CN109705153B - Purifying method of ethyl orthosilicate - Google Patents
Purifying method of ethyl orthosilicate Download PDFInfo
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- CN109705153B CN109705153B CN201910106872.9A CN201910106872A CN109705153B CN 109705153 B CN109705153 B CN 109705153B CN 201910106872 A CN201910106872 A CN 201910106872A CN 109705153 B CN109705153 B CN 109705153B
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Abstract
The invention provides a method for purifying tetraethoxysilane, which comprises the following steps: vaporizing raw material ethyl orthosilicate in a vaporizer, and sequentially passing through a first fiber bed demister, a second fiber bed demister and a third fiber bed demister on the upper part of the vaporizer to obtain ethyl orthosilicate steam; the aperture of the first fiber bed demister is 1-20 mu m; the pore diameter of the second fiber bed demister is 2-10 mu m; the pore diameter of the third fiber bed demister is 0.1-2 mu m. Compared with the prior art, the method utilizes three layers of fiber bed defoamers with different apertures to treat vaporized tetraethoxysilane and can also play a role in separating metal ions from heavy hydrocarbon of oil, so that the method can greatly reduce the content of heavy hydrocarbon and metal ions in tetraethoxysilane steam while vaporizing tetraethoxysilane, plays a role in primary purification, and ensures the quality of tetraethoxysilane steam entering a post-treatment system.
Description
Technical Field
The invention belongs to the technical field of semiconductors, and particularly relates to a method for purifying tetraethoxysilane.
Background
The method for forming an oxide layer in a semiconductor process mainly includes thermal oxidation (for a semiconductor material capable of forming a self-stabilizing oxide layer), Low Pressure Chemical Vapor Deposition (LPCVD), Plasma Enhanced Chemical Vapor Deposition (PECVD), and Atmospheric Pressure Chemical Vapor Deposition (APCVD), wherein, due to the large gas flow rate required by APCVD and the relatively large amount of particles generated by the process, most of the semiconductor processes are rarely used at present.
When Tetraethoxysilane (TEOS) is used for LPCVD, TEOS is evaporated from a liquid state to a gas state, the TEOS is decomposed at 700-750 ℃ and 300mTOR pressure and is deposited on the surface of a silicon wafer to form a silicon dioxide film, the deposition rate of the silicon dioxide film can reach 50 a/min, the thickness uniformity of the film is less than 3%, and the excellent process characteristics and the obvious characteristics of the film in the aspect of use safety gradually become a mainstream process for depositing the silicon dioxide film.
The deposition of silicon dioxide on the surface of the SiC wafer is realized by applying the tetraethyl orthosilicate (TEOS) LPCVD technology, and the defects that the SiC oxide layer is too thin and the PECVD silicon dioxide layer is too loose can be overcome to a certain extent. By adopting the reasonable application of the TEOS LPCVD technology and the high-temperature oxidation technology, the compactness of an oxide layer medium and the adhesive capacity with a SiC wafer are ensured, the electrical property and the yield of a device are improved, and the defect of long-time high-temperature oxidation of the oxide layer with a certain thickness is avoided. After the technology is adopted, the direct current yield of the SiC chip is improved, the comparative slide result of the microwave power device shows that the microwave performance is also obviously improved, the power gain is improved by about 1.5dB compared with the original technology, and the power additional efficiency is improved by nearly 10%.
But the LPCVD process requires that the tetraethoxysilane is high-purity tetraethoxysilane, wherein the content of metal ions is a key index for detecting whether a product is qualified, and the method plays a decisive role in the quality of the high-purity tetraethoxysilane. For the ultra-pure ethyl silicate, the content of each metal ion is required to be less than or equal to 0.02ppb, and the content in the raw material is dozens of times of the standard of the final product, so that each link in the production process needs to be controlled to ensure the quality of the final product.
