Ozone water production method and ozone water production system

Abstract

To provide an ozone water producing and an ozone water producing system capable of producing ozone water from which metal components have been sufficiently removed.SOLUTION: Ozone is dissolved in ultra pure water to produce ozone water, and metal components are removed from the ozone water by ion exchange treatment.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This application relates to a method for producing ozone water and an ozone water production system.

Background Art

[0002] In recent years, ozone water has been used, for example, in surface cleaning and surface treatment of silicon wafers in semiconductor manufacturing processes.

[0003] For example, Patent Document 1 shows an example in which a Si-H bond is formed on the surface of a mirror-finished silicon wafer, and ozone or hydrogen peroxide water is allowed to act on the surface of this silicon wafer to form an oxide film of only one atomic layer.

[0004] Patent Document 2 describes a method in which when polishing of the wafer surface with a polishing liquid approaches completion, the supply of the polishing liquid is stopped, and at the same time, a rinse liquid is supplied to remove abrasive grains from the wafer surface. As an oxidizing agent contained in the rinse liquid, ozone water is exemplified.

[0005] Patent Document 3 describes that, as an example of cleaning for making the surface of a silicon wafer hydrophilic, cleaning with a mixed liquid of a small amount of hydrofluoric acid and ozone water is used.

[0006] Generally, ozone water is often used in the cleaning process of silicon wafers, and is widely used, for example, in device formation processes on silicon wafers such as resist stripping. However, in such device formation processes, wirings, resists, etc. are present on the surface of the silicon wafer. In the cleaning process of the silicon wafer, when, for example, these wirings, resists, etc. are peeled off and removed, the resist is mixed into the stripping agent. Therefore, even if impurities are present in the ozone water used as the stripping agent, these impurities have not been a problem.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] In part of the semiconductor manufacturing process, ozone water as described above is used in the removal of resist from silicon wafers, pattern formation, etc.

[0009] By the way, in a silicon wafer with a mirror-finished surface, it is required that the impurities on this surface are extremely few. Accordingly, it is necessary that the impurities contained in the ozone water are also extremely few. In particular, in the future, as the semiconductors to be manufactured become more miniaturized, this tendency is expected to become more prominent. However, ozone water with the metal components sufficiently removed to be suitably used in a semiconductor manufacturing process for such silicon wafers, etc. does not actually exist.

[0010] For example, Patent Document 1 describes that by immersing a silicon wafer in ozone water of 8 ppm for 5 seconds, a single layer of natural oxide film is formed on the surface, but does not describe the concentration of metal components in the ozone water.

[0011] Patent Document 2 describes that the content of the oxidizing agent in the rinse liquid is determined such that the oxidation-reduction potential of the rinse liquid becomes 10 mV or more, but does not describe the concentration of metal components in the ozone water.

[0012] Also in Patent Document 3, the concentration of metal components in the ozone water is not described.

[0013] There is no ozonated water with metal components removed to such an extent that it can be used for cleaning and processing a silicon wafer with a mirror-finished surface. Also, there is no manufacturing method or manufacturing system for ozonated water with metal components sufficiently removed.

[0014] An object of the present application is to obtain an ozonated water production method and an ozonated water production system capable of producing ozonated water with metal components sufficiently removed.

Means for Solving the Problem

[0015] In the ozonated water production method of the first aspect, ozone is dissolved in ultrapure water to produce ozonated water, and metal components are removed from the ozonated water by ion exchange treatment.

[0016] In this ozonated water production method, ozone is dissolved in ultrapure water to produce ozonated water. At this stage, ozonated water with a sufficient amount of ozone dissolved can be obtained as the ozone concentration.

[0017] However, the ozonated water thus obtained may contain metal components such as iron and titanium in addition to ozone. For the surface cleaning and surface treatment of a silicon wafer with a mirror-finished surface, ionized water containing a large amount of such metal components may be unsuitable in some cases.

[0018] In the ozonated water production method of the first aspect, metal components are removed from the obtained ozonated water by ion exchange treatment. Thereby, it is possible to produce ozonated water in which an amount of ozone necessary for surface cleaning and surface treatment of a silicon wafer with a mirror-finished surface is dissolved and the metal components are sufficiently removed.

[0019] The degree of removal of metal components by the ion exchange treatment only needs to be sufficient for use in surface cleaning and surface treatment of a silicon wafer with a mirror-finished surface. For example, in the second aspect, in the ion exchange treatment, the iron concentration of the ozone water is set to 0.01 μg / L or less. In other words, for surface cleaning and surface treatment of a silicon wafer with a mirror-finished surface, ozone water in which metal components have been removed to such an extent that the iron concentration is 0.01 μg / L or less can be used without problems.

