Method of removing contaminants from EUV masks

Abstract

An aqueous cleaning composition containing sulfonic acid and chloride ion sources is used to clean contaminants from EUV photomasks used in semiconductor manufacturing. Depending on the requirements, the aqueous cleaning composition may include oxidants and surfactants. The aqueous cleaning composition removes tin and other contaminants from the photomask. These other contaminants include, but are not limited to, aluminum oxide, etching, and photoresist residues.

Description

Technical Field

[0001] This invention relates to a method for removing contaminants from an EUV photomask using an aqueous solution containing sulfonic acid and chloride ions. More specifically, this invention relates to a method for removing contaminants from an EUV photomask using an aqueous solution containing sulfonic acid and chloride ions, wherein at least one of the contaminants removed from the EUV photomask is tin. Prior Technology

[0002] Extreme ultraviolet (EUV) lithography is an advanced lithography technique used in semiconductor manufacturing. EUV light can be generated by tin plasma produced by a laser. A dual-laser pulse emission scheme has been developed to achieve higher tin ionization rates and higher conversion efficiency, ensuring a high-power (greater than 200 watts) light source for 13.5nm high-volume semiconductor manufacturing (HVM). Although measures have been implemented to prevent tin contamination of critical components and optics in semiconductor manufacturing, standard tools for periodic maintenance (PM) are still required to achieve stable power delivery and prevent patterning failures.

[0003] Pellicles, or protective films, used for EUV photomasks are a relatively recent development for HVM. Without these protective films, contaminants such as environmental particles, alumina (Al₂O₃) particles, and tin can contaminate the EUV photomask, leading to defects. Regular cleaning of the EUV photomask is necessary during the lithography process to address contamination. The standard cleaning composition for removing contaminants from EUV photomasks is an aqueous mixture of sulfuric acid and hydrogen peroxide (SPM). However, after approximately 30 cleaning runs, SPM causes significant critical size (CD) loss in the tantalum (Ta)-based absorber and antireflective coating (ARC) of the EUV photomask. In addition to the CD loss in the Ta-based absorber and ARC, SPM has shown insufficient cleaning performance for removing tin from EUV photomasks.

[0004] Therefore, the semiconductor manufacturing industry needs a new composition and method to clean EUV photomasks, especially to clean the tin in EUV photomasks. Summary of the Invention

[0005] This invention relates to a method for removing contaminants from an extreme ultraviolet (EUV) photomask, comprising: a) Inspect the extreme ultraviolet (EUV) photomask for contaminants; b) Provide an aqueous cleaning composition consisting of water, sulfonic acid or its salt, a chloride ion source, an oxidant as needed, and a surfactant as needed; and c) Contact the extreme ultraviolet photomask with an aqueous cleaning component to remove at least some tin from the extreme ultraviolet photomask.

[0006] The present invention further relates to a method for removing contaminants from an extreme ultraviolet photomask, comprising: a) Inspect the extreme ultraviolet (EUV) photomask for contaminants; b) Provide an aqueous cleaning composition consisting of water, a chloride ion source, a sulfonic acid or its salt having the following formula, an oxidant as needed, and a surfactant as needed: RS(=O)2-OH (I) Wherein R-series alkyl or aryl; and c) Contact the extreme ultraviolet photomask with an aqueous cleaning component to remove at least some tin from the extreme ultraviolet photomask.

[0007] The methods and cleaning compositions of this invention are capable of removing at least tin and other contaminants from EUV photomasks, such as, but not limited to, alumina, etching residues, and photoresist residues commonly found on EUV photomasks in semiconductor manufacturing. Compared to many conventional cleaning compositions and processes used for EUV photomasks, the methods and cleaning compositions of this invention also reduce or prevent substantial damage to EUV photomask structural components such as, but not limited to, the overlay and ARC. Other advantages and improvements of this invention will be understood by those skilled in the art through reading the specification and examples of this application. Simple Explanation of the Diagram

[0008] [Figure 1] illustrates the EUV photomask of the present invention, showing various structural components and EUV light applied to the surface of the EUV photomask at a principal ray angle of 6°. Implementation

[0009] As used throughout this instruction manual, unless the context clearly indicates otherwise, the abbreviations have the following meanings: °C = degrees Celsius; nm = nanometer; μg = microgram; Å = angstrom; min = minute; DI = deionized; UV = ultraviolet; EUV = extreme ultraviolet; EUVL = extreme ultraviolet lithography; ML = multilayer; ARC = anti-reflective coating or layer; LTM = low thermal expansion material; CVD = chemical vapor deposition; PVD = physical vapor deposition; PEB = post-exposure baking; SPM = sulfuric acid + hydrogen peroxide mixture; IC = integrated circuit; e-beam (electron beam); AFM = atomic force microscope. 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 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; and wt% = weight percent.

