Manufacturing method of high purity propylene glycol monomethyl ether acetate for semiconductors used in photoresist process

Abstract

The present invention provides a method for producing high-purity propylene glycol monomethyl ether acetate for semiconductors, comprising the steps of distilling and purifying raw material propylene glycol monomethyl ether acetate and cooling the distilled and purified propylene glycol monomethyl ether acetate by passing it through a cooler. At this time, high-purity propylene glycol monomethyl ether acetate can be produced by maintaining the dissolved oxygen content in the propylene glycol monomethyl ether acetate at less than 1.0 ppm during the distillation and purification steps and the cooling step, and maintaining the temperature of the cooler at 40 ℃ or lower.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing propylene glycol monomethyl ether acetate, and more specifically, to a method for manufacturing high-purity propylene glycol monomethyl ether acetate for semiconductors used in a photoresist process using an EUV / ArF light source. Background Technology

[0002] In the era of the Fourth Industrial Revolution, semiconductors are key components used in artificial intelligence, smart devices, automobiles, the Internet of Things, and 5G. As semiconductors are also being incorporated into small mobile devices and wearable devices, semiconductor companies are focusing on miniaturization.

[0003] Fine circuit patterns, such as those in small semiconductor integrated circuits, are manufactured by a method in which a photoresist containing a photosensitive compound and a solvent is uniformly applied to a conductive metal film or oxide film formed on a substrate using a spin coating method, followed by exposure, development, etching, and stripping processes to realize the desired fine circuit pattern.

[0004] At this stage, the subsequent photolithography process is implemented by using extreme ultraviolet (EUV) light to finely expose the desired pattern to the coating film, so it is highly sensitive to external and internal contamination.

[0005] Therefore, unnecessary photoresist residues and other contaminants applied to the edges or back surfaces of the substrate during the coating process must be removed, as they can become critical contaminants in the subsequent photolithography process. To remove these contaminants, thinners have been used in the edge bead removing (EBR) and resist reducing coating (RRC) processes.

[0006] Recently, as semiconductor integration density has increased, photoresists utilizing extreme ultraviolet (EUV) light sources are being applied. As the impact of photoresist usage on integrated circuit manufacturing costs has grown, there has been a continuous demand to reduce photoresist usage to cut costs.

[0007] In response to these demands, the RRC (Reducing Resist Coating) process has been applied, which involves treating the substrate surface with a thinner before applying the photoresist to enable even coating across the entire surface of the substrate using only a small amount of photoresist. As integration density increases and the diameter of substrates (wafers) grows, the importance of the RRC process is growing; consequently, there is a demand for the development of thinners that can fully perform the existing EBR process while offering excellent RRC performance.

[0008] The most important substance among the thinner compositions used in these RRC and EBR processes is propylene glycol monomethyl ether acetate (hereinafter also referred to as PGMEA).

[0009] Materials used in micro-semiconductor processes, particularly in photoresist processes using ArF or EUV light sources, have very strict requirements regarding purity, moisture, acidity, etc. For example, semiconductor-grade PGMEA is required to have a purity of 99.999% or higher, an acidity of 20 ppm or lower, and a moisture content of 50 ppm or lower.

[0010] PGMEA is prone to decomposing into aldehydes and methyl formate in the presence of oxygen. Therefore, in order to produce high-purity PGMEA, it is necessary to prevent PGMEA from decomposing into aldehydes and methyl formate under oxygen (O2) to prevent these substances from acting as impurities.

[0011] In addition, if the acid content remaining in the PGMEA used before and after the photoresist coating in the photolithography process is high, it affects the decomposition rate or curing rate of the photoresist (PR) resin and can react with water-soluble alkaline solutions such as KOH and TMAH used as developers, acting as a factor in causing defects in the chip and corroding semiconductor equipment.

[0012] Therefore, to minimize the impact on the precision of the pattern formation process in the photoresist process, it is crucial to use high-purity PGMEA and simultaneously minimize the residual acid content. The problem to be solved

[0013] The present invention aims to provide a method for producing high-purity propylene glycol monomethyl ether acetate for semiconductors used in photoresist processes by controlling the amount of dissolved oxygen in PGMEA, the temperature of the cooler, and whether an antioxidant is added. means of solving the problem

[0014] In one aspect, the present invention provides a method for producing high-purity propylene glycol monomethyl ether acetate for semiconductors, comprising the steps of: distilling and purifying raw material propylene glycol monomethyl ether acetate; and passing the distilled and purified propylene glycol monomethyl ether acetate through a cooler to cool it. At this time, oxygen is removed during distillation and purification so that the dissolved oxygen content in the propylene glycol monomethyl ether acetate is maintained at less than 1.0 ppm during the distillation and purification steps.

