JP4619195B2 - Trace impurity analysis method - Google Patents

Description

  The present invention relates to a trace impurity analysis apparatus and a trace impurity analysis method for managing impurity concentrations in a sample gas in real time and supplying a source gas with a more stable purity.

  In the semiconductor field in recent years, in order to improve the yield of line width processing and multi-layer processing that are increasingly miniaturized, it is required to increase the purity of the gas supplied to the semiconductor manufacturing process. In recent years, it has been considered that the yield improvement in semiconductor manufacturing can be achieved by suppressing the fluctuation of the impurity concentration rather than the high purity by reducing the impurity concentration in the process gas. Therefore, it is required to manage the impurities in the process gas in real time and statistically to a lower concentration when supplying the process gas. Specifically, for example, detection of impurities in the sub ppb order is required. In order to statistically manage the impurity concentration in the sub ppb order, an analyzer having performance that meets the requirements is required. However, in an actual semiconductor factory, absolute reliability due to contamination free and 365 days Stop operation is also required.

  FIG. 4 is a diagram for explaining an example of the configuration of a conventional impurity analyzer. In the configuration shown in FIG. 4, the sample gas A feeding path 43a provided with the pressure reducing valve 41a and the opening / closing valve 42a, and the sample gas B feeding path 43b provided with the pressure reducing valve 41b and the opening / closing valve 42b are respectively provided. When the sample gas A is analyzed, the feed path 43a is connected to the gas analysis means 44, and the pipe of the feed path 43b is removed to perform the gas analysis. When performing gas analysis of the sample gas B without connecting the inlet path 43b and the gas analyzing means 44, the inlet path 43b is connected to the gas analyzing means 44 and the piping of the inlet path 43a is removed. By not connecting the delivery path 43a and the gas analysis means 44, the gas species introduced into the gas analysis means 44 can be switched.

  However, in the impurity analyzer of such a configuration, there is a problem that it takes time to switch the gas type because the pipe must be removed and attached every time the sample gas is switched, and the impurity analysis cannot be performed in real time. .

  FIG. 5 is a diagram for explaining another example of the configuration of a conventional impurity analyzer. In the configuration shown in FIG. 5, the introduction path 53a of the sample gas A provided with the pressure reducing valve 51a and the opening / closing valve 52a, and the delivery path 53b of the sample gas B provided with the pressure reducing valve 51b and the opening / closing valve 52b are provided. 54, the introduction path 54 and the gas analysis means 55 are connected. The gas type of the sample gas introduced into the gas analyzing means 55 is switched by opening / closing the pressure reducing valves 51a, 51b and the opening / closing valves 52a, 52b. However, in the configuration as shown in FIG. 5, for example, when the sample gas B on-off valve 52 b leaks during measurement of the sample gas A, the sample gas B may be mixed into the introduction path 54, and the inflow path 53 a When the pressure with the inflow path 53b differs, the sample gas B may flow back into the inflow path 53a due to leakage of the on-off valve 52b. In these cases, the sample gas B is mixed into the gas analysis means 55, so that the accuracy of impurity analysis of the sample gas A is reduced. When the sample gas A and the sample gas B are a combination having a danger due to mixing, there is a problem that safety of gas analysis cannot be ensured.

  Patent Document 1 proposes a trace impurity analysis method in which a sample gas is fractionated by gas chromatography and then introduced into an atmospheric pressure ionization mass spectrometer together with a carrier gas to detect trace impurity components in the gas. .

  Patent Document 2 discloses a gas analyzer that combines a sample gas introduction system for switching and introducing a plurality of sample gases and an analyzer, and the sample gas introduced before switching when the sample gas is switched and introduced. There has been proposed a gas analyzer provided with means for monitoring changes in the concentration of components. In the gas analyzer of Patent Document 2, it is possible to analyze a plurality of gases with one analyzer, and when changing the type of sample gas, the concentration change of the sample gas component introduced before switching When the speed is different from the predetermined concentration change speed, the analysis operation of the gas analyzer can be stopped by closing the shut-off valve or purging the path with an inert gas such as nitrogen. . However, in the gas analyzer of Patent Document 2, since pipes of different gas series are combined and the gas is switched to the analytical instrument only by switching the valve, if a leak occurs in the valve of one sample gas introduction system, one sample The gas and other sample gas may be mixed, or one sample gas may flow backward to the other sample gas introduction path. When these phenomena occur, there is a problem that sufficient analysis accuracy cannot be obtained, and a problem that safety cannot be secured depending on the kind of gas to be mixed.

Patent Document 3 discloses an apparatus for analyzing trace impurities in a gas comprising a gas chromatograph and an atmospheric pressure ionization mass spectrometer, wherein a sample gas introduced from a sample gas introduction source is supplied to the atmospheric pressure ionization mass spectrometer. And a system for introducing the gas into the atmospheric pressure ionization mass spectrometer via the gas chromatograph, and a flow path switching means for switching the flow path of the sample gas to either of the two systems. The gas chromatograph is provided with a carrier gas introduction path for entraining the impurities separated by the gas chromatograph and introducing them into the atmospheric pressure ionization mass spectrometer. An analysis apparatus has been proposed. According to the analyzer of Patent Document 3, all impurities in the sample gas can be measured simply by switching the flow path of the sample gas. However, since the analysis apparatus of Patent Document 3 has a configuration in which the flow path of the sample gas is switched, there still remains a problem of deterioration in analysis accuracy and safety due to mixing of different gases.
JP-A-6-34616 JP-A-11-295270 JP 2004-294446 A

  The present invention solves the above-described problems, can measure trace impurities in a sample gas in real time, and can further analyze a plurality of types of sample gases by switching in a short cycle. It is another object of the present invention to provide a trace impurity analysis method.

