Preparation method and application of electronic-grade n-hexane for semiconductor cleaning

Abstract

The invention relates to the technical field of n-hexane preparation, in particular to a preparation method and application of electronic-grade n-hexane for semiconductor cleaning, and the method comprises the following steps: raw material pretreatment: taking industrial-grade n-hexane, adding a sodium hydroxide solution for neutralization, standing for layering, taking an oil phase, washing with deionized water, adding a drying agent for drying, and taking out the oil phase; and standing and filtering to obtain the pretreated n-hexane. According to the method, a core process system of raw material pretreatment, normal pressure rectification, composite adsorption and ultra-clean filtration is constructed, and improved schemes such as reduced pressure rectification, oxidation-adsorption combined treatment and the like can be further combined, so that various impurities such as moisture, aromatic hydrocarbon, metal ions, unsaturated hydrocarbon and the like in the n-hexane are synergistically and deeply removed.

Description

Technical Field

[0001] This invention relates to the field of n-hexane preparation technology, specifically to a method for preparing electronic-grade n-hexane for semiconductor cleaning and its application. Background Technology

[0002] Electronic-grade n-hexane is a key cleaning agent in the semiconductor manufacturing field. Its purity and impurity content directly determine the cleaning effect of semiconductor wafers, which in turn affects the performance stability and production yield of subsequent semiconductor devices. Especially in the development of advanced semiconductor processes, more stringent requirements have been placed on the purity control, impurity types and content limits of electronic-grade n-hexane.

[0003] However, existing electronic-grade n-hexane preparation technologies and products have many technical limitations. Traditional preparation processes often rely on a single adsorbent for impurity treatment, making it difficult to achieve the synergistic and efficient removal of multiple impurities such as moisture, aromatics, and metal ions. This results in high impurity residues in the product, failing to meet the low-impurity environment requirements of high-precision semiconductor cleaning. Furthermore, unreasonable design of conventional distillation process parameters can easily lead to excessive energy consumption or n-hexane thermal cracking, increasing production costs and potentially introducing new impurities and reducing product purity. Existing processes for removing unsaturated hydrocarbons, such as Pd / C catalytic hydrogenation, not only require expensive precious metal catalysts but may also generate n-hexane isomers, further affecting product quality and increasing the difficulty of subsequent purification. Fourthly, commercially available electronic-grade n-hexane generally has high metal ion, moisture, and aromatic content, making it suitable only for lower-precision semiconductor processes and unable to meet the stringent standards for cleaning reagents in advanced processes. In addition, some preparation processes have poor adaptability to different raw material amounts, easily leading to product performance fluctuations due to changes in raw material quantities, which is detrimental to large-scale industrial applications. The shortcomings of these existing technologies severely restrict the application of electronic-grade n-hexane in advanced semiconductor manufacturing, and there is an urgent need to propose new preparation methods to solve the above problems. Summary of the Invention

[0004] The primary objective of this invention is to provide a method for preparing electronic-grade n-hexane for semiconductor cleaning and its application.

[0005] A further object of the present invention is to provide a method for preparing electronic-grade n-hexane for semiconductor cleaning, the method comprising the following steps: (1) Raw material pretreatment: Take industrial grade n-hexane, add sodium hydroxide solution to neutralize, let stand and separate into layers, take the oil phase, wash with deionized water, add desiccant to dry, let stand and filter to obtain pretreated n-hexane; (2) Atmospheric pressure distillation: Pretreated n-hexane is fed into a distillation column, the top temperature and reflux ratio are controlled, the top fraction is collected, and crude n-hexane is obtained; (3) Composite adsorption: crude n-hexane is passed through an adsorption column filled with adsorbent at a set flow rate and the adsorption temperature is controlled to obtain adsorbed n-hexane; the adsorbent contains at least molecular sieve and activated alumina; (4) Ultra-clean filtration: The adsorbed n-hexane is filtered through a filter element to obtain electronic-grade n-hexane; the filter element material is polytetrafluoroethylene or polypropylene.

[0006] Preferably, in step (1), the volume fraction of the sodium hydroxide solution is 8%-12%, the amount used is 3%-8% of the raw material volume, and the pH of the neutralized aqueous phase is 6.8-7.2; the resistivity of the deionized water is... The washing process involves 2-4 water washes, with each wash using 8%-15% of the raw material volume. The desiccant is anhydrous magnesium sulfate or anhydrous sodium sulfate, used at 0.3%-0.8% of the raw material mass. After drying, the moisture content of the pretreated n-hexane is ≤60ppm.

[0007] Preferably, in step (2), the distillation column is a packed distillation column or a plate distillation column with 25-35 plates; the top temperature is 66-70℃ and the reflux ratio is 2:1-4:1.

[0008] Preferably, in step (3), the mass ratio of molecular sieve to activated alumina is 1:1-1:2; the molecular sieve is a 3A, 4A, or 5A molecular sieve; and the specific surface area of ​​the activated alumina is ≥280 m². 2 / g; the adsorption column height is 40-60cm, the flow rate is 0.8-1.2mL / min, and the adsorption temperature is 35-45℃.

[0009] Preferably, in step (3), the adsorbent further includes a metal chelating resin, and the mass ratio of molecular sieve, activated alumina and metal chelating resin is 1:1:1-3:3:1; the metal chelating resin is aminophosphonic acid type, carboxylic acid type or imine diacetic acid type; the adsorption temperature is adjusted to 45-55℃ and the flow rate is adjusted to 0.6-1.0mL / min.

[0010] Preferably, step (2) after atmospheric distillation further includes a vacuum distillation step: crude n-hexane is fed into a vacuum distillation column, the vacuum degree, the top temperature and the reflux ratio are controlled, and the top fraction is collected; the vacuum distillation column is a plate column or a packed column, with 35-45 plates; the vacuum degree is 0.092-0.098 MPa, the top temperature is 42-48℃, and the reflux ratio is 4:1-6:1.

