JP2023037218A - Ozone water producing method and ozone water producing system - Google Patents

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

The present application relates to an ozonated water production method and an ozonated water production system.

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

For example, in Patent Document 1, Si—H bonds are formed on the surface of a mirror-finished silicon wafer, and ozone or hydrogen peroxide solution is applied to the surface of the silicon wafer to form an oxide film of only one atomic layer. Examples are given.

Patent Document 2 describes a method of stopping the supply of the polishing liquid when the polishing of the wafer surface with the polishing liquid is nearing completion, and simultaneously supplying a rinse liquid to remove abrasive grains from the wafer surface. Ozone water is exemplified as an oxidizing agent contained in the rinse liquid.

Patent Document 3 describes that cleaning with a mixed solution of a small amount of hydrofluoric acid and ozone water is used as an example of cleaning to make the surface of a silicon wafer hydrophilic.

In general, ozone water is often used in the cleaning process of silicon wafers, and is often used in device formation processes on silicon wafers such as resist stripping. However, in such a device formation process, wiring, resist, etc. exist on the surface of the silicon wafer. In the cleaning process of a silicon wafer, for example, when these wirings, resists, etc. are stripped and removed, the stripping agent is mixed with the resist. Therefore, even if impurities exist in the ozone water used as the stripping agent, the impurities do not pose a problem.

JP-A-9-63910 JP-A-11-243072 JP 2005-244127 A

Ozonated water as described above is used in part of the semiconductor manufacturing process, such as resist removal and pattern formation on silicon wafers.

By the way, silicon wafers with mirror-finished surfaces are required to have an extremely small amount of impurities on the surface. Accordingly, it is required that the ozonized water contains extremely few impurities. Especially in the future, this trend is expected to become more pronounced as semiconductors to be manufactured are miniaturized. However, practically no ozonized water from which metal components have been sufficiently removed to the extent that it can be suitably used in the semiconductor manufacturing process for such silicon wafers or the like exists.

For example, Patent Document 1 describes that a silicon wafer is immersed in 8 ppm ozonized water for 5 seconds to form a natural oxide film on the surface. Not listed.

Patent Document 2 describes that the content of the oxidizing agent in the rinse solution is determined so that the oxidation-reduction potential of the rinse solution is 10 mV or more, but does not describe the concentration of the metal component in the ozone water. not

Patent document 3 also does not describe the concentration of metal components in ozone water.

Thus, there is no ozonized water from which metal components have been removed to such an extent that it can be used for cleaning or processing silicon wafers with mirror-finished surfaces, and ozonized water from which metal components have been sufficiently removed. There is also no manufacturing method and manufacturing system for

An object of the present application is to obtain an ozonized water production method and an ozonated water production system capable of producing ozonized water from which metal components are sufficiently removed.

In the method for producing ozonized water of the first aspect, ozonized water is produced by dissolving ozone in ultrapure water,
Metal components are removed from the ozone water by ion exchange treatment.

In this method for producing ozone water, ozone is dissolved in ultrapure water to produce ozone water. At this stage, ozone water in which a sufficient amount of ozone has been dissolved is obtained.

However, the ozonized water obtained in this manner may contain metal components such as iron and titanium in addition to ozone. Ionized water containing a large amount of metal components may be unsuitable for surface cleaning and surface treatment of mirror-finished silicon wafers.

In the method for producing ozonized water of the first aspect, metal components are removed from the obtained ozonized water by ion exchange treatment. This makes it possible to produce ozonized water in which an amount of ozone necessary for cleaning and treating the surface of a mirror-finished silicon wafer is dissolved and metal components are sufficiently removed.

The degree of removal of the metal component by the ion exchange treatment is sufficient as long as it can be used for surface cleaning and surface treatment of mirror-finished silicon wafers. In the treatment, the iron concentration of the ozone water is set to 0.01 μg/L or less. In other words, ozone water from which metal components have been removed to such an extent that the iron concentration is 0.01 μg/L or less is sufficient for surface cleaning and surface treatment of mirror-finished silicon wafers. can be used.

In the third embodiment, ion exchange fibers are used for the ion exchange treatment.

As a result, metal components can be efficiently removed from the ozonated water, for example, compared to a configuration using an ion exchange resin for ion exchange treatment.

The ozone water production system of the fourth aspect comprises an ultrapure water production device for producing ultrapure water, and an ozone dissolving device for obtaining ozone water by dissolving ozone in the ultrapure water produced by the ultrapure water production device. and an ion exchange device for removing metal components from the ozone water by ion exchange treatment.

In this ozonated water production system, ultrapure water is produced by an ultrapure water production device, and ozone is dissolved in the produced ultrapure water by an ozone dissolving device to produce ozonated water. At this stage, ozone water in which a sufficient amount of ozone has been dissolved is obtained.

