Method for purifying high purity isopropyl alcohol for semiconductor cleaning processes

Abstract

The present invention relates to a purification process of high purity isopropyl alcohol for semiconductor cleaning processes, comprising the step of removing diacetone alcohol, boric acid triisopropyl ester and metal impurities by means of a distillation process after removing diacetone alcohol in isopropyl alcohol by an adsorption process.

Description

TECHNICAL FIELD

[0001] The present invention relates to a purification method of isopropyl alcohol, and more particularly, to a purification method of high-purity isopropyl alcohol for a semiconductor cleaning process. BACKGROUND

[0002] Isopropyl alcohol (hereinafter, referred to as "IPA") is used for various purposes including a cleaning agent in the electronic industry such as semiconductor or LCD (Liquid Crystal Display) manufacturing.

[0003] In a semiconductor cleaning process, after patterning a wafer, water has been used for cleaning, but there was a problem of pattern collapse in cleaning with water. Therefore, in order to solve such a problem, IPA having low surface tension and excellent solubility and volatility compared to water is used.

[0004] For IPA used in a semiconductor cleaning process, the specification for moisture and impurities is very strict.

[0005] IPA used in a semiconductor cleaning process needs to maintain a purity of 99.999% or more (5N), moisture of 10 ppm or less, metal impurities of 20 ppt or less, triisopropyl borate (hereinafter, referred to as boron compound) of 50 ppt or less, and needs to completely remove diacetone alcohol.

[0006] The content of moisture and impurities in industrial IPA as a raw material exceeds the specification required in a semiconductor cleaning process, and thus in order to maintain a purity of 99.999% (5N) or more, a purification process is required.

[0007] PRIOR ART DOCUMENT

[0008] PATENT DOCUMENT

[0009] (Patent Document 1) Korean Patent No. 10-1662895 (published on March 2, 2015)

[0010] (Patent Document 2) Korean Patent No. 10-1582001 (published on January 9, 2014)

[0011] (Patent Document 3) Korean Patent No. 10-1206214 (published on July 26, 2010) SUMMARY

[0012] PROBLEMS TO BE SOLVED BY THE INVENTION

[0013] The present invention aims to provide a purification method of isopropyl alcohol of high purity, which introduces an adsorption process and a distillation process to purify industrial isopropyl alcohol, thereby completely removing diacetone alcohol, and the moisture, triisopropyl borate and metal content meet the semiconductor grade specifications.

[0014] Technical Solution

[0015] To solve the above problems, the present invention provides a purification method of isopropyl alcohol, which purifies industrial isopropyl alcohol (hereinafter also referred to as IPA) as a raw material using an adsorption process and a distillation process. According to an embodiment of the present invention, the present invention includes: a step of removing diacetone alcohol (hereinafter also referred to as DAA) in isopropyl alcohol by an adsorption process, and then removing diacetone alcohol, triisopropyl borate (hereinafter also referred to as borate compound) and metal impurities from the lower stream by a distillation process.

[0016] The adsorption process includes a passing step of passing the isopropyl alcohol through a 10X or 13X molecular sieve after passing through a 3A or 4A molecular sieve, and the distillation process includes a primary distillation process for removing impurities having a lower boiling point than isopropyl alcohol, and a secondary distillation process for distilling the lower stream of the primary distillation process, removing DAA, borate compound and metal impurities having a higher boiling point than isopropyl alcohol from the lower stream, and obtaining purified isopropyl alcohol from the upper stream.

[0017] Preferably, the molecular sieve is sufficiently washed with IPA containing 10 ppm or less of moisture before use, and preferably, nitrogen gas is purged in order to inhibit the inflow of oxygen during the distillation process.

[0018] Preferably, the temperature is maintained at 82°C or less when the primary and secondary distillation processes are performed, and the reflux ratio is maintained at 1.5 or more when the secondary distillation process is performed.

[0019] Effects of the Invention

[0020] According to the present invention, semiconductor-grade isopropyl alcohol of high purity can be produced, which has a moisture content, metal content and borate compound content that meet the specifications required in a semiconductor cleaning process, and does not contain diacetone alcohol.