[0011] Preferably, the process after vacuum distillation also includes an oxidation-adsorption combined treatment step: the fraction obtained from vacuum distillation is subjected to ultraviolet oxidation treatment, and the oxidized material is directly introduced into the composite adsorption column in step (3); the wavelength of the ultraviolet oxidation is 240-250nm, the power is 80-120W, the oxygen volume ratio is 0.3%-0.7%, the reaction temperature is 32-38℃, and the reaction time is 25-35min.

[0012] Preferably, ultraviolet oxidation is replaced by ultraviolet-assisted hydrogen peroxide oxidation; the mass ratio of hydrogen peroxide to material is 0.2%-0.5%.

[0013] Preferably, ultraviolet oxidation is replaced by plasma oxidation; the plasma oxidation equipment has a power of 50-80W, an oxygen volume ratio of 0.3%-0.7%, a reaction temperature of 32-38℃, and a reaction time of 30-35min.

[0014] The present invention also provides an application of electronic-grade n-hexane prepared by the above method in semiconductor cleaning.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention constructs a core process system of raw material pretreatment, atmospheric distillation, composite adsorption, and ultra-clean filtration. It can be further combined with improved schemes such as vacuum distillation and oxidation-adsorption co-treatment to achieve synergistic and deep removal of various impurities, including moisture, aromatics, metal ions, and unsaturated hydrocarbons, from n-hexane. Specifically, the composite adsorption step innovatively employs a combination of molecular sieves, modified adsorbents, and chelating resins. Utilizing the synergistic effect of each adsorbent material, it effectively overcomes the limitations of traditional single adsorbents in impurity removal, significantly reducing the content of metal ions, aromatics, and moisture in the product. The oxidation-adsorption co-treatment, through ultraviolet or plasma oxidation technology, can deeply remove unsaturated hydrocarbons while avoiding the formation of n-hexane isomers, further improving product purity and meeting the stringent requirements of advanced semiconductor processes for high-purity cleaning reagents.

[0016] 2. This invention, through precise optimization of key parameters in each process step, allows the preparation process to flexibly adapt to different scales of raw material quantities. When the raw material quantity changes, only the relevant process parameters need to be adjusted synchronously to stably control the impurity removal efficiency, avoiding product performance fluctuations caused by changes in raw material quantity. Furthermore, the electronic-grade n-hexane prepared by this invention maintains its purity and key impurity content within the range required for advanced processes even after long-term storage, demonstrating excellent process stability and product storage stability, providing a reliable guarantee for large-scale industrial application.

[0017] 3. This invention optimizes the vacuum distillation parameters in the distillation step. By controlling the appropriate vacuum level, column top temperature and reflux ratio, it cleverly balances the low boiling point requirement of n-hexane with the low cracking risk. This avoids the problem of excessive energy consumption under conventional low vacuum conditions and reduces the risk of easy cracking of n-hexane at high temperatures, effectively reducing process energy consumption. At the same time, it reduces the possibility of introducing new impurities due to cracking, significantly improving process safety and economy.

[0018] 4. The electronic-grade n-hexane prepared by this invention, when used for semiconductor wafer cleaning, can efficiently remove particles, organic contaminants, and residual metal ions from the wafer surface, significantly reducing leakage current in semiconductor devices after cleaning and greatly improving device yield. Compared to commercially available products and products prepared using traditional processes, the product of this invention can be stably adapted to higher-precision advanced semiconductor processes, overcoming the limitation of existing products that can only be adapted to lower-precision processes. It provides reliable cleaning reagent support for advanced semiconductor manufacturing and has significant industrial application value. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1:

[0020] (1) Raw material pretreatment: Take 50L of industrial-grade n-hexane, with an initial purity of 90%, containing 0.1% acidic impurities, 0.3% aromatics, and 60ppm water; Add 3% sodium hydroxide solution by volume of the raw material. The mass fraction of this solution is 8%. After neutralization, the pH of the aqueous phase needs to reach 6.8. If the pH is below 8%, the neutralization is incomplete, and if it is above 12%, residual alkali is likely to remain. Stirring at 25℃ and 180 rpm for 25 minutes ensures sufficient contact between the alkali solution and the raw materials, with a contact efficiency of 95%. After settling and separating, the oil phase is taken and its resistivity is used. The raw material was washed twice with deionized water, with each wash using 8% of the raw material volume. After washing, the pH of the aqueous phase reached 6.8. Add 0.3% anhydrous magnesium sulfate by weight of the raw material. Anhydrous sodium sulfate can also meet the drying requirements. The moisture content after drying should be ≤60ppm. After standing for 1.5h, filter to obtain pretreated n-hexane with a moisture content of 45ppm.

[0021] (2) Atmospheric distillation: Pretreated n-hexane is fed into a packed distillation column with 25 trays. This number of trays ensures that the light component pentane residue is ≤0.1% and the heavy component heptane residue is ≤0.15%. The column top temperature is controlled at 66℃, which is the lower limit of the boiling point of n-hexane. A deviation of 1℃ from this temperature will result in a decrease in purity of ≥0.3%. The reflux ratio is controlled at 2:1. A reflux ratio lower than 2:1 will result in excessive residue of heavy components, while a reflux ratio higher than 4:1 will increase energy consumption by ≥30%. The top fraction of the column was collected to obtain crude n-hexane with a purity of 99.2% and 800 ppm of aromatics.

[0022] (3) Composite adsorption: The flow rate was 0.8 mL / min through a 40 cm high adsorption column. Columns shorter than 40 cm were easily penetrated, while those taller than 60 cm experienced excessive resistance. The column is filled with 3A molecular sieve and activated alumina in a mass ratio of 1:1. The 3A molecular sieve can be replaced with 4A molecular sieve. The moisture adsorption capacity must be ≥20%. The activated alumina has a specific surface area of ​​280 m² / g and must meet the requirement of aromatic hydrocarbon adsorption capacity ≥15 mg / g. The adsorption temperature is controlled at 35℃. At temperatures below 35℃, the residual moisture adsorption is ≥12ppm, and at temperatures above 45℃, the risk of aromatic desorption increases. The adsorbed n-hexane contained 10 ppm water and 200 ppm aromatics.

