Patent Application
20090068083
The present invention relates to processes for synthesizing NF3, which is useful for interior washing of semiconductor production apparatuses such as CVD apparatuses, and halogenated nitrogens, which are useful as a raw material for synthesizing difluoroaminoalkanes from lower normal alkyl mercury compounds.
Hitherto, there has been a report by A. V. PANKRATOV et al. that NF2Cl and NFCl2 are produced from NH4Cl and F2, as a process for producing halogenated nitrogens (Non-patent Publication 1). With respect to the synthesis of NF2Cl and NF3 using interhalogen, there are a process in which solid NH4F is reacted with ClF3 diluted to 35% or lower by N2 and the like at from −40° C. to room temperature (Patent Publication 1), and a process in which solid NH4F or solid NH4HF2 is dispersed in a fluorocarbon oil, and it is reacted with ClF3 in a temperature range of 50-75° C. (Patent Publication 2), and the like. The former process is a solid-gas reaction, and has a problem that the control of the reaction and the continuous synthesis are difficult. The latter process had a danger that the fluorocarbon oil reacts with ClF3 by the generation of a local reaction heat to cause explosion and had a fear of the contamination of the produced NF2Cl with the carbon oil mist and vapor to lower purity. It is known that NF2Cl is produced by a reaction of HNF2 with ClF3 and that NF3 is produced by a reaction of ClF5 with HNF2 (Non-patent Publication 2). These processes have a problem that the synthesis of HNF2 itself is difficult.
Furthermore, halogenated nitrogen compounds, such as NFCl, NF2Br and NFBr2, are also known (Non-patent Publication 3, Non-patent Publication 4, and Non-patent Publication 5).
As processes for producing NF3, which is one of halogenated nitrogens, there are known (a) a process in which gaseous F2 is blown into a HF-adduct of a liquid acidic ammonium fluoride or ammonium complex compound (Patent Publication 3 and Patent Publication 4), (b) a process by electrolysis of a HF solution of acidic ammonium fluoride (Patent Publication 5), (c) a process in which gaseous NH3 is reacted with gaseous F2 (Patent Publication 6), (d) a process by glow discharge of a gaseous mixture of N2 and F2 (Patent Publication 7), (e) a process by a gas-phase reaction between FN3 and NOF or ClF3 (Patent Publication 8), (D a process by a reaction between solid (NH4)3AlF6 and F2 (Patent Publication 9).
In the process (a), however, it is necessary to conduct a liquid stirring with a high-energy power in order to increase the efficiency of the contact between gaseous F2 and the liquid. Thus, there has been a problem that the structure of the reactor becomes mechanically complicated and that a large energy is necessary. Furthermore, there has been a problem that the generation of reaction heat is great, that the size increase of the apparatus is difficult, and that the temperature range for making the synthesis possible is narrow. The electrolysis process (b) has a problem that a large amount of electric energy is necessary and that a danger of explosion exists due to the generation of sludge through dissolution of Ni electrode and due to the mixing of H2 and NF3. The process (c) is accompanied with a danger of explosion. The process (d) is not a preferable process, since yield is low. The processes (e) and (f) are cumbersome and difficult, since it is necessary to synthesize FN3 and (NH4)3AlF6 themselves.
Patent Publication 1: U.S. Pat. No. 3,084,025 specification
Patent Publication 2: U.S. Pat. No. 3,314,770 specification
Patent Publication 7: U.S. Pat. No. 3,304,248 specification
Patent Publication 8: U.S. Pat. No. 4,001,380 specification
Non-patent Publication 3: EXTON, D. B., Williams S. A., et al., J. Phys. Chem., 1993
It is an object of the present invention to provide a process for industrially synthesizing halogenated nitrogen compounds with safety and easiness.
As a result of an eager examination, the present inventors have found that a halogenated nitrogen is obtained with good yield by reacting an ammonium complex compound that is one selected from the group consisting of an acidic ammonium fluoride (NH4F.nHF, 1<n), an acidic fluoroammonium complex ((NH4)yMFz.mHF, 1≦y≦4, 2≦z≦8, 0.1≦m) and a mixture of these and that is in liquid form, with an interhalogen compound or a mixture of the interhalogen compound and F2 gas, thereby reaching the present invention.
