IF7-derived iodine fluoride compound recovery method and recovery device
09676626 ยท 2017-06-13
Assignee
Inventors
Cpc classification
International classification
Abstract
An IF.sub.7-derived iodine fluoride compound recovery method includes putting gas containing IF.sub.7 into contact with a material to be fluorinated, thereby converting the IF.sub.7 into IF.sub.5; and cooling gas containing the IF.sub.5, thereby trapping the IF.sub.5 as an IF.sub.7-derived iodine fluoride compound. The recovered IF.sub.5 may be reacted with fluorine to generate IF.sub.7, which may be reused for a semiconductor production process.
Claims
1. An IF.sub.7-derived iodine fluoride compound recovery method, comprising: putting gas containing IF.sub.7 into contact with a material to be fluorinated containing at least one of elemental Si, elemental W or aluminum oxide, thereby converting the IF.sub.7 into IF.sub.5; and cooling gas containing IF.sub.5, thereby trapping the IF.sub.5 as an IF.sub.7-derived iodine fluoride compound.
2. The IF.sub.7-derived iodine fluoride compound recovery method according to claim 1, wherein the material to be fluorinated is contained at a content of at least 20% by weight.
3. The IF.sub.7-derived iodine fluoride compound recovery method according to claim 1, wherein the material to be fluorinated is Si.
4. The IF.sub.7-derived iodine fluoride compound recovery method according to claim 1, wherein the IF.sub.5 is recovered at a temperature of 80 C. or higher and 50 C. or lower.
5. The IF.sub.7-derived iodine fluoride compound recovery method according to claim 2, wherein the IF.sub.5 is recovered at a temperature of 80 C. or higher and 50 C. or lower.
6. The IF.sub.7-derived iodine fluoride compound recovery method according to claim 3, wherein the IF.sub.5 is recovered at a temperature of 80 C. or higher and 50 C. or lower.
7. A reuse method of IF.sub.7 comprising: putting gas containing IF.sub.7 into contact with a material to be fluorinated containing at least one of elemental Si, elemental W or aluminum oxide, thereby converting the IF.sub.7 into IF.sub.5; cooling gas containing the IF.sub.5, thereby trapping the IF.sub.5 as an IF.sub.7-derived iodine fluoride compound; reacting the IF.sub.5 that is recovered with fluorine, thereby generating IF.sub.7; and reusing the generated IF.sub.7 for a semiconductor production process.
8. The reuse method of IF.sub.7 according to claim 7, wherein the material to be fluorinated is Si.
9. The reuse method of IF.sub.7 according to claim 7, wherein the IF.sub.5 is recovered at a temperature of 80 C. or higher and 50 C. or lower.
Description
BRIEF DESCRIPTION OF DRAWINGS
(1)
REFERENCE SIGNS LIST
(2) 1: reaction tube; 2: exhaust gas flow-in passage; 3: exhaust gas flow-out passage; 4: heating unit; 5: trap device; 6: gas discharge passage; 7: chiller; 8: introduction passage; 9: introduction passage; 11: valve; 12: valve; 13: valve; 14: valve; 15: valve; 100: recovery device
DESCRIPTION OF EMBODIMENTS
(3) Hereinafter, an IF.sub.7-derived iodine fluoride compound recovery method and recovery device according to the present invention will be described with reference to the drawings. The IF.sub.7-derived iodine fluoride compound recovery method and recovery device according to the present invention are not to be construed as being limited to the following embodiments or examples. In the drawings referred to in the embodiments and examples, the same elements or elements having the same functions will bear the same reference signs, and the descriptions thereof will not be repeated.
(4) According to the present invention, an IF.sub.7-derived iodine fluoride compound is recovered by putting IF.sub.7 into contact with a material to be fluorinated and thus converting the IF.sub.7 into IF.sub.5. For such a method of recovery, an attention is focused on that IF.sub.7 and IF.sub.5 are different in the vapor pressure. Unlike IF.sub.7, IF.sub.5 can be recovered as a solid at a high temperature (temperature that is not a very low temperature). Namely, the present invention has a feature of converting IF.sub.7 into IF.sub.5, so that a general-purpose cooling device can be used for the recovery.
