A method and system for purifying high-purity tetraethyl orthosilicate

Abstract

The application belongs to the technical field of semiconductors, and particularly relates to a high-purity tetraethyl orthosilicate purification method and a purification system. The purification method comprises the following steps: performing primary adsorption treatment on crude tetraethyl orthosilicate by using an adsorbent I, and then performing solid-liquid separation, wherein the obtained liquid product is tetraethyl orthosilicate adsorption liquid; the adsorbent I simultaneously contains chitosan, zeolite and shell activated carbon; performing vacuum distillation on the tetraethyl orthosilicate adsorption liquid under the condition that the temperature is 70-100 DEG C and the vacuum degree is less than or equal to 60 kPa, and then performing condensation on the obtained gaseous product to obtain tetraethyl orthosilicate distillation liquid; and performing filtration on the tetraethyl orthosilicate distillation liquid to remove particulate matter with a particle size of less than or equal to 0.1 microns, thereby obtaining high-purity tetraethyl orthosilicate. The method provided by the application can be used to obtain electronic-grade tetraethyl orthosilicate with a purity of not less than 99.999999%.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor technology, and particularly relates to a method and system for purifying high-purity tetraethyl orthosilicate. Background Technology

[0002] Electronic grade tetraethyl orthosilicate (TEOS) is widely used in chemical vapor deposition processes to form silicon dioxide deposits, thereby blocking contaminants and impurities from entering semiconductor devices. It can also be used to create conductive or insulating layers, antireflective films to improve light absorption, and temporarily block etching.

[0003] Electronic-grade tetraethyl orthosilicate (TEO) typically requires a purity of 99.999999%. It is prepared primarily by purifying industrial-grade TEO, which generally has a purity of 99%, still containing about 1% impurities. These impurities include electronically active and non-electronic impurities. Electronically active impurities are metal ions, which reduce the insulation performance of SiO2 thin films deposited in semiconductor devices, leading to micrometer-level interconnections and ultimately rendering the circuit board unusable. Non-electronic impurities include organic matter and water, which affect the film's physical properties by altering the surface structure integrity and planar uniformity.

[0004] US5840953 discloses a method for preparing electronic-grade tetraethyl orthosilicate using gas chromatography, employing lithium hydride to remove impurities, resulting in a tetraethyl orthosilicate product with a purity of not less than 99.999999% and a moisture content of less than 2 ppm. Since gas chromatographs are mainly used for the analysis and detection of trace elements, and gas chromatograph equipment is expensive, this method has a high cost. Summary of the Invention

[0005] The present invention aims to provide a purification method and system for obtaining electronic-grade tetraethyl orthosilicate with a purity of not less than 99.999999% at low cost.

[0006] Specifically, the purification method for tetraethyl orthosilicate provided by the present invention includes the following steps:

[0007] S1. Crude tetraethyl orthosilicate is subjected to initial adsorption treatment with adsorbent I, followed by solid-liquid separation. The resulting liquid product is tetraethyl orthosilicate adsorbent solution. Adsorbent I contains chitosan, zeolite, and activated carbon from fruit shells.

[0008] S2. The tetraethyl orthosilicate adsorbent solution is distilled under reduced pressure at a temperature of 70-100℃ and a vacuum degree of ≤60kPa. The resulting gaseous product is condensed to obtain tetraethyl orthosilicate distillate.

[0009] S3. Filter the tetraethyl orthosilicate distillate to remove particulate matter with a particle size of less than 0.1 μm to obtain high-purity tetraethyl orthosilicate.

[0010] The purification system for tetraethyl orthosilicate provided by the present invention includes a first adsorption device, a distillation device, a cooling device, and a filtration device connected in sequence. The first adsorption device is filled with an adsorbent I containing chitosan, zeolite, and activated carbon from fruit shells. The filtration device is capable of removing particulate matter with a particle size of less than 0.1 μm.

