Hydrogencarbonate Water and Cleaning Method Using Same

Abstract

The present invention relates to hydrogencarbonate water and a cleaning method using the hydrogencarbonate water. Provided are hydrogencarbonate water obtained by dissolving carbon dioxide in hydrogen water having a dissolved hydrogen concentration of 0.1 ppm to 2.0 ppm; and a cleaning method comprising cleaning a substrate by immersing the substrate in the hydrogencarbonate water, or spraying the hydrogencarbonate water to the substrate.

Claims

1. A hydrogencarbonate water obtained by dissolving carbon dioxide in hydrogen water having a dissolved hydrogen concentration of 0.1 ppm to 2.0 ppm.

2. The hydrogencarbonate water according to claim 1, wherein the hydrogen water has a pH of 5.5 to 6.8, an oxidation-reduction potential of 200 mV to 700 mV and a dissolved hydrogen concentration of 0.1 ppm to 2.0 ppm.

3. The hydrogencarbonate water according to claim 1, wherein the hydrogen water is hydrogen water obtained by dissolving hydrogen gas in pure water or ultrapure water, or hydrogen water obtained by electrolyzing pure water or ultrapure water.

4. A hydrogencarbonate water having a pH of 4.0 to 6.8, an oxidation-reduction potential of 50 mV to 650 mV and an electric conductivity of 0.072 S/cm to 80 S/cm.

5. The hydrogencarbonate water according to claim 1, wherein the hydrogencarbonate water has a pH of 4.0 to 6.8, an oxidation-reduction potential of 50 mV to 650 mV and an electric conductivity of 0.072 S/cm to 80 S/cm.

6. A cleaning method comprising cleaning a substrate by immersing the substrate in a hydrogencarbonate water obtained by dissolving carbon dioxide in hydrogen water having a dissolved hydrogen concentration of 0.1 ppm to 2.0 ppm, or spraying to the substrate the hydrogencarbonate water according to.

7. The cleaning method according to claim 6, wherein the substrate is cleaned by spraying the hydrogencarbonate water to the substrate for 5 to 10 minutes while rotating the substrate at 80 to 300 rpm and applying a megasonic at 1 to 3 MHz to the hydrogencarbonate water.

8. The cleaning method according to claim 6, wherein the hydrogencarbonate water is preheated at 40 C. to 85 C.

9. The hydrogencarbonate water according to claim 2, wherein the hydrogen water is hydrogen water obtained by dissolving hydrogen gas in pure water or ultrapure water, or hydrogen water obtained by electrolyzing pure water or ultrapure water.

10. The hydrogencarbonate water according to claim 3, wherein the hydrogencarbonate water has a pH of 4.0 to 6.8, an oxidation-reduction potential of 50 mV to 650 mV and an electric conductivity of 0.072 S/cm to 80 S/cm.

11. The cleaning according to claim 6, wherein the hydrogen water has a pH of 5.5 to 6.8, an oxidation-reduction potential of 200 mV to 700 mV and a dissolved hydrogen concentration of 0.1 ppm to 2.0 ppm and is used for immersing or spraying the substrate.

12. The cleaning according to claim 6, wherein the hydrogencarbonate water obtained by dissolving carbon dioxide in hydrogen water having a dissolved hydrogen concentration of 0.1 ppm to 2.0 ppm and the hydrogen water is hydrogen water obtained by dissolving hydrogen gas in pure water or ultrapure water, or hydrogen water obtained by electrolyzing pure water or ultrapure water and is used for immersing or spraying the substrate.

13. The cleaning according to claim 6, wherein the hydrogencarbonate water has a pH of 4.0 to 6.8, an oxidation-reduction potential of 50 mV to 650 mV and an electric conductivity of 0.072 S/cm to 80 S/cm and is used for immersing or spraying the substrate.

14. The cleaning according to claim 6, wherein the hydrogencarbonate water obtained by dissolving carbon dioxide in hydrogen water having a dissolved hydrogen concentration of 0.1 ppm to 2.0 ppm and has a pH of 4.0 to 6.8, an oxidation-reduction potential of 50 mV to 650 mV and an electric conductivity of 0.072 S/cm to 80 S/cm and is used for immersing or spraying the substrate.

