JP2002340751A - Method for evaluating quality of sample water, and apparatus for sampling impurity in sample water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for correctly evaluating the effect on a substrate of sample water by sampling impurities contained in highly pure sample water such as ultra pure water by continuously supplying the sample water to the substrate, and hence accurately measuring the concentration of impurities contained in the sample water. SOLUTION: An impurity-sampling apparatus 2 equipped with a sampling container 8 having a substrate-fixing section 6 inside, a sample water supply means for supplying sample water 12 onto the upper surface of the substrate 4 being fixed to the substrate-fixing section, and sample water-drying means 18 and 20 for drying the sample water on the upper surface of the substrate. Then, the sample water is continuously supplied to the substrate by the sample water-supplying means, at the same time the sample water is continuously dried by the sample water-drying means, thus sampling impurities contained in the sample water as a residue on the substrate, and then analyzing the impurities on the substrate. The sample water is sampled directly and continuously from a sampling point 40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating the quality of sample water such as ultrapure water, and an apparatus for collecting impurities in the sample water used for carrying out the method.

[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.

Conventionally, as a method for evaluating the quality of ultrapure water, there is a method in which ultrapure water is collected from a sampling point of the ultrapure water into a collection container and measured. For example, JIS-K0553
Test method for metal elements in ultrapure water specified in JIS
There is an anion test method in ultrapure water specified in K0556. 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 sampling point 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. Also,
In this method, since only the quality of ultrapure water when collected in a collection container is to be evaluated, it was difficult to continuously evaluate the quality of ultrapure water used for substrate cleaning and the like. .

On the other hand, as disclosed in Japanese Patent Application Laid-Open Nos. Hei 4-136538 and Hei 9-15174, sample water (including chemicals) is dropped on the surface of the substrate, and the sample water is evaporated to form the sample water. There is a method in which the impurities contained are precipitated as residues on the substrate surface and analyzed. However, in this method, since the sample water is dropped on the substrate surface in a batch system, since the amount of impurities in the ultrapure water is extremely small, the amount of the sample water to be evaluated is increased to improve the analysis accuracy. Then, a plurality of steps are required, and as a result, there is a problem that contamination occurs and analysis accuracy is reduced.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and is intended to continuously remove impurities contained in high-purity sample water such as ultrapure water onto a substrate. By collecting the sample on the substrate by contacting it with the sample water, the concentration of impurities contained in the sample water can be accurately measured, and the effect of the sample water on the substrate can be correctly evaluated. It is an object of the present invention to provide a water quality evaluation method of a sample water capable of evaluating the water quality of the sample water with high accuracy, and an apparatus for collecting impurities in the sample water used in the method.

[0008]

According to the present invention, in order to achieve the above object, a sample water is continuously supplied to a substrate, and the sample water is continuously dried to continuously supply the sample water to the substrate. A method for evaluating the water quality of a sample water, comprising: collecting impurities contained in the sample water as residues on a substrate and analyzing the impurities on the substrate.

Further, the present invention is an impurity collecting apparatus which can be used for carrying out the above-mentioned water quality evaluation method, wherein the sampling container having a substrate fixing part in which a substrate is fixed substantially horizontally is provided. A sample water supply unit for supplying sample water to the upper surface of the fixed substrate; and a sample water drying unit for drying sample water existing on the upper surface of the substrate fixed to the substrate fixing unit. By continuously supplying the sample water to the upper surface of the substrate and continuously drying the sample water by the sample water drying means,
Provided is an apparatus for collecting impurities in sample water, wherein impurities contained in the sample water continuously supplied to the substrate are collected as residues on the substrate.

Hereinafter, the present invention will be described in more detail. In the water quality evaluation method of the present invention, first, as described above, by simultaneously supplying the sample water to the substrate and drying while contacting at least so that the sample water does not overflow from the substrate, Impurities contained in the sample water continuously supplied to the substrate are collected as residues on the substrate. In this case, there is no particular limitation on the type of substrate used,
Usually, a substrate for which the influence of the sample water is to be evaluated is used. Examples of such a substrate include those having a clean and flat surface such as a silicon wafer, a compound semiconductor substrate, a glass substrate, a metal plate, a glassy carbon plate, and a ceramic plate. However, in the measurement of metals, it is preferable to select a silicon wafer as a substrate effective for using a 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 water quality evaluation method of the present invention, it is appropriate that the sample water is directly and continuously collected from the sampling point and the sample water is continuously supplied to the substrate. As a result, it is possible to continuously evaluate the water quality of the sample water such as ultrapure water used for cleaning the substrate without polluting the water quality and without time lag.

