JP2003066019A - Method and device for analyzing metallic carbonyl compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device capable of accurately analyzing a metallic carbonyl compound in a condition in which it is coexisting with carbon monoxide, just like the metallic carbonyl compound in carbon monoxide. SOLUTION: This method is to analyze a metallic carbonyl compound in a measuring object gas containing carbon monoxide. After collecting the metallic carbonyl compound by passing the measuring object gas in a collecting pipe 11 cooled down to -150--190 deg.C, the metallic carbonyl compound is lead out by raising the temperature of the collecting pipe to 20-30 deg.C, and is analyzed by bringing it into an analyzer 12 using an infrared absorption spectrometer by vacuum-sucking it with a vacuum pump 17.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method and an apparatus for analyzing a metal carbonyl compound, and more particularly to a method and an apparatus for analyzing a metal carbonyl compound present in carbon monoxide used in an etching process in the semiconductor industry. .

[0002]

2. Description of the Related Art Since carbon monoxide has a high reactivity with metals, it reacts with a metal material of a pipe for supplying carbon monoxide as a high pressure gas to produce various metal carbonyl compounds. It is known.
In recent years, carbon monoxide has been used for dry etching in the semiconductor manufacturing process. However, when a metal carbonyl compound is present in carbon monoxide, the metal carbonyl compound contaminates the wafer and impairs the function of the device. Will be given. Therefore, when carbon monoxide is used in the semiconductor industry, it is necessary to remove the metal carbonyl compound, which requires highly sensitive analysis of the metal carbonyl compound in carbon monoxide.

Infrared spectroscopy is generally used for the analysis of metal carbonyl compounds. However, the infrared absorption wave number range of the metal carbonyl compound is 2000 to 2100 cm.
It is in the vicinity of ^-1 , and absorption of carbon monoxide as the main component becomes an interference peak. Therefore, when measuring a metal carbonyl compound in the state of coexisting with carbon monoxide, there is a problem that it is difficult to analyze a trace amount of the metal carbonyl compound because the absorptions of the both overlap.

Therefore, in order to analyze a metal carbonyl compound in carbon monoxide by infrared analysis with high sensitivity, it is necessary to separate carbon monoxide and metal carbonyl in advance, but most of the metal carbonyl compounds. Since it is unstable and easily decomposed, if an attempt is made to separate the resinous material containing a large amount of water and various column materials such as those used in gas chromatographs from each other, the metal carbonyl compound is decomposed and accurate analysis cannot be performed.

A method is also conceivable in which carbon monoxide is bubbled in an acidic chemical solution to recover a metal carbonyl compound in the solution and the metal components in the solution are analyzed by a metal analyzer such as a plasma mass spectrometer. The recovery efficiency of the metal carbonyl compound in the liquid is not clear, and there is a problem in terms of accuracy.

Therefore, the present invention provides a method and apparatus capable of accurately and highly sensitively analyzing a metal carbonyl compound in the state of coexisting with carbon monoxide, such as a metal carbonyl compound in carbon monoxide. Has an aim.

[0007]

In order to achieve the above object, a method for analyzing a metal carbonyl compound of the present invention is a method for analyzing a metal carbonyl compound in a gas to be measured containing carbon monoxide, the method comprising: The target gas is circulated through the cooled collecting tube to collect the metal carbonyl compound, and then the temperature of the collecting tube is raised to derive the metal carbonyl compound from the collecting tube, and the metal carbonyl compound is introduced into an analyzer for analysis. It is characterized by doing.

Further, in the method for analyzing a metal carbonyl compound of the present invention, the temperature of the collection tube when collecting the metal carbonyl compound is -150 to -190 ° C., and the collection tube for the metal carbonyl compound is The temperature of the collection tube when it is discharged from the collection tube is 20 to 30 ° C., the operation of drawing the metal carbonyl compound from the collection tube and introducing it into the analyzer is performed by vacuum suction, and the analyzer is red. It is characterized by being an external absorption analyzer.