  The present invention is a trace impurity analyzer for detecting impurity components contained in a plurality of types of sample gases for each of the sample gases, and is arranged in parallel for each of the sample gases. A plurality of inlet paths, an introduction path where the plurality of inlet paths merge, and one or more gas analysis means connected to the inlet path, each of the plurality of inlet paths, At least two on-off valves and a decompression means for decompressing the path between the two on-off valves are provided, and by switching the type of sample gas introduced into the gas analysis means, 1 The present invention relates to a trace impurity analysis apparatus in which two or more kinds of sample gases are sequentially introduced into a gas analysis means.

  In the trace impurity analyzing apparatus of the present invention, it is preferable to switch the type of sample gas introduced into the gas analyzing means while maintaining the gas analyzing means in an operating state.

  The gas analysis means in the trace impurity analyzer of the present invention preferably includes an atmospheric pressure ionization mass spectrometer. It is also preferred that the gas analysis means comprises an atmospheric pressure ionization mass spectrometer and a gas chromatograph.

  In the trace impurity analyzer of the present invention, it is preferable to further provide a purge path connected to the introduction path.

  The present invention also relates to a trace impurity analysis apparatus in which the sample gas analyzed by the gas analysis means is at least two selected from nitrogen gas, oxygen gas, argon gas, helium gas, and hydrogen gas.

  The trace impurity analyzer of the present invention is preferably operated by a fully automatic system according to a preset program.

  In the trace impurity analyzer of the present invention, it is preferable to provide a pressure monitoring means for measuring in real time the pressure of the path depressurized by the decompression means.

  The present invention further provides a trace impurity analysis method for detecting an impurity component contained in each of a plurality of types of sample gases for each of the sample gases, wherein the method is arranged in parallel for each of the sample gases, and each includes at least two Among a plurality of feeding paths for feeding a sample gas, provided with an opening / closing valve and a decompression means for decompressing the path between the two opening / closing valves, for feeding the first sample gas Closing the on-off valve in the inlet path other than the first inlet path to reduce the path between the on-off valves, and opening the two on-off valves in the first inlet path The first sample gas is introduced into the gas analyzing means through a first step of feeding the first sample gas into the first feeding path and an introduction path where the plurality of feeding paths merge. A second step of measuring the amount of trace contained in the first sample gas by the gas analyzing means. A third step of detecting an object, and a fourth step of closing the two on-off valves in the first sending-in path and reducing the path between the on-off valves to a reduced pressure state. The same operation as in the first to fourth steps is performed except that the inflow path in which the on-off valve is opened is sequentially switched to another inflow path and the type of the sample gas introduced into the gas analyzing means is changed. The present invention relates to a trace impurity analysis method for detecting trace impurities by sequentially introducing two or more kinds of sample gases into one gas analysis means by repeating.

  The trace impurity analysis method of the present invention preferably further includes a step of purging the introduction path with gas before introducing the sample gas into the gas analysis means.

  According to the present invention, in a trace impurity analyzer capable of performing trace impurity analysis for each sample gas by sequentially introducing a plurality of types of sample gases into one gas analysis means, By providing the decompression means, it is possible to prevent the mixing of different gases into the gas analysis means and improve the analysis accuracy. In addition, according to the present invention, it is possible to prevent foreign gas from being mixed into the gas analysis means, and therefore, the analysis can be performed safely even when the sample gas includes a combination of gas species that may cause danger due to mutual mixing.

  The trace impurity analyzer of the present invention includes a plurality of inflow paths for injecting a sample gas, an introduction path through which the plurality of inflow paths merge, arranged in parallel for each sample gas, and the introduction path One or more gas analysis means connected to each other, and at least two on-off valves in each of the plurality of delivery paths, and a decompression means for decompressing a path between the two on-off valves And by switching the type of the sample gas introduced into the gas analyzing means, two or more types of the sample gases are sequentially introduced into one gas analyzing means.

  Hereinafter, typical aspects of the trace impurity analysis apparatus and trace impurity analysis method according to the present invention will be described with reference to the drawings, but the present invention is not limited thereto. FIG. 1 is a diagram for explaining an example of the configuration of a trace impurity analyzer according to the present invention. In the trace impurity analyzing apparatus having the configuration shown in FIG. 1, the sample gas A supply path 14a including the pressure reducing valve 11a and the open / close valves 12a and 13a, the pressure reducing valve 11b, and the open / close valve 12b are provided as the sample gas supply path. , 13b and the sample gas B feed path 14b are arranged in parallel.

  The feeding paths 14 a and 14 b merge into the introduction path 16, and the introduction path 16 is connected to the gas analysis means 17. Further, pressure reducing means 15 is provided for reducing the pressure between the on-off valve 12a and the on-off valve 13a of the infeed path 14a and between the on-off valve 12b and the on-off valve 13b of the inflow path 14b. On-off valves 15a and 15b are provided between the inlet paths 14a and 14b and the pressure reducing means 15, respectively.

