Cleaning liquid for removing particles, and cleaning method

Abstract

Provided is a cleaning liquid having a low global warming potential and having particle removing properties equal to or higher than that of a conventional hydrofluoroether. The present disclosure relates to a cleaning liquid for removing particles. The cleaning liquid contains hydrofluoroether, and the hydrofluoroether is a compound represented by general formula (1).

Description

Cleaning solution for particle removal and cleaning method

[0001] The present disclosure relates to a cleaning solution for removing particles and a cleaning method.

[0002] Methods for cleaning objects to be cleaned (objects to be cleaned) that use hydrofluoroethers are known, as described in Patent Documents 1 to 4. Among these, hydrofluoroethers such as methyl perfluoroisobutyl ether and methyl perfluoron-butyl ether are used as cleaning solutions for removing particles from objects to be cleaned (Non-Patent Document 1).

[0003] In the production processes of precision instruments, semiconductors, and the like, adhesion of particles to components can be a factor in reducing production yield. In the electronics industry, components are becoming increasingly smaller and more integrated, making particle removal from components essential in the production process. Here, in this specification, "particles" refers to fine particles whose diameter (particle size) measured by a particle classifier is on the order of 5000 nm or less, e.g., fine particles on the order of 5 nm to 5000 nm.

[0004] International Publication No. 93 / 09272 Japanese Patent Application Laid-Open No. 2020-132688 Japanese Patent Application Laid-Open No. 2022-41936 International Publication No. 2021 / 065428

[0005] Industrial Cleaning No. 15, published April 3, 2015

[0006] The global warming potential (GWP) of the cleaning solution using hydrofluoroether disclosed in Non-Patent Document 1 is ４ F ９ OCH ３ ) 320, product number "Novec7200" (manufactured by 3M, chemical formula C ４ F ９ O.C. ２ H ５ ) 55, product number "Novec7300" (manufactured by 3M, chemical formula C ６ F １３ OCH ３) is 210. An object of the present disclosure is to provide a cleaning liquid that has a low global warming potential and particle removal properties equal to or greater than those of these hydrofluoroethers.

[0007] One embodiment of the present disclosure is the cleaning solution of [Disclosure 1] to [Disclosure 5] below.

[0008] [Disclosure 1] A cleaning liquid for removing particles, the cleaning liquid containing a hydrofluoroether, the hydrofluoroether being a compound represented by the following general formula (1): Here, Rf １ and Rf ２ are each independently a fluorine atom, a perfluoroalkyl group having 1 to 6 carbon atoms, or a chlorofluoroalkyl group having 1 to 6 carbon atoms, and R ３ is an alkyl group having 1 to 6 carbon atoms or a fluoroalkyl group having 1 to 6 carbon atoms, and Rf １ and Rf ２ At least one of the groups is a perfluoroalkyl group having 1 to 6 carbon atoms, or a chlorofluoroalkyl group having 1 to 6 carbon atoms.

[0009] [Disclosure 2] The cleaning solution according to Disclosure 1, further comprising a lower alcohol.

[0010] [Disclosure 3] The cleaning liquid according to Disclosure 1 or 2, wherein the hydrofluoroether is 1,1,1,3,3,3-hexafluoro-2-methoxypropane, 1,1,1,3,3,3-hexafluoro-2-fluoromethoxypropane, 1,1,1,3,3,3-hexafluoro-2-ethoxypropane, 1,1,1,3,3,3-hexafluoro-2-n-propoxypropane, or 1,1,1,3,3,3-hexafluoro-2-isopropoxypropane. and at least one selected from the group consisting of 1,1,1,3,3,3-hexafluoro-2-n-butoxypropane, 1,1,1,3,3,3-hexafluoro-2-t-butoxypropane, 1,1,1,3,3,4,4,4-octafluoro-2-methoxybutane, 1,1,1,3,3,4,4,4-octafluoro-2-ethoxybutane, and 1,3-dichloro-1,1,3,3-tetrafluoro-2-methoxypropane.

[0011] [Disclosure 4] The cleaning liquid according to any one of Disclosures 1 to 3, wherein the hydrofluoroether is 1,1,1,3,3,3-hexafluoro-2-methoxypropane.

[0012] [Disclosure 5] The cleaning solution according to any one of Disclosures 1 to 4, wherein the volume resistivity at an applied voltage of 250 V is 10×10 ８ It is Ω·m or less.

[0013] Further, one embodiment of the present disclosure is a method for removing particles from an object to be cleaned, as set forth in [Disclosure 6] to [Disclosure 10] below.

[0014] [Disclosure 6] A method for removing particles from an object to be cleaned, comprising: step (3) of contacting a cleaning liquid with an object to be cleaned, the object having particles adhering to its surface; and step (4) of removing the cleaning liquid from the object to be cleaned, wherein step (4) is carried out by volatilizing the cleaning liquid at a pressure lower than saturated vapor pressure, and the cleaning liquid contains a hydrofluoroether, and the hydrofluoroether is a compound represented by the following general formula (1): Here, Rf １ and Rf ２ are each independently a fluorine atom, a perfluoroalkyl group having 1 to 6 carbon atoms, or a chlorofluoroalkyl group having 1 to 6 carbon atoms, and R ３ is an alkyl group having 1 to 6 carbon atoms or a fluoroalkyl group having 1 to 6 carbon atoms, and Rf １ and Rf ２ At least one of the groups is a perfluoroalkyl group having 1 to 6 carbon atoms, or a chlorofluoroalkyl group having 1 to 6 carbon atoms.

