JPH046896B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention manages and controls the concentration of oxidizing gas in excimer laser gas in excimer laser generation systems frequently used in the chemical industry, machinery industry, semiconductor industry, etc. The present invention relates to a method and apparatus for measuring the concentration of oxidizing gas, which is essential for this purpose. (Prior art) Conventionally, an excimer laser generation system consists of a mixed gas of an inert gas such as helium, argon, or krypton gas and an oxidizing gas such as fluorine, nitrogen trifluoride, or hydrogen chloride gas. Excimer laser gas is not recycled and is often discharged after a certain period of use due to deterioration of the gas due to a decrease in the concentration of oxidizing gas. However, it still contains a considerable amount of useful gas, and in order to reduce costs, or because the excimer laser gas contains harmful gases such as fluorine gas, pollution treatment equipment is required to discharge them. In such cases, it has been desired to recycle the excimer laser gas. Attempts have been made to recycle the gas in a small number of cases, and in this case, it is necessary to measure the concentration of the oxidizing gas in order to replenish the oxidizing gas that has been consumed or decreased in the system. Chemical analysis, gas chromatography, etc. have been adopted as means for this purpose, but these have the following problems. (Problems to be solved by the present invention) In an excimer laser generation system, oxidizing gas,
For example, since the fluorine gas decreases and the laser output decreases accordingly, it is desirable to always maintain the fluorine gas concentration at the set value by replenishing the fluorine gas. However, when using gas chromatography, let alone chemical analysis, analysis takes a long time, at least 30 minutes, and in the case of fluorine gas, which is extremely corrosive, it causes wear and tear on the gas chromatography equipment. Because it requires an operation to convert it into a less corrosive fluoride and submit it to gas chromatography, the concentration of fluorine gas must be set at the set value because the actual fluorine gas has been reduced even further by the time the analysis results are obtained. It was impossible to maintain it. In addition, these analytical means are complicated to operate and require skill, and the analytical equipment is large and expensive, making it impossible for even unskilled personnel to perform measurements quickly, easily, and accurately. On the other hand, gas measuring methods and devices using chemiluminescence have been known for some time. For example, in Japanese Patent Application Laid-Open No. 48-29492 (hereinafter referred to as the conventional example), a transparent plate is placed in contact with the tube of a photomultiplier tube, and a base plate is placed in contact with the transparent plate. A shallow meandering groove is provided on the contacting surface, and the gas to be measured is introduced into the groove and reacts with a solid, liquid, or gaseous reactant on the groove, and the resulting chemiluminescence is transferred to the translucent plate. In Japanese Patent Application Laid-open No. 51-60593 (hereinafter referred to as the conventional example), two types of chromatography columns are used to analyze organic gases using ozone. It is possible to separate the above-mentioned gases to be measured, or further to control the temperature to an appropriate temperature by utilizing the difference in reaction temperature of each gas, or to adjust the appropriate wavelength by utilizing the difference in chemiluminescence wavelength due to the reaction of each gas. Detecting and measuring the chemiluminescence of each gas by using a filter that passes through it was disclosed in Japanese Patent Application Laid-Open No. 57-53646.
(hereinafter referred to as the conventional example), holes are evenly distributed to take in the gas to be measured and the reaction gas from around the reaction chamber, and multiple photodiodes for detection are located at specified positions. It is disclosed that it allows None of these conventional examples mentions the measurement of oxidizing gases such as fluorine, nitrogen trifluoride, and hydrogen chloride in excimer laser gas, and in all of them, the gas to be measured is measured from one side of the reaction chamber.