In the water quality evaluation method of the present invention, it is preferable to dry the sample water by heating or vacuum drying. This makes it possible to reliably and continuously dry the sample water supplied to the substrate so as not to overflow from the substrate.

Next, in the water quality evaluation method of the present invention, impurities in the sample water collected on the substrate are analyzed. Although there is no limitation on the analysis target, it is particularly preferable to analyze one or more selected from metals, organic substances, ions and fine particles as impurities in the sample water.

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 which are physically adsorbed, 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.

In the water quality evaluation method of the present invention, it is preferable that both the operation of drying while supplying the sample water to the substrate and the operation of analyzing impurities on the substrate are performed in an atmosphere with high cleanliness. Thereby, it is possible to prevent the substrate from being contaminated during the above operation. The atmosphere having a high degree of cleanliness specifically 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. The class here is
This is a value indicating how many 0.3 μm fine particles are present per 1 ft ^{3. The} smaller the value, the higher the cleanliness.

[0019]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic view showing an embodiment of the apparatus for collecting impurities in sample water according to the present invention. The impurity collecting apparatus 2 of the present embodiment includes a sampling container 8 having one or two or more substrate fixing portions 6 (only one is illustrated in the figure) on which the substrate 4 is fixed substantially horizontally, and a substrate fixing portion. A sample water supply unit for supplying sample water to the center of the upper surface of the substrate 4 fixed to the substrate 6; and a sample water drying unit for drying sample water existing on the upper surface of the substrate 4 fixed to the substrate fixing unit 6. I do. The sampling container 8 has an openable door 9 and an ULPA filter (Ultra Low Penetration).
Air Filter) or a chemical filter 11.
In FIG. 1, reference numeral 30 denotes an ultrapure water production apparatus, and reference numeral 40 denotes a sampling point of ultrapure water.

The sample water supply means includes a sample water sampling pipe 10 for directly and continuously sampling sample water from a sampling point 40 of ultrapure water.
The sample water 12 collected through the substrate 4 is continuously dropped and brought into contact with the upper surface of the substrate 4 fixed to the substrate fixing unit 6. The sample water sampling pipe 10 is provided with a flow control valve 14 and a flow meter or pressure gauge 16 to control the flow rate of the sample water supplied to the substrate 4 by the flow control valve 14, Alternatively, the flow rate can be measured by the pressure gauge 16. The flow meter is preferably a flow meter without a sliding portion or a movable portion, for example, a vortex flow meter, or a non-contact type flow meter, for example, an ultrasonic flow meter. The installation place of the flow meter may be either upstream or downstream of the flow control valve 14. Also, in the flow measurement with a pressure gauge, if the pipe diameter is determined,
By monitoring the pressure, the flow rate can be calculated.

The sample water drying means includes an infrared light lamp 18 installed above the substrate 4 in the sampling vessel 8;
And a heater 20 built in the substrate fixing portion 6.
The sample water 12 supplied to the upper surface of the substrate 4 is continuously dried by heating and drying using the heat of the infrared light lamp 18 and the heater 20 so that the sample water 12 does not overflow from the substrate. In this case, the sample water is usually heated to about 80 to 90 ° C.

FIG. 2 is a schematic view showing another embodiment of the apparatus for collecting impurities in sample water according to the present invention. The impurity collecting apparatus 22 of this example is the same as the impurity collecting apparatus 2 of FIG. 1 except that the configuration of the sample water drying unit is changed. Therefore, in FIG. 2, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

In the impurity collecting apparatus 22 of this embodiment, the sampling container 24 is configured as a vacuum dryer. The sampling container 24 has a lid 25. The sampling container 24 increases the degree of vacuum in the container 24 by discharging the air in the container 24 to the outside of the container 24 through the suction pipe 26, whereby the sample water supplied to the upper surface of the substrate 4 by vacuum drying or the heater 20. 12 is continuously dried so as not to overflow from the substrate.