Further, the apparatus for analyzing a metal carbonyl compound according to the present invention comprises a collecting tube through which a gas to be measured containing carbon monoxide and a metal carbonyl compound flows, cooling means for cooling the collecting tube, and the collecting tube. A temperature raising means for raising the temperature of the tube, an analyzer for analyzing the metal carbonyl compound derived from the collection tube, and a vacuum suction means for guiding the metal carbonyl compound from the collection tube to the analyzer are provided. It is characterized by being.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a systematic diagram showing an example of an embodiment of an analyzer for metal carbonyl compounds of the present invention. This analyzer includes a collection tube 11 for collecting a metal carbonyl compound, and an analyzer 12 for analyzing the metal carbonyl compound collected by the collection tube 11. The collecting pipe 11 is made of metal such as stainless steel, copper, brass, aluminum, etc., having a diameter of 1/16 inch to 1/4 inch and a length of 1 to 5 m. The collection tube 11 is housed in a coil shape in a heat insulating container 13 into which a coolant for cooling the collection tube 11 is introduced. The downstream side of the collection tube 11 is an analyzer 12
To an exhaust path 16 provided with a flow meter 15, and a vacuum pump 1 for guiding gas from the collection pipe 11 to the analyzer 12 is provided downstream of the analyzer 12.
7 is provided.

As the analyzer 12, any analyzer can be used as long as it can analyze a metal carbonyl compound, and infrared laser spectroscopy or the like can also be used. For example, Jacksier et al. Proposed calibration curve creation method (EP 0960856 (199
The infrared absorption analyzer by infrared spectroscopy described in 9)) is most suitable.

The heat insulating container 13 is provided with a refrigerant introduction path 18 and a refrigerant exit path 19 for introducing and discharging a cooling refrigerant, and heating means for raising the temperature of the collection tube 11 to a predetermined temperature. For example, an electric heater 20 is provided. Any refrigerant may be used as the cooling medium for cooling the collection tube 11, and the temperature at which the metal carbonyl compound can be collected in the collection tube 11 and the carbon monoxide is hardly collected. It only needs to be cooled.

Specifically, when the collection tube 11 is cooled to a temperature lower than -190 ° C, the boiling point of carbon monoxide (-19
(1.5 ° C.), carbon monoxide is also trapped in the collection tube 11 together with the metal carbonyl compound, and the two cannot be separated, and if the temperature is higher than −150 ° C., the vapor pressure rises. Since the metal carbonyl compound cannot be collected sufficiently, it is desirable to use a refrigerant that can be cooled in the temperature range of -150 to -190 ° C. Liquid argon having a boiling point of about −186 ° C. is optimal as such a refrigerant, and the collection tube 11 can be stably maintained in a cooled state at about −185 ° C.

In the low temperature trap in the usual concentration analysis method, various fillers are filled in the collection tube 11 in order to improve the trapping performance. Such a filler is used. Then, the metal carbonyl compound trapped by the water content contained in the packing material may be decomposed and accurate analysis may not be performed.

On the other hand, the heating temperature of the collecting tube 11 is 20 to 3
0 ° C. is suitable, and when the temperature is raised to 30 ° C. or higher, the metal carbonyl compound may be decomposed, or the remaining trace amount of carbon monoxide may react with the piping material to generate a new metal carbonyl compound. . If the heating temperature is low, it may take a long time to sufficiently desorb the collected metal carbonyl compound. As the heating means, any means other than the electric heater 20 can be used, and a gas or a liquid having an appropriate temperature is introduced into the heat insulating container 13 by using the refrigerant introduction path 18 and the refrigerant discharge path 19. It is also possible to introduce it to raise the temperature of the collection tube 11, and to use this together with an electric heater.

The vacuum pump 17 is used to introduce the metal carbonyl compound into the analyzer 12 in the highest possible concentration, but the collection tube 11 in the state where the metal carbonyl compound is collected is brought to the cooling temperature. By vacuuming the inside of the collection tube 11 with the vacuum pump 17 in the held state, carbon monoxide can be excluded from the path from the collection tube 11 to the analyzer 12, and therefore the analysis of the metal carbonyl compound can be performed. The accuracy can be further improved. When the temperature of the collection tube 11 is raised and the metal carbonyl compound is sent to the analyzer 12 without using the vacuum pump 17 or in combination, a gas that does not affect the analysis of the metal carbonyl compound is collected. The analyzer 12 is circulated in the collecting pipe 11.
You can also send it to.