  In the trace impurity analysis apparatus having the configuration shown in FIG. 1, two types of gas analysis means 17 are provided for one gas analysis means 17 by sequentially switching the type of sample gas introduced into the gas analysis means 17 between sample gas A and sample gas B. The sample gas can be sequentially introduced, and the impurity component contained in the sample gas can be detected for each sample gas. Although FIG. 1 shows the case where there are two types of sample gases, the present invention is not limited to this, and three or more types of sample gases may be used. When analyzing three or more kinds of sample gases, the analysis can be performed by sequentially switching the sample gases and sequentially introducing a plurality of kinds of sample gases into one gas analyzing means.

  In the trace impurity analyzing apparatus of the present invention, it is more preferable to switch the type of sample gas introduced into the gas analyzing means while maintaining the gas analyzing means in an operating state. For example, a purge gas feed path is provided separately from the sample gas feed path, and the purge gas is introduced into the gas analyzing means when the sample gas is switched so as not to interrupt the gas supply to the gas analyzing means. can do. That is, in the trace impurity analyzer of the present invention, it is more preferable to provide a purge gas supply path.

  In addition to the sample gas delivery route, if a purge gas delivery route is provided separately, the piping such as the introduction route is purged with the purge gas when the sample gas is switched, and the residual sample gas in the piping can be removed in a shorter time. It is preferable in that it can be performed. In the case where a purge gas feeding path is separately provided, an inert gas such as ultra high purity nitrogen gas or ultra high purity argon gas, or ultra high purity gas of the same gas type as the sample gas may be preferably used as the purge gas.

  The gas analysis means in the trace impurity analyzer of the present invention preferably includes an atmospheric pressure ionization mass spectrometer. The atmospheric pressure ionization mass spectrometer is excellent in impurity detection sensitivity and is a useful means for analyzing trace impurities. Further, it is also preferable that the gas analyzing means comprises an atmospheric pressure ionization mass spectrometer and a gas chromatograph according to the type of sample gas to be analyzed. The combined use of an atmospheric pressure ionization mass spectrometer and a gas chromatograph is useful when analyzing a plurality of substances that are difficult to be separated and detected by any one of the gas analysis means.

  Examples of the sample gas analyzed in the present invention include, for example, a gas supplied as a raw material gas in various processes in the semiconductor field and the like, such as nitrogen gas, oxygen gas, argon gas, helium gas, hydrogen gas, and carbon dioxide gas. Is exemplified. Further, typically, for example, combinations of two or more selected from nitrogen gas, oxygen gas, argon gas, helium gas, and hydrogen gas are exemplified. Since the trace impurity analyzer of the present invention can prevent mixing of different kinds of sample gases, it is a combination of gas species that causes danger when mixed, such as a combination of oxygen gas and hydrogen gas. However, it is possible to sequentially perform analysis by switching the gas species introduced into the gas analysis means while maintaining high safety.

  The trace impurity analyzer of the present invention is preferably operated by a fully automatic system according to a preset program. In the present invention, when the gas analyzing means is continuously operated without stopping, a fully automatic system can be constructed relatively easily. By adopting a fully automatic system, the problem of variation in gas analysis results due to human operation and the problem of safety during operation are solved.

  In the trace impurity analyzer of the present invention, it is preferable to provide a pressure monitoring means for measuring in real time the pressure of the path depressurized by the decompression means. In the trace impurity analyzer of the present invention, for sample gases other than the sample gas being analyzed, the pressure of the sample gas in the introduction path or under analysis is maintained by maintaining at least a part of each inlet path in a reduced pressure state. The structure prevents leakage into the delivery path. When the on-off valve leaks in the delivery path, the pressure in the path that is decompressed by the decompression means increases. Therefore, by measuring the pressure in the path in real time by the pressure monitoring means, it is possible to monitor in real time whether the on-off valve in the sending path is leaking. Thereby, the presence or absence of mixing of the sample gas under analysis and the other gas can be confirmed, and the analysis accuracy can be further improved. The pressure monitoring means can be appropriately installed at any part of the path where the pressure is reduced in each of the feeding paths.

  In the trace impurity analyzer of the present invention, a configuration that can reduce the pressure in the vicinity of the confluence of the sample gas delivery path is more preferably employed. In the present invention, the sample gas is introduced into the gas analysis means from the feeding path corresponding to each sample gas via the common introduction path for all the sample gases. Therefore, if the sample gas remains in the vicinity of the confluence of the delivery path, the sample gas before switching may be mixed into the sample gas analyzed after switching the sample gas, which may reduce the analysis accuracy. If the pressure in the vicinity of the confluence of the delivery path is reduced when the sample gas is switched, the residual sample gas in the vicinity of the confluence is removed in a relatively short time, which has the advantage of improved analysis accuracy.

  Furthermore, it is preferable that the trace impurity analyzer of the present invention includes a temperature adjusting means that enables the piping to be maintained at a desired temperature. Specifically, for example, a temperature adjusting means is provided for each inflow path, in the vicinity of the junction of the inflow path, in the introduction path, etc., so that the pipe is kept in a heated state and can be baked. be able to. In particular, when the introduction path is formed by a relatively narrow pipe near the confluence of the inflow path, the outgas from the inner wall of the pipe tends to have a large effect on the analysis results, and this tendency is in contact with multiple types of gases. The longer the route, the more prominent. By providing temperature control means in these pipes and baking the pipes at the time of switching the sample gas, it is possible to remove the residual sample gas in the pipes and release the outgas in a short time. Further, when the gas analysis is performed while the pipe is kept at a relatively low temperature by the temperature adjusting means, the outgas from the inner wall of the pipe during the gas analysis can be suppressed to a low concentration, thereby improving the analysis accuracy. be able to.

