Tetraethyl orthosilicate purification process for chip CVD deposition

Abstract

This invention relates to a purification process for tetraethyl orthosilicate (TEO) used in CVD deposition on semiconductor chips, belonging to the field of silane coupling agent preparation. The steps include using industrial-grade TEO as raw material and anhydrous ethanol as solvent, employing an ultra-low temperature recrystallization process to remove organic impurities through multiple recrystallizations at low temperatures; and using a combination of ethylenediaminetetraacetic acid (EDTA) complexing agent and a quartz degravation distillation apparatus to remove metal ions. The preparation method provided by this invention is simple to implement, highly efficient, energy-efficient, and easily industrialized.

Description

Technical Field

[0001] This invention relates to a process for purifying tetraethyl orthosilicate for CVD deposition on chips, belonging to the field of silane coupling agent preparation. Background Technology

[0002] Electronic-grade tetraethyl orthosilicate (TEO) is a microelectronic chemical used in the fabrication of epitaxial materials for integrated circuits. It is an important precursor material in the emerging semiconductor industry, and its preparation requires extremely high control over the content of organic and metal ion impurities. Industrial-grade TEO typically has an organic purity of 99.0%–99.5%, still containing more than 0.5% of various organic impurities, and also contains high levels of dozens of other metal ions. Among these impurities, metal ions are electroactive impurities that reduce the insulation performance of silicon dioxide thin films in semiconductor devices, while non-electroactive impurities such as moisture and organic matter affect the uniformity and smoothness of the deposited film.

[0003] Patent application CN113292588A discloses a method for preparing electronic-grade tetraethyl orthosilicate with a purity greater than 99.999999% by adsorption treatment followed by four consecutive distillations. Patent application CN109912636A discloses a method for preparing electronic-grade tetraethyl orthosilicate with a purity of 99.9999999% by removing light component impurities through distillation, removing chlorides through alkaline adsorption, removing metal ions through spherical activated carbon and cation exchange resin, and finally removing remaining impurities through heavy distillation.

[0004] Based on the above-disclosed patents, the preparation of electronic-grade tetraethyl orthosilicate mainly utilizes adsorption, complexation, multiple distillation, and sub-boiling distillation processes. While these processes can achieve impurity removal, they also have significant shortcomings in the purification process. The method disclosed in patent application CN113292588A requires four consecutive distillations to obtain electronic-grade tetraethyl orthosilicate, resulting in low impurity removal efficiency and high energy consumption. The method disclosed in patent application CN109912636A requires high theoretical plate numbers and reflux ratios for both light and heavy distillation to achieve impurity removal, placing high demands on equipment, resulting in high energy consumption and low efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a tetraethyl orthosilicate purification process for chip CVD deposition that simultaneously meets various requirements such as purity, moisture, and particulate matter, with significant separation effect, high efficiency, low cost, and easy industrialization.

[0006] The technical solution of this invention is:

[0007] A process for purifying tetraethyl orthosilicate for CVD deposition on chips, characterized by comprising the following steps:

[0008] 1) In an environment of ultrapure nitrogen (nitrogen content 99.9999%), add industrial-grade tetraethyl orthosilicate and anhydrous ethanol to a PTFE container equipped with a thermometer, PTFE tubing, and mechanical stirrer. Turn on the mechanical stirrer and lower the temperature of the container system to -80 to -110°C using liquid nitrogen. Crystallize the tetraethyl orthosilicate at -80 to -110°C. After 0 to 5 hours, filter at low temperature to remove organic impurities. Repeat the above steps to perform the recrystallization and impurity removal process 1 to 5 times.

[0009] 2) Under ultrapure nitrogen environment, the filtered tetraethyl orthosilicate is introduced into a distillation column to separate the ethanol solvent by distillation;

[0010] 3) Under ultrapure nitrogen atmosphere, add ethylenediaminetetraacetic acid (EDTA) complexing agent to tetraethyl orthosilicate and stir at room temperature for 0-5 hours;

[0011] 4) Stop stirring and filter the tetraethyl orthosilicate through a polytetrafluoroethylene filter (hydrophilic polytetrafluoroethylene filter membrane, pore size 0.1μm) to remove fine particulate matter and complexed metal ions;

[0012] 5) Under ultrapure nitrogen atmosphere, the filtered tetraethyl orthosilicate is introduced into a quartz degravation distillation column, and electronic grade tetraethyl orthosilicate is obtained after distillation and separation.

