A device and process for preparing ultra-pure ammonia for semiconductors

Abstract

The present invention discloses a device and process for preparing ultra-pure ammonia for semiconductors, wherein the device comprises a vaporization unit, a pretreatment unit for desulfurization and dehydration, a light removal unit, a heavy removal unit and a post-purification unit for removing water, oxygen and metals, which are connected in sequence, and a heating system for heating the vaporization unit and the distillation system; the device can conveniently and efficiently remove impurities such as water, oxygen and metals to obtain ultra-pure ammonia; in addition, the medium of the heating system provides both a heat source and a cold source, thereby realizing continuous energy-saving production; the removal of high and low boiling point components can be recycled as industrial ammonia without exhaust gas emission.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-high purity ammonia preparation, and in particular to a device and process for preparing ultra-pure ammonia for semiconductors. Background Art

[0002] With the rapid development of semiconductor VLSI, LED lighting devices, and solar photovoltaics, the purity requirements for ultra-high purity ammonia used in the manufacturing processes in the above fields are getting higher and higher. The lower the content of impurities such as total hydrocarbons, water, and metal ions, the better. For example, in the silicon nitride film growth process, a small amount of metal particle impurities will affect the lattice length of the film, causing local interlayer lattice disorder, and at the same time affecting the film resistivity and other parameter performance. Therefore, energy-saving, efficient and stable ammonia purification technology has always been the focus of research in the field of electronic special gas purification.

[0003] Chinese patent document CN102167355A discloses a method for producing ultra-pure ammonia, which uses a three-stage distillation method to purify industrial ammonia to prepare ultra-pure ammonia. During the purification process, 50°C hot water and -5°C cold water are required. The process uses electricity or gas to heat the water, and a refrigerator is used to prepare chilled water, which is then transported to the bottom and top of each distillation tower respectively. The energy consumption is high, and the distillation method alone cannot remove moisture and metal impurities to a lower standard.

[0004] Chinese patent document CN111960436 A discloses a method for producing ultrapure ammonia, wherein the raw ammonia is vaporized in a series of evaporators and then enters a diverter tower for rectification. This process only involves simple evaporation and primary distillation, and separate heat source systems and cold source systems are required during the evaporation and distillation processes, resulting in high energy consumption. Moreover, water and metal impurities cannot be removed to a lower standard only through evaporation and primary distillation.

[0005] Chinese patent document CN109019631A discloses a production system and method for ultrapure ammonia, which utilizes a simple two-stage distillation to remove light and heavy impurities in the raw ammonia. However, the distillation system uses separate heat sources and cold sources, resulting in high energy consumption.

[0006] Chinese patent document CN112299445A discloses a method for preparing ultrapure ammonia using a packed distillation tower, which utilizes the high specific surface area of ​​the packing to improve the distillation efficiency. Its essence is still distillation, requiring a separate heat source in the bottom of the tower and a cooling source at the top of the tower, resulting in high energy consumption and poor water and metal removal effects.

[0007] Chinese patent document CN106430243A discloses an ammonia purification system which uses only a single-stage adsorption and a single-stage distillation method, and places all tanks, coils, and towers in one cylinder, which is inconvenient to maintain and the purity of the product cannot be guaranteed.

[0008] Therefore, it is necessary to design a new type of ultra-pure ammonia preparation device and process to solve the defects of the above-mentioned prior art, such as difficulty in removing impurities, low efficiency, high energy consumption, and lack of purity guarantee. Summary of the invention

[0009] The present invention provides an apparatus and process for preparing ultrapure ammonia for semiconductors, so as to solve at least one of the many defects existing in the above-mentioned prior art.

[0010] To achieve the above object, the scheme of the present invention is as follows:

[0011] A device for preparing ultrapure ammonia for semiconductor use, comprising a vaporization unit, a pretreatment unit, a distillation system and a post-purification unit connected in sequence, and a heating system for heating the vaporization unit and the distillation system;

[0012] The vaporization unit is used to vaporize industrial liquid ammonia;

[0013] The pretreatment unit is used for desulfurization and moisture removal;

[0014] The distillation system is composed of a light removal unit and a heavy removal unit connected in series, each of which comprises at least one distillation tower, and the ammonia gas is sequentially stripped of light components and heavy components through the distillation system;

[0015] Post-purification units are used to remove moisture, oxygen and metals.

