JP2007085748A - Quality evaluation method and apparatus of water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a quality evaluation method of water capable of accurately evaluating an adhesion component or the amount thereof even if the content in water to be measured has the adhesion dependency to an evaluation substrate with respect to a passing water amount or time in the quality evaluation of water. <P>SOLUTION: Water to be measured are brought into contact with a plurality of evaluation substrates in a predetermined amount for a predetermined time and the deposit bonded to the evaluation substrate is analyzed to evaluate the quality of the water to be measured precisely even if there is the adhesion dependency of the content in the water to be measured to the evaluation substrate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to, for example, a water quality evaluation method and a water quality evaluation apparatus that analyze components and amounts of inclusions contained in water to be measured that adhere to an object.

Due to demands for improving product characteristics and yield, ultrapure water with high purity has recently been used as pure water used particularly in the fields of semiconductor manufacturing and chemical manufacturing. That is, it is required to remove components that may reduce the amount of impurities contained in pure water and have an adverse effect. When using pure water, it is essential to confirm that the required water quality is maintained. Usually, in the production of pure water, ions, metals, fine particles, viable bacteria, silica, total organic carbon (TOC), etc. contained in pure water are measured with various analyzers so that the content is below a certain level. The water quality is maintained and managed.
In particular, since impurities contained in pure water used for cleaning in the semiconductor field directly affect product quality and yield, accurate analysis is required. Conventionally, as a method of evaluating the quality of pure water, a method of collecting pure water from a pure water outlet and collecting it into a collection container, a method of analyzing online using a measuring instrument, and the like have been used. This measures and manages the water quality. This method of collecting pure water from a pure water outlet and collecting it in a collection container is a method of analyzing the quality of pure water itself, and therefore directly assessing the impact of the pure water on a specific object. I couldn't.

Therefore, instead of evaluating impurities contained in pure water, for example, when pure water is used as cleaning water, it is necessary to accurately evaluate impurities that actually affect the object to be cleaned. Therefore, as a method of analyzing impurities adhering to the surface of the silicon substrate in contact with pure water, after immersing the silicon substrate as a sample in a container storing pure water for a predetermined time, after removing the silicon substrate and drying, The natural oxide film formed on the silicon substrate is dissolved using hydrofluoric acid, and the resulting solution is evaporated to dryness to form a powder. After the powder is dissolved with a nitric acid solution, the solution is flameless atomic absorption. There has been proposed a method of quantitatively evaluating the amount of impurities adhering to a silicon substrate by analysis by a method.
In the above method, in order to accurately evaluate impurities adhering to the silicon wafer (substrate), a method of analyzing the impurities adhering to the surface of the silicon wafer after passing pure water through the entire container holding the silicon wafer for a certain period of time. Has been proposed (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2002-296269 (page 3, FIG. 1)

  The inventors have found that the components and amount of deposits adhering to the evaluation substrate vary depending on the amount of water flow and time. However, in the conventional evaluation method for analyzing deposits attached to the evaluation substrate surface after a certain period of time, not only the state of the water quality that changes from time to time but also the time when the contents in the measured water adhere to the evaluation substrate. Since the dependence is not taken into account, there is a problem that the inclusions released from the evaluation substrate on the way are not detected, and the analysis result is limited to only the deposits remaining on the evaluation substrate surface. . For this reason, there is a problem that the relationship between the result of the detected deposit and the yield of the product is not clear, and the causal relationship may not be accurately grasped.

  The present invention has been made in order to solve such problems, and even if the content in the water to be measured is dependent on the evaluation substrate with respect to the water flow rate and time, The purpose is to be able to accurately evaluate components and amounts.

  In order to solve the above-described problems, in the evaluation method according to the present invention, the water to be measured is brought into contact with each of a plurality of evaluation substrates for a predetermined amount of time for a predetermined time, and the adhered matter attached to the evaluation substrate is identified. Thus, the inclusions contained in the measured water are identified.

