JP2002296269A - Device and method for evaluating water quality for sample water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure a concentration of an impurity contained in sample water, and to correctly evaluate an influence onto a substrate, by sampling the impurity contained in the sample water of high purity such as ultrapure water on the substrate using a special container. SOLUTION: A container 4 having a substrate fixing part 12 is used to fix a substrate 10. A substrate take in/out ports, a sample water inlet 20 and a sample water outlet are provided in the container. The container is movable in a sealed condition. The sample water is introduced from the sample water inlet into the container, the sample water is discharged from the sample water outlet to an outside of the container, and the sample water is thereby brought into contact with the substrate fixed to the substrate fixing part. The substrate after the contact with the sample water is dried under a condition fixed to the fixing part. An operation for putting the substrate from the substrate take in/out ports into the container to be fixed to the substrate fixing part, and an operation for taking out the substrate from the substrate take in/out ports to the outside of the container are carried out under a highly clean atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for evaluating the quality of sample water such as ultrapure water.

[0002]

2. Description of the Related Art In the fields of semiconductor manufacturing, chemical manufacturing, and the like, which use ultrapure water for general purposes, ultrapure water of even higher purity has been required in recent years. In the production of ultrapure water, ions, metals, fine particles, viable bacteria, silica, total organic carbon (TOC) and the like contained in the ultrapure water are measured by various analyzers to control water quality.

In the production of ultrapure water, it is necessary to confirm that the desired water quality is maintained. In particular, impurities in ultrapure water used for cleaning and the like in the semiconductor field affect the quality and yield of products, so that accurate analysis is required.

[0004] Conventionally, as a method for evaluating the quality of ultrapure water, there is a method in which ultrapure water is collected from a use point of the ultrapure water into a collection container and measured. For example, ultrapure water specified in JIS-K0553 is used. Metal element test method, JIS-K05
56, for example, a method for testing anions in ultrapure water. In addition, the quality of water may be checked by an on-line analysis method using a monitor instrument. However, there is no monitor instrument for trace metals and viable bacteria.

However, since the method of collecting ultrapure water from a point of use into a collection container and analyzing it is a method of analyzing the ultrapure water itself, the effect of the ultrapure water on a specific substrate is directly evaluated. I couldn't do that. In addition, in this method, only the water quality of the ultrapure water when collected in the collection container is to be evaluated. Therefore, it is difficult to continuously evaluate the water quality of the ultrapure water used for substrate cleaning and the like. there were.

On the other hand, there have been some attempts to analyze the surface of a silicon substrate brought into contact with ultrapure water, as disclosed in Japanese Patent Application Laid-Open Nos. 4-147060 and 5-251542. The evaluation of the quality of ultrapure water using a silicon substrate is performed, for example, as follows. First, a silicon substrate is immersed for a predetermined time in a container storing ultrapure water as a sample. Next, after the silicon substrate is taken out and dried, the natural oxide film formed on the silicon substrate is dissolved using hydrofluoric acid. Further, the obtained solution is evaporated to dryness to form a powder, and the powder is dissolved in a nitric acid solution. The solution is analyzed by a flameless atomic absorption method to quantify the amount of impurities in the sample.

However, the above-described method for evaluating the quality of ultrapure water using a silicon substrate requires a plurality of analysis operations, so that handling errors are likely to occur due to complicated handling, and analysis accuracy is not always sufficient. In particular, handling errors often occur when substrates are taken in and out of the container, making it difficult to perform accurate analysis.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and is intended to remove impurities contained in high-purity sample water such as ultrapure water using a special container. By collecting above, the concentration of impurities contained in the sample water is accurately measured, and the water quality evaluation device for the sample water capable of correctly evaluating the influence on the substrate, and the sample water using the device The purpose is to provide a water quality evaluation method.

[0009]

In order to achieve the above object, the present invention comprises a container having a substrate fixing portion for fixing a substrate therein, the container having a substrate entrance, a sample water entrance and a sample water entrance. A water outlet is provided, and the sample water is introduced into the container from the sample water inlet, and the sample water is discharged from the sample water outlet to the outside of the container, so that the sample water comes into contact with the substrate fixed to the substrate fixing portion. And a container capable of moving the container in a closed state.

The present invention also relates to a water quality evaluation method using the above-described water quality evaluation device of the present invention, wherein a substrate is put into a container from a substrate entrance and fixed to a substrate fixing portion, and then the container is inserted from a sample water inlet. The sample water is introduced into the container, and the sample water is discharged from the sample water outlet to the outside of the container. A method for evaluating water quality of a sample water, characterized in that after drying in a state where the substrate is fixed to a substrate fixing portion, the substrate is taken out of the container from a substrate entrance and an impurity in the sample water attached to the substrate is analyzed.