[0016] Furthermore, the heating system includes a first compressor and a second compressor, which are respectively used to generate heating steam; the vaporization unit includes a vaporizer; the light removal unit includes a first distillation tower, and the heavy removal unit includes a second distillation tower; the first compressor is connected to the vaporizer and the first distillation tower; the second compressor is connected to the second distillation tower.

[0017] Preferably, the light removal unit includes a first condenser for condensing at the top of the first distillation tower; the heating system includes a first liquid buffer tank and a first gas buffer tank; the output end of the first compressor is connected to the vaporizer and the first distillation tower, and the loop pipeline is then connected to the first liquid buffer tank, the first condenser and the first gas buffer tank in sequence, and the first gas buffer tank is connected to the input end of the first compressor; the heating steam enters the first liquid buffer tank after condensation through the vaporizer and the first distillation tower, exchanges heat with the first condenser, and then vaporizes and returns to the first compressor for compression.

[0018] Preferably, the deweighting unit includes a second condenser for condensing at the top of the second distillation tower; the heating system includes a second liquid buffer tank and a second gas buffer tank; the output end of the second compressor is connected to the second distillation tower, the second liquid buffer tank, the second condenser and the second gas buffer tank in sequence, and the second gas buffer tank is connected to the input end of the second compressor; the heating steam enters the second liquid buffer tank after condensation in the second distillation tower, vaporizes after heat exchange with the second condenser, and then returns to the second compressor for compression.

[0019] Furthermore, the pretreatment unit comprises a desulfurizer and an adsorber which are connected in sequence; the desulfurizer is filled with activated carbon, and the adsorber is filled with a molecular sieve modified with sodium hydroxide and ferric nitrate.

[0020] Furthermore, the purification unit comprises a first purifier and a second purifier which are connected in sequence; the first purifier is filled with γ-Al2O3, and the second purifier is filled with alkali metal styrene cation exchange lipid.

[0021] The present invention also provides a process for preparing ultrapure ammonia for semiconductors, which is characterized by comprising the following steps:

[0022] S1. After industrial liquid ammonia is vaporized, it is pretreated to remove sulfur and moisture in turn;

[0023] S2. Remove light components and heavy components in turn through multiple distillations;

[0024] S3. After distillation, water, oxygen and metal are removed from the ammonia to obtain ultra-pure ammonia.

[0025] Furthermore, in step S1, the vaporization pressure is 0.3-0.8 MPa.

[0026] Furthermore, the light components and heavy components removed in step S2 are both produced as industrial crude products.

[0027] Furthermore, in step S2, the distillation operating pressure for removing light components is 0.2-0.7 MPa, the tower top temperature is -19°C to 14°C, and the tower bottom temperature is -17°C to 16°C; the distillation operating pressure for removing heavy components is 0.15-0.5 MPa, the tower top temperature is -25°C to 2°C, and the tower bottom temperature is -23°C to 4.5°C.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The present invention adopts a comprehensive method of pre-desulfurization and dehydration combined with secondary distillation to sequentially remove light and heavy impurities and post-treatment to obtain a stable high-purity ammonia product; metal oxide compound dehydration, metal cation exchange resin, and metal oxide compound purifier remove water to below 10 ppb, solving the problem that water is difficult to completely separate in the distillation operation; metal cation exchange resin can efficiently remove metal impurities, solving the inefficient method of simply distilling to remove metal impurities in the distillation operation;

[0030] 2. The present invention adopts heat pump distillation technology to provide both heat source and cold source in the distillation process, which solves the problem of needing heating and condensation in the distillation process. At the same time, the high efficiency of compression heat exchange is utilized to greatly reduce the energy consumption of the whole process, saving about 75% of energy compared with traditional distillation;

[0031] 3. The purification method provided by the present invention can use industrial ammonia products as raw materials, which are low-priced, widely available, and have few limitations on industrial application; the ammonia containing high-boiling and low-boiling substances discharged from the system can be recycled as industrial ammonia, and there is no waste gas emission;

[0032] 4. The device provided by the present invention can realize continuous, stable and fully automatic control, ensuring the stability of product quality and the consistency of products from batch to batch, and the product recovery rate is relatively high; the process technology is a continuous operation process, and each purifier is a fully automatic dual-system structure, which can automatically regenerate and automatically switch. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is an overall schematic diagram of the device for preparing ultra-pure ammonia for semiconductors according to the present invention.