[0015] [Disclosure 7] The method for removing particles from an object to be cleaned according to Disclosure 6, wherein the cleaning liquid contains a lower alcohol.

[0016] [Disclosure 8] The method for removing particles from an object to be cleaned according to Disclosure 6 or 7, wherein the hydrofluoroether is 1,1,1,3,3,3-hexafluoro-2-methoxypropane, 1,1,1,3,3,3-hexafluoro-2-fluoromethoxypropane, 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- The fluorocarbon polymer is at least one selected from the group consisting of isopropoxypropane, 1,1,1,3,3,3-hexafluoro-2-n-butoxypropane, 1,1,1,3,3,3-hexafluoro-2-t-butoxypropane, 1,1,1,3,3,4,4,4-octafluoro-2-methoxybutane, 1,1,1,3,3,4,4,4-octafluoro-2-ethoxybutane, and 1,3-dichloro-1,1,3,3-tetrafluoro-2-methoxypropane.

[0017] [Disclosure 9] The method for removing particles from an object to be cleaned according to any one of Disclosures 6 to 8, wherein the hydrofluoroether is 1,1,1,3,3,3-hexafluoro-2-methoxypropane.

[0018] [Disclosure 10] The method for removing particles from an object to be cleaned according to any one of Disclosures 6 to 9, wherein the volume resistivity of the cleaning liquid at an applied voltage of 250 V is 10×10 ８ It is Ω·m or less.

[0019] The cleaning solution according to the present disclosure has a lower global warming potential than conventional cleaning solutions for removing particles using hydrofluoroether, and has particle removal properties equal to or greater than those of conventional cleaning solutions for removing particles using hydrofluoroether.

[0020] The present disclosure will be described in detail below, but the following description of the constituent elements is an example of an embodiment of the present disclosure, and the present disclosure is not limited to these specific details. Various modifications can be made within the scope of the gist of the present disclosure.

[0021] 1. Cleaning Solution The components contained in, and further that can be contained in, the cleaning solution of the present disclosure will be described below.

[0022] 1-1. Hydrofluoroether A hydrofluoroether is used as an essential component of the cleaning solution of the present disclosure. The hydrofluoroether according to this embodiment is a compound represented by the following formula (1). As will be explained below, the hydrofluoroether according to this embodiment contains carbon atoms, hydrogen atoms, oxygen atoms, and fluorine atoms, and may also contain chlorine atoms. The compound represented by formula (1) may be used alone, or two or more types may be used in combination. In formula (1), Rf １ and Rf ２ are each independently a fluorine atom, a perfluoroalkyl group having from 1 to 6 carbon atoms, or a chlorofluoroalkyl group having from 1 to 6 carbon atoms (preferably a linear perfluoroalkyl group having from 1 to 4 carbon atoms, a linear chlorofluoroalkyl group having from 1 to 4 carbon atoms, a branched perfluoroalkyl group having from 3 or 4 carbon atoms, or a branched chlorofluoroalkyl group having from 3 or 4 carbon atoms, because they have a lower global warming potential). １ and Rf ２ may be the same or different. ３ is an alkyl group having 1 to 6 carbon atoms, or a fluoroalkyl group having 1 to 6 carbon atoms. The alkyl group having 1 to 6 carbon atoms is preferably an alkyl group having 1 to 4 carbon atoms. Furthermore, the fluoroalkyl group having 1 to 6 carbon atoms is preferably a fluoroalkyl group having 1 to 4 carbon atoms. Here, Rf １ and Rf ２ At least one of (preferably Rf １ and Rf ２ and both of the above) are perfluoroalkyl groups having 1 to 6 carbon atoms, or chlorofluoroalkyl groups having 1 to 6 carbon atoms.

[0023] In formula (1), Rf １ and Rf ２are each independently a fluorine atom, a perfluoroalkyl group having from 1 to 6 carbon atoms, or a chlorofluoroalkyl group having from 1 to 6 carbon atoms. The perfluoroalkyl group having from 1 to 6 carbon atoms may be linear, branched, or cyclic. When the perfluoroalkyl group is branched or cyclic, the number of carbon atoms in the perfluoroalkyl group is 3 to 6. The perfluoroalkyl group having from 1 to 6 carbon atoms is preferably a perfluoroalkyl group having from 1 to 4 carbon atoms.

[0024] The chlorofluoroalkyl group having from 1 to 6 carbon atoms may be linear, branched, or cyclic. When the chlorofluoroalkyl group is branched or cyclic, the number of carbon atoms in the chlorofluoroalkyl group is 3 to 6. The chlorofluoroalkyl group having from 1 to 6 carbon atoms is preferably a chlorofluoroalkyl group having from 1 to 4 carbon atoms. Furthermore, in this specification, the chlorofluoroalkyl group having from 1 to 6 carbon atoms is preferably one in which all hydrogen atoms of the alkyl group are substituted with chlorine atoms and fluorine atoms.

