JP5975527B2 - Method for cleaning photomask-related substrate and method for manufacturing photomask-related substrate - Google Patents

Description

  The present invention relates to a method for cleaning a photomask-related substrate typified by a transparent substrate such as quartz glass, which is used for fine processing of a semiconductor integrated circuit, a CCD (collection coupling element), an LCD (liquid crystal display element), a magnetic head, etc. And a method of manufacturing a photomask-related substrate including the cleaning method as a cleaning step.

  Semiconductor integrated circuits used for various applications are designed to be finer in order to improve the degree of integration and reduce power consumption. Along with this, in the lithography technology using a photomask for forming a circuit, in order to obtain a finer image, light having a shorter wavelength is used as an exposure light source. In the practical processing step, the exposure light source is shifted from KrF excimer laser light (248 nm) to ArF excimer laser light (193 nm).

  Photomasks used in lithography technology include binary masks that have a light-blocking part that blocks exposure light almost completely, and the light phase is inverted with respect to the light-transmitting part while attenuating the light, resulting in light and darkness due to diffraction of the exposure light. A halftone phase shift mask or the like that prevents a decrease in contrast is put into practical use. These are made by forming a resist pattern on a photomask blank in which a thin film made of a chromium compound or a metal silicide compound is formed on a transparent substrate such as quartz glass, and etching the thin film using this pattern as an etching mask. The UV irradiation process is performed in the manufacturing process, particularly in the cleaning process.

  It is disclosed in Patent Document 1 that wettability can be improved by removing organic substances on the main surface and the end surface of the substrate by performing UV irradiation before wet cleaning of the photomask-related substrate, thereby facilitating wet cleaning.

Japanese Patent Laid-Open No. 2005-221929

However, in the current state-of-the-art practical processing process, an ArF excimer laser beam having a higher energy than the KrF excimer laser beam is used as an exposure light source. As a result, mask damage that has not been seen with the use of the KrF excimer laser beam Has been found to occur in photomasks. One of the mask damages is the generation of foreign growth defects on the photomask when the photomask is continuously used. This growth defect is called haze, and examples thereof include growth of ammonium sulfate crystals on the mask pattern surface irradiated with high-energy laser light.
In addition, in order to obtain a sufficient effect when UV irradiation is performed in the UV irradiation processing of a photomask-related substrate typified by a transparent substrate such as quartz glass, it is necessary to secure a sufficient concentration of generated ozone.

  The present invention has been made in view of the above problems, and an object of the present invention is to reduce substances that cause haze on the surface of a photomask-related substrate while maintaining the cleaning processing ability by UV irradiation.

In order to solve the above problems, the present invention provides:
A photomask-related substrate cleaning method including a UV irradiation step of irradiating a photomask-related substrate with UV, wherein the UV irradiation step is performed in an atmosphere containing oxygen having an oxygen concentration of 5% to 15%. A method for cleaning a substrate is provided.

With such a photomask-related substrate cleaning method, NH ₄ ⁺ , SO ₄ ²⁻ , NO ₂ ⁻ , which cause haze on the photomask-related substrate surface while maintaining the cleaning processing capability by UV irradiation. The amount of ions such as NO ₃ ⁻ can be reduced.

  At this time, it is preferable to use UV having a wavelength of 200 nm or less.

  With UV having such a wavelength, ozone can be efficiently generated during the UV irradiation process.

  The photomask-related substrate is preferably made of quartz glass.

  As described above, the present invention can effectively clean a photomask-related substrate using quartz glass.

  The photomask-related substrate is preferably a photomask-related substrate having a chromium-containing film on the surface.

  Thus, in the present invention, a photomask-related substrate having a film containing chromium on the surface can be cleaned.

  Furthermore, it is preferable to include a step of performing a wet cleaning process after the UV irradiation step.

  By performing the wet cleaning process in this way, the amount of ions that cause haze on the surface of the photomask-related substrate can be further reduced.

  At this time, it is preferable to perform the wet cleaning process using hydrogen water.

  With such a wet cleaning process, the amount of ions that cause haze on the surface of the photomask-related substrate can be further reduced.

  Furthermore, the present invention provides a photomask-related substrate manufacturing method including a cleaning process using the photomask-related substrate cleaning method.