However, the ozonized water obtained in this manner may contain metal components such as iron and titanium in addition to ozone. Ionized water containing a large amount of metal components may be unsuitable for surface cleaning and surface treatment of mirror-finished silicon wafers.

In the ozone water production system of the fourth aspect, metal components are removed by the ion exchange device from the ozone water obtained by the ozone dissolving device. This makes it possible to produce ozonized water in which an amount of ozone necessary for cleaning and treating the surface of a mirror-finished silicon wafer is dissolved and metal components are sufficiently removed.

The degree of removal of metal components by the ion exchange device may be sufficient so that it can be used for surface cleaning and surface treatment of mirror-finished silicon wafers. In the apparatus, the metal components are removed until the iron concentration of the ozone water becomes 0.01 μg/L or less. In other words, ozone water from which metal components have been removed to such an extent that the iron concentration is 0.01 μg/L or less is sufficient for surface cleaning and surface treatment of mirror-finished silicon wafers. can be used.

In a sixth embodiment, the ion exchange device comprises ion exchange fibers.

As a result, metal components can be efficiently removed from the ozone water, for example, compared to the case of using a configuration including an ion exchange resin as an ion exchange device.

In the present application, an ozonized water production method and an ozonated water production system capable of producing ozonized water from which metal components are sufficiently removed are obtained.

FIG. 1 is a configuration diagram showing the ozone water production system of the first embodiment. FIG. 2 is an explanatory diagram showing the internal configuration of the ion exchange device in the ozone water production system of the first embodiment. FIG. 3 is an explanatory diagram showing the internal configuration of an ion exchange device in the ozone water production system of the second embodiment.

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

The ozone water production system 12 of the first embodiment has an ultrapure water production device 14, a degassing device 16, an ozone dissolving device 18, an ion exchange device 20, and a use point 22, as shown in FIG. Then, ozonized water in which ozone is dissolved at a predetermined concentration can be obtained from the raw water. This ozonized water is used, for example, in a semiconductor manufacturing process for surface cleaning and surface treatment of a mirror-finished silicon wafer. Here, the term “mirror surface” means that the surface of the silicon wafer has an arithmetic mean roughness (Ra) of 4 nm or less 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 made by KLA Tencor
・Measurement mode: Roughness
・Measurement length: 200 μm
・Measurement speed: 5 μm/sec
・Measurement load: 1 mg
Arithmetic mean roughness (Ra) is a value obtained by integrating the absolute value of the difference between the reference line and the unevenness in the range of the measurement length on the surface of the object, taking the average height of the unevenness as a reference, and dividing it by the measured length. (Integrated value per unit length).

The ultrapure water production device 14 removes impurities from the supplied raw water to produce ultrapure water. Examples of raw water include industrial water, tap water, ground water, river water, and the like.

The ultrapure water production device 14 has, for example, a pretreatment device, a primary pure water device, a pure tank, a secondary pure water device, and the like.

The pretreatment device pretreats raw water used to produce ultrapure water. That is, pretreatment in which a part of impurities such as suspended solids and organic matter is removed by removing turbidity from the raw water supplied by using a coagulating sedimentation device, a sand filtration device, a membrane filtration device, a demineralization device, or the like. get water

In the primary pure water system, the pretreated water obtained by the pretreatment system is further subjected to various treatments such as adsorption, filtration, and ion exchange to remove impurities that could not be removed by the pretreatment system. get water

The primary pure water obtained by the primary pure water device is sent to the pure water tank and temporarily stored. In the secondary pure water system, the temporary pure water sent from the pure water tank is subjected to various treatments such as decomposition of organic matter by ultraviolet irradiation, sterilization, adsorption, filtration, ion exchange, etc., and is removed by the primary pure water system. The remaining impurities are further removed to produce ultrapure water.

The degassing device 16 is a device for removing gases such as dissolved oxygen from ultrapure water. For example, there is a configuration in which gas, particularly dissolved oxygen, in ultrapure water is removed by using a gas separation membrane that is impermeable to moisture but permeable to gas. A degassing device (membrane degassing device) having such a configuration may be included in, for example, a secondary pure water device. Moreover, even if the deaeration treatment by the deaeration device 16 is not performed, the amount of dissolved gas may be so low that it does not pose a problem when using ozone water. In such a case, the degassing device 16 may not perform the degassing process.

The ozone dissolving device 18 is a device for dissolving ozone in the ultrapure water deaerated by the deaerator 16 .

