JP2000304734A - Detecting method for contaminant in air - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a detecting method in which a contaminant in a trace amount in air in a clean room or the like is detected simply, with good accuracy and in a short time. SOLUTION: A collecting pipe 12 which is filled with many detecting pieces 10 whose total surface area is known is used. Air 14 as an object is sucked forcibly into the collecting pipe 12. A contaminant in the air as the object is adsorbed to surfaces of the detecting pieces. The contaminant which is adsorbed to the detecting pieces is desorbed from the detecting pieces so as to be analyzed. Thereby, the contaminant is specified and quantitatively determined. Silicon-wafer small pieces whose surface area is known are used as the detecting pieces. As the silicon-wafer small pieces, a silicon wafer is used in such a way that it is crushed in its cleavage plane and that the silicon-wafer small pieces in the same size are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a small amount of contaminants in air, and particularly to a method for detecting an organic gaseous contaminant adsorbed on a silicon wafer surface or a liquid crystal glass substrate in a clean room. The present invention relates to a method for detecting a contaminant, which is preferably applied to a method for detecting contaminants.

[0002]

2. Description of the Related Art As is well known, in a state-of-the-art industrial clean room such as a semiconductor or liquid crystal manufacturing factory, not only fine particles but also acidic gas, alkaline gas, organic gas, etc. Is also attracting attention as a controlled substance. In particular, an organic gaseous pollutant adsorbed on the surface of a silicon wafer has become a problem in the semiconductor manufacturing process, and an evaluation of the organic gaseous pollutant in a clean room is required.

[0003] As a method for evaluating organic gaseous pollutants in a clean room, a silicon wafer as a sample is exposed to air in a clean room to adsorb the contaminants on its surface, and the adsorbed material is desorbed from the sample for analysis. Conventionally, identification and quantification of contaminants have been performed.

[0004]

However, in order to adsorb contaminants on the surface by simply exposing the sample to the air in a clean room as described above, the amount of contaminants to be detected is particularly small. In such cases, sufficient exposure time is required, and there is room for contamination when handling and carrying samples, so that it is not easy to carry out.

In order to analyze the contaminants adsorbed on the sample, as shown in FIG. 4, a silicon wafer as the sample 1 is housed in a heating device 2 and heated by a heater 3 to heat the sample 1. The contaminants on the surface are vaporized and desorbed, and the carrier gas such as nitrogen gas or helium gas is used.
The heat desorption method is a method in which the condensate is identified and quantified by conducting the adsorbent 6 by adsorbing the adsorbent 6 by introducing it to a cooling collector 5 and analyzing the adsorbent 6 by a gas chromatograph or a gas chromatograph-mass spectrometer. Generally adopted. However, such a conventional thermal desorption method requires a special and expensive dedicated heating device 2, and the sample 1 requires the heating device 2.
There is also a problem that the method cannot be applied to a large-sized object that cannot be stored.

[0006] In view of the above circumstances, an object of the present invention is to provide an effective detection method capable of detecting a trace amount of contaminants in air in a clean room or the like more simply, in a short time, and with high accuracy.

[0007]

The invention of claim 1 is a method for detecting contaminants in air, wherein a large number of detection pieces are filled in a collection tube and the total surface area of the detection pieces is reduced. In advance, the contaminants in the target air are adsorbed on the surface of the detection piece by forcibly sucking the target air into the collection tube, and the contaminants adsorbed on the detection piece are desorbed from the detection piece. The analysis identifies and quantifies the pollutants.

According to a second aspect of the present invention, a small piece of a silicon wafer having a known surface area is used as the detection piece.

According to a third aspect of the present invention, a large number of small pieces of silicon wafer formed into the same size by crushing a silicon wafer at a cleavage plane are used.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. This embodiment is applied to a case where a pollutant in the air of a clean room is detected in order to evaluate an organic gaseous pollutant adsorbed on a silicon wafer in a semiconductor manufacturing process. In this embodiment, as shown in FIG.
The detection piece 10 is a silicon wafer small piece as shown in FIG. 2 and the total surface area of a large number of the detection pieces 10 in the collection pipe 11 is determined in advance. That is what you need.

