Method for cleaning a substrate for a raw mask, substrate for a raw mask and a raw mask encompassing the substrate

Abstract

A cleaning process for a substrate for a raw mask, comprising: a first cleaning process of irradiating a cleaning target substrate with a pretreatment light to produce a light-cleaned substrate; and a second cleaning process of applying a first cleaning solution and a post-treatment light to the light-cleaned substrate to produce a substrate for a crude mask; wherein the pre-treatment light is a light with a wavelength of 50 nm to 300 nm, and wherein the post-treatment light is a light with a wavelength of 50 nm to 450 nm, wherein the substrate for a crude mask comprises sulfuric acid ions in an amount of 0 ng / cm² to 0.1 ng / cm², nitric acid ions in an amount of 0 ng / cm² to 0.4 ng / cm², nitrous acid ions in an amount of 0 ng / cm² to 0.05 ng / cm² and ammonium ions in an amount of 0 ng / cm² to 1.5 ng / cm² as residual ions, measured by the method of ion chromatography.

Description

CROSS-REFERENCE TO RELATED REGISTRATIONS

[0001] This application claims priority over Korean patent application No. 10-2021-0110129, filed on August 20, 2021. 1. Technical field

[0002] The present disclosure relates to a purification process of a substrate for a raw mask, a substrate for a raw mask and a raw mask comprising the substrate. 2. Description of the state of the art

[0003] Due to the high integration of semiconductor devices and the like, miniaturization of semiconductor circuit structures is necessary. For this reason, the importance of lithography, a technique for developing a circuit structure on a wafer surface using a photomask, is further emphasized.

[0004] To develop a miniaturized circuit structure, it is necessary that the exposure light source used in an exposure process (photolithography) has a short wavelength. Recently, an ArF excimer laser (wavelength of 193 nm) or similar has been used as the exposure light source.

[0005] A raw mask comprises a transparent substrate and a thin film, such as a light-blocking film, formed on the transparent substrate. The transparent substrate can be produced by shaping a material with light transmission properties, a polishing process, a cleaning process, and the like.

[0006] When miniaturizing a circuit structure, it is necessary to more effectively prevent the creation of defects during the manufacturing process of the raw mask. Among the defects that can be introduced in the final raw mask, one can be caused by the transparent substrate. To develop a predetermined small circuit structure, it is necessary to meticulously control the properties, such as the flatness and surface roughness of the transparent substrate, and it is also necessary to significantly reduce defects, particles, and the like within the transparent substrate itself compared to the previous case. [Related prior art][Patent document] (Patent document 1) Korean patent application no. 10-0316374, and (Patent document 2) Korean patent application no. 10-0745065. SUMMARY

[0007] In a general aspect, a cleaning process of a substrate for a raw mask according to one embodiment comprises a first cleaning process of irradiating a cleaning target substrate with a pretreatment light to produce a light-cleaned substrate, and a second cleaning process of applying a first cleaning solution and a posttreatment light to the light-cleaned substrate to produce a substrate for a raw mask.

[0008] The pretreatment light is a light with a wavelength of 50 nm to 300 nm.

[0009] The post-treatment light is a light with a wavelength of 50 nm to 450 nm.

[0010] The intensity of the pretreatment light can be 25 mW / cm². 2 or more.

[0011] The target substrate for cleaning can be irradiated with pretreatment light by two or more light sources.

[0012] A UI value according to equation 1 below can be 20% or less. UI(%)=Imax−IminImax+Imin×100

[0013] In equation 1, I max the maximum value of the intensities of the pretreatment light applied by each light source, and I min is the minimum value of the intensities of the pretreatment light applied by each light source.

[0014] The first cleaning process can be carried out in an atmosphere of reduced pressure.

[0015] The atmosphere in which the cleaning target substrate is arranged can be applied by a discharge pressure of 0.01 kPa to 1 kPa.

[0016] The first cleaning solution may include SC-1 (Standard Clean-1) solution, ozonated water, ultra-pure water, hydrogen water, carbonated water, or a combination of two or more of the above.

[0017] The SC-1 solution is a solution that includes NH4OH, H2O2 and H2O.

[0018] The substrate purified with light can be one from which some or all of a compound that absorbs light with a wavelength of 100 to 190 nm has been removed.

[0019] The first purification solution may include a hydroxyl radical precursor.

[0020] The post-treatment light can form a hydroxyl radical by irradiation when the first cleaning solution is applied to the light-cleaned substrate.

[0021] The substrate for a crude mask can contain sulfuric acid ions in an amount of 0 ng / cm². 2 up to 0.1 ng / cm³ 2 Nitric acid ions in a quantity of 0 ng / cm³ 2 up to 0.4 ng / cm² 2 , nitrous acid ions in an amount of 0 ng / cm³ 2 up to 0.05 ng / cm² 2 and ammonium ions in an amount of 0 ng / cm³ 2 up to 1.5 ng / cm² 2as residual ions, measured by the method of ion chromatography.

[0022] The PRE value of the substrate for a raw mask can be 90% or more according to Equation 2 below. PRE(%)=Pb−PaPb×100

[0023] In equation 2, the P b -Value the number of particles, measured against the target substrate for cleaning, and the P a The value is the number of particles, measured on the substrate for a raw mask.

[0024] The substrate for a raw mask according to another embodiment is a quartz substrate with a flatness of 0.5 µm or less.

[0025] The substrate for a crude mask contains sulfuric acid ions in an amount of 0 ng / cm³. 2 up to 0.1 ng / cm³ 2 , Nitric acid ions in an amount of 0 ng / cm³ 2 up to 0.4 ng / cm² 2 , nitrous acid ions in an amount of 0 ng / cm³ 2 up to 0.05 ng / cm² 2and ammonium ions in an amount of 0 ng / cm³ 2 up to 1.5 ng / cm² 2 as residual ions, measured by the method of ion chromatography.

[0026] The substrate for a raw mask can contain chloride ions in an amount of 0 ng / cm². 2 up to 0.1 ng / cm³ 2 as residual ions, measured by the method of ion chromatography.

[0027] A raw mask according to another embodiment comprises the substrate for a raw mask. DETAILED DESCRIPTION

[0028] Exemplary embodiments of the present disclosure are described in detail below with reference to the accompanying drawings, so that they can be easily implemented by those skilled in the field to which the present invention relates. However, the exemplary embodiments can be implemented in many different forms and should not be interpreted as being limited to the embodiments set forth herein.

[0029] This application uses terms for degree such as "approximately," "essentially," and the like to indicate values ​​that approximate the value when a tolerance appropriate for manufacturing and quality is present. Furthermore, these terms for degree are used to facilitate the understanding of exemplary embodiments and to prevent an infringer from inadvertently misusing the stated content, which specifies an exact or absolute number.

[0030] In this application, the expression ‘combination(s) thereof’ contained in a Markush-like expression means one or more mixtures or combinations selected from the group consisting of components specified in the Markush-like expression; that is to say, one or more components selected from the group consisting of the components are included.

[0031] In this application, the description of “A and / or B” means “A, B or A and B”.

[0032] In this application, terms such as "first", "second", "A" or "B" are used to distinguish the same terms from one another, unless expressly stated otherwise.

[0033] In this application, “B is placed on A” means that B is in direct contact with A or is arranged over A with another layer or structure in between, and should therefore not be interpreted as being limited to B being arranged in direct contact with A.

[0034] In this application, a singular form is interpreted contextually as containing both a plural form and a singular form, unless explicitly stated otherwise.

[0035] In this application, room temperature refers to 20 to 25 °C.

[0036] In this application, humidity refers to relative humidity.