(5)
(6) The material to be fluorinated that is to fill the reaction tube 1 is fluorinated itself to convert IF.sub.7 into IF.sub.5. In this embodiment, the material to be fluorinated that is introduced into the reaction tube 1 may contain at least one element selected from, for example, Si, Al, W and I. The material to be fluorinated is not limited to such an element. In this embodiment, a material containing Si, which is generally used as a semiconductor, is preferably usable as the material to be fluorinated. Preferably, the material to be fluorinated that is to fill the reaction tube 1 contains at least one element selected from the above list at a content of at least 20% by weight. The material to be fluorinated contains at least one element selected from the above list more preferably at a content of at least 50% by weight, and still more preferably at a content of 80% by weight. When the content of such an element in the material to be fluorinated is less than 20% by weight, the conversion efficiency from IF.sub.7 to IF.sub.5 is not sufficient, which is not preferable.
(7) Outside the reaction tube 1, a heater is located as a heating unit 4. The heating unit 4 maintains the inside of the reaction tube 1 at a temperature sufficiently high to convert IF.sub.7 into IF.sub.5 by use of the material to be fluorinated. The temperature used to convert IF.sub.7 into IF.sub.5 varies in accordance with the material to be fluorinated that fills the reaction tube 1 or the process pressure. In consideration of the reaction rate, the temperature used to convert IF.sub.7 into IF.sub.5 is preferably, for example, 20 C. or higher and 300 C. or lower. The reaction tube 1 can be driven at an optimal temperature in accordance with the material to be fluorinated. In the process of introducing the exhaust gas into the reaction tube 1 to convert IF.sub.7 into IF.sub.5, He, Ne, Ar, Xe, Kr, N.sub.2 or the like is optionally usable as accompanying gas.
(8) The residence time of the gas in the reaction tube 1 may be any time that is sufficient to convert IF.sub.7 into IF.sub.5. There is no influence on the recovery ratio even if the residence time is further extended. The time necessary to convert IF.sub.7 into IF.sub.5 depends on the flow rate. In the case where, for example, the reaction tube 1 is connected to an etching device, the time necessary to convert IF.sub.7 into IF.sub.5 depends on the etching rate in the etching device. In the case where the reaction tube 1 is connected to a common etching device, the residence time of the gas in the reaction tube 1 is about a few minutes (3 to 5 minutes).
(9) The gas containing IF.sub.5 converted from IF.sub.7 in the reaction tube 1 is introduced into the trap device 5 via an exhaust gas flow-out passage 3. The amount of the gas to be introduced into the trap device 5 via the exhaust gas flow-out passage 3 is adjusted by a valve 12. The trap device 5 is used to trap IF.sub.5 contained in the introduced gas, and may be, for example, a general-purpose cooling device. The trap device 5 is connected to, for example, an introduction passage 8 used to introduce a cooling liquid from a chiller 7 and also to an introduction passage 9 used to introduce the cooled liquid into the chiller 7. A valve 14 is provided in introduction passage 8, and a valve 15 is provided in the introduction passage 9. The temperature used to cool the trap device 5 can be adjusted by the valve 14 and the valve 15. The gas introduced into the trap device 5 is cooled at a predetermined temperature, for example, 80 C. or higher and 50 C. or lower. Thus, IF.sub.5 is liquefied and thus trapped. The exhaust gas after IF.sub.5 is trapped flows out from a gas discharge passage 6 via a valve 13.