A system that introduces each of the reactant gases while sucking in and discharging the more reacted gas from the other,
In order to maintain the amount of these gases introduced at a constant level, accurate measurements cannot be made unless precise valve operations are performed to balance the introduction and discharge.Also, the amount of gas sampling inevitably increases, making it difficult for measurements to be carried out. This will require an extra amount of gas. In the conventional example, since the reaction occurs in the vicinity of the light-transmitting plate, there is a problem in that the light-transmitting plate is likely to be contaminated by reaction products and the like, which deteriorates measurement accuracy. In the conventional method, gas separation using a column requires a long time, and the addition of columns, heating control means, cooling means, filters, etc. makes the apparatus bulky and complicates operation. Particularly when measuring extremely corrosive excimer laser gas such as fluorine gas, corrosion of parts that come into contact with the gas cannot be avoided, but replacing these parts is time consuming and costly. There are other problems. It is not hard to imagine that in the conventional example as well, it takes time and money to replace corroded members. The present invention solves these problems and provides a quick, easy, and accurate measuring method required for managing excimer laser gas.In addition, the structure is simple and compact, and parts can be replaced quickly and easily. The purpose is to provide a measuring device that can (Means for Solving the Problems) The present invention aims to improve the concentration of an oxidizing gas in an excimer laser gas consisting of a mixed gas of an inert gas and one type of oxidizing gas among fluorine-based or chlorine-based gases. In this method, a reducing gas selected from hydrogen, methane, silicon hydride gas, or a mixture thereof is brought into contact with the excimer laser gas, and the luminescence (chemiluminescence) produced when it chemically reacts with the oxidizing gas is detected. (sensor) and the concentration of oxidizing gas in excimer laser gas, which is a mixture of an inert gas and one type of oxidizing gas from fluorine-based or chlorine-based gases. In the apparatus, a branch pipe is provided in the circulation line of the excimer laser gas, an introduction pipe for collecting a part of the branch pipe, and one end is connected to the introduction pipe,
a reaction vessel sealed with a reducing gas selected from hydrogen, methane, silicon hydride gas, or a mixed gas thereof; a feed pipe for feeding the reducing gas into the reaction vessel; a laser gas introduction side of the reaction vessel; A detection device that detects chemiluminescence generated by the reaction between the oxidizing gas and the reducing gas and converts it into an electrical signal at the other end facing the oxidizing gas, an amplifier that amplifies the electrical signal, and records and stores the amplified signal. It consists of having a recording device. In the present invention, the inert gas in the excimer laser gas mainly refers to rare gases such as helium, neon, argon, krypton gas, etc., and one or more types may be present. The oxidizing gas is fluorine, nitrogen trifluoride, hydrogen chloride gas, etc., and one of them is present in the excimer laser gas. Reducing gases react with oxidizing gases to effectively express chemiluminescence, and are specified for accurate measurement. Hydrogen, methane, silicon hydride,
Alternatively, a mixture of these gases may be used. In the apparatus of the present invention, a branch pipe is provided in the excimer laser gas circulation line to introduce a part of the laser gas, and the gas is further collected and sent through an introduction pipe with a volume of several cc or less to be introduced into the reaction vessel. The excimer laser gas is introduced from one end of a cylindrical container, for example, into a reaction vessel with a volume of several cc to several hundred cc, which is filled with a specific reducing gas at very low pressure introduced from an entry pipe, and the above-mentioned oxidation in the laser gas is carried out. The reactive gas is reacted with the reducing gas, and the chemiluminescence generated during the reaction is transmitted to a photoelectric conversion element, ie, a photodiode, etc. of a detection device through a window provided at the other end of the reaction vessel opposite to the gas inflow end. It detects the electrical signal, amplifies it, records it with a recording device, and discharges the residual gas after the reaction out of the system through an exhaust pipe, and has an extremely simple and compact structure. Furthermore, since the introduction pipe and reaction vessel are made detachable using pipe joints, etc., even if they become worn out, they can be quickly and easily replaced. (Example) An example of implementing the present invention will be described in detail below. In a fluorine-based krypton excimer laser system, the temperature of fluorine gas decreases as it is excited by electron beam irradiation, discharge, etc., and the present invention can be effectively applied to supplying the fluorine gas. FIG. 1 is a schematic diagram showing an example of the apparatus of the present invention. In the figure, 5 is a branch pipe for collecting laser gas from an excimer laser gas circulation line (not shown), and by operating a valve 6, a volume of, for example, 3c is extracted. It is led to the introduction pipe 1 of c. Note that the gas pressure is 2 atmospheres in this example. Reference numeral 7 denotes a pipe for introducing a reducing gas such as silicon hydride gas, and the gas is sealed into the reaction vessel 2 having a volume of 50 c.c., for example, by operating a valve 8. Note that the gas pressure may be as extremely low as about 0.3 Torr (4×10 ⁻⁴ atmospheres). Reference numeral 9 denotes a pipe for discharging waste gas after measurement, and discharge is performed by operating a valve 14. Further, the valve 14 is used to bring the introduction pipe 1 and the reaction vessel 2 under a vacuum of 10 ^-3 Torr before measurement. The mixed gas is supplied to the reaction vessel 2 by operating the valve 10.