[0015] In the above distillation purification step and cooling step, the dissolved oxygen content in the propylene glycol monomethyl ether acetate is maintained at less than 1.0 ppm, and the temperature of the cooler is maintained at 40 ℃ or lower, preferably 20~30 ℃ or 30~40 ℃.

[0016] In another aspect, the method further includes the step of storing the propylene glycol monomethyl ether acetate that has passed through the cooler in a storage container, and it is preferable to maintain the dissolved oxygen content in the propylene glycol monomethyl ether acetate in the storage container at less than 1.0 ppm.

[0017] Preferably, an antioxidant can be added to the storage container at a concentration of 10 ppm or less.

[0018] The antioxidants include 2,6-di-tert-butyl-4-methylphenol (BHT), 4-tert-butyl catechol (TBC), p-methoxyphenol (MEHQ), 4-tert-butylphenol (TBP), HQ (Hydroquinone), tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] methane, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-, C7-9-branched alkyl esters, triethylene glycol-bis-3-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate, In the group consisting of thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] One or more can be selected.

[0019] The above high-purity propylene glycol monomethyl ether acetate does not contain acetaldehyde and methyl formate and can be used in a photoresist process using an EUV or ArF light source. Effects of the invention

[0020] According to the present invention, high-purity propylene glycol monomethyl ether acetate for semiconductors used in photoresist processes can be produced by controlling the amount of dissolved oxygen in PGMEA, the temperature of the cooler, and whether an antioxidant is added, so the yield of the semiconductor manufacturing process can be improved and the defect rate of the microprocess can be lowered, thereby improving the productivity of the semiconductor. Specific details for implementing the invention

[0021] Unless otherwise specifically defined, all terms in this specification have the same general meaning as understood by a person skilled in the art to which the present invention pertains, and in the event of a conflict with the meaning of a term used in this specification, the definition used in this specification shall prevail.

[0022] Throughout the specification, when a part is described as 'comprising' a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0023] In describing the present invention, if it is determined that a detailed description of related known components or functions may obscure the essence of the invention, such detailed description is omitted.

[0024] The term 'propylene glycol monomethyl ether acetate' as used in this specification may be abbreviated as PGMEA.

[0025] The term 'high purity' as used in this specification means 99.999% or higher, i.e., a purity of 5N or higher.

[0026] The present invention will be described in detail below.

[0027] According to one embodiment of the present invention, the present invention provides a method for producing high-purity propylene glycol monomethyl ether acetate for semiconductors, comprising the steps of distilling and purifying raw material propylene glycol monomethyl ether acetate (PGMEA), and cooling the distilled and purified propylene glycol monomethyl ether acetate by passing it through a cooler.

[0028] According to another embodiment of the present invention, the step of storing the propylene glycol monomethyl ether acetate that has passed through the cooler in a storage container may be further included.

[0029] In addition, preferably, a step of purging with nitrogen may be included prior to the distillation purification step to minimize the oxygen content present in all facilities or equipment, such as distillation towers, piping, coolers, and storage containers.

[0030] First, we will explain the process by which the raw material PGMEA is decomposed and impurities are generated.

[0031] The raw material PGMEA contains oxygen, moisture, and other impurities. In particular, PGMEA contains up to 9 ppm of dissolved oxygen (saturated), and decomposition reactions caused by moisture and oxygen in the PGMEA can lead to the formation of impurities. Therefore, in order to manufacture high-purity PGMEA, it is necessary to suppress the formation of such impurities as much as possible.

[0032] The hydrolysis reaction proceeds as shown in Reaction Scheme 1 below due to the moisture contained in the raw material PGMEA.

[0033] <Reaction Equation 1>

[0034]

[0035]

[0036] As can be seen from Reaction Scheme 1 above, when PGMEA is hydrolyzed, propylene glycol monomethyl ether and acetic acid are produced, both of which act as impurities. In addition, the impurity propylene glycol monomethyl ether is decomposed into aldehydes, dimethyl ethers, etc. by radicals.