[0020] In the third embodiment, ion exchange fibers are used in the ion exchange treatment.

[0021] Thereby, for example, compared with a configuration using an ion exchange resin in the ion exchange treatment, metal components can be efficiently removed from the ozone water.

[0022] The ozone water production system of the fourth aspect includes an ultrapure water production device for producing ultrapure water, an ozone dissolution device for dissolving ozone in the ultrapure water produced by the ultrapure water production device to obtain ozone water, and an ion exchange device for removing metal components from the ozone water by ion exchange treatment.

[0023] In this ozone water production system, ultrapure water is produced by the ultrapure water production device, and the produced ultrapure water is dissolved with ozone by the ozone dissolution device to produce ozone water. At this stage, ozone water in which a sufficient amount of ozone is dissolved can be obtained as the ozone concentration.

[0024] However, the ozone water thus obtained may contain metal components such as iron and titanium in addition to ozone. For surface cleaning and surface treatment of a silicon wafer with a mirror-finished surface, such ion water containing a large amount of metal components may be unsuitable in some cases.

[0025] In the ozone water production system of the fourth aspect, metal components are removed from the ozone water obtained by the ozone dissolution device using an ion exchange device. As a result, it is possible to produce ozone water in which an amount of ozone necessary for surface cleaning and surface treatment of a silicon wafer with a mirror-finished surface is dissolved, and the metal components are sufficiently removed.

[0026] The degree of removal of metal components by the ion exchange device only needs to be sufficient for use in surface cleaning and surface treatment of a silicon wafer with a mirror-finished surface. For example, in the fifth aspect, in the ion exchange device, the metal components are removed until the iron concentration of the ozone water becomes 0.01 μg / L or less. In other words, for surface cleaning and surface treatment of a silicon wafer with a mirror-finished surface, ozone water in which the metal components are removed to such an extent that the iron concentration is 0.01 μg / L or less can be used without problems.

[0027] In the sixth embodiment, the ion exchange device includes ion exchange fibers.

[0028] As a result, compared with a configuration using an ion exchange resin as the ion exchange device, for example, metal components can be efficiently removed from ozone water.

Advantages of the Invention

[0029] In the present application, an ozone water production method and an ozone water production system capable of producing ozone water from which metal components have been sufficiently removed are obtained.

Brief Description of the Drawings

[0030]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0031] Hereinafter, the ozone water production system 12 of the first embodiment will be described with reference to the drawings.

[0032] As shown in FIG. 1, the ozone water production system 12 of the first embodiment includes an ultrapure water production device 14, a deaeration device 16, an ozone dissolution device 18, an ion exchange device 20, and a use point 22. And ozone water in which ozone is dissolved at a predetermined concentration can be obtained from raw water. As applications of this ozone water, for example, there is a semiconductor manufacturing process for performing surface cleaning and surface treatment of a silicon wafer whose surface has been mirror-finished. Here, “mirror surface” means that the surface of the silicon wafer has an arithmetic mean roughness (Ra) of 4 nm or less as defined in JIS B0601-2013 (or ISO13565-1), for example. This arithmetic mean roughness (Ra) can be measured under the following conditions as an example. · Fine shape measuring device: P16-OF manufactured by KLA Tencor · Measurement mode: Roughness · Measurement length: 200 μm · Measurement speed: 5 μm / sec · Measurement load: 1 mg The arithmetic mean roughness (Ra) is a value (integrated value per unit length) obtained by integrating the absolute value of the difference between the reference line and the unevenness, with the average value of the heights of the unevenness as a reference within the measurement length range on the surface of the object, and dividing by the measurement length.

[0033] The ultrapure water production device 14 removes impurities from the supplied raw water and produces ultrapure water. Examples of the raw water include industrial water, tap water, groundwater, river water, and the like.

[0034] The ultrapure water production device 14 has a configuration including, for example, a pretreatment device, a primary pure water device, a pure water tank, and a secondary pure water device.

[0035] The pretreatment device pretreats the raw water used for the production of ultrapure water. That is, for the supplied raw water, the raw water is deflocculated using a coagulation sedimentation device, a sand filtration device, a membrane filtration device, a desalination device, etc., to obtain pretreated water in which a part of the impurities such as suspended substances and organic substances has been removed.

[0036] In the primary pure water device, for the pretreated water obtained by the pretreatment device, further treatments such as adsorption, filtration, and ion exchange are performed to remove the impurities that could not be completely removed by the pretreatment device, and to obtain primary pure water.