The fluorine gas and silicon hydride gas in the mixed gas come into contact with each other and react instantly. Via the window section 11 provided at the other end opposite to the gas inflow end, the signal is detected by the photodiode 3 disposed in contact with or close to the window section 11, converted into an electrical signal, and appropriately amplified by the amplifier 13. ,
The light intensity is recorded on the recorder 4 as a light intensity-time curve as shown in FIG. As described above, the operation is extremely easy, and the results are known within a few seconds after the mixed gas is subjected to measurement. Although the shape of the reaction vessel 2 is not specified, as described above, the window 11 is provided at the other end opposite to the gas inflow end, and the direction of ejection of the inflow gas is aligned with the axis perpendicular to the plane forming the window 11. is the most effective for detecting chemiluminescence. Note that if the gas inflow end and the window 11 are too close to each other, reaction products and the like may contaminate the window 11, impair its light transmittance, and deteriorate the detection accuracy of the photodiode 3. Therefore, depending on the difference between the inflow gas pressure and the silicon hydride gas pressure and the volume of each gas, the distance between the gas inflow end and the window 11 is usually 5.
It is preferable to maintain a distance of at least cm. If aluminum or nickel is used for the introduction pipe 1 or the reaction vessel 2, the inner surface will react with the fluorine gas to form a hard film of aluminum fluoride or nickel fluoride, which will resist the attack of the fluorine gas. However, there will be an extremely large amount of resistance. Similarly, it is preferable to use quartz glass, which has high erosion resistance, for the window portion 11. FIG. 4 is a partially cutaway side view showing the introduction part of the excimer laser gas, in which a valve 6 is attached to the tip of the branch pipe 5, and a removable cylindrical valve is attached by abutting the outlet end of the branch pipe 5 with the starting end of the introduction pipe 1. Similarly, a valve 10 is attached to the terminal end of the introduction pipe 1, and a removable cylindrical coupling 16 is attached by abutting the outflow side end of the valve 10 against the inflow side pipe of the reaction vessel 2. Although not shown, the valve 8,
By butting the pipes together and attaching a cylindrical joint to the reaction vessel side of 14, even if the introduction pipe 1 and the reaction vessel 2 become worn out, they can be easily replaced. The concentration of fluorine gas is proportional to the integrated intensity of the light intensity-time curve shown in the graph of Fig. 2, and the graph of Fig. 3 shows the relationship between the concentration of fluorine gas and the integrated intensity. However, extremely good linearity with respect to concentration changes can be obtained even in the trace amount range of 0.1 to 0.3%. Table 1 shows the measurement accuracy and measurement time of fluorine gas concentration in comparison with a comparative example and a reference example. In the table, Nos. 1 to 3 are according to the present invention, Nos. 5
No. 6 is a comparative example in which ammonia and carbon monoxide are used as reducing gases, and No. 6 is a reference example in gas chromatography. This result shows that in the comparative example, the measurement accuracy is insufficient with an error range of ±6% or more, whereas in the present invention, the measurement accuracy is within an error range of ±2%, which is sufficient for controlling fluorine gas. It exhibits high accuracy and the measurement time is extremely short, within 10 seconds, making it suitable for managing excimer laser gas. In particular, when No. 1 silicon hydride gas is used, measurements can be made with high precision over a range of low to high fluorine concentrations without using any ignition means. On the other hand, when using hydrogen or methane gas, an ignition means such as a filament (indicated by * in the table) as shown in Fig. 12 may be used to measure the low concentration range of fluorine gas. The light intensity of this ignition itself can be excluded by conducting a blank test in advance. When implementing the present invention, the fluorine gas concentration in the excimer laser generation system is measured at regular intervals while replenishing fluorine gas is constantly flowing through the excimer laser generation system, and the amount of replenishing fluorine gas is determined based on the results. It is also possible to adjust the