[0021] Therefore, since metal elution can be prevented in a post-production storage tank, a mobile tank truck moving to a customer, a storage tank and a pipeline for use by a customer, high-purity isopropyl alcohol can be supplied to a semiconductor cleaning line, thereby reducing the rejection rate of a semiconductor process and improving the productivity of semiconductors. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 FIG. 1 is a diagram for explaining a purification process of isopropyl alcohol according to an embodiment of the present invention.

[0023] Figure 2 A gas chromatogram of components of isopropyl alcohol purified according to an embodiment of the present application. DETAILED DESCRIPTION

[0024] Unless specifically defined otherwise, all terms used in the present specification are intended to have the same meaning as those commonly understood by one of ordinary skill in the art to which the present application pertains, and, unless otherwise defined, the terms are not to be interpreted as having the same meaning as those used in any other document in the art. Throughout the entire specification, unless explicitly described otherwise, when a part "comprises" a certain constituent element, it means that it can further include other constituent elements, rather than excluding other constituent elements.

[0025] The term "semiconductor grade" used in the present specification means a degree of purity or characteristics maintained to a degree required in a semiconductor cleaning process, "removal" means a reduction in the content of a specific substance, and "complete removal" means a state in which a specific substance does not exist.

[0026] Also, the term "high purity" used in the present application means a purity of 99.999%, i.e., 5N or more.

[0027] For the sake of explanation of constituent elements of the present application, the terms of first, second, A, B, (a), (b), etc. can be used. Such terms are used only to distinguish the constituent elements thereof from other constituent elements, and the nature or order or sequence, etc. of the constituent elements are not limited to the terms.

[0028] For the sake of explanation of the present application, if it is judged that a detailed explanation of a related well-known constituent or function will obscure the gist of the present application, a detailed explanation thereof will be omitted.

[0029] Hereinafter, an embodiment of the present application will be described in detail with reference to the accompanying drawings.

[0030] Figure 1 A diagram for explaining a purification method of high-purity isopropyl alcohol usable in a semiconductor cleaning process according to an embodiment of the present application.

[0031] REFERENCE Figure 1The purification method of isopropyl alcohol according to an embodiment of the present application includes a washing step S110 of washing a molecular sieve for an adsorption process with IPA, a first adsorption step S120 of passing industrial IPA as a raw material through the washed 3A or 4A molecular sieve to remove moisture and diacetone alcohol, a second adsorption step S130 of passing the IPA through a 10X or 13X molecular sieve to completely remove diacetone alcohol, a first distillation process step S140 of performing distillation to remove impurities having a lower boiling point than IPA and obtaining a lower stream, and a second distillation process step S150 of performing distillation to remove impurities having a higher boiling point than IPA to the lower part and obtaining purified IPA in the upper part, using the lower stream.

[0032] First, the washing step S110 will be described.

[0033] According to the present application, if the content of moisture in IPA as a raw material is reduced to a semiconductor grade level and DAA (diacetone alcohol) can be completely removed through an adsorption process, the scope of the present application is not limited to a specific means, but the adsorption process of an embodiment of the present application uses a molecular sieve.

[0034] A molecular sieve can remain basic substances due to manufacturing characteristics. Such remaining basic substances can convert acetone, which is formed by oxidation of IPA in a subsequent purification process, into DAA by means of a hydroxy aldehyde reaction. Therefore, in order to minimize the generation of DAA during the purification process, it is preferable to remove the basic substances remaining in the molecular sieve, and thus it is preferable to sufficiently wash the molecular sieve before use.

[0035] It is preferable that IPA used at the time of washing contains moisture of 10 ppm or less, and in order to maintain the pH of the molecular sieve to 6.5 to 7.5, it is preferable to sufficiently perform washing.

[0036] Industrial IPA as a raw material is passed through the washed molecular sieve to remove moisture and DAA (S120). In general, industrial IPA as a raw material contains tens to hundreds of ppm of moisture, and contains tens of ppt of DAA.