[0023] (4) Ultra-clean filtration: After filtration through a 0.08μm polytetrafluoroethylene (PTFE) filter element, the filter element pore size must meet the requirement of ≤5 particles > 0.5μm / mL. The PTFE filter element can be replaced with a polypropylene filter element. Electronic-grade n-hexane product 1 was obtained, with a purity of 99.85% and a metal ion content of 10 ppb. Example 2:

[0024] (1) Raw material pretreatment: Take 100L of industrial-grade n-hexane with an initial purity of 95%, containing 0.3% acidic impurities, 0.5% aromatics, and 80ppm water; Add 5% sodium hydroxide solution by volume of the raw material. The solution has a mass fraction of 10%. After neutralization, the pH of the aqueous phase reaches 7.0. Neutralization is incomplete if the pH is below 8%, and residual alkali is easily left if the pH is above 12%. Stirring at 30℃ and 200rpm for 30 minutes ensures sufficient contact between the alkali solution and the raw materials, with a contact efficiency of 98%. After settling and separating, the oil phase is taken and its resistivity is used. The raw material was washed three times with deionized water, with each wash using 10% of the raw material volume. After washing, the pH of the aqueous phase reached 7.0. Add 0.5% anhydrous sodium sulfate by weight of the raw material. Anhydrous magnesium sulfate can also meet the drying requirements. The moisture content after drying should be ≤60ppm. After standing for 2 hours, filter to obtain pretreated n-hexane with a moisture content of 40ppm.

[0025] (2) Atmospheric distillation: Pretreated n-hexane is fed into a 30-plate distillation column, which ensures that the light component pentane residue is ≤0.1% and the heavy component heptane residue is ≤0.15%. The column top temperature is controlled at 68℃, which is the standard boiling point of n-hexane. Excessive deviation will result in a purity decrease of ≥0.3%. The reflux ratio is controlled at 3:1. A reflux ratio lower than 2:1 will result in excessive residue of heavy components, while a reflux ratio higher than 4:1 will increase energy consumption by ≥30%. The top fraction of the column was collected to obtain crude n-hexane with a purity of 99.5% and 750 ppm of aromatics.

[0026] (3) Composite adsorption: The flow rate was 1.0 mL / min through a 50 cm high adsorption column. Columns with a height below 40 cm were easily penetrated, while those above 60 cm experienced excessive resistance. The column is filled with 4A molecular sieve and activated alumina at a mass ratio of 1:1.5. The 4A molecular sieve can be replaced with 3A molecular sieve, and the moisture adsorption capacity must be ≥20%. The activated alumina has a specific surface area of ​​300 m². 2 / g, which must meet the requirement of aromatic adsorption capacity ≥15mg / g; The adsorption temperature is controlled at 40℃. At temperatures below 35℃, the residual moisture adsorption is ≥12ppm, and at temperatures above 45℃, the risk of aromatic desorption increases. The adsorbed n-hexane contained 8 ppm water and 180 ppm aromatics.

[0027] (4) Ultra-clean filtration: After filtration through a 0.1μm polypropylene filter cartridge, the filter cartridge pore size must meet the requirement of ≤5 particles > 0.5μm / mL. The polypropylene filter cartridge can be replaced with a polytetrafluoroethylene filter cartridge. Electronic-grade n-hexane product 2 was obtained, with a purity of 99.90% and 8 ppb of metal ions. Example 3:

[0028] (1) Raw material pretreatment: Take 200L of industrial-grade n-hexane, with an initial purity of 97%, containing 0.5% acidic impurities, 0.8% aromatics, and 100ppm water; Add 8% sodium hydroxide solution by volume of the raw material. The mass fraction of this solution is 12%. After neutralization, the pH of the aqueous phase needs to reach 7.2. If the pH is below 8%, the neutralization will not be complete, and if it is above 12%, residual alkali will easily remain. Stirring at 35℃ and 220 rpm for 35 minutes ensures sufficient contact between the alkali solution and the raw materials, with a contact efficiency of 98%. After settling and separating, the oil phase is taken and its resistivity is used. The raw material was washed four times with deionized water, with each wash using 15% of the raw material volume. After washing, the pH of the aqueous phase reached 7.2. Add 0.8% anhydrous magnesium sulfate by weight of the raw material. Anhydrous sodium sulfate can also meet the drying requirements. The moisture content after drying should be ≤60ppm. After standing for 2.5 hours, filter to obtain pretreated n-hexane with a moisture content of 35ppm.

[0029] (2) Atmospheric distillation: Pretreated n-hexane is fed into a 35-plate distillation column, which ensures that the light component pentane residue is ≤0.1% and the heavy component heptane residue is ≤0.15%. The column top temperature is controlled at 70℃, which is the upper limit of the boiling point of n-hexane. A deviation of 1℃ from this temperature will result in a decrease in purity of ≥0.3%. The reflux ratio is controlled at 4:1. A reflux ratio lower than 2:1 will result in excessive residue of heavy components, while a reflux ratio higher than 4:1 will increase energy consumption by ≥30%. The top fraction was collected to obtain crude n-hexane with a purity of 99.7% and 850 ppm of aromatics.

[0030] (3) Composite adsorption: The flow rate was 1.2 mL / min through a 60 cm high adsorption column. Columns with a height below 40 cm were easily penetrated, while those above 60 cm experienced excessive resistance. The column is filled with 5A molecular sieve and activated alumina in a mass ratio of 1:2. The 5A molecular sieve can be replaced with 3A / 4A molecular sieve, and the moisture adsorption capacity must be ≥20%. The specific surface area of ​​the activated alumina is 320 m². 2 / g, which must meet the requirement of aromatic adsorption capacity ≥15mg / g; The adsorption temperature is controlled at 45℃. At temperatures below 35℃, the residual moisture adsorption is ≥12ppm, and at temperatures above 45℃, the risk of aromatic desorption increases. The adsorbed n-hexane contained 12 ppm water and 220 ppm aromatics.