With such a manufacturing method, the amount of ions such as NH ₄ ⁺ , SO ₄ ²⁻ , NO ₂ ⁻ , NO ₃ ^−, etc., which cause haze on the substrate surface is reduced, so that it was continuously used as a photomask It is possible to manufacture a photomask-related substrate that hardly causes haze.

As described above, with the photomask-related substrate cleaning method of the present invention, NH ₄ ⁺ , SO ₄ ^{2 that} causes haze on the photomask-related substrate surface while maintaining the cleaning processing capability by UV irradiation is maintained. ⁻ , NO ₂ ⁻ , NO ₃ ^{− and the} like can be reduced. Moreover, if it is a manufacturing method of the photomask related board | substrate which includes such a washing | cleaning method as a washing | cleaning process, a photomask related board | substrate which does not generate | occur | produce a haze easily when it uses continuously as a photomask can be manufactured.

It is the schematic which shows an example of the washing | cleaning apparatus which can be used by this invention. It is the schematic which shows an example of the UV irradiation unit in the washing | cleaning apparatus which can be used by this invention. It is the schematic which shows another example of the UV irradiation unit in the washing | cleaning apparatus which can be used by this invention. It is a graph which shows the relationship between the ozone concentration in atmosphere in the Example of this invention, and oxygen concentration. _NH ⁴ + photomask blank surface in the embodiment of the present ^{_{invention, SO 4 2-, NO 2 -}} , NO 3 - and is a graph showing the relationship between oxygen concentration.

In the cleaning process of the photomask-related substrate, UV irradiation is used in order to improve wettability such as decomposition of organic substances on the substrate surface and modification of hydrophilicity. This obtains the above-described cleaning ability by generating ozone gas from oxygen gas in the atmosphere by UV irradiation. Moreover, in order to produce | generate high concentration ozone gas, the one where an oxygen concentration is low is desirable.
However, if the oxygen concentration is reduced too much, the amount of ions that cause haze such as SO ₄ ²⁻ , NO ₂ ⁻ , and NO ₃ ⁻ increases due to the action of the generated ozone.

Therefore, the present inventor has determined the amount of ions such as NH ₄ ⁺ , SO ₄ ²⁻ , NO ₂ ⁻ , NO ₃ ^{− and the} like that cause haze on the substrate while maintaining an ozone concentration having a cleaning ability for organic substance decomposition. As a result of examining the UV irradiation conditions to reduce, especially the oxygen supply conditions, by adjusting the oxygen concentration in the atmosphere of the UV irradiation process to a certain range, cleaning treatment such as organic substance decomposition and wettability improvement of the substrate surface by UV irradiation The present invention was completed by finding that the amount of ions such as NH ₄ ⁺ , SO ₄ ²⁻ , NO ₂ ⁻ , NO ₃ ^{− and the} like causing haze on the substrate surface can be reduced while maintaining the capability.

That is, the present invention
A photomask-related substrate cleaning method including a UV irradiation step of irradiating a photomask-related substrate with UV, wherein the UV irradiation step is performed in an atmosphere containing oxygen having an oxygen concentration of 5% to 15%. A method for cleaning a substrate.
Hereinafter, the present invention will be described in more detail.

The photomask-related substrate cleaning method of the present invention is characterized by having a UV irradiation step performed in an atmosphere containing oxygen having an oxygen concentration of 5% or more and less than 15%. If the oxygen concentration in the atmosphere is less than 5% in the UV irradiation step, the amount of ions such as SO ₄ ²⁻ , NO ₂ ⁻ , NO ₃ ⁻ increases, and haze is generated on the substrate surface. On the other hand, when the oxygen concentration is higher than 15%, it is not possible to obtain an ozone concentration sufficient for organic substance decomposition and wettability improvement on the substrate surface.

In addition, by improving wettability in the UV irradiation process as described above, not only the removal of foreign substances such as organic matter after decomposition is facilitated in the wet cleaning process described later, which can be performed as a subsequent process. Further, drying unevenness can be reduced in the drying process of wet cleaning, and surface residual ions such as NH ₄ ⁺ , SO ₄ ²⁻ , NO ₂ ⁻ , NO ₃ ^{− and the} like that cause haze can be further reduced.

  The UV irradiation step can also be performed before applying a resist for forming a photomask circuit. By performing it before applying the resist, the wettability of the substrate surface can be improved and the amount of ions can be reduced. In particular, it is effective in deteriorating the shape such as pattern tailing and undercut after development of chemically amplified resist. The development performance can be stabilized.