[0037] Therefore, by means of the first adsorption process of passing IPA as a raw material through a 3A or 4A molecular sieve, the moisture can be reduced to 10 ppm or less.

[0038] By means of the first adsorption process, although the moisture can be reduced to a semiconductor grade, DAA cannot be completely removed. Therefore, in order to completely remove DAA, it is necessary to continuously pass IPA through a 10X or 13X molecular sieve after the first adsorption process.

[0039] IPA for semiconductor process is very strict on the specification of metal (M) as an impurity, and all items are controlled in ppt units. The acceptable metal content of IPA for semiconductor cleaning process requires 50 ppt or less, preferably 20 ppt or less, for each metal.

[0040] Generally, metals can be removed in the lower stream of the distillation process because of their very high boiling points, but even if only a small amount of DAA remains, it can cause problems of metal elution in the distillation column, pipes, storage tanks, etc. made of stainless steel. Since DAA forms a chelate with metals, especially Fe, it has a problem of accelerating the elution of metals.

[0041] Therefore, in order to complete the removal of DAA in IPA as a raw material, in an embodiment of the present application, 2 adsorption processes are performed, which pass IPA, which has been significantly reduced in moisture by means of 1 adsorption process, through 10X or 13X molecular sieves (S130).

[0042] Passing IPA through 10X or 13X molecular sieves adsorbs and removes DAA in two mechanisms. The first is to form a salt with Na+ or K+ attached to the surface of the molecular sieve and be removed, and the second is to insert / adsorb the voids of the molecular sieve with DAA molecules that are slightly smaller than the voids of the molecular sieve and be removed.

[0043] As described above, IPA that has passed through 1 and 2 adsorption processes contains moisture at a level acceptable in semiconductor cleaning processes, and DAA is completely removed so that it does not exist.

[0044] As described in the foregoing, if metal flows in the semiconductor manufacturing process, it needs to be purified because it can be a cause of disqualification, and 20 or more metals contained in IPA need to be controlled to 50 ppt or less for each metal.

[0045] The metals managed for IPA for semiconductors include Ag, Al, As, Au, B, Ba, Ca, Cd, Cr, Cs, Cu, Ga, Ge, Hf, In, K, La, Li, Mg, Mn, Mo, Na, Nb, Ni, Pb, Sb, Sn, Sr, Ta, Ti, V, W, Y, Zn, Zr, etc. in addition to Fe, and these should be included in IPA at 20 ppt or less, and Fe ion is one of the metals that needs to be very carefully managed.

[0046] Generally, since the boiling point of metals is higher than that of IPA, it is easy to remove with ordinary distillation. Therefore, by means of a distillation process, the metal as an impurity can be reduced to the level of a semiconductor grade.

[0047] In addition, a binder of a molecular sieve used to reduce the content of moisture and completely remove DAA contains triisopropyl borate (hereinafter, referred to as a boron compound), and the boron compound can be eluted from a glass material in a purification process. This boron compound also affects the intrinsic properties of a semiconductor, and thus is one of items managed in ppt units. The boron compound contained in IPA used in a semiconductor cleaning process is required to be 50 ppt or less.

[0048] The boiling point of the boron compound is about 140°C, and thus can be removed by means of a distillation process, but a portion forms an azeotropic distillation with isopropyl alcohol, and thus it is difficult to perfectly remove. Therefore, it is preferable to perform a distillation process to remove the metal and the boron compound, and to perform a 2-time distillation process to reduce the content of the boron compound.

[0049] The distillation process step can include a 1-time distillation process step S140 and a 2-time distillation process step S150.

[0050] Since this distillation process is performed at a high temperature, IPA supplied to a distillation column is exposed to oxygen and heat, and as shown in the following Reaction Formula 1, acetone is generated, and thus there is a problem in that acetone can be converted into DAA under an acid or basic catalyst.