  According to the present invention, since the deposit on the evaluation substrate can be evaluated in a short time with the amount of contact with the measured water and the amount of contact with the measured water, it is included in the measured water in the actual use state. From the standpoint of how much inclusions are attached to the object, it is possible to accurately grasp the components of the inclusions in the measured water.

Embodiment 1 FIG.
FIG. 1 is a sectional view showing the configuration of a water quality evaluation apparatus according to Embodiment 1 of the present invention. FIG. 2 is a diagram illustrating an example of identification of deposits by the water quality evaluation apparatus according to the first embodiment.
In FIG. 1, 1 is a supply pipe for supplying pure water which is water to be measured, V1 is a valve attached to the supply pipe 1, 2a, 2b, ..., 2n branches the supply pipe 1. , Vn are valves attached to the distribution pipes 2a, 2b, ..., 2n, 3a, 3b, ..., 3n are distribution pipes 2a, 2b, .., Tn is a joint for connecting the distribution pipes 2a, 2b, 2n and the containers 3a, 3b, 3n, 4a, 4b,. 4n is an introduction pipe attached to the containers 3a, 3b, ..., 3n, 5a, 5b, ..., 5n is a lead-out pipe attached to the containers 3a, 3b, ..., 3n Yes, 6a, 6b, ..., 6n are in containers 3a, 3b, ..., 3n Re is installed in a silicon wafer, respectively. The lead-out pipes 5a, 5b,..., 5n-1 and the introduction pipes 4b,..., 4n are connected to the distribution pipes 2b,.

Next, the operation of the water quality evaluation apparatus in the first embodiment will be described.
The inventors have found that the deposit component and amount adhering to the evaluation substrate depend on the water flow rate and time. That is, depending on the content in the water to be measured, even if it is initially attached to the evaluation substrate, it may be released after a certain time. Alternatively, there are those that do not adhere unless they contact the evaluation substrate for a certain period of time. In consideration of this point, the first embodiment distributes the water to be measured and supplies it to a plurality of evaluation substrates at the same time, so that the components and amounts of deposits having time dependency can be accurately identified in a short time. It is a thing.
Pure water, which is the water to be measured, supplied from the supply pipe 1 is distributed to the distribution pipes 2a, 2b,..., 2n via the valve 1, and the joints Ta, Tb,. 4n are supplied to the containers 3a, 3b,..., 3n. The pure water adjusted by the valves Va, Vb, Vn is simultaneously supplied to the respective containers 3a, 3b,..., 3n with the same amount of pure water distributed through the introduction pipes 4a, 4b,. Supplied. Pure water is dropped on the center of the surface of the silicon wafers 6a, 6b,..., 6n installed horizontally in the containers 3a, 3b,. Fall from. It is discharged from the outlet pipes 5a, 5b,... Between each container, a lead-out pipe and an introduction pipe are connected in series, and pure water discharged from each container is sequentially sent to a subsequent container. Therefore, for example, if the amount of pure water supplied from each distribution pipe is 10 cc / second, the uppermost part is the first stage, and the subsequent and N-th stage silicon wafers have a water flow rate of 10 × Ncc / second. . Therefore, the amount of pure water that comes into contact with each silicon wafer surface is different.