  The wavelength of the UV light source used in the UV irradiation step is not particularly limited as long as it has sufficient energy to activate oxygen, but it is preferable to use light having a wavelength of 200 nm or less. Is 175 nm or less, particularly preferably 172 nm. By setting the wavelength of the UV irradiation light to 200 nm or less, the efficiency of light absorption by oxygen molecules in the irradiation atmosphere is rapidly improved. As a result, ozone can be efficiently generated to increase the ozone concentration in the atmosphere. it can. Further, relatively small organic foreign matters can be absorbed and dissociated and decomposed by UV, and then react with ozone to be removed as volatile reaction products.

  Examples of the UV lamp used at this time include a low-pressure mercury lamp and an excimer UV lamp. An excimer UV lamp is preferable.

  The excimer UV lamp is a lamp in which xenon gas is sealed in a quartz glass tube, and the xenon gas is excited and emitted with high-frequency power, and can emit UV having a wavelength of 175 nm or less. When this UV is irradiated to oxygen gas, it is said that active oxygen is directly generated. At the same time, high-concentration ozone is generated near the irradiation window, and active oxygen is generated via the ozone. These two reactions can generate more active oxygen than low-pressure mercury lamps, and the active oxygen and the energy of the UV itself can decompose organic substances on the substrate surface, improve wettability, especially improve hydrophilicity, etc. it can.

A photomask-related substrate used in the present invention includes a photomask substrate, a photomask blank obtained by forming one or more inorganic films on the photomask substrate, a photomask formed by processing the photomask blank, and It includes a photomask blank manufacturing intermediate in the middle of manufacturing a photomask blank formed by forming a plurality of inorganic films, and includes a photomask manufacturing intermediate in the middle of processing with the photomask blank.
Specific examples of the photomask substrate include a substrate (transparent substrate) having translucency with respect to exposure light such as quartz glass and calcium fluoride.
Photomask-related substrates that can be effectively cleaned using the cleaning method of the present application are quartz glass, a photomask blank using quartz glass, a photomask thereof, a photomask blank manufacturing intermediate, and a photomask thereof. Production intermediate.

  As such a photomask-related substrate, there is a photomask blank having a film containing chromium on the surface or a photomask blank manufacturing intermediate. As the film containing chromium, a film containing at least one of oxygen, nitrogen and carbon in metal chromium or metal chromium, that is, metal chromium, chromium oxide, chromium nitride, chromium carbide, chromium oxynitride, chromium oxide A film containing carbide, chromium nitride carbide, or chromium oxynitride carbide can be given.

  In addition, as a photomask-related substrate, a pattern is typically formed using the electron beam resist on the above-mentioned photomask blank, and the pattern is transferred by dry etching or wet etching using the resist pattern as an etching mask, or the photomask Mention may be made of production intermediates.

  As a photomask obtained from the above-mentioned photomask-related substrate, any binary mask, halftone phase shift mask, Levenson mask, or the like can be used as long as it has a pattern made of the above-described film material.

Moreover, in this invention, the process of performing a wet cleaning process after the said UV irradiation process can be included. The wet cleaning method is not particularly limited as long as it is a conventionally used method. However, the amount of ions such as SO ₄ ^{2− on} the surface of the object to be cleaned is preferably suppressed to a low level, and SO ₄ ^{2 -} so as not to source, production intermediates are preferably cleaned as much as possible in a state that is not contaminated with sulfate ions. In order to reduce the residual amount of acids derived from acids and alkali components such as sulfuric acid on the surface, use megasonic cleaning or high-pressure nozzles using functional water such as hydrogen water instead of acid solutions such as sulfuric acid. It is preferable to remove foreign substances such as organic substances decomposed in the UV irradiation step by performing cleaning.

The photomask-related substrate cleaned by such a cleaning method removes foreign matters such as organic substances on the surface of the substrate by UV irradiation, and also includes NH ₄ ⁺ , SO ₄ ²⁻ , NO ₂ ⁻ , NO ₃ ^{− and the} like. The amount of ions is reduced.

