively high miscibility with water.

2. Example 2

In this example, the evaluation result of the miscibility of hydrofluoroether with water related to an embodiment of the present invention is described in comparison with Example 1. However, in this example, the miscibility with water of the hydrofluoroether containing a small amount of alcohol-containing solvent will be evaluated.

Specifically, HFE-356 is used as a hydrofluoroether related to an embodiment of the present invention, and Novec (registered trademark) is a hydrofluoroether that is "hydrofluoroether not belonging to an embodiment of the present invention". 7200, Novec (registered trademark) 7300, Novec (registered trademark) 7500 as comparative examples. Put 29.7 g of each hydrofluoroether, 0.3 g of 2-propanol as an alcohol-containing solvent, and 1 g of ultrapure water into a 50 mL glass sample container at 20°C, and place it in a glass sample container after thorough mixing. ℃. After the solution was separated into two phases, the same method as in Example 1 was applied, and the measurement system was the moisture concentration of the lower organic layer. Each measurement was performed 3 times, and the average value was used as the result. Table 2 shows the weight of water present in 100 g of hydrofluoroether.

"Table 2" Table 2 Evaluation of the miscibility of hydrofluoroether containing alcoholic solvents with water Fluoroether Water content (mg/100g) HFE-356 110.3 Novec 7200 21.7 Novec 7300 13.8 Novec 7500 9.6

It can be seen from Table 2 that even when a small amount of alcohol-containing solvent is included, HFE-356, which is a hydrofluoroether related to this embodiment, has a higher solubility in water at 20°C, compared to the hydrogen in the comparative example. The fluoroether is about 5 times to 11 times. In addition, it was confirmed that the solubility of water in hydrofluoroether increased due to the inclusion of a small amount of alcohol.

These results contribute to the cleaning efficiency in the above-mentioned steps (S3) and (S13). If the substrate that has been cleaned with an alcohol-containing solvent is cleaned with a hydrofluoroether solvent, the hydrofluoroether solvent will adhere to the substrate, but the hydrofluoroether solvent attached to the substrate may include a small amount of alcohol-containing solvent and water-based cleaning. Net liquid. As is obvious from Examples 1 and 2, the hydrofluoroether related to this embodiment type shows high miscibility with water regardless of whether it contains an alcohol-containing solvent. Furthermore, as is obvious from this embodiment, the hydrofluoroether related to this embodiment contains a small amount of alcohol-containing solvent, so the solubility of water is increased. Therefore, in the state where the hydrofluoroether solvent is attached to the substrate, the hydrofluoroether solvent will not phase separate from water, and the hydrofluoroether solvent can be efficiently permeated through the steps (S3) and (S13) To replace alcohol-containing solvents or water-based cleaning solutions.

3. Example 3

In this example, the result of evaluating the thermal stability of hydrofluoroether is described.

Use HFE-356 and 1,1,1,3,3,4,4,4-octafluoro-2-methoxybutane (hereinafter referred to as HFE-458) as the hydrofluorine related to one embodiment of the present invention Ether, using hexafluoroisopropanol (hereinafter referred to as HFIP) as a comparative example. Put 35 mL of each sample into a 50 mL stainless steel reactor and seal it. The sample was cooled to -78°C and degassed, and then heated at 150°C in an oil bath. Before heating and after 21 hours, 42 hours, and 105 hours have passed after heating, take 5 mL of each sample and analyze it by gas chromatography and ion chromatography. A gas chromatograph (manufactured by Shimadzu Corporation, GC-2030) was used for gas chromatography analysis, and an ion chromatograph (manufactured by Thermo Fisher Scientific, ICS-2100) was used for ion chromatography analysis. The purity of the sample is calculated from the area ratio in the gas chromatogram. The results are shown in Table 3.

"table 3" Table 3 Thermal stability evaluation of hydrofluoroether 105 hours later F ion (ppb) 60 70 430 GC purity (area%) ＞99.99 ＞99.99 ＞99.99 42 hours later F ion (ppb) 50 55 200 GC purity (area%) ＞99.99 ＞99.99 ＞99.99 21 hours later F ion (ppb) ≦40 50 80 GC purity (area%) ＞99.99 ＞99.99 ＞99.98 Before heating F ion (ppb) ≦40 ≦40 ≦40 GC purity (area%) ＞99.99 ＞99.99 ＞99.99 Sample HEF-356 HEF-458 HFIP

No matter which sample was heated for 105 hours, there was no change in appearance and maintained a colorless and transparent state. Moreover, no new sharp peaks were observed in the gas chromatogram of any sample. On the other hand, it is known that compared to HFE-356 and HFE-458, which are hydrofluoroethers related to this embodiment, in HFIP, which is a fluorine-containing alcohol, fluoride ions are greatly increased by heating. From this, it was confirmed that the hydrofluoroether related to this embodiment is thermally stable compared to the fluorine-containing alcohol.

4. Example 4

In this example, the results of evaluating the stability of hydrofluoroether in a supercritical state are described.