  Hereinafter, specific embodiments of the present invention will be described, but the present invention is not limited thereto.

<Embodiment 1>
In the present embodiment, a case will be described in which the sample gas A is first analyzed and then the sample gas B is analyzed using the trace impurity analyzer configured as shown in FIG. First, in order to analyze the sample gas A, the pressure reducing valve 11a and the on-off valves 12a and 13a in the sample gas A feeding path are opened, and the pressure reducing valve 11b and the on-off valve 12b in the sample gas B feeding path 14b are opened. 13b is closed. Further, the on-off valve 15a is closed and 15b is opened (first step). As a result, the sample gas A is introduced from the delivery path 14a through the introduction path 16 into the gas analyzing means 17, while the sample gas B is stopped from being fed into the delivery path 14b by closing the pressure reducing valve 11b. (Second step). Here, between the on-off valves 12b and 13b of the delivery path 14b is maintained in a reduced pressure state by the decompression means 15 via the opened on-off valve 15b, so that even if a leak of the decompression valve 11b occurs, Since the pressure between the on-off valves 12b and 13b is maintained lower than the downstream path of the on-off valve 13b, the sample gas B does not pass through the on-off valve 13b, and mixing of the sample gas A and the sample gas B is prevented. Is done. In this state, the impurity concentration in the sample gas A is measured by the gas analyzing means 17 (third step). After the analysis of the sample gas A is completed, the pressure reducing valve 11a and the on-off valves 12a and 13a of the delivery path 14a are closed to stop the introduction of the sample gas A to the gas analyzing means 17, and the on-off valve 15a is opened. The pressure between the on-off valves 12a and 13a is reduced (fourth step). The analysis of the sample gas A is completed by the above first to fourth steps.

  Next, the same operation as in the first to fourth steps is performed for the sample gas B, and the sample gas B is analyzed. The pressure reducing valve 11b and the open / close valves 12b and 13b in the sample gas B feed path 14b are sequentially opened, and the open / close valve 15b is closed. As a result, the sample gas B is introduced into the gas analysis means 17 through the introduction path 16 through the introduction path 14b. Between the on-off valves 12a and 13a of the delivery path 14a, the decompression means 15 is maintained in a decompressed state via the opened on-off valve 15a. Therefore, even if the decompression valve 11a leaks, the on-off valve 12a , 13a is maintained lower than the downstream path of the on-off valve 13a, so that the sample gas A does not pass through the on-off valve 13a, and mixing of the sample gas A and the sample gas B is prevented. In this state, the gas analyzer 17 measures the impurity concentration in the sample gas B. After the analysis of the sample gas B is completed, the pressure reducing valve 11b and the open / close valves 12b and 13b of the delivery path 14b are closed to stop the introduction of the sample gas B into the gas analyzing means 17, and the open / close valve 15b is opened. .

  By repeating the above and sequentially switching the gas introduced into the gas analyzing means 17 between the sample gas A and the sample gas B, the trace impurities contained in the sample gas A and the sample gas B can be analyzed in real time.

  In the present embodiment, when the sample gas A and the sample gas B are sequentially switched and introduced into the gas analyzing means 17, at least a part of the sample gas feeding path that has not been analyzed in real time is in a reduced pressure state. By being maintained, the sample gas being analyzed is not mixed into the feed-in path or the introduction path, and degradation of the analysis accuracy is effectively prevented. As a result, a trace amount of impurities can be analyzed.

<Embodiment 2>
FIG. 2 is a diagram for explaining another example of the configuration of the trace impurity analyzer according to the present invention. In this embodiment, a case where a trace impurity analyzer having the configuration shown in FIG. 2 is used will be described. The microanalyzer shown in FIG. 2 includes a sample gas A feed path 24a provided with a pressure reducing valve 21a and on / off valves 22a and 23a, and a sample gas B feed path provided with a pressure reducing valve 21b and on / off valves 22b and 23b. In addition to 24b, a purge gas C feed path 24c having a pressure reducing valve 21c and on-off valves 22c and 23c is further provided. The inflow paths 24a, 24b, and 24c merge into the introduction path 26, and the introduction path 26 is connected to the gas analysis means 27. Further, between the opening / closing valve 22a and the opening / closing valve 23a of the sending path 24a, between the opening / closing valve 22b and the opening / closing valve 23b of the sending path 24b, and between the opening / closing valve 22c and the opening / closing valve 23c of the sending path 24c. Pressure reducing means 25 for reducing the pressure between each of them is provided, and on-off valves 25a, 25b, and 25c are provided between the feeding paths 24a, 24b, and 24c and the pressure reducing means 25, respectively. In the configuration shown in FIG. 2, the opening / closing valve 28 is connected to the path after the sample gas A feed path 24a and the sample gas B feed path 24b merge and before the purge gas C feed path 24c merges. Further, an on-off valve 29 is provided between the on-off valves 23 a, 23 b, 28 and the pressure reducing means 25.