[0013] In step 1), the organic purity of industrial-grade tetraethyl orthosilicate is ≥99.5%, and the purity of anhydrous ethanol is ≥99.9%.

[0014] In step 1), the amount of anhydrous ethanol added is 10-200% of the mass of tetraethyl orthosilicate, preferably 10-100% of the mass of tetraethyl orthosilicate.

[0015] In step 2), the temperature of the system to be de-ethyl orthosilicate in the distillation column is 50-90°C, the vacuum degree is -0.05--0.1 MPa, and the reflux ratio is 0-10, preferably 1-3.

[0016] In step 3), the amount of ethylenediaminetetraacetic acid (EDTA) complexing agent added is 0-10% of the mass of tetraethyl orthosilicate, preferably 0.5-5% of the mass of tetraethyl orthosilicate.

[0017] In step 5), the quartz de-heavy distillation system is used to remove heavy orthosilicate. The temperature of the system is 100-120°C, the vacuum is -0.05--0.1 MPa, the theoretical plate number is 20-90, and the reflux ratio is 0-50, preferably 5-20.

[0018] After steps 1) and 2) are completed, the organic content of the materials obtained in steps 1) and 2) is detected by a GC detector.

[0019] After step 5) is completed, the organic content of the material obtained in step 5) is detected by a GC analyzer; the metal ion impurity content is detected by an ICP-MS analyzer; the moisture content is detected by a Karl Fischer moisture analyzer; and the chloride content is detected by an ion chromatograph.

[0020] The advantages of this invention compared to the prior art are:

[0021] 1. The ultra-low temperature recrystallization process is simpler, more efficient, and less energy-consuming than the multiple distillation methods commonly used in existing technologies, making it easier to industrialize organic impurities.

[0022] 2. The method of using ethylenediaminetetraacetic acid (EDTA) complexing agent and quartz degravation distillation device can remove metal ions simply and efficiently.

[0023] 3. The obtained electronic-grade tetraethyl orthosilicate has an organic purity of up to 99.99995%, an inorganic purity of up to 99.9999998%, a moisture content of less than 5 ppm, and a chloride content of less than 50 ppb, which fully meets the application requirements of semiconductor chips. Detailed Implementation

[0024] Example 1

[0025] Under ultrapure nitrogen atmosphere, 2000g of industrial-grade tetraethyl orthosilicate and 640g of anhydrous ethanol were added to a 5000ml four-necked PTFE flask equipped with a thermometer, PTFE tubing, and mechanical stirrer. After addition, the mechanical stirrer was turned on at 240 rpm, and the temperature of the PTFE flask was lowered to -90°C using liquid nitrogen. This temperature was maintained for 1 hour to allow the tetraethyl orthosilicate to crystallize. After crystallization, stirring was stopped, and the mixture was filtered at -90°C to remove uncrystallized ethanol and organic impurities. Tetraethyl orthosilicate (melting point: -77°C) crystallized at -90°C, while ethanol (melting point: -114°C) did not crystallize. Organic impurities, due to their low concentration in the system, were difficult to combine and crystallize. Therefore, the method of crystallizing tetraethyl orthosilicate at -90°C followed by filtration effectively removed organic impurities. The above process was repeated once, with the ultra-low temperature recrystallization impurity removal process repeated once.

[0026] Since a small amount of ethanol is trapped during the crystallization of tetraethyl orthosilicate, it cannot be completely removed by filtration. Under ultrapure nitrogen, the mixture of tetraethyl orthosilicate with ethanol solvent after the organic impurities have been removed is introduced into a distillation column to separate the ethanol solvent by distillation. In the distillation column, the temperature of the system to be de-electroethyl orthosilicate is 75°C, the vacuum degree is -0.08MPa, and the reflux ratio is 2.