[0025] Rf １ and Rf ２ At least one of (preferably Rf １ and Rf ２ and both of them) are perfluoroalkyl groups having from 1 to 6 carbon atoms, or chlorofluoroalkyl groups having from 1 to 6 carbon atoms, preferably perfluoroalkyl groups having from 1 to 4 carbon atoms, or chlorofluoroalkyl groups having from 1 to 4 carbon atoms, more preferably linear perfluoroalkyl groups having from 1 to 4 carbon atoms, or linear chlorofluoroalkyl groups having from 1 to 4 carbon atoms, and even more preferably linear perfluoroalkyl groups having from 1 to 4 carbon atoms.

[0026] Rf １ , Rf ２Examples of the linear, branched, or cyclic perfluoroalkyl group having from 1 to 6 carbon atoms include linear perfluoroalkyl groups having from 1 to 6 carbon atoms, such as a trifluoromethyl group, a pentafluoroethyl group, a heptafluoro-n-propyl group, a nonafluoro-n-butyl group, an undecafluoro-n-pentyl group, and a tridecafluoro-n-hexyl group; branched perfluoroalkyl groups having from 3 to 6 carbon atoms, such as a heptafluoroisopropyl group, a nonafluoroisobutyl group, a nonafluoro-sec-butyl group, and a nonafluoro-tert-butyl group; and cyclic perfluoroalkyl groups having from 3 to 6 carbon atoms, such as a pentafluorocyclopropyl group, a heptafluorocyclobutyl group, a nonafluorocyclopentyl group, and an undecafluorocyclohexyl group. Among these, linear perfluoroalkyl groups having from 1 to 6 carbon atoms are preferred, linear perfluoroalkyl groups having from 1 to 4 carbon atoms are more preferred, a trifluoromethyl group and a pentafluoroethyl group are even more preferred, and a trifluoromethyl group is particularly preferred.

[0027] Rf １ , Rf ２Examples of the linear, branched or cyclic chlorofluoroalkyl group having from 1 to 6 carbon atoms include a chlorodifluoromethyl group, a dichlorofluoromethyl group, a 1-chloro-1,2,2,2-tetrafluoroethyl group, a 1,2-dichloro-1,2,2-trifluoroethyl group, a 1,1-dichloro-2,2,2-trifluoroethyl group, a 3-chloro-1,1,2,2,3,3-hexafluoro-n-propyl group, a 2-chloro-1,1,2,3 ... -propyl group, 1-chloro-1,2,2,3,3,3-hexafluoro-n-propyl group, 1,2-dichloro-1,2,3,3,3-pentafluoro-n-propyl group, 2,3-dichloro-1,1,2,3,3-pentafluoro-n-propyl group, 1,3-dichloro-1,2,2,3,3-pentafluoro-n-propyl group, 3,3-dichloro-1,1,2,2,3-pentafluoro-n-propyl group, 4-chloro-1,1,2,2,3,3,4,4-octafluoro fluoro-n-butyl group, 3-chloro-1,1,2,2,3,4,4,4-octafluoro-n-butyl group, 2-chloro-1,1,2,3,3,4,4,4-octafluoro-n-butyl group, 2,3-dichloro-1,1,2,3,4,4,4-heptafluoro-n-butyl group, 5-chloro-1,1,2,2,3,3,4,4,5,5-decafluoro-n-pentyl group, 4-chloro-1,1,2,2,3,3,4,5,5,5-decafluoro-n-pentyl group, 4, linear chlorofluoroalkyl groups having from 1 to 6 carbon atoms, such as a 5-dichloro-1,1,2,2,3,3,4,5,5-nonafluoro-n-pentyl group, a 6-chloro-1,1,2,2,3,3,4,4,5,5,6,6-dodecafluoro-n-hexyl group, a 5-chloro-1,1,2,2,3,3,4,4,5,6,6,6-dodecafluoro-n-hexyl group, and a 5,6-dichloro-1,1,2,2,3,3,4,4,5,6,6-undecafluoro-n-hexyl group;Branched-chain chlorofluoroalkyl groups having 3 to 6 carbon atoms such as 1-chloro-2,2,2-trifluoro-1-(trifluoromethyl)ethyl group, 2-chloro-1,2,2-trifluoro-1-(trifluoromethyl)ethyl group, 1,2-dichloro-2,2-difluoro-1-(trifluoromethyl)ethyl group, 2,2-dichloro-1,2-difluoro-1-(trifluoromethyl)ethyl group, and 2-chloro-1-(chlorodifluoromethyl)-1,2,2-trifluoroethyl group; 2-chloro-1,2,3,3-tetrafluorocyclopropyl group, 2-chloro-1,2,3,3,4,4-hexafluorocyclobutyl group, 3-chloro-1,2,2,3,4,4-hexafluorocyclobutyl group, 2- Examples of cyclic chlorofluoroalkyl groups having 3 to 6 carbon atoms include a chloro-1,2,3,3,4,4,5,5-octafluorocyclopentyl group, a 3-chloro-1,2,2,3,4,4,5,5-octafluorocyclopentyl group, a 1-chloro-2,2,3,3,4,4,5,5,6,6-decafluorocyclohexyl group, a 2-chloro-1,2,3,3,4,4,5,5,6,6-decafluorocyclohexyl group, a 3-chloro-1,2,2,3,4,4,5,5,6,6-decafluorocyclohexyl group, a 4-chloro-1,2,2,3,3,4,5,5,6,6-decafluorocyclohexyl group, and a 3,4-dichloro-1,2,2,3,4,5,5,6,6-nonafluorocyclohexyl group. Among these, a linear chlorofluoroalkyl group having from 1 to 6 carbon atoms is preferred, a linear chlorofluoroalkyl group having from 1 to 4 carbon atoms is more preferred, and a chlorodifluoromethyl group is even more preferred.