[0037] In this application, the intensity of a light refers to the intensity of a light source.

[0038] Due to the high integration of semiconductor devices, a high-resolution photomask is required to develop further minute structures on a wafer. With the development of a tiny structure with a smaller width (critical dimension, CD) on the surface of a wafer by forming a complex structural film of a photomask, avoiding the degradation of the photomask's resolution caused by the occurrence of a defect becomes a more critical problem.

[0039] During handling and storage processes, contaminants may adhere to a substrate intended for a raw mask. If contaminants remain on the surface of a substrate for a raw mask, this can lead to problems such as impaired raw mask dissolution due to a defect in the thin film formed on the substrate, a change in the substrate's permeability, or similar issues.

[0040] The inventors of the present disclosure have determined that an impurity remaining on the surface of the substrate can be effectively removed if a first cleaning is carried out by light in an atmosphere with a certain condition and a second cleaning is carried out by applying both a cleaning solution and light irradiation, and have drawn up the present disclosure.

[0041] The following is a detailed description of the present disclosure. Cleaning process of a substrate for a raw mask

[0042] A cleaning process for a substrate for a raw mask according to an embodiment of the present disclosure comprises a first cleaning process of irradiating a cleaning target substrate with a pretreatment light to produce a light-cleaned substrate, and a second cleaning process of applying a first cleaning solution and a posttreatment light to the light-cleaned substrate to produce a substrate for a raw mask.

[0043] The pretreatment light is a light with a wavelength of 50 nm to 300 nm.

[0044] The post-treatment light is a light with a wavelength of 50 nm to 450 nm.

[0045] Any substrate suitable for a raw mask can be used as the cleaning target substrate without restriction. The cleaning target substrate can be a substrate suitable for a semiconductor raw mask measuring 6 inches wide, 6 inches long, and 0.25 inches thick.

[0046] Before the first cleaning process is carried out, a cleaning target substrate and a light source can be arranged in a room where the first cleaning process will be carried out.

[0047] According to this embodiment, the space in which the first cleaning process is carried out can be controlled to maintain an atmosphere with a temperature and pressure within a predetermined range. According to this embodiment, an atmospheric gas with a volume ratio within a predetermined range can be injected into and discharged from the space. The space in which the first cleaning process is carried out can be a cleaning chamber.

[0048] A light source can be positioned to shine light onto the surface of a cleaning target substrate with a uniform intensity. One or more light sources can be arranged within a space where the initial cleaning process takes place to emit light with a uniform intensity.

[0049] The light source can irradiate the surface of the target substrate with pretreatment light. The light source could be, for example, a UV lamp or a laser light source.

[0050] In the first cleaning process, the target substrate can be cleaned with light by shining a pretreatment light onto it. Specifically, when the surface of the target substrate is irradiated with the pretreatment light, some or all of the particles containing organic matter present on the surface can absorb the pretreatment light. The molecular bonds in the organic matter can be broken, and the particles containing the organic matter can be decomposed and removed by the pretreatment light transferring energy to them.

[0051] In the first cleaning process, pretreatment light can be directed onto the surface of the target substrate to be cleaned, creating a light-cleaned substrate. In such a case, energy sufficient to decompose organic substances can be transferred to the surface to be cleaned by the pretreatment light.

[0052] The wavelength of the pretreatment light can be greater than or equal to 50 nm and less than or equal to 300 nm. The wavelength of the pretreatment light can be 70 nm or more. The wavelength of the pretreatment light can be 100 nm or more. The wavelength of the pretreatment light can be 190 nm or less. The wavelength of the pretreatment light can be 180 nm or less. In such a case, the pretreatment light can be easily absorbed by particles containing organic substances.

[0053] The intensity of the pretreatment light can be 25 mW / cm².2 or more. The intensity of the pretreatment light can be 40 mW / cm². 2 or more. The intensity of the pretreatment light can be 60 mW / cm². 2 or more. The intensity of the pretreatment light can be 200 mW / cm². 2 or less. The intensity of the pretreatment light can be 150 mW / cm². 2 or less. In such a case, the pretreatment light can transfer enough energy to sufficiently decompose organic substances.

[0054] In the first cleaning process, the pretreatment light can be directed onto the target substrate by two or more light sources. In such a case, the light intensities applied by each light source for emitting the pretreatment light can be the same. The light intensities applied by each light source can also differ from one another.

[0055] During the first cleaning process, the UI value can be 20% or less according to the equation below. UI(%)=Imax−IminImax+Imin×100

[0056] In equation 1, I max the maximum value of the intensities of the pretreatment light applied by each light source, and I min is the minimum value of the intensities of the pretreatment light applied by each light source.

[0057] In the first cleaning process, the UI value can be 20% or less. The UI value can be 15% or less. The UI value can be 10% or less. The UI value can be 0% or more. In such a case, pretreatment light with a uniform intensity can be directed across the entire surface of the target substrate.

[0058] The pretreatment light can be shone onto a substrate for a time of 50 to 200 seconds. The pretreatment light can be shone onto a substrate for a time of 70 to 180 seconds. The pretreatment light can be shone onto a substrate for a time of 100 to 150 seconds. In such cases, organic substances remaining on the surface of a target substrate can be sufficiently decomposed, the time required to clean the substrate can be reduced, and thus the efficiency of the cleaning process can be increased.

[0059] The initial cleaning process can be performed in a reduced-pressure atmosphere. Degassing pressure can then be applied to the atmosphere surrounding the substrate being cleaned. This prevents contamination of the substrate surface by particle residues formed during pretreatment irradiation. Furthermore, absorption of the pretreatment light by atmospheric gases is avoided, thus preventing any deterioration in light transmission.

[0060] A reduced-pressure atmosphere can be applied to the initial cleaning process. Specifically, the initial cleaning process can be carried out in an atmosphere with a pressure of 50 Pa to 1000 Pa. The atmospheric pressure can be greater than or equal to 100 Pa and less than or equal to 950 Pa. The atmospheric pressure can be greater than or equal to 200 Pa and less than or equal to 500 Pa.

[0061] The first cleaning process can be carried out in an atmosphere with a discharge pressure of 0.01 kPa to 1 kPa. The first cleaning process can be carried out in an atmosphere with a discharge pressure of 0.1 kPa to 0.8 kPa. The first cleaning process can be carried out in an atmosphere with a discharge pressure of 0.2 kPa to 0.5 kPa.

[0062] The first cleaning process can be carried out in an inert atmosphere. An inert atmosphere refers to an atmosphere containing a gas that includes an inert gas as its main component.

[0063] Any gas with low reactivity that cannot cause a chemical reaction with a particle or the like in a first cleaning process can be used as an inert gas without restriction. For example, N2, He, Ar, and the like can be used as an inert gas.

[0064] In an inert atmosphere, the atmospheric gas can comprise an inert gas in a quantity of 90% by volume or more. In an inert atmosphere, the atmospheric gas can comprise an inert gas in a quantity of 95% by volume or more. In an inert atmosphere, the atmospheric gas can comprise an inert gas in a quantity of 99.99% by volume or less.

[0065] In such a case, particle residues generated in the first cleaning process can be stably emitted through the atmospheric gas.

[0066] The first cleaning process can be carried out in an oxidation atmosphere. An oxidation atmosphere refers to an atmosphere containing a gas that includes a reactive oxygen species precursor.

[0067] The reactive oxygen species precursor is a material that can form a reactive oxygen species when exposed to pretreatment light. The reactive oxygen species precursor can contain an oxygen element. The reactive oxygen species can be, for example, O₂ or H₂O.