15. The cleaning according to claim 6, wherein the wherein the hydrogen water has a pH of 5.5 to 6.8, an oxidation-reduction potential of 200 mV to 700 mV and a dissolved hydrogen concentration of 0.1 ppm to 2.0 ppm that is obtained by dissolving hydrogen gas in pure water or ultrapure water, or hydrogen water obtained by electrolyzing pure water or ultrapure water and is used for immersing or spraying the substrate.

16. The cleaning according to claim 6, wherein the hydrogen water is hydrogen water obtained by dissolving hydrogen gas in pure water or ultrapure water, or hydrogen water obtained by electrolyzing pure water or ultrapure water and wherein the hydrogencarbonate water has a pH of 4.0 to 6.8, an oxidation-reduction potential of 50 mV to 650 mV and an electric conductivity of 0.072 S/cm to 80 S/cm and is used for immersing or spraying the substrate.

17. A Hydrogencarbonate water having a pH of 4.0 to 6.8, an oxidation-reduction potential of 200 mV to 700 mV, a dissolved hydrogen concentration of 0.1 ppm to 2.0 ppm and an electric conductivity of 0.072 S/cm to 80 S/cm.

Description

BRIEF DESCRIPTION OF DRAWING

[0030] FIG. 1 is a schematic view of an example of an electrolysis apparatus usable for production of hydrogen water in the present invention.

MODE OF CARRYING OUT THE INVENTION

[0031] Hydrogencarbonate water of the present invention is obtained by dissolving carbon dioxide in hydrogen water having a dissolved hydrogen concentration of 0.1 ppm to 2.0 ppm. In addition, in the hydrogencarbonate water of the present invention, it is preferable that the hydrogen water in which carbon dioxide is dissolved has a pH of 5.5 to 6.8, an oxidation-reduction potential of 200 mV to 700 mV and a dissolved hydrogen concentration of 0.1 ppm to 2.0 ppm. The oxidation-reduction potential of the hydrogen water is more preferably 200 mV to 650 mV. In addition, in the hydrogencarbonate water of the present invention, hydrogen water having a dissolved hydrogen concentration of 0.1 ppm to 2.0 ppm, or hydrogen water having a pH of 5.5 to 6.8, an oxidation-reduction potential of 200 mV to 700 mV and a dissolved hydrogen concentration of 0.1 ppm to 2.0 ppm as well as the hydrogen water having an oxidation-reduction potential of 200 mV to 650 mV is preferably hydrogen water obtained by dissolving hydrogen gas in pure water or ultrapure water, or hydrogen water obtained by electrolyzing pure water or ultrapure water. In addition, it is preferable that the hydrogencarbonate water of the present invention has a pH of 4.0 to 6.8, an oxidation-reduction potential of 50 mV to 650 mV and an electric conductivity of 0.072 S/cm to 80 S/cm. The oxidation-reduction potential of the hydrogencarbonate water of the present invention is more preferably 300 mV to 650 mV, still more preferably 400 mV to 650 mV. The electric conductivity of the hydrogencarbonate water of the present invention is more preferably 10 S/cm to 80 S/cm, still more preferably 10 S/cm to 60 S/cm. The hydrogencarbonate water having these characteristics can be obtained by dissolving carbon dioxide in the above hydrogen water.

[0032] The object to be cleaned by a cleaning method of the present invention is not particularly limited, but the cleaning method can be suitably used for cleaning a substrate such as a substrate to be used in preparation of a semiconductor wafer, an organic EL (OLED), a photomask, an LCD, a hard disk or the like. In the cleaning method of the present invention, a substrate to be cleaned is immersed in the hydrogencarbonate water of the present invention, or the hydrogencarbonate water of the present invention is sprayed to the substrate, whereby the substrate can be cleaned. In addition, in the cleaning method of the present invention, it is preferable that the substrate is cleaned by spraying the hydrogencarbonate water to the substrate for 5 to 10 minutes while rotating the substrate at 80 to 300 rpm and applying a megasonic at 1 to 3 MHz to the hydrogencarbonate water of the present invention. In addition, in the cleaning method of the present invention, it is preferable that the hydrogencarbonate water of the present invention is preheated at 40 C. to 85 C., and used, and it is more preferable that the hydrogencarbonate water of the present invention is preheated at 50 C. to 85 C., and used. In the cleaning method of the present invention, fine particles as a contaminating substance can be removed at a removal ratio of 80% or more, or 90% or more.