[0037] The primary pure water obtained by the primary pure water device is sent to a pure water tank and temporarily stored. In the secondary pure water device, for the temporarily pure water sent from the pure water tank, various treatments such as decomposition and sterilization of organic substances by ultraviolet irradiation, adsorption, filtration, and ion exchange are performed, and the impurities that could not be completely removed by the primary pure water device are further removed to produce ultrapure water.

[0038] The degassing device 16 is a device that removes gases such as dissolved oxygen from ultrapure water. For example, a configuration can be cited in which a gas separation membrane that allows gases to permeate but does not allow water to permeate is used to remove the gases in the ultrapure water, particularly dissolved oxygen. Note that such a degassing device (membrane degassing device) may be included in, for example, the secondary pure water device. Also, even if the degassing treatment by the degassing device 16 is not performed, there may be cases where the amount of dissolved gas is low enough not to cause problems when using ozone water. In such cases, a configuration that does not perform the degassing treatment by the degassing device 16 may also be adopted.

[0039] The ozone dissolution device 18 is a device that dissolves ozone in the ultrapure water degassed by the degassing device 16.

[0040] The specific method of dissolving ozone in ultrapure water is not particularly limited. For example, a membrane dissolution method, a tank dissolution method, a non-circulation method, a circulation method, etc. can be used. In a membrane dissolution type ozone dissolution device, a gas to be dissolved (ozone gas in this application) is diffused and dissolved in ultrapure water using a gas permeable membrane. In a tank dissolution type ozone dissolution device, with ultrapure water and ozone contained in a tank, the tank is controlled to a predetermined internal pressure to dissolve ozone in the ultrapure water. In this case, the ultrapure water may be sequentially moved to a plurality of tanks with gradually reduced internal pressure, while dissolving ozone in the ultrapure water. Thereby, ozone water in which ozone is dissolved at a predetermined concentration in the ultrapure water is obtained. Also, the circulation method is a method in which ozone water that was not used at the use point 22 among the produced ozone water is returned to any process in the ozone water production process and reused. In contrast, the non-circulation method is a method in which ozone water that was not used at the use point 22 among the produced ozone water is not returned to any process in the ozone water production process.

[0041] The ion exchange device 20 is a device that performs an ion exchange treatment on the ozone water obtained by dissolving ozone in the ozone dissolution device 18 and removes metal components from this ozone water.

[0042] In the first embodiment, as the ion exchange device 20, as shown in FIG. 2, a cation exchange type ion exchange device including ion exchange fibers 32 is used. Specifically, for example, a non-woven sheet-like base material 34 is formed of polyester fibers, cellulose fibers, high-density polyethylene fibers, etc. A monomer is added to the surface of this base material 34, so that a large number of hydrocarbon chains 36 are provided. And functional groups 38 as metal ion adsorbents are provided on these large number of hydrocarbon chains 36 by graft polymerization or the like. As the functional group 38, for example, a sulfo group, an iminodiacetic acid group, etc. can be used.

[0043] Since the actual ion exchange fiber 32 is, for example, sheet-shaped, a plurality of ion exchange fibers 32 are stacked and housed in a container such as a cartridge for use. As an example, there is a structure in which a single sheet-shaped ion exchange fiber 32 is wound in a spiral shape in a certain direction to form a substantially cylindrical shape with multiple layers as a whole, and this is housed in a cartridge or the like. In this case, by allowing the ozone water to flow from the center of the spiral of the ion exchange fiber 32 to the outer peripheral side, a wide area where the ozone water contacts the ion exchange fiber 32 can be ensured. Alternatively, one or a plurality of stacked ion exchange fibers may be housed in a capsule, and the ozone water may be passed through in the thickness direction of the ion exchange fiber 32.

[0044] In the ion exchange device 20 having such a structure, when ozone water is passed through, the metal components (metal ions) contained in the ozone water are captured by the functional groups 38, and the metal components are removed from the ozone water.

[0045] The ozone water from which the metal components have been removed by the ion exchange device 20 is sent to the use point 22. Note that the ozone water that has not been used at the use point 22 may be returned to the upstream side of the deaerator 16 or the upstream side of the ozone dissolution device 18 for reuse.

[0046] Next, the operation of the ozone water production system 12 and the ozone water production method of the present embodiment will be described.

[0047] In the ultrapure water production device 14, ultrapure water is produced from raw water. The produced ultrapure water is subjected to a deaeration process by the deaerator 16. By the deaeration process, gases such as dissolved oxygen in the ultrapure water are removed.