[0068] Reactive oxygen species refer to oxygen species with a higher reactivity compared to oxygen gas in its ground state. Examples of reactive oxygen species include oxygen radicals, hydroxyl radicals, ozone, excited oxygen, and the like.

[0069] If the initial cleaning process is performed in an oxidizing atmosphere, reactive oxygen species can be generated by irradiation with pretreatment light. In such a case, the pretreatment light can break the molecular bonds within organic substances contained in particles, and simultaneously, the reactive oxygen species can oxidize and decompose these organic substances. This allows particles containing organic substances to decompose more rapidly.

[0070] In the oxidation atmosphere, the atmospheric gas can contain the reactive oxygen precursor in an amount of 5% by volume or more. Alternatively, in the oxidation atmosphere, the atmospheric gas can contain the reactive oxygen precursor in an amount of 30% by volume or less. In such a case, particles containing organic substances can be removed more quickly, and it is possible to avoid excessive attenuation of the pretreatment light by the atmospheric gas.

[0071] The first cleaning process can be carried out at a temperature of 10 to 50 °C. The first cleaning process can be carried out at a temperature of 15 to 30 °C. The first cleaning process can be carried out at room temperature. In such a case, changes in the flatness of the target substrate due to heat can be avoided.

[0072] The first cleaning process can be carried out under conditions of 20 to 70% humidity. The first cleaning process can also be carried out under conditions of 30 to 50% humidity. In such a case, the intensity of the pretreatment light for irradiation can be prevented from becoming excessively weak due to moisture contained in the atmospheric gas.

[0073] A light-cleaned substrate is one from which some or all of a light-absorbing compound located on the surface of the target substrate has been removed. This light-absorbing compound is an organic compound in which bonds between molecules are broken when irradiated with light of this wavelength, causing oxidation and decomposition. Such organic compounds can originate from suspended particles adsorbed onto the substrate surface during manufacturing and storage. These organic compounds can create defects in the thin film formed on the substrate surface, thus necessitating their thorough removal.

[0074] The first cleaning process effectively removes organic substances formed from particles present on the surface of a target substrate before the cleaning process, which involves the application of an initial cleaning solution and post-treatment light, is carried out.

[0075] A cleaning process for a substrate for a raw mask of an embodiment comprises a second cleaning process of applying a first cleaning solution and a post-treatment light to produce a substrate for a raw mask.

[0076] The second cleaning process can be carried out in the same room as the first cleaning process. Alternatively, the second cleaning process can be carried out in a different room than the one where the first cleaning process was carried out.

[0077] A light source can be positioned to shine light onto the surface of the light-cleaned substrate with a uniform intensity. The light source can also irradiate the surface of the light-cleaned substrate with post-treatment light. The light source could be, for example, a UV lamp or a laser light source with a controlled wavelength.

[0078] One or more light sources can be arranged within the room where the second cleaning process is carried out in order to irradiate the surface of the light-cleaned substrate with light of an overall uniform intensity.

[0079] In the second cleaning process, a first cleaning solution can be applied to the surface of the light-cleaned substrate, and then the surface of the light-cleaned substrate can be irradiated with a post-treatment light. In the second cleaning process, the surface of the light-cleaned substrate can be irradiated with a post-treatment light, and then a first cleaning solution can be applied to the surface of the light-cleaned substrate. In the second cleaning process, a first cleaning solution can be applied to the surface of the light-cleaned substrate, and the surface of the light-cleaned substrate can be irradiated with a post-treatment light simultaneously.

[0080] In the second cleaning process, when a first cleaning solution is applied to the surface of a light-cleaned substrate and the substrate surface is then irradiated with post-treatment light, energy from the post-treatment light can be transferred to the hydroxyl radical precursor contained in the first cleaning solution to form a hydroxyl radical. The hydroxyl radical exhibits a high affinity for the substrate. It can oxidize and remove materials that induce grain growth, such as sulfuric acid and nitric acid, that remain on the substrate surface.In such a case, in a raw mask manufacturing process or an exposure process, it can be prevented that the materials remaining on the substrate surface, which induce a grain, are exposed to exposure light and moisture to form a grain on the substrate surface.

[0081] Additionally, if the surface of the light-cleaned substrate is irradiated with post-treatment light, the surface can be activated. This means that the affinity of the substrate surface for a primary cleaning solution can be increased by the post-treatment light with a controlled wavelength. The post-treatment light incident on the light-cleaned substrate surface can transfer energy to the surface, thereby breaking some of the bonds between the elements that make up the substrate surface. The substrate surface can then exhibit high energy and react with hydroxyl radicals and similar compounds present in the primary cleaning solution. A functional group with relatively high polarity can be formed on the substrate surface, and the affinity of the substrate surface for the primary cleaning solution can be temporarily increased.In such a case, it is possible to improve the cleaning effect of the substrate surface by the first cleaning solution during the second cleaning process, and organic substances can be easily removed by reducing the affinity between the organic substances and the substrate surface.

[0082] In the second cleaning process, a cleaning target surface within the light-cleaned substrate can be irradiated with post-treatment light. In such a case, the surface energy of the cleaning target surface can be easily adjusted within a predetermined range of the embodiment.

[0083] A hydroxyl radical has a considerably short lifetime and readily dissipates during cleaning. A challenge lies in maintaining a constant quantity of hydroxyl radicals or generating them in temporarily large amounts. However, in this embodiment, the initial cleaning solution is allowed to come into contact with the surface of a cleaning target on the substrate, and a post-treatment light directly irradiates the initial cleaning solution that comes into contact with the surface of the cleaning target, thereby maintaining a sufficient quantity of hydroxyl radicals to achieve a cleaning effect on the substrate surface.

[0084] The post-treatment light can have a wavelength of 50 nm to 450 nm. The post-treatment light can have a wavelength of 70 nm to 350 nm. The post-treatment light can have a wavelength of 100 nm to 300 nm. In such a case, the surface energy of the substrate can be easily regulated to meet the requirements of the embodiment, and the hydroxyl radicals in the initial cleaning solution can be efficiently generated.

[0085] The wavelength of the post-treatment light can be longer than the wavelength of the pre-treatment light. The difference between the wavelengths of the pre-treatment and post-treatment light can be 50 nm or more. The difference between the wavelengths of the pre-treatment and post-treatment light can be 70 nm or more. The difference between the wavelengths of the pre-treatment and post-treatment light can be 100 nm or more. The difference between the wavelengths of the pre-treatment and post-treatment light can be 150 nm or more. The difference between the wavelengths of the pre-treatment and post-treatment light can be 250 nm or less.The difference in wavelength between the pretreatment light and the posttreatment light can be 200 nm or less. In such a case, the first cleaning solution can easily absorb some of the light energy from the posttreatment light during the second cleaning process.

[0086] If the pretreatment light irradiation is carried out by two or more light sources, the average wavelength of the pretreatment lights applied by the respective light sources is replaced by the above wavelength of the pretreatment light, and the value of the difference between the wavelength value of the pretreatment light and the wavelength value of the posttreatment light is calculated.

[0087] The intensity of the post-treatment light can be 30 mW / cm². 2 or less, 20 mW / cm² 2 or less, 10 mW / cm² 2 or less or 8 mW / cm² 2or less. The intensity of the post-treatment light can be 6 mW / cm². 2 or less. The intensity of the post-treatment light can be 4 mW / cm². 2 or less. The intensity of the post-treatment light can be 0.5 mW / cm². 2 or more. The intensity of the post-treatment light can be 1 mW / cm². 2 or more. The intensity of the post-treatment light can be 2 mW / cm². 2 or more. In such a case, hydroxyl radicals can be generated in sufficient quantity to clean the surface of the light-cleaned substrate.