[0010] The term "adjacent" means direct contact that gives two metal layers a common interface. The term "aqueous" means water or water-based. Throughout this specification, 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. The term "numerical aperture" is an optical physical specification. Unless otherwise indicated, quantities expressed as % are by weight. Throughout this specification, the term "a / an" can refer to both the singular and plural. All numerical ranges are inclusive and can be combined in any order, except where it is logically possible to limit the numerical range to a maximum sum of 100%.

[0011] EUVL is a promising patterning technique for semiconductor technology nodes in the nanometer range, such as 14nm and smaller. Like optical lithography, EUVL requires a photomask to print on the wafer, but it uses light in the EUV region, ranging from about 1nm to about 100nm. Preferably, the light used in EUVL is around 13.5nm. At a wavelength of 13.5nm, many materials are highly absorbent. Therefore, reflective optics are typically used in EUVL rather than refractive optics. During EUVL processing, the EUV photomask should be kept as clean as possible to avoid contamination and defects in the circuitry formed on the semiconductor substrate and optics used in the lithography process.

[0012] The present invention relates to providing an EUV photomask. This EUV photomask is used in a photolithography process to manufacture semiconductor wafers. The EUV photomask includes a substrate and a pattern formed on or to be formed on the substrate. The pattern is defined according to a circuit design. A conductive layer for electrostatic adsorption is located on the back side of the substrate. In this invention, the photomask is a reflective photomask used for extreme ultraviolet lithography. [Figure 1] shows an example of a reflective light mask in a cross-sectional view.

[0100] Reflective mask

[0100] Includes a substrate

[0102] Deposited on the substrate

[0102] on the reflection ML

[0104] Deposited on reflective ML

[0104] Covering layer

[0106] and deposited in the overburden Patterned absorption layer on

[0106]

[0108] The photomask further includes a conductive layer located on the back side of a substrate typically made of CrN or other conductive materials.

[0110] ARC

[0112] Adjacent absorption layer

[0108] . ARC materials include, but are not limited to, tantalum boron oxide (TaBO). ARC can better visualize any defective images by reducing the intensity of the inspection photoluminescence.

[0013] base

[0102] Includes LTEM. Substrate

[0102] This is used to minimize image distortion caused by heating of the photomask due to enhanced illumination radiation. The LTEM may include fused silica, fused silica, calcium fluoride, silicon carbide, silicon oxide-titanium oxide alloy, or other suitable LTEMs known in the art. Substrate

[0102] Includes materials with low defect levels and smooth surfaces. Reflective ML

[0104] The substrate is deposited using conventional processes known in the art, such as CVD or PVD.

[0102] Above. According to Fresnel's equation, when light propagates through the interface between two materials with different refractive indices, light reflection occurs. The greater the difference in refractive index, the greater the reflected light. To increase reflected light, reflection can also be achieved by depositing alternating materials.

[0104] to increase the number of interfaces, and by providing reflection ML

[0104] Each layer is chosen with an appropriate thickness to allow constructive interference of light reflected from different interfaces. However, the reflection ML The absorption limit of

[0104] allows for the highest achievable reflectivity. Reflection ML

[0104] Includes multiple film pairs, such as molybdenum-silicon (Mo / Si) film pairs (e.g., in each film pair, a molybdenum layer is located above or below a silicon layer). Alternatively, reflective ML

[0104] It may include a molybdenum-beryllium (Mo / Be) film pair, or any material that is highly reflective at EUV wavelengths can be used to reflect ML.

[0104] . Reflection ML

[0104] The thickness of each layer depends on the EUV wavelength and the angle of incidence. Adjust the reflection ML

[0104] thickness to achieve maximum constructive interference and reflection ML of EUV light reflected at each interface.

[0104] Minimal absorption of EUV light. Reflection ML can be selected.