[0048] Then, ozone is dissolved in the ultrapure water degassed by the degassing device by the ozone dissolving device 18 to obtain ozone water. In the technology disclosed in the present application, examples of the uses of ozone water include semiconductor manufacturing processes such as surface cleaning and surface treatment of a silicon wafer whose surface is mirror-finished. The ozone water obtained by the ozone dissolving device 18 satisfies the concentration of ozone required for use in these semiconductor manufacturing processes.

[0049] By the way, when assuming the above-described semiconductor manufacturing process as the use of ozone water, conventional ozone water may be unsuitable for use due to the metal components contained therein. For example, in a configuration where silicon wafers are bonded together, it is required to extremely reduce impurities on the bonding surface. Also, in a configuration where the surface of a silicon wafer is mirror-polished or washed after polishing, it is required not to cause minute scratches or adhesion of impurities on the surface. Further, even in a configuration where an epitaxial film is formed on the surface of a silicon wafer, for example, when washing the surface to make it hydrophilic, it is required not to adhere impurities to the surface. A more specific target is a process for manufacturing a silicon wafer having a wiring line width of 22 nm or less, particularly 10 nm or less, and further 5 nm or less, when forming a wiring on the surface of a silicon wafer.

[0050] Therefore, in the above-described semiconductor manufacturing process, ozone water with metal components reduced to the limit is required. However, the concentration of metal components contained in conventional ozone water may be high for these uses, and there has been no manufacturing method and manufacturing system for ozone water with the concentration of metal components sufficiently lowered.

[0051] In contrast, in the technology disclosed in the present application, for the ozonated water obtained by dissolving ozone with the ozone dissolution device 18, the metal components are removed by the ion exchange treatment in the ion exchange device 20. As an index (degree) for the removal of these metal components, for example, the iron concentration in the ozonated water is removed until it becomes 0.01 μg / L or less. In the ozonated water in which the iron concentration has been removed to this extent, metal components other than iron have also been removed, and when used in the above semiconductor manufacturing process, the ozonated water has had the metal components sufficiently removed.

[0052] That is, in the technology disclosed in the present application, it is possible to produce ozonated water in which the metal components have been sufficiently removed to such an extent that it can be used in a semiconductor manufacturing process that requires ozonated water with extremely few metal components.

[0053] Next, a second embodiment will be described. In the second embodiment, the configuration of the ion exchange device is different from that of the first embodiment, but the other configurations can be the same. Hereinafter, the overall configuration of the ozonated water production system of the second embodiment will be omitted from illustration, and the ion exchange device 40 will be described.

[0054] As shown in FIG. 3, in the ion exchange device 40 in the ozonated water production system of the second embodiment, ion exchange resin 42 is used instead of the ion exchange fiber 32 (see FIG. 2) of the first embodiment.

[0055] The ion exchange resin 42 has a particulate resin substrate 44 having a large number of pores 46. And functional groups (refer to the functional groups 38 of the first embodiment) exist inside the pores 46. And a plurality of ion exchange resins 42 (particulate resin substrates 44) are accommodated in a container having a certain shape, and the ozonated water is passed through this container.

[0056] Also in the ozone water production system of the second embodiment, since it has the ion exchange device 40 equipped with such an ion exchange resin 42, the ion exchange treatment is performed on the ozone water obtained by dissolving ozone by the ozone dissolution device 18 in the ion exchange device 20. And thereby, it is possible to produce ozone water in which metal components are sufficiently removed when used in the above semiconductor manufacturing process.

[0057] In the second embodiment, the ion exchange resin 42 used as the ion exchange device 40 has a particulate resin base material 44. Since the shape of the resin base material 44 is stable and the functional groups are provided in the pores 46, it is easy to maintain the state in which the functional groups are held.

[0058] On the other hand, in the first embodiment, functional groups 38 are provided on a large number of hydrocarbon chains 36, and the area for capturing metal ions in ozone water is wider than that in the second embodiment. Therefore, the removal rate of removing metal components from ozone water (the amount of metal ions removed per unit time) is also larger in the first embodiment than in the second embodiment.

Example

[0059] Next, the technology disclosed in the present application will be described in more detail with reference to examples and comparative examples. Note that the technology disclosed in the present application is not limited to the configurations and ranges described in the following Examples 1 and 2.