(10) As described above, according to the present invention, the recovery device 100 is used to put the gas containing IF.sub.7 into contact with the material to be fluorinated and thus to convert IF.sub.7 into IF.sub.5 in the reaction tube 1. The gas containing the generated IF.sub.5 is cooled in the trap device 5, and the IF.sub.5 is trapped as an IF.sub.7-derived iodine fluoride compound. Conventionally, a cooling device of a very low temperature is needed to condense and recover IF.sub.7 contained in the exhaust gas, as described above. By contrast, according to the present invention, IF.sub.7 is converted into IF.sub.5 and thus the IF.sub.5 can be recovered from the gas after being cooled in a temperature range realized by a general-purpose cooling device. A plurality of reaction tubes 1 and a plurality of trap devices 5 may be provided and used in a switched manner, so that the iodine fluoride can be recovered continuously.
(11) The recovery device 100 may further include a fluorination device that reacts the recovered IF.sub.5 with fluorine to generate IF.sub.7. There are various known methods for fluorinating IF.sub.5 to generate IF.sub.7. Any of such known techniques can be applied for a fluorination device to be arranged in or connected to the recovery device 100.
EXAMPLES
(12) Hereinafter, the present invention will be described in detail by way of examples. The present invention is not limited to the following examples. In the examples, the present invention was applied to exhaust gas generated in a dry etching process. As the material to be fluorinated that is introduced into the reaction tube 1, silicon (Si) was used in examples 1 through 6, activated alumina (Al.sub.2O.sub.3) was used in examples 7 through 12, iodine (I.sub.2) was used in examples 13 through 17, and tungsten (W) was used in examples 18 through 22. In reference example 1, iodine (I.sub.2) was used and the temperature of the reaction tube was different from example 17 and the like. In comparative examples 1 through 4, the reaction tube 1 was not used and the trap device 5 was used for the recovery.
Example 1
(13) In example 1, the reaction tube 1 was filled with Si, and gas containing IF.sub.7, IF.sub.5 and N.sub.2 at a volume ratio of IF.sub.7:IF.sub.5:N.sub.2=50:10:40 was introduced into the reaction tube 1 at 100 sccm. The conversion from IF.sub.7 into IF.sub.5 was performed at a temperature of the reaction tube 1 of 80 C. IF.sub.5 was trapped at a temperature of the trap device 5 of 50 C.
Example 2
(14) In example 2, IF.sub.5 was trapped under substantially the same conditions as those in example 1 except that the total flow rate of the gas to be introduced was 300 sccm.
Example 3
(15) In example 3, IF.sub.5 was trapped under substantially the same conditions as those in example 1 except that the volume ratio of IF.sub.7, IF.sub.5 and N.sub.2 of the gas to be introduced was IF.sub.7:IF.sub.5:N.sub.2=90:10:0.
Examples 4 and 5
(16) In examples 4 and 5, IF.sub.5 was trapped under substantially the same conditions as those in example 1 except that the cooling temperature of the trap device 5 was different. In example 4, the cooling temperature was 20 C. In example 5, the cooling temperature was 10 C.
Example 6
(17) In example 6, IF.sub.5 was trapped under substantially the same conditions as those in example 1 except that the temperature of the reaction tube 1 was 30 C.
Example 7
(18) In example 7, the reaction tube 1 was filled with Al.sub.2O.sub.3, and gas containing IF.sub.7, IF.sub.5 and N.sub.2 at a volume ratio of IF.sub.7:IF.sub.5:N.sub.2=50:10:40 was introduced into the reaction tube 1 at 100 sccm. The conversion from IF.sub.7 into IF.sub.5 was performed at a temperature of the reaction tube 1 of 80 C. IF.sub.5 was trapped at a temperature of the trap device 5 of 50 C.
Example 8
(19) In example 8, IF.sub.5 was trapped under substantially the same conditions as those in example 7 except that the total flow rate of the gas to be introduced was 300 sccm.
Example 9
(20) In example 9, IF.sub.5 was trapped under substantially the same conditions as those in example 7 except that the volume ratio of IF.sub.7, IF.sub.5 and N.sub.2 of the gas to be introduced was IF.sub.7:IF.sub.5:N.sub.2=90:10:0.