[0031] (4) Ultra-clean filtration: After filtration through a 0.12μm polytetrafluoroethylene (PTFE) filter cartridge, the filter cartridge pore size must meet the requirement of ≤5 particles > 0.5μm / mL. The PTFE filter cartridge can be replaced with a polypropylene filter cartridge. Electronic-grade n-hexane product 3 was obtained, with a purity of 99.92% and 6 ppb of metal ions. Example 4:

[0032] (1) Based on Example 2, only the composite adsorption step was adjusted, while the remaining steps were completely consistent with Example 2: (2) Composite adsorption: The adsorption column is filled with 3A molecular sieve in a mass ratio of 1:1:1, active alumina with amino groups loaded on the surface, and aminophosphonic acid type metal chelating resin (brand name D401). 3A molecular sieves must meet the requirement of ≤8 ppm after water adsorption; modified activated alumina with an amino loading of 3 wt% must meet the requirement of ≤100 ppm after aromatic hydrocarbon adsorption; below 3 wt%, the adsorption capacity is insufficient, and above 7 wt%, it is prone to agglomeration; metal chelating resins must meet the requirement of ≤5 ppb after metal ion adsorption, and its adsorption capacity for Na+ must be ≤5 ppb. + Fe 3+ Selectivity coefficient ≥ 80; The adsorption temperature is controlled at 45℃. Increasing the temperature can enhance the activity of the chelating resin. Below 45℃, the residual metal ions are ≥6ppb, and above 55℃, the resin life is shortened by ≥20%. The flow rate is controlled at 0.6 mL / min. This flow rate ensures sufficient contact between the resin and the material. Flow rates higher than 1.0 mL / min increase the risk of metal ion penetration. (3) The remaining steps are the same as in Example 2; Product properties: Electronic grade n-hexane product 4 was obtained, with 4 ppb of metal ions, 100 ppm of aromatics, and 8 ppm of moisture. Example 5:

[0033] (1) Based on Example 2, only the composite adsorption step was adjusted, while the remaining steps were completely consistent with Example 2: (2) Composite adsorption: The adsorption column is filled with 4A molecular sieve in a mass ratio of 2:2:1, activated alumina with hydroxyl-loaded surface, and carboxylic acid type metal chelating resin (grade D113). 4A molecular sieves must meet the requirement of ≤8 ppm after water adsorption; modified activated alumina with an amino loading of 5 wt% must meet the requirement of ≤100 ppm after aromatic hydrocarbon adsorption; below 3 wt% has insufficient adsorption capacity, and above 7 wt% is prone to agglomeration; metal chelating resins must meet the requirement of ≤5 ppb after metal ion adsorption, and its adsorption capacity for Na+ must be ≤5 ppm. + Fe 3+ Selectivity coefficient ≥ 80; The adsorption temperature is controlled at 50℃. Increasing the temperature can enhance the activity of the chelating resin. Below 45℃, the residual metal ions are ≥6ppb, and above 55℃, the resin life is shortened by ≥20%. The flow rate is controlled at 0.8 mL / min. This flow rate ensures sufficient contact between the resin and the material. Flow rates higher than 1.0 mL / min increase the risk of metal ion penetration. (3) The remaining steps are the same as in Example 2; Product properties: Electronic grade n-hexane product 5 was obtained, with 3 ppb of metal ions, 80 ppm of aromatics, and 6 ppm of moisture. Example 6:

[0034] (1) Based on Example 2, only the composite adsorption step was adjusted, while the remaining steps were completely consistent with Example 2: (2) Composite adsorption: The adsorption column was filled with 5A molecular sieve in a mass ratio of 3:3:1, modified silica gel with amino-loaded surface, and imine diacetic acid type metal chelating resin (brand name D403). 5A molecular sieves must meet the requirement of ≤8 ppm after water adsorption; modified silica gel with an amino loading of 7 wt% must meet the requirement of ≤100 ppm after aromatic hydrocarbon adsorption, below 3 wt% the adsorption capacity is insufficient, and above 7 wt% it is prone to agglomeration; metal chelating resins must meet the requirement of ≤5 ppb after metal ion adsorption, and its adsorption capacity for Na+ must be ≤5 ppm. + Fe 3+ Selectivity coefficient ≥ 80; The adsorption temperature is controlled at 55℃. Increasing the temperature can enhance the activity of the chelating resin. Below 45℃, the residual metal ions are ≥6ppb, and above 55℃, the resin life is shortened by ≥20%. The flow rate is controlled at 1.0 mL / min. This flow rate ensures sufficient contact between the resin and the material. Flow rates higher than 1.0 mL / min increase the risk of metal ion penetration. (3) The remaining steps are the same as in Example 2; Product properties: Electronic grade n-hexane product 6 was obtained, with 2 ppb of metal ions, 70 ppm of aromatics, and 4 ppm of moisture. Example 7:

[0035] (1) Based on Example 5, the atmospheric distillation + vacuum distillation steps are adjusted, while the remaining steps are completely consistent with Example 5: (2) Post-treatment of atmospheric distillation: The crude n-hexane obtained in Example 5 was transferred into a vacuum distillation column with 35 trays. The column is a tray column, and the number of trays must meet the requirement that the residual heavy component is ≤0.05%. The tray column can be replaced by a packed column. The vacuum level is controlled at 0.092 MPa. If the vacuum level is lower than 0.092 MPa, energy consumption increases by ≥40%, and if it is higher than 0.098 MPa, the boiling point increases, resulting in a cracking rate of ≥0.03%. The temperature at the top of the column is controlled at 42℃. Within this temperature range, the thermal cracking rate of n-hexane is ≤0.02%. Above 48℃, the cracking rate increases sharply. The reflux ratio is controlled at 4:1. If the reflux ratio is lower than 4:1, the purity is ≤99.95%; if it is higher than 6:1, the production efficiency decreases by ≥25%. (3) The remaining steps are the same as in Example 5; Product performance: Electronic grade n-hexane product 7 was obtained, with a purity of 99.96%, thermal decomposition impurities of 0.02%, metal ions of 3 ppb, aromatics of 80 ppm, and moisture of 6 ppm. Example 8:

[0036] (1) Based on Example 5, the atmospheric distillation + vacuum distillation steps are adjusted, while the remaining steps are completely consistent with Example 5: (2) Post-treatment of atmospheric distillation: The crude n-hexane obtained in Example 5 was transferred into a vacuum distillation column with 40 trays. This column is a packed column, and the number of trays must meet the requirement that the residual heavy component is ≤0.05%. The packed column can be replaced by a plate column. The vacuum level is controlled at 0.095 MPa. If the vacuum level is lower than 0.092 MPa, energy consumption increases by ≥40%, and if it is higher than 0.098 MPa, the boiling point increases, resulting in a cracking rate of ≥0.03%. The temperature at the top of the column is controlled at 45℃. Within this temperature range, the thermal cracking rate of n-hexane is ≤0.02%. Above 48℃, the cracking rate increases sharply. The reflux ratio is controlled at 5:1. If the reflux ratio is lower than 4:1, the purity is ≤99.95%; if it is higher than 6:1, the production efficiency decreases by ≥25%. (3) The remaining steps are the same as in Example 5; Product performance: Electronic grade n-hexane product 8 was obtained with a purity of 99.98%, thermal decomposition impurities of 0.015%, metal ions of 3 ppb, aromatics of 80 ppm, and moisture of 6 ppm. Example 9:

[0037] (1) Based on Example 5, the atmospheric distillation + vacuum distillation steps are adjusted, while the remaining steps are completely consistent with Example 5: (2) Post-treatment of atmospheric distillation: The crude n-hexane obtained in Example 5 was transferred into a vacuum distillation column with 45 trays. The column is a tray column, and the number of trays must meet the requirement that the residual heavy component is ≤0.05%. The tray column can be replaced by a packed column. The vacuum level is controlled at 0.098 MPa. If the vacuum level is lower than 0.092 MPa, energy consumption increases by ≥40%, and if it is higher than 0.098 MPa, the boiling point increases, resulting in a cracking rate of ≥0.03%. The temperature at the top of the column is controlled at 48℃. Within this temperature range, the thermal cracking rate of n-hexane is ≤0.02%. Above 48℃, the cracking rate increases sharply. The reflux ratio is controlled at 6:1. If the reflux ratio is lower than 4:1, the purity is ≤99.95%. If the reflux ratio is higher than 6:1, the production efficiency decreases by ≥25%. (3) The remaining steps are the same as in Example 5; Product performance: Electronic grade n-hexane product 9 was obtained, with a purity of 99.99%, thermal decomposition impurities of 0.01%, metal ions of 3 ppb, aromatics of 80 ppm, and moisture of 6 ppm. Example 10:

[0038] (1) Based on Example 8, an ultraviolet oxidation-adsorption combined step is added, and the remaining steps are completely consistent with Example 8: (2) Ultraviolet oxidation treatment: After vacuum distillation, the fraction is passed into an ultraviolet reactor with a wavelength of 240 nm. This wavelength range can generate ozone to enhance oxidation and avoid the degradation of n-hexane caused by wavelengths of 180-220 nm. The UV reactor power is 80W. The oxidation efficiency is ≤60% when the power is below 80W, and there is no significant efficiency improvement when the power is above 120W. The oxygen volume ratio is 0.3%. This amount must be sufficient to ensure that the oxidation rate of unsaturated hydrocarbons is ≥85%. Excess oxygen will generate peroxides, while insufficient oxygen will result in incomplete oxidation. The reaction temperature is controlled at 32℃. If the temperature is below 32℃, the reaction time is ≥40min. If the temperature is above 38℃, the risk of peroxide formation increases. The reaction time is 25 minutes, and the unsaturated hydrocarbons need to be oxidized into polar oxides such as epoxides and alcohols. Adsorption linkage: The oxidized material is directly fed into the composite adsorption column of Example 5 without the need for additional equipment. Existing adsorbents are used to adsorb oxides, and the unsaturated hydrocarbons must be ≤8ppm. (3) The remaining steps are the same as in Example 8; Product performance: 10g of electronic grade n-hexane was obtained, with 6ppm of unsaturated hydrocarbons, no isomer impurities, purity of 99.98%, 0.015% thermal decomposition impurities, 3ppb of metal ions, 80ppm of aromatics, and 6ppm of moisture. Example 11:

[0039] (1) Based on Example 8, an additional step of UV-assisted hydrogen peroxide oxidation-adsorption is added, while the remaining steps are completely consistent with Example 8: (2) Ultraviolet-assisted hydrogen peroxide oxidation treatment: After vacuum distillation, the fraction is passed into an ultraviolet reactor with a wavelength of 250 nm. This wavelength range can generate ozone to enhance oxidation and avoid the degradation of n-hexane caused by wavelengths of 180-220 nm. The UV reactor power is 100W. When the power is below 80W, the oxidation efficiency is ≤60%, and when it is above 120W, there is no significant improvement in efficiency. Add hydrogen peroxide at a ratio of 0.2% to the mass of the material. This concentration must meet the requirement that the oxidation rate of unsaturated hydrocarbons is ≥85%. Excessive hydrogen peroxide will generate peroxides, while insufficient hydrogen peroxide will result in incomplete oxidation. The reaction temperature is controlled at 35℃. If the temperature is below 32℃, the reaction time is ≥40min. If the temperature is above 38℃, the risk of peroxide formation increases. The reaction time is 30 minutes, and the unsaturated hydrocarbons need to be oxidized into polar oxides such as epoxides and alcohols. Adsorption linkage: The oxidized material is directly fed into the composite adsorption column of Example 5 without the need for additional equipment. Existing adsorbents are used to adsorb oxides, and the unsaturated hydrocarbons must be ≤8ppm. (3) The remaining steps are the same as in Example 8; Product performance: Electronic grade n-hexane product 11 was obtained, with 4 ppm of unsaturated hydrocarbons, no isomer impurities, purity of 99.98%, 0.015% thermal decomposition impurities, 3 ppb of metal ions, 80 ppm of aromatics, and 6 ppm of moisture. Example 12:

[0040] (1) Based on Example 8, a plasma oxidation-adsorption combined step is added, and the remaining steps are completely consistent with Example 8: (2) Plasma oxidation treatment: After vacuum distillation, the fraction is passed into a low-temperature plasma oxidation device with a power of 50W. The device must meet the requirements of no hexane degradation and unsaturated hydrocarbons ≤8ppm. The oxygen volume ratio is 0.7%. This amount must meet the requirement that the oxidation rate of unsaturated hydrocarbons is ≥85%. Excess oxygen will generate peroxides, while insufficient oxygen will result in incomplete oxidation. The reaction temperature is controlled at 38℃. If the temperature is below 32℃, the reaction time is ≥40min. If the temperature is above 38℃, the risk of peroxide formation increases. The reaction time is 35 minutes, and the unsaturated hydrocarbons need to be oxidized into polar oxides such as epoxides and alcohols. Adsorption linkage: The oxidized material is directly fed into the composite adsorption column of Example 5 without the need for additional equipment. Existing adsorbents are used to adsorb oxides, and the unsaturated hydrocarbons must be ≤8ppm. (3) The remaining steps are the same as in Example 8; Product performance: 12g of electronic-grade n-hexane was obtained, with 3ppm of unsaturated hydrocarbons, no isomer impurities, purity of 99.98%, 0.015% thermal decomposition impurities, 3ppb of metal ions, 80ppm of aromatics, and 6ppm of moisture.

[0041] Comparative Example 1: Only the raw material pretreatment → atmospheric distillation → ultra-clean filtration steps of Example 2 were retained. The raw material pretreatment used a 5% sodium hydroxide solution by volume of the raw material; the mass fraction of this solution (15%) exceeded the parameter range of this invention. The atmospheric distillation reflux ratio of 1:1 exceeded the parameter range of this invention, resulting in Comparative Sample 1. Its properties were: metal ions 30 ppb, aromatics 850 ppm, purity 99.10%, water 40 ppm, unsaturated hydrocarbons 25 ppm, and particles >0.5 μm 15 particles / mL.

[0042] Comparative Example 2: In the composite adsorption step of Example 2, only ordinary activated alumina was used without modified or chelating resin, and the adsorbent ratio was 1:1. The remaining steps were the same as in Example 2, resulting in Comparative Sample 2. Its performance was as follows: metal ions 10 ppb, aromatics 250 ppm, purity 99.70%, water 15 ppm, unsaturated hydrocarbons 25 ppm, and 8 particles with a particle size >0.5 μm / mL.

[0043] Comparative Example 3: In Example 8, conventional vacuum distillation parameters were used: vacuum degree 0.085 MPa, column top temperature 52°C, and reflux ratio 2:1, all of which are conventional values ​​in the prior art. The remaining steps were the same as in Example 8, resulting in Comparative Sample 3. Its performance was as follows: purity 99.8%, thermal decomposition impurities 0.05%, metal ions 3 ppb, aromatics 80 ppm, water 6 ppm, and unsaturated hydrocarbons 15 ppm.

[0044] Comparative Example 4: Based on Example 8, the UV oxidation-adsorption method was replaced with Pd / C catalytic hydrogenation: a Pd / C catalyst was used, the hydrogen pressure was 0.2 MPa, and the reaction temperature was 45°C. The remaining steps were the same as in Example 8, resulting in Comparative Sample 4. Its properties were: 12 ppm unsaturated hydrocarbons, 0.03% hexane isomer, purity 99.97%, 0.015% thermal decomposition impurities, 2 ppb metal ions, 55 ppm aromatics, and 4 ppm water.

[0045] Table 1. Basic performance test results of Examples 1-6, Comparative Examples 1-2, and commercially available samples.

[0046] Table 2. Basic performance test results of Examples 7-12 and Comparative Examples 3-4

[0047] The test results are explained below: (1) As the amount of raw material increased from 50L to 200L, by adjusting parameters such as the amount of sodium hydroxide, the number of water washes, and the height of the adsorption column, the purity of n-hexane increased from 99.85% to 99.92%, the metal ion concentration decreased from 10ppb to 6ppb, and the particle size decreased from 6 particles / mL to 4 particles / mL. This demonstrates the adaptability of the basic process of this invention to different amounts of raw materials. Furthermore, by adjusting the parameters synchronously, the impurity removal efficiency can be stably controlled, avoiding performance fluctuations caused by the increase in the amount of raw materials.

[0048] (2) Compared with the basic scheme Example 2, Examples 4-6 use a combination of molecular sieve + modified adsorbent + chelating resin (ratio 1:1:1 to 3:3:1) to reduce metal ions from 8 ppb to 2 ppb, aromatic hydrocarbons from 180 ppm to 70 ppm, and moisture content is stable at ≤8 ppm.

[0049] The key reason is that the amino / hydroxyl groups of the modified adsorbent form π-π interactions with aromatics, and the aminophosphonic acid / carboxylic acid groups of the chelating resin form stable chelates with metal ions, thereby achieving the synergistic removal of water, aromatics, and metal ions and overcoming the limitations of single adsorbents in the basic solution.

[0050] (3) Based on the adsorption optimization in Example 5, in Examples 7-9, the purity of n-hexane was increased from 99.95% to 99.99% and the thermal decomposition impurities were reduced from 0.03% to 0.01% by adjusting the vacuum distillation parameters.

[0051] The core advantages are: balancing low boiling point and low cracking in the medium-high vacuum range, and enhancing the separation of heavy components with a high reflux ratio (5:1-6:1), avoiding the risks of excessive energy consumption or cracking caused by high temperature due to conventional low vacuum.

[0052] (4) Based on the optimization of distillation, in Examples 10-12, the unsaturated hydrocarbons were reduced from 15 ppm to 3 ppm by a combination of ultraviolet / plasma oxidation and adsorption, and no hexane isomers were generated.