  The procedure of gas analysis in the present embodiment will be described below in the case where sample gas A is first analyzed and then sample gas B is analyzed. First, in order to analyze the sample gas A, the pressure reducing valve 21a and the on-off valves 22a and 23a in the sample gas A feeding path are opened, and the pressure reducing valve 21b and the on-off valve 22b in the sample gas B feeding path 24b are opened. 23b, and the pressure reducing valve 21c and the on-off valves 22c and 23c in the purge gas C feed path 24c are closed. The on-off valve 25a is closed and the on-off valves 25b and 25c are opened (first step). As a result, the sample gas A is introduced from the delivery path 24a through the introduction path 26 to the gas analyzing means 27, while the sample gas B and the purge gas C are supplied to the delivery paths 24b and 24c by closing the pressure reducing valves 21b and 21c. Delivery is stopped (second step). Here, between the on-off valves 22b and 23b of the delivery path 24b and between the on-off valves 22c and 23c of the delivery path 24c are maintained in a decompressed state by the decompression means 25 via the opened on-off valves 25b and 25c. Therefore, even if a leak occurs in the pressure reducing valves 21b and 21c, the pressure between the on-off valves 22b and 23b and between the on-off valves 22c and 23c is lower than the paths downstream of the on-off valves 23b and 23c, respectively. Therefore, the sample gas B and the purge gas C do not pass through the on-off valves 23b and 23c, and mixing of the sample gas A and the sample gas B or the purge gas C is prevented. In this state, the impurity concentration in the sample gas A is measured by the gas analyzing means 27 (third step). After the analysis of the sample gas A is completed, the pressure reducing valve 21a and the on-off valves 22a and 23a in the sample gas A delivery path 24a are closed to stop the introduction of the sample gas A into the gas analyzing means 27, and then the purge gas The pressure reducing valve 21c and the on-off valves 22c and 23c in the C feeding path 24c are opened, the on-off valve 25c is closed, and the purge gas C is introduced into the gas analyzing means 27 through the introduction path 26. Further, the on-off valve 25a is opened, and the pressure between the on-off valves 22a, 23a is reduced (fourth step).

  In the present embodiment, an on-off valve 29 is provided between the on-off valves 23a, 23b, 28 and the decompression means 25, and when purging with the purge gas C, the on-off valve 29 is opened, and the on-off valves 23a, 23a, The sample gas A remaining between 23 b and the on-off valve 28 can be removed by the decompression means 25. This prevents mixing of the sample gas remaining in the pipe with the sample gas to be analyzed next. Thereafter, the on-off valve 29 is closed, and the pressure reducing valve 21c and the on-off valves 22c, 23c in the purge gas C feed path 24c are closed, the on-off valve 25c is opened, and the pressure between the on-off valves 22c, 23c is also reduced. The analysis of the sample gas A is completed by the above procedure.

  Next, the same operation as in the first to fourth steps is performed for the sample gas B, and the sample gas B is analyzed. The pressure reducing valve 21b and the open / close valves 22b and 23b in the sample gas B feed path 24b are sequentially opened, and the open / close valve 25b is closed. As a result, the sample gas B is introduced into the gas analyzing means 27 through the introduction path 26 through the introduction path 24b. Since the opening / closing valves 22a and 23a of the delivery path 24a and between the opening / closing valves 22c and 23c of the delivery path 24c are maintained in a reduced pressure state by the decompression means 25 via the opened opening / closing valves 25a and 25c. Even when a leak occurs in the pressure reducing valves 21a and 21c, the pressure between the on-off valves 22a and 23a and between the on-off valves 22c and 23c is maintained lower than the downstream path of the on-off valve 23a and the on-off valve 23c, respectively. The sample gas A and the purge gas C do not pass through the on-off valves 23a and 23c, and mixing of the sample gas A or the purge gas C and the sample gas B is prevented. In this state, the gas analyzer 27 measures the impurity concentration in the sample gas B. After the analysis of the sample gas B is completed, the pressure reducing valve 21b and the open / close valves 22b and 23b of the delivery path 24b are closed to stop the introduction of the sample gas B into the gas analyzing means 27, and the open / close valve 25b is opened. . Thereafter, purging with the purge gas C is performed by the method described above, and the sample gas B remaining in the pipe is removed.

  By repeating the above and sequentially switching the gas introduced into the gas analyzing means 27 between the sample gas A and the sample gas B, the trace impurities contained in the sample gas A and the sample gas B can be analyzed in real time.

  In the present embodiment, when the sample gas A and the sample gas B are sequentially switched and introduced into the gas analyzing means 27, at least a part of the sample gas feeding path that has not been analyzed in real time is in a reduced pressure state. By being maintained, the sample gas being analyzed is not mixed into the feed-in path or the introduction path, and degradation of the analysis accuracy is effectively prevented. As a result, a trace amount of impurities can be analyzed. Further, by flowing the purge gas when switching the sample gas, the sample gas remaining in the pipe can be removed in a shorter time. Further, by continuing to supply the purge gas to the gas analysis means 27 when the sample gas is switched, the gas analysis means 27 can be continuously operated without stopping. On the other hand, the sample gas remaining in the pipe can be removed in a shorter time by reducing the pressure in the vicinity of the confluence of the delivery path during the purge.