[0028] In formula (1), R ３ is an alkyl group having 1 to 6 carbon atoms, or a fluoroalkyl group having 1 to 6 carbon atoms. The alkyl group having 1 to 6 carbon atoms may be linear, branched, or cyclic. When the alkyl group is branched or cyclic, the number of carbon atoms in the alkyl group is 3 to 6. The alkyl group having 1 to 6 carbon atoms is preferably an alkyl group having 1 to 4 carbon atoms.

[0029] The fluoroalkyl group having from 1 to 6 carbon atoms may be linear, branched, or cyclic. When the fluoroalkyl group is branched or cyclic, the number of carbon atoms in the fluoroalkyl group is from 3 to 6. The fluoroalkyl group having from 1 to 6 carbon atoms is preferably a fluoroalkyl group having from 1 to 4 carbon atoms.

[0030] R ３ is preferably a linear alkyl group having 1 to 4 carbon atoms, a branched alkyl group having 3 or 4 carbon atoms, a linear fluoroalkyl group having 1 to 4 carbon atoms, or a branched fluoroalkyl group having 3 or 4 carbon atoms, more preferably a linear alkyl group having 1 to 4 carbon atoms, or a branched alkyl group having 3 or 4 carbon atoms, and even more preferably a linear alkyl group having 1 to 4 carbon atoms.

[0031] R ３ Examples of the alkyl group having 1 to 6 carbon atoms include linear alkyl groups having 1 to 6 carbon atoms, such as methyl, ethyl, n-propyl, n-butyl, n-pentyl, and n-hexyl groups; branched alkyl groups having 3 to 6 carbon atoms, such as isopropyl, isobutyl, sec-butyl, and tert-butyl groups; and cyclic alkyl groups having 3 to 6 carbon atoms, such as cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl groups. Of these, methyl and ethyl groups are preferred.

[0032] R ３Examples of the fluoroalkyl group having from 1 to 6 carbon atoms include a linear fluoroalkyl group having from 1 to 6 carbon atoms, such as a monofluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a 1-fluoroethyl group, a 2-fluoroethyl group, a 1,2-difluoroethyl group, a 1,2,2-trifluoroethyl group, a 2,2,2-trifluoroethyl group, a 1,2,2,2-tetrafluoroethyl group, a 1,1,2,2,2-pentafluoroethyl group, or a 2,2,3,3,3-pentafluoro-n-propyl group; a 1,1,1,3,3,3-hexafluoroisopropyl group, a 1,1,2, Examples of fluoroalkyl groups include branched fluoroalkyl groups having from 3 to 6 carbon atoms, such as 3,3,3-hexafluoro-2-(trifluoromethyl)propyl and nonafluoro-tert-butyl; and cyclic fluoroalkyl groups having from 3 to 6 carbon atoms, such as 1-fluorocyclopropyl, 2-fluorocyclopropyl, 1-fluorocyclobutyl, 2-fluorocyclobutyl, 3-fluorocyclobutyl, 2-fluorocyclopentyl, 3-fluorocyclopentyl, 2-fluorocyclohexyl, 3-fluorocyclohexyl, and 4-fluorocyclohexyl groups.

[0033] Rf １ , Rf ２ , and R ３ Examples of the combination of Rf include the following: １ is a fluorine atom, Rf ２ is a trifluoromethyl group, R ３ is a methyl group, (b) Rf １ is a trifluoromethyl group, Rf ２ is a trifluoromethyl group, R ３ is a methyl group, (c) Rf １ is a trifluoromethyl group, Rf ２ is a pentafluoroethyl group, R ３ is a methyl group, (d) Rf １ is a trifluoromethyl group, Rf ２ is a trifluoromethyl group, R ３ is an ethyl group, (e) Rf １ is a trifluoromethyl group, Rf ２ is a pentafluoroethyl group, R ３ is an ethyl group, (f) Rf１ is a chlorodifluoromethyl group, Rf ２ is a chlorodifluoromethyl group, R ３ is a methyl group, and (g) Rf １ is a trifluoromethyl group, Rf ２ is a trifluoromethyl group, R ３ is a monofluoromethyl group

[0034] Specific examples of hydrofluoroethers 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, and 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-t-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, 1,1,1,3,3,4,4,5,5,6,6,7,7,7-tetradecafluoro-2-methoxyheptane, 1,1,1,3,3,4,4,5,5,6,6,7,7,8,8,8-hexadecafluoro-2-methoxyoctane, 1-chloro-1,1,3,3,3-pentafluoro-2-methoxypropane, 1,3-dichloro-1,1,3,3-tetrafluoro-2-methoxypropane, 1,3-dichloro-2-ethoxy-1,1,3,3-tetrafluoropropane, etc.