Next, a procedure for analyzing a metal carbonyl compound contained in a trace amount in the gas to be measured using the analyzer shown in this embodiment will be described. First, after sufficiently purging the inside of the system, a refrigerant is introduced into the heat insulating container 13 to cool the collection tube 11. At this time, the collection tube 11 can be cooled to about −185 ° C. by using liquid argon as the refrigerant. In this state, the analysis valve 21 is closed and the inlet valve 22,
The outlet valve 23 and the exhaust valve 24 are opened, and the gas to be measured, for example, high-purity carbon monoxide is introduced from the inlet valve 22 to collect the gas.
The gas amount is precisely measured while controlling the flow rate by using a flow meter 15, for example, a mass flow controller, while making the gas flow to 1.

After passing a predetermined amount of gas to be measured, the inlet valve 22 and the exhaust valve 24 are closed, the analysis valve 21 and the suction valve 25 are opened, the vacuum pump 17 is operated, and the pressure is checked by the pressure gauge 26. While vacuuming the system. By performing such vacuum evacuation to evacuate the portion of the collection pipe 11 to 1 Torr or less, preferably 0.1 Torr or less, components other than the metal carbonyl compound collected in the collection pipe 11, particularly one Carbon oxide can be sufficiently removed from the path from the collection tube 11 to the analyzer 12.

Then, the refrigerant is discharged from the heat insulating container 13 to introduce hot water and the like, and the heater 20 is operated.
By heating the collection tube 11 to about 30 ° C., the metal carbonyl compound collected in the collection tube 11 is vaporized and introduced into the analyzer 12, for example, the gas cell 12a of the infrared absorption analyzer. As a result, the metal carbonyl compound introduced into the gas cell 12a can be quantitatively analyzed by the analysis operation of the analyzer 12, and the content of the metal carbonyl compound in the measurement target gas can be calculated from the amount of gas measured by the flow meter 15. You can ask.

The main object of the present invention is to analyze a metal carbonyl compound in carbon monoxide used in an etching process in the semiconductor industry with high accuracy and high sensitivity. A component which does not adversely affect the collection of the metal carbonyl compound in 11 or does not adversely affect the analysis of the metal carbonyl compound in the analyzer 12 may be contained, and in a gas containing such a component as a main component. When carbon monoxide and a metal carbonyl compound coexist in
For example, it can be applied to analysis of a metal carbonyl compound when carbon monoxide and a metal carbonyl compound coexist in nitrogen gas.

[0021]

[Example] Nickel carbonyl in carbon monoxide was analyzed by using the analyzer having the configuration shown in FIG. As the collecting pipe 11, 1/16 inch pipe made of stainless steel (SUS316L) was used for 2 m. Liquid argon was used as the coolant to set the cooling temperature of the collection tube 11 to −185 ° C., and warm water was used to raise the temperature of the collection tube 11 to 30 ° C.
An infrared absorption spectrometer (FT-IR) was used for the analyzer 12, and a stainless steel optical path length of 10 m was used for the gas cell 12a.

The collection tube 11 is cooled to -185 ° C., the analysis valve 21 is closed, the inlet valve 22, the outlet valve 23 and the exhaust valve 24 are opened, and the flow rate of the gas to be measured is measured by a flow meter (mass flow controller) 15 It was adjusted to 2000 sccm and circulated for 20 minutes. Therefore, the sampling gas amount is 40 liters.

Next, the inlet valve 22 and the exhaust valve 24 were closed, the analysis valve 21 and the suction valve 25 were opened, and the system was evacuated to 0.1 Torr by the vacuum pump 17. further,
The outlet valve 23 is closed and the gas cell 12a is set to 0.001 Torr.
It was evacuated below r. Collection tube 1 at the same time as this vacuum exhaust
The heating of No. 1 was started, and the temperature of the collection tube 11 was raised to 30 ° C.
Then, the suction valve 25 is closed and the outlet valve 23 is opened to introduce the components collected in the collection pipe 11 into the gas cell 12a,
The components in the gas cell 12a were measured.

First, carbon monoxide (purified gas) from which nickel carbonyl was sufficiently removed by low-temperature purification at liquid nitrogen temperature was used as a gas to be measured, and nickel carbonyl was analyzed by the above procedure. Next, a mixed gas was prepared by adding 3.5 ppb of nickel carbonyl to the same carbon monoxide, and nickel carbonyl was analyzed by the same procedure. The spectra obtained by both analyzes are shown in FIG. From this result, it is found that the absorption peak of nickel carbonyl appears without being affected by the interference peak in the spectrum obtained by adding nickel carbonyl.