In this case, in the water quality evaluation apparatus of the present invention, it is preferable that at least the inner surface of the container is formed of a fluororesin, high-purity quartz, or a surface nonconductive metal. Thereby, it is possible to prevent the substrate from being contaminated by the container.

In the water quality evaluation method of the present invention, the operation of putting a substrate into a container from the substrate entrance and fixing it to the substrate fixing portion and the operation of taking the substrate out of the container from the substrate entrance and exit are performed in a highly clean atmosphere. It is preferable to carry out in. Thereby, it is possible to prevent the substrate from being contaminated during the above operation. The atmosphere with high cleanliness is, specifically,
It refers to an environment from which impurities (fine particles and gas components) in the air have been removed, and is preferably an atmosphere cleaner than class 100. Class referred to here, 1ft ³ per 0.3μ
It is a value indicating how many fine particles of m exist, and a smaller value indicates higher cleanliness.

There is no particular limitation on the type of substrate used in the present invention, and usually a substrate for which the influence of the sample water is to be evaluated is used. As such a substrate, for example, a silicon wafer, a compound semiconductor substrate, a glass substrate, a metal plate,
Those having a clean and flat surface such as a glassy carbon plate and a ceramic plate can be used. However, for the measurement of metals,
It is preferable to select a silicon wafer as a substrate effective for using the WSA method (described later), which is a highly clean and highly sensitive analysis method. However, if an analysis method other than the WSA method such as the total reflection X-ray fluorescence method is used, the substrate is not limited to a silicon wafer.

In the present invention, it is particularly preferable to analyze one or more selected from metals, organic substances, ions and fine particles as impurities in the sample water attached to the substrate.

In this case, as a method of analyzing metals, for example, a method described in A. Shimazaki: Proc. ECS, Defects in Silicon
II, p. 47-1991 "(hereinafter, referred to as WSA method) can be suitably used. In the WSA method, the entire surface of the wafer is scanned with droplets of a recovery liquid, and the impurities recovered in the droplets are analyzed by a flameless atomic absorption method (AAS) or an inductively coupled mass spectrometer (I
CP-MS), and the total amount of impurities can be quantified with high sensitivity. As an analysis method other than the WSA method, a method in which impurities on the substrate are not dissolved and detected by a surface analyzer such as a total reflection X-ray fluorescence method may be used.

In the analysis of organic substances, the organic substances adsorbed on the substrate surface include a chemically adsorbed component, a low molecular weight component and a high molecular weight component adsorbed physically, and it is necessary to use an analytical method suitable for the purpose of measurement. It is. For example, acetone, isopropyl alcohol, etc. are described in the document "Thermal desorption-gas chromatography" described in the document "Ayako Shimazaki, Makiko Tamaki, Yumi Sasaki, Tsuyoshi Matsumura: The 39th Lecture Meeting on Applied Physics, 30a-ZF-6-1992". A chromatography mass spectrometer can be used.
Urea and the like can be measured using liquid chromatography after extraction with an extract.

The analysis of ions can be carried out by extracting the substrate in the extract, and then measuring the extract by ion chromatography. For example, the document "H. Shim
izuand S.ishiwari: Mater.Trans., Jum., 36,1271-1995 ''
The ions can be analyzed using the method described in, for example.

The analysis of the fine particles can be performed using a mirror surface wafer surface inspection apparatus or the like.

[0019]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an embodiment of a water quality evaluation device according to the present invention, in which (A) is a front view,
(B) is a side view.

In the water quality evaluation apparatus 2 of this embodiment, reference numeral 4 denotes a sealable container. The container 4 includes a container body 6 and a lid 8 that closes an upper end opening of the container body 6, and a substrate fixing portion 12 that can fix a plurality of substrates 10 is provided inside the container body 6. ing. The substrate fixing section 12 holds the substrate 10 (in this example, a silicon wafer) between four round rod-shaped substrate fixing rods 14. The upper two of the four substrate fixing rods 14 are connected to the lid 8.

A plurality of ejection holes 16 are provided at the bottom of the container body 6.
Is provided, and an end of the sample water ejection pipe 18 is configured as a sample water inlet 20.
In addition, a drain port 22 is formed at the bottom of the container body 6. In the water quality evaluation device 2 of the present example, as will be described later, the upper end opening of the container body 6 is configured as a substrate inlet / outlet and a sample water outlet.

The water quality evaluation of the ultrapure water using the apparatus of this embodiment is as follows.
For example, the process is performed as follows (see FIG. 2, FIG. 2 is a front view showing a state in which the sample water is brought into contact with the substrate using the apparatus of FIG. 1).