According to the present invention, a process for synthesizing a halogenated nitrogen represented by a formula of NFxL3-x. (L represents a halogen other than fluorine, and 1≦x≦3) is provided. This process comprises the step of (a) reacting an ammonium complex compound that is one selected from the group consisting of NH4F.nHF, (NH4)yMFz.mHF and a mixture of these and that is in liquid form, with an interhalogen compound or a mixture of an interhalogen compound and F2 gas, wherein 1<n, 1≦y≦4, 2≦z≦8, 0.1≦m, and M represents one selected from the group consisting of elements of group 1 to group 16 of periodic table and a mixed element of these elements.
In the following, the present invention is described in detail.
In the present invention, when an interhalogen compound is reacted with a molten salt of HF adduct of the ammonium salt or fluoroammonium complex salt or a HF solution of the ammonium salt or fluoroammonium complex salt, the interhalogen compound is utilized by almost 100%, and a halogenated nitrogen NFxL3-x (L=halogen) is produced. A reaction of the produced halogenated nitrogen gas with F2 or HF produces NF3 and an interhalogen compound. Furthermore, the produced interhalogen compound can be reused in the above reaction step.
In the present invention, an acidic ammonium fluoride (NH4F.nHF) in liquid form is used as a raw material. Although 1<n, preferably 2.0≦n≦20. An acidic fluoroammonium complex ((NH4)yMFz.mHF), which is another raw material, is used. Here, y, z and m are numbers in ranges of 1≦y≦4, 2≦z≦8, and 0.1≦m. M represents one selected from the group consisting of elements of group 1 to group 16 of periodic table and a mixed element of these elements.
Specifically, M is Al, Be, Cd, Ce, Cr, Co, Cu, Ga, Ge, Ho, In, Fe, Pb, Mn, Nb, Ni, P, Sb, Si, Sn, Th, Ti, V, Zn, Zr, W, Mg, Li, K, or Na. As compounds using these, it is possible to cite (NH4)3AlF6, NH4AlF4, NH4MgAlF6, NH4BeF4, NH4LiBeF4, NH4NaBeF4, NH4CdF3, NH4CeF5, (NH4)4CeF8, (NH4)2CeF6, (NH4)4CeF7, (NH4)3CrF6, NH4CrF6, NH4CrF3, (NH4)2CoF4, (NH4)2CoF6, NH4CoF3, NH4CuF3, (NH4)2CuF4, (NH4)3CuF6, (NH4)3GaF6, (NH4)2GaF5, NH4GaF4, (NH4)2GeF6, (NH4)3GeF7, NH4HoF, (NH4)2In3F6, (NH4)3FeF6, NH4Fe2F6, NH4FeF4, (NH4)2NaFeF6, (NH4)2KFeF6, (NH4)2PbF6, NH4MnF3, (NH4)3MnF6, NH4NbF6, (NH4)2NiF4, NH4NiF3, NH4 PF6, NH4SbF6, NH4SbF4, NH4Sb2F7, (NH4)2SiF6, (NH4)3SiF7, NH4LiSiF6, (NH4)2SnF6, (NH4)4ThF8, (NH4)3ThF7, (NH4)3TiF6, (NH4)3TiF7, (NH4)3VF6, NH4ZnF3, (NH4)2ZnF4, (NH4)3ZrF7, NH4ZrF5, (NH4)2ZrF6, NH4WF7, and the like. It is possible to use a mixture of these. Of these compounds, particularly preferable ones are (NH4)3AlF6, NH4AlF4, NH4CuF3, (NH4)2CuF4, (NH4)3CuF6, (NH4)3FeF6, NH4Fe2F6, NH4FeF4, (NH4)2NiF4, NH4NiF3, and (NH4)2SiF6.