[0011] The key to this invention lies in the use of adsorption treatment, vacuum distillation, and filtration, with chitosan, zeolite, and activated carbon from fruit shells working synergistically as adsorbents. This facilitates the removal of metal ions from tetraethyl orthosilicate, ensuring that the purity of the obtained tetraethyl orthosilicate is not less than 99.999999% (W / W). Activated carbon from fruit shells has a large specific surface area and high adsorption capacity, effectively adsorbing both electronically active and non-electronically active impurities in the system. Chitosan is a linear polysaccharide polymer; its amino groups can coordinate with metal cations, resulting in chemisorption and excellent adsorption of metal ions. However, its poor mechanical properties and poor spreadability can easily lead to the "embedding" of active amino groups, preventing it from exerting its maximum adsorption effect. Zeolite, with its unique pore structure and thermal stability, not only has excellent adsorption properties but also compensates for the lack of mechanical strength in chitosan, maximizing its adsorption activity. In other words, this invention combines chitosan, zeolite, and activated carbon from fruit shells to leverage the advantages of activated carbon from fruit shells having a large adsorption capacity, chitosan having a strong chelating ability, and zeolite having high mechanical properties. The three have a synergistic effect, exhibiting super adsorption capacity for electronic and non-electronic impurities in crude tetraethyl orthosilicate, while also removing moisture and improving the purity of the tetraethyl orthosilicate product.

[0012] In a preferred embodiment of the present invention, the activated carbon is coconut shell activated carbon, which can more effectively reduce electronic and non-electronic impurities in crude tetraethyl orthosilicate, exhibiting stronger impurity removal capabilities. This is presumably because coconut shell activated carbon possesses a unique small-molecule pore structure with well-developed pores and acidic functional groups on its surface, giving it a strong adsorption capacity for both electronic and non-electronic impurities in the system.

[0013] In another embodiment of the present invention, the purification method of tetraethyl orthosilicate provided by the present invention further includes, after step S2 and before step S3, deep adsorption treatment of the tetraethyl orthosilicate distillate with adsorbent II, wherein adsorbent II contains cation exchange resin, carbon nanotubes and zeolite, thereby increasing the purity of the obtained tetraethyl orthosilicate to 99.9999999% (W / W). Detailed Implementation

[0014] The purification method for tetraethyl orthosilicate provided by this invention includes the following steps:

[0015] S1. Crude tetraethyl orthosilicate is subjected to initial adsorption treatment with adsorbent I, followed by solid-liquid separation. The resulting liquid product is tetraethyl orthosilicate adsorbent solution. Adsorbent I contains chitosan, zeolite, and activated carbon from fruit shells.

[0016] S2. The tetraethyl orthosilicate adsorbent solution is distilled under reduced pressure at a temperature of 70-100℃ and a vacuum degree of ≤60kPa. The resulting gaseous product is condensed to obtain tetraethyl orthosilicate distillate.

[0017] S3. Filter the tetraethyl orthosilicate distillate to remove particulate matter with a particle size of less than 0.1 μm to obtain high-purity tetraethyl orthosilicate.

[0018] In this invention, in step S1, the preferred mass ratio of chitosan, zeolite, and activated carbon from fruit shells in adsorbent I is (1-3):(1-2):1. Based on 1 part by weight of activated carbon from fruit shells, the preferred content of chitosan is 1-3 parts by weight, such as 1, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.8, or 3 parts by weight, or any value between them; the preferred content of zeolite is 1-2 parts by weight, such as 1, 1.2, 1.5, 1.8, or 2 parts by weight, or any value between them. Through numerous experiments, the inventors of this invention discovered that when the mass ratio of chitosan, zeolite, and activated carbon from fruit shells in adsorbent I is 2:2:1, the adsorption effect on impurities is better. It is speculated that at this ratio, these three components can absorb different types of impurities respectively, and through optimal combination, the impurities in the system are more thoroughly adsorbed, and the purity of the product can reach 99.9999999%.

[0019] In a preferred embodiment, in step S1, the chitosan can be acid-soluble chitosan and / or water-soluble chitosan. The acid-soluble chitosan is preferably a chitosan with a high degree of deacetylation, such as 85%, 90%, or 95%. The water-soluble chitosan can be selected from at least one of chitosan hydrochloride, chitosan quaternary ammonium salt, and carboxymethyl chitosan. The chitosan can be derived from black tiger shrimp shells, domestic crab shells, domestic shrimp shells, crayfish shells, etc.

