Removal of contaminants from EUV masks

Abstract

To provide removal of contaminants from EUV masks.SOLUTION: An aqueous cleaning composition containing sulfonic acids and a source of chloride ions is used to clean contaminants from EUV masks used in the manufacture of semiconductors. Optionally, the aqueous cleaning composition can include oxidizing agents and surfactants. The aqueous cleaning composition removes tin and other contaminants from the mask. Such other contaminants include, but are not limited to, aluminum oxide, and etch and photoresist residues.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for removing contaminants from an EUV mask using an aqueous solution containing sulfonic acid and chloride ions. More specifically, the present invention relates to a method for removing contaminants from an EUV mask using an aqueous solution containing sulfonic acid and chloride ions, wherein at least one of the contaminants removed from the EUV mask is tin. [Background technology]

[0002] Extreme ultraviolet (EUV) photolithography is an advanced lithography technique for semiconductor manufacturing. EUV light can be generated from tin plasma produced by a laser. To ensure high power output of 13.5 nm, i.e., light sources exceeding 200 watts, for high-volume semiconductor manufacturing (HVM), a double-laser pulse shooting method has been developed for higher tin ionization rates and higher conversion efficiency. In semiconductor manufacturing, several measures have been developed to prevent tin from contaminating critical components and optical components, but conventional means of periodic maintenance (PM) are still necessary for stable power handling and to prevent pattern defects.

[0003] Pellicles, or protective films, for EUV masks appeared relatively late compared to HVM. Without a pellicle, contaminants such as environmental particles, alumina (Al2O3) particles, and tin can contaminate the EUV mask, thus potentially causing defects. To address contamination issues, EUV masks need to be cleaned regularly during the lithography process. A standard cleaning composition for removing contaminants from EUV masks is an aqueous mixture of sulfuric acid and hydrogen peroxide (SPM). However, SPM causes significant limiting dimensional (CD) loss of the tantalum (Ta)-based absorber and anti-reflective coating (ARC) of the EUV mask after about 30 cleaning runs. In addition to the CD loss of the Ta-based absorber and ARC, SPM has shown insufficient cleaning performance for removing tin from EUV masks. [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Therefore, the semiconductor manufacturing industry needs new compositions and methods for cleaning EUV masks, particularly for removing tin from EUV masks. [Means for solving the problem]

[0005] The present invention is a method for removing contaminants from an extreme ultraviolet mask, a) A process of inspecting the extreme ultraviolet mask for contaminants, b) Water, sulfonic acid or its salt, chloride ions of A step of providing an aqueous cleaning composition comprising a source, optionally an oxidizing agent, and optionally a surfactant, c) A step of contacting the extreme ultraviolet mask with an aqueous cleaning composition to remove at least tin from the extreme ultraviolet mask. Regarding methods including

[0006] The present invention is a method for removing contaminants from an extreme ultraviolet mask, a) A process of inspecting the extreme ultraviolet mask for contaminants, b) Water, chloride ions of Source, formula: RS(=O)2-OH (I) (In the formula, R is an alkyl or aryl group.) A step of providing an aqueous cleaning composition comprising a sulfonic acid or a salt thereof having, optionally an oxidizing agent and optionally a surfactant, c) A step of contacting the extreme ultraviolet mask with an aqueous cleaning composition to remove at least tin from the extreme ultraviolet mask. Further details regarding methods including

[0007] The method and cleaning composition of the present invention enable the removal of at least tin and other contaminants from EUV masks, such as alumina, etching residues, and photoresist residues, which are commonly found on EUV masks in semiconductor manufacturing, for example, but are not limited to these. Compared with many conventional cleaning compositions and processes for EUV masks, the method and cleaning composition of the present invention also substantially reduce or prevent damage to structural components of the EUV mask, such as the capping layer and ARC, for example, but are not limited to these. Further advantages and improvements of the present invention can be understood by those skilled in the art by reading the specification and examples of this application. [Brief explanation of the drawing]

[0008] [Figure 1] The present invention illustrates various structural components of an EUV mask and the application of EUV light at a principal ray angle of 6° to the surface of the EUV mask. [Modes for carrying out the invention]