[0033] Hereinafter, preferred examples of the present invention will be described in more detail with reference to attached drawings. It is to be noted in advance that the terms and words used in the description of the present application and claims should not be interpreted as common or having indeterminate meanings in a limited way, and should be interpreted with meanings and concepts consistent with the technical idea of the present invention on the basis of the principle that the inventor can appropriately define concepts of terms for explaining the invention of the inventor himself or herself in an optimum manner.

[0034] Therefore, it should be understood that since examples described in the description of the present application and configurations shown in the drawings are merely the most desirable examples of the present invention, and do not represent all aspects of the technical idea of the present invention, various equivalents and modifications substitutable for these examples may exist at the time of filing the present application.

[0035] In the method of cleaning a substrate according to the present invention, the substrate is cleaned using hydrogencarbonate water. Thus, the hydrogencarbonate water will be first described here, and the cleaning method using the hydrogencarbonate water will be described later. Hereinafter, the pH and oxidation-reduction potential (ORP), the electric conductivity, the carbon dioxide concentration and the dissolved hydrogen concentration were measured using the following devices, respectively.

[0036] (1) pH and oxidation-reduction potential (ORP): HM-31P from DKK-TOA Corporation

[0037] (2) Electric conductivity: CM-21PW from TOA Corporation

[0038] (3) Carbon dioxide concentration: 7515 from TSI

[0039] (4) Dissolved hydrogen concentration: DH-35A from DKK-TOA Corporation

[0040] (Production of Hydrogencarbonate Water)

[0041] The hydrogencarbonate water of the present invention can be obtained by dissolving carbon dioxide (CO.sub.2) in hydrogen water. At this time, as the hydrogen water, hydrogen water obtained by dissolving hydrogen gas in purified water with an electric conductivity of 50 S or less, such as pure water or ultrapure water, or electrolyzing the purified water can be suitably used. The hydrogen water is preferably hydrogen water having a dissolved hydrogen concentration of 0.1 ppm to 2.0 ppm. Further, the hydrogen water in the present invention is preferably hydrogen water obtained by electrolyzing purified water with an electric conductivity of 50 S/cm or less, such as pure water or ultrapure water. Particularly, in a preferred embodiment, it is preferable that the hydrogen water obtained in this manner has a pH of 5.5 to 6.8, an oxidation-reduction potential (ORP) of 200 mV to 700 mV and a dissolved hydrogen concentration of 0.1 ppm to 2.0 ppm. As the hydrogencarbonate water obtained by dissolving carbon dioxide (CO.sub.2) in the hydrogen water, one having a pH of 4.0 to 6.8, an oxidation-reduction potential of 50 mV to 650 mV and an electric conductivity of 0.072 S/cm to 80 S/cm can be preferably used. The concentration of carbon dioxide (CO.sub.2) in the hydrogencarbonate water is preferably 0.1 ppm to 2.0 ppm, more preferably 0.5 ppm to 2.0 ppm.

[0042] When hydrogen water is to be obtained by electrolyzing purified water with an electric conductivity of 50 S/cm or less, such as pure water or ultrapure water, the electrolysis method is not particularly limited as long as hydrogen water having a dissolved hydrogen concentration of 0.1 ppm to 2.0 ppm can be obtained, and for example, a method can be suitably shown which uses an electrolysis apparatus (FIG. 1) in which two cathode plates are placed with one anode plate held therebetween, a cation-exchange membrane is provided on one cathode plate side of the anode plate with the membrane in contact with the side, an electrically conductive plate with the cation-exchange membrane provided on the anode plate side with the membrane in contact with the side and with a large number of minute pores drilled in the electrically conductive plate is provided between a pair of electrode plates (between the anode plate and one cathode plate and between the anode plate and the other cathode plate), water is caused to flow separately between the anode plate and the electrically conductive plate and between the cathode plate and the electrically conductive plate, and treated water flowing between the cathode plate and the electrically conductive plate is utilized.

[0043] Thus, the hydrogencarbonate water of the present invention, which is obtained by dissolving carbon dioxide (CO.sub.2) in hydrogen water obtained by dissolving hydrogen gas in purified water or electrolyzing purified water, has a pH of 4.0 to 6.8, and hence acidity higher than that of hydrogen water having a pH of 5.5 to 6.8, and particularly, while existing carbonated water has oxidizing power in terms of an oxidation-reduction potential (ORP), the hydrogencarbonate water of the present invention has reducing power (50 mV to 650 mV) in terms of the ORP, so that generation of an oxide film in patterns formed on a substrate at the time of cleaning the substrate is prevented.