In the production of high-purity tetraethoxysilane, the most common link is vaporization, but the existing vaporization system cannot well remove tiny droplets generated in the vaporization process of the raw material, so that the existing vaporization process cannot well remove heavy hydrocarbon and metal ions in the TEOS raw material, certain burden is caused to subsequent production, and the quality risk exists in the production of high-purity tetraethoxysilane.
Disclosure of Invention
In view of the above, the present invention provides a method for purifying tetraethoxysilane, which can remove metal ions while vaporizing.
The invention provides a method for purifying tetraethoxysilane, which comprises the following steps:
vaporizing raw material ethyl orthosilicate in a vaporizer, and sequentially passing through a first fiber bed demister, a second fiber bed demister and a third fiber bed demister on the upper part of the vaporizer to obtain ethyl orthosilicate steam; the aperture of the first fiber bed demister is 1-20 mu m; the pore diameter of the second fiber bed demister is 2-10 mu m; the pore diameter of the third fiber bed demister is 0.1-2 mu m.
Preferably, the heating medium in the vaporizer is steam; the temperature of the steam is 160-200 ℃.
Preferably, the flow rate of the raw material ethyl orthosilicate is 150-250 kg/h.
Preferably, the vaporizer is provided with a vent line.
Preferably, the opening degree of the emptying pipeline is 1-5%.
Preferably, the vaporizer is provided with a drain outlet.
Preferably, the opening degree of the sewage draining outlet is 5-10%.
Preferably, the height between the liquid level of the raw material ethyl orthosilicate and the first fiber bed demister is 2.5-3 m.
Preferably, the distance between the first fiber bed demister and the second fiber bed demister is 0.1-0.5 m.
Preferably, the distance between the second fiber bed demister and the third fiber bed demister is 0.1-0.5 m.
The invention provides a method for purifying tetraethoxysilane, which comprises the following steps: vaporizing raw material ethyl orthosilicate in a vaporizer, and sequentially passing through a first fiber bed demister, a second fiber bed demister and a third fiber bed demister on the upper part of the vaporizer to obtain ethyl orthosilicate steam; the aperture of the first fiber bed demister is 1-20 mu m; the pore diameter of the second fiber bed demister is 2-10 mu m; the pore diameter of the third fiber bed demister is 0.1-2 mu m. Compared with the prior art, the method utilizes three layers of fiber bed defoamers with different apertures to treat vaporized tetraethoxysilane, can separate liquid with the diameter of more than 0.1 mu m in gaseous tetraethoxysilane, has the defoaming efficiency of more than 95 percent, and can also play a role in separating metal ions and oil heavy hydrocarbons.
Drawings
Fig. 1 is a schematic view of a vaporizer used in the embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a method for purifying tetraethoxysilane, which comprises the following steps: vaporizing raw material ethyl orthosilicate in a vaporizer, and sequentially passing through a first fiber bed demister, a second fiber bed demister and a third fiber bed demister on the upper part of the vaporizer to obtain ethyl orthosilicate steam; the aperture of the first fiber bed demister is 1-20 mu m; the pore diameter of the second fiber bed demister is 2-10 mu m; the pore diameter of the third fiber bed demister is 0.1-2 mu m.
Wherein the raw material of the tetraethoxysilane is the tetraethoxysilane raw material well known to those skilled in the art, and the purity of the tetraethoxysilane is usually 99%, wherein the tetraethoxysilane comprises the following impurities: water, ethanol, methanol, propanol, metal ions, and the like.
Vaporizing raw material ethyl orthosilicate in a vaporizer; in order to keep the amount of the tetraethoxysilane entering and exiting the vaporizer balanced and enable continuous feeding and discharging, the flow rate of the tetraethoxysilane raw material is preferably 150-250 kg/h; the raw material ethyl orthosilicate is preferably controlled by a shielding pump to enter the vaporizer; the heating medium in the vaporizer is preferably steam; the temperature of the steam is preferably 160-200 ℃, and more preferably 170-185 ℃; the vaporizer is preferably provided with a heating medium inlet and a heating medium outlet; heating medium steam enters from a heating medium inlet, and after heat exchange, condensed hot water flows out of the vaporizer through a heating medium outlet so as to ensure heat source supply during vaporization; the heat exchanger in the vaporizer is a heat exchanger well known to those skilled in the art, and in the present invention, a tubular heat exchanger is preferred, a spiral fin tubular heat exchanger is more preferred, and a high-frequency welded spiral fin tubular heat exchanger is still more preferred. By adopting the high-frequency welded spiral fin tube type heat exchanger, the total heat exchange area is increased by 3.5 times compared with the original heat exchanger under the condition of not changing the floor space of the heat exchanger.