[0009] As used herein, abbreviations have the following meanings unless the context explicitly indicates otherwise: °C = °C, nm = nanometer, μg = microgram, Å = angstrom, min = minute, DI = deionization, UV = ultraviolet light, EUV = extreme ultraviolet light, EUVL = extreme ultraviolet lithography, ML = multilayer, ARC = anti-reflective coating or layer, LTEM = low thermal expansion material, CVD = chemical vapor deposition, PVD = physical vapor deposition, PEB = post-exposure bake, SPM = sulfuric acid + hydrogen peroxide mixture, IC = integrated circuit, e-beam (electron beam), AFM = atomic force microscope, Temp = temperature, Al = aluminum, Cu = copper, C = carbon, S = sulfur, O = oxygen, H = hydrogen, Ru = ruthenium, Ta = tantalum, Ti = titanium, B = boron, Cr = chromium, N = nitrogen, Mo = molybdenum, Si = silicon, K + = Potassium cation, Na +=Sodium cation, Al2O3=Aluminum oxide, HCl=Hydrogen chloride, Nd=Neodymium, YAG=Yttrium-aluminum garnet, e-Chuck=Electrostatic chuck, POB=Projection optics component box, NA=Numerical aperture, ER=Etching rate, Ex=Example, MSA=Methanesulfonic acid, XPS=X-ray photoelectron spectrometer, ICP-MS=Inductively coupled plasma mass spectrometry, ND=No damage, wt%=Weight percent.

[0010] The term “adjacent” means that two metal layers are in direct contact such that they have a common interface. The term “aqueous” means water or an aqueous system. The terms “composition” and “solution” are used interchangeably throughout this specification. The terms “EUV mask” and “mask” are used interchangeably throughout this specification. The terms “resist” and “photoresist” are used interchangeably throughout this specification. The term “numerical aperture” is a physical indicator of an optical component. Unless otherwise specified, amounts in percent are weight percent. The terms “one (a)” and “one (an)” can refer to both singular and plural throughout this specification. All numerical ranges are inclusive and can be combined in any order, except where it is logical to restrict such numerical ranges to sum to 100%.

[0011] EUVL is a promising patterning technique for semiconductor technology nodes in the nanometer range, such as 14 nm and below. Like photolithography, EUVL requires a photomask to print on the wafer, but it differs in that it uses light in the EUV region in the range of approximately 1 nm to 100 nm. Preferably, the light used in the EUVL process is around 13.5 nm. At a wavelength of 13.5 nm, many materials are highly absorbent. Therefore, reflective optical components, rather than refractive optical components, are generally used in EUVL. During the EUVL process, the EUV mask must be kept as clean as possible to avoid contamination and defects in the circuits formed on the semiconductor substrate and optical components used in the lithography process.

[0012] The present invention includes providing an EUV mask. The EUV mask is used to manufacture semiconductor wafers during a lithography exposure process. The EUV mask includes a substrate and a pattern formed thereon or on the substrate. The pattern is defined according to the circuit design. On the back side of the substrate is a conductive layer intended for electrostatic chucking. In the present invention, the mask is a reflective mask used in extreme ultraviolet lithography. An exemplary reflective mask 100 is shown in the cross-sectional view. The reflective mask 100 includes a substrate 102, a reflective ML 104 deposited on the substrate 102, a capping layer 106 deposited on the reflective ML 104, and a patterned absorption layer 108 deposited on the capping layer 106. The mask typically further includes a conductive layer 110 on the back side of the substrate, which is made of CrN or another conductive material. The ARC 112 is adjacent to the absorption layer 108. The ARC material includes, but is not limited to, tantalum boron oxide (TaBO). ARC allows for better visualization of images with any defects by reducing the intensity of the chemical light used for inspection.

[0013] The substrate 102 includes LTEM. The substrate 102 helps to minimize image distortion due to mask heating by enhanced illumination radiation. The LTEM can include fused silica, fused quartz, calcium fluoride, silicon carbide, silicon oxide - titanium oxide alloy, or other suitable LTEM known in the art. The substrate 102 includes a material with a low defect level and a smooth surface. The reflective ML 104 is deposited on the substrate 102 by a conventional process known in the art, such as by CVD or PVD. According to Fresnel's equation, light reflection occurs when light propagates across the interface between two materials with different refractive indices. The greater the difference in refractive indices, the greater the reflected light. To increase the reflected light, the number of interfaces can also be increased by depositing the reflective ML 104 of alternating materials, and by selecting appropriate thicknesses for each layer of the reflective ML 104, the light reflected from different interfaces can be constructively interfered. However, the absorption of the reflective ML 104 limits the highest achievable reflectivity. The reflective ML 104 includes a plurality of film pairs, such as pairs of molybdenum - silicon (Mo / Si) films (e.g., molybdenum layers above or below the silicon layers in each film pair). Instead, the reflective ML 104 can include pairs of molybdenum - beryllium (Mo / Be) films, or any material highly reflective at EUV wavelengths can be utilized for the reflective ML 104. The thickness of each layer of the reflective ML 104 depends on the EUV wavelength and the angle of incidence. The thickness of the reflective ML 104 is adjusted to achieve maximum constructive interference of the EUV light reflected at each interface and minimum absorption of the EUV light by the reflective ML 104. The reflective ML 104 can be selected to provide a high reflectivity for the selected radiation type / wavelength. The typical number of film pairs is between 20 and 80, but any number of film pairs can be used. In some embodiments, the reflective ML 104 includes 40 pairs of Mo / Si layers. In one example, each pair of Mo / Si films has a thickness of about 7 nm, and the total thickness is 280 nm, thereby achieving a reflectivity of about 70%.