[0037] Ultimately, propylene glycol monomethyl ether and acetic acid are produced by the moisture in PGMEA, and an aldehyde is produced by the radical reaction of propylene glycol monomethyl ether.

[0038] In addition, the aldehyde produced by hydrolysis reacts with oxygen as shown in Reaction Scheme 2 below to produce methyl formate and acetic acid.

[0039] <Reaction Equation 2>

[0040]

[0041] As can be seen from the above reaction schemes 1 and 2, the raw material propylene glycol monomethyl ether acetate can produce various impurities such as acetaldehyde, methyl formate, and acetic acid through hydrolysis reactions, radical reactions, oxidation reactions, etc.

[0042] In order to produce high-purity propylene glycol monomethyl ether acetate suitable for semiconductors, a distillation purification process is generally carried out, but if the dissolved oxygen concentration in PGMEA is high, it is difficult to produce high-purity PGMEA with only a simple distillation purification process.

[0043] Therefore, it is necessary to appropriately control the moisture and oxygen content and suppress radical generation so that the above reaction equation does not proceed.

[0044] In one embodiment, the present invention suppresses the generation of radicals (R·) by appropriately controlling the temperature during the cooling step, and maintains a low dissolved oxygen concentration (content) by purging nitrogen during the distillation purification step and the cooling step.

[0045] In addition, we propose a method to maintain a low dissolved oxygen concentration (content) by purging nitrogen during the product storage stage, as well as to prevent oxidation by adding an antioxidant.

[0046] Hereinafter, a method for manufacturing and / or purifying high-purity propylene glycol monomethyl ether acetate according to an embodiment of the present invention will be described in detail.

[0047] First, prepare the raw material PGMEA. As seen above, this raw material contains various unknown impurities and moisture, and in particular, the dissolved oxygen content can be up to 9 ppm.

[0048] Next, to reduce the dissolved oxygen content in the PGMEA, the distillation tower, distillation piping, cooler, and storage vessel are replaced with nitrogen (N2). That is, before carrying out the process, nitrogen is purged from the entire facility or equipment to replace the air (oxygen) with nitrogen, and nitrogen is also purged during the process to properly control the dissolved oxygen content in the PGMEA.

[0049] For example, although the amount of dissolved oxygen in PGMEA decreases during the distillation step, oxygen in the equipment may be extracted by purging with nitrogen to minimize the re-dissolution of the lost oxygen. However, since any method is sufficient to maintain the dissolved oxygen content in PGMEA at an appropriate level, the present invention is not limited to the method of controlling the dissolved oxygen content by purging with nitrogen.

[0050] It is necessary to reduce the amount of dissolved oxygen in PGMEA to less than 1 ppm, preferably 0.7 ppm or less. The dissolved oxygen concentration in the facility was measured using an Oxigen Microsensor (UNISENSE, OX-25-107692).

[0051] Meanwhile, the maximum allowable amount of dissolved oxygen in PGMEA is correlated with the temperature of the cooler at the downstream end of the distillation process.

[0052] The temperature of the cooler can be maintained at 40°C or lower, preferably 20 to 40°C, more preferably 20 to 30°C or 30 to 40°C. By introducing a cooler to control the temperature, it is possible not only to prevent the radical reaction from proceeding but also to determine an appropriate amount of acceptable dissolved oxygen in PGMEA.

[0053] For example, when the temperature of the cooler is maintained at 20 to 30 ℃, the dissolved oxygen content in PGMEA is maintained at less than 1.0 ppm, preferably 0.7 ppm or less, and when the temperature of the cooler is maintained at 30 to 40 ℃, the dissolved oxygen content in PGMEA is maintained at less than 0.5 ppm, preferably 0.3 ppm or less.

[0054] Therefore, it can be seen that the higher the temperature of the cooler, the lower the dissolved oxygen concentration in PGMEA must be.

[0055] After determining the permissible dissolved oxygen based on the temperature of the cooler before the distillation purification step, the distillation tower, distillation piping, cooler, and storage vessel are replaced with nitrogen (N2) to maintain the dissolved oxygen content in PGMEA appropriately.

[0056] Next, a distillation purification process is carried out according to conventional methods. For example, a tray column or a packed column may be used in the distillation process, and distillation may be performed at 80 to 140°C, preferably 80 to 100°C.