<Embodiment 3>
FIG. 3 is a diagram for explaining still another example of the configuration of the trace impurity analyzer according to the present invention. In this embodiment, a case where a trace impurity analyzer having the configuration shown in FIG. 3 is used will be described. The microanalyzer configured as shown in FIG. 3 has a sample gas A feed path 304a having a pressure reducing valve 301a and on / off valves 302a and 303a, and a sample gas B having a pressure reducing valve 301b and on / off valves 302b and 303b. An inlet path 304b and a purge gas C inlet path 304c including on-off valves 302c and 303c are provided. The inflow paths 304 a, 304 b, and 304 c merge into the introduction path 306, and the introduction path 306 is connected to the gas analysis means 307. Further, between the on-off valve 302a and the on-off valve 303a of the inflow path 304a, between the on-off valve 302b and the on-off valve 303b of the inflow path 304b, and between the on-off valve 302c and the on-off valve 303c of the inflow path 304c. Pressure reducing means 305 for reducing the pressure between them is provided, and on-off valves 305a, 305b, and 305c are provided between the feeding paths 304a, 304b, and 304c and the pressure reducing means 305, respectively.

  In the trace impurity analyzing apparatus having the configuration shown in FIG. 3, the sample gas A feeding path 304a and the sample gas B feeding path 304b are merged and before the purge gas C feeding path 304c is merged. An on-off valve 308 is provided in the path, and an on-off valve 309 is provided between the on-off valves 303 a, 303 b, 308 and the pressure reducing means 305. By opening the on-off valve 309 when the sample gas is switched, the vicinity of the confluence of the inflow path 304a and the inflow path 304b can be in a reduced pressure state, so that the residual sample gas in the vicinity of the confluence is relatively short. Can be removed.

  Further, in the trace impurity analyzer configured as shown in FIG. 3, the purge path 310 is provided, and the purge gas C can be exhausted from the purge path 310 to the outside of the system via the inlet path 304c and the introduction path 306. Further, temperature adjusting means 311 and 312 are provided in the vicinity of the junction of the sample gas A feed path 304a and the sample gas B feed path 304b and the introduction path 306, respectively.

  In the trace impurity analyzer configured as shown in FIG. 3, it is also preferable that the inner diameters of the pipes of the purge gas C feeding path 304c, the introduction path 306, and the purge path 310 are larger than the inner diameters of the pipes of the sample gas feeding path. . In this case, the purge gas is supplied from the feed path 304c to the purge path 310 via the introduction path 306 when switching the type of the sample gas without imposing a load on the gas analysis means 307 or affecting the analysis accuracy of the sample gas. C can be purged at a high flow rate. Thereby, the residual sample gas in the introduction path 306 is removed in a shorter time, and the time required for switching the sample gas can be shortened.

  In the configuration shown in FIG. 3, the purge gas C can be introduced into the gas analysis means 307 when the sample gas is switched. In this case, the supply of gas to the gas analysis means 307 is not interrupted even during the purge. Therefore, it is possible to switch the sample gas while maintaining the gas analyzing means 307 in the operating state.

  The procedure of gas analysis in the present embodiment will be described below in the case where sample gas is analyzed first and then sample gas B is analyzed. First, in order to analyze the sample gas A, the pressure reducing valve 301a and the on-off valves 302a and 303a in the sample gas A feeding path are opened, and the on-off valves 302b and 303b in the sample gas B feeding path 304b are opened. The on-off valves 302c and 303c in the purge gas C feed path 304c are closed. The on-off valve 305a is closed and the on-off valves 305b and 305c are opened (first step). As a result, the sample gas A is introduced from the delivery path 304a through the introduction path 306 to the gas analyzing means 307, while the sample gas B and the purge gas C are fed into the delivery path 304b by closing the pressure reducing valve 301b and the on-off valve 302c. , 304c is stopped (second step). Here, between the on-off valves 302b and 303b of the sending-in route 304b and between the on-off valves 302c and 303c of the sending-in route 304c are maintained in a decompressed state by the decompressing means 305 via the opened on-off valves 305b and 305c. Therefore, even if a leak occurs in the pressure reducing valve 301b and the on-off valve 302c, the pressure between the on-off valves 302b and 303b and the pressure between the on-off valves 302c and 303c are paths downstream of the on-off valves 303b and 303c, respectively. In order to be kept lower, the sample gas B and the purge gas C do not pass through the on-off valves 303b and 303c, and mixing of the sample gas A and the sample gas B or the purge gas C is prevented. In this state, the impurity concentration in the sample gas A is measured by the gas analyzing means 307 (third step). After the analysis of the sample gas A is completed, the pressure reducing valve 301a and the open / close valves 302a and 303a in the sample gas A feed path 304a are closed to stop the feed of the sample gas A, and then the purge gas C feed path The on-off valves 302c and 303c in 304c are opened, and the on-off valve 305c is closed. Further, the on-off valve 305a is opened, and the pressure between the on-off valves 302a and 303a is reduced (fourth step). In the present embodiment, the purge gas C is not introduced into the gas analysis means 307 but is exhausted from the purge path 310 to the outside of the system. As a result, the purge gas can flow through the introduction path 306 at a large flow rate, so that the residual sample gas in the introduction path 306 can be removed in a shorter time, and the time required for switching the sample gas can be shortened.

  In the present embodiment, the on-off valve 309 is also opened thereafter, and the sample gas A remaining between the on-off valves 303a and 303b and the on-off valve 308 is removed by the decompression means 305. Thereby, mixing of the sample gas remaining in the pipe and the sample gas to be analyzed next is prevented. Thereafter, the on-off valve 309 is closed, and the on-off valves 302c and 303c in the purge gas C feed path 304c are closed, the on-off valve 305c is opened, and the pressure between the on-off valves 302c and 303c is reduced. The analysis of the sample gas A is completed by the above procedure.