HFE-356 and HFE-458 are used as the hydrofluoroether related to one embodiment of the present invention, and HFE-347pc-f is used as a comparative example. 14.5 g of each sample was put into approximately 25 mL stainless steel reactor and sealed. The sample was cooled to -78°C and degassed, and then heated at 200°C in an oil bath. At this time, it was confirmed that the pressure in the container was 2.7 MPa or more. Since the critical temperature of HFE-356 is 186°C and the critical pressure is 2.7 MPa, this means that HFE-356 exists in a supercritical state under these conditions. After heating at the same temperature for 6 hours, the sample was analyzed in the same manner as in Example 3. In the case of using HFE-458 and HFE-347pc-f, it is confirmed that the critical temperature and critical pressure are reached. These results are disclosed in Table 4.

"Table 4" Table 4 Thermal stability evaluation of hydrofluoroether in supercritical state Sample Before heating 6 hours later GC purity (area%) F ion (ppb) GC purity (area%) F ion (ppb) HFE-356 ＞99.99 ≦40 ＞99.99 ≦40 HFE-458 ＞99.99 ≦40 ＞99.99 ≦40 HFE-347pc-f ＞99.99 ≦40 ＞99.98 70

No matter which sample was heated for 6 hours, there was no change in appearance and maintained a colorless and transparent state. Moreover, no new sharp peaks were observed in the gas chromatogram of any sample. However, if compared with HFE-356 and HFE-458, which are hydrofluoroethers related to one embodiment of the present invention, it can be confirmed that the fluoride ion concentration in HFE-347pc-f of the comparative example is increased. This fact implies that the hydrofluoroether and the solvent containing it related to this embodiment have high stability in the supercritical state.

S1, S2, S3, S4, S5, S11, S12, S13, S14, S15, S16: Process

<FIG. 1> shows a flowchart of a substrate processing method according to an embodiment of the present invention.

<FIG. 2> shows a flowchart of a substrate processing method according to an embodiment of the present invention.

S1, S2, S3, S4, S5: process

Claims (20)

A substrate processing method comprising: washing a substrate with an aqueous cleaning solution; replacing the aqueous cleaning solution attached to the substrate with a first solvent containing an alcohol having a carbon number of 1 to 5; 1) The second solvent of the hydrofluoroether shown replaces the first solvent attached to the substrate; the hydrofluoroether contained in the second solvent attached to the substrate is transformed into a supercritical state; and the supercritical state is Removal of the aforementioned hydrofluoroether; "Chemical 1"

Rf ¹ and Rf ² are each independently a fluorine atom, a linear perfluoroalkyl group with a carbon number of 1 to 4 or a branched perfluoroalkyl group with a carbon number of 3 or 4, and R ³ is a straight chain with a carbon number of 1 or more and 4 or less. Chain alkyl, branched alkyl with 3 or 4 carbons, linear fluoroalkyl with 1 to 4 carbons, or branched fluoroalkyl with 3 or 4 carbons, at least one of ^{Rf 1} and Rf ^{2 is carbon} A straight-chain perfluoroalkyl group with a number of 1 to 4 or a branched perfluoroalkyl group with a carbon number of 3 or 4. A substrate processing method comprising: washing a substrate with an aqueous cleaning solution; replacing the aqueous cleaning solution attached to the substrate with a first solvent containing an alcohol having a carbon number of 1 to 5; 1) The second solvent of the hydrofluoroether shown replaces the first solvent attached to the substrate; the second solvent attached to the substrate is replaced with a fluorine solvent; the fluorine solvent attached to the substrate is transformed into a supercritical state ; And to remove the aforementioned fluorine solvent in the supercritical state; "Chemical 2"