An example in which the amount of pure water supplied from each pipe is 10 cc / second, the number of stages (the number of containers) is 6, and the deposits on the silicon wafer surface are identified by components when the water passage time is 1 hour. As shown in FIG. The peak area value for each molecule was normalized and shown on the vertical axis. According to this, the saturated aliphatic compound A represented by CnHm adheres a lot on the first-stage silicon wafer with a short contact time with pure water, and the adhering amount after the third stage where the contact time with pure water becomes long. It shows that it was released after being attached to the silicon wafer. The primary amine compound B represented by CnHm—NH ₃ increases in the amount of adhesion in the silicon wafer up to the third stage, and decreases in the silicon wafers in the subsequent stages. On the other hand, the tertiary amine compound C represented by (CnHm) ₃ -N, the carboxylic acid compound D represented by CnHm-COOH, and the metal element E such as Na increase the amount of adhesion as the silicon wafer in the subsequent stage. Thus, it is clear that the content contained in the pure water depends on the components, and the rate of adhesion to the silicon wafer depends on the amount of water that is in contact with the pure water and the time.
In the first embodiment, the optimum value of the amount of water supplied to the silicon wafer varies depending on the wafer size, but may be an amount that wets the entire surface of the silicon wafer, and is preferably 3 to 30 cc / second. Further, if the water passage time is in the range of 30 minutes to 180 minutes, the respective contents can be adhered.
Therefore, by optimizing the amount of water flow according to the content to be identified, it is possible to accurately identify the components contained in the measured water. Here, it is effective to use a ToF-SIMS (Time of Flight Secondary Ion Mass Spectrometry) analyzer that can identify a component of a substance with high accuracy.

  In the water quality evaluation method and the water quality evaluation apparatus shown in the first embodiment of the present invention, the evaluation boards having different water flow conditions can be obtained by connecting the containers for putting the evaluation boards in series and supplying the water to be measured to each. You can get it at once. As a result, there is an effect that it is possible to accurately identify the dependency of the component adhering to the evaluation substrate from the inclusion contained in the measured water with a small amount of measured water in a short time. In the conventional measurement of only a constant water flow rate, it is possible to identify all the inclusions that have been difficult to detect, and the inclusion of the water to be measured can be identified with higher accuracy.

Embodiment 2. FIG.
FIG. 3 shows a sectional view of the configuration of the water quality evaluation apparatus according to Embodiment 2 of the present invention.
The second embodiment shows another embodiment that realizes a state in which the surface of the silicon wafer and the water to be measured are in contact with each other from the same water to be measured at different water flow rates.
In FIG. 3, 11 is a supply pipe for supplying pure water 18 to be measured, V1 is a valve attached to the supply pipe 11, 17 is a tank for storing pure water 18, 12a, 12b,. .., 12n are distribution pipes for distributing the pure water 18 of the tank 17 from the supply pipe 1, Va, Vb,..., Vn are valves attached to the distribution pipes 12a, 12b,. , 13n are containers attached to the distribution pipes 12a, 12b, ..., 12n, and 14a, 14b, ..., 14n are containers 13a, 13b, ..., 14n, respectively. .., 15n are outlet pipes attached to the containers 13a, 13b,..., 13n, and 16a, 16b,. 13a, 1 b, · · ·, respectively installed silicon wafer in 13n. Reference numeral 19 denotes a drain pipe to which the tank 17 is attached, and 20 denotes a drain valve attached to the drain pipe 19.

Next, the operation of the water quality evaluation apparatus in the second embodiment will be described.
Containers 13a, 13b,... Containing silicon wafers 16a, 16b,..., 16n through a plurality of distribution pipes 12a, 12b,. Pure water is supplied to 13n independently. By adjusting the valves Va, Vb,..., Vn, pure water is brought into contact with the silicon wafers 16a, 16b,. ..Attachment adhered to 16n is identified by an analyzer.

  In the water quality evaluation method and the water quality evaluation apparatus shown in the second embodiment of the present invention, the containers for storing the evaluation substrates are directly connected to the tanks, and the amount of water to be measured supplied to each container is changed to change the water quality. Evaluation boards with different amounts of water can be obtained at once. As a result, it is possible to accurately identify the inclusions contained in the measured water that is dependent on the water flow rate attached to the evaluation substrate in a short time, and to enable the identification of the inclusions contained in the measured water. There is. Further, in the second embodiment, the flow rate and time of the water to be measured can be adjusted independently by opening and closing the valve, and evaluation can be performed by focusing on a specific type of content in the water to be measured. Is possible. Specifically, for example, as described in the first embodiment, the saturated aliphatic compound, the primary amine compound, the tertiary amine compound, the carboxylic acid compound, and the metals are different in the amount of adhesion depending on the amount of water flow and time. Among these inclusions, the effect of enabling efficient identification of inclusions can be expected by changing the required number of measurement substrates, the amount of water to flow, and the time according to the inclusion to be identified.