The upper part of the vaporizer is sequentially provided with a first fiber bed demister, a second fiber bed demister and a third fiber bed demister; a vaporization space is arranged between the heat exchanger and the first fiber bed demister; the distance between the heat exchanger and the first fiber bed demister is preferably 2.5-3 m; the first fiber bed demister is 1-20 microns in aperture and is used for catching mist particles with the diameter of 5-10 microns in vaporized ethyl orthosilicate; the thickness of the first fiber bed demister is preferably 0.1-0.15 m; primary purifying spaces of ethyl orthosilicate are respectively arranged between the first fiber bed demister and the second fiber bed demister and between the second fiber bed demister and the third fiber bed demister, and the distance between the first fiber bed demister and the second fiber bed demister is preferably 0.1-0.5 m; the distance between the second fiber bed demister and the third fiber bed demister is preferably 0.1-0.5 m; the pore diameter of the second fiber bed demister is 2-10 microns and is used for capturing atomized particles with the diameter of 2-5 microns in the vaporized tetraethoxysilane; the thickness of the second fiber bed demister is preferably 0.1-0.15 m; the third fiber bed demister has the aperture of 0.1-2 mu m and is used for catching atomized particles with the diameter of 0.1-2 mu m in vaporized tetraethoxysilane; the thickness of the third fiber bed demister is preferably 0.1-0.15 m; the ethyl orthosilicate steam outlet of the vaporizer is preferably provided with the top of the vaporizer, and vaporized ethyl orthosilicate sequentially passes through the first fiber bed demister, the second fiber bed demister and the third fiber bed demister, so that the obtained ethyl orthosilicate steam does not contain fog particles larger than 0.1 mu m, the content of heavy hydrocarbon and metal ions in gas is greatly reduced, and the quality of the ethyl orthosilicate steam entering a subsequent treatment system is ensured.
In the present invention, the vaporizer is preferably further provided with a vent pipe; the blow-down pipe is preferably located on the lower side wall of the first fiber bed demister; during the vaporization process, the opening degree of the vent pipeline is preferably 1-5%, and light components in the tetraethoxysilane steam can be partially removed.
The vaporizer is preferably also provided with a sewage draining outlet; the sewage draining outlet is preferably positioned at the bottom of the vaporizer; during the vaporization process, the opening degree of the sewage draining outlet is preferably 5-10%, so that heavy hydrocarbon and metal ions at the bottom of the vaporizer and in the cathode are discharged out of the vaporizer.
According to the invention, the vaporizer is preferably further provided with a liquid level meter for monitoring the amount of the tetraethoxysilane liquid in the vaporizer, so that the load of the vaporizer can be monitored at any time to ensure the vaporizing effect.
In the present invention, the heat exchanger, the various components, and the connecting pipes in the vaporizer are preferably made of an electropolished 316L stainless steel material.
The invention utilizes three layers of fiber bed defoamers with different apertures to treat vaporized tetraethoxysilane, can separate liquid with the diameter of more than 0.1 mu m in gaseous tetraethoxysilane, has the defoaming efficiency of more than 95 percent, and can also play a role in separating metal ions and heavy oil hydrocarbons, thereby greatly reducing the content of steam heavy hydrocarbon and metal ions of tetraethoxysilane while vaporizing tetraethoxysilane, playing a role in primary purification, and ensuring the quality of tetraethoxysilane steam entering a post-treatment system.
In order to further illustrate the present invention, the following will describe the method for purifying tetraethoxysilane provided by the present invention in detail with reference to the examples.