[0060] In Example 1, ozone water was produced using the ozone water production system of the first embodiment, and in Example 2, ozone water was produced using the ozone water production system of the second embodiment. Further, without using the ozone water production system according to the technology disclosed in the present application, that is, ozone water in which metal components are not removed by the ion exchange devices 20 and 40 was used as a comparative example. In addition to these examples and comparative examples, numerical values of iron concentration, titanium concentration, and TOC (Total Organic Carbon) concentration were measured for the ultrapure water obtained by the ultrapure water production device 14 (see FIG. 1). The measurement results are shown in Table 1.

[0061]

Table 1

[0062] The ion exchange devices used in Example 1 and Example 2 are as follows.

[0063] Example 1: An ion exchange device configured to use one 10-inch cartridge of the Glan Craft KG-S type (manufactured by Kurashiki Fiber Processing Co., Ltd.). Example 2: Cation exchange resin (Duolite CGP (manufactured by Rohm and Haas)) Space velocity: 30 (1 / h)

[0064] Note that the above space velocity is the value obtained by dividing the flow rate passing through the target (in this case, the ion exchange resin 42) per unit time by the volume of the ion exchange resin 42, and indicates how many times the ozone water of the ion exchange resin 42 passes through the ion exchange resin 42 per unit time. In each of the examples and comparative examples, the flow rate was 20 L / min.

[0065] As shown in Table 1, in the comparative example, the iron and titanium contents are increased compared to the ultrapure water. This is presumably because elution of iron and titanium occurs in any of the processes after the ultrapure water is produced by the ultrapure water production apparatus 14. In Example 1 and Example 2, for the ozone water in which the iron concentration is increased more than 0.01 μg / L in this way, the metal components are removed by the ion exchange device 20 or the ion exchange device 40 until the iron concentration becomes 0.01 μg / L or less.

[0066] As a result, it can be seen that in the ozone water of Example 1, the concentrations of iron and titanium are significantly reduced compared to the ozone water of the comparative example, and the metal components can be sufficiently removed.

[0067] In addition, in the ozone water of Example 1, the TOC value slightly increases with respect to ultrapure water. This is presumably because a small amount of organic substances are generated by decomposition in the ion exchange device 20. However, the amount of increase in TOC in the ozone water of Example 1 is such that it has no impact on the use of ozone water in the technology disclosed in the present application, and substantially, the ozone water of Example 1 is equivalent to ultrapure water.

[0068] Also in the ozone water of Example 2, compared with the ozone water of the comparative example, the concentrations of iron and titanium are significantly decreased, indicating that the metal components can be sufficiently removed. However, in the ozone water of Example 2, the concentrations of iron and titanium are higher compared with the ozone water of Example 1. This is presumably due to the fact that, compared with the ion exchange fiber 32 used in Example 1, the ion exchange resin 42 used in Example 2 has a smaller surface area in contact with the ion water and a slower ion exchange rate. Also, in the ozone water of Example 2, the TOC value is larger compared with the ozone water of Example 1. This is presumably because, compared with the ion exchange fiber 32, the ion exchange resin 42 is more likely to generate carbon components by being decomposed by ozone.

Explanation of Reference Numerals

[0069] 12 Ozone water production system 14 Ultrapure water production device 16 Degassing device 18 Ozone dissolution device 20 Ion exchange device 22 Use point 32 Ion exchange fiber 34 Base material 36 Hydrocarbon chain 38 Functional group 40 Ion exchange device 42 Ion exchange resin 44 Resin base material 46 Pore

Claims

1. Manufacturing ozone water by dissolving ozone in ultrapure water for semiconductor manufacturing processes, removing metal components from the ozone water by ion exchange treatment, Ozone water manufacturing method.

2. The ozone water manufacturing method according to Claim 1, wherein in the ion exchange treatment, the iron concentration of the ozone water is set to 0.01 μg / L or less.

3. The ozone water manufacturing method according to Claim 1 or Claim 2, wherein ion exchange fibers are used in the ion exchange treatment.

4. An ultrapure water manufacturing apparatus for manufacturing ultrapure water for semiconductor manufacturing processes, an ozone dissolution apparatus for obtaining ozone water by dissolving ozone in the ultrapure water manufactured by the ultrapure water manufacturing apparatus, an ion exchange apparatus for removing metal components from the ozone water by ion exchange treatment, An ozone water manufacturing system having the above.

5. The ozone water manufacturing system according to Claim 4, wherein in the ion exchange apparatus, the metal components are removed until the iron concentration of the ozone water becomes 0.01 μg / L or less.

6. The ozone water manufacturing system according to Claim 4, wherein the ion exchange apparatus includes ion exchange fibers.

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