[0014] The capping layer 106 is deposited on the reflective ML 104 by a conventional CVD or PVD process well known in the art. Because the capping layer 106 has different etching properties from the absorption layer, the capping layer 106 functions as an etching stop layer in the subsequent patterning or repair process of the absorption layer. The capping layer 106 contains Ru or, instead, a Ru compound such as ruthenium-boron (RuB) or ruthenium-silicon (RuSi).

[0015] The absorption layer 108 is also deposited on the capping layer 106 by a conventional CVD or PVD process and then patterned using a conventional imaging process to form a major pattern according to the IC design layout. In some embodiments, the absorption layer 108 absorbs the radiation beam projected onto it, as shown in the figure. The absorption layer 108 may include one or more layers from the group of suitable materials such as tantalum boronitride (TaBN), chromium (Cr), chromium oxide (CrO), titanium nitride (TiN), tantalum nitride (TaN), tantalum (Ta), titanium (Ti), or aluminum-copper (Al-Cu), palladium, aluminum oxide (AlO), molybdenum (Mo), or other suitable materials. Preferably, the absorption layer is TaBN. Patterning of the absorption layer 108 includes etching using a lithography patterning process and conventional processes known in the art. The lithography patterning process further includes the steps of forming an EUV-sensitive resist layer by spin-on coating, exposing the resist layer using an electron beam in an appropriate mode such as direct electron beam writing, and developing the exposed resist layer to form a patterned resist layer containing a plurality of openings that define a circuit pattern. The lithography patterning process may include other operations such as PEB. The etching process is applied to the absorption layer 108 through the openings in the patterned resist layer, and the absorption layer 108 is patterned using the patterned resist layer as an etching mask. The patterned resist layer is then removed by plasma ashing or wet exfoliation. The resist material may be a positive or negative photoresist. Photoresists are well known in the art. The present invention can be carried out using conventional photoresists.

[0016] Mask 100 is used in the lithography exposure process when patterning a semiconductor wafer. As shown in the figure, when the illumination beam 114 of EUV light generated from a tin plasma is projected onto the mask 100, a part of the illumination beam 114 projected onto the absorption layer 108 is absorbed by the absorption layer 108, and another part of the illumination beam 114 projected onto the reflective ML 104 is reflected by the reflective ML 104. The solid line indicates the EUV light beam focused on the EUV mask. The dotted line indicates the direction of the light beam. Thereby, a patterned illumination beam is generated. The light beam is generated by a conventional EUV light generator equipped with a Nd:YAG laser and a carbon dioxide laser. The highest performance of the light incident angle is an incident light angle of 6° with high reflectivity and low light diffraction in the current NA = 0.33 EUV lithography scanner. The patterned illumination beam is used to expose a resist film coated on a semiconductor wafer. Preferably, the illumination beam is generated from a tin plasma generated by a laser. During subsequent additional lithography operations such as PEB and development, a resist pattern is formed on the wafer and can be used as an etching mask during the etching process or an implantation mask during ion implantation.

[0017] One problem that occurs when using reflective EUV lithography technology is when defects appear inside or on the reflective EUV mask. When using a transmissive mask, relatively small defects may not be significantly harmful, but due to various factors such as the reduction in the size of the features of the circuit pattern in the mask 100, the same defects may be critical when using a reflective EUV mask. Therefore, the quality or integrity of the corresponding exposed image is affected by the defects of the mask 100.