[0020] In a preferred embodiment, in step S1, the particle size of the fruit shell activated carbon is 5-30 mesh, such as 5, 8, 10, 12, 15, 18, 20, 25, 30 mesh or any value between them; the moisture content is ≤10%, such as 10%, 8%, 5%, 2%, 1%, 0.1%, 0 or any value between them; and the specific surface area is 1000-1300 m². 2 / g, such as 1000, 1050, 1100, 1150, 1200, 1250, 1300m 2 / g or any value between them. Furthermore, the activated carbon from the fruit shells can specifically be at least one of peach shell activated carbon, apricot shell activated carbon, coconut shell activated carbon, jujube shell activated carbon, etc.

[0021] In a preferred embodiment, in step S1, the conditions for the initial adsorption treatment include a temperature of 20–40°C, such as 20°C, 25°C, 30°C, 35°C, 40°C, or any value between them; and a liquid hourly space velocity of 5–50 h⁻¹. -1 , such as 5h -1 10h -1 15h -1 20h -1 25h -1 30h -1 35h -1 40h -1 45h -1 50h -1 Or any value in between. In this invention, the term "liquid hourly space velocity" refers to the volume of liquid passing through a unit volume of adsorbent per unit time.

[0022] In this invention, the solid-liquid separation method in step S1 can be centrifugal separation, pressure filtration, vacuum filtration, etc., with centrifugal separation being preferred.

[0023] In this invention, the purpose of the vacuum distillation in step S2 is to further remove electronically active impurities and non-electronic impurities from tetraethyl orthosilicate. The vacuum distillation temperature is 70–100°C, such as 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, or any value between them; the vacuum degree is ≤60 kPa, such as 10 kPa, 20 kPa, 30 kPa, 40 kPa, 50 kPa, 60 kPa, or any value between them. In a preferred embodiment, step S2 includes a first vacuum distillation and a second vacuum distillation performed sequentially. The first vacuum distillation temperature is 90–100°C and the vacuum degree is 50–60 kPa, and the second vacuum distillation temperature is 70–90°C and the vacuum degree is 40–50 kPa. Since tetraethyl orthosilicate has a boiling point of 168°C under normal pressure, distillation under normal pressure will easily cause it to decompose before reaching its boiling point. Vacuum distillation can lower its boiling point and prevent thermal decomposition. Using two consecutive vacuum distillations can more effectively remove electronically active and non-electronically active impurities from the crude tetraethyl orthosilicate, further improving the purity of the product. Furthermore, the condensation is preferably performed using circulating cooling water. The temperature of the circulating cooling water is preferably 20–30°C.

[0024] In this invention, the purpose of filtration in step S3 is to remove particulate matter with a particle size of less than 0.1 μm from the tetraethyl orthosilicate distillate. In a preferred embodiment, step S3 includes a first-stage filtration and a second-stage filtration performed sequentially. The filter used in the first-stage filtration has a pore size of less than 100 nm, and the filter used in the second-stage filtration has a pore size of less than 50 nm. This allows for more thorough removal of electronically active and non-electronically active impurities from the tetraethyl orthosilicate.