[0035] In one embodiment, the hydrofluoroether is selected from the group consisting of 1,1,1,3,3,3-hexafluoro-2-methoxypropane, 1,1,1,3,3,3-hexafluoro-2-fluoromethoxypropane, 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, It is preferable that at least one selected from the group consisting of 1,3,3,3-hexafluoro-2-n-butoxypropane, 1,1,1,3,3,3-hexafluoro-2-t-butoxypropane, 1,1,1,3,3,4,4,4-octafluoro-2-methoxybutane, 1,1,1,3,3,4,4,4-octafluoro-2-ethoxybutane, and 1,3-dichloro-1,1,3,3-tetrafluoro-2-methoxypropane is included. １ and Rf ２ Hydrofluoroethers in which a hydrogen atom is bonded to a carbon bonded to a carbon atom tend to exhibit lower GWP values ​​than hydrofluoroether isomers having the same chemical composition. For example, as shown in Table 1, among the hydrofluoroether (HFE-) 347 series having the same chemical composition, HFE-347mmz1 (1,1,1,3,3,3-hexafluoro-2-fluoromethoxypropane) which is branched and has a hydrogen atom on the branched chain has a smaller GWP-100 than the others, and similarly, among the hydrofluoroether (HFE-) 356 series having the same chemical composition, HFE-356mmz1 (1,1,1,3,3,3-hexafluoro-2-methoxypropane) which has a similar structure has the smallest GWP-100. The above GWP-100 refers to the value (100-year value) set forth in the Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change (IPCC).

[0036] Among the hydrofluoroethers, 1,1,1,3,3,3-hexafluoro-2-methoxypropane is particularly preferred. Among the hydrofluoroethers of the preferred embodiments described above, 1,1,1,3,3,3-hexafluoro-2-methoxypropane is preferred because it has a low global warming potential (GWP-100) of 8.13.

[0037] The fluorine content of the hydrofluoroether (compound represented by general formula (1)) is preferably 40% by mass to 70% by mass, more preferably 45% by mass to 66% by mass, and even more preferably 50% by mass to 65% by mass. This tends to result in better particle removal properties. Here, the fluorine content is calculated as "(number of fluorine atoms x 19) / molecular weight of hydrofluoroether" x 100 (%), and can be expressed as, for example, Rf １ is a trifluoromethyl group, Rf ２ is a trifluoromethyl group, R ３ is a methyl group (in this case the molecular formula is C ４ H ４ F ６ O), and the fluorine content is "(6×19) / 182"×100=63 mass %.

[0038] The content of the hydrofluoroether (compound represented by general formula (1)) in the cleaning solution is adjusted appropriately depending on the object to be cleaned and the cleaning conditions. The content is not particularly limited, but may be 30% by mass to 100% by mass, 60% by mass to 100% by mass, or 80% by mass to 100% by mass.

[0039] 1-2. Method for Producing Hydrofluoroethers Although there are no limitations on the method for producing the hydrofluoroethers, by utilizing a substitution reaction according to the following scheme, it is possible to obtain high-purity hydrofluoroethers in high yield under mild conditions. Specifically, a hydrofluoroether can be produced by reacting a readily available substituted alcohol (compound (2) in the scheme) with a substituted alkane or substituted fluoroalkane having a leaving group L (compound (3) in the scheme) in the presence of a base. Rf １ , Rf ２ , and R３ The definition of is the same as that of the hydrofluoroether described above.

[0040] Examples of the leaving group L include conjugate acid residues having a high pKa, such as trifluoromethanesulfonyl, methanesulfonyl, fluorosulfonyl, nonafluorobutanesulfonyl, chlorine, iodine, bromine, and paratoluenesulfonyl. Among them, substituted alkanes or substituted fluoroalkanes having chlorine as the leaving group L are preferred because they are relatively inexpensively available. In addition, the compound (2) can be reacted with a base such as dimethyl sulfate to form a substituted alkane or fluoroalkane of the formula: R ３ -O-SO ２ -O-R ３ (4) (R ３ The definition of the compound (4) is the same as that of the hydrofluoroether described above) to obtain a hydrofluoroether.

[0041] There is no limitation on the type of base, and examples thereof include carbonates and bicarbonates of alkali metals or Group 2 elements, such as sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, cesium carbonate, and cesium bicarbonate; nitrogen-containing heteroaromatic compounds such as pyridine and pyrazine; aromatic amines such as dialkylanilines; and aliphatic tertiary amines such as trialkylamines, dialkylpiperazines, and alkylpyrrolidines.