[0018] The method of the present invention preferably includes inspecting the mask 100 to identify one or more defects using mask inspection means such as optical inspection means, AFM or other suitable inspection means. A commercially available mask inspection means is the MATRICS® X800 from Lasertec Corporation. Bruker is a pioneering AFM supplier. Inspection of the mask 100 includes the steps of scanning the surface of the mask, locating defects in the mask, and determining the shape and size of the defects. There are two types of defects in the mask: hard defects and soft defects. Hard defects refer to defects that cannot be removed by the cleaning process. Therefore, the present invention focuses on removing soft defects.

[0019] Soft defects refer to defects that can be removed by the cleaning process of the present invention, including but not limited to particles, tin, aluminum oxide, and resist residues. The method of the present invention is particularly effective in removing tin from an EUV mask without substantially damaging the tantalum-based components of the mask, preferably including ruthenium and ruthenium-based compounds, such as components of the ARC and absorption layer and the capping layer. Tin contaminants on the mask are typically generated during the application of laser-generated tin plasma, as described above. The figure shows an exemplary soft defect 116 formed in the capping layer 106, in which case the capping layer contains Ru.

[0020] This method proceeds by performing a cleaning process on the EUV mask, thereby removing soft defects. The cleaning process involves sulfonic acid or its salts and chloride ions. of The method involves applying an aqueous cleaning composition containing the source to an EUV mask, such as the EUV mask 100 shown in the figure. The pH of the aqueous cleaning composition is less than 1.

[0021] Preferably, the sulfonic acid in the cleaning composition of the present invention is of formula: RS(=O)2-OH (I) (In the formula, R is an organic group selected from the group consisting of alkyl and aryl groups.) It has. The alkyl group has the general formula: C n H 2n+1 (wherein the formula, the variable n is an integer of 1 or more, preferably an integer from 1 to 4, more preferably an integer from 1 to 3, and most preferably n is 1 or 2). Preferably, R is selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl and isobutyl, more preferably R is selected from the group consisting of methyl, ethyl, propyl and isopropyl, and most preferably R is selected from the group consisting of methyl and ethyl. More preferred examples of alkyl sulfonic acids are methanesulfonic acid, ethanesulfonic acid and propanesulfonic acid and their salts. Most preferred examples are methanesulfonic acid and ethanesulfonic acid and their salts, with methanesulfonic acid and its salts being preferred over ethanesulfonic acid and its salts.

[0022] The aryl group of R includes, but is not limited to, substituted or unsubstituted benzene or benzyl groups. Substituents include, but are not limited to, hydroxyl, C1-C3 hydroxyalkyl, C1-C3 alkoxy, and C1-C3 alkyl groups. Preferably, R is selected from the group consisting of benzene, hydroxybenzene, and tolyl, and more preferably, R is selected from the group consisting of benzene and hydroxybenzene. Preferred examples of aryl sulfonic acids are benzenesulfonic acid, 4-hydroxybenzenesulfonic acid, and toluenesulfonic acid, most preferably p-toluenesulfonic acid.

[0023] Salts of sulfonic acid may also be included in the cleaning composition of the present invention. The salts can be used alone or, preferably, in combination with one or more of the above-mentioned sulfonic acids. The general formula for a salt of sulfonic acid is: RS(=O)2-O - Y + (II) (In the formula, R is defined above, and Y + (This is a counter-cation for neutralizing the sulfonate anion.) It has Y. Preferably, +is K + or Na + and more preferably, Y + is K + Examples of preferred sulfonates are potassium methanesulfonate, sodium methanesulfonate and sodium ethanesulfonate. More preferably, the sulfonate is potassium methanesulfonate and sodium methanesulfonate.

[0024] Preferably, in the aqueous cleaning composition of the present invention, the above alkylsulfonic acid, these salts or mixtures thereof are included in the aqueous cleaning composition. Preferred alkylsulfonic acids are methanesulfonic acid and ethanesulfonic acid and their K + or Na + salts selected from the group consisting of. Most preferred are methanesulfonic acid and its K + and Na + salts.

[0025] In order to remove contaminants from the EUV mask without substantially damaging mask components such as ARC, capping layer, absorption layer, ML and LTEM layers, especially components containing Ta and Ru compounds, a sufficient amount of one or more of sulfonic acid and its salts is included in the aqueous cleaning composition of the present invention. Preferably, a sufficient amount of sulfonic acid and its salts is included in the aqueous cleaning composition of the present invention to remove at least Sn ions from the EUV mask. Other contaminants that can be removed from EUV mask components using the cleaning composition of the present invention include, but are not limited to, Al2O3, resists such as photoresist, and particles such as etching residues and environmental particles. Preferably, the sulfonic acid and its salts are included in the aqueous cleaning composition in an amount of at least 10% by weight, preferably at least 15% by weight, more preferably 15 - 65% by weight, and most preferably 40 - 65% by weight.