[0025] In a preferred embodiment of the present invention, the purification method of tetraethyl orthosilicate further includes, after step S2 and before step S3, deep adsorption treatment of the tetraethyl orthosilicate distillate using adsorbent II, wherein adsorbent II simultaneously contains cation exchange resin, carbon nanotubes, and zeolite. This allows for more thorough removal of impurities from the crude tetraethyl orthosilicate, yielding tetraethyl orthosilicate with a purity of not less than 99.9999999%. The cation exchange resin can remove metal ions through cation exchange. The cation exchange resin can be a strongly acidic cation exchange resin, a weakly acidic cation exchange resin, or a mixture of both, preferably a strongly acidic cation exchange resin. The strongly acidic cation exchange resin can be a styrene-based strongly acidic cation exchange resin and / or an acrylic-based strongly acidic cation exchange resin, preferably a styrene-based strongly acidic cation exchange resin. The functional group of the styrene-based strongly acidic cation exchange resin is preferably a sulfonic acid group, and the total exchange capacity is preferably 1.5–3 mmol / mL. The carbon nanotubes also exhibit perfect adsorption of metal ions. The diameter of the carbon nanotubes is preferably 10–30 nm, and the length is preferably 0.5–2 μm. As mentioned above, zeolite has a unique pore structure and thermal stability, which not only provides excellent adsorption but also improves the mechanical strength of the adsorbent and prolongs its effective adsorption time. The preferred mass ratio of cation exchange resin, carbon nanotubes, and zeolite in adsorbent II is (5–10):(0.1–0.5):1. Based on 1 part by weight of zeolite, the content of the cation exchange resin is 5–10 parts by weight, such as 5, 6, 7, 8, 9, 10 parts by weight or any value between them; the content of the carbon nanotubes is 0.1–0.5 parts by weight, such as 0.1, 0.2, 0.3, 0.4, 0.5 parts by weight or any value between them. Through numerous experiments, the inventors of this invention discovered that when the mass ratio of cation exchange resin, carbon nanotubes, and zeolite in the adsorbent II is 8:0.3:1, it is more conducive to the removal of impurities in crude tetraethyl orthosilicate. It is speculated that at this ratio, these three components can absorb different types of impurities respectively, and the optimal combination allows the impurities in the system to be more thoroughly adsorbed.

[0026] In a preferred embodiment, the conditions for the deep adsorption treatment include a temperature of 20–40°C, such as 20°C, 25°C, 30°C, 35°C, 40°C, or any value between them; and a liquid hourly space velocity of 5–50 h⁻¹. -1 , such as 5h -1 10h -1 15h -1 20h -1 25h -1 30h -1 35h -1 40h -1 45h -1 50h -1 Or any value between them.

[0027] The purification system for tetraethyl orthosilicate provided by the present invention includes a first adsorption device, a distillation device, a cooling device, and a filtration device connected in sequence. The first adsorption device is filled with an adsorbent I containing chitosan, zeolite, and activated carbon from fruit shells. The filtration device is capable of removing particulate matter with a particle size of less than 0.1 μm.

[0028] In a preferred embodiment, the distillation apparatus includes a first vacuum distillation apparatus, a condenser, and a second vacuum distillation apparatus. The material inlet of the first vacuum distillation apparatus is connected to the liquid outlet of the first adsorption apparatus, the gas outlet of the first vacuum distillation apparatus is connected to the material inlet of the condenser, the material outlet of the condenser is connected to the material inlet of the second vacuum distillation apparatus, and the gas outlet of the second vacuum distillation apparatus is connected to the material inlet of the cooling apparatus.

[0029] In a preferred embodiment, the filtration device includes a primary filter and a secondary filter. The inlet of the primary filter is connected to the material outlet of the cooling device, and the filtrate outlet of the primary filter is connected to the inlet of the secondary filter. The pore size of the primary filter is less than 100 nm, and the pore size of the secondary filter is less than 50 nm.

[0030] In a preferred embodiment, the tetraethyl orthosilicate purification system further includes a second adsorption device, the material inlet of which is connected to the material outlet of a cooling device, and the material outlet of which is connected to the material inlet of a filtration device; the second adsorption device is filled with adsorbent II containing cation exchange resin, carbon nanotubes, and zeolite.

[0031] The present invention will be described in detail below through embodiments.

[0032] In the following examples and comparative examples:

[0033] Crude tetraethyl orthosilicate was purchased from Shanghai Duyin Industrial Co., Ltd., with a purity of 99.9%.

[0034] Carboxymethyl chitosan was purchased from Aladdin, CAS number 83512-85-0, with a degree of substitution ≥80% and a molecular weight of approximately 100,000.

[0035] The zeolite balls were purchased from Beijing Guotou Shengshi Technology Co., Ltd., with a particle size of 1-3 mm.