(1) The lid 8 is removed from the container body 6, and one or a plurality of substrates 10 are inserted into the container body 6 from the upper end opening (substrate entrance) of the container body 6 (a plurality of substrates in this example). These substrates 10 are fixed to the substrate fixing unit 12.
In this apparatus, the substrate 10 is fixed to the substrate fixing portion 12 only by mounting the substrate 10 on the lower two of the four substrate fixing rods 14. afterwards,
A lid 8 is attached to the container body 6 to seal the container 4. The operation of putting the substrate 10 into the container 4 from the substrate entrance and fixing it to the substrate fixing part 12 is performed in an atmosphere with high cleanliness.

(2) Next, the container 4 containing the substrate 10 is transported to a point of use of ultrapure water, and a sample water sampling pipe connected to the point of use is connected to the sample water inlet 20 of the container 4. The lid 8 is removed from the main body 6. Thereafter, the sample water flowing through the sample water sampling pipe is continuously introduced into the container main body 6 from the sample water inlet 20 for a predetermined time, and the sample water overflows from the upper end opening (substrate entrance) of the container main body 6, The sample water is brought into contact with the substrate 10 fixed to the substrate fixing unit 12. In this case, the container 4 is provided with a drain tank 24 for receiving the overflowed sample water.
The flow rate (integrated amount) of the sample water that has been installed in the inside and is measured by an integrating flow meter 28 installed in the drain pipe 26. In FIG. 2, the flow of the sample water is indicated by arrows. It is preferable that the sampling operation of the ultrapure water is also performed in an atmosphere with high cleanliness. Therefore, when the cleanliness of the ultrapure water sampling place is low, the ultrapure water sampling operation is performed using the ULPA filter (Ultra Low Penetrat).
It is preferably performed in a booth using an ion air filter or a chemical filter.

(3) The substrate 10 having been brought into contact with the sample water is dried while being fixed to the substrate fixing portion 12. Specifically, after the plug of the drain port 22 is removed and the sample water in the container body 6 is drained, the container 8 is naturally attached with the lid 8 attached thereto or with the lid 8 removed from the container body 6. The substrate 10 is dried by a drying method or a method of contacting with clean air. This drying operation of the substrate is also preferably performed in a highly clean atmosphere. Therefore, when the cleanliness of the drying place of the substrate is low, it is preferable to perform the drying operation of the substrate in a booth provided with an ULPA filter or a chemical filter.

(4) Next, the container 4 containing the dried substrate 10 is transported in a highly clean atmosphere with the lid 8 attached to the container body 6, and the container body 6 is placed in this atmosphere.
The lid 8 is removed from the container 10, and the substrate 10 is taken out of the container body 6 from the upper end opening (substrate entrance) of the container body 6.

(5) Then, impurities in the sample water adhering to the substrate 10 are analyzed. As the impurities, it is appropriate to analyze one or more kinds selected from metals, organic substances, ions and fine particles. As these analysis methods, the methods described above can be used. This analysis operation is also preferably performed in an atmosphere with high cleanliness.

[0028]

(Example 1) The quality of ultrapure water was evaluated in substantially the same manner as in (1) to (5) described above. First, the lid of the water quality evaluation apparatus shown in FIG. 1 was opened in a clean bench (class 10), five silicon wafers with a natural oxide film were placed on the substrate fixing part, and the container was closed with the lid. This water quality evaluation device was transported to a clean room (class 1000), and the pipe of the sample water was connected to the sample water inlet of the water quality evaluation device. Further, the lid of the water quality evaluation device was opened, and the sample water was passed through the container for 24 hours. As the sample water, a solution in which iron was added to ultrapure water having a metal impurity concentration of 1 ng / L or less so that the iron concentration was 5 ng / L was used. After passing the water, the water was drained from the bottom of the apparatus, the lid was closed, and the wafer was air-dried. Impurities adhering to the substrate were collected using a WSA method, and iron was measured using an inductively coupled plasma mass spectrometry (ICP-MS method). Table 1 shows the average value and the coefficient of variation of the recovery concentrations of the five wafers. The coefficient of variation (or relative standard deviation) is a value obtained by dividing the standard deviation of n measurement results by the average value of n and multiplying by 100. The unit is percent (%). The smaller the coefficient of variation, the smaller the dispersion of the measured values.

(Comparative Example 1) A bath in which a wafer can be immersed and a folder for fixing the wafer were prepared and placed in a clean room (class 1000). Place five silicon wafers with natural oxide film in the folder,
Water passed for hours. After passing water, remove the folder from the immersion tank,
Air dried. The sample water and the impurity analysis method were the same as in Example 1.