[0057] Next, the distilled and purified PGMEA is passed through a cooler to lower its temperature. By lowering the temperature in this way, the radical reaction can be suppressed. As described above, it is desirable to maintain the temperature of the cooler at 40°C or lower, but considering the relationship with the dissolved oxygen content, it may be maintained at 20-30°C or 30-40°C.

[0058] The purified PGMEA that has passed through the cooler is stored in a storage container. At this time, an antioxidant may be added to prevent the formation of impurities when stored in the container after distillation.

[0059] The antioxidant may be a phenolic antioxidant, specifically 2,6-di-tert-butyl-4-methylphenol (BHT), 4-tert-butyl catechol (TBC), p-methoxyphenol (MEHQ), 4-tert-butylphenol (TBP), HQ (Hydroquinone), tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-, C7-9-branched alkyl esters, triethylene glycol-bis-3-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate, thiodiethylene One or more may be selected from the group consisting of bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], but are not limited thereto.

[0060] Since the above antioxidant can act as an impurity if added in amounts greater than 10 ppm, it is desirable to add up to a maximum of 10 ppm.

[0061] If an antioxidant is added to the storage container, the dissolved oxygen in PGMEA can be maintained at less than 1.0 ppm, preferably less than 0.7 ppm, even if the temperature of the cooler is maintained at 30 to 40 ℃. That is, even if the temperature of the cooler is maintained at a somewhat high level, the allowable oxygen content in PGMEA can be increased by adding an antioxidant to the storage container.

[0062] The present invention will be described in more detail below through examples. These examples are merely illustrative of the present invention, and therefore the scope of the present invention is not limited by these examples.

[0063] 1. When antioxidants are not added

[0064] <Example 1>

[0065] After distilling and purifying the raw material PGMEA in a distillation tower with an internal temperature of 100 ℃, it is passed through a cooler maintaining a temperature of 20~30 ℃, and the cooled purified PGMEA is transferred to a storage container for storage. At this time, the dissolved oxygen content in the PGMEA in the distillation tower, cooler, and storage container is maintained at 0.3 ppm.

[0066] <Examples 2> to <Examples 4>

[0067] It is identical to Example 1 above, except that the dissolved oxygen content in PGMEA in the distillation tower, cooler, and storage container and the temperature of the cooler are maintained as shown in Table 1 below.

[0068] <Comparative Example 1> to <Comparative Example 5>

[0069] It is identical to Example 1 above, except that the dissolved oxygen content in the PGMEA in the distillation tower, cooler, and storage container is maintained as shown in Table 1 below.

[0070] In Examples 1 to 4 and Comparative Examples 1 to 5, the PGMEA in the storage container was sampled and the content of propylene glycol monomethyl ether acetate, acetaldehyde, methyl formate, and other impurities was measured using Gas Chromatoglyph, and the results are shown in Table 1.

[0071] Dissolved oxygen content (ppm) Cooler temperature (°C) Acetaldehyde content (ppm) Methylformate content (ppm) Other impurities (ppm) water Example 1 0.3 20~30 N / D N / D 6 99.9994 Example 2 0.5 20~30 N / D N / D 7 99.9993 Example 3 0.7 20~30 N / D N / D 7 99.9993 Example 4 0.3 30~40 N / D N / D 7 99.9993 Comparative Example 1 1 20~30 3 3 8 99.9986 Comparative Example 2 5 20~30 6 7 7 99.9980 Comparative Example 3 9 20~30 13 21 20 99.9946 Comparative Example 4 0.5 30~40 4 4 11 99.9981 Comparative Example 5 0.7 30~40 7 7 12 99.9977

[0072] (N / D: not detected)

[0073] Looking at Table 1 above, it can be seen that in the case of Examples 1 to 3, when the temperature of the cooler is 20 to 30 ℃ and the dissolved oxygen contained in propylene glycol monomethyl ether acetate is maintained at less than 1.0 ppm, preferably 0.3 to 0.7 ppm, acetaldehyde and methyl formate are not produced.

[0074] In the case of Comparative Examples 1 to 3, it can be seen that when the dissolved oxygen content is 1 ppm or higher, acetaldehyde and methyl formate are generated by radicals produced from propylene glycol monomethyl ether, which is part of the impurity. In addition, it can be seen that due to the generation of impurities, the purity of propylene glycol monomethyl ether acetate deviates from the standard of 99.999% or higher for propylene glycol monomethyl ether acetate for EUV semiconductors.

