JP3584430B2 - Contaminant detection method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is intended for various articles requiring high cleanliness (for example, silicon wafers and liquid crystal glass substrates, or interior finishing materials for clean rooms, etc.), and contaminants adsorbed or adhered to the surface of the object. The present invention relates to a method for detecting the presence / absence (for example, an organic substance, a metal, an ionic substance, etc.) and a concentration thereof.
[0002]
[Prior art]
As is well known, in the manufacturing process of semiconductors and liquid crystals, silicon wafers and liquid crystal glass substrates must be maintained at a high degree of cleanliness, and inspection and evaluation of the presence and degree of contamination on their surfaces in the middle of the manufacturing process. It is important to.
[0003]
As a method for detecting contaminants adsorbed or attached to the surface of a silicon wafer, particularly, an organic substance, a solvent extraction method and a heat desorption method are known.
[0004]
In the solvent extraction method, as shown in FIG. 3, a sample 1 (a silicon wafer to be inspected) is immersed in an organic solvent 2 to extract contaminants adsorbed on the surface of the sample 1 into the solvent 2. Is concentrated and analyzed by a gas chromatograph or a gas chromatograph-mass spectrometer to identify and quantify the type and concentration of the extracted contaminant.
[0005]
In the thermal desorption method, as shown in FIG. 4, a sample 1 is heated to about 300 ° C. by a heater 4 in a heating vessel 3 so that contaminants adsorbed on the surface are vaporized and separated from the sample 1. The contaminated matter is guided to a cooling collector 6 by a carrier gas 5 such as nitrogen gas or helium gas to be adsorbed by an adsorbent, and the adsorbent is analyzed by a gas chromatograph or a gas chromatograph-mass spectrometer.
[0006]
When a metal or an ionic substance is to be detected, a solvent extraction method similar to the above (however, an ion chromatograph, an atomic absorption spectrometer, an ICP-mass spectrometer, or the like is used for analysis) or a surface analysis It is known to perform analysis using an apparatus (X-ray microanalyzer, analytical electron microscope, etc.).
[0007]
[Problems to be solved by the invention]
However, in the solvent extraction method shown in FIG. 3, a large amount of solvent is required to immerse the entire silicon wafer, a large amount of solvent needs to be concentrated, and there is room for contamination at the stage of concentration of the solvent. There is a problem that contaminants insoluble in the solvent cannot be detected.
[0008]
In addition, the heat desorption method shown in FIG. 4 requires a special and expensive dedicated heating vessel 3. When the sample 1 is heated, the contaminants are decomposed or deteriorated, and detection is performed as it is. This cannot be applied to a large sample that cannot be accommodated in the heating vessel 3 or cannot be applied to a liquid crystal glass substrate.
[0009]
Further, the surface analyzer used for detecting a metal or an ionic substance is extremely large and expensive, and the analysis by these is a point analysis for one point on the sample surface. When performing detection over a range, a large amount of analysis data is required.
[0010]
In addition, the above-mentioned conventional methods are based on the premise that all procedures are performed in an analysis room or a laboratory. Therefore, conventionally, the sample 1 is generally stored in a container such as a wafer cassette which can hold a clean state. Although it is brought from the production line to the analysis room and laboratory, it is considered that carrying silicon wafers, although using a wafer cassette etc., has room for contamination at that stage, and it is preferable that Absent.
[0011]
By the way, in recent years, a decrease in cleanliness caused by adsorption of various contaminants (gaseous contaminants, metals, ionic substances, etc.) on the surface of the interior finishing material of a clean room has become a problem. However, at this time, there is no effective and appropriate means to analyze and evaluate contaminants in the interior finishing materials of clean rooms.Therefore, it is necessary to confirm the cleanliness of the interior finishing materials in clean rooms. There was a problem that it could not be done. Conventionally, if the analysis and evaluation of contaminants on the interior finishing material of a clean room were to be performed dare, a sample was cut from the target interior finishing material, and the sample was subjected to the solvent extraction method or the heat desorption method described above. Alternatively, it is necessary to perform analysis using a surface analyzer, but in such a case, it is inevitable that the surroundings will be severely contaminated during sample cutting work, and naturally it is necessary to stop operating the clean room for a long time. And it takes a lot of trouble to recover, which is not realistic at all.