Next, with the amount of sampling gas fixed, the gas flow rate during sampling was changed from 50 sccm to 45
It was changed to 0 sccm. The change in absorbance of the nickel carbonyl spectrum at this time is shown in FIG. Also, the gas flow rate is fixed at 300 sccm and the sampling time is changed to change the sampling gas amount from 600 cc to 6900 c.
It was changed to c (6.9 liters). The change in absorbance of the nickel carbonyl spectrum at this time is shown in FIG.

Further, a blank signal was confirmed and a calibration curve was prepared. In the experiment, a product having a carbon monoxide balanced nickel carbonyl concentration of 125 ppb was used. Table 1 shows a summary of the measurement results. In the table, L is liter.

[0027]

[Table 1]

The intensity of the blank signal is 0.
It was 0002. The extinction coefficient of nickel carbonyl is
It tended to be slightly lower when the sampling amount was low, but a constant value was obtained in almost all areas. When the sampling amount was 5 liters or more, the extinction coefficient was 0.00012 and the correlation coefficient was 0.9989 by the least squares method.
The obtained extinction coefficient and the noise intensity of the blank, and the lower limit of detection (2S /
N) was found to be 0.7 ppb. 0.1 ppb
It was found that the sampling amount should be 33 L in order to obtain the sensitivity of.

From the results of this experiment, it can be judged that the method of the present invention can analyze the metal carbonyl compound in carbon monoxide without loss and without generating it in the apparatus.

[0030]

As described above, according to the present invention,
It is possible to analyze metal carbonyls in pure carbon monoxide simultaneously in multiple components, and it is possible to analyze metal carbonyls while carbon monoxide remains undestructed. In addition, the analysis operation is simple,
It is efficient. Further, by changing the sampling gas amount and the optical path length of the gas cell, it is possible to greatly change the detection sensitivity.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of a mode of an analyzer for metal carbonyl compounds of the present invention.

FIG. 2 is a diagram showing a spectrum of a purified gas and a spectrum of a mixed gas in Examples.

FIG. 3 is a diagram showing a change in absorbance of a nickel carbonyl spectrum when a gas flow rate during sampling is changed.

FIG. 4 is a diagram showing a change in absorbance of a nickel carbonyl spectrum when a sampling gas amount is changed.

[Explanation of symbols]

11 ... Collection tube, 12 ... Analyzer, 13 ... Insulation container, 14 ...
Analysis path, 15 ... Flowmeter, 16 ... Exhaust path, 17 ... Vacuum pump, 18 ... Refrigerant introduction path, 19 ... Refrigerant derivation path, 2
0 ... Electric heater

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2G052 AA03 AB01 AC13 AC28 AD02                       AD42 BA02 BA14 BA21 CA02                       CA04 DA13 DA24 EB01 EB11                       EB13 ED03 GA11 JA05 JA09                 2G059 AA01 BB01 CC20 DD12 EE01                       EE10 EE12 HH01 HH06 MM12

Claims (5)

[Claims] 1. A method for analyzing a metal carbonyl compound in a measurement target gas containing carbon monoxide, the measurement target gas being passed through a cooled collection tube to collect the metal carbonyl compound, A method for analyzing a metal carbonyl compound, characterized in that the temperature of the collection tube is raised, the metal carbonyl compound is led out from the collection tube, and introduced into an analyzer for analysis. 2. The temperature of the collection tube when collecting the metal carbonyl compound is −150 to −190 ° C.,
The method for analyzing a metal carbonyl compound, wherein the temperature of the collection tube when the metal carbonyl compound is discharged from the collection tube is 20 to 30 ° C. 3. A method for analyzing a metal carbonyl compound in carbon monoxide, wherein the operation of introducing the metal carbonyl compound from a collection tube and introducing it into an analyzer is performed by vacuum suction. 4. The method for analyzing a metal carbonyl compound in carbon monoxide, wherein the analyzer is an infrared absorption analyzer. 5. A collection pipe through which a gas to be measured containing carbon monoxide and a metal carbonyl compound is circulated, cooling means for cooling the collection pipe, temperature raising means for raising the temperature of the collection pipe, An analyzer for analyzing the metal carbonyl compound derived from the collection tube, and a vacuum suction means for introducing the metal carbonyl compound from the collection tube to the analyzer are provided. Analyzer for metal carbonyl compounds.