[0051] <Reaction Formula 1>

[0052]

[0053] Therefore, in order to prevent IPA from being oxidized in a purification process, nitrogen is sufficiently supplied to the inside of a column and an auxiliary operating device and a distillation process is performed. That is, it is preferable to sufficiently purge nitrogen to maximize the prevention of oxygen inflow during a distillation process.

[0054] A 1-time distillation process is a process to remove impurities having a lower boiling point than IPA, and a 2-time distillation process is a process to remove impurities having a higher boiling point than IPA.

[0055] Even if nitrogen is purged and a distillation process is performed, DAA can be additionally generated during the distillation process. Even if the amount of DAA is small, it can be problematic if it remains, and thus it is necessary to appropriately adjust the temperature of a distillation column to completely remove DAA.

[0056] The distillation temperature and the number of refluxes in the distillation process step affect the residual amount of DAA. In a 1-time distillation process, if the internal temperature of a distillation column is maintained at 82°C or less, and preferably, is maintained at 78 to 82°C, DAA is not generated, and in a 2-time distillation process, if the internal temperature of a distillation column is maintained at 82°C or less, and preferably, is maintained at 78 to 82°C, and the number of refluxes in a 2-time distillation column is maintained at 1.5 or more, and preferably, is maintained at 1.5 to 2 or more, IPA in which DAA is completely removed can be obtained.

[0057] If the temperature of the 1st distillation column exceeds 82°C, a trace amount of DAA is generated, and the trace amount of generated DAA has a boiling point of 166°C, which is higher than that of IPA, and thus can be removed with the lower stream of the 2nd distillation column, but since most of the operation is concentrated, DAA is concentrated in the lower portion and can rise to the upper stream.

[0058] Therefore, preferably, the temperature of the 1st distillation column is maintained at 82°C or less, so that the DAA contained in the IPA supplied to the 2nd distillation column is 0.5 ppt or less.

[0059] A trace amount of DAA, boron compounds, and metal compounds are contained in the IPA supplied to the 2nd distillation column. Therefore, in order to completely remove the DAA and reduce the boron compounds to 50 ppt or less, the internal temperature of the distillation column is maintained at 82°C or less, preferably, 78 to 82°C, and the reflux ratio is maintained at 1.5 or more, preferably, 1.5 to 2 or more.

[0060] By means of the 2nd distillation process, impurities such as DAA, boron compounds, and metal compounds can be removed with the lower stream, DAA can be completely removed, and high-purity IPA can be obtained with the upper stream.

[0061] Therefore, by the adsorption and distillation processes, 10 ppm or less of moisture, 50 ppt or less of triisopropyl borate, and 20 ppt or less of each metal are contained, and semiconductor-grade purified IPA having a purity of 99.999 wt% or more without containing diacetone alcohol can be obtained.

[0062] Hereinafter, specific examples of the present application will be described. The following examples are merely illustrative of the present application and the scope of the present application is not limited to these examples.

[0063] <Example 1>

[0064] The 3A and 13X molecular sieves were washed with IPA having 10 ppm or less of moisture at a molecular sieve volume ratio of 50 times. Industrial IPA containing 120 ppm of moisture, 18 ppt of diacetone alcohol, and 100 ppt of boron compounds was continuously passed through the washed 3A and 13X molecular sieves.

[0065] Thereafter, while maintaining the reboiler temperature of the 1st distillation column at 78°C, 5 wt% was removed with the upper stream with respect to the input amount, and the lower stream was supplied to the 2nd distillation column.

[0066] While maintaining the reboiler of the 2nd distillation column at 78°C, the reflux ratio was maintained at 1.5 to 2, high-boiling substances such as diacetone alcohol, boron compounds, and metals were removed with the lower stream, and high-purity semiconductor-grade IPA was obtained with the upper stream.

[0067] <Example 2>

[0068] The reboiler temperature of the 1st distillation column and the 2nd distillation column was maintained at 80°C, respectively, except for this, purification was performed in the same manner as in Example 1.