[0012]
In view of the above circumstances, the present invention is an effective method that can easily detect various contaminants on the surface of silicon wafers and liquid crystal glass substrates as well as interior finishing materials of clean rooms and the like without concern about contamination. The purpose is to provide.
[0013]
[Means for Solving the Problems]
The present invention is a method for detecting the presence and concentration of contaminants adsorbed or adhered to the surface of an article requiring high cleanliness, and a method for detecting a clean wiping material and a wiping liquid. After wiping the contaminants on the surface of the object by performing a wiping operation on the surface of the object, the wiping material and the wiping liquid used for wiping are collected, and the contaminants wiped off by the wiping material and the wiping liquid. It is characterized by analyzing the components of the product.
If the contaminant to be detected is an organic substance, use quartz wool as the wiping material and an organic solvent such as hexane as the wiping liquid, and heat the collected wiping material and wiping liquid to remove the contaminant. To analyze. In this case, the collected wiping material and the wiping liquid are housed in a glass collecting tube and sealed, and the glass collecting tube is directly attached to the analyzer and heated to contaminate the wiping material and the wiping liquid. It is good to let things come off.
If the contaminants to be detected are metals or ionic substances, use a clean room wiper as the wiping material, use ultrapure water as the wiping solution and solvent, and immerse the collected wiping material and wiping solution in the solvent. To elute the contaminants into the solvent and analyze the eluate. In this case, the collected wiping material and the wiping liquid are stored in a sealed container made of a quartz container or a plastic container and sealed, and the sealed container is taken into an analysis room where contaminants are removed from the wiping material and the wiping liquid. What is necessary is just to elute in a solvent.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a conceptual diagram showing an embodiment in which the method of the present invention is applied to a silicon wafer. The method of the present embodiment is suitable when the contaminant to be detected is an organic substance. Quartz wool is used as the wiping material 10 and an organic solvent such as hexane is used as the wiping liquid 11. A predetermined amount of the wiping liquid 11 is dropped on the surface of the sample 1 of the silicon wafer, which is an object, by using the dropper 12 or the wiping liquid 10 is impregnated in the wiping material 10 in advance, and the wiping material 10 is sampled with the tweezers 13 using the tweezers 13. By performing the operation of wiping the entire surface of the sample 1 uniformly, the contaminants on the surface of the sample 1 are extracted by the wiping liquid 11 and mechanically wiped by the wiping material 10.
[0015]
After repeating the above wiping operation on the entire surface of the sample 1 several times as necessary, all the wiping materials 10 and the wiping liquid 11 used in the wiping operation are collected in place, and the glass is collected. It is housed in a collecting pipe (not shown) and sealed in a completely airtight state. Then, the glass collection tube is attached to a gas chromatograph or a gas chromatograph-mass spectrometer, and the wiping material 10 and the wiping liquid 11 in the glass collection tube are heated to release the wiped contaminants. Analyze to identify and quantify contaminants. Note that all instruments used for the wiping operation, that is, quartz wool as the wiping material 10, organic solvent as the wiping liquid 11, dropper 12, tweezers 13, and the glass collection tube are all guaranteed cleanliness. It is natural to use what has been done.
[0016]
According to the above method, if the contaminant adsorbed on the surface of the sample 1 is an organic substance that is soluble in the wiping liquid 11, it can be easily extracted and reliably wiped off. Even contaminants such as ions can be mechanically wiped by the wiping material 10 and the wiping liquid 11, so that not only organic substances but also all contaminants can be detected, identified, and quantified. .
[0017]
Since the above wiping operation does not require any special device, it can be easily performed in the middle of the production line, and therefore, it is not necessary to take out the sample 1 from the production line for inspection as in the related art. In addition, the wiping material 10 and the wiping liquid 11 used for wiping can be immediately collected in the glass collecting tube and completely sealed, or completely sealed in the glass collecting tube. For example, there is little room for contamination from carrying it. Therefore, according to the above-mentioned method, there is much less concern that contamination will occur at the time of inspection than in the past.
[0018]
Further, since the above wiping operation can be applied without any problem even if the sample 1 is large, a large sample to which the conventional thermal desorption method cannot be applied, for example, a next-generation 300 mm wafer or a large liquid crystal glass It can be applied to a substrate without any problem. Furthermore, since only a small amount of solvent is used as the wiping liquid 11, it is not necessary to use a large amount of solvent or to concentrate it as in the conventional solvent extraction method in which the entire sample is immersed in the solvent. Of course, no special and complicated device is required as in the case of the conventional thermal desorption method, so that the detection cost can be sufficiently reduced as compared with the conventional method. In addition, the present invention can be similarly applied not only to a silicon wafer but also to a liquid crystal glass substrate during a liquid crystal manufacturing process.