A specific method for dissolving ozone in ultrapure water is not particularly limited, and for example, a membrane dissolution method, a tank dissolution method, a non-circulation method, a circulation method, or the like can be used. In the membrane dissolving type ozone dissolving apparatus, a gas permeable membrane is used to diffuse and dissolve a gas to be dissolved (ozone gas in the case of the present application) in ultrapure water. In a tank dissolving type ozone dissolving apparatus, a tank containing ultrapure water and ozone is controlled to have a predetermined internal pressure to dissolve ozone in the ultrapure water. In this case, the ozone may be dissolved in the ultrapure water while the ultrapure water is sequentially transferred to a plurality of tanks with sequentially lowered internal pressures. As a result, ozonized water in which ozone is dissolved at a predetermined concentration in ultrapure water is obtained. The circulating system is a system in which the ozonized water that is not used at the point of use 22 out of the produced ozonized water is returned to any step in the ozonated water production process for reuse. On the other hand, the non-circulating method is a method in which the ozonized water that has not been used at the point of use 22 out of the produced ozonized water is not returned to any step in the ozonated water production process.

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 dissolving device 18 to remove metal components from the ozone water.

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

Since the actual ion-exchange fibers 32 are, for example, sheet-shaped, a plurality of ion-exchange fibers 32 are stacked and housed in a container such as a cartridge for use. One example is a structure in which a single sheet-like ion-exchange fiber 32 is spirally wound in a certain direction to form a plurality of layers of a generally cylindrical shape as a whole, which is housed in a cartridge or the like. In this case, by allowing the ozonated water to flow from the center of the spiral of the ion exchange fibers 32 to the outer peripheral side, it is possible to secure a wide area where the ozonated water contacts the ion exchange fibers 32 . Alternatively, one or a plurality of laminated ion-exchange fibers may be contained in a capsule, and ozone water may be passed through the ion-exchange fibers 32 in the thickness direction.

In the ion exchange device 20 having such a structure, when the 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. be.

The ozonized water from which metal components have been removed by the ion exchange device 20 is sent to the use point 22 . Incidentally, the ozonated water that has not been used at the point of use 22 may be returned to the upstream side of the degassing device 16 or the upstream side of the ozone dissolving device 18 for reuse.

Next, the operation of the ozonated water production system 12 of this embodiment and the ozonated water production method will be described.

The ultrapure water production device 14 produces ultrapure water from raw water. The ultrapure water is deaerated by the deaerator 16 . Gases such as dissolved oxygen in the ultrapure water are removed by the degassing treatment.

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, applications of ozone water include, for example, semiconductor manufacturing processes such as surface cleaning and surface treatment of silicon wafers whose surfaces have been mirror-finished. The ozone water obtained by the ozone dissolving device 18 satisfies the required ozone concentration for use in these semiconductor manufacturing processes.

By the way, when the semiconductor manufacturing process described above is assumed as an application of ozonated water, conventional ozonated water may be unsuitable for use due to the metal components contained therein. For example, in a configuration in which silicon wafers are bonded together, it is required to extremely reduce impurities on the bonding surface. In addition, even in a configuration in which the surface of a silicon wafer is mirror-polished or cleaned after polishing, it is required that the surface be free from microscopic scratches and adhesion of impurities. Furthermore, even in the configuration where an epitaxial film is formed on the surface of a silicon wafer, it is required that impurities do not adhere to the surface, for example, when cleaning the surface to make it hydrophilic. More specifically, in the case of forming wiring on the surface of a silicon wafer, the line width of the wiring to be formed is 22 nm or less, particularly 10 nm or less, and further a silicon wafer manufacturing process of 5 nm or less. be.

Therefore, in the above-described semiconductor manufacturing process, ozonized water with metal components reduced to the utmost limit is required. However, the concentration of metal components contained in conventional ozonated water is sometimes high for these uses, and there has been no method or system for producing ozonized water with a sufficiently low concentration of metal components.

On the other hand, in the technology disclosed in the present application, metal components are removed from ozone water obtained by dissolving ozone in the ozone dissolving device 18 by ion exchange treatment in the ion exchange device 20 . As an index (degree) of removal of the metal component, for example, removal is performed until the iron concentration of the ozone water becomes 0.01 μg/L or less. The ozonized water from which the iron concentration has been removed to this extent also has metal components other than iron removed, and is ozonized water from which the metal components have been sufficiently removed for use in the semiconductor manufacturing process described above.

That is, the technique disclosed in the present application can produce ozonized water from which metal components are sufficiently removed to the extent that it can be used in semiconductor manufacturing processes that require ozonated water with extremely low metal components.

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

As shown in FIG. 3, in the ion exchange device 40 in the ozone water production system of the second embodiment, an ion exchange resin 42 is used instead of the ion exchange fibers 32 (see FIG. 2) of the first embodiment.

The ion exchange resin 42 has a particulate resin base material 44 having numerous pores 46 . A functional group (see the functional group 38 of the first embodiment) is present inside the pores 46 . A plurality of ion-exchange resins 42 (particulate resin base material 44) are accommodated in a container having a fixed shape, and ozone water is passed through this container.

