JP2906290B2 - Method for measuring metal impurities in gas - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for measuring metal impurities in a gas, and particularly to a method for measuring a trace amount of corrosive gas such as boron trichloride (BCl ₃ ) hydrogen chloride (HCl). The present invention relates to a method for measuring a metal impurity contained in a steel sheet with high accuracy.

[Prior Art] Various gases are used as raw material gases for manufacturing semiconductor devices. Generally, high-purity gases are used as these gases. Among them, gases such as BCl ₃ and HCl are likely to contain metal impurities due to their corrosiveness,
When a gas containing metal is used as a raw material, deterioration of insulating properties is caused when a semiconductor is manufactured. Therefore, when shipping the above gas, the amount of metal impurities is measured, and only those that pass the test are attached with an inspection certificate.

At present, there is no analyzer that directly measures metal impurities in the gas, so that the gas is bubbled in an acid solution such as a dilute hydrochloric acid solution or a dilute nitric acid solution to measure the metal impurities in the gas. After collection, trace metals are added to the solution.
Solution absorption method measured by ICP emission spectrometry or FLAAS analysis (flameless atomic absorption spectrometry), or after collecting metals in a gas with a filter, dissolve the metals collected by the filter into the solution. The method has been performed by any of the filter collection methods measured by the above-mentioned analysis method.

[Problems to be solved by the invention]

However, in the solution absorption method described above, when the gas does not hydrolyze or dissolve in the solution, the gas becomes foamy and passes through the solution. And the metal impurities could not be sufficiently collected. On the other hand, even in the case of a completely hydrolyzed or dissolved gas, for example,
For HCl, HCl becomes strong acid solution dissolved in a solution, there is a disadvantage that reduces the sensitivity of the measurement, also, BCl ₃
In the case of (1), boric acid that is hardly soluble in the solution is generated, which causes an obstacle in measurement, and also causes a disadvantage that the measurement accuracy is deteriorated.

In addition, as a result of various experiments, it has been found that metal impurities in the gas currently supplied to the semiconductor manufacturing field contain fine metals having a particle size of 0.05 μm or less. Therefore, in the filter collection method, it is necessary to collect and measure even a metal having a particle size equal to or smaller than the particle size.However, if the filter is made finer, it becomes difficult to take out the metal collected by the filter into a solution. Similarly, there is a disadvantage that the measurement accuracy is deteriorated.

In view of the above, the present inventors have intensively studied to develop a method capable of measuring metal impurities in a gas with high accuracy.

[Means for solving the problem]

As a result, if the gas containing metal impurities is brought into contact with the porous polymer beads, it is possible to collect fine metal impurities at a much higher rate than in the past and to clean the porous polymer beads on which the metal impurities are adsorbed, It has been found that the trapped metal impurities can be easily taken into the solution and then analyzed by a well-known analysis method. The present invention has been completed based on this finding.

That is, the method for measuring metal impurities in a gas of the present invention comprises contacting a gas containing metal impurities with porous polymer beads to adsorb the metal impurities to the porous polymer beads, and then removing the porous polymer beads adsorbing the metal impurities. After washing, the metal impurities adsorbed on the porous polymer beads are taken into the aqueous solution, and then the amount of the metal impurities in the aqueous solution is quantified.

As the porous polymer beads used in the present invention, porous polymer beads used as a filler in gas chromatography can be used as they are, and various commercially available ones can be appropriately selected and used.

The gas (sample gas) to be measured is not particularly limited, and is not limited to the gas supplied to the semiconductor manufacturing field, and can be applied to the measurement of metal impurities contained in various gases.

In addition, the porous polymer beads are packed and used in a packed column in the same manner as in a gas chromatograph, and the diameter and length of the packed column are determined by the type of the sample gas (the type of the contained metal component and the type of the base gas) and the like. It can be appropriately determined according to the flow rate and the like.

〔Example〕

Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples.

First, FIGS. 1 and 2 show the configuration of an experimental apparatus used to confirm the effectiveness of the method of the present invention. In the figures, reference numeral 1 denotes a gas container filled with a sample gas; A gas meter for measuring gas flow rate, 3 is a detoxification cylinder for detoxifying a sample gas, and 4 is a packed column for preventing reverse diffusion from a downstream pipe to reduce a measurement error. .

Reference numeral 5 denotes an absorption solution similar to that used in the conventional solution absorption method, for example, dilute hydrochloric acid for bubbling a sample gas, 6 a bypass pipe, 7 a three-way valve for switching the flow path of the sample gas, 8 Is a purge gas introduction pipe, and 9 is a pressure gauge.