By doing so, the fluorine gas concentration in the laser generation system is always at the set value,
Optimal laser oscillation conditions can be maintained. In addition, after amplifying the electrical signal from the photodiode by replacing it with the recorder 4, convert it from analog to digital, input it to the microcomputer, and memorize the relationship between fluorine gas concentration and integrated intensity shown in Figure 3 in advance. For example, it is also possible to display the output results as fluorine gas concentration. (Effects of the Invention) As described above, the present invention allows the concentration of the oxidizing gas mixed with the inert gas in the excimer laser gas to be measured quickly, easily, and with high precision, so that the concentration of the oxidizing gas can always be kept at the set value. This has the remarkable effect of making it possible to maintain the excimer laser generation system in an optimal state at all times. Furthermore, the apparatus of the present invention has the advantage that it is simple and compact, does not require any skill to operate, and even if parts such as the introduction pipe or reaction vessel become worn out, they can be quickly replaced, and the cost is low. 【table】

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing an example of the device of the present invention, and Figure 2 is a graph of light intensity versus time recording chemiluminescence due to the reaction between argon gas containing 0.3% fluorine gas and silicon hydride gas. 3 is a graph showing the relationship between the concentration of fluorine gas and the light intensity (integrated intensity), and FIG. 4 is a partially cutaway side view showing the introduction portion of the excimer laser gas. 1...Introduction pipe, 2...Reaction container, 3...Photodiode, 4...Recorder, 13...Amplifier.

Claims (1)

[Claims] 1. A method for measuring the concentration of an oxidizing gas in an excimer laser gas consisting of a mixed gas of an inert gas and an oxidizing gas of one type of fluorine-based or chlorine-based gas, A reducing gas selected from hydrogen, methane, silicon hydride gas, or a mixture thereof is brought into contact with the excimer laser gas, and the light intensity of luminescence (chemiluminescence) generated when it chemically reacts with the oxidizing gas is measured. A method for measuring the concentration of an oxidizing gas. 2. In an apparatus for measuring the concentration of an oxidizing gas in an excimer laser gas consisting of a mixed gas of an inert gas and an oxidizing gas of one type of fluorine-based or chlorine-based gas, the circulation of the excimer laser gas An inlet pipe is provided with a branch pipe in the line to collect a part of the pipe, and one end is connected to the inlet pipe, and a reaction vessel is sealed with a reducing gas selected from hydrogen, methane, silicon hydride gas, or a mixed gas thereof; Detecting chemiluminescence generated by the reaction between the oxidizing gas and the reducing gas at the feed pipe for feeding the reducing gas into the reaction vessel, and at the other end of the reaction vessel opposite to the laser gas introduction side. 1. A device for measuring the concentration of an oxidizing gas, comprising a detection device for converting the oxidizing gas into an electrical signal, an amplifier for amplifying the electrical signal, and a recording device for recording and storing the amplified signal.