[0088] Post-treatment light irradiation can be performed for a duration of 20 to 200 seconds. Post-treatment light irradiation can be performed for a duration of 30 to 150 seconds. Post-treatment light irradiation can be performed for a duration of 50 to 100 seconds. In such cases, the time required for a cleaning process can be reduced while efficiently removing organic matter and residues remaining on the substrate.

[0089] In the second cleaning process, the target substrate can be irradiated with post-treatment light from two or more light sources. In such a case, the entire surface of the light-cleaned substrate can be irradiated with post-treatment light of sufficient intensity to generate hydroxyl radicals.

[0090] A low-pressure mercury lamp, for example, can be used as a light source for irradiation with post-treatment light.

[0091] A first cleaning solution can be applied to the surface of the light-cleaned substrate through a nozzle during the second cleaning process. The first cleaning solution can be applied through one or more nozzles to ensure even distribution across the entire surface of the light-cleaned substrate.

[0092] The initial cleaning solution may contain a hydroxyl radical precursor. The hydroxyl radical precursor is a material that receives energy from the post-treatment light to form a hydroxyl radical. Examples of hydroxyl radical precursors include H₂O, H₂O₂, O₃, and similar substances.

[0093] The initial cleaning solution can include SC-1 (Standard Clean-1) solution (SC-1 solution is a solution comprising NH4OH, H2O2, and H2O), ozonated water, ultrapure water, hydrogenated water, carbonated water, or a combination of two or more of the aforementioned. In such a case, the remaining organic particles not removed in the initial cleaning process can be effectively oxidized and removed by the initial cleaning solution, and a sufficient quantity of hydroxyl radicals can be generated by post-treatment light.

[0094] A total flow rate of the first cleaning solution applied to the surface of the light-cleaned substrate with an area of ​​100 cm² 2 up to 300 cm 2The applied flow rate can be 2000 ml / min or more. The total flow rate of the first cleaning solution can be 3000 ml / min or more. Alternatively, the total flow rate of the first cleaning solution can be 5000 ml / min or less. In such a case, hydroxyl radicals can be introduced in sufficient quantity onto the surface of the light-cleaned substrate, and any particles remaining after the first cleaning process can be adequately removed.

[0095] The second cleaning process can be carried out at a temperature of 10 °C to 100 °C. The second cleaning process can be carried out at a temperature of 30 °C to 70 °C. The second cleaning process can be carried out at room temperature. In such a case, it can be prevented that the flatness of the light-cleaned substrate is deformed due to atmospheric temperature.

[0096] A cleaning method for a substrate for a raw mask of the embodiment comprises a wet cleaning process for cleaning the surface of the substrate for a raw mask using a second cleaning solution.

[0097] In the wet cleaning process, it is possible to remove any remaining contamination from the surface of a raw mask by applying a second cleaning solution. Specifically, the raw mask substrate can comprise a front surface, on which a thin film has formed, and a rear surface positioned opposite the front surface. The second cleaning solution can be applied to the respective front and rear surfaces via nozzles to clean the raw mask substrate.

[0098] The application of the second cleaning solution can be carried out using ultrasound. The ultrasonic power applied to each nozzle can be greater than 0 W and less than or equal to 50 W. Alternatively, the ultrasonic power applied to each nozzle can be greater than or equal to 10 W and less than or equal to 45 W. The ultrasonic power of a nozzle positioned at the front surface can be lower than the ultrasonic power of a nozzle positioned at the rear surface. Conversely, the ultrasonic power of a nozzle positioned at the front surface can be the same as that of a nozzle positioned at the rear surface.

[0099] The ultrasonic frequency applied to each nozzle can be greater than or equal to 0.5 MHz and less than or equal to 3 MHz. The ultrasonic frequency applied to each nozzle can be greater than or equal to 0.8 MHz and less than or equal to 2 MHz. The ultrasonic frequency of a nozzle applied to the front surface can be lower than the ultrasonic frequency of a nozzle applied to the rear surface. Alternatively, the ultrasonic frequency of a nozzle applied to the front surface can be the same as the ultrasonic frequency of a nozzle applied to the rear surface.

[0100] The second cleaning solution can be applied using one or more types or solutions. The second cleaning solution can include carbonated water, ozonated water, hydrogenated water, SC-1 solution, ultrapure water, or a combination of two or more of the aforementioned.

[0101] A wet cleaning process can be carried out for a period of time from 1 minute to 40 minutes. The wet cleaning process can be carried out for a period of time from 2 minutes to 25 minutes.

[0102] In such a case, it is possible to thoroughly remove foreign substances that are present on the surface of a substrate for a raw mask.

[0103] A cleaning process for a raw mask substrate can include a rinsing and a drying process. This removes any cleaning solution remaining on the surface of the raw mask substrate, thereby preventing damage to the substrate and the formation of turbidity caused by the remaining cleaning solution.

[0104] A rinsing process can be performed on a substrate for a raw mask after the second cleaning process has been completed. Ultrapure water, carbonated water, hydrogenated water, or a combination of two or more of the aforementioned can be used in the rinsing process.

[0105] In a drying process, a substrate for a raw mask can be dried after the rinsing process is complete. During the drying process, the substrate for the raw mask can be rotated at a speed within a predetermined range of the embodiment. A ramp-down method, which involves applying an initial rotational speed of the substrate to a high value and then gradually decreasing the rotational speed, can be used in the drying process. A ramp-up method, which involves applying an initial rotational speed of the substrate to a low value and then gradually increasing the rotational speed, can also be used in the drying process.

[0106] When the ramp-up procedure is applied in the drying process, the minimum rotational speed of the substrate can be 0 rpm or more, 100 rpm or more, 500 rpm or more, 800 rpm or more, or 1000 rpm or more, and the maximum rotational speed of the substrate can be 3500 rpm or less, 3000 rpm or less, 2500 rpm or less, or 2000 rpm or less.

[0107] When the shutdown procedure is applied in the drying process, the maximum rotational speed of the substrate can be 3500 rpm or less, 3000 rpm or less, 2500 rpm or less, 2000 rpm or less, and the minimum rotational speed of the substrate can be 0 rpm or more, 100 rpm or more, 500 rpm or more, 800 rpm or more, or 1000 rpm or more.

[0108] By applying the rinsing and drying process to the substrate for a raw mask, the cleaning solution remaining on the substrate surface can be effectively removed.

[0109] A substrate for a raw mask, purified by the above-described cleaning process for a substrate for a raw mask, may contain sulfuric acid ions in an amount of 0 ng / cm³. 2 up to 0.1 ng / cm³ 2 or less, nitric acid ions in an amount of 0 ng / cm³ 2 up to 0.4 ng / cm² 2 or less, nitrous acid ions in an amount of 0 ng / cm³ 2 up to 0.05 ng / cm² 2 or less and ammonium ions in an amount of 0 ng / cm³ 2 up to 0.05 ng / cm² 2 or less.

[0110] One embodiment can effectively remove residues that have a high affinity for the substrate surface and are difficult to remove by applying the cleaning method described above.

[0111] The amount of residual ions present on the substrate surface can be measured using an ion chromatography method. Specifically, a target substrate is placed in a clean bag, and ultrapure water is injected into the clean bag. The clean bag is immersed in a water tank at 90°C for 120 minutes, after which an ion wash solution is obtained from the clean bag. The ion wash solution and the elution are then injected into an ion chromatography column for analysis, allowing the determination of the residual ion weights. The measured residual ion weights are divided by the front surface area of ​​the substrate for a crude mask, and the amounts of residual ions are calculated.

[0112] For example, a solution comprising KOH, LiOH, MSA (methanesulfonic acid) and NaOH was applied as an elution and a mobile phase flow rate greater than or equal to 0.4 ml / min and less than or equal to 2.0 ml / min was set.