[0104] , which makes it provide high reflectivity for the selected radiation type / wavelength. The typical number of film pairs is 20-80, however, any number of film pairs can be used. In some embodiments, the reflectivity ML...

[0104] It includes forty pairs of Mo / Si layers. In one example, each Mo / Si film pair has a thickness of about 7 nm, and a total thickness of 280 nm, thus achieving a reflectivity of about 70%.

[0014] Cover layer

[0106] Deposited on reflective ML by conventional CVD or PVD processes well known in the art.

[0104] Above. Due to the covering layer

[0106] It has different etching characteristics from the absorption layer, therefore the capping layer

[0106] It acts as an etch barrier layer in subsequent patterning or repair processes of the absorbent layer.

[0106] Includes Ru or alternative Ru compounds, such as ruthenium-boron (RuB) or ruthenium-silicon (RuSi).

[0015] Absorption layer

[0108] The capping layer is also deposited using conventional CVD or PVD processes.

[0106] Then, a conventional imaging process is used to pattern the IC design layout to form the main pattern. In some embodiments, the absorption layer...

[0108] Absorbs the radiation beam projected onto it, such as As shown in Figure 1. Absorption layer

[0108] It may comprise a single layer or multiple layers from the group consisting of 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 absorber layer is TaBN. Absorber layer

[0108] The patterning includes a photolithographic patterning process and etching using conventional processes known in the art. The photolithographic patterning process further includes: forming an EUV light-sensitive resist layer by spin coating; writing the exposed resist layer using an electron beam in a suitable mode such as direct electron beam; and developing the exposed resist layer to form a patterned resist layer including a plurality of openings defining a circuit pattern. The photolithographic patterning process may include other operations, such as PEB. The patterning extends through the openings of the patterned resist layer into the absorption layer.

[0108] An etching process is applied to use a patterned resist layer as an etching mask to make the absorption layer

[0108] Patterning. The patterned resist layer is then removed by plasma ashing or wet stripping. The resist material can be a positive or negative photoresist. Photoresists are well known in the art. Conventional photoresists can be used to implement this invention.

[0016] When patterning a semiconductor wafer, the photomask

[0100] Used in photolithography exposure processes. For example... [Figure 1] shows the illumination beam of EUV light generated by tin plasma.

[0114] Projected onto the light shield

[0100] When projected onto the absorption layer The illumination beam on

[0108]

[0114] A portion of the absorbed layer

[0108] Absorption, while projection onto the reflective ML The illumination beam on

[0104] Another part of

[0114] was reflected by ML

[0104] Reflection. Solid lines represent EUV beams focused on an EUV photomask. Dashed lines represent beam direction. This produces a patterned illumination beam. The beam is generated by a conventional EUV light generator equipped with an Nd:YAG laser and a carbon dioxide laser. The optimal performance of the light incident angle is a 6° incident angle, which has high reflectivity and low light diffraction in current NA=0.33 EUV lithography scanners. The patterned illumination beam is used to expose the resist film coated on the semiconductor wafer. Preferably, the illumination beam is generated by laser-generated tin plasma. After subsequent additional lithography operations, such as PEB and development, the resist pattern is formed on the wafer and can be used as an etching photomask in the etching process or as an implantation photomask in the ion implantation process.

[0017] A challenge arises when defects occur in or on a reflective EUV lithography mask. While relatively small defects may not be significantly detrimental when using a transmissive mask, similar defects can become significant when using a reflective EUV mask due to various factors, such as the mask itself.

[0100] The feature size of the circuit pattern is reduced. Therefore, the quality or integrity of the corresponding exposed image is affected by the photomask. The impact of defects on

[0100] .

[0018] The preferred method of the present invention includes inspecting the photomask using a photomask inspection tool, such as an optical inspection tool, an AFM (Optical Frequency Imaging) or other suitable inspection tool.

[0100] To identify one or more defects. A commercially available photomask inspection tool is the MATRICS™ X800 from Lasertec Corporation. Bruker is a pioneer supplier of AFM. Inspecting the photomask.

[0100] This includes scanning the photomask surface, locating defects on the photomask, and determining the shape and size of the defects. Defects on the photomask include two types: hard defects and soft defects. Hard defects refer to defects that cannot be removed by a cleaning process. Therefore, this invention relates to the removal of soft defects.