Since the ozone water production system of the second embodiment also has the ion exchange device 40 having such an ion exchange resin 42, the ozone water obtained by dissolving ozone in the ozone dissolving device 18 is , an ion exchange treatment is performed in the ion exchange device 20 . This makes it possible to produce ozonized water from which metal components have been sufficiently removed for use in the above-described semiconductor manufacturing process.

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 resin base material 44 has a stable shape and the functional groups are provided in the pores 46, it is easy to maintain the state in which the functional groups are held.

In contrast, in the first embodiment, many hydrocarbon chains 36 are provided with functional groups 38, and the area for trapping metal ions in ozone water is wider than in the second embodiment. Therefore, the removal speed (amount of metal ions removed per unit time) for removing metal components from ozone water is also greater in the first embodiment than in the second embodiment.

Next, the technology disclosed in the present application will be described in more detail with reference to examples and comparative examples. It should be noted that the technology disclosed in the present application is not limited to the configuration and scope described in the following Examples 1 and 2.

In Example 1, ozone water was produced using the ozone water production system of the first embodiment, and in Example 2, the ozone water production system of the second embodiment was used. In addition, ozonated water without using the ozonated water production system according to the technology disclosed in the present application, that is, without removal of metal components by the ion exchange devices 20 and 40 was used as a comparative example. In addition to these examples and comparative examples, the iron concentration, titanium concentration and TOC (Total Organic Carbon) concentration of the ultrapure water obtained by the ultrapure water production device 14 (see FIG. 1) were measured. I measured the numbers. Table 1 shows the measurement results.

The ion exchange apparatus used in Examples 1 and 2 is as follows.

Example 1: An ion exchange apparatus using one 10-inch cartridge of Grancraft KG-S type (manufactured by Kurashiki Textile Processing Co., Ltd.).
Example 2: Cation exchange resin (Duolite CGP (manufactured by Rohm and Haas)
Spatial velocity: 30 (1/h)

The above space velocity is a 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. It shows how many times as much ozonized water as 42 passes through the ion exchange resin 42 . In each example and comparative example, the flow rate was 20 L/min.

As shown in Table 1, in the comparative example, iron and titanium are increased more than ultrapure water. It is considered that this is because iron and titanium are eluted in any of the processes after ultrapure water is produced by the ultrapure water production apparatus 14 . In Examples 1 and 2, the ion exchange device 20 or the ion exchange device 40 reduces the iron concentration to 0 for the ozone water having the iron concentration higher than 0.01 μg/L. Metal components are removed until the concentration becomes 01 μg/L or less.

As a result, it can be seen that the ozonized water of Example 1 has a significantly lower concentration of iron and titanium than the ozonized water of the comparative example, and the metal components can be sufficiently removed.

It should be noted that the ozone water of Example 1 has a slightly higher TOC value than the ultrapure water. It is considered that this is because a small amount of organic matter was generated by decomposition in the ion exchange device 20 . However, the increase in TOC in the ozonated water of Example 1 does not affect the application of the ozonated water in the technology disclosed in the present application, and substantially the ozonated water of Example 1 is ultrapure water. is equivalent to

Also in the ozonized water of Example 2, the concentrations of iron and titanium are significantly lower than those of the ozonized water of the comparative example, indicating that the metal components can be sufficiently removed. However, the ozone water of Example 2 has higher concentrations of iron and titanium than the ozone water of Example 1. This is thought to be due to the fact that the ion exchange resin 42 used in Example 2 has a narrower surface area with which the ionized water contacts and the ion exchange rate is lower than that of the ion exchange fiber 32 used in Example 1. . Further, the ozone water of Example 2 has a larger TOC value than the ozone water of Example 1. This is probably because the ion-exchange resin 42 is more likely to be decomposed by ozone to produce a carbon component than the ion-exchange fiber 32 .

12 Ozone water production system 14 Ultrapure water production device 16 Degassing device 18 Ozone dissolving 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 Substrate 46 Pores

Claims (6)

ozonated water is produced by dissolving ozone in ultrapure water,
removing metal components from the ozonated water by ion exchange treatment;
A method for producing ozonated water. The method for producing ozonized water according to claim 1, wherein the iron concentration of the ozonized water is set to 0.01 µg/L or less in the ion exchange treatment. The method for producing ozone water according to claim 1 or 2, wherein ion exchange fibers are used for the ion exchange treatment. an ultrapure water production device for producing ultrapure water;
an ozone dissolving device for obtaining ozone water by dissolving ozone in the ultrapure water produced by the ultrapure water production device;
an ion exchange device for removing metal components from the ozonated water by ion exchange treatment;
ozonated water production system. The ozone water production system according to claim 4, wherein the ion exchange device removes the metal component until the iron concentration of the ozone water becomes 0.01 µg/L or less. The ozone water production system according to claim 4, wherein the ion exchange device comprises ion exchange fibers.

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