In the synthesis process of the present invention, it is optional to add an alkali metal fluoride or alkali-earth metal fluoride in order to lower volatility of a molten salt of HF adduct of the ammonium salt or fluoroammonium complex salt or a HF solution of the ammonium salt or fluoroammonium complex salt. In order to regenerate the ammonium salt or fluoroammonium complex salt, it can be accomplished by introducing NH3, a mixed gas or mixed liquid of NH3 and HF, or NH4F into the reactor with the synthesis process of the halogenated nitrogen.
As the interhalogen compound used in the present invention, it is possible to cite ClF5, ClF3, ClF, BrF5, BrF3, BrF, IF7, IF5, IF3, IF and the like. In particular, ClF3, BrF5, BrF3, IF7, IF5, and IF3 are preferable.
It is possible to cite LiF, NaF, KF, RbF, CsF, FrF2 and the like as the alkali metal fluoride, which is used in the present invention, for lowering volatility of a molten salt of HF adduct of the ammonium salt or fluoroammonium complex salt or a HF solution of the ammonium salt or fluoroammonium complex salt. As the alkali-earth metal fluoride, it is possible to cite BeF2, MgF2, CaF2, SrF2, BaF2, RaF2, and the like. In particular, LiF, NaF, KF, RbF, CsF, MgF2, CaF2, BaF2, and the like are preferable.
As the reaction process, it is possible to select a process in which the reaction is conducted by supplying an interhalogen compound in gaseous form or liquid form to a molten salt or HF solution of the ammonium salt or fluoroammonium complex salt previously put into the reactor, a process in which a molten salt or HF solution of HF adduct of the ammonium salt or fluoroammonium complex salt is added in a dropwise manner to a HF solution of an interhalogen compound solution, or a process in which their solids themselves are added.
One of great advantages of this process is that the reaction temperature range is wide. For example, in a reaction of an acidic ammonium fluoride molten salt with F2, only a relatively narrow temperature of 120° C. to 200° C. makes it possible to synthesize a halogenated nitrogen (nitrogen trifluoride). However, the process of the present invention makes the synthesis possible in the after-mentioned wide range.
In the case of introducing an interhalogen compound into a HF adduct of a liquid ammonium salt or fluoroammonium complex salt, it suffices that the lower limit of the reaction temperature is not lower than a higher one of melting point of the HF adduct of the liquid ammonium salt or fluoroammonium complex salt and that of the interhalogen compound. In the case of introducing a HF adduct of a solid or liquid ammonium salt or fluoroammonium complex salt into a liquid interhalogen compound or its HF solution, it suffices to have a temperature, at which the interhalogen compound or the HF solution of the ammonium salt does not solidify, or higher. The upper limit of the reaction temperature is preferably not higher than 250° C. Exceeding 250° C. is not preferable, since corrosion of the apparatus material is vigorous. The range of the reaction temperature is as above. More preferably, it is from 0° C. to 200° C.
In the case of conducting the synthesis by a reaction between a HF adduct of the fluoroammonium complex salt and an interhalogen compound, a temperature of 20° C. to 250° C. is preferable, more preferably from 50° C. to 200° C. If the temperature is low, the reaction does almost not proceed. If the temperature is high, the generation rate of N2 becomes high. Therefore, they are not preferable.
The pressure for the reaction may suitably be set in view of vapor pressures of the ammonium salt and the fluoroammonium complex salt.
A halogen other than fluorine of the interhalogen compound is formed mostly as chlorine, bromine, iodine, or nitrogen halide. Therefore, it can be regenerated into a fluorine-containing, interhalogen compound by reacting a gas discharged from the reactor with F2. Thus, it can be reused as a synthesis raw material.