[0026] The aqueous cleaning composition of the present invention also contains chloride ions. A water-soluble compound that provides chloride ions and does not substantially contaminate the EUV mask ofIt can be used as a source. Preferably, HCl is chloride ions. of It is the source.

[0027] Preferably, one or more chloride ions of The source is contained in the aqueous cleaning composition and provides at least 0.05% by weight of chloride ions. More preferably, one or more chloride ions. of The source is contained in the aqueous cleaning composition and provides 0.1 to 5% by weight of chloride ions, most preferably one or more chloride ions. of The source is included in the cleaning composition of the present invention, providing 0.1 to 2% by weight of chloride ions.

[0028] Optionally, the aqueous cleaning composition may contain an oxidizing agent. Conventional oxidizing agents can be used. Such oxidizing agents include, but are not limited to, hydrogen peroxide, peroxydisulfuric acid, peroxymonosulfuric acid, and perchloric acid. Preferably, the oxidizing agent is hydrogen peroxide. In the aqueous cleaning composition of the present invention, the oxidizing agent may be included in an amount of 0.5 to 5 g / 100 g, preferably 0.5 to 2 g / 100 g of the aqueous cleaning composition.

[0029] Optionally, the aqueous cleaning composition may contain a surfactant. Such surfactants include nonionic surfactants, cationic surfactants, anionic surfactants, and amphoteric surfactants. Preferably, the surfactant is non-foaming. More preferably, the surfactant is an anionic surfactant. Most preferably, the surfactant is a non-foaming anionic surfactant such as dodecyldiphenyloxide disulfonic acid, which is commercially available from Pilot Chemical Corp. as CALFAX® DBA-70. The surfactant may be included in conventional amounts.

[0030] Preferably, the aqueous cleaning composition of the present invention comprises one or more sulfonic acids and their salts, and one or more chloride ions to provide chloride ions to the cleaning composition. ofThe mixture consists of a source, optionally an oxidizing agent, optionally a surfactant, and water. Preferably, the sulfonic acid is a sulfonic acid having formula (I) above, and its salt has formula (II) above. Preferably, chloride ions. of The source is HCl.

[0031] More preferably, the aqueous cleaning composition of the present invention comprises 15 to 65% by weight of methanesulfonic acid or a salt thereof, 0.1 to 5% by weight of chloride ions, and water.

[0032] Most preferably, the aqueous cleaning composition of the present invention comprises 40 to 65% by weight of methanesulfonic acid or a salt thereof, and 0.1 to 2% by weight of chloride ions (where, chloride ions of It consists of HCl (the source) and water.

[0033] Optionally, the method of the present invention may include an additional inspection step to further verify whether the EUV mask has been cleaned to meet the mask specifications for semiconductor manufacturing. If further cleaning is required, the mask cleaning method described above can be repeated. The cleaning method can be repeated as many times as necessary to achieve the desired cleanliness of the EUV mask.

[0034] The aqueous cleaning composition of the present invention can be applied to EUV masks for cleaning by conventional methods known in the art. The EUV mask can be immersed in the cleaning composition for a time sufficient to remove contaminants from the mask. Optionally, the mask can then be rinsed with water. Alternatively, the cleaning composition can be sprayed onto the mask, followed by rinsing with water. An example of a commercially available cleaning method is Mask Track Pro from SUSS MicroTec Inc.

[0035] The cleaning composition of the present invention is preferably used at a temperature of at least 30°C, more preferably 50-85°C, and most preferably 55-80°C.

[0036] The required exposure time of an EUV mask to the aqueous cleaning composition of the present invention may vary depending on the contaminants or defects in the mask and the location of the contaminants, such as the material composition of the ARC, absorption layer or capping layer, and contaminated layer. For example, tin is the most difficult to remove from an EUV mask. Removing photoresist contaminants from the mask may also be difficult due to variations in the composition of the photoresist. Generally, the EUV mask is exposed to the cleaning composition for at least 1 minute, or 5-30 minutes, or 5-10 minutes. Particularly difficult-to-remove contaminants, such as tin, may require multiple cleaning cycles, in which case each cleaning cycle may vary over time. The amount of removed contaminants can be measured by any suitable process and apparatus known in the art. An example of a process for measuring contaminants, particularly tin, is ICP-MS.