The detection piece 10 is formed according to the procedure shown in FIG.
That is, the surface of the silicon wafer 13 is scratched in parallel with a diamond cutter or the like at regular intervals as shown in FIG. Divide by the cleavage plane to form a strip as shown in (b). Then
The strip-shaped silicon wafer is similarly scratched and similarly pressurized to further divide at the cleavage plane, and (c)
A number of small square silicon wafer pieces having the same dimensions as shown in FIG.

As described above, the detection piece 10 formed by dividing the silicon wafer 13 by the cleavage plane has a sufficiently smooth crushed side surface, and therefore, it is necessary to strictly determine the surface area including the side surface. it can. In this embodiment, a small number of silicon wafer pieces formed with high accuracy are selected and used as the detection pieces 10, and the total surface area of the detection pieces 10 is obtained in advance.

For example, when a silicon wafer 13 having a thickness of 0.6 mm is used, if the size of each detection piece 10 is strictly set to 3 mm × 3 mm, the surface area of each detection piece 10 becomes 25.2 mm ² , Are packed in a total of 4,536 mm ² (45.
36 cm ² ).

As described above, the detection piece 1 having a known total surface area
The collection tube 12 filled with 0 can be handled in the same manner as other conventional collection tubes, for example, a Tenax collection tube, and can accurately detect contaminants in the air.

That is, in order to detect contaminants using the above-mentioned collection tube 12, first, a clean one (blank collection tube) whose purity is guaranteed is stored in a closed container and brought to the work site. After filling the detection piece 10 in the glass tube 11, the blank collection tube is heated to about 300 ° C. while passing an inert gas such as helium gas, so that the inner surface of the glass tube 11 and the surface of the detection piece 10 are heated. It can be obtained by completely desorbing various substances adsorbed on the surface.

At the work site, the collection tube 12
Sampling is performed by forcibly passing the target air 14 through the collection tube 12 at a constant flow rate for a fixed time (for example, 0.5 liter / minute × 20 hours) using a suction pump as shown in FIG. . Thereby, the contaminants in the target air 14 are adsorbed on the surface of each detection piece 10. Note that the side surface of the detection piece 10 (the crushed surface of the silicon wafer 13) is also equivalent to the surface of the silicon wafer 13 with respect to adsorption of contaminants.

After the sampling is completed, the collection tube 12 is completely sealed and stored in a closed container, brought into an analysis room or a laboratory, and analyzed there. That is, by heating to about 300 ° C. while passing an inert gas such as helium gas through the collection tube 12, the contaminants adsorbed on the detection piece 10 by sampling are desorbed from the detection piece 10. It is directly introduced into an analytical instrument (for example, a gas chromatograph or a gas chromatograph-mass spectrometer) together with a carrier gas, and thereby qualitative analysis and quantitative analysis are performed.

As described above, the identification and total amount of the contaminants in the target air 14 adsorbed on the detection piece 10 by sampling can be obtained, and the unit surface area can be calculated from the total surface area of the detection piece 10 as well as the total amount of the contaminants. The amount of contaminants adsorbed per unit area (that is, per unit area of the silicon wafer) (ng / cm ² ) can be easily and accurately obtained.

According to the above-described detection method using the collection tube 12, handling of the sample is remarkably compared with the case where the silicon wafer as the sample is directly exposed to the air and analyzed by the thermal desorption method. Therefore, there is less concern about contamination. In addition, the analyzers and sampling devices used when using various conventional collection tubes can be used as they are, and no special devices or equipment are required, so that contamination is significantly easier and more accurate than the conventional method. Substance detection can be performed. Of course, as the glass tube 11 in the above-mentioned collection tube 12, the glass tube in various conventional collection tubes can be used as it is.