[0036] Apricot shell activated carbon was purchased from Zhengzhou Kelin Water Purification Materials Co., Ltd. Its particle size was 10-24 mesh, moisture content ≤10%, and specific surface area was 1140 m². 2 / g.

[0037] Coconut shell activated carbon was purchased from Yixing Huahai Activated Carbon Co., Ltd. Its particle size was 8-20 mesh, moisture content ≤10%, and specific surface area was 1230 m². 2 / g.

[0038] The carbon nanotubes were octadecylamine-functionalized single-walled carbon nanotubes, purchased from Merck, model number 652482, with diameters ranging from 2 to 10 nm and lengths from 0.5 to 2 μm.

[0039] The cation exchange resin was purchased from Tianjin Yunkai Resin Technology Co., Ltd. The 001×7 strong acid cation exchange resin model was Styrene-DVB, specifically a styrene-based strong acid cation exchange resin with sulfonic acid groups as functional groups. The total exchange capacity was ≥1.8 mmol / mL (wet), and the particle size range was 0.3–1.25 mm.

[0040] Example 1

[0041] This embodiment provides a method for purifying tetraethyl orthosilicate, specifically including the following steps:

[0042] S1. Crude tetraethyl orthosilicate is subjected to primary adsorption treatment using a metal ion adsorption device packed with adsorbent I. The resulting liquid product is the tetraethyl orthosilicate adsorption solution. Adsorbent I is a mixture of chitosan, zeolite, and apricot shell activated carbon in a mass ratio of 2:2:1. The conditions for the primary adsorption treatment include a temperature of 30°C and a liquid hourly space velocity of 30 h⁻¹. -1 .

[0043] S2. The tetraethyl orthosilicate adsorbate solution is passed through a first vacuum distillation column for a first vacuum distillation at 90°C and a vacuum of 60 kPa. The distillate product is then introduced into a condenser for condensation. The condensed liquid fraction is then passed through a second vacuum distillation column for a second vacuum distillation at 70°C and a vacuum of 50 kPa. The distillate product is then introduced into a condenser for condensation to obtain the tetraethyl orthosilicate distillate. The condenser uses circulating cooling water at 25°C for condensation.

[0044] S3. The tetraethyl orthosilicate distillate is filtered sequentially through two filters. First, it is filtered through a first filter with a pore diameter of 100 nm, and then through a second filter with a pore diameter of 50 nm to remove particles with a diameter greater than 0.05 μm, thus obtaining the purified tetraethyl orthosilicate solution.

[0045] Example 2

[0046] Tetraethyl orthosilicate was purified according to the method in Example 1, except that the mass ratio of chitosan, zeolite and apricot shell activated carbon in adsorbent I was 3:2:1.

[0047] Example 3

[0048] Tetraethyl orthosilicate was purified according to the method in Example 1, except that the mass ratio of chitosan, zeolite and apricot shell activated carbon in adsorbent I was 1:1:2.

[0049] Example 4

[0050] The tetraethyl orthosilicate was purified according to the method of Example 2, except that this example further includes a step of deep adsorption treatment of the tetraethyl orthosilicate distillate with adsorbent II after step S2 and before step S3. Adsorbent II is a mixture of cation exchange resin, carbon nanotubes, and zeolite in a mass ratio of 8:0.3:1. The conditions for deep adsorption treatment include a temperature of 30°C and a liquid hourly space velocity of 30 h⁻¹. -1 .

[0051] Example 5

[0052] Ethyl orthosilicate was purified according to the method in Example 1, except that the apricot shell activated carbon in adsorbent I was replaced with coconut shell activated carbon of the same weight.

[0053] Comparative Example 1

[0054] Ethyl orthosilicate was purified according to the method in Example 1, except that the apricot shell activated carbon in adsorbent I was replaced with chitosan in the same weight proportion.

[0055] Comparative Example 2

[0056] Ethyl orthosilicate was purified according to the method in Example 2, except that the zeolite in Adsorbent I was replaced with the same amount of apricot shell activated carbon.

[0057] Comparative Example 3

[0058] Tetraethyl orthosilicate was purified according to the method in Example 3, except that chitosan in adsorbent I was replaced with apricot shell activated carbon of the same weight.