The evaluation of the quality of ultrapure water using the impurity collecting apparatus 2 of FIG. 1 or the impurity collecting apparatus 22 of FIG. 2 is performed, for example, as follows.

(1) Open the door 9 or the lid 25 of the sampling container 8 or 24, and
One or more substrates 4 are put into the sampling container 8 or 24 through the opening of the substrate 4 and the substrate 4 is fixed to the substrate fixing part 6. Then, the door 9 of the sampling container 8 or 24
Alternatively, the lid 25 is closed.

(2) Next, the sample water 12 is continuously dropped and brought into contact with the upper surface of the substrate 4 by the sample water supply means, and the sample water is continuously dried by the sample water drying means so that at least the sample water 12 does not overflow from the substrate. By performing the drying, the impurities contained in the sample water 12 continuously supplied to the substrate 4 are collected as residues on the substrate 4. Note that the supply means and the drying means successively form residues containing impurities without overflowing the sample water from the substrate, so that more impurities contained in the sample water can be collected.

(3) Next, a fixed amount of sample water is supplied,
Finally, after all the sample water on the substrate is dried, the door 9 or the lid 25 of the sampling container 8 or 24 is opened, and the substrate 4 is taken out of the sampling container 8 or 24 from the upper end opening of the sampling container 8 or 24. .

(4) Then, impurities in the sample water adhering to the substrate 4 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.

The above operations (1) to (4) are preferably performed in a highly clean atmosphere, for example, preferably in a clean room. In the case of the impurity collecting apparatus 2 of FIG. 1, the ULPA filter or the chemical filter 11 is used.
Is operated, the cleanliness in the apparatus can be increased, and it is preferable to operate in a clean room because the cleanliness becomes higher. When the ULPA filter or the chemical filter 11 is operated, the filter 1
The outside air is continuously taken in from an outside air intake located at the upper part of 1, and the outside air is passed through a filter 11 to be continuously discharged into a sampling container 8 from an outside air outlet (not shown). As a result, the air that has been processed by the filter 11 and from which impurities such as gas components and fine particles have been removed flows unilaterally from the top to the bottom in the sampling container 8, and the opening and closing door 9 is slightly displaced upward and therebelow. It flows out of the formed opening (not shown), and the sampling container 8
Inside is always kept clean.

[0030]

EXAMPLES (Example 1: Analysis of metals) Using the impurity collecting apparatus 2 shown in FIG. 1, sodium (1 ng / L), iron (1 ng / L) and copper (1 ng / L) of known concentrations were used as sample water.
The water quality of ultrapure water was evaluated in the same manner as in the above (1) to (4) except that the mixed solution containing L) was used. In this case, the substrate fixing table 6 of the impurity collecting apparatus 2 of FIG.
A silicon wafer with a natural oxide film was set as the substrate 4 on the substrate 4, sample water was continuously dropped on the substrate 4 and dried, and impurities in the sample water were collected on the substrate 4. The drop flow rate of the sample water was 1 mL / min. The impurity collection time (sample water dropping time) was 10 minutes, 24 hours, and 144 hours. That is, the sample water dripping amount is 10 mL, 1440 mL, 864
It was 0 mL. In the analysis of the impurities, the impurities deposited on the substrate were collected by using the WSA method, and sodium, iron, and copper were measured by using inductively coupled plasma mass spectrometry (ICP-MS method). The results are shown in Table 1.

[0031]

[Table 1]

(Example 2: Analysis of organic matter) Urea (1
ng / L) and acetic acid (1 ng / L), except that the quality of ultrapure water was evaluated in the same procedure as in the above (1) to (4). In this case, a silicon wafer with a natural oxide film is set as the substrate 4 on the substrate fixing table 6 of the impurity collecting apparatus 2 of FIG. 1, and the sample water is continuously dropped on the substrate 4 and dried to obtain impurities in the sample water. Was collected on the substrate 4. The drop flow rate of the sample water was 1 mL / min. The impurity collection time (sample water dropping time) was 24 hours, 144 hours.
Time. That is, the amount of sample water dropped is 1440 mL,
It was 8640 mL. In the analysis of impurities, the substrate was extracted with an extract, and urea was measured with a liquid chromatograph mass spectrometer and acetic acid was measured using the extract with a spectrophotometer. The results are shown in Table 2.