[0027] Add 50g of ethylenediaminetetraacetic acid complexing agent to tetraethyl orthosilicate that has been purified of organic impurities. Stir at 100r / min for 1 hour at room temperature, and then filter through a polytetrafluoroethylene filter with a pore size of 0.1μm to remove particulate matter.

[0028] The filtered tetraethyl orthosilicate was introduced into a quartz-based de-distillation apparatus for distillation separation to obtain electronic-grade tetraethyl orthosilicate. In the quartz-based de-distillation system, the temperature of the tetraethyl orthosilicate to be de-distilled was 110℃, the vacuum degree was -0.08 MPa, the theoretical plate number was 75, and the reflux ratio was 15. The obtained electronic-grade tetraethyl orthosilicate had an organic purity (GC) of 99.99992%, an inorganic purity (ICP-MS) of 99.9999996%, a water content of 4 ppm, and a chloride content of 33 ppb.

[0029] Example 2

[0030] Under ultrapure nitrogen atmosphere, 2000g of industrial-grade tetraethyl orthosilicate and 1000g of anhydrous ethanol were added to a 5000ml four-necked PTFE flask equipped with a thermometer, PTFE tubing, and mechanical stirrer. The mechanical stirrer was turned on and stirred at 240 rpm. Subsequently, the temperature of the flask system was lowered to -100℃ using liquid nitrogen and held at this temperature for 1 hour to allow the tetraethyl orthosilicate in the system to crystallize. After crystallization, stirring was stopped, and the system was filtered at -90℃ to remove uncrystallized ethanol and organic impurities. The above steps were repeated twice for ultra-low temperature recrystallization and impurity removal.

[0031] Under ultrapure nitrogen atmosphere, a mixture of tetraethyl orthosilicate (after organic impurities have been removed) and ethanol solvent is introduced into a distillation system to separate the ethanol solvent by distillation. In the distillation column, the temperature of the system to be de-electrosilicate is 75°C, the vacuum degree is -0.08 MPa, and the reflux ratio is 2.

[0032] Add 50g of ethylenediaminetetraacetic acid complexing agent to tetraethyl orthosilicate that has been purified of organic impurities. Stir at 100r / min for 2 hours at room temperature, and then filter through a polytetrafluoroethylene filter with a pore size of 0.1μm to remove particulate matter.

[0033] The filtered tetraethyl orthosilicate was introduced into a quartz-based heavy distillation apparatus for separation, yielding electronic-grade tetraethyl orthosilicate. The heavy distillation system was maintained at 110°C, a vacuum of -0.08 MPa, 75 theoretical plates, and a reflux ratio of 15. The resulting electronic-grade tetraethyl orthosilicate had an organic purity (GC) of 99.99995%, an inorganic purity (ICP-MS) of 99.9999998%, a water content of 3 ppm, and a chloride content of 30 ppb.

[0034] Example 3

[0035] Under ultrapure nitrogen atmosphere, 2000g of industrial-grade tetraethyl orthosilicate and 1500g of anhydrous ethanol were added to a 5000ml four-necked PTFE flask equipped with a thermometer, PTFE tubing, and mechanical stirrer. The mechanical stirrer was turned on and stirred at 240 rpm. The temperature of the flask system was then lowered to -100℃ using liquid nitrogen and maintained at this temperature for 3 hours to allow the tetraethyl orthosilicate to crystallize. Stirring was then stopped, and the system was filtered at -90℃ to remove uncrystallized ethanol and organic impurities. The above steps were repeated once for ultra-low temperature recrystallization and impurity removal.

[0036] Under ultrapure nitrogen atmosphere, a mixture of tetraethyl orthosilicate (after organic impurities have been removed) and ethanol solvent is introduced into a distillation column, where the ethanol solvent is separated by distillation. In the distillation column, the system to be de-treated with tetraethyl orthosilicate is at a temperature of 75°C, a vacuum of -0.08 MPa, and a reflux ratio of 2.