[0069] <Example 3>

[0070] The reboiler temperature of the 1st distillation column and the 2nd distillation column was maintained at 82°C, respectively, except for this, purification was performed in the same manner as in Example 1.

[0071] <Comparative Example 1> to <Comparative Example 6>

[0072] The reboiler temperature of the 1st distillation column and the 2nd distillation column and the reflux ratio were maintained under the conditions shown in Table 1 below, except for this, purification was performed in the same manner as in Example 1.

[0073] <Comparative Example 7>

[0074] The IPA used as a raw material was not washed and used as it was, except for this, purification was performed in the same manner as in Example 1.

[0075] <Comparative Example 8> and <Comparative Example 9>

[0076] The temperature of the 1st distillation process was maintained as shown in Table 1 below, except for this, purification was performed in the same manner as in Example 7.

[0077] <Comparative Example 10>

[0078] After passing the IPA used as a raw material through only a 3A molecular sieve, it was fed to the distillation process, except for this, purification was performed in the same manner as in Example 3.

[0079] <Comparative Example 11>

[0080] The reflux ratio was maintained at 2.5 to 3, except for this, purification was performed in the same manner as in Example 10.

[0081] The results of measuring the content of moisture, diacetone alcohol (DAA), and boron compounds contained in IPA after the raw material used in the purification processes of Examples 1 to 3 and Comparative Examples 1 to 11 and each process step were as shown in Table 1 below. In Table 1 below, the unit of the moisture content is ppm, and the units of the contents of DAA and boron compounds are ppt.

[0082] [Table 1]

[0083]

[0084] M / S: molecular sieve

[0085] N / D: not detected

[0086] As can be seen from the table 1, according to the embodiment 1 to embodiment 3 of the present application, high purity IPA containing 10 ppm or less of moisture, 50 ppm or less of boron compound, and completely removing diacetone alcohol can be obtained.

[0087] As in the embodiment 1 to embodiment 3, comparative example 1 to comparative example 9, if the molecular sieves of 3A and 13X are used continuously, the moisture can be reduced to 10 ppm or less, and DAA can be completely removed, but according to comparative example 10 and comparative example 11, it can be confirmed that DAA is not completely removed in the adsorption process.

[0088] In the case of the embodiment 3, since 0.5 ppt of diacetone alcohol is contained in the lower stream of the 1st distillation column, it can be confirmed that DAA can be additionally generated in the distillation process. However, the additionally generated DAA is removed with the lower stream in the 2nd distillation process, and thus DAA is not observed in the upper stream of the 2nd distillation column.

[0089] From the observation of the embodiment 1 to embodiment 3 and comparative example 1 and comparative example 2, it can be confirmed that the amount of DAA contained in the lower stream varies depending on the temperature of the 1st distillation column. In particular, from the comparison of the embodiment 3 and comparative example 1 and comparative example 2, when DAA contained in the lower stream of the 1st distillation column is 0.5 ppt or less, DAA can be completely removed by means of the 2nd distillation process (embodiment 3), but when it is a lower stream containing 0.9 ppt or more of DAA, DAA cannot be completely removed even if the 2nd distillation is performed. Thus, it can be known that in order to contain 0.5 ppt or less of DAA in the 1st distillation process step, it is very important to set the temperature conditions of the 1st distillation column.

[0090] Also, in the case of the comparative example 3, since 0.5 ppt of DAA is contained in the lower stream of the 1st distillation column, and 0.01 ppt of DAA still exists in the upper stream of the 2nd distillation column, it can be known that the reflux ratio in the 2nd distillation column affects the residual amount of DAA. That is, it can be known that when the reflux ratio of the 2nd distillation column is 1, DAA cannot be completely removed. Also, it can be confirmed that the amount of boron compound at this time is 51 ppt, which exceeds the acceptable value of 50 ppt required in the semiconductor grade.

[0091] The comparative example 4 to comparative example 6 are cases where the temperature of the 1st and 2nd distillation columns is 82°C or more, and the reflux ratio of the 2nd distillation column is 1 or less, and it can be confirmed that DAA is contained in the upper stream of the 2nd distillation column, and boron compound of 50 ppt or more is also contained.