[0034] Marked in the figure are: 1. Vaporizer; 2. Desulfurizer; 3. Adsorber; 4. First condenser; 5. First distillation tower; 6. Second distillation tower; 7. First purifier; 8. Second purifier; 9. First compressor; 10. First gas buffer tank; 11. First liquid buffer tank; 12. Second compressor; 13. Second gas buffer tank; 14. Second liquid buffer tank; 61. Second condenser. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] It should be understood that the orientations or positional relationships indicated by terms such as “upper”, “lower”, “top”, “bottom”, “inside” and “outside” are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0037] like Figure 1 As shown, the present invention provides a device for preparing ultra-pure ammonia for semiconductors, comprising a vaporizer 1, a desulfurizer 2, and an adsorber 3 connected in sequence by pipelines, wherein the desulfurizer 2 is filled with activated carbon, and the adsorber 3 is filled with a 5A molecular sieve modified with sodium hydroxide and ferric nitrate; sulfur and moisture in industrial ammonia are removed in advance respectively, the output pipeline of the adsorber 3 is further connected to the feed port of the first distillation tower 5, the first distillation tower 5 is provided with a discharge port at the bottom thereof to be connected to the feed port of the second distillation tower 6, the discharge port at the top of the second distillation tower 6 is connected in sequence to the first purifier 7 and the second purifier 8 to transport the ultra-pure ammonia product, and the heavy component is extracted from the bottom of the second distillation tower 6 to be transported to an industrial ammonia tank; the first purifier 7 is filled with metal oxides, such as γ-Al2O3, which can further remove moisture and oxygen in ammonia; the second purifier 8 is filled with metal cation exchange resins, such as alkali metal (sodium / potassium) styrene cation exchange resins, which can further remove metal ions in ammonia, and the material after the metal ions are removed enters the product analysis and filling system as the final ultra-high purity ammonia product for semiconductors.

[0038] The above-mentioned device also includes a heating system and a cooling system. The top of the first distillation tower 5 is connected to the first condenser 4. The material output end of the first condenser 4 is further connected to the first distillation tower 5 and the crude product extraction pipeline. After the material produced at the top of the tower is condensed and cooled by the first condenser 4, part of it is extracted as a crude ammonia product, and the other part re-enters the first distillation tower 5 as a top reflux; the first compressor 9 is filled with high-temperature heating steam, and the output end pipeline of the first compressor 9 is respectively connected to the vaporizer 1 and the shell side of the kettle reboiler of the first distillation tower 5 for heating. The return water generated after the heat exchange is connected to the first liquid buffer tank 11 through the pipeline; the bottom of the first liquid buffer tank 11 is connected to the first condenser 4, and the material in the first condenser 4 is heat exchanged. The loop is connected to the first gas buffer tank 10. The return water returns to the gaseous state after heat exchange in the first condenser 4 and enters the first gas buffer tank 10. The top of the first gas buffer tank 10 is then connected to the input end of the first compressor 9 to compress the gas. A second condenser 61 is provided at the top of the second distillation tower 6, which is an integrated condenser. The second compressor 12 is filled with high-temperature heating steam. The output end pipeline of the second compressor 12 is connected to the shell side of the reboiler of the kettle of the second distillation tower 6, and the return water is connected to the second liquid buffer tank 14. The bottom of the second liquid buffer tank 14 is connected to the second condenser 61 to cool the top material and absorb the released heat to vaporize. The second condenser 61 loop pipeline is connected to the second gas buffer tank 13, and the top of the second gas buffer tank 13 is further connected to the input end of the second compressor 12 to compress the gas.

[0039] In the present invention, the medium used in the above-mentioned heating system and cooling system can be ammonia, chlorofluorocarbons or other equivalent conventional low-temperature refrigerants, and its compression pressure and expansion pressure can match the use temperature. The description of "return water" is the state of the medium output after heat exchange, and it is not water in the absolute sense.