[0075] Comparing Example 4, Comparative Examples 4 and 5, it can be seen that when the temperature of the cooler rises to 30 to 40°C, acetaldehyde and methyl formate are not produced only when the dissolved oxygen is 0.3 ppm, while acetaldehyde and methyl formate are produced as impurities when the dissolved oxygen is 0.5 ppm or higher. In addition, it can be seen that due to the formation of impurities, the purity of propylene glycol monomethyl acetate deviates from the standard of 99.999% or higher for propylene glycol monomethyl ether acetate for EUV semiconductors.

[0076] Accordingly, looking at Examples 1 to 4 and Comparative Examples 1 to 5, it can be seen that the formation of acetaldehyde and methyl formate is suppressed when the dissolved oxygen content in PGMEA is low and the temperature of the cooler is low.

[0077] 2. When antioxidants are added

[0078] <Example 5>

[0079] After distilling and purifying the raw material PGMEA in a distillation tower with an internal temperature of 100 ℃, it is passed through a cooler maintaining a temperature of 30 to 40 ℃, and the cooled purified PGMEA is transferred to a storage container for storage. At this time, the dissolved oxygen content in the PGMEA in the distillation tower, cooler, and storage container is maintained at 0.5 ppm, and 10 ppm of the antioxidant BHT is added to the storage container.

[0080] <Example 6>

[0081] It is identical to Example 5 except that the dissolved oxygen content in PGMEA was maintained at 0.7 ppm.

[0082] <Example 7>

[0083] It is identical to Example 5 except that 10 ppm of the antioxidant TBC was added.

[0084] <Example 8>

[0085] It is identical to Example 5 except that the dissolved oxygen content in PGMEA is maintained at 0.7 ppm and 10 ppm of the antioxidant TBC is added.

[0086] <Example 9>

[0087] It is identical to Example 5 except that 10 ppm of the antioxidant SONGNOX 1010 (tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane) was added.

[0088] <Comparative Example 6>

[0089] It is identical to Example 5 except that the dissolved oxygen content in PGMEA was maintained at 1 ppm.

[0090] <Comparative Example 7>

[0091] It is identical to Example 5 except that the dissolved oxygen content in PGMEA was maintained at 5 ppm.

[0092] <Comparative Example 8>

[0093] It is identical to Example 5 except that the dissolved oxygen content in PGMEA was maintained at 1 ppm.

[0094] <Comparative Example 9>

[0095] It is identical to Example 5 except that the dissolved oxygen content in PGMEA is maintained at 5 ppm and 10 ppm of TBC is added as an antioxidant.

[0096] In Examples 5 to 9 and Comparative Examples 6 to 9, the PGMEA in the storage container was sampled and the content of propylene glycol monomethyl ether acetate, acetaldehyde, methyl formate, and other impurities was measured using Gas Chromatoglyph, and the results are shown in Table 2.

[0097] Dissolved oxygen content (ppm) Cooler temperature (°C) Antioxidant (ppm) Acetaldehyde (ppm) Methyl formate (ppm) Other impurities (ppm) water Example 5 0.5 30~40 10 N / D N / D 6 99.9994 Example 6 0.7 30~40 10 N / D N / D 8 99.9992 Example 7 0.5 30~40 10 N / D N / D 7 99.9993 Example 8 0.7 30~40 10 N / D N / D 8 99.9993 Example 9 0.5 30~40 10 N / D N / D 8 99.9992 Comparative Example 6 1 30~40 10 3 2 9 99.9981 Comparative Example 7 5 30~40 10 5 5 10 99.9980 Comparative Example 8 1 30~40 10 4 3 14 99.9979 Comparative Example 9 5 30~40 10 5 4 12 99.9979

[0098] (N / D: not detected)

[0099] Looking at Table 2 above, it can be seen that in the case of Examples 5 and 6, when the cooler temperature rises to 30~40℃ and the dissolved oxygen is 0.5~0.7 ppm, 10 ppm of the antioxidant Butylated hydroxytoluene (hereinafter BHT) is added, acetaldehyde and methyl formate are not produced.

[0100] On the other hand, in the case of Comparative Examples 6 and 7, it can be seen that when the dissolved oxygen is 1 ppm or higher, the formation of impurities such as acetaldehyde and methyl formate is not suppressed even when BHT is added.