[0037] During lithography exposure processes that use masks to pattern semiconductor wafers, the masks can easily become contaminated, requiring multiple cleanings during the lithography process. Preferably, EUV masks are cleaned at the end of the lithography process after a significant amount of contaminants have accumulated in one or more layers of the EUV mask.

[0038] Specific processes, materials, and equipment may vary in the manufacturing of lithographic semiconductor wafers. Generally, this method begins with placing a mask into a lithography system. Preferably, the lithography system is an EUV lithography system designed to expose a resist layer with EUV light. The resist layer is a material sensitive to EUV light, such as a negative or positive photoresist. The EUV lithography system includes a radiation source for generating EUV light, such as EUV light having wavelengths in the range of about 1 nm to about 100 nm. For example, the radiation source generates EUV light with wavelengths centered around about 13.5 nm. An example of a commonly used radiation source is a Sn plasma generated by a laser. Such a Sn plasma generates Sn ions, which often contaminate the EUV mask with Sn, as mentioned above. The lithography system also includes an illuminator. In various embodiments, the illuminator includes various reflective optical components, such as a mirror system with a single mirror or multiple mirrors, to direct light from the radiation source onto the mask stage. A lithography system includes a mask stage configured to hold a mask in place. In some embodiments, the mask stage includes an electrostatic chuck for holding the mask in place. The lithography system also includes a projection optics module or POB for imaging the pattern of the mask onto a semiconductor substrate fixed to a substrate stage of the lithography system. The POB has reflective optics for projecting EUV light. The EUV light carrying the image of the defined pattern on the mask is directed away from the mask and collected by the POB. The illuminator and POB are collectively referred to as the optical module of the lithography system. The lithography system also includes a substrate stage for fixing the semiconductor substrate.

[0039] The semiconductor wafer is coated with a resist layer sensitive to EUV beams. The wafer may be a silicon wafer or may instead contain additional semiconductor materials. Such additional semiconductor materials may include compound semiconductors containing germanium, silicon carbide, gallium arsenide, gallium phosphide, indium phosphide, indium arsenide, and indium antimonide, or alloy semiconductors containing SiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP, and GaInAsP.

[0040] In yet another alternative example, the semiconductor wafer includes a semiconductor on an insulator (SOI) structure. In other embodiments, the semiconductor wafer also includes one or more conductive or dielectric films. In some embodiments, the dielectric film may include silicon oxide, a high-k dielectric material film, or a combination of silicon oxide and a high-k dielectric material, and the conductive thin film for the gate electrode film may include doped polysilicon or a metal such as aluminum (Al), copper (Cu), tungsten (W), nickel (Ni), titanium (Ti), gold (Au), platinum (Pt), or alloys of these metals.

[0041] An example of an EUV lithography method involves performing a lithographic exposure process on a resist layer using an EUV mask in an EUV lithography system. In this method, the generated EUV radiation is irradiated onto the mask by an illuminator and further projected onto the resist layer coated on the wafer by a POB, thereby forming a latent image on the resist layer. In some embodiments, the lithographic exposure process is performed in scan mode. The resist layer can be removed by wet exfoliation or plasma ashing. [Examples]

[0042] The following embodiments are included to further illustrate the present invention, but are not intended to limit its scope.

[0043] Examples 1-6 Removal of tin particles from semiconductor wafers A water-based sulfonic acid cleaning composition was prepared as shown in Table 1 below. The pH of this cleaning composition was less than 1. Semiconductor wafers containing PVD tin particles were provided by Triomax Technology Co., Ltd. The wafers were cut into 2.8 cm × 2.8 cm coupons. The semiconductor wafers contained tin particles, as opposed to a uniform film of tin for reproducing tin in the EUV photomask after tin plasma deposition.

[0044] Next, a coupon of a semiconductor wafer containing tin particles was immersed in 100 g of the solution (weight of water + weight of component) disclosed in Table 1 below, at the time and temperature listed in Table 1. Because H2O2 is unstable when combined with other compounds, 0.5 g of 31% H2O2 was mixed with 99.5 g of the solution immediately before immersing the coupon in the washing solution. Then, each solution was analyzed by ICP-MS for dissolved tin ions.

[0045] [Table 1]

[0046] Examples 7-9 (Comparison) Removal of tin particles from semiconductor wafers As shown in Table 2 below, aqueous sulfonic acid cleaning compositions were prepared. The pH of these cleaning compositions was less than 1.

[0047] The procedure for determining the amount of tin removed from the semiconductor wafer coupon containing tin particles was repeated as disclosed in Examples 1 to 6 above, except that the aqueous sulfonic acid cleaning composition disclosed in Table 2 was used.