  As an apparatus used in a method for manufacturing a photomask-related substrate including the cleaning method as a cleaning step, for example, a UV irradiation unit that performs a UV irradiation step of irradiating UV to the photomask-related substrate P as shown in FIG. 3, a cleaning apparatus 1 having a wet cleaning unit 4 for performing a wet cleaning process for cleaning the photomask-related substrate P by a wet process after the UV irradiation process, and a transport means 5 for transporting the substrate. . Further, a pre-processing unit 2 that performs a pre-processing step for removing foreign matters on the surface of the photomask-related substrate P in advance may be provided before the UV irradiation step.

  The pretreatment unit 2 can be appropriately selected according to a pretreatment method, such as a wet treatment unit capable of treatment using a liquid or an air blow unit capable of treatment using a gas.

  The UV irradiation unit 3 has lamps arranged in a vertical direction in a lamp house provided perpendicular to the installation floor, and translates the photomask-related substrate P, which is an object to be cleaned, in the vertical direction relative to the lamp. It is preferable to have a mechanism (substrate movement mechanism).

  By irradiating the photomask-related substrate P with UV using such an apparatus 1, the cleanliness and uniformity of the surface to be cleaned can be improved. In addition, the UV irradiation unit 3 can oxidize and decompose foreign substances and then perform treatment with the final chemical solution. However, the UV irradiation unit 3 used here irradiates UV light only from one side of the photomask-related substrate. However, UV light may be irradiated from both sides. For example, in the vertical type in which the UV irradiation units 30a and 30b are provided with the lamp house 32 and the UV lamp 33 on the left and right of the UV irradiation chamber 31 shown in FIG. It is desirable to use a type in which the treated and decomposed foreign matter naturally drops and does not remain on the substrate surface.

  In such a UV irradiation unit 3, a mixed gas of air and an inert gas containing a certain amount of oxygen gas is supplied from a plurality of gas supply portions 35 a and 35 b provided on the surface facing the substrate P in the UV irradiation chamber 31 at a uniform interval. Is supplied to the substrate P transferred into the UV irradiation chamber 31 while adjusting the oxygen concentration, and is discharged from the gas exhaust unit 36 through the gas exhaust path portions 38a and 38b by the exhaust devices 37a and 37b. Is preferred. Such a configuration is preferable because the cleanliness of the surface after cleaning of the photomask-related substrate P can be easily made uniform.

  In addition, as shown in FIG. 3, such a UV irradiation unit is provided with rotating shafts 39a and 39b in the vicinity of the lower portion of the UV irradiation chamber, and the first UV irradiation unit 30a side and the first shaft around these rotating shafts. By rotating the second UV irradiation unit 30b side, the inside of the UV irradiation chamber 31 can be opened to the left and right, and maintenance such as replacement of the UV lamp can be facilitated.

  As the wet cleaning unit 4 in the cleaning apparatus 1, a unit used for conventional wet cleaning can be adopted.

  The transport means 5 for transporting the substrate P is not particularly limited as long as it can transport the substrate in the order of the pretreatment unit 2, the UV irradiation unit 3, and the wet cleaning unit 4. For example, as described above, when the UV irradiation unit 3 is of a vertical type and a mechanism for moving the UV irradiation unit 3 in the vertical direction is provided, the transport unit 5 may be integrated with the substrate moving mechanism.

In the present invention, the cleaning process of the photomask-related substrate can be performed using the cleaning apparatus exemplified above as follows.
Hereinafter, a photomask-related substrate manufacturing method including the cleaning method of the present invention as a cleaning step will be described with reference to the cleaning apparatus 1 shown in FIG. 1 and the UV irradiation unit 3 shown in FIG.

In the cleaning process of the method for manufacturing a photomask-related substrate of the present invention, it is preferable that the pretreatment unit 2 first performs pretreatment.
The pretreatment process is not particularly limited as long as it is a process for removing foreign substances made of organic matter, such as a wet process using a liquid or a process for removing foreign substances by gas blowing using a gas. When a wet process using a liquid such as shower cleaning is used, if the photomask-related substrate shows strong water repellency, it will repel on the surface of the photomask-related substrate, and uneven drying tends to occur. A dry process that is not used is preferred.

Among these, as a dry process, it is preferable to carry out by gas blow using gas, and it is particularly preferable to carry out blow by an inert gas using air or N ₂ or the like. If the photomask-related substrate, which is an object to be cleaned, is rotated or swung back and forth relative to the blow when performing the gas blow with the gas, the blow can be performed with good uniformity. At this time, the surface of the photomask-related substrate can be further neutralized by, for example, spraying dry nitrogen at a pressure of 0.3 MPa with a clean air gun with a built-in filter of 0.01 μm, for example, thereby improving the foreign matter removing ability. .