  The trace impurity analyzer configured as shown in FIG. 3 includes temperature adjusting means 311 and 312. In the present embodiment, when purging the introduction path 306 with the purge gas C, the vicinity of the junction of the introduction path 304a and the introduction path 304b and the introduction path 306 are baked by the temperature adjusting means 311 and 312 respectively. Also good. By performing the baking, the sample gas remaining in the vicinity of the junction and in the introduction path 306 can be removed in a shorter time. As the baking conditions, for example, a condition in which the purge gas is a high purity nitrogen gas, the flow rate is 60 Nl / min, the baking temperature is 50 ° C., and the purge time is 20 hours can be employed.

  Next, the same operation as in the first to fourth steps is performed for the sample gas B, and the sample gas B is analyzed. The pressure reducing valve 301b and the open / close valves 302b and 303b in the sample gas B feed path 304b are sequentially opened, and the open / close valve 305b is closed. As a result, the sample gas B is introduced into the gas analyzing means 307 through the introduction path 304b and the introduction path 306. Since the opening / closing valves 302a and 303a of the delivery path 304a and between the opening and closing valves 302c and 303c of the delivery path 304c are maintained in a reduced pressure state by the decompression means 305 via the opened opening / closing valves 305a and 305c, Even when the pressure reducing valve 301a and the on-off valve 302c leak, the pressure between the on-off valves 302a and 303a and between the on-off valves 302c and 303c is maintained lower than the paths downstream of the on-off valves 303a and 303c, respectively. Therefore, the sample gas A and the purge gas C do not pass through the on-off valves 303a and 303c, and mixing of the sample gas A or the purge gas C and the sample gas B is prevented. In this state, the gas analyzer 307 measures the impurity concentration in the sample gas B. After the analysis of the sample gas B is completed, the pressure reducing valve 301b and the open / close valves 302b and 303b of the delivery path 304b are closed to stop the introduction of the sample gas B into the gas analyzing means 307, and the open / close valve 305b is opened. . Thereafter, purging with the purge gas C is performed by the method described above, and the sample gas B remaining in the pipe is removed.

  By repeating the above and sequentially switching the gas introduced into the gas analysis means 307 between the sample gas A and the sample gas B, the trace impurities contained in the sample gas A and the sample gas B can be analyzed in real time.

  In the present embodiment, when the sample gas A and the sample gas B are sequentially switched and introduced into the gas analyzing means 307, at least a part of the sample gas feeding path that has not been analyzed in real time is in a reduced pressure state. By being maintained, the sample gas being analyzed is not mixed into the feed-in path or the introduction path, and degradation of the analysis accuracy is effectively prevented. As a result, a trace amount of impurities can be analyzed. Furthermore, by providing the purge path, the purge gas can be flowed at a large flow rate when the sample gas is switched, and in this case, the sample gas remaining in the pipe can be removed in a shorter time. In addition, the sample gas remaining in the pipe can be removed in a shorter time by reducing the pressure in the vicinity of the confluence of the plurality of sample gas feed paths during the purge.

<Example>
EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

Example 1
When the sample gas A is hydrogen gas, the sample gas B is argon gas, and the purge gas C is nitrogen gas, after the analysis of the hydrogen gas, the nitrogen gas is purged and argon is used. The purge time until gas switching was possible was evaluated. As the gas analysis means 27, API-MS (atmospheric pressure ionization mass spectrometer) (“UG510-II special type” manufactured by Renesas Technology) was used. In this example, SUS316L-EP 1/8 size (diameter 3.2 mm) and 1/4 size (diameter 6.35 mm) pipes were used for each path.

  The pressure between the open / close valves 22b and 23b of the argon gas feed path and the open / close valves 22c and 23c of the nitrogen gas feed path is reduced, hydrogen gas is fed, and impurities of hydrogen gas are obtained by API-MS. Concentration was measured. Thereafter, the pressure between the on-off valves 22a and 23a of the hydrogen gas feeding path is reduced, the on-off valves 22c and 23c of the nitrogen gas feeding path are opened, and the gas analyzing means passes through the feeding path 24c and the introduction path 26. 27 was purged with nitrogen gas at a flow rate of 12 Nl / min.

  Completion of the purge was confirmed by introducing nitrogen gas via the inlet path 24c and the inlet path 26 into the API-MS as the gas analyzing means 27 and measuring the hydrogen gas concentration in the nitrogen gas. The time required for the nitrogen gas purge in this example was several days until the impurity component analysis value became less than 1 ppb.

(Example 2)
When the sample gas A is hydrogen gas, the sample gas B is argon gas, and the purge gas C is nitrogen gas, the nitrogen gas is purged after the analysis of the hydrogen gas to the argon gas using the trace impurity analyzer shown in FIG. The time required for purging until the changeover was enabled was evaluated. As the gas analysis means 307, API-MS (atmospheric pressure ionization mass spectrometer) of the same model as in Example 1 was used. In the present embodiment, the same 1/4 size (diameter 6.35 mm) pipe as that used in the first embodiment is used for the delivery path 304c, the introduction path 306, and the purge path 310, and the other paths are used. The same 1/8 size pipe (diameter 3.2 mm) as that used in Example 1 was used.