[0113] The Dionex ICS-2100 ion chromatography model, available from THERMO SCIENTIFIC Corporation, can be used as an ion chromatography analysis device.

[0114] A substrate for a raw mask, to which a substrate purification process for a raw mask is applied, may contain sulfuric acid ions, which are removed by an ion chromatography process in an amount of 0 ng / cm³. 2 up to 0.1 ng / cm³ 2 Sulfuric acid ions were measured at a concentration of 0.05 ng / cm³. 2 or less. The sulfuric acid ions can be present in amounts of 0.03 ng / cm³. 2 or be less comprehensive.

[0115] The substrate for a raw mask, to which a raw mask substrate purification process is applied, may contain nitric acid ions, which are detected by an ion chromatography process in an amount of 0 ng / cm³. 2 up to 0.4 ng / cm² 2 Nitric acid ions were measured at a concentration of 0.3 ng / cm³. 2 or less. The nitric acid ions can be present in amounts of 0.2 ng / cm³. 2 or less. The nitric acid ions can be present in amounts of 0.1 ng / cm³. 2 or less. The nitric acid ions can be present in amounts of 0.05 ng / cm³. 2 or be less comprehensive.

[0116] A substrate for a raw mask, to which a substrate purification process for a raw mask is applied, may contain nitrous acid ions, which are detected by an ion chromatography process in an amount of 0 ng / cm³. 2 up to 0.05 ng / cm² 2The ions of nitrous acid were measured at a concentration of 0.02 ng / cm³. 2 or less. The ions of nitrous acid can be present in amounts of 0.02 ng / cm³. 2 or less. The ions of nitrous acid can be present in amounts as low as 0.01 ng / cm³. 2 or be less comprehensive.

[0117] A substrate for a raw mask, to which a raw mask cleaning process is applied, can contain ammonium ions in an amount of 0 ng / cm². 2 up to 1.5 ng / cm² 2 The ammonium ions can be present in amounts of 1.3 ng / cm². 2 or less. The ammonium ions can be present in amounts of 1 ng / cm². 2 or less. The ammonium ions can be present in amounts of 0.7 ng / cm³. 2 or be less comprehensive.

[0118] A substrate for a raw mask, to which a substrate purification process for a raw mask is applied, can contain chloride ions in an amount of 0 ng / cm². 2 up to 0.1 ng / cm³ 2 The ammonium ions can be present in amounts of 0.05 ng / cm². 2 or less. The ammonium ions can be present in amounts of 0.01 ng / cm³. 2 or be less comprehensive.

[0119] In such a case, it is possible to avoid the formation of a grain defect on the substrate surface during a raw mask manufacturing process or an exposure process.

[0120] A substrate for a raw mask, to which a substrate cleaning process for a raw mask is applied, may have a PRE value of 90% or more according to Equation 2 below. PRE(%)=Pb−PaPb×100

[0121] In equation 2, the P b-Value the number of particles, measured against the target substrate for cleaning, and the P a The value is the number of particles, measured on the substrate for a raw mask.

[0122] The detailed description of a method for measuring P b -value and of the P a The particle count is determined. Specifically, a target substrate sample is placed in a defect tester. The number of particles within a 146 mm vertical and horizontal area on the surface of the target substrate sample is then measured using the defect tester. While the particle count is being measured, a test light is applied by a green laser with a wavelength of 532 nm. The laser power is set to 3000 mW (1050 mW as the laser power measured at the surface of the target substrate), and the movement speed of a stage is set to 2 for the measurement.

[0123] For example, the P b -value and the P a -Value can be measured using a defect tester model M6641S, available from LASERTEC.

[0124] A raw mask substrate to which a raw mask substrate cleaning process is applied can have a PRE value of 90% or more according to Equation 2 below. The PRE value can be 95% or more. The PRE value can be 99% or more. The PRE value can be 100% or less. In such a case, a raw mask substrate can be provided in which defects in optical properties and defects in the thin film caused by particles are effectively reduced. Substrate for a raw mask

[0125] A substrate for a raw mask according to a further embodiment of the present disclosure is a quartz substrate with a flatness of 0.5 µm.

[0126] Controlling the flatness of the substrate for a raw mask can reduce in-plane variation in optical properties of the thin film to be formed on the substrate. Furthermore, when developing a structure on the wafer surface using a photomask deposited on the substrate, it is possible to avoid structural distortion.

[0127] The substrate for a raw mask must be cleaned before it is used for the production of a raw mask. The embodiment applies the cleaning method of a substrate for a raw mask as described above and can thereby provide a substrate for a raw mask that, in addition to controlling flatness, contains a small amount of residues.

[0128] The flatness of the substrate of a raw mask can be measured, for example, using the UltraFlat model, available from Corning Tropel Corporation.

[0129] The flatness of a substrate for a raw mask can be 0.5 µm or less. In such a case, variation in the optical properties in the in-plane direction of a thin film to be formed on the substrate can be reduced.

[0130] The substrate for a crude mask contains sulfuric acid ions in an amount of 0 ng / cm³. 2 up to 0.1 ng / cm³ 2 Nitric acid ions in a quantity of 0 ng / cm³ 2 up to 0.4 ng / cm² 2 , nitrous acid ions in an amount of 0 ng / cm³ 2 up to 0.05 ng / cm² 2 and ammonium ions in an amount of 0 ng / cm³ 2 up to 0.05 ng / cm² 2 as residual ions, measured by an ion chromatography method.

[0131] The substrate for a raw mask can contain chloride ions in an amount of 0 ng / cm². 2 up to 0.1 ng / cm³ 2 as residual ions, measured by an ion chromatography method.

[0132] By controlling the amount of ions remaining in the substrate for a raw mask, it is possible to avoid the occurrence of structural distortion on a wafer caused by grains grown on the substrate surface. In particular, even when a solution containing ammonium ions, such as an SC-1 solution, is used as a cleaning solution to clean the substrate for a raw mask, the amount of ammonium ions remaining on the substrate can be controlled to avoid affecting the resolution of the raw mask.

[0133] The description of a measurement method for the amount of residual ions of a substrate for a raw mask using an ion chromatography method is the same as the description already given above and is therefore omitted.

[0134] The substrate for a crude mask can include sulfuric acid ions, which are detected by an ion chromatography method in an amount of 0 ng / cm³. 2 up to 0.1 ng / cm³ 2 Sulfuric acid ions were measured at a concentration of 0.05 ng / cm³. 2 or less. The sulfuric acid ions can be present in amounts of 0.03 ng / cm³. 2 or be less comprehensive.

[0135] The substrate for a crude mask can include nitric acid ions, which are detected by an ion chromatography method in an amount of 0 ng / cm³. 2 up to 0.4 ng / cm² 2 Nitric acid ions were measured at a concentration of 0.3 ng / cm³. 2or less. The nitric acid ions can be present in amounts of 0.2 ng / cm³. 2 or less. The nitric acid ions can be present in amounts of 0.1 ng / cm³. 2 or less. The nitric acid ions can be present in amounts of 0.05 ng / cm³. 2 or be less comprehensive.

[0136] The substrate for a crude mask can include nitrous acid ions detected by ion chromatography at a concentration of 0 ng / cm³. 2 up to 0.05 ng / cm² 2 The ions of nitrous acid were measured at a concentration of 0.02 ng / cm³. 2 or less. The ions of nitrous acid can be present in amounts as low as 0.01 ng / cm³. 2 or be less comprehensive.