  In the first and second embodiments, for example, when a silicon wafer is used as an evaluation substrate and inclusions contained in pure water used as cleaning water for the silicon wafer are identified, it is actually used. Because it is possible to accurately identify deposits that adhere to silicon wafers, it is possible to accurately grasp the impact of inclusions on product yield when manufacturing semiconductor devices, and to clarify the relationship between inclusions and yields There is also an effect that can be done.

  In the first and second embodiments, the case where a silicon wafer is used as the evaluation substrate has been described. Needless to say, the present invention can also be applied to other semiconductor substrates, glass substrates, ceramic substrates, electronic components, and the like. Moreover, although the example of pure water was shown about to-be-measured water, this evaluation method can also be applied to the identification of the inclusion contained not only in pure water but normal water.

  In addition, the ToF-SIMS analyzer that can identify the component with high accuracy is used as the means for analyzing the deposit on the evaluation substrate in the first and second embodiments. However, other analyzers such as a flameless atomic absorption method may be used. May be.

  Furthermore, in Embodiments 1 and 2, by identifying the content of the water to be measured by deriving the difference between the component of the deposit on the evaluation board and the component of the water to be measured in the reference water, It can also be applied to water quality management of measured water.

1 is a configuration cross-sectional view of a water quality evaluation apparatus in Embodiment 1. FIG. It is a figure which shows the example of identification of the deposit | attachment using the water quality evaluation apparatus in Embodiment 1. FIG. It is a structure sectional view of the water quality evaluation apparatus in Embodiment 2.

Explanation of symbols

2a, 2b, ..., 2n, 12a, 12b, ..., 12n distribution pipes 3a, 3b, ..., 3n, 13a, 13b, ..., 13n containers 4a, 4b, ..., 4n , 14a, 14b, ..., 14n Inlet pipes 5a, 5b, ..., 5n, 15a, 15b, ..., 15n Outlet pipes 6a, 6b, ..., 6n, 16a, 16b, ... , 16n Silicon wafer Va, Vb, ..., Vn valve

Claims (8)

The measured water distributed to the plurality of evaluation boards arranged in multiple stages is dropped on each evaluation board surface, and the measurement water dropped on the upper evaluation board is also dropped on the lower evaluation board surface. A water quality evaluation method characterized in that the components of the inclusions in the measured water are analyzed by dropping them together and identifying the components of the deposits adhering to the respective evaluation substrates. The water quality evaluation method according to claim 1, wherein a supply amount of the distributed measured water to each evaluation substrate is 3 to 30 cc / second. The deposits attached to the evaluation substrate are classified into saturated aliphatic compounds, primary amine compounds, tertiary amine compounds, carboxylic acid compounds and metals, and the deposits are identified for each classification component by the ToF-SIMS method. The water quality evaluation method according to claim 1, wherein 3. The water quality evaluation method according to claim 1, wherein the difference between the identification component of the deposit on the evaluation substrate in the reference water and the identification component of the deposit on the evaluation substrate in the water to be measured is derived. . A plurality of containers each storing a plurality of evaluation boards;
Piping connecting the plurality of containers in series;
A distribution pipe that distributes the water to be measured and supplies the measured water individually to the lowermost containers in order from the uppermost stage of the plurality of containers;
An analysis means for identifying deposits adhering to the surface of the plurality of evaluation substrates. The water quality evaluation apparatus according to claim 5, wherein a distribution pipe to which the valve is attached and a pipe for connecting the containers in series are connected. A plurality of containers each storing a plurality of evaluation boards;
A distribution pipe that distributes the water to be measured and supplies it individually to the plurality of containers;
An analysis means for identifying deposits adhering to the surface of the plurality of evaluation substrates. The water quality evaluation apparatus according to claim 7, wherein supply amounts of water to be measured supplied to the plurality of containers are different from each other.

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