Further, since the contaminant is adsorbed on the detection piece 10 by forcibly sucking the target air 14 into the collection tube 12, four times per unit time as compared with a case where the sample is simply exposed to the air. It has been found that about twice the amount of adsorption can be obtained, and therefore, it is possible to effectively detect trace amounts of contaminants even with a short sampling period.

Since a small piece formed by crushing the silicon wafer 13 on the cleavage surface was used as the detection piece 10,
The side surface of the detection piece 10, which is a crushed surface, naturally becomes smooth, and the surface area thereof can be accurately obtained. Moreover, the detecting pieces 10 having the same shape and the same dimensions (and thus the same surface area)
Is used in a fixed number, so that the total surface area of the detection pieces 10 can be easily obtained from the surface area of each detection piece 10 and the number of the detection pieces 10 to be filled in the collection tube 12. However, the detection pieces 10 do not necessarily have to have the same shape and the same size, and the total surface area may be obtained by calculating the surface area of each detection piece 10 and adding the surface areas. There is no problem even if the shapes and dimensions of the pieces 10 vary. Needless to say, the detection piece 10 is not limited to a square shape, and a strip shape shown in FIG. 3B may be used as it is.

Since the above embodiment aims at detecting an organic gaseous contaminant adsorbed on a silicon wafer in a semiconductor manufacturing process, a small piece of silicon wafer is used as the detection piece 10. It is sufficient that the contaminant to be detected is adsorbed. For example, when detecting a contaminant adsorbed on a glass substrate in a liquid crystal manufacturing process, a small piece of a glass substrate may be used as the detection piece 10.

[0023]

According to the first aspect of the present invention, contaminants in the target air are adsorbed on the surface of the detection piece by forcibly sucking the target air into a collection tube filled with a large number of detection pieces, and the detection pieces are applied to the detection pieces. The identification and quantification of contaminants by desorbing and analyzing adsorbed contaminants from the detector strip makes handling much easier than simply exposing the sample to air, thus reducing contamination. There are few concerns, and the analyzers and sampling devices used when using various conventional collection tubes can be used as they are, and no special devices or equipment are required. It is possible to accurately detect contaminants. In particular, since the total surface area of a large number of detection pieces to be filled in the collection tube is determined in advance, not only the total amount of the contaminants adsorbed on the detection pieces, but also the contaminant per unit surface area of the detection pieces from the total surface area of the detection pieces. The amount of adsorption can also be easily and accurately determined.

According to the second aspect of the present invention, since a small piece of silicon wafer having a known surface area is used as the detection piece, it is possible to accurately specify and quantify a contaminant actually adsorbed on the silicon wafer in the semiconductor manufacturing process.

According to the third aspect of the present invention, since a large number of silicon wafer small pieces formed by crushing a silicon wafer at a cleavage plane to have the same size are used, the surface area of the detection piece can be easily and accurately obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a collection tube used in a detection method according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of the detection piece.

FIG. 3 is a view showing a process of forming a detection piece.

FIG. 4 is a diagram showing an outline of a conventional thermal desorption method.

[Explanation of symbols]

 10 Detection piece (Silicon wafer small piece) 12 Collection tube 14 Target air

Claims (3)

[Claims] 1. A method for detecting contaminants in air, wherein a plurality of detection pieces are filled in a collection tube, and the total surface area of the detection pieces is determined in advance. By forcibly sucking air, the contaminants in the target air are adsorbed on the surface of the detection piece, and the contaminants adsorbed on the detection piece are desorbed from the detection piece and analyzed. A method for detecting pollutants in the air, comprising: 2. The method for detecting contaminants in air according to claim 1, wherein a small piece of silicon wafer having a known surface area is used as said detection piece. 3. The method for detecting contaminants in air according to claim 2, wherein a large number of small pieces of silicon wafer formed into the same size by crushing the silicon wafer on the cleavage surface are used.