[0019]
FIG. 2 shows a comparison of the wafer surface adsorption concentrations detected by the method of the present invention according to the above embodiment and the conventional thermal desorption method. As is apparent from FIG. 2, in the method of the present invention, substantially the same detection result is obtained although the detection value is slightly lower in general as compared with the conventional heat desorption method. It has proven to be fully effective.
[0020]
Hexane is preferably used as the wiping liquid 11 in terms of extractability with respect to various organic substances and ease of use. However, other organic solvents such as carbon tetrachloride, carbon disulfide, acetone, and toluene can also be used. Yes , an optimum wiping solution may be appropriately selected and employed .
[0021]
The embodiment described above is suitable when the contaminant to be detected is an organic substance.However, when the contaminant to be detected is a metal or an ionic substance, the following is preferable. .
[0022]
That is, it is not preferable to use quartz wool as the wiping member 10 because a metal component such as sodium is eluted. Therefore, a clean room wiper is used instead. The clean room wiper is a product made of, for example, polyester long fiber or polypropylene long fiber, which is guaranteed to have cleanliness on the assumption that it is used in a clean room, and has been frequently used in a clean room. As the wiping liquid 11, ultrapure water is used instead of the organic solvent. Then, a wiping operation is performed using the wiping material 10 and the wiping liquid 11, and the wiping material 10 and the wiping liquid 11 are all collected and sealed in a sealed container. As the sealed container used here, it is preferable to use a quartz container or a plastic container instead of the above-mentioned glass collecting tube. (In the glass collecting tube, there is a concern that metal components such as sodium may be eluted similarly to quartz wool. Absent). Then, the sealed container is brought into an analysis room or the like, where the collected wiping material 10 and wiping liquid 11 are immersed in a solvent to elute the wiped contaminants into the solvent, and the eluate is subjected to ion chromatography or ion chromatography. Analysis is performed by an atomic absorption spectrometer, an ICP-mass spectrometer, or the like. As a solvent for eluting contaminants, the same ultrapure water as the wiping liquid 11 may be used. In addition, besides ultrapure water, nitric acid, sodium hydroxide, acetic acid, sulfuric acid and the like can be used as the wiping liquid 11 and the solvent, and an optimal one may be selected according to the type of contaminant assumed. .
[0023]
As described above, it is possible to easily detect metals and ionic substances by almost the same method as that for organic substances, and in particular, it is not necessary to use a large and expensive surface analyzer as in the past, and for large samples. Is also very effective because it can be applied without any problem.
[0024]
In the above embodiment, the wiping operation using the wiping material 10 is performed manually using the tweezers 13. However, the wiping operation can be performed mechanically if there is no fear of causing contamination. For example, the entire surface of the sample 1 is wiped by placing the sample 1 on a turntable and rotating it like a record while pressing the wiping material 10 against the surface of the sample 1 with a constant pressure and sliding in the radial direction of the sample 1. It is conceivable to do so. Alternatively, it is conceivable to fix the sample 1 and move the wiping member 10 so as to scan the entire surface, or conversely, fix the wiping member 10 and move the sample 1 similarly. Of course, the size and shape of the wiping material 10 and the required amount of the wiping liquid 11 may be arbitrarily set so that the wiping operation can be performed efficiently and reliably.
[0025]
Furthermore, the present invention is applicable not only to the above-described silicon wafers and liquid crystal glass substrates, but also to various articles requiring high cleanliness. The present invention can be suitably adopted to confirm and evaluate the cleanliness of a finishing material (for example, an acrylic plate used as a partition panel, a partition material, a ceiling material, a floor material, and the like). In other words, when the clean room is completed, or if the cleanliness of the operating clean room is impaired for some reason, the specific part of the finishing material in the clean room is targeted, and the surface Perform a similar wiping operation using a wiping material such as quartz wool or a clean room wiper and a wiping liquid such as an organic solvent or ultrapure water, and apply the wiping material and the wiping liquid used for wiping in place. And sealed in a sealed container such as a glass collection tube, a quartz container, or a plastic container, and then carry it to an analysis room or a laboratory for analysis. Therefore, according to the present invention, it is possible to confirm and evaluate the cleanliness of interior finish materials in a clean room, which was not possible in the past, and it is easy to stop the production line while keeping the clean room in operation. It is possible to implement. Of course, it is needless to say that the present invention can be similarly applied not only to the interior finishing material but also to the surfaces of various manufacturing apparatuses installed in a clean room and their accessories.