[0101] Therefore, it can be seen that when BHT, an antioxidant, is added, the dissolved oxygen concentration in PGMEA is maintained at less than 1.0 ppm, preferably less than 0.7 ppm, and the generation of two impurities, acetaldehyde and methyl formate, can be suppressed even if the temperature of the cooler is maintained at a somewhat high level.

[0102] In the case of Examples 7 and 8, it can be seen that when 10 ppm of 4-tert-Butylcatechol (hereinafter TBC) is added instead of the antioxidant BHT, even when the temperature of the cooler rises to 30~40℃ and the dissolved oxygen is 0.5~0.7 ppm, acetaldehyde and methyl formate are not produced.

[0103] On the other hand, in the case of Comparative Examples 8 and 9, when the dissolved oxygen is 1 ppm or higher, it can be seen that the formation of impurities such as acetaldehyde and methyl formate is not suppressed even when TBC is added.

[0104] Example 9 is a case where SONGNOX 1010 (tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane) 10 ppm was added instead of the antioxidant BHT, and it can be seen that the formation of acetaldehyde and methyl formate is suppressed even when using such an antioxidant.

[0105] Therefore, it can be confirmed that when an antioxidant is added and a distillation process is carried out, even if the cooler temperature of propylene glycol monomethyl ether acetate becomes 30 to 40°C, the formation of impurities can be suppressed to a degree that meets semiconductor-grade requirements when the dissolved oxygen is less than 1.0 ppm, preferably 0.7 ppm or less.

[0106] The foregoing description is merely illustrative of the present invention, and those skilled in the art will be able to make various modifications without departing from the essential characteristics of the present invention. Accordingly, the embodiments disclosed herein are intended to illustrate, not limit, the present invention, and the scope of the rights of the present invention is not limited by such embodiments. The scope of protection of the present invention should be interpreted by the claims, and all technology within an equivalent scope should be interpreted as being included within the scope of the rights of the present invention.

Claims

Claim 1 A method for producing high-purity propylene glycol monomethyl ether acetate for semiconductors, comprising: a step of distilling and purifying raw material propylene glycol monomethyl ether acetate; and a step of cooling the distilled and purified propylene glycol monomethyl ether acetate by passing it through a cooler, wherein in the distillation and purification step and the cooling step, the dissolved oxygen content in the propylene glycol monomethyl ether acetate is maintained at 0.7 ppm or less, and the temperature of the cooler is maintained at 20 to 30 ℃. Claim 2 A method for producing high-purity propylene glycol monomethyl ether acetate for semiconductors, comprising: a step of distilling and purifying raw material propylene glycol monomethyl ether acetate; and a step of cooling the distilled and purified propylene glycol monomethyl ether acetate by passing it through a cooler, wherein in the distillation and purification step and the cooling step, the dissolved oxygen content in the propylene glycol monomethyl ether acetate is maintained at 0.3 ppm or less, and the temperature of the cooler is maintained at 30 to 40 ℃. Claim 3 A method for producing high-purity propylene glycol monomethyl ether acetate for semiconductors, comprising: a step of distilling and purifying raw material propylene glycol monomethyl ether acetate; a step of cooling the distilled and purified propylene glycol monomethyl ether acetate by passing it through a cooler; and a step of storing the propylene glycol monomethyl ether acetate that has passed through the cooler in a storage container, wherein in the distillation and purification step and the cooling step, the dissolved oxygen content in the propylene glycol monomethyl ether acetate is maintained at 0.7 ppm or less, the temperature of the cooler is maintained at 30 to 40 ℃, and an antioxidant is introduced into the storage container at 10 ppm or less. Claim 4 delete Claim 5 delete Claim 6 delete Claim 7 According to claim 3, The antioxidant is 2,6-di-tert-butyl-4-methylphenol (BHT), 4-tert-butyl catechol (TBC), p-methoxyphenol (MEHQ), 4-tert-butylphenol (TBP), HQ (Hydroquinone), tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] methane, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-, C7-9-branched alkyl esters, triethylene glycol-bis-3-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate, thiodiethylene A method for producing high-purity propylene glycol monomethyl ether acetate for semiconductors, characterized by being selected from the group consisting of bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. Claim 8 delete Claim 9 A method for producing high-purity propylene glycol monomethyl ether acetate for semiconductors, characterized in that, in one of claims 1 to 3, the high-purity propylene glycol monomethyl ether acetate does not contain acetaldehyde and methyl formate and is used in a photoresist process using an EUV or ArF light source.

Images