Examples 10 and 11
(21) In examples 10 and 11, IF.sub.5 was trapped under substantially the same conditions as those in example 7 except that the cooling temperature of the trap device 5 was different. In example 10, the cooling temperature was 20 C. In example 11, the cooling temperature was 10 C.
Example 12
(22) In example 12, IF.sub.5 was trapped under substantially the same conditions as those in example 7 except that the temperature of the reaction tube 1 was 30 C.
Example 13
(23) In example 13, the reaction tube 1 was filled with I.sub.2, and gas containing IF.sub.7, IF.sub.5 and N.sub.2 at a volume ratio of IF.sub.7:IF.sub.5:N.sub.2=50:10:40 was introduced into the reaction tube 1 at 100 sccm. The conversion from IF.sub.7 into IF.sub.5 was performed at a temperature of the reaction tube 1 of 300 C. IF.sub.5 was trapped at a temperature of the trap device 5 of 50 C.
Example 14
(24) In example 14, IF.sub.5 was trapped under substantially the same conditions as those in example 13 except that the total flow rate of the gas to be introduced was 300 sccm.
Example 15
(25) In example 15, IF.sub.5 was trapped under substantially the same conditions as those in example 13 except that the volume ratio of IF.sub.7, IF.sub.5 and N.sub.2 of the gas to be introduced was IF.sub.7:IF.sub.5:N.sub.2=90:10:0.
Example 16
(26) In example 16, IF.sub.5 was trapped under substantially the same conditions as those in example 13 except that the cooling temperature of the trap device 5 was 20 C.
Example 17
(27) In example 17, IF.sub.5 was trapped under substantially the same conditions as those in example 13 except that the temperature of the reaction tube 1 was 200 C.
Example 18
(28) In example 18, the reaction tube 1 was filled with W, and gas containing IF.sub.7, IF.sub.5 and N.sub.2 at a volume ratio of IF.sub.7:IF.sub.5:N.sub.2=50:10:40 was introduced into the reaction tube 1 at 100 sccm. The conversion from IF.sub.7 into IF.sub.5 was performed at a temperature of the reaction tube 1 of 100 C. IF.sub.5 was trapped at a temperature of the trap device 5 of 50 C.
Example 19
(29) In example 19, IF.sub.5 was trapped under substantially the same conditions as those in example 18 except that the total flow rate of the gas to be introduced was 300 sccm.
Example 20
(30) In example 20, IF.sub.5 was trapped under substantially the same conditions as those in example 18 except that the volume ratio of IF.sub.7, IF.sub.5 and N.sub.2 of the gas to be introduced was IF.sub.7:IF.sub.5:N.sub.2=90:10:0.
Examples 21 and 22
(31) In examples 21 and 22, IF.sub.5 was trapped under substantially the same conditions as those in example 18 except that the cooling temperature of the trap device 5 was different. In example 21, the cooling temperature was 20 C. In example 22, the cooling temperature was 10 C.
Reference Example 1
(32) In reference example 1, IF.sub.5 was trapped under substantially the same conditions as those in example 17 except that the temperature of the reaction tube 1 was 30 C.
Comparative Examples 1 through 4
(33) In comparative examples 1 through 4, the reaction tube 1 was not used. Gas containing IF.sub.7, IF.sub.5 and N.sub.2 at a volume ratio of IF.sub.7:IF.sub.5:N.sub.2=50:10:40 was introduced into the trap device 5 at 100 sccm. IF.sub.5 was trapped at a temperature of the trap device 5 of 50 C. in comparative example 1, of 100 C. in comparative example 2, of 196 C. in comparative example 3, and of 10 C. in comparative example 4.
(34) Table 1 shows the recovery ratio of IF.sub.5 and the purity of IF.sub.5 in the recovered gas in examples 1 through 22, reference example 1 and comparative examples 1 through 4.