  At this time, in order to supply clean gas, it is preferable to blow through a filter, and in particular, through a filter of 0.01 μm or less and a pressure of 0.05 to 0.7 MPa, 10 to 120 L / min. The flow rate may be

  Furthermore, it is preferable to remove acid gas, alkaline gas, and organic gas from the gas before blowing, and a filter can be used in such a case. As the filter, it is preferable to use a filter for removing anions and cations and activated carbon as a filter.

  In addition, as a pretreatment process, for example, an ultrasonic dry cleaner may be used. When an ultrasonic dry cleaner is used, there are few problems of exhaust and reattachment of removed particles can be reduced.

Next, the UV irradiation unit 3 performs a UV irradiation process. In this step, the atmosphere contains oxygen having an oxygen concentration of 5% to 15%.
By irradiating with UV in this way, organic substances on the surface are removed, and the surface of the object to be cleaned is improved in wettability and becomes hydrophilic.

  The total amount of gas supplied from the gas supply units 35a and 35b is preferably 10 to 150 (L / min.). If gas supply is performed with such a total introduction amount as such, there is no fear that the ozone-containing gas generated in the UV irradiation chamber 31 will leak from the substrate introduction portion (opening portion), and there is no fear of disturbing the air flow inside the apparatus. preferable. The gas is not particularly limited as long as it has a predetermined oxygen concentration, and a gas obtained by mixing nitrogen with oxygen or a mixed gas of air and nitrogen may be used as the inert gas.

  Further, the discharge amount of the gas discharged from the gas discharge portion 36 through the gas exhaust path portions 38a and 38b is proportional to the total gas introduction amount described above. The ratio is preferably 3.0 times, more preferably 1.5 to 2.0 times. With such a discharge amount, even when the substrate transport mechanism enters the apparatus through the openings in the vicinity of the exhaust devices 37a and 37b, the external atmosphere drawn from the openings enters the device. There is no turbulence of the airflow in the apparatus due to the approach.

The amount of UV irradiation on the surface of the substrate P is preferably 10 mJ / cm ² or more per unit area. The amount of ozone generated when UV irradiation is performed is proportional to the amount of UV irradiation, and if the irradiation amount is high, the cleaning effect can be improved. However, if it is 10 mJ / cm ² or more, UV ozone cleaning is performed in the presence of the specified oxygen. When performing, an ozone concentration for ensuring a sufficient cleaning ability is obtained, and sufficient ozone can be spread over the surface of the substrate P. Moreover, as an upper limit, it is preferable to set it as the irradiation amount of 41.5 mJ / cm <2> or less per unit area so that an ultraviolet irradiation amount may not be raised too much.

It is preferable that wet cleaning is performed in the wet cleaning unit 4 after the UV irradiation process.
The wet cleaning method is as described above. It is preferable that the amount of ions including SO ₄ ²⁻ on the surface of the photomask-related substrate P is suppressed to be low, and in particular, the production intermediate should be SO ₄ ^{2− as} much as possible so as not to be a source of SO ₄ ²⁻ . It is preferable to wash in a non-contaminated state. In order to reduce the residual amount of acids derived from acids and alkali components such as sulfuric acid on the surface, use megasonic cleaning or high-pressure nozzles using functional water such as hydrogen water instead of acid solutions such as sulfuric acid. It is preferable to remove the foreign matter decomposed in the UV irradiation step by performing cleaning.

  If it is a manufacturing method of a photomask related substrate including such a cleaning process, foreign matter such as organic matter on the substrate surface is removed by UV irradiation, and the amount of ions is reduced. It is possible to obtain a good photomask that is unlikely to cause mask damage such as the above and a production intermediate thereof.

  Photomask-related substrates typified by a transparent substrate such as quartz glass obtained by the above-described photomask-related substrate manufacturing method are semiconductor integrated circuits, CCDs (collection coupling elements), LCDs (liquid crystal display elements), magnetic heads, etc. As what is used for a fine process, it can use suitably.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not limited by these description.