[0048] [Table 2]

[0049] ICP-MS analysis of tin ions in the solutions shown in Table 2 revealed a significant decrease in the amount of tin ions in the aqueous cleaning solutions, in contrast to the tin ions in the solutions of Examples 1-6. Aqueous sulfonic acid cleaning compositions containing a combination of MSA and HCl showed a significantly greater overall improvement in tin removal compared to aqueous cleaning compositions without the combination of MSA and HCl.

[0050] Examples 10-13 (comparative) Removal of tin particles from semiconductor wafers As shown in Table 3 below, aqueous sulfonic acid cleaning compositions were prepared. The pH of these cleaning compositions was less than 1.

[0051] The procedure for determining the amount of tin removed from the semiconductor wafer coupon containing tin particles was repeated as disclosed in Examples 1 to 6 above, except that the aqueous sulfonic acid cleaning composition disclosed in Table 3 was used.

[0052] [Table 3]

[0053] Replacing HCl with the organic acid citric acid significantly reduced the removal of tin from semiconductor wafer coupons, in contrast to the aqueous cleaning compositions containing MSA and HCl in Examples 1-6.

[0054] Examples 14-15 Removal of tin particles from semiconductor wafers Aqueous sulfonic acid and SPM cleaning compositions were prepared in deionized water. The pH of these cleaning compositions was less than 1. The SPM (sulfuric acid / peroxide mixture) consisted of 96% by weight sulfuric acid and 31% by weight hydrogen peroxide (volume ratio of 10:1).

[0055] The procedure for determining the amount of tin to be removed from the coupon of a semiconductor wafer containing tin particles was repeated as disclosed in Examples 1 to 6 above.

[0056] [Table 4]

[0057] Semiconductor wafer coupons containing tin particles were immersed in an aqueous cleaning solution for 0.5 minutes or 1 minute. During immersion, the solution temperature was 80°C. The amount of tin removed from the coupons is shown in Table 5 below.

[0058] [Table 5]

[0059] The results in Table 5 show that the aqueous cleaning solution of the present invention improved tin removal compared to conventional SPM cleaning compositions.

[0060] Examples 16-17 Damage to TaBo and Ru Aqueous sulfonic acid and SPM cleaning compositions were prepared in deionized water. The pH of these cleaning compositions was less than 1. The SPM (sulfuric acid / peroxide mixture) consisted of 96% by weight sulfuric acid and 31% by weight hydrogen peroxide (volume ratio of 10:1).

[0061] Three EUV photomask substrates containing uniform films of Ru with a thickness of 3.5 nm and TaBO with a thickness of 2 nm were obtained from Toppan photomask Inc. Each EUV photomask substrate was cut into 3 cm x 3 cm coupons. The coupons were immersed in two aqueous cleaning compositions and SPM disclosed in Table 6 at 80°C for 1 minute. After 1 minute, the coupons were removed, and the concentrations of Ru and TaBO in the cleaning aqueous solutions were measured using ICP-MS.

[0062] [Table 6]

[0063] The etching rates of Ru and TaBO were determined using the following formulas. ER(Å / min)=c(ppb)×w(g) / D(g / cm 3 ) × A (cm 2 )×t(min)×10, formula (I) In the formula, c is the concentration of Ru or TaBO in the solution, w is the weight of the washing solution, A is the area of ​​the coupon, t is the time the coupon was immersed in the washing solution, and D is the density of Ru or TaBO. The density of Ru is 12.45 g / cm³. 3 Therefore, the density of TaBO is 14.3 g / cm³. 3 That is the case.

[0064] [Table 7]

[0065] Although SPM did not show any detectable Ru in the solution, Examples 16 and 17 still showed very low Ru etching rates, indicating that the MSA-containing solution caused slight damage to the Ru film.

[0066] SPM showed minimal damage to the TaBO film, but the MSA-containing solution still caused slight damage to the TaBO film.

[0067] Examples 18-22 Removal of Al2O3 from silicon wafers As shown in Table 8, aqueous sulfonic acid cleaning compositions were prepared. The pH of these cleaning compositions was less than 1.

[0068] A silicon wafer coated with a thick 2,000 Å alumina film was immersed in the cleaning solution disclosed in Table 8 for 10 minutes. The wafer was removed, and the thickness of the alumina film was measured by XPS. The etching rate was determined using equation (II), where h0 is the film thickness before immersion, h is the film thickness after immersion, and t is the immersion time in minutes. ER(Å / min)=h0-h / t Formula (II)

[0069] [Table 8]

[0070] Examples 21 and 22, which are the cleaning solutions of the present invention, showed the highest ER ratio for alumina.