[0092] As for Comparative Example 7 and Comparative Example 8, the molecular sieve used in the adsorption process was not washed, and except for this, purification was performed under the same conditions as in Example 1 and Example 3, respectively, but the lower stream of the 1st distillation column contained 1.2 ppt and 6.9 ppt of diacetone alcohol, respectively, and after the 2nd distillation process, the upper stream still contained 0.4 ppt and 1.8 ppt of diacetone alcohol, respectively. Therefore, in order to completely remove DAA, it is necessary to use the molecular sieve used in the adsorption process after washing with IPA.

[0093] Comparative Example 9 used a molecular sieve that was not washed, and the temperature of the distillation process was 85°C, and therefore DAA remained in the upper stream of the 2nd distillation column.

[0094] As for Comparative Example 10, after passing the IPA used as a raw material through a 3A molecular sieve, it was introduced into the distillation process, and except for this, purification was performed in the same manner as in Example 3, but 2.1 ppt of DAA remained in the upper stream of the distillation process, and it was found that even if the reflux ratio was increased as in Comparative Example 11, if DAA was not completely removed in the adsorption process, DAA can remain in the upper stream of the 2nd distillation column. Therefore, it is necessary to completely remove DAA in the adsorption process step and then introduce it into the distillation process.

[0095] The results of analyzing (ICP-MS analysis) the content of metals contained in the purified IPAs obtained according to the Examples 1 to 3, Comparative Examples 1 to 6, Comparative Example 10, and Comparative Example 11 are shown in Table 2 and Table 3 below. In Table 2 and Table 3 below, the content of each metal is in ppt.

[0096] [Table 2]

[0097] Metal Ag A1 As Au B Ba Ca Cd Co Cr Cs Cu Fe Ga Ge Hf In K Example 1 0 2 1 0 11 0 0 0 0 0 0 0 1 0 0 0 0 1 Example 2 0 1 0 0 9 0 0 0 0 0 0 0 2 0 0 0 0 2 Example 3 0 1 2 0 13 0 0 0 0 0 0 0 1 0 0 0 0 2 Comparative Example 1 0 0 1 0 14 0 0 0 0 0 0 0 1 0 0 0 0 3 Comparative Example 2 0 0 1 0 8 0 0 0 0 0 0 0 2 0 0 0 0 1 Comparative Example 3 0 1 2 0 7 0 0 0 0 0 0 0 0 0 0 0 0 2 Comparative Example 4 0 1 2 0 6 0 0 0 0 0 0 0 0 0 0 0 0 2 Comparative Example 5 0 2 2 0 12 0 0 0 0 0 0 0 1 0 0 0 0 1 Comparative Example 6 0 1 0 0 11 0 0 0 0 0 0 0 1 0 0 0 0 2 Comparative Example 10 0 0 0 0 10 0 0 0 0 0 0 0 1 0 0 0 0 2 Comparative Example 11 0 2 0 0 9 0 0 0 0 0 0 0 1 0 0 0 0 4

[0098] [Table 3]

[0099] Metal La Li Mg Mn Mo Na Nb Ni Pb Sb Sn Sr Ta Ti V W Y Zn Zr Example 1 0 0 0 1 1 2 0 2 0 0 0 0 0 1 1 0 0 2 0 Example 2 0 0 0 0 0 3 0 2 0 0 0 0 0 0 1 0 0 3 0 Example 3 0 0 0 0 0 2 0 2 0 0 0 0 0 1 3 0 0 3 1 Comparative Example 1 0 0 0 1 0 4 0 3 0 0 0 0 0 2 2 0 0 2 0 Comparative Example 2 0 0 0 1 2 2 0 1 0 0 0 0 0 1 4 0 0 4 0 Comparative Example 3 0 0 0 1 1 1 0 2 0 0 0 0 0 1 3 0 0 5 0 Comparative Example 4 0 0 0 1 1 1 0 2 0 0 0 0 0 1 2 0 0 1 0 Comparative Example 5 0 0 0 2 2 3 0 1 0 0 0 0 0 2 1 0 0 3 0 Comparative Example 6 0 0 0 2 2 2 0 1 0 0 0 0 0 3 1 0 0 3 0 Comparative Example 10 0 0 0 3 1 4 0 3 0 0 0 0 0 1 1 0 0 4 0 Comparative Example 11 0 0 0 2 1 1 0 4 0 0 0 0 0 1 1 0 0 2 0