(35) TABLE-US-00001 TABLE 1 Gas Total Temp. of Temp. Recovery Purity of concentration flow Material in reaction of trap ratio IF.sub.5 in (% by volume) rate reaction tower device (converted recovered IF.sub.7 IF.sub.5 N.sub.2 (sccm) tower ( C.) ( C.) into I) gas Ex. 1 50 10 40 100 Si 80 50 99.9 >99 Ex. 2 50 10 40 300 99.9 >99 Ex. 3 90 10 0 100 99.9 >99 Ex. 4 50 10 40 100 20 98.4 >99 Ex. 5 50 10 40 100 10 95 >99 Ex. 6 50 10 40 100 30 50 99.9 >99 Ex. 7 50 10 40 100 Al.sub.2O.sub.3 80 50 99.9 >99 Ex. 8 50 10 40 300 94.3 >99 Ex. 9 90 10 0 100 99.9 >99 Ex. 10 50 10 40 100 20 98.4 >99 Ex. 11 50 10 40 100 10 95 >99 Ex. 12 50 10 40 100 30 50 80 >99 Ex. 13 50 10 40 100 I.sub.2 300 50 99.9 >99 Ex. 14 50 10 40 300 95.6 >99 Ex. 15 90 10 0 100 99.9 >99 Ex. 16 50 10 40 100 20 99.1 >99 Ex. 17 50 10 40 100 200 50 95.1 >99 Ex. 18 50 10 40 100 W 100 50 94.7 82 Ex. 19 50 10 40 300 90.8 86 Ex. 20 90 10 0 100 99.4 78 Ex. 21 50 10 40 100 20 92.4 86 Ex. 22 50 10 40 100 10 90.6 88 Reference 50 10 40 100 I.sub.2 30 50 30.5 >99 ex. 1 Comparative 50 10 40 100 50 40.1 >99 ex. 1 Comparative 50 10 40 100 100 99.5 >99 ex. 2 Comparative 50 10 40 100 196 99.9 >99 ex. 3 Comparative 50 10 40 100 10 0 >99 ex. 4
(36) In the examples, the recovery ratio of IF.sub.5 was 90% or higher even when the cooling temperature of the trap device 5 was 10 C. By contrast, the recovery ratio was merely 40% under the conditions of comparative example 1 even when the cooling temperature of the trap device 5 was 50 C. Under the conditions of comparative example 4, IF.sub.5 was not recovered when the cooling temperature of the trap device 5 was 10 C. As is clear from comparative examples 2 and 3, IF.sub.7 needed to be cooled at 100 C. for trapping in order to realize a recovery ratio of 99% or higher without being converted into IF.sub.5.
(37) The following evaluation is as compared with example 1 unless otherwise specified. In example 1 through 3, Si was used as the material to be fluorinated. No difference was recognized in the recovery ratio or the purity of IF.sub.5 even where the total flow rate of the gas to be introduced into the reaction tube 1 was higher as in example 2 or even where the ratio of IF.sub.7 in the gas was higher as in example 3. By contrast, in examples 4 and 5, in which the cooling temperature of the trap device 5 was higher, the recovery ratio of IF.sub.5 was slightly lower. In example 6, in which the temperature of the reaction tube 1 was 30 C., no difference was recognized in the recovery ratio or the purity of IF.sub.5.
(38) In example 7, in which Al.sub.2O.sub.3 was used as the material to be fluorinated, no difference was recognized in the recovery ratio or the purity of IF.sub.5 as compared with examples 1 through 3. In example 8, in which the total flow rate of the gas to be introduced into the reaction tube 1 was 300 sccm, the recovery ratio of IF.sub.5 was slightly lower. By contrast, in example 9, in which the ratio of IF.sub.7 in the gas to be introduced into the reaction tube 1 was higher, no difference was recognized in the recovery ratio or the purity of IF.sub.5. In examples 10 and 11, in which the cooling temperature of the trap device 5 was higher, the recovery ratio of IF.sub.5 was slightly lower as in examples 4 and 5. In example 12, in which Al.sub.2O.sub.3 was used as the material to be fluorinated and the temperature of the reaction tube 1 was 30 C., the recovery ratio of IF.sub.5 was slightly lower but still was twice the recovery ratio in comparative example 1.