[0042] There are no limitations on the solvent used in the substitution reaction, and examples thereof include amide solvents such as N,N-dimethylformamide and N,N-dimethylacetamide, sulfur-containing solvents such as dimethyl sulfoxide, ketones such as ethyl methyl ketone, and ether solvents such as tetrahydrofuran and dioxane. Among these, amide solvents are preferred because they are stable under weakly basic conditions, have high polarity, and have a boiling point significantly different from that of hydrofluoroether.

[0043] An example of the procedure for producing a hydrofluoroether is as follows: A substituted alcohol is added to a mixture of a solvent and a base, and a substituted alkane or substituted fluoroalkane having a leaving group L in an amount equal to or slightly in excess of the substituted alcohol is added dropwise to this mixture. The reaction temperature can be appropriately selected from the ranges of 0°C to 50°C, 0°C to 40°C, or 10°C to 30°C. The dropping rate is appropriately adjusted so as not to cause the reaction to run away. The reaction time depends on the reactivity of the substituted alcohol, alkane, or fluoroalkane and the type of base, but can be selected from the ranges of, for example, 1 hour to 3 days, 4 hours to 1 day, or 10 hours to 20 hours. The progress of the reaction can be monitored by, for example, gas chromatography or １ H-nuclear magnetic resonance spectroscopy ( １ H-NMR), or １９ F-nuclear magnetic resonance spectroscopy ( １９ This can be confirmed by monitoring the concentration of the substituted alcohol using F-NMR.

[0044] After the reaction is complete, the added base and salts precipitated by the reaction are removed by filtration, and the residue is distilled under reduced pressure to obtain the target hydrofluoroether. The pressure during distillation may be, for example, from 10 kPa to 50 kPa. If necessary, further precision distillation may be carried out.

[0045] 1-3. Lower Alcohol A lower alcohol is a component that may be contained in the cleaning solution of the present disclosure. By including the lower alcohol in the cleaning solution, the volume resistivity of the cleaning solution can be reduced (volume resistivity will be described in detail in another section). The lower alcohol may be used alone or in combination of two or more types. The lower alcohol is not particularly limited as long as it has 5 or fewer carbon atoms, and may include at least one selected from the group consisting of isopropanol, ethanol, and methanol. Ethanol is particularly preferred. The content of the lower alcohol that may be contained in the cleaning solution is not particularly limited, but from the viewpoint of the flammability of the cleaning solution, the upper limit may be 20% by mass, or the upper limit may be 10% by mass or 5% by mass, and the lower limit may be 2% by mass.

[0046] 1-4. Other Components The cleaning solution of the present disclosure may contain aliphatic alcohols, aliphatic esters, aliphatic amines, aliphatic amides, fluoroolefins, haloolefins, etc., as long as the object of the present disclosure is not impaired. These may be used alone, or two or more types may be used in combination.

[0047] The cleaning solution of the present disclosure may contain water to the extent that it does not impair the objectives of the present disclosure. Furthermore, in view of the objectives of the present disclosure, it is preferable that the cleaning solution have a low particle content. The cleaning solution may have a particle count of preferably 10 particles / mL or less, more preferably 3 particles / mL or less, and even more preferably 1 particle / mL or less, with a particle size of 0.05 μm or more. In this specification, particle size refers to the diameter of particles measured using a particle classifier. Furthermore, the particle count refers to the number measured using a condensation particle counter equipped with a particle classifier.

[0048] The components, or the liquid after mixing the components, can be purified to achieve the above particle counts by passing them through a particle removal filter. The particle removal filter can be a filter using a polymer membrane as a filter material. For example, an UltiClean filter (for particles 0.05 μm to 0.2 μm) manufactured by Pall Corporation (East Hills, New York, USA), which has a membrane made of polytetrafluoroethylene (PTFE) and a housing made of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), can be used. Other filters can also be used as long as they are capable of removing the desired particle size. However, when using filters made of polypropylene (PP) or polyethylene (PE), contamination from the filter may occur depending on the type and manufacturer, so it is preferable to use a filter made of polytetrafluoroethylene (PTFE) and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA).

[0049] 1-5. Volume Resistivity of Cleaning Liquid According to Non-Patent Document 1, there is a correlation between volume resistivity and particle removal performance. Table 2 below shows the volume resistivity of conventional hydrofluoroethers, representative hydrofluoroethers in this disclosure, and mixtures thereof with ethanol at an applied voltage of 250 V. In this disclosure, volume resistivity refers to that obtained under the following measurement conditions. <Measurement Conditions> 50 ml of sample (liquid) is placed in a container / counter electrode, and the main electrode is inserted and connected to a measuring instrument. The current value when a voltage is applied under certain conditions is measured, and the volume resistivity R is calculated according to Ohm's law. ｖ Calculate the volume resistance [Ω] using the obtained value of volume resistance using the following formula The volume resistivity is calculated by: ０ is the capacitance (56.4 pF) between the electrodes when no sample is placed. Other conditions are as follows: Test equipment: ULTRA HIGH RESISTANCE METER R8340A (manufactured by ADC Corporation), SAMPLE CHAMBER TR44 (manufactured by ADVANTEST Corporation) Electrode shape and arrangement: Main electrode φ42 mm x 70 mm, guard electrode φ42 mm x 7 mm (2 electrodes), counter electrode φ45 mm x 145 mm Distance between main electrode and guard electrode: 1 mm, distance between main electrode and counter electrode: 1.5 mm Applied voltage: DC 250 V Voltage application time: 1 minute Measurement environment: 22°C, humidity 60%