[0040] In the above-mentioned device described in the present invention, the materials filled in each purifier (desulfurizer 2, adsorber 3, first purifier 7, second purifier 8, etc.) are all commercially available products, and each purifier is set as a fully automatic dual system, which can be automatically regenerated and automatically switched, and can realize continuous automatic operation of the device.

[0041] The present invention also proposes an ultrapure ammonia extraction process based on the above device, which is specifically as follows:

[0042] The industrial product liquid ammonia is vaporized after heat exchange in the vaporizer 1, and the pressure is 0.3-0.8MPa. The ammonia gas is desulfurized by the desulfurizer 2, and then further dehydrated by the adsorber 3 before entering the feed port of the first distillation tower 5. The operating pressure of the distillation tower is 0.2-0.7MPa (A), the tower top temperature is -19℃~14℃, and the tower bottom temperature is -17℃~16℃; the light components extracted from the tower top are condensed by the first condenser 4 and partially refluxed into the tower, and the uncondensed parts are extracted as crude products; the heavy components in the bottom of the first distillation tower 5 enter the second distillation tower 6 for further distillation and purification, and the operating pressure is 0.15-0.5MPa (A), the tower top temperature is -25℃~2℃, and the tower bottom temperature is -23℃~4.5℃. The top component of the second distillation tower 6 is passed through the first purifier 7 to reduce the moisture and oxygen contents to below 10 ppb, and then passed through the second purifier 8 to remove the metal ion content to below 10 ppt to obtain an ultra-high purity liquid ammonia product.

[0043] In the above process, the first compressor 9 outputs high-temperature gas to heat the vaporizer 1 and the shell side of the reboiler of the first distillation tower 5, and then condenses, and then after throttling expansion, it becomes liquid and enters the first condenser 4 to absorb the heat released by the material and then becomes gas; similarly, the second compressor 12 outputs high-temperature gas to heat the shell side of the reboiler of the second distillation tower 6, and then condenses, and then after throttling expansion, it condenses on the top of the second distillation tower 6 to absorb the heat released by the material and then becomes gas.

[0044] The above process enables the heat transfer medium to provide both a heat source and a cold source, solving the problem of requiring steam (hot water) and low-temperature chilled water during the distillation process. At the same time, the high efficiency of compression heat exchange is utilized to greatly reduce the energy consumption of the entire process, saving about 75% of energy consumption compared to traditional distillation.

[0045] In the above process, the desulfurization treatment and dehydration pretreatment before distillation can reduce the boiling range of the material, which is helpful to improve the efficiency and purity of distillation purification. The two distillation processes have different operating conditions to respectively extract light components and heavy components, thereby improving the overall purity. Finally, after dehydration, deoxygenation and removal of heavy metal ions, a liquid ammonia product of 99.99999% (above 7N grade) is finally obtained.

[0046] The following is a comparative example for verifying the above process, which is used to verify the necessity of each purification unit in the above process of the present invention and the criticality of the sequence design.

[0047] Comparative Example 1

[0048] The second distillation tower 6 is not used in the purification process, and the product extracted from the bottom of the first distillation tower 5 is directly purified by the first purifier 7 and the second purifier 8, and the other parts remain unchanged. The purity of the final product is 99.99451%.

[0049] Comparative Example 2

[0050] During the purification process, the product extracted from the top of the second distillation tower 6 is purified by the second purifier 8 and the first purifier 7, and the other conditions remain unchanged. The purity of the final product is 99.99983%.

[0051] Comparative Example 3

[0052] The purification process does not use the desulfurizer 2 and the adsorber 3 for pretreatment, and the crude ammonia is directly vaporized and then distilled twice, and the other conditions remain unchanged. The final product has a purity of 99.99875%.

[0053] It is not difficult to see that in Comparative Example 1, only one distillation was performed to remove light components, the order of purification treatment was changed in Comparative Example 2, and the purity of the finished product in Comparative Example 3 did not reach the 7N level without pretreatment. It can be seen that Comparative Example 1 failed to remove heavy impurities by only one distillation and purification, affecting the final purity; the order of removing water, oxygen, and metal ions in Comparative Example 2 may be affected by the purification filling material, resulting in the mixing of impurities and affecting the final purity; Comparative Example 3 did not pretreat to remove water and sulfur impurities, and the azeotropic products produced were difficult to remove even after secondary distillation and subsequent purification, thus affecting the final purity.