[0033]

[Table 2]

From Tables 1 and 2, according to the present invention, impurities contained in sample water such as ultrapure water are recovered at a high recovery rate, and the concentration of impurities contained in the sample water is accurately measured. It was confirmed that it was possible.

[0035]

As described above, according to the present invention, impurities contained in high-purity sample water, such as ultrapure water, are removed from at least the substrate while the sample water is continuously supplied to and brought into contact with the substrate. By using a means to dry so as not to overflow, it is possible to easily collect a certain amount of impurities contained in the sample water without contaminating the substrate, and to accurately measure the concentration of impurities contained in the sample water. The measurement can be performed well, and the influence of the sample water on the substrate can be correctly evaluated. Therefore, according to the present invention, of the impurities in ultrapure water used for cleaning a semiconductor substrate, etc., a residue component on the substrate, that is, a component affecting the substrate can be specified, and those components can be accurately determined. Can be measured.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an embodiment of an apparatus for collecting impurities in sample water according to the present invention.

FIG. 2 is a schematic diagram showing another embodiment of the apparatus for collecting impurities in sample water according to the present invention.

[Explanation of symbols]

 2 Impurity Sampling Device 4 Substrate 6 Substrate Fixing Section 8 Sampling Vessel 10 Sample Water Sampling Pipe 12 Sample Water 14 Flow Rate Control Valve 16 Flow Meter or Pressure Gauge 18 Infrared Light Lamp 20 Heater 22 Impurity Sampling Device 24 Sampling Vessel 26 Suction Pipe 30 Ultrapure water production equipment 40 sampling points

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Akiko Umeka 1-2-2-8 Shinsuna, Koto-ku, Tokyo Organo Corporation F-term (reference) 2G052 AA06 AB01 AB11 AC27 AC28 AD06 AD26 AD52 BA12 CA03 CA04 CA11 CA38 DA05 EB01 EB11 GA13 GA24 HA15 HA17 HA18 HC22 HC25 HC28 JA09 JA23

Claims (8)

[Claims] 1. A sample water is continuously supplied to a substrate, and the sample water is continuously dried to collect impurities contained in the sample water continuously supplied to the substrate as residues on the substrate. And analyzing the impurities on the substrate. 2. The method for evaluating water quality of a sample water according to claim 1, wherein the sample water is directly and continuously collected from a sampling point, and the sample water is continuously supplied to a substrate. 3. The method for evaluating water quality of sample water according to claim 1, wherein the sample water supplied to the substrate is continuously dried by heating drying or vacuum drying. 4. The method according to claim 1, wherein one or more selected from metals, organic substances, ions and fine particles are analyzed as impurities on the substrate. Water quality evaluation method for sample water. 5. A sampling container having therein a substrate fixing portion to which a substrate is fixed substantially horizontally, a sample water supply means for supplying sample water to an upper surface of the substrate fixed to the substrate fixing portion, Sample water drying means for drying the sample water present on the upper surface of the fixed substrate, wherein the sample water is continuously supplied to the upper surface of the substrate by the sample water supply means, and the sample water is dried by the sample water drying means. An apparatus for collecting impurities in sample water, wherein impurities contained in sample water continuously supplied to the substrate are collected as residues on the substrate by continuously drying the sample water. 6. A sample water supply means includes a sample water sampling pipe for directly and continuously sampling sample water from a sampling point, and supplies the sample water collected through the sample water sampling pipe to an upper surface of a substrate. The apparatus for collecting impurities in sample water according to claim 5, characterized in that: 7. The apparatus for collecting impurities in sample water according to claim 5, wherein the sample water drying means dries the sample water present on the upper surface of the substrate by heating drying or vacuum drying. 8. The apparatus for collecting impurities in sample water according to claim 5, wherein the inside of the sampling vessel has an atmosphere with high cleanliness.