[0050] The hydrofluoroethers of the present disclosure can be understood to have, unexpectedly, a sufficiently lower volume resistivity and superior particle removal properties than conventional hydrofluoroethers. In this specification, the expression "a hydrofluoroether has excellent particle removal properties" means that when the hydrofluoroether is used to clean an object to be cleaned, the hydrofluoroether has excellent particle removal properties from the object to be cleaned.

[0051] The cleaning solution of the present disclosure preferably has a low volume resistivity, and the value is 10×10 at an applied voltage of 250 V. ８ Ω·m or less, preferably 9×10 ８ The lower limit is not particularly limited, but may be 1×10 ４It may be Ω·m or more.

[0052] 2. Method for Removing Particles from an Object to be Cleaned The method for removing particles from an object to be cleaned of the present disclosure includes the step (3) of bringing the cleaning liquid of the present disclosure into contact with the object to be cleaned, having particles adhering to its surface, and the step (4) of removing the cleaning liquid from the object to be cleaned, but preferably includes the step (1) of preparing an object to be cleaned, having particles adhering to its surface, the step (2) of preparing the cleaning liquid of the present disclosure, the step (3) of bringing the cleaning liquid into contact with the object to be cleaned, and the step (4) of removing the cleaning liquid from the object to be cleaned.

[0053] 2-1. Step (1) In the present disclosure, examples of the object to be cleaned include semiconductor substrates such as silicon substrates, image sensor substrates, etc. Particles adhering to the object to be cleaned may be derived from, for example, residual CMP slurry or shavings used in the planarization step of the semiconductor manufacturing process, or from a metal mask used in vapor deposition of an organic film during circuit formation on an image sensor substrate.

[0054] 2-2. Step (2) The cleaning solution of the present disclosure can be prepared by mixing the hydrofluoroether of the present disclosure with the above-mentioned lower alcohol and other components as desired. Note that the hydrofluoroether of the present disclosure itself may also be used as the cleaning solution of the present disclosure.

[0055] 2-3. Step (3) The method of bringing the cleaning solution of the present disclosure into contact with the object to be cleaned can be selected appropriately depending on the object to be cleaned. For example, a method of immersing the object to be cleaned in the cleaning solution in a tank, a method of contacting the object to be cleaned with the cleaning solution by spraying, spraying, showering, etc., or a method of applying a mist can be used. When the cleaning solution comes into contact with the object to be cleaned, ultrasonic waves may be applied, or the object may be heated (for example, heated to near the boiling point of the cleaning solution). Step (3) removes particles adhering to the surface of the object to be cleaned.

[0056] 2-4. Step (4) After step (3) is performed, the method for removing the cleaning solution from the object to be cleaned can be selected appropriately depending on the object to be cleaned. However, the remaining cleaning solution after it has been removed from the object to be cleaned by its own weight can be removed by exposing it to dry air or dry nitrogen and evaporating it. Alternatively, it can be replaced with a solution for another purpose. Among these methods, volatilization (evaporative removal) of the cleaning solution at less than the saturated vapor pressure is preferred. When evaporating, the cleaning solution vapor can be removed from the room containing the object to be cleaned by ventilating dry air or dry nitrogen, or by reducing the pressure in the room containing the object to be cleaned and returning it to atmospheric pressure with dry air or dry nitrogen. If particles are present in the dry air or dry nitrogen, they may adhere to the object to be cleaned. Therefore, it is desirable to remove the particles using a HEPA filter or the like before introducing the dry air or dry nitrogen into the room containing the object to be cleaned. To promote evaporation of the cleaning solution, the dry air or dry nitrogen can be heated before being introduced into the room containing the object to be cleaned. The upper limit of the temperature of the dry air or dry nitrogen should be set depending on the object to be cleaned, but is usually 20°C or higher and 120°C or lower, preferably 30°C or higher and 80°C or lower.

[0057] Hereinafter, the present disclosure will be described in further detail with reference to examples and comparative examples, but the scope of the present disclosure is not limited in any way by these examples and comparative examples.

[0058] (1) Preparation of objects to be cleaned with particles adhering to their surfaces A silicon wafer (4-inch, P-type, manufactured by Samco Technology) was coated with 3 g of an ethanol solution containing 0.0017 mass% standard particles (DUKES STANDARD™ manufactured by Therm Scientific, product number 4009A (particle size 1.0 μm), material: polystyrene, concentration 1 wt%) diluted 580 times in ethanol by spin coating (200 rpm). After coating the silicon wafer with the specified ethanol solution, the wafer was rotated for 30 seconds to volatilize the ethanol. An object to be cleaned with particles adhering to its surface was prepared for each cleaning solution to be tested.