Next, the regeneration of NH4F.nHF or (NH4)yMFz.mHF can be conducted by introducing NH3, while reacting an ammonium complex compound selected from the group consisting of NH4F.nHF, (NH4)yMFz.mHF and a mixture of these with an interhalogen compound. Specifically, a HF solution, in which NH4AlF4 is dispersed, remains in a solution, in which NF2Cl and NF3 have been generated by the reaction between (NH4)3AlF6 and ClF3. Blowing NH3 therein regenerates (NH4)3AlF6. In the regeneration, according to need, it is optional to allow HF to flow at the same time, and it is optional to introduce NH4F and NH4F.nHF, which have previously been synthesized.
The process of the present invention makes it possible to easily produce with low price NF3, which is a cleaning gas useful for interior washing of semiconductor production apparatuses such as CVD apparatuses, and halogenated nitrogens, which are useful as a raw material for synthesizing difluoroaminoalkanes from lower normal alkyl mercury compounds.
In the following, the present invention is described in detail by examples. The present invention is, however, not limited to such examples.
(NH4)3AlF6.6HF in the form of liquid was put into a stainless steel container, and 100% F2 was bubbled under the following conditions with stirring. The discharged gas was passed through a cooling trap (0° C.), and then it was analyzed by FT-IR, UV and gas chromatography. With this, the generation of a trace amount of NF3 was found, but most of it was the unreacted F2 (Table 1). HF is excluded from the concentrations in Table 1. The reason is that the HF concentration increase by volatilization of the molten salt and the conveyance of the gas flow result in no mass balance.
[Conditions] stainless steel container: φ55 mm×H220 mm, 500 ml
3 cm immersion from the gas-blowing nozzle
Pressure in the container: 93.3 kPa
Reaction temperatures: 60° C., 100° C. and 120° C.
NH4F.2.5HF in the form of liquid was put into a stainless steel container, and 100% F2 was bubbled under the following conditions with stirring. The discharged gas was passed through a cooling trap (0° C.), and then it was analyzed by FT-IR, UV and gas chromatography. With this, the generation of a trace amount of NF3 was found, but most of it was the unreacted F2 (Table 2). HF is excluded from the concentrations in Table 2. The reason is that the HF concentration increase by volatilization of the molten salt, the conveyance of the gas flow, and conducting the synthesis without additionally charging the liquid layer with NH3 result in change over time of the concentration of the volatilizing HF and thereby no mass balance.
[Conditions] stainless steel container: 455 mm×H220 mm, 500 ml
3 cm immersion from the gas-blowing nozzle
Pressure in the container: 93.3 kPa
Reaction temperatures: 60° C., 100° C. and 120° C.
(NH4)3AlF6.6HF in the form of liquid was put into a stainless steel container, and 100% ClF3 was bubbled under the following conditions with stirring. The discharged gas was analyzed by FT-IR, UV and gas chromatography (Table 3). As a result, it was found that ClF3 reacted by 85% even at 0° C., and that halogenated nitrogens, such as NF2Cl and NF3, were obtained. HF is excluded from the concentrations in Table 3. The reason is that the HF concentration increase by volatilization of the molten salt and the conveyance of the gas flow result in no mass balance. Besides HF and substances in Table 3, HCl and Cl2 are generated.
[Conditions] stainless steel container: φ55 mm×H220 mm, 500 ml
3 cm immersion from the gas-blowing nozzle
Pressure in the container: 93.3 kPa
Reaction temperatures: 0° C., 20° C., 60° C., 100° C., 120° C. and 150° C.
NH4F.2.5HF in the form of liquid was put into a stainless steel container, and 100% ClF3 was bubbled under the following conditions with stirring. The discharged gas was analyzed by FT-IR, UV and gas chromatography (Table 4). As a result, it was found that halogenated nitrogens, such as NF2Cl, NFCl2 and NF3, were obtained. HF is excluded from the concentrations in Table 4. The reason is that the HF concentration increase by volatilization of the molten salt and the conveyance of the gas flow result in no mass balance. Besides HF and substances in Table 4, HCl and Cl2 are generated. Similar results were obtained even in case that ClF3 was diluted to 20% by using Ar as a diluting gas.