Rf ¹ and Rf ² are each independently a fluorine atom, a linear perfluoroalkyl group with a carbon number of 1 to 4 or a branched perfluoroalkyl group with a carbon number of 3 or 4, and R ³ is a straight chain with a carbon number of 1 or more and 4 or less. Chain alkyl, branched alkyl with 3 or 4 carbons, linear fluoroalkyl with 1 to 4 carbons, or branched fluoroalkyl with 3 or 4 carbons, at least one of ^{Rf 1} and Rf ^{2 is carbon} A straight-chain perfluoroalkyl group with a number of 1 to 4 or a branched perfluoroalkyl group with a carbon number of 3 or 4. The substrate processing method according to claim 1 or 2, wherein the aforementioned transformation is performed in a chamber. The substrate processing method according to claim 1, wherein the removal is performed without the hydrofluoroether in a liquid state. The substrate processing method according to claim 2, wherein the removal is performed without the hydrofluoroether in a liquid state. The substrate processing method according to claim 1 or 2, wherein the solubility of the hydrofluoroether in water at 20° C. is 0.03 g/100g or more and 0.2 g/100g or less. The substrate processing method according to claim 1 or 2, wherein the fluorine content of the hydrofluoroether is 40% by weight or more and 70% by weight or less. The substrate processing method according to claim 1 or 2, wherein the global warming potential of the hydrofluoroether is 0 or more and 500 or less. The substrate processing method according to claim 1 or 2, wherein Rf ¹ and Rf ² are each independently a linear perfluoroalkyl group with a carbon number of 1 or more and a carbon number of 4 or less, or a branched perfluoroalkyl group with a carbon number of 3 or 4, and R ³ is a straight-chain alkyl group having 1 to 4 carbon atoms or a branched alkyl group having 3 or 4 carbon atoms. The substrate processing method according to claim 1 or 2, wherein Rf ¹ and Rf ² are each independently a trifluoromethyl group or a pentafluoroethyl group, and R ³ is a methyl group or an ethyl group. The substrate processing method according to claim 1 or 2, wherein the aforementioned hydrofluoroether is selected from 1,1,1,3,3,3-hexafluoro-2-methoxypropane, 1,1,1,3 ,3,3-hexafluoro-2-ethoxypropane, 1,1,1,3,3,3-hexafluoro-2-n-propoxypropane, 1,1,1,3,3,3- Hexafluoro-2-isopropoxypropane, 1,1,1,3,3,3-hexafluoro-2-n-butoxypropane, 1,1,1,3,3,3-hexafluoro-2 -Tertiary butoxypropane, 1,1,1,3,3,4,4,4-octafluoro-2-methoxybutane and 1,1,1,3,3,4,4,4 -At least one of the group consisting of octafluoro-2-ethoxybutane. The substrate processing method according to claim 1 or 2, wherein the concentration of the hydrofluoroether in the second solvent is 90% by weight or more and 100% by weight or less. The substrate processing method according to claim 1 or 2, wherein the aforementioned alcohol is selected from methanol, ethanol, n-propanol, isopropanol, 1-butanol, isobutanol, secondary butanol, tertiary butanol, Propylene glycol monomethyl ether. The substrate processing method according to claim 1 or 2, wherein the aqueous cleaning solution is water. The substrate processing method according to claim 2, wherein the aforementioned fluorine solvent is selected from CF ₃ CF ₂ CH ₂ OCHF ₂ , CF ₃ CF ₂ OCH ₂ CF ₃ , CF ₃ CF ₂ CF ₂ OCH ₃ , (CF ₃ ) ₂ CFOCH ₃ , CF ₃ CF ₂ CF ₂ CF ₂ OCH ₃ , (CF ₃ ) ₂ CFCF ₂ OCH ₃ , CF ₃ CF ₂ (CF ₃ ) CFOCH ₃ , (CF ₃ ) ₃ COCH ₃ , CF ₃ CF ₂ CF ₂ CF ₂ OCH ₂ CH ₃ 、(CF ₃ ) ₂ CFCF ₂ OCH ₂ CH ₃ 、CF ₃ CF ₂ (CF ₃ )CFOCH ₂ CH ₃ 、(CF ₃ ) ₃ COCH ₂ CH ₃ 、(CF ₃ ) ₂ CFCF(OCH ₃ )CF ₂ CF ₃ , CHF ₂ CF ₂ OCH ₂ CF ₃ , C ₄ F ₉ H, C ₅ F ₁₁ H, C ₆ F ₁₃ H, C ₄ F ₉ CH ₂ CH ₃ , C ₆ F ₁₃ CH ₂ CH ₃ , CF ₃ CH ₂ CF ₂ CH ₃ , cC ₅ F ₇ H ₃ , CF ₃ CF ₂ CHFCHFCF ₃ , CF ₃ CH ₂ CHF ₂ , (CF ₃ CF ₂ CF ₂ CF ₂ ) ₃ N and perfluorohexane. A solvent containing hydrofluoroether represented by the following formula (1), "Chemical 3"

Rf ¹ and Rf ² are each independently a fluorine atom, a linear perfluoroalkyl group with a carbon number of 1 to 4 or a branched perfluoroalkyl group with a carbon number of 3 or 4, and R ³ is a straight chain with a carbon number of 1 or more and 4 or less. Chain alkyl, branched alkyl with 3 or 4 carbons, linear fluoroalkyl with 1 to 4 carbons, or branched fluoroalkyl with 3 or 4 carbons, at least one of ^{Rf 1} and Rf ^{2 is carbon} A straight-chain perfluoroalkyl group with a number of 1 to 4 or a branched perfluoroalkyl group with a carbon number of 3 or 4. The solvent according to claim 16, wherein the purity of the aforementioned hydrofluoroether is 99.0% or more and 100% or less. The solvent according to claim 17, wherein the aforementioned hydrofluoroether is selected from 1,1,1,3,3,3-hexafluoro-2-methoxypropane, 1,1,1,3,3,3 -Hexafluoro-2-ethoxypropane, 1,1,1,3,3,3-hexafluoro-2-n-propoxypropane, 1,1,1,3,3,3-hexafluoro-2 -Isopropoxypropane, 1,1,1,3,3,3-hexafluoro-2-n-butoxypropane, 1,1,1,3,3,3-hexafluoro-2-tertiary butane Oxypropane, 1,1,1,3,3,4,4,4-octafluoro-2-methoxybutane and 1,1,1,3,3,4,4,4-octafluoro- At least one of the group consisting of 2-ethoxybutane. The solvent according to claim 16, which is a cleaning solvent used to clean a substrate. The solvent according to claim 16, which is a cleaning solvent for drying a semiconductor substrate.

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