[0137] The substrate for a crude mask can include ammonium ions, which are detected by an ion chromatography method in an amount of 0 ng / cm². 2 up to 1.5 ng / cm² 2The ammonium ions can be measured in amounts of 1 ng / cm³. 2 or less. The ammonium ions can be present in amounts of 0.7 ng / cm³. 2 or be less comprehensive.

[0138] The substrate for a crude mask can include chloride ions, which are detected by an ion chromatography method in an amount of 0 ng / cm³. 2 up to 0.1 ng / cm³ 2 The chloride ions were measured at a concentration of 0.05 ng / cm³. 2 or less. The chloride ions can be present in amounts as low as 0.01 ng / cm². 2 or be less comprehensive.

[0139] In such a case, the growth of a crystal caused by residues can be effectively prevented.

[0140] The substrate for a raw mask can be a substrate for a semiconductor with a size of 6 inches wide, 6 inches long and 0.25 inches high. Raw mask

[0141] A raw mask according to a further embodiment of the present disclosure comprises the substrate for a raw mask described above.

[0142] The raw mask can comprise a raw mask substrate and a thin film arranged on the raw mask substrate.

[0143] The thin film may comprise an etch stop film, a phase shift film, a light shielding film, an etch mask film, or a combination of two or more of the aforementioned.

[0144] Such a raw mask can effectively prevent a deterioration of resolution depending on the exposure process, and a cleaning cycle for removing haze can be extended.

[0145] The following section provides a detailed description of embodiments in further detail. Evaluation example: PRE (particle removal efficiency) test

[0146] Identical synthetic quartz substrates measuring 6 inches wide, 6 inches long, and 0.25 inches high, stored in SMIF (Standard Mechanical Interface) pods, were opened inside a defect tester to be prepared as cleaning target substrate samples. The surface of a cleaning target substrate sample was imaged to determine the number of observed particles. Specifically, cleaning target substrate samples were arranged in a LASERTEC M6641S defect tester. Subsequently, the number of particles was measured over a 146 mm vertical and horizontal area on the substrate surface.When measuring the number of particles, a test light is applied by a green light laser with a wavelength of 532 nm, the power of the laser is set to 3000 mW (1050 mW as power of a laser, measured at the surface of the substrate as the measurement target) and the movement speed of an object stage is set to 2 for the measurement.

[0147] The following describes a first cleaning process for target substrate samples in experimental examples to produce light-cleaned substrate samples. Specifically, a discharge pressure of 0.350 kPa, an atmospheric temperature of 23 °C, and an atmospheric humidity of 45% ± 5% were applied to a cleaning chamber. An atmospheric gas consisting of 16.7 vol% O₂ and 83.3 vol% N₂ was introduced into the cleaning chamber, and a pretreatment light source with a wavelength of 172 nm and an intensity of 40 mW / cm² was activated. 2The surface of a cleaning target substrate sample was irradiated. The pretreatment irradiation time for each experimental example is listed in Table 1 below.

[0148] After completion of the first cleaning process, a second cleaning process was performed on the light-cleaned substrate sample of each experimental example to prepare a substrate sample for a raw mask. Specifically, in the second cleaning process, the light-cleaned substrate sample was arranged, and then ozonated water was applied through two nozzles at a flow rate of 2500 ml / min. The amount of dissolved ozone in the ozonated water was adjusted to 11.2 mg / L. A pretreatment light source with a wavelength of 254 nm and an intensity of 8 mW / cm² was used. 2The surface of the light-cleaned substrate was irradiated by two light sources positioned on the sample. The irradiation time with post-treatment light is listed for each experimental example in Table 1 below.

[0149] A wet cleaning process was performed on the raw mask substrate sample after completion of the second cleaning process. Specifically, hydrogenated water and SC-1 solution were simultaneously applied to the surface of the raw mask substrate at a flow rate of 700 ml / min. The SC-1 solution consisted of ammonia water at 0.1% by volume, oxygenated water at 0.08% by volume, and ultrapure water at 99.82% by volume.

[0150] The substrate sample for a raw mask was rinsed with hydrogenated and carbonated water and dried after completion of the wet cleaning process. Drying was achieved using a ramp-up procedure with a minimum substrate rotation speed of 0 rpm and a final rotation speed of 1500 rpm. Subsequently, the surface of each sample was imaged to determine the particle count. The particle count measurement was performed under the same conditions as the measurement of the surface count of the substrate after cleaning.

[0151] The PRE-(%) value according to equation 2 of each experimental example was calculated from the number of particles measured on the surface of the sample of the cleaning target substrate and the number of particles measured on the surface of the sample of the substrate for a raw mask after rinsing and drying.

[0152] The PRE value calculated for each experimental example is listed in Table 1 below. Evaluation example: Measurement of residues

[0153] Example 1: A synthetic quartz substrate with a width of 6 inches, a length of 6 inches, a height of 0.25 inches, a flatness of 0.5 µm or less, and a birefringence of 5 nm or less was prepared as a cleaning target substrate sample. Image examination of the synthetic quartz substrate surface revealed no particles 60 nm or larger.

[0154] A first cleaning process was performed on the target substrate sample to produce a light-cleaned substrate sample. Specifically, a discharge pressure of 0.350 kPa, an atmospheric temperature of 23 °C, and an atmospheric humidity of 45% ± 5% were applied to a cleaning chamber, and an atmospheric gas mixture of O₂ at 16.7% by volume and N₂ at 83.3% by volume was introduced into the cleaning chamber. Subsequently, a pretreatment light with a wavelength of 172 nm and an intensity of 40 mW / cm² was applied. 2 The surface of the target substrate sample for cleaning. Irradiation with pretreatment light was performed for a duration of more than 100 seconds and less than or equal to 150 seconds.

[0155] After completion of an initial cleaning process, a second cleaning process was performed on the sample of the light-cleaned substrate from each experimental example to prepare a substrate sample for a raw mask. Specifically, the substrate sample was arranged, and in the second cleaning process, ozonated water was applied at a flow rate of 2500 ml / min through two or more nozzles. The amount of dissolved ozone in the ozonated water was adjusted to 11.2 mg / L. The surface of the light-cleaned substrate sample was then treated with post-treatment light at a wavelength of 254 nm and an intensity of 8 mW / cm², using two light sources positioned on the sample. 2The application of ozonated water and the irradiation with a post-treatment light are performed simultaneously or sequentially within a short time. The duration of the post-treatment light irradiation for each experimental example is listed in Table 1 below.

[0156] A wet cleaning process was performed on a sample of a raw mask substrate after completion of the second cleaning process. Specifically, hydrogenated water and SC-1 solution were simultaneously applied to the surface of the raw mask substrate at a flow rate of 700 ml / min. The wet cleaning process was carried out for approximately 20 minutes. The SC-1 solution was applied as a single solution comprising 0.1% by volume ammonia water, 0.1% by volume oxygenated water, and 99.82% by volume ultrapure water.

[0157] The substrate sample for a raw mask was rinsed with hydrogenated and carbonated water after completion of the wet cleaning process and then dried. Drying of the substrate was carried out using a ramp-up procedure with a minimum substrate rotation speed of 0 rpm and a final substrate rotation speed of 1500 rpm.

[0158] The amount of residual ions present on the surface of the substrate for a raw mask was measured by ion chromatography after rinsing and drying. Specifically, the substrate was placed in a clean bag as the target, and 100 ml of ultrapure water was injected into the clean bag. After immersing the clean bag in a water tank at 90°C for 120 minutes, an ion washout solution and an eluent were injected into an ion chromatography column for analysis, and the mass of the ions was measured for each ion type. The mass of the ions measured for each ion type was then divided by the surface area (504 cm²). 2 ) divided, and the amounts of the respective ion types were calculated.