  The pressure between the open / close valves 302b and 303b of the argon gas feed path and the open / close valves 302c and 303c of the nitrogen gas feed path is reduced, hydrogen gas is fed, and the API-MS Impurity concentration was measured. Thereafter, the pressure between the on-off valves 302a and 303a of the hydrogen gas feeding path is reduced, the on-off valves 302c and 303c of the nitrogen gas feeding path are opened, and the feeding path 304c, the introduction path 306, and the purge path 310 are opened. Then, nitrogen gas was purged at a flow rate of 60 Nl / min. Further, from the start to the end of the purge, the temperature adjusting means 311, 312 baked the vicinity of the confluence of the feed path and the introduction path 306 at 50 ° C.

  Completion of the purge was confirmed by introducing nitrogen gas via the feed path 304c and the introduction path 306 into the gas analysis means 307 and measuring the hydrogen gas concentration. The time required for the nitrogen gas purge in this example was one day until the impurity component analysis value became less than 1 ppb.

(Example 3)
Using the trace impurity analyzer of the configuration shown in FIG. 3, coil tube piping immediately after purchase, that is, coil tube piping that has not been baked, was attached as each inflow path, and the outgas concentration was evaluated. As the coil tube piping, KUZE SUS316L-EP1 / 4 (diameter 6.35 mm) 1.0 t × 28 m was used.

  Argon gas was fed from the feeding path A, introduced into the gas analysis means 307 via the introduction path 306, and the concentrations of hydrogen gas and water in the argon gas were measured as outgas concentrations. As a gas analysis means, API-MS of the same model as in Example 1 was used. The results are shown in Table 1.

Example 4
The same operation as in Example 3 was performed except that stainless steel piping (KUZE SUS316L-EP 1/4 1.0 t × 28 m coil tube piping) that had been baked in advance was used for each delivery route. Hydrogen gas and water concentrations were measured as outgas concentrations. The baking was performed at 350 ° C. for 24 hours while purging purified argon gas having a moisture content of 0.2 to 0.5 ppb. The results are shown in Table 1.

  From the results of Examples 1 and 2, according to the trace impurity analyzer of the present invention, even if the switching cycle of the sample gas introduced into the gas analyzing means is relatively short, the error of the impurity component analysis value is 1 ppb. It can be seen that the following excellent analysis accuracy can be obtained. Furthermore, from the results of Example 2, when the purge gas is flowed at a large flow rate when the sample gas is switched, and the vicinity of the confluence of the feeding path is baked at the time of purging, the removal efficiency of the residual sample gas in the pipe is further improved. I understand that

  From the results shown in Table 1, in Example 4 using piping that had been baked in advance, the hydrogen gas and water concentrations in the argon gas were less than 2.0 hours after the start of the transfer. The concentration is restored. Therefore, it can be seen that, when a pipe baked in advance in the present invention is used as an inflow path, outgas from the inner wall of the pipe is prevented from being mixed into the sample gas, and the analysis accuracy is further improved.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The trace impurity analysis apparatus and trace impurity analysis method of the present invention can be suitably applied to various uses that require supply of a source gas with stable purity, such as a semiconductor manufacturing process.

It is a figure explaining an example of the composition of the trace impurity analysis device concerning the present invention. It is a figure explaining another example of the structure of the trace impurity analyzer which concerns on this invention. It is a figure explaining the further another example of the structure of the trace impurity analyzer which concerns on this invention. It is a figure explaining an example of the composition of the conventional impurity analyzer. It is a figure explaining another example of the structure of the conventional impurity analyzer.

Explanation of symbols

  11a, 11b, 21a, 21b, 21c, 301a, 301b, 41a, 41b, 51a, 51b Pressure reducing valve, 12a, 12b, 13a, 13b, 15a, 15b, 22a, 22b, 22c, 23a, 23b, 23c, 25a, 25b, 25c, 28, 29, 302a, 302b, 302c, 303a, 303b, 303c, 305a, 305b, 305c, 308, 309, 42a, 42b, 52a, 52b On-off valve, 14a, 14b, 24a, 24b, 24c, 304a, 304b, 304c, 43a, 43b, 53a, 53b Inlet path, 15, 25, 305 Pressure reducing means, 16, 26, 306, 54 Inlet path, 17, 27, 307, 44, 55 Gas analyzing means, 310 Purge Path, 311, 312 Temperature adjustment means.

Claims (2)

A trace impurity analysis method for detecting, for each sample gas, an impurity component contained in each of a plurality of types of sample gases,
Each of the sample gases is arranged in parallel, each of which is provided with a plurality of feeds for feeding a sample gas, each of which is provided with at least two on-off valves and a decompression means for decompressing a path between the two on-off valves. Of the inlet paths, the on-off valves in the inlet paths other than the first inlet path for feeding the first sample gas are closed to reduce the path between the on-off valves, and the first A first step of opening the two on-off valves in one delivery path and feeding the first sample gas into the first delivery path;
A second step of introducing the first sample gas into the gas analysis means via an introduction path where the plurality of delivery paths merge;
A third step of detecting trace impurities contained in the first sample gas by the gas analyzing means;
A fourth step of closing the two on-off valves in the first delivery path and reducing the path between the on-off valves;
Except that the type of the sample gas introduced into the gas analyzing means is changed by sequentially switching the feeding path in which the on-off valve is opened in the first step to another feeding path. A trace impurity analysis method for detecting trace impurities by sequentially introducing two or more kinds of the sample gases into one gas analysis means by repeating the same operation as in the four steps. The trace impurity analysis method according to claim 1 , further comprising a step of purging the introduction path with a gas before introducing the sample gas into the gas analysis means.

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