The reagents used in the following examples are all commercially available.
Examples
The method comprises the following steps of adopting a vaporizer shown in FIG. 1, wherein 1 is the vaporizer, 2 is an ethyl orthosilicate steam outlet, 3 is an emptying pipeline, 4 is an ethyl orthosilicate raw material inlet, 5 is a heating medium inlet, 6 is a fiber bed demister, 7 is a high-frequency welding spiral fin tube type heat exchanger, 8 is a liquid level meter port, 9 is a sewage draining port, and 10 is a heating medium outlet; the distance between the heat exchanger and the first fiber bed demister is 3 meters; the distance between the first fiber bed demister and the second fiber bed demister is 0.5 m; the distance between the second fiber bed demister and the third fiber bed demister is 0.5 m; the thickness of the first fiber bed demister, the second fiber bed demister and the third fiber bed demister is 0.15 m.
TEOS vaporization adopts steam as a heat source, the steam enters a high-frequency welding spiral finned tube heat exchanger (7) through a steam inlet (5) on the vaporizer and fully contacts with the raw material TEOS through the heat exchange tube (7), vaporization of the raw material TEOS is guaranteed, and hot water after heat exchange is discharged out of the vaporizer through a hot water outlet (10).
The side wall of the vaporizer is connected with a vent pipeline (3), and light components such as nitrogen, oxygen, methane and the like in the TEOS raw material can be vented through the vent pipeline (3). The vaporizer is provided with a liquid level meter (8) which can monitor the load of the vaporizer at any time and ensure the vaporizing effect.
(1) Raw material TEOS (wherein the composition of metal ions is shown in table 1) continuously enters the interior of the vaporizer through a TEOS raw material inlet (4) by a shield pump, the amount of the TEOS entering the vaporizer is maintained at 150-250 kg/h by the shield pump, the amount of the TEOS entering the vaporizer is kept balanced, and continuous feeding and discharging can be realized.
(2) Steam enters the high-frequency welding spiral finned tube (7) through the heating medium inlet (5), the temperature of the steam is controlled to be about 160 ℃ to 200 ℃, the raw material TEOS is fully vaporized through steam heating, and condensed hot water flows out of the vaporizer (1) through the heating medium outlet (10).
(3) The vaporized TEOS enters a three-layer fiber bed demister (6), wherein the pore diameter of the first layer of fiber bed demister is 1-20 microns, preferably 10 microns, and is used for capturing mist particles with the diameter of 5-10 microns in the TEOS; the pore diameter of the second layer fiber bed demister is 2-10 microns, preferably 2 microns, and is used for capturing fog particles with the diameter of 2-5 microns in TEOS; the pore diameter of the third layer of fiber bed demister is 0.1-2 microns, preferably 0.1 micron, and is used for capturing mist particles with the diameter of 0.1-2 microns in TEOS. Through three-layer fiber bed demister, it is guaranteed that vaporized TEOS steam entering a raw material gas outlet pipeline (2) does not contain fog particles larger than 0.1 micron, content of heavy hydrocarbon and metal ions in gas is greatly reduced, and quality of TEOS raw material gas entering a rear system is guaranteed.
(4) The opening degree of the emptying pipeline (3) is kept between 1 and 5 percent in the gasification process, and light components in the raw material gas can be partially removed; keeping the opening degree of the sewage draining outlet (9) between 5 and 10 percent to ensure that the heavy hydrocarbon and the metal ions enriched at the bottom of the vaporizer are discharged out of the vaporizer.
Three different steam temperatures are respectively selected as heat sources, the selected temperatures are respectively 160-170 ℃, 170-185 ℃ and 185-200 ℃, and the three layers of fiber defoamers are respectively a first layer of 1-20 micrometers, a second layer of 2-10 micrometers and a third layer of 0.1-2 micrometers. The analysis results are shown in table 2, and the selection of different temperatures can find that when the selected steam temperature is 160-170 ℃, although the content of metal ions in the vaporized TEOS is low, the vaporization amount is obviously insufficient, and the subsequent yield is influenced; when the steam temperature is 185-200 ℃, the metal ion content in the TEOS at the outlet is the highest. The optimized steam temperature is 170-185 ℃.