[0071] Examples 23-24 (comparison) Conventional tin etching removal formulation As shown in Table 9, aqueous sulfonic acid cleaning compositions were prepared. The pH of these cleaning compositions was less than 1. Aqueous cleaning compositions were conventional cleaning compositions used to remove tin from printed circuit boards. However, upon preparation of the solutions, it was found that they were non-uniform and unsuitable for cleaning semiconductor wafers. Insoluble residues were observed to precipitate from the solutions.

[0072] [Table 9]

[0073] Examples 25-30 Removal of tin particles from semiconductor wafers As shown in Table 10 below, aqueous sulfonic acid cleaning compositions were prepared. The pH of these cleaning compositions was less than 1. Semiconductor wafers containing PVD tin particles were provided by Triomax Technology Co., Ltd. The wafers were cut into 2.8 cm × 2.8 cm coupons. The semiconductor wafers contained tin particles, as opposed to a uniform film of tin for reproducing tin in the EUV photomask after tin plasma deposition.

[0074] Next, a coupon of a semiconductor wafer containing tin particles was immersed in 100 g of the solution (weight of water + weight of component) disclosed in Table 10 below, at the time and temperature listed in Table 10. Because H2O2 is unstable when combined with other compounds, 1 g of 31% H2O2 was mixed with 99 g of the solution immediately before immersing the coupon in the washing solution. Then, each solution was analyzed by ICP-MS for dissolved tin ions.

[0075] [Table 10]

[0076] The aqueous sulfonic acid cleaning compositions of Examples 25-30 were uniform and stable, and showed good tin removal in contrast to the non-uniform comparative examples 23-24 described above. [Explanation of Symbols]

[0077] 100 Reflective Masks 102 circuit boards 104 Reflective ML 106 Capping layer 108 Absorption layer 110 Conductive layer 112 ARC 114 Illumination beams 116 Software defects

Claims

1. A method for removing contaminants from an extreme ultraviolet mask, a) A step of inspecting the extreme ultraviolet mask for contaminants, b) A step of providing an aqueous cleaning composition comprising water, sulfonic acid or a salt thereof, a source of chloride ions, and an oxidizing agent, c) A step of contacting the extreme ultraviolet mask with the aqueous cleaning composition containing sulfonic acid and a source of chloride ions to remove at least tin from the extreme ultraviolet mask. A method that includes this.

2. The aforementioned sulfonic acid is given by formula: R-S(=O) 2 -OH (I) (In the formula, R is an alkyl or aryl group.) The method according to claim 1, comprising:

3. R is C n H 2n+1 The method according to claim 2, wherein the variable n is an integer of 1 or more.

4. R is C n H 2n+1 The method according to claim 3, wherein the variable n is an integer from 1 to 4.

5. The method according to claim 1, wherein the sulfonic acid is in an amount of at least 10% by weight.

6. The method according to claim 5, wherein the sulfonic acid is in an amount of 15 to 65% by weight.

7. The method according to claim 1, wherein the chloride ions are present in an amount of at least 0.05% by weight.

8. The method according to claim 7, wherein the chloride ions are present in an amount of at least 0.1 to 5% by weight.

9. The salt of the aforementioned sulfonic acid is given by formula: 2)(#) 2  - ﹹ + (=) (wherein, R is an alkyl or aryl group, and Y + is a counter cation) The method according to claim 1, comprising:

10. The method according to claim 1, wherein the aqueous cleaning composition is at least 30°C.

11. The method according to claim 10, wherein the aqueous cleaning composition is 50 to 85°C.

12. The method according to claim 1, further comprising a surfactant in the aqueous cleaning composition.

13. A method for removing contaminants from an extreme ultraviolet mask, a) A step of inspecting the extreme ultraviolet mask for contaminants, b) Water, source of chloride ions, formula: R-S(=O) 2 -OH (I) (In the formula, R is an alkyl or aryl group.) A step of providing an aqueous cleaning composition comprising a sulfonic acid or a salt thereof having and an oxidizing agent, c) A step of bringing the extreme ultraviolet mask into contact with the aqueous cleaning composition to remove at least tin from the extreme ultraviolet mask. A method that includes this.

14. The method according to claim 13, wherein the aqueous cleaning composition further contains a surfactant.