[0059] Comparative Example 4

[0060] Tetraethyl orthosilicate was purified according to the method in Example 2, except that chitosan was used to replace both the apricot shell activated carbon and zeolite in adsorbent I.

[0061] Comparative Example 5

[0062] Tetraethyl orthosilicate was purified according to the method in Example 1, except that in step S2, the temperature of the first vacuum distillation was 110°C.

[0063] Comparative Example 6

[0064] Tetraethyl orthosilicate was purified according to the method in Example 1, except that in step S3, only one filtration was performed, and the pore size of the filter was 0.5 μm. That is, the filtration removed particulate matter with a particle size of less than 0.5 μm, and high-purity tetraethyl orthosilicate was obtained.

[0065] Test case

[0066] The purity and elemental content of the tetraethyl orthosilicate obtained in the examples and comparative examples were determined by GC and ICP-MS analysis, respectively. The particle size was tested by LPC. The results are shown in Table 1.

[0067]

Claims

1. A method for purifying tetraethyl orthosilicate, characterized by, The method comprises the following steps: S1, the crude tetraethyl orthosilicate is subjected to primary adsorption treatment with adsorbent I, and then solid-liquid separation is performed, and the obtained liquid product is tetraethyl orthosilicate adsorption liquid; the adsorbent I contains chitosan, zeolite and shell activated carbon at the same time; the mass ratio of chitosan, zeolite and shell activated carbon in the adsorbent I is (1-3):(1-2):1; S2, the tetraethyl orthosilicate adsorption liquid is subjected to vacuum distillation under the condition that the temperature is 70-100℃ and the vacuum degree is ≤60kPa; the vacuum distillation comprises first vacuum distillation and second vacuum distillation performed in sequence; the temperature of the first vacuum distillation is 90-100℃ and the vacuum degree is 50-60kPa; the temperature of the second vacuum distillation is 70-90℃ and the vacuum degree is 40-50kPa; the obtained gaseous product is condensed to obtain a tetraethyl orthosilicate distillation liquid; S3, the tetraethyl orthosilicate distillation liquid is subjected to filtration to remove particulate matter with a particle size of 0.1μm or less; the filtration comprises first filtration and second filtration performed in sequence; the filter used in the first filtration has a pore size of 100nm or less; the filter used in the second filtration has a pore size of 50nm or less; and a high-purity tetraethyl orthosilicate is obtained.

2. The method for purifying tetraethyl orthosilicate according to claim 1, characterized by, In step S1, the fruit shell activated carbon has a particle size of 5-30 mesh, a moisture content of ≤10%, and a specific surface area of 1000-1300 m 2 / g.

3. The method for purifying tetraethyl orthosilicate according to claim 1, characterized by, Step S1, the conditions of the primary adsorption treatment include temperature of 20-40℃, liquid hourly space velocity of 5-50h -1 .

4. The purification method of tetraethyl orthosilicate according to any one of claims 1 to 3, characterized by, The method further comprises, after step S2 and before step S3, subjecting the tetraethyl orthosilicate distillation liquid to deep adsorption treatment with adsorbent II; the adsorbent II contains cation exchange resin, carbon nanotube and zeolite at the same time.

5. The method for purifying tetraethyl orthosilicate according to claim 4, characterized by, The mass ratio of cation exchange resin, carbon nanotube and zeolite in the adsorbent II is (5-10):(0.1-0.5):

1.

6. The method for purifying tetraethyl orthosilicate according to claim 4, wherein The cation exchange resin is a styrene-based strong acidic cation exchange resin, the functional group is sulfonic acid group, and the total exchange capacity is 1.5-3mmol / mL.

7. The method for purifying tetraethyl orthosilicate according to claim 4, wherein The diameter of the carbon nanotube is 10-30nm, and the length is 0.5-2μm.

8. The method for purifying tetraethyl orthosilicate according to claim 4, wherein The conditions of the deep adsorption treatment include a temperature of 20-40℃, a liquid hourly space velocity of 5-50h -1 .

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