[0100] As can be confirmed from Table 2 and Table 3, not only the purified IPAs obtained according to the Examples 1 to 3 of the present application, but also the purified IPAs obtained according to Comparative Examples 1 to 6, Comparative Example 10, and Comparative Example 11, contained each metal in an amount of 20 ppm or less.

[0101] Therefore, the content of metals contained in the IPA purified according to the Examples of the present application meets the semiconductor specifications.

[0102] Furthermore, the results of analyzing the components of the high-purity purified IPA obtained from the upper stream of the 2nd distillation column according to Example 1 of the present application are shown in Table 4 below. Figure 2 [Table 4]

[0103] Figure 2 For analyzing the gas chromatogram of the components of isopropyl alcohol purified according to the embodiment 1 of the present application, the component analysis results are shown in Table 4 below.

[0104] [Table 4]

[0105]

[0106] As shown by Table 4 and Figure 2 It can be seen that according to the purification method of the present application, IPA having a purity of 99.999% or more (5N or more) can be obtained. That is, according to the purification method of the present application, high-purity IPA having a purity of 5N or more, which contains no DAA and has moisture, boron compound and metal contents satisfying the required levels in semiconductor grade, can be obtained.

[0107] The above description is merely illustrative of the present application and various modifications can be made by those skilled in the art without departing from the nature of the present application. Therefore, the embodiments disclosed in the present specification are not intended to limit the present application, but to explain the present application, and the scope of protection of the present application is not limited to these embodiments. The scope of protection of the present application should be interpreted according to the claims of the present application, and all technologies within the equivalent scope thereof should be interpreted as being included in the scope of protection of the present application.

Claims

1. A method for purifying isopropyl alcohol, characterized by, completely removing diacetone alcohol from isopropyl alcohol by an adsorption process, and then completely removing the generated diacetone alcohol and reducing the content of triisopropyl borate and metal impurities to a level required in a semiconductor cleaning process by means of a distillation process; the adsorption process includes a passing step which makes the isopropyl alcohol pass through a 10X or 13X molecular sieve in succession after passing through a 3A or 4A molecular sieve; the distillation process includes a 1st distillation process which removes impurities having a lower boiling point than isopropyl alcohol, and a 2nd distillation process which distills a lower stream of the 1st distillation process to remove the diacetone alcohol, triisopropyl borate compound and metal impurities having a higher boiling point than isopropyl alcohol, and obtain purified isopropyl alcohol in an upper stream; during the 1st and 2nd distillation processes, the distillation temperature is maintained at 82°C or lower, and when the 2nd distillation process is performed, the reflux ratio is maintained at 1.5 or more; the method further includes a washing step which washes the molecular sieve with isopropyl alcohol having a moisture content of 10 ppm or less in order to maintain the molecular sieve at pH 6.5 to 7.5 before the adsorption process.

2. The method for purifying isopropyl alcohol according to claim 1, characterized by, reducing the moisture content of isopropyl alcohol to 10 ppm or less by the adsorption process.

3. The method for purifying isopropyl alcohol according to claim 1, characterized by, purging nitrogen gas in order to suppress the inflow of oxygen during the distillation process.

4. The method for purifying isopropyl alcohol according to claim 1, characterized by, the purity of isopropyl alcohol purified by means of the distillation process is 99.999 wt% or more, the moisture content is 10 ppm or less, triisopropyl borate is 50 ppt or less, and each metal is 20 ppt or less.

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