[0054] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A device for preparing ultrapure ammonia for semiconductors, characterized in that: It includes a vaporization unit, a pretreatment unit, a distillation system and a post-purification unit which are connected in sequence, and a heating system for heating the vaporization unit and the distillation system; The vaporization unit is used to vaporize industrial liquid ammonia; The pretreatment unit is used for desulfurization and moisture removal; The distillation system is composed of a light removal unit and a heavy removal unit connected in series, each of which comprises at least one distillation tower, and the ammonia gas is sequentially stripped of light components and heavy components through the distillation system; The post-purification unit is used to remove moisture, oxygen and metals; The pretreatment unit comprises a desulfurizer (2) and an adsorber (3) which are connected in sequence; the desulfurizer (2) is filled with activated carbon, and the adsorber (3) is filled with a molecular sieve modified with sodium hydroxide and ferric nitrate; The purification unit comprises a first purifier (7) and a second purifier (8) which are connected in sequence; the first purifier (7) is filled with γ-Al2O3, and the second purifier (8) is filled with alkali metal styrene cation exchange lipid.

2. The device according to claim 1, characterized in that The heating system comprises a first compressor (9) and a second compressor (12), each of which is used to generate heating steam; the vaporization unit comprises a vaporizer (1); the light removal unit comprises a first distillation tower (5), and the heavy removal unit comprises a second distillation tower (6); the first compressor (9) is connected to the vaporizer (1) and the first distillation tower (5); and the second compressor (12) is connected to the second distillation tower (6).

3. The device according to claim 2, characterized in that The light removal unit comprises a first condenser (4) for condensing at the top of a first distillation tower (5); the heating system comprises a first liquid buffer tank (11) and a first gas buffer tank (10); the output end of the first compressor (9) is connected to the vaporizer (1) and the first distillation tower (5); the loop pipeline is then connected to the first liquid buffer tank (11), the first condenser (4) and the first gas buffer tank (10) in sequence; the first gas buffer tank (10) is connected to the input end of the first compressor (9); the heating steam is condensed by the vaporizer (1) and the first distillation tower (5) and then enters the first liquid buffer tank (11), exchanges heat with the first condenser (4), and then vaporizes and returns to the first compressor (9) for compression.

4. The device according to claim 2, characterized in that The de-weighting unit comprises a second condenser (61) for condensing at the top of a second distillation tower (6); the heating system comprises a second liquid buffer tank (14) and a second gas buffer tank (13); the output end of the second compressor (12) is connected to the second distillation tower (6), the second liquid buffer tank (14), the second condenser (61) and the second gas buffer tank (13) in sequence, and the second gas buffer tank (13) is connected to the input end of the second compressor (12); the heating steam is condensed in the second distillation tower (6) and then enters the second liquid buffer tank (14), exchanges heat with the second condenser (61), and then vaporizes and returns to the second compressor (12) for compression.

5. A process for preparing ultrapure ammonia for semiconductor use, characterized in that: The steps include: S1. After industrial liquid ammonia is vaporized, it is pretreated to remove sulfur and moisture in turn; S2. Remove light components and heavy components in turn through multiple distillations; S3. The ammonia after distillation is further subjected to the removal of water, oxygen and metals to obtain ultra-pure ammonia; In step S1, the desulfurization process uses activated carbon, and the dehydration process uses sodium hydroxide and ferric nitrate modified molecular sieves; In step S3, γ-Al2O3 is used in the dehydration process, and alkali metal styrene-based cation exchange lipid is used in the deoxygenation process.

6. The process according to claim 5, characterized in that The vaporization pressure in step S1 is 0.3-0.8 MPa.

7. The process according to claim 5, characterized in that The light components and heavy components removed in step S2 are both produced as industrial crude products.

8. The process according to claim 5, characterized in that In the step S2, the distillation operation pressure for removing the light components is 0.2-0.7 MPa, the tower top temperature is -19°C~14°C, and the tower bottom temperature is -17°C~16°C; the distillation operation pressure for removing the heavy components is 0.15-0.5 MPa, the tower top temperature is -25°C~2°C, and the tower bottom temperature is -23°C~4.5°C.

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