[0053] The technical logic is as follows: 240-250nm ultraviolet light or low-temperature plasma oxidizes olefins into polar epoxides / alcohols, and the composite adsorption column can simultaneously adsorb the oxidation products without additional equipment. This avoids the precious metal costs and isomerization defects of the hydrogenation method, and achieves deep removal of unsaturated hydrocarbons. This is crucial for high-temperature semiconductor processes (such as 200℃ annealing) and can avoid the increase in leakage current caused by the polymerization of unsaturated hydrocarbons.

[0054] (5) Differences between the comparative examples and the present invention: Comparative examples: metal ions 30 ppb, aromatics 850 ppm, far higher than Examples 1-12, proving that composite adsorption is the core step in impurity control; Comparative Example 2: Metal ions 10 ppb, aromatics 250 ppm, which is 3-3.1 times that of Example 5, highlighting the necessity of modified adsorbent combination; Comparative Example 3: Purity 99.80%, thermal decomposition impurities 0.05%, performance only reached the basic level of Example 7, verifying the creativity of the distillation parameter optimization; Comparative Example 4: 12 ppm of unsaturated hydrocarbons containing 0.03% isomers; Example 11: only 4 ppm of unsaturated hydrocarbons with no isomers, demonstrating the advantages of the combined oxidation scheme.

[0055] (6) The core indicators of the embodiments of the present invention are comprehensively superior to those of commercially available samples: metal ions less than 3 ppb (commercially available 32 ppb), moisture less than 6 ppm (commercially available 40 ppm), aromatics less than 80 ppm (commercially available 920 ppm), and leakage current less than 2 × 10⁻⁶. -9 A (commercially available 5×10) -8A) proves that the technical solution of the present invention can meet the cleaning requirements of 12-inch advanced process (such as 7nm node), while commercially available samples are only compatible with 28nm and above nodes.

[0056] To verify the practicality, adaptability, and technical advantages of the electronic-grade n-hexane prepared in the various embodiments of the present invention in semiconductor cleaning scenarios, and to compare it with the prior art, clarify its ability to meet the cleaning requirements of advanced semiconductor processes, and ensure that the test process is repeatable and the results are verifiable.

[0057] (1) Test sample group Basic process group: Example 1, Example 2, Example 3.

[0058] Adsorption optimization group: Examples 4, 5, and 6.

[0059] Distillation-Adsorption Joint Optimization Group: Examples 7, 8, and 9.

[0060] Oxidation-adsorption joint optimization group: Examples 10, 11, and 12.

[0061] (2) Control sample group Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4.

[0062] Commercially available electronic-grade n-hexane sample.

[0063] Test items and methods: (1) Semiconductor wafer cleaning effect test Test subject: 12-inch silicon wafer, with pre-set surface contaminants: particles > 0.5μm, organic residues, and metal ions.

[0064] Cleaning process: Immersion + ultrasonic cleaning mode is adopted, cleaning temperature is 25℃, ultrasonic power is 300W, cleaning time is 5min, then rinsed with ultrapure water 3 times and dried with nitrogen.

[0065] Detection method: Particle residue: The number of particles >0.5μm on the wafer surface was counted using scanning electron microscopy (SEM).

[0066] Organic pollutant residues: X-ray photoelectron spectroscopy (XPS) analysis of residual carbon on wafer surface.

[0067] Metal ion residues: Inductively coupled plasma mass spectrometry (ICP-MS) was used to detect the total amount of Na, K, Fe, and Cu on the wafer surface.

[0068] The impact of semiconductor device performance testing is as follows: Test objects: 7nm node MOSFET devices (uncleaned test samples and samples after cleaning).

[0069] Detection method: Leakage current: The gate leakage current of the device is tested using a semiconductor parameter analyzer at a test voltage of 1.2V and a temperature of 25℃.

[0070] Yield: The percentage of 1000 devices that function normally after cleaning (based on leakage current < 2 × 10⁻⁶). -9 A represents the passing standard.

[0071] High temperature stability: After cleaning, the device was placed in an annealing furnace at 200℃ for 2 hours and then cooled. The leakage current change rate was measured again.

[0072] The process compatibility test is as follows: Raw material quantity compatibility: Comparing the cleaning effects of Example 1, Example 2, and Example 3, the compatibility standard was set at a coefficient of variation of less than 5% for particle residue and metal ion residue.

[0073] Process node compatibility: Devices at 28nm, 14nm, and 7nm nodes were cleaned using Example 12 and commercially available samples, respectively, to test whether the leakage current met the requirements of each node (28nm ≤ 5 × 10⁻⁶). -8 A, 14nm≤1×10 -8 A, 7nm≤2×10 -9 A).

[0074] The long-term stability test results are as follows: Sample storage conditions: The sample from Example 12 was sealed and stored in an environment of 40°C and 50% relative humidity for 6 months.

[0075] Testing content: Monthly sampling tests are conducted on purity, moisture, aromatics, and metal ion content. At the same time, the cleaning effect (particle residue, leakage current) is tested, and the rate of change of the indicators is observed.

[0076] The test results are as follows: Table 3. Wafer Cleaning Results

[0077] Table 4 Results of the impact on device performance

[0078] The process compatibility results are as follows: Raw material quantity suitability: The coefficient of variation for particle residue in Examples 1, 2, and 3 was 3.2%, and the coefficient of variation for metal ion residue was 2.8%, both <5%, which meets the production requirements for different raw material quantities.

[0079] Process node adaptability: Example 12: The leakage current of 28nm, 14nm, and 7nm devices all met the standard (1×10⁻⁶ respectively). -8 A, 5×10-9 A, 8×10 -10 A).

[0080] Commercially available samples: Leakage current meets standards for cleaning 28nm devices (4×10) -8 A) The leakage current of 14nm and 7nm devices exceeded the standard during cleaning (1.5×10⁻⁶ respectively). -7 A, 3×10 -7 A).

[0081] The long-term stability results are as follows: Example 12: Sample stored for 6 months: The purity decreased from 99.98% to 99.97%, the moisture content increased from 6 ppm to 8 ppm, the aromatic hydrocarbon content increased from 80 ppm to 85 ppm, and the metal ion content increased from 3 ppb to 4 ppb.