Example 1 Polapack Q (trade name, manufactured by WATERS, USA) was used as porous polymer beads. When a commercially available porous polymer bead is precisely analyzed, a metal has already been adhered to itself. First, the adhered metal was washed (conditioned) as shown in FIG. That is, a column packed with 7.5 g of the above porous polymer beads
Tubes 12 and 13 were connected to both ends of 11 (diameter 6 × 8φ, length 70 cm), and an appropriate washing aqueous solution, for example, dilute hydrochloric acid was circulated by a pump 14 to perform washing several times to sufficiently remove adhered metals. .
At this time, a Teflon diaphragm pump was used as the pump 14 so that the metal would not melt out of the pump 14 and adhere to the porous polymer beads. The pipe 15 is a nitrogen gas supply pipe for driving a Teflon diaphragm pump.

Next, as shown in FIG. 1, a column 11 filled with the porous polymer beads washed as described above was inserted between the gas container 1 and the absorbing solution (dilute hydrochloric acid) 5, and BCl ₃ was introduced into nitrogen gas. The sample gas containing 10% was flowed at room temperature at a rate of 0.11 / min for 21 times. Thereafter, the column 11 was removed, and dilute hydrochloric acid was passed through the column 11 in the same manner as in FIG. 3 described above. Emission Analyzer (ICAP-575Mk-11, manufactured by Nippon Jarrell Ash) and F
LAAS analyzer (Perkin-Elmer 1100-B HGA700)
Was measured. At the same time, the metal content of the absorption solution 5 was determined, and the amount of metal impurities passed through the column 11 was measured. Table 1 shows the results.

Comparative Example 1 An experimental apparatus having the configuration shown in FIG. 2, that is, an apparatus having the same configuration except that the column 11 was not inserted in Example 1 was used, and a sample gas was circulated under the same conditions as in Example 1. ,
The content of metals collected in the absorption solution 5 was determined. Table 1 shows the results.

As is clear from Table 1, 0.11 μg of aluminum was collected in Example 1 whereas 0.09 μg was collected in Conventional Example 1 and silicon was 14 μg in Example 1 compared to that of Example 1. In Example 1, the amount was 10 μg.
It can be seen that in magnesium and zinc, metal impurities that could not be detected in Conventional Example 1 could be quantified. Further, the amount of metal in the solution obtained by bubbling the sample gas after passing through the column 11 in Example 1 was below the detection limit, and most of the metal impurities in the sample gas were porous polymer beads in the column 11. You can see that they are being collected.

Example 2 In Example 1, the flow rate of the sample gas was changed to change the column.
The relationship between the amount of BCl ₃ passing through the column 11 and the amount of silicon collected in the porous polymer beads in the column 11 was examined. FIG. 4 shows the result of plotting the relationship between the two by the data least squares method. As is clear from FIG. 4, good linearity was obtained, and a correlation coefficient of 0.99 was obtained.

Example 3 A sample gas containing 50% HCl in nitrogen was used. The same porous polymer beads as in Example 1 were 6 × 8φ in diameter, each having a length of A: 10 cm (filling amount: about 1 g), B: 3
The sample gas was packed in a column of 0 cm (filling amount: about 3.1 g) and C: 60 cm (filling amount: about 6.2 g), and the sample gas was passed through the apparatus having the same configuration as in Example 1 at a flow rate of 0.11 / min at a rate of 3.51 min. I let it. Then, the amount of metal impurities collected in the porous polymer beads and the amount of metal impurities collected in the absorption solution were measured in the same manner as in Example 1. Table 2 shows the results.

From Table 2, it can be seen that when the column length is 10 cm, the porous polymer beads filled in the column break through and the metal is led out of the column and collected in the absorbing solution. Therefore, when measuring metal impurities under the conditions of Example 3, it is understood that it is sufficient to set the column length to about 30 cm. In addition, if the column is too long, the cost increases.

〔The invention's effect〕

As described above, the method for measuring metal impurities in a gas according to the present invention captures the metal impurities in the gas into the porous polymer beads and then quantifies the metal impurities in the solution. Can prevent the negative effects of
Measurement sensitivity can be improved. In addition, a metal having a particle size of 0.05 μm or less can be collected, the collection efficiency can be increased, and the measurement can be performed more accurately than before.

[Brief description of the drawings]

FIG. 1 is a system diagram of the experimental device used in each example, FIG. 2 is a system diagram of the experimental device used in Comparative Example 1, FIG. 3 is a schematic diagram showing an example of a porous polymer bead cleaning device, FIG. FIG. 4 is a diagram showing the relationship between the amount of BCl ₃ passing through the column and the amount of silicon collected in the porous polymer beads. 1 ... gas container, 2 ... gas meter, 5 ... absorption solution, 11 ... column

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Claims (1)

(57) [Claims] 1. A gas containing metal impurities is brought into contact with porous polymer beads to adsorb the metal impurities to the porous polymer beads, and then the porous polymer beads having the metal impurities adsorbed thereon are washed and adsorbed to the porous polymer beads. A method for measuring metal impurities in a gas, comprising: taking in the metal impurities thus obtained into an aqueous solution; and quantifying the amount of the metal impurities in the aqueous solution.