[0030]

[Table 1]

(Example 2) The quality of ultrapure water was evaluated in substantially the same procedure as in the above (1) to (5). First, the lid of the water quality evaluation apparatus shown in FIG. 1 was opened in a clean bench (class 10), five silicon wafers with a natural oxide film were placed on the substrate fixing part, and the container was closed with the lid. This water quality evaluation device was transported to a clean room (class 1000), and the pipe of the sample water was connected to the sample water inlet of the water quality evaluation device. Further, the lid of the water quality evaluation device was opened, and the sample water was passed through the container for 24 hours. As the sample water, a solution in which isopropyl alcohol was added to ultrapure water having a TOC concentration of 1 μg / L or less so that the isopropyl alcohol concentration became 10 μg / L was used. After passing the water, the water was drained from the bottom of the apparatus, the lid was closed, and the wafer was air-dried. The substrate was placed in a heat desorption container and heated, and isopropyl alcohol was measured using a heat desorption-gas chromatograph mass spectrometer. Table 2 shows the average value and the coefficient of variation of the recovery concentrations of the five wafers.

(Comparative Example 2) A bath in which a wafer can be immersed and a folder for fixing the wafer were prepared and placed in a clean room (class 1000). Place five silicon wafers with natural oxide film in the folder,
Water passed for hours. After passing water, remove the folder from the immersion tank,
Air dried. The sample water and impurity analysis method were the same as in Example 2.

[0033]

[Table 2]

From Tables 1 and 2, according to the first embodiment, the operation of putting the substrate into the container from the substrate entrance and fixing it to the substrate fixing portion and the operation of taking the substrate out of the container from the substrate entrance and exit are performed in a highly clean atmosphere. (2) that the impurities contained in the sample water can be accurately recovered, and that the dispersion of the measured values is small;
Therefore, it was found that the impurities contained in the sample water can be accurately quantified, and the influence on the substrate can be correctly evaluated.
In response, the installation of silicon wafers in folders,
In Comparative Examples 1 and 2, in which the silicon wafer was taken out of the folder at the sampling location, the measured values varied greatly, and it was difficult to accurately quantify impurities contained in the sample water.

[0035]

As described above, according to the present invention, impurities contained in high-purity sample water such as ultrapure water are collected on a substrate using a special container, thereby containing the impurities in the sample water. It is possible to accurately measure the concentration of the impurity contained and accurately evaluate the influence on the substrate. Therefore, according to the present invention, of the impurities in ultrapure water used for cleaning a semiconductor substrate and the like, the components adsorbed on the substrate, that is, the components that affect the substrate can be specified, and those components can be accurately determined. Can be measured.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a water quality evaluation device for sample water according to the present invention, wherein (A) is a front view and (B) is a side view.

FIG. 2 is a front view showing a state where sample water is brought into contact with a substrate using the apparatus of FIG.

[Explanation of symbols]

 2 Water quality evaluation device 4 Container 6 Container body 8 Lid 10 Substrate 12 Substrate fixing part 14 Substrate fixing rod 18 Sample water ejection pipe 20 Sample water inlet

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G01N 1/10 G01N 1/10 N H01L 21/304 648 H01L 21/304 648G F-term (Reference) 2G052 AA06 AB26 AC17 AC28 AD06 AD26 AD52 BA02 BA21 CA02 CA48 DA05 DA22 EB01 ED01 ED03 FD18 JA09

Claims (6)

[Claims] 1. A container provided with a substrate fixing portion for fixing a substrate therein, the container having a substrate entrance, a sample water inlet, and a sample water outlet provided therein. By introducing the sample water and discharging the sample water from the sample water outlet to the outside of the container, the sample water can be brought into contact with the substrate fixed to the substrate fixing portion, and the container can be moved in a closed state. An apparatus for evaluating water quality of a sample water. 2. The apparatus for evaluating water quality of a sample water according to claim 1, wherein at least the inner surface of the container is formed of a fluororesin, high-purity quartz, or a surface nonconductive metal. 3. A water quality evaluation method using the water quality evaluation device according to claim 1 or 2, wherein a substrate is put into a container from a substrate entrance and fixed to a substrate fixing portion, and then a sample water inlet is inserted into the container. The sample water is introduced into the substrate, and the sample water is discharged from the sample water outlet to the outside of the container, so that the sample water is brought into contact with the substrate fixed to the substrate fixing portion. A method for evaluating water quality of a sample water, comprising drying the substrate in a state of being fixed to a fixing portion, taking out the substrate from the substrate inlet / outlet to the outside of the container, and analyzing impurities in the sample water attached to the substrate. 4. The method according to claim 1, wherein the operation of inserting the substrate into the container through the substrate entrance and fixing the substrate to the substrate fixing portion and the operation of taking the substrate out of the container through the substrate entrance and exit are performed in a highly clean atmosphere. Item 4. The water quality evaluation method of the sample water according to Item 3. 5. The method according to claim 3, wherein a silicon wafer is used as the substrate. 6. The method according to claim 3, wherein one or more selected from metals, organic substances, ions and fine particles are analyzed as impurities in the sample water attached to the substrate. The water quality evaluation method of the sample water described in the paragraph.