[0019] Soft defects refer to defects that can be removed by the cleaning process of this invention, such as, but not limited to, particles, tin, aluminum oxide, and resist residues. The method of this invention is particularly effective for removing tin from EUV photomasks without substantially damaging the tantalum-based components of the photomask, such as, but not limited to, ARC and absorber layers, as well as components of the capping layer, preferably including ruthenium and ruthenium-based compounds. As mentioned above, tin contaminants on photomasks are typically generated during the application of tin plasma produced by laser. [Figure 1] illustrated on the cover layer

[0106] An example of a soft defect formed on the surface.

[0116] , where the overlay layer contains Ru.

[0020] This method removes soft defects by performing a cleaning process on the EUV photomask. The cleaning process involves applying an aqueous cleaning composition containing sulfonic acid or its salts and a chloride ion source to the EUV photomask, such as... [Figure 1] shows the EUV photomask

[0100] . The pH of the aqueous cleaning component is less than 1.

[0021] Preferably, the sulfonic acid in the cleaning composition of the present invention has the following formula: RS(=O)2-OH (I), R is selected from the group consisting of alkyl and aryl groups. The alkyl group has the general formula: CnH2n+1, where the variable n is an integer from 1 to a larger integer, 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, wherein methanesulfonic acid and its salts are preferred over ethanesulfonic acid and its salts.

[0022] The aryl group of R includes, but is not limited to, substituted or unsubstituted benzyl or benzyl groups. Substituent groups 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; more preferably, R is selected from the group consisting of benzene and hydroxybenzene. Examples of preferred aryl sulfonic acids are benzenesulfonic acid, 4-hydroxybenzenesulfonic acid, and toluenesulfonic acid, with p-toluenesulfonic acid being the most preferred.

[0023] Salts of sulfonic acids may also be included in the cleaning compositions of the present invention. These salts may be used alone, or preferably in combination with one or more of the aforementioned sulfonic acids. Salts of sulfonic acids have the general formula: RS(=O)2-O-Y+ (II), Wherein R is as defined above, and Y+ is the counter cation that neutralizes the sulfonate anion. Preferably, Y+ is K+ or Na+, and more preferably, Y+ is K+. Preferred examples of sulfonates are potassium methanesulfonate, sodium methanesulfonate, and sodium ethanesulfonate. More preferably, the sulfonates are potassium methanesulfonate and sodium methanesulfonate.

[0024] Preferably, in the aqueous cleaning composition of the present invention, the aforementioned alkyl sulfonic acid, its salt, or mixture thereof is included in the aqueous cleaning composition. Preferably, the alkyl sulfonic acid is selected from the group consisting of methanesulfonic acid and ethanesulfonic acid and their K+ or Na+ salts. Most preferably, it is methanesulfonic acid and its K+ and Na+ salts.

[0025] The aqueous cleaning composition of this invention contains sufficient amounts of one or more sulfonic acids and their salts to remove contaminants from EUV photomasks without causing substantial damage to photomask components such as ARC, capping layers, absorber layers, ML and LTM layers, especially components containing Ta and Ru compounds. Preferably, the aqueous cleaning composition of this invention contains sufficient amounts of sulfonic acids and their salts to remove at least Sn ions from EUV photomasks. Other contaminants that can be removed from EUV photomask components using the cleaning composition of this invention include, but are not limited to, Al2O3, resists such as photoresists, etching residues, and particles such as environmental particles. Preferably, the sulfonic acid and its salts are contained in the aqueous cleaning composition in an amount of at least 10 wt%, preferably at least 15 wt%, more preferably 15-65 wt%, and most preferably 40-65 wt%.

[0026] The aqueous cleaning composition of this invention also contains chloride ions. Water-soluble compounds that provide chloride ions and substantially do not contaminate the EUV photomask can be used as chloride ion sources. Preferably, HCl is a chloride ion source.

[0027] Preferably, the aqueous cleaning composition contains one or more chloride ion sources to provide at least 0.05 wt% chloride ions. More preferably, the aqueous cleaning composition contains one or more chloride ion sources to provide 0.1-5 wt% chloride ions. Most preferably, the cleaning composition of the present invention contains one or more chloride ion sources to provide 0.1-2 wt% chloride ions.