[0037] Add 50g of ethylenediaminetetraacetic acid complexing agent to tetraethyl orthosilicate that has been purified of organic impurities. Stir at 100r / min for 1 hour at room temperature, and then filter through a polytetrafluoroethylene filter with a pore size of 0.1μm to remove particulate matter.

[0038] The filtered tetraethyl orthosilicate was introduced into a quartz de-distillation apparatus. After distillation, electronic-grade tetraethyl orthosilicate was obtained. In the quartz de-distillation system, the temperature of the tetraethyl orthosilicate to be de-distilled was 110℃, the vacuum degree was -0.08 MPa, the theoretical plate number was 75, and the reflux ratio was 15. The obtained electronic-grade tetraethyl orthosilicate had an organic purity (GC) of 99.99993%, an inorganic purity (ICP-MS) of 99.9999994%, a water content of 3 ppm, and a chloride content of 29 ppb.

Claims

1. A process for purifying tetraethyl orthosilicate for CVD deposition on semiconductor chips, characterized in that: The steps are as follows: 1) In an ultrapure nitrogen atmosphere, add industrial grade tetraethyl orthosilicate and anhydrous ethanol to a PTFE container equipped with a thermometer, PTFE tubing, and mechanical stirrer. Turn on the mechanical stirrer and use liquid nitrogen to lower the temperature of the container system to -80~-110℃. Allow the tetraethyl orthosilicate to crystallize at -80~-110℃. After 0~5 hours, filter at low temperature to remove organic impurities. Repeat the above steps to perform the recrystallization and impurity removal process 1 to 5 times. 2) Under ultrapure nitrogen environment, the filtered tetraethyl orthosilicate is introduced into the distillation system to separate the ethanol solvent by distillation; 3) Under ultrapure nitrogen atmosphere, add ethylenediaminetetraacetic acid complexing agent to tetraethyl orthosilicate and stir at room temperature for 0-5 hours; 4) Stop stirring and filter the tetraethyl orthosilicate through a polytetrafluoroethylene filter to remove fine particulate matter and complexed metal ions; 5) Under ultrapure nitrogen atmosphere, the filtered tetraethyl orthosilicate is introduced into a quartz degravation distillation column, and electronic grade tetraethyl orthosilicate is obtained after distillation and separation. In step 1), the amount of anhydrous ethanol added is 10-200% of the mass of tetraethyl orthosilicate. In step 2), the temperature of the system to be de-ethyl orthosilicate in the distillation column is 50~90℃, the vacuum degree is -0.05~-0.1MPa, and the reflux ratio is 0~10. In step 5), the temperature of the quartz de-heavy distillation system to be de-heavy tetraethyl orthosilicate is 100~120℃, the vacuum degree is -0.05~-0.1MPa, and the reflux ratio is 0~50. In step 1), the organic purity of industrial grade tetraethyl orthosilicate is ≥99.5%, and the purity of anhydrous ethanol is ≥99.9%.

2. The tetraethyl orthosilicate purification process for chip CVD deposition according to claim 1, characterized in that: In step 3), the amount of ethylenediaminetetraacetic acid complexing agent added is 0.5-10% of the mass of tetraethyl orthosilicate.

3. The tetraethyl orthosilicate purification process for chip CVD deposition according to claim 1, characterized in that: In step 3), the amount of ethylenediaminetetraacetic acid complexing agent added is 0.5-5% of the mass of tetraethyl orthosilicate.

4. The tetraethyl orthosilicate purification process for chip CVD deposition according to claim 1, characterized in that: After steps 1) and 2) are completed, the organic content of the materials obtained in steps 1) and 2) is detected by a GC detector.

5. The tetraethyl orthosilicate purification process for chip CVD deposition according to claim 1, characterized in that: After step 5) is completed, the organic content of the obtained product is detected by GC analyzer, the metal ion impurity content is detected by ICP-MS analyzer, the moisture content is detected by Karl Fischer moisture analyzer, and the chloride content is detected by ion chromatograph.