[Conditions] stainless steel container: φ55 mm×H220 mm, 500 ml
3 cm immersion from the gas-blowing nozzle
Pressure in the container: 93.3 kPa
Reaction temperatures: −15° C., 0° C., 20° C., 60° C., 100° C., 120° C. and 150° C.
NH4F.2.5HF in the form of liquid was put into a stainless steel container, the temperature was increased to 100° C., and 1% ClF3 (He diluting gas) was bubbled under the following conditions with stirring. The discharged gas was analyzed by FT-IR, UV and gas chromatography. As a result, NF3 was obtained with a yield of 85% (based on ClF3).
[Conditions] stainless steel container: 55 mm×H220 mm, 500 ml
3 cm immersion from the gas-blowing nozzle
Pressure in the container: 93.3 kPa
A gas obtained by an experiment similar to Example 3 was passed through a NaF tube, thereby lowering HF to 100 ppm or lower. Then, an FT-IR analysis was conducted, while F2 was mixed by 100 SCCM in a stainless steel tube (½ inch φ×500 mL) heated at 100° C. As a result, NF2Cl disappeared, and NF3 and ClF3 were obtained. Even when the heating temperature was increased to 300° C., NF3 and ClF3 were obtained. Furthermore, when the heated gas was passed through a trap cooled to −78° C. with refrigerant, ClF3 was obtained in the trap, and it was possible to pass NF3 through the trap. The collected ClF3 was reused in the synthesis.
A stainless steel container used in Example 14 was charged with 300 CC (mixing ratio ClF3:HF=1:10) of a HF solution of ClF3, and NH4F.10HF in the form of liquid was added in a dropwise manner at 0° C. with stirring. With this, NF3 and NF2Cl were obtained at a ratio of 1:2. The generation rate of N2 was 30% of the total. Similar results were obtained even by using BrF5, BrF3, IF7, IF5 and IF3 in place of ClF3.
A stainless steel container used in Example 14 was charged with a NH4F.2HF solution (300 CC), and ClF3 and F2 were blown by mixing of 20 SCCM and 10 SCCM at 60° C. with stirring. With this, NF2Cl was almost not obtained, but NF3 was obtained. The generation rate of N2 upon this was 5% of the total.
A stainless steel container was charged with NH4F.2.5HF in the form of liquid, 10% ClF3 diluted with NF3 was bubbled, and at the same time NH3 diluted to 10% was bubbled from a tube that was different from the tube, from which ClF3 was bubbled. The discharged gas was analyzed by FT-IR, UV and gas chromatography. As a result, NF3 and Cl2 were obtained.
[Conditions] stainless steel container: φ55 mm×H220 mm, 500 ml
3 cm immersion from the gas-blowing nozzle
Pressure in the container: 93.3 kPa
Reaction temperature: 125° C.
ClF3 flow rate: 12 SCCM
NH3 flow rate: 4 SCCM
ClF3 was blown into NH4F.2.5HF in the liquid form under the following conditions. A gas discharged from the reactor was analyzed by FT-IR and UV. With this, it was found to be a gas in which NF2Cl, NFCl2, HF, ClF and Cl2 were mixed together. This gas together with F2 (100 SCCM) was introduced into a Ni tube heated at 100° C. By analysis of a gas discharged from the Ni tube, it was found that NF2Cl and NFCl2 disappeared and NF3 was generated. A similar result was obtained even by replacing the acidic ammonium fluoride by (NH4)3AlF6.6HF.
[Conditions] stainless steel container: φ55 mm×H220 mm, 500 ml
6 cm immersion from the gas-blowing nozzle
Pressure in the container: 93.3 kPa
Reaction temperature: 40° C. (The gas introduction was started at room temperature. The temperature increased to 40° C. by its own heat and stabilized.)
ClF3 flow rate: 50 SCCM
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-197436 | Jul 2005 | JP | national |
| 2005-229584 | Aug 2005 | JP | national |
| 2006-113720 | Apr 2006 | JP | national |
| 2006-153015 | Jun 2006 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2006/312149 | 6/16/2006 | WO | 00 | 10/23/2007 |