[0028] As needed, the aqueous cleaning composition may contain an oxidizing agent. Conventional oxidizing agents can be used. These oxidizing agents include, but are not limited to, hydrogen peroxide, persulfate, persulfate, and perchloric acid. Preferably, the oxidizing agent is hydrogen peroxide. The amount of oxidizing agent contained in the aqueous cleaning composition of the present invention may be 0.5-5 g / 100 g of the aqueous cleaning composition, preferably 0.5-2 g / 100 g of the aqueous cleaning composition.

[0029] As needed, aqueous cleaning components may contain surfactants. Such surfactants include nonionic, cationic, anionic, and amphoteric surfactants. Preferably, the surfactant is non-foaming. More preferably, the surfactant is anionic. Most preferably, the surfactant is a non-foaming anionic surfactant, such as dodecyl diphenyl ether disulfonic acid, 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, one or more chloride ion sources that provide chloride ions to the cleaning composition, an oxidant as needed, a surfactant as needed, and water. Preferably, the sulfonic acid is a sulfonic acid having the above formula (I) and its salt has the above formula (II). Preferably, the chloride ion source is HCl.

[0031] More preferably, the aqueous cleaning composition of the present invention consists of 15-65 wt% of methanesulfonic acid or its salt, 0.1-5 wt% of chloride ions and water.

[0032] Preferably, the aqueous cleaning composition of the present invention consists of 40-65 wt% of methanesulfonic acid or its salt, 0.1-2 wt% of chloride ions and water, wherein the chloride ion source is HCl.

[0033] If necessary, the method of this invention may include another inspection operation to further check 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 multiple times as needed to achieve the required cleanliness of the EUV mask.

[0034] The aqueous cleaning composition of this invention can be applied to EUV photomasks for cleaning using conventional methods known in the art. Sufficient time can be allowed to immerse the EUV photomask in the cleaning composition to remove contaminants. If necessary, the photomask can then be rinsed with water. Alternatively, the cleaning composition can be sprayed onto the photomask and then rinsed with water. An example of a commercial cleaning tool is the MaskTrack Pro from SUSS MicroTec Inc.

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

[0036] The sufficient exposure time of the EUV photomask to the aqueous cleaning composition of this invention can be varied depending on the contaminants or defects on the photomask, their location (e.g., on the ARC, absorber layer, or capping layer), and the material composition of the contaminant layer. For example, tin is the most difficult to remove from EUV photomasks. Removing photoresist contaminants from the photomask can also be challenging due to the different compositions of the photoresists. Generally, the EUV photomask is exposed to the cleaning composition for at least 1 minute, or, for example, 5-30 minutes, or, for example, 5-10 minutes. Contaminants that are particularly difficult to remove, such as tin, may require multiple cleaning runs or cycles, where the time of each cleaning cycle may vary. The amount of contaminants removed can be measured by any suitable process and equipment known in the art. An example of a process for measuring contaminants (especially tin) is ICP-MS.

[0037] In photolithography, a process that uses a photomask to pattern semiconductor wafers, the photomask can be easily contaminated, requiring multiple cleanings during the process. Preferably, the EUV photomask is cleaned at the end of the photolithography process after a significant amount of contaminants have accumulated on one or more layers.

[0038] The specific steps, materials, and equipment used in photolithography for semiconductor wafer fabrication can vary. Generally, the method begins with loading a photomask into a photolithography system. Preferably, the photolithography system is an EUV photolithography system, designed to expose a resist layer by means of EUV light. The resist layer is a material sensitive to EUV light, such as a negative or positive photoresist. The EUV photolithography system includes a radiation source for generating EUV light, such as EUV light having a wavelength in the range of about 1 nm to about 100 nm. For example, the radiation source generates EUV light with a wavelength centered at about 13.5 nm. An example of a commonly used radiation source is a laser generated by Sn plasma. This Sn plasma generates Sn ions, which typically cause the EUV photomask to become Sn-contaminated, as described above. The photolithography system also includes an illuminator. In various embodiments, the illuminator includes various reflective optics, such as a single mirror or a mirror system with multiple mirrors, to guide light from the radiation source onto the photomask stage. The photolithography system includes a photomask stage configured to hold the photomask. In some embodiments, the photomask stage includes an electrostatic chuck for holding the photomask. The lithography system also includes a projection optical module (POB) for imaging the pattern of the photomask onto a semiconductor substrate fixed to the substrate stage of the lithography system. The POB has reflective optics for projecting EUV light. EUV light carrying an image of the pattern defined on the photomask is guided from the photomask and collected by the POB. The illuminator and the POB are collectively referred to as the optical module of the lithography system. The lithography system also includes a substrate stage for holding the semiconductor substrate.