[0044] (Cleaning of Substrate)

[0045] One embodiment of a process of cleaning a substrate using the hydrogencarbonate water of the present invention is as follows. First, the substrate is cleaned by spin cleaning in which the substrate is cleaned while being rotated at a predetermined rotation speed. At this time, the substrate is rotated at a speed of preferably 80 to 300 rpm. On the other hand, to a surface of the substrate which is rotated in this manner, the hydrogencarbonate water of the present invention is sprayed using a nozzle or the like. At this time, by applying a megasonic at 1 to 3 MHz to give high-frequency energy to the hydrogencarbonate water, energy of high-frequency vibration or the like can be utilized to uniformly clean the entire substrate by this energy. The hydrogencarbonate water is continuously sprayed for 5 to 10 minutes. In addition, as another embodiment, mention is made of a method in which the substrate is immersed in a container filled with the hydrogencarbonate water of the present invention, or a method in which in the foregoing method, a megasonic at 1 to 3 MHz is applied to the hydrogencarbonate water in the container.

[0046] In this way, improvement of the yield and improvement of quality can be achieved by removing organic substances and fine particle impurities on a surface of the substrate, and particularly, since a chemical agent is not used, and therefore there is no rinsing step, the cleaning step can be simplified. Further, formation of an oxide film on patterns formed on the substrate is suppressed through reducing power of the hydrogencarbonate water, so that improvement of quality can be expected together with a cleaning effect. In a preferred embodiment of the present invention, it is preferable that the hydrogencarbonate water is preheated at a predetermined temperature, preferably 40 C. to 85 C., more preferably 50 C. to 85 C., and used for cleaning in the cleaning method of the present invention. This is because in this range, the hydrogencarbonate water exhibits the highest oxidation-reduction potential, and resultantly has the strongest reducing power.

Example 1

[0047] (Example of Production of Hydrogencarbonate Water)

[0048] First, ultrapure water was electrolyzed to obtain hydrogen water. The hydrogen water at this time had a pH of 6.5 and an oxidation-reduction potential of 683 mV.

[0049] Subsequently, the hydrogen water was added in an airtight container, and 2 ppm of carbon dioxide (CO.sub.2) was dissolved in the hydrogen water to obtain hydrogencarbonate water. The hydrogencarbonate water at this time had a pH of 4.6, an oxidation-reduction potential (ORP) of 470 mV and an electric conductivity of 43.2 S/cm.

[0050] (Property Change Depending on Carbon Dioxide Concentration)

[0051] The results of comparing the changes of the pH, the oxidation-reduction potential (ORP) and the electric conductivity based on the concentration of carbon dioxide (CO.sub.2) in the hydrogen water and hydrogencarbonate water obtained in this manner are as shown in Table 1. From Table 1, it is apparent that as the concentration of carbon dioxide was increased, higher acidity was exhibited, it was possible to have reducing power although the oxidation-reduction potential was slightly reduced, and the electric conductivity was rapidly increased.

TABLE-US-00001 TABLE 1 CO.sub.2 concentration 0 ppm 0.5 ppm 1 ppm pH 6.5 5.2 4.5 ORP (mV) 680 510 437 Electric conductivity (S/cm) 0.25 15 45

Example 2

[0052] (Example of Cleaning of Substrate)

[0053] A silicon wafer oxidized with ozone water was contaminated with Al.sub.2O.sub.3 and a CMP slurry at a density of 5,000 contaminants per wafer, and hydrogencarbonate water at normal temperature (pH: 4.9, ORP: 500 mV, electric conductivity: 18 S/cm) obtained by the same method as in Example 1 was then sprayed to a surface of the substrate by a spray nozzle system while the substrate was rotated at 80 rpm. At this time, a megasonic at 2 MHz was applied, and the spraying was continued for 8 minutes. As a result, contaminating substances (>0.07 m) were removed at a removal ratio of 80% or more.

INDUSTRIAL APPLICABILITY

[0054] The hydrogencarbonate water of the present invention can be suitably used as a cleaning liquid for a substrate to be used particularly in preparation of a semiconductor wafer, an organic EL (OLED), a photomask, an LCD, a hard disk or the like. The cleaning method of the present invention can be suitably used for cleaning a substrate to be used particularly in preparation of a semiconductor wafer, an organic EL (OLED), a photomask, an LCD, a hard disk or the like.