[0026]
【The invention's effect】
As described above, the detection method of the present invention performs a wiping operation on an object surface using an organic solvent, ultrapure water, or the like as a wiping liquid, quartz wool, a clean room wiper, or the like as a wiping material. Since the wiping solution and the wiping material are collected and the components of the contaminated substances are analyzed, the contaminants insoluble in the solvent that cannot be detected by the conventional solvent extraction method are mechanically wiped. It is also possible to detect contaminants which are supposed to be decomposed or deteriorated by the conventional thermal desorption method, and it is possible to detect various contaminants such as organic substances, metals and ionic substances. There is an effect that the detection can be easily performed.
[0027]
In addition, the present invention does not require any special and expensive equipment for the wiping operation, so that a simple wiping operation can be performed on a silicon wafer or a liquid crystal glass substrate in the middle of a semiconductor or liquid crystal production line. Therefore, there is no need to carry the sample itself during the test, so there is no risk of contamination due to carrying the sample, and the detection cost can be reduced without being limited by the size of the sample. Play.
If the contaminant is an organic substance, if the wiping material and the wiping solution used for wiping are immediately sealed in a glass collection tube on the spot, the contaminant can be carried without concern about contamination. Instead, by attaching the glass collecting tube to the analyzer, the wiping material and the wiping liquid can be heated as it is to remove contaminants and perform analysis. If the contaminants are metals or ionic substances, if the wiping material and the wiping liquid used for wiping are immediately sealed in a sealed container made of quartz or plastic on the spot, there is a risk of contamination. And the contaminants can be eluted into the solvent from the wiping material and the wiping liquid and analyzed there.
[0028]
In addition, the present invention can be widely applied not only to silicon wafers and liquid crystal glass substrates, but also to various articles. Analysis and evaluation of the cleanliness of the interior material itself can be easily performed.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing an embodiment when a detection method of the present invention is applied to a silicon wafer.
FIG. 2 is a graph showing a comparison between detection values obtained by the method of the present invention and a conventional heat desorption method.
FIG. 3 is a conceptual diagram showing a conventional solvent extraction method.
FIG. 4 is a conceptual diagram showing a conventional thermal desorption method.
[Explanation of symbols]
1 sample (object)
10 Wiping material 11 Wiping liquid

Claims (4)

In order to detect the presence and concentration of organic substances, which are contaminants adsorbed or adhered to the surface of articles that require high cleanliness , use a clean wiping material and wiping liquid. After performing a wiping operation on the surface to wipe off contaminants on the surface, the wiping material and the wiping liquid used for wiping are collected, and the components of the contaminant wiped off by the wiping material and the wiping liquid are analyzed. A method for detecting contaminants,
Contamination characterized by using quartz wool as the wiping material, using an organic solvent such as hexane as the wiping liquid, heating the collected wiping material and the wiping liquid to separate contaminants, and performing analysis. Object detection method. 2. The method for detecting contaminants according to claim 1, wherein the collected wiping material and the wiping liquid are housed in a glass collecting tube and hermetically sealed, and the glass collecting tube is mounted on an analyzer for analysis. Use a clean wiping material and liquid to detect the presence and concentration of contaminant metals and ionic substances adsorbed or adhered to the surface of articles requiring high cleanliness. After wiping the surface of the object to wipe off contaminants on the surface, the wiping material and the wiping liquid used for wiping are collected, and the components of the contaminant wiped off by the wiping material and the wiping liquid. A method for detecting contaminants, comprising:
Using a clean room wiper as the wiping material, using ultrapure water as the wiping solution and the solvent, immersing the collected wiping material and the wiping solution in the solvent to elute contaminants into the solvent, and eluting the A method for detecting contaminants, comprising analyzing a liquid . 4. The contaminant detection method according to claim 3, wherein the collected wiping material and the wiping liquid are stored in a sealed container made of a quartz container or a plastic container and sealed, and the sealed container is carried into an analysis chamber for analysis. Method.

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