[0159] When ion chromatography was measured, a solution comprising KOH, LiOH, MSA (methanesulfonic acid) and NaOH was used as the eluent, and the flow rate of the mobile phase was set greater than or equal to 0.4 ml / min and less than or equal to 2.0 ml / min.

[0160] The Dionex ICS-2100 ion chromatography model, available from THERMOSCIENTIFIC, was used as the analysis device for ion chromatography.

[0161] Example 2: A substrate for a crude mask was prepared under the same conditions as Example 1, and the amount of residual ions was measured by ion chromatography for the respective ion species. However, a substrate in which no particle with a size of 80 nm or larger was found when an image measurement of the surface of the synthetic quartz substrate was performed was used as the purification target substrate sample. The substrate was a synthetic quartz substrate with a width of 6 inches, a length of 6 inches, a height of 0.25 inches, a flatness of 0.5 µm, and a birefringence of 5 nm.

[0162] Example 3: A substrate for a raw mask was prepared under the same conditions as Example 1, and the amount of residual ions was measured for the respective ion species by ion chromatography. However, the irradiation time with pretreatment light was set to be greater than 0 seconds and less than or equal to 50 seconds.

[0163] Example 4: A substrate for a raw mask was prepared under the same conditions as in Example 2, and the amount of residual ions was measured for the respective ion species by ion chromatography. However, the irradiation time with pretreatment light was set to be greater than 0 seconds and less than or equal to 50 seconds.

[0164] Example 5: A substrate for a raw mask was prepared under the same conditions as Example 1, and the amount of residual ions was measured for the respective ion species by ion chromatography. However, the irradiation time with pretreatment light was adjusted to be greater than 50 seconds and less than or equal to 100 seconds.

[0165] Example 6: A substrate for a raw mask was prepared under the same conditions as in Example 2, and the amount of residual ions was measured for the respective ion species by ion chromatography. However, the irradiation time with pretreatment light was adjusted to be greater than 50 seconds and less than or equal to 100 seconds.

[0166] Example 7: A substrate for a raw mask was prepared under the same conditions as Example 1, and the amount of residual ions was measured for the respective ion species by ion chromatography. However, the time for irradiation with post-treatment light was set to be greater than 0 seconds and less than or equal to 50 seconds.

[0167] Example 8: A substrate for a raw mask was prepared under the same conditions as Example 2, and the amount of residual ions was measured for the respective ion species by ion chromatography. However, the time for irradiation with post-treatment light was set to be greater than 0 seconds and less than or equal to 50 seconds.

[0168] Example 9: A substrate for a raw mask was prepared under the same conditions as Example 1, and the amount of residual ions was measured for the respective ion species by ion chromatography. However, the time for irradiation with post-treatment light was adjusted to be more than 100 seconds and less than or equal to 150 seconds.

[0169] Example 10: A substrate for a raw mask was prepared under the same conditions as Example 2, and the amount of residual ions was measured for the respective ion species by ion chromatography. However, the irradiation time with post-treatment light was adjusted to be greater than 100 seconds and less than or equal to 150 seconds.

[0170] Example 11: A substrate for a raw mask was prepared under the same conditions as Example 1, and the amount of residual ions was measured for the respective ion species by ion chromatography. However, the time for post-treatment light irradiation was adjusted to be greater than 150 seconds and less than or equal to 200 seconds.

[0171] Example 12: A substrate for a raw mask was prepared under the same conditions as Example 2, and the amount of residual ions was measured for the respective ion species by ion chromatography. However, the irradiation time with post-treatment light was adjusted to be greater than 150 seconds and less than or equal to 200 seconds.

[0172] Example 13: A substrate for a raw mask was prepared under the same conditions as Example 1, and the amount of residual ions was measured for the respective ion species by ion chromatography. However, the irradiation time with pretreatment light was adjusted to be greater than 150 seconds and less than or equal to 200 seconds.

[0173] Example 14: A substrate for a raw mask was prepared under the same conditions as Example 2, and the amount of residual ions was measured for the respective ion species by ion chromatography. However, the irradiation time with pretreatment light was adjusted to be greater than 150 seconds and less than or equal to 200 seconds.

[0174] Comparative Example 1: A synthetic quartz substrate with a flatness of 0.5 µm or less and a birefringence of 5 nm or less was prepared. Image measurements of the synthetic quartz substrate's surface revealed no particles larger than 60 nm. The amount of residual ions in the synthetic quartz substrate was measured for each ion type by ion chromatography. The ion chromatography measurement conditions were set to be the same as in Example 1.

[0175] Comparative Example 2: A synthetic quartz substrate with a flatness of 0.5 µm or less and a birefringence of 5 nm or less was prepared. Image measurements of the synthetic quartz substrate's surface revealed no particles 80 nm or larger. The amount of residual ions in the synthetic quartz substrate was measured for each ion type by ion chromatography. The ion chromatography measurement conditions were set to be the same as in Example 1.

[0176] Comparative example 3: A synthetic quartz substrate with a flatness of 0.5 µm or less and a birefringence of 5 nm or less was prepared. Image measurements of the surface of the synthetic quartz substrate revealed no particles with a size of 60 nm or larger.

[0177] A second cleaning process was performed on the sample of the target substrate, while a first cleaning process was not applied. The conditions for the second cleaning process were the same as for Example 1. A wet cleaning process, a rinsing process, and a drying process were performed on the raw mask substrate sample after completion of the second cleaning process. The wet cleaning, rinsing, and drying processes were performed under the same conditions as for Example 1.

[0178] Residual ions in the sample of the light-purified substrate were measured by ion chromatography. The ion chromatography measurement conditions were set to be the same as for Example 1.

[0179] Comparative Example 4: A sample of a light-purified substrate was prepared under the same conditions as Comparative Example 3, and the amount of residual ions was measured for the respective ion species by ion chromatography. However, the substrate used as the purification target sample was a synthetic quartz substrate with a flatness of 0.5 µm or less and a birefringence of 5 nm or less, and as a result of the image measurement, no particle with a size of 80 nm or more was found in the substrate.

[0180] A first cleaning process was not applied to the sample of the target substrate, and a second cleaning process was performed to prepare a sample of a raw mask substrate. The conditions of the second cleaning process were set to be the same as for Example 1. A wet cleaning, rinsing, and drying process was performed on the raw mask substrate sample after completion of the second cleaning process. The wet cleaning, rinsing, and drying processes were performed under the same conditions as for Example 1.