(39) In example 13, in which I.sub.2 was used as the material to be fluorinated, no difference was recognized in the recovery ratio or the purity of IF.sub.5 as compared with examples 1 through 3. In example 14, in which the total flow rate of the gas to be introduced into the reaction tube 1 was 300 sccm, the recovery ratio of IF.sub.5 was slightly lower as in example 8. In example 15, in which the ratio of IF.sub.7 in the gas to be introduced into the reaction tube 1 was higher, no difference was recognized in the recovery ratio or the purity of IF.sub.5. In example 16, in which the cooling temperature of the trap device 5 was 20 C., the recovery ratio of IF.sub.5 was slightly lower as in examples 4 and 10. In example 17, in which the temperature of the reaction tube 1 was 200 C., the recovery ratio of IF.sub.5 was slightly lower. In reference example 1, in which the temperature of the reaction tube 1 was 30 C., the recovery ratio of IF.sub.5 was about 30%. However, in reference example 1, the purity of IF.sub.5 in the recovered gas exceeded 99%, which was equivalent to that of the above-evaluated examples of the present invention. In reference 1, the reaction temperature of the reaction tube 1 is lower. Therefore, the recovery ratio can be made as high as that of the examples of the present invention by making the reaction time sufficiently long. In the case where I.sub.2 is used as the material to be fluorinated, IF.sub.5 is generated and recovered. In the examples in which I.sub.2 was used, a reduction in the mass of the material to be fluorinated in the reaction tube 1 was subtracted from the total recovery amount to calculate the recovery ratio of IF.sub.5.
(40) In example 18, in which W was used as the material to be fluorinated, the recovery ratio of IF.sub.5 was slightly lower than in examples 1 through 3. In example 19, in which the total flow rate of the gas to be introduced into the reaction tube 1 was 300 sccm, the recovery ratio of IF.sub.5 was slightly lower as in examples 8 and 14. By contrast, in example 20, in which the ratio of IF.sub.7 in the gas to be introduced into the reaction tube 1 was higher, the recovery ratio of IF.sub.5 was higher than in example 18. In examples 21 and 22, in which the cooling temperature of the trap device 5 was higher, the recovery ratio of IF.sub.5 was slightly lower as in examples 4 and 5.
(41) In examples 18 through 22, in which W was used as the material to be fluorinated, the purity of IF.sub.5 in the recovered gas was lower. In the case where W is used as the material to be fluorinated, the reaction with IF.sub.7 progresses as follows.
W+3IF.sub.7.fwdarw.WF.sub.6+3IF.sub.5
(42) Therefore, in the case where W is used as the material to be fluorinated, WF.sub.6 is trapped as a solid together with IF.sub.5. This is why the purity of IF.sub.5 is lower.
(43) In the above-described examples, the recovery ratio is lower in the case where the temperature of the reaction tube 1 is lower. This is considered to occur because the reaction rate of converting IF.sub.7 into IF.sub.5 is decreased and thus the reaction time is insufficient. In the case where the cooling temperature of the trap device 5 is higher, the recovery ratio of IF.sub.5 is lower. This occurs because IF.sub.5 as a solid sublimates.
(44) As described above, iodine heptafluoride-derived gas can be recovered at a high efficiency with no use of a very low temperature by use of the IF.sub.7-derived iodine fluoride compound recovery method and recovery device according to the present invention.
(45) According to the present invention, a method for recovering iodine heptafluoride-derived gas at a high efficiency with no use of a very low temperature, and a recovery device therefor, are provided.
(46) The present invention is useful to recover iodine heptafluoride from iodine heptafluoride-containing gas that is discharged in microscopic processing performed by use of etching of a metal film in production of a semiconductor device.