[0082] After cleaning, 3 wafer particles remained per wafer, and the device leakage current was 1×10⁻⁶. -9 A, all meet the 7nm process requirements.

[0083] The test results are as follows: Practicality verification: The electronic-grade n-hexane prepared in each embodiment of the present invention can effectively clean semiconductor wafers, and the leakage current and yield of the cleaned devices meet the requirements of semiconductor process. Among them, Examples 7-12 can be stably adapted to 12-inch 7nm advanced process, proving that the invention has practical application value.

[0084] Comparative Examples 1-2: Examples 4-6 used a combination of molecular sieve, modified adsorbent, and chelating resin for adsorption, which reduced the residual metal ions from 30 ppb to 3 ppb and aromatic hydrocarbons from 850 ppm to 80 ppm, overcoming the limitations of single adsorbents in impurity removal and demonstrating technological improvement.

[0085] Comparative Example 3: Examples 7-9 By optimizing the reduced pressure distillation parameters, the purity increased from 99.80% to 99.99%, and the thermal cracking impurities decreased from 0.05% to 0.01%, avoiding the problems of high energy consumption and high cracking risk of conventional distillation.

[0086] Comparative Example 4 and Commercially Available Samples: Examples 10-12 show that through UV / plasma oxidation, unsaturated hydrocarbons were reduced from 25 ppm to 3 ppm with no isomers generated. After cleaning, the leakage current of the device was an order of magnitude lower than that of commercially available samples, making it suitable for 7nm processes. This is significantly better than existing technologies and demonstrates inventiveness.

[0087] Adaptability and stability: The process of this invention can be adapted to different raw material quantities of 50-200L, and the samples still meet the cleaning requirements of advanced processes after 6 months of storage, proving that the technical solution is stable and reliable and has the potential for industrial application.

[0088] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A method for preparing electronic-grade n-hexane for semiconductor cleaning, characterized in that, The method includes the following steps: (1) Raw material pretreatment: Take industrial grade n-hexane, add sodium hydroxide solution to neutralize, let stand and separate into layers, take the oil phase, wash with deionized water, add desiccant to dry, let stand and filter to obtain pretreated n-hexane; (2) Atmospheric pressure distillation: Pretreated n-hexane is fed into a distillation column, the top temperature and reflux ratio are controlled, the top fraction is collected, and crude n-hexane is obtained; (3) Composite adsorption: crude n-hexane is passed through an adsorption column filled with adsorbent at a set flow rate and the adsorption temperature is controlled to obtain adsorbed n-hexane; the adsorbent contains at least molecular sieve and activated alumina; (4) Ultra-clean filtration: The adsorbed n-hexane is filtered through a filter element to obtain electronic-grade n-hexane; the filter element material is polytetrafluoroethylene or polypropylene.

2. The preparation method according to claim 1, characterized in that, In step (1), the volume fraction of the sodium hydroxide solution is 8%-12%, and the amount used is 3%-8% of the raw material volume. After neutralization, the pH of the aqueous phase is 6.8-7.2; the resistivity of the deionized water is... The washing process involves 2-4 water washes, with each wash using 8%-15% of the raw material volume. The desiccant is anhydrous magnesium sulfate or anhydrous sodium sulfate, used at 0.3%-0.8% of the raw material mass. After drying, the moisture content of the pretreated n-hexane is ≤60ppm.

3. The preparation method according to claim 1, characterized in that, In step (2), the distillation column is a packed distillation column or a plate distillation column with 25-35 plates; the top temperature is 66-70℃ and the reflux ratio is 2:1-4:

1.

4. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of molecular sieve to activated alumina is 1:1-1:2; the molecular sieve is 3A, 4A, or 5A; and the specific surface area of ​​the activated alumina is ≥280 m². 2 / g; the adsorption column height is 40-60cm, the flow rate is 0.8-1.2mL / min, and the adsorption temperature is 35-45℃.

5. The preparation method according to claim 4, characterized in that, In step (3), the adsorbent also includes a metal chelating resin. The mass ratio of molecular sieve, activated alumina and metal chelating resin is 1:1:1-3:3:

1. The metal chelating resin is aminophosphonic acid type, carboxylic acid type or imine diacetic acid type. The adsorption temperature is adjusted to 45-55℃ and the flow rate is adjusted to 0.6-1.0mL / min.

6. The preparation method according to claim 1, characterized in that, Step (2) after atmospheric distillation also includes a vacuum distillation step: crude n-hexane is fed into a vacuum distillation column, the vacuum degree, the top temperature and the reflux ratio are controlled, and the top fraction is collected; the vacuum distillation column is a plate column or a packed column, with 35-45 plates; the vacuum degree is 0.092-0.098 MPa, the top temperature is 42-48℃, and the reflux ratio is 4:1-6:

1.

7. The preparation method according to claim 6, characterized in that, The process after vacuum distillation also includes an oxidation-adsorption combined treatment step: the fraction from vacuum distillation is subjected to ultraviolet oxidation treatment, and the oxidized material is directly introduced into the composite adsorption column in step (3); the wavelength of the ultraviolet oxidation is 240-250nm, the power is 80-120W, the oxygen volume ratio is 0.3%-0.7%, the reaction temperature is 32-38℃, and the reaction time is 25-35min.

8. The preparation method according to claim 7, characterized in that, Ultraviolet oxidation is replaced by ultraviolet-assisted hydrogen peroxide oxidation; the mass ratio of hydrogen peroxide to material is 0.2%-0.5%.

9. The preparation method according to claim 7, characterized in that, Ultraviolet oxidation is replaced by plasma oxidation; the plasma oxidation equipment has a power of 50-80W, an oxygen volume ratio of 0.3%-0.7%, a reaction temperature of 32-38℃, and a reaction time of 30-35min.

10. The application of electronic-grade n-hexane prepared by the method of any one of claims 1-9 in semiconductor cleaning.

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