[0059] (2) Particle Removal Test The object to be cleaned, prepared in (1) above and having particles adhering to its surface, was immersed in each of the cleaning solutions (25°C) shown in Table 2, and ultrasonic waves were applied for 5 minutes. The object to be cleaned was then removed from the cleaning solution and allowed to stand. After confirming that the cleaning solution had evaporated from the cleaning solution, the object to be cleaned was observed at 1000x magnification using an optical microscope equipped with a digital imaging element. As a result, no particles were observed on the object to be cleaned, regardless of whether it was immersed in cleaning solution #1, #2, or #3.

[0060] This application claims priority under the Paris Convention or the laws of countries that have adopted it, based on Japanese Patent Application No. 2023-178093 filed on October 16, 2023. The contents of that application are incorporated herein by reference in their entirety.

Claims

1. A cleaning liquid for removing particles, comprising a hydrofluoroether, the hydrofluoroether being a compound represented by the following general formula (1). Here, Rf １ and Rf ２ each independently represents a fluorine atom, a perfluoroalkyl group having 1 to 6 carbon atoms, or a chlorofluoroalkyl group having 1 to 6 carbon atoms; R ３ is an alkyl group having 1 to 6 carbon atoms or a fluoroalkyl group having 1 to 6 carbon atoms; Rf １ and Rf ２ At least one of the groups is a perfluoroalkyl group having 1 to 6 carbon atoms, or a chlorofluoroalkyl group having 1 to 6 carbon atoms.

2. The cleaning solution of claim 1, further comprising a lower alcohol.

3. The hydrofluoroether is 1,1,1,3,3,3-hexafluoro-2-methoxypropane, 1,1,1,3,3,3-hexafluoro-2-fluoromethoxypropane, 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-isopropoxypropane, 3. The cleaning solution according to claim 1, which is at least one selected from the group consisting of 1,3-dichloro-1,1,3,3-tetrafluoro-2-methoxypropane, 1,1,1,3,3,4,4,4-hexafluoro-2-n-butoxypropane, 1,1,1,3,3,3-hexafluoro-2-t-butoxypropane, 1,1,1,3,3,4,4,4-octafluoro-2-methoxybutane, 1,1,1,3,3,4,4,4-octafluoro-2-ethoxybutane, and 1,3-dichloro-1,1,3,3-tetrafluoro-2-methoxypropane.

4. A cleaning solution according to any one of claims 1 to 3, wherein the hydrofluoroether is 1,1,1,3,3,3-hexafluoro-2-methoxypropane.

5. The volume resistivity at an applied voltage of 250 V is 10 x 10 ８ The cleaning solution according to any one of claims 1 to 4, having a resistance of Ω·m or less.

6. A method for removing particles from an object to be cleaned, comprising: a step (3) of contacting a cleaning liquid with the object to be cleaned having particles adhering to its surface; and a step (4) of removing the cleaning liquid from the object to be cleaned, wherein the step (4) is carried out by volatilizing the cleaning liquid at a pressure less than the saturated vapor pressure, and the cleaning liquid contains a hydrofluoroether, and the hydrofluoroether is a compound represented by the following general formula (1). Here, Rf １ and Rf ２ each independently represents a fluorine atom, a perfluoroalkyl group having 1 to 6 carbon atoms, or a chlorofluoroalkyl group having 1 to 6 carbon atoms; R ３ is an alkyl group having 1 to 6 carbon atoms or a fluoroalkyl group having 1 to 6 carbon atoms; Rf １ and Rf ２ At least one of the groups is a perfluoroalkyl group having 1 to 6 carbon atoms, or a chlorofluoroalkyl group having 1 to 6 carbon atoms.

7. The method for removing particles from an object to be cleaned according to claim 6, wherein the cleaning liquid contains a lower alcohol.

8. The hydrofluoroether is 1,1,1,3,3,3-hexafluoro-2-methoxypropane, 1,1,1,3,3,3-hexafluoro-2-fluoromethoxypropane, 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 8. The method for removing particles from an object to be cleaned according to claim 6 or 7, wherein the fluorocarbon is at least one selected from the group consisting of 1,1,1,3,3,3-hexafluoro-2-t-butoxypropane, 1,1,1,3,3,4,4,4-octafluoro-2-methoxybutane, 1,1,1,3,3,4,4,4-octafluoro-2-ethoxybutane and 1,3-dichloro-1,1,3,3-tetrafluoro-2-methoxypropane.

9. The method for removing particles from an object to be cleaned according to any one of claims 6 to 8, wherein the hydrofluoroether is 1,1,1,3,3,3-hexafluoro-2-methoxypropane.

10. The volume resistivity of the cleaning solution at an applied voltage of 250 V is 10×10 ８ The method for removing particles from an object to be cleaned according to any one of claims 6 to 9, wherein the resistance is Ω·m or less.

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