[0181] The amounts of residual ions measured for each ion type by ion chromatography of each example and comparison example are listed in Table 2 below. [Table 1] Time for irradiation with pretreatment light (s) Time for post-treatment light irradiation (s) PRE (%) Experiment 1 More than 0 and less than or equal to 50 More than 0 and less than or equal to 50 77,3 Experiment 2 More than 0 and less than or equal to 50 More than 50 and less than or equal to 100 88,2 Experiment 3 More than 0 and less than or equal to 50 More than 100 and less than or equal to 150 87,9 Experiment 4 More than 0 and less than or equal to 50 More than 150 and less than or equal to 200 87,8 Experiment 5 More than 50 and less than or equal to 100 More than 0 and less than or equal to 50 82,2 Experiment 6 More than 50 and less than or equal to 100 More than 50 and less than or equal to 100 92,7 Experiment 7 More than 50 and less than or equal to 100 More than 100 and less than or equal to 150 92,1 Experiment 8 More than 50 and less than or equal to 100 More than 150 and less than or equal to 200 92,1 Experiment 9 More than 100 and less than or equal to 150 More than 0 and less than or equal to 50 86,4 Experiment 10 More than 100 and less than or equal to 150 More than 50 and less than or equal to 100 99,5 Experiment 11 More than 100 and less than or equal to 150 More than 100 and less than or equal to 150 99,2 Experiment 12 More than 100 and less than or equal to 150 More than 150 and less than or equal to 200 99,2 Experiment 13 More than 150 and less than or equal to 200 More than 0 and less than or equal to 50 86,3 Experiment 14 More than 150 and less than or equal to 200 More than 50 and less than or equal to 100 97,7 Experimental More than 150 and less than More than 100 and less than 97,1 Game 15 or even 200 or even 150 Experiment 16 More than 150 and less than or equal to 200 More than 150 and less than or equal to 200 97,0 Table 2 Type of cleaning target substrate The amount of residues for the respective ion types (ng / cm2) Cl- NO2- NO3- SO4 2- NH4+ Example 1 A 0,01 0,01 0,09 0,02 0,54 Example 2 B 0,01 0 0,02 0,02 1,00 Example 3 A 0,01 0,01 0,19 0,05 0,66 Example 4 B 0,01 0 0,11 0,04 1,14 Example 5 A 0,01 0 0,17 0,04 0,62 Example 6 B 0,01 0 0,10 0,03 1,04 Example 7 A 0,01 0,01 0,20 0,04 0,71 Example 8 B 0,01 0 0,12 0,04 1,20 Example 9 A 0,01 0 0,13 0,03 0,59 Example 10 B 0,01 0 0,05 0,03 1,08 Example 11 A 0,01 0 0,14 0,03 0,58 Example 12 B 0,01 0 0,07 0,03 1,06 Example 13 A 0,01 0,01 0,15 0,03 0,61 Example 14 B 0,01 0 0,07 0,03 1,02 Comparison example 1 A 0,01 0 0,26 0,06 0,19 Comparison example 2 B 0,01 0 0,11 0,06 0,94 Comparison example 3 A 0,01 0,01 0,21 0,05 1,12 Comparison example 4 B 0,01 0 0,10 0,05 2,23 * Type A of the cleaning target substrate is a synthetic quartz substrate with a width of 6 inches, a length of 6 inches, a height of 0.25 inches, a flatness of 0.5 µm or less, a birefringence of 5 nm or less, and no particles larger than 60 nm were found as a result of surface imaging. Type B of the cleaning target substrate is a synthetic quartz substrate with a width of 6 inches, a length of 6 inches, a height of 0.25 inches, a flatness of 0.5 µm or less, a birefringence of 5 nm or less, and no particles larger than 80 nm were found as a result of surface imaging.

[0182] In Table 1, experimental examples 1 to 16 show PRE values ​​of 75% or more. In particular, when the pretreatment light irradiation time was set to more than 50 seconds and the posttreatment light irradiation time was set to more than 50 seconds, PRE values ​​show a value of 90% or more.

[0183] Table 2 contained the amounts of sulfuric acid ions, nitric acid ions, nitrous acid ions, and ammonium ions, measured by ion chromatography, within the range limited in the embodiments. In particular, the amounts of nitric acid ions and sulfuric acid ions in Examples 1 to 14 are lower than the values ​​in the comparison examples.

[0184] For ammonium ions, the amounts measured in Examples 1 to 14 show a higher value than the values ​​in comparison examples 1 and 2, where cleaning using the SC-1 solution was not performed. This is assumed to be influenced by NH4 ions present in the SC-1 solution applied as the cleaning solution. However, the amount of ammonium was observed to be lower in Examples 1 to 14 than in comparison examples 3 and 4, where cleaning with light was carried out by irradiation with a post-treatment light.

[0185] Although the exemplary embodiments have been described in detail, the scope of the present invention is not limited thereto, and modifications and changes made by those skilled in the field using the basic concept of the present invention as defined in the following claims shall fall within the scope of the present invention. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] KR 100316374

[0006] KR 100745065

[0006]

Claims

[1] A method for cleaning a substrate for a mask blank, comprising: a first cleaning process of irradiating a cleaning target substrate with a pretreatment light to produce a light-cleaned substrate; and a second cleaning process of applying a first cleaning solution and a post-treatment light to the light-cleaned substrate to produce a substrate for a mask blank; wherein the pretreatment light is a light having a wavelength of 50 nm to 300 nm, and wherein the post-treatment light is a light with a wavelength of 50 nm to 450 nm. [2] A cleaning method of a substrate for a mask blank according to claim 1, wherein an intensity of the pretreatment light is 25 mW / cm 2 or more. [3] A cleaning method of a substrate for a mask blank according to claim 1, wherein the cleaning target substrate is irradiated with the pretreatment light by two or more light sources, and where a UI value according to equation 1 below is 20% or less; UI(%)=Imax−IminImax+Imin×100 where in equation 1 I max is the maximum value of the intensities of the pretreatment light applied by each light source and I min is the minimum value of the intensities of the pretreatment light applied by each light source. [4] The cleaning method of a substrate for a mask blank according to claim 1, wherein the first cleaning process is performed in a reduced pressure atmosphere, and the atmosphere in which the cleaning target substrate is placed is applied by a discharge pressure of 0.01 kPa to 1 kPa. [5] A method for cleaning a substrate for a mask blank according to claim 1, wherein the first cleaning solution comprises SC-1 (Standard Clean-1) solution or ozone water or ultra-pure water or hydrogen water or carbonated water; and where the SC-1 solution is a solution comprising NH4OH, H2O2 and H2O. [6] A cleaning method of a substrate for a mask blank according to claim 1, wherein the light-cleaned substrate is one in which part or all of a compound that absorbs light having a wavelength of 100 to 190 nm is removed. [7] A cleaning method of a substrate for a mask blank according to claim 1, wherein the first cleaning solution comprises a hydroxyl radical precursor, and wherein the post-treatment light forms a hydroxyl radical by irradiation when the first cleaning solution is applied to the light-cleaned substrate. [8] A cleaning method of a substrate for a mask blank according to claim 1, wherein the substrate for a mask blank contains sulfuric acid ions in an amount of 0 ng / cm 2 up to 0.1 ng / cm 2 , nitric acid ions in an amount of 0 ng / cm 2 up to 0.4 ng / cm 2 , ions of nitrous acid in an amount of 0 ng / cm 2 up to 0.05 ng / cm 2 and ammonium ions in an amount of 0 ng / cm 2 up to 1.5 ng / cm 2 as residual ions, measured by the method of ion chromatography. [9] The cleaning method of a substrate for a mask blank according to claim 1, wherein the PRE value of the substrate for a mask blank is 90% or more according to the following equation 2; PRE(%)=Pb−PaPb×100 where in equation 2 the P b -value is the number of particles measured on the cleaning target substrate, and the P a -value is the number of particles measured on the substrate for a blank mask. [10] A substrate for a mask blank, which is a quartz substrate having a flatness of 0.5 µm or less, wherein the substrate for a mask blank contains sulfuric acid ions in an amount of 0 ng / cm 2 up to 0.1 ng / cm 2 , nitric acid ions in an amount of 0 ng / cm 2 up to 0.4 ng / cm 2 , ions of nitrous acid in an amount of 0 ng / cm 2 up to 0.05 ng / cm 2 and ammonium ions in an amount of 0 ng / cm 2 up to 1.5 ng / cm 2 as residual ions, measured by the method of ion chromatography. [11] The substrate for a mask blank according to claim 10, wherein the substrate for a mask blank contains chloride ions in an amount of 0 ng / cm 2 up to 0.1 ng / cm 2 as residual ions, measured by the method of ion chromatography. [12] A mask blank comprising the substrate for a mask blank according to claim 10.