For the fiber demister, three layers of 10-micron, 2-micron and 0.1-micron fiber defoamers are independently selected for research, the research results are shown in table 3, and the analysis results show that the vaporizer has poor effect of removing small-particle fog particles and poor effect of removing metal ions by independently adopting three layers of 1-20-micron and 2-10-micron fiber defoamers; the fiber demister with the diameter of 0.1-2 microns is independently adopted, so that the resistance is large, the vaporization amount is influenced, the yield is also influenced, and the fiber demister is not independently used in practical application. Therefore, the optimal selection is to adopt a fiber demister with a first layer of 1-20 microns, a second layer of 2-10 microns and a third layer of 0.1-2 microns in industrial production.
TABLE 1 detection results of metal ions in raw material tetraethoxysilane and final product
TABLE 2 results of metal ion detection in tetraethoxysilane steam obtained under different conditions
TABLE 3 results of metal ion detection in tetraethoxysilane steam obtained under different conditions (three-layer demister adopts different specifications)
Remarking: condition a: the three layers of defoamers are all 1-20 microns.
Condition B: the three layers of defoamers are all 2-10 microns.
Condition C: the specifications of the three-layer demister are respectively 1-20 microns on the first layer, 2-10 microns on the second layer and 0.1-2 microns on the third layer.
Claims (4)
1. A method for purifying tetraethoxysilane, which is characterized by comprising the following steps:
vaporizing raw material ethyl orthosilicate in a vaporizer, and sequentially passing through a first fiber bed demister, a second fiber bed demister and a third fiber bed demister on the upper part of the vaporizer to obtain ethyl orthosilicate steam; the aperture of the first fiber bed demister is 1-20 mu m; the pore diameter of the second fiber bed demister is 2-10 mu m; the pore diameter of the third fiber bed demister is 0.1-2 mu m;
the flow rate of the raw material ethyl orthosilicate is 150-250 kg/h;
the height between the liquid level of the raw material ethyl orthosilicate and the first fiber bed demister is 2.5-3 m;
the distance between the first fiber bed demister and the second fiber bed demister is 0.1-0.5 m;
the distance between the second fiber bed demister and the third fiber bed demister is 0.1-0.5 m;
the vaporizer is provided with an emptying pipeline;
the opening degree of the emptying pipeline is 1% -5%.
2. The purification method according to claim 1, wherein the heating medium in the vaporizer is steam; the temperature of the steam is 160-200 ℃.
3. Purification method according to claim 1, wherein the vaporizer is provided with a blow off outlet.
4. The purification method according to claim 3, wherein the degree of opening of the drain outlet is 5% to 10%.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN203095627U (en) * | 2012-11-28 | 2013-07-31 | 苏州金宏气体股份有限公司 | Device for preparing ultra pure ammonia by vaporizing liquid ammonia |
| CN103772424A (en) * | 2013-12-31 | 2014-05-07 | 贵州威顿晶磷电子材料有限公司 | Preparation method of electronic grade tetraethoxysilane |
| CN108640943A (en) * | 2018-04-20 | 2018-10-12 | 居焕龙 | A method of producing ethyl orthosilicate using silica flour |
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2019
- 2019-02-02 CN CN201910106872.9A patent/CN109705153B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN203095627U (en) * | 2012-11-28 | 2013-07-31 | 苏州金宏气体股份有限公司 | Device for preparing ultra pure ammonia by vaporizing liquid ammonia |
| CN103772424A (en) * | 2013-12-31 | 2014-05-07 | 贵州威顿晶磷电子材料有限公司 | Preparation method of electronic grade tetraethoxysilane |
| CN108640943A (en) * | 2018-04-20 | 2018-10-12 | 居焕龙 | A method of producing ethyl orthosilicate using silica flour |
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