(Examples and comparative examples)
A photomask blank made of quartz glass, in which a square of 152 cm (6 inches) on a side and a substrate of about 6 mm (0.25 inches) in thickness, a film of chromium, oxygen, and nitrogen having a thickness of 70 nm is formed. Prepared and changed the oxygen concentration by adjusting the flow rate of air and nitrogen gas at a flow rate of 10 L / min in a mixed gas of nitrogen and oxygen, and UV at 18 mW / cm ² per unit area using a UV lamp with a wavelength of 172 nm Was irradiated for 3 minutes. At this time, the ozone concentration in the atmosphere was measured using an ozone concentration meter EG2001B manufactured by Sugawara Jitsugyo Co., Ltd. The result is shown in FIG.

Thereafter, the following processing was performed on the photomask blank.
1. Hydrogen water + MS (megasonic): 180 sec
2. DIW (deaerated water, dissolved oxygen 10% or less): 60 sec
3. Spin drying: 1500rpm / 30sec

After the above treatment, the amounts of NO ₂ ⁻ , NO ₃ ⁻ , SO ₄ ²⁻ and NH ₄ ^{+ on} the Cr surface were measured by ion chromatography. Specific conditions are as follows.
100 ml of ultrapure water was put into a quartz cell that had been cleaned, and kept at 80 ° C. while being heated by a heater. The sample to be evaluated was immersed in ultrapure water in this state and taken out after 120 minutes of immersion. And the amount of each ion was measured with the ion chromatograph analyzer ICS-3000 made from DEONEX by making the ultrapure water after immersion into an extract. In addition, IonPac AS11-HC made by the same company was used for the anion measurement, and IonPac CS12A made by the same company was used for the cation measurement. The measured amount of ions was converted to a unit and expressed as the weight μg (μg / L) of each ion contained in 1 liter of the extract. The relationship between the measured value and the measured oxygen concentration during the UV irradiation process was summarized. The result is shown in FIG.

From this, the ozone concentration is sufficiently high by setting the oxygen concentration in the atmosphere to 5% or more and 15% or less in the UV irradiation step, and NO ₂ ⁻ , NO ₃ ⁻ , SO ₄ ²⁻ , and NH ₄ ⁺ on the substrate surface are sufficiently reduced. I knew it was possible.

From the above results, it is clear that the photomask-related substrate cleaning method of the present invention can reduce the amount of ions such as NH ₄ ⁺ , SO ₄ ²⁻ , NO ₂ ⁻ , and NO ₃ ^{− that} cause haze. Became.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

DESCRIPTION OF SYMBOLS 1 ... Cleaning apparatus, 2 ... Pre-processing unit, 3 ... UV irradiation unit,
4 ... wet cleaning unit, 5, 5a, 5b, 5c, 5d ... conveying means,
30a ... 1st UV irradiation unit, 30b ... 2nd UV irradiation unit,
31 ... UV irradiation chamber, 32 ... Lamp house, 33 ... UV lamp,
34 ... Substrate transport mechanism, 35a, 35b ... Gas supply unit, 36 ... Gas discharge unit,
37a, 37b ... exhaust device, 38a, 38b ... gas exhaust path,
39a, 39b ... rotating shaft, P ... photomask related substrate.

Claims (7)

A cleaning method for a photomask-related substrate including a UV irradiation step of irradiating a photomask-related substrate with UV, wherein the UV irradiation step has an oxygen concentration of 5% to 15% (however, excluding 5% to 10%) The method for cleaning a photomask-related substrate, which is performed in an atmosphere containing oxygen ) .   The method for cleaning a photomask-related substrate according to claim 1, wherein the UV has a wavelength of 200 nm or less.   The method for cleaning a photomask-related substrate according to claim 1, wherein the photomask-related substrate is made of quartz glass.   4. The photomask-related substrate according to claim 1, wherein a photomask-related substrate having a chromium-containing film on a surface of a quartz substrate is cleaned as the photomask-related substrate. Cleaning method.   The method for cleaning a photomask-related substrate according to any one of claims 1 to 4, further comprising a step of performing a wet cleaning process after the UV irradiation step.   The method for cleaning a photomask-related substrate according to claim 5, wherein the wet cleaning process is performed using hydrogen water. A method for manufacturing a photomask-related substrate, comprising: a cleaning step using the method for cleaning a photomask-related substrate according to any one of claims 1 to 6.

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