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

[0040] In another alternative, the semiconductor wafer includes a semiconductor-on-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 film, or a combination of silicon oxide and a high-k dielectric material, and the conductive film used for the gate electrode film may include doped polycrystalline silicon or metals such as aluminum (Al), copper (Cu), tungsten (W), nickel (Ni), titanium (Ti), gold (Au), platinum (Pt), or metal alloys thereof.

[0041] Examples of EUV lithography methods include performing photolithographic exposure processes on a resist layer using an EUV photomask in an EUV lithography system. In this method, the generated EUV radiation is irradiated onto the photomask by an illuminator and further projected onto the resist layer coated on the wafer by a POB (Polymer Optical Image Block), thereby forming a latent image on the resist layer. In some embodiments, the photolithographic exposure process is performed in a scanning mode. The resist layer can be removed by wet stripping or plasma ashing.

[0042] The following examples are included to further illustrate the invention, but are not intended to limit its scope. Examples 1 to 6 Removing tin particles from semiconductor wafers

[0043] The water-based sulfonic acid cleaning composition was prepared as shown in Table 1 below. The pH of the cleaning composition was less than 1. Semiconductor wafers containing PVD tin particles were provided by Triomax Technology Co., Ltd. The wafers were diced into 2.8cm × 2.8cm sample blocks. The semiconductor wafers included tin particles instead of a homogeneous tin film to simulate tin on an EUV photomask after tin plasma deposition.

[0044] The semiconductor wafer sample block containing tin particles was then immersed in 100g of the solutions disclosed in Table 1 (weight of water + weight of components), with the time and temperature listed in Table 1. Due to the instability of H2O2 when combined with other compounds, 0.5g of 31% H2O2 was mixed with 99.5g of the solution before immersing the sample block in the cleaning solution. The dissolved tin ions in each solution were then analyzed by ICP-MS. Examples 7 to 9 (Comparative Examples) Removing tin particles from semiconductor wafers

[0045] The water-based sulfonic acid cleaning composition was prepared as shown in Table 2 below. The pH of the cleaning composition was less than 1.

[0046] In addition to using the water-based sulfonic acid cleaning composition disclosed in Table 2, repeat the procedure for determining the amount of tin removed from the semiconductor wafer sample block containing tin particles, as disclosed in Examples 1 to 6 above.

[0047] Compared to the tin ion concentrations in the solutions of Examples 1 to 6, ICP-MS analysis of the tin ion concentrations in the solutions in Table 2 showed a significant reduction in the amount of tin ions in the aqueous cleaning solutions. The aqueous sulfonic acid cleaning composition containing the combination of MSA and HCl showed a significant overall improvement in tin removal compared to the aqueous cleaning composition without the MSA and HCl combination. Examples 10 to 13 (Comparative Examples) Removing tin particles from semiconductor wafers

[0048] The water-based sulfonic acid cleaning composition was prepared as shown in Table 3 below. The pH of the cleaning composition was less than 1.

[0049] In addition to using the water-based sulfonic acid cleaning composition disclosed in Table 3, repeat the procedure for determining the amount of tin removed from the semiconductor wafer sample block containing tin particles, as disclosed in Examples 1 to 6 above.

[0050] Compared to the aqueous cleaning compositions containing MSA and HCl in Examples 1 to 6, replacing HCl with the organic acid citric acid resulted in a significant reduction in the removal of tin from the semiconductor wafer sample block. Examples 14 to 15 Removing tin particles from semiconductor wafers

[0051] Aqueous sulfonic acid and SPM cleaning components were prepared in DI water. The cleaning components had a pH less than 1. The SPM (sulfuric acid / peroxide mixture) consisted of 96 wt% sulfuric acid and 31 wt% hydrogen peroxide (10:1 volume ratio).

[0052] The procedure for determining the amount of tin removed from a semiconductor wafer sample block containing tin particles is repeated as disclosed in Examples 1 to 6 above.

[0053] Semiconductor wafer sample blocks containing tin particles were immersed in an aqueous cleaning solution for 0.5 min or 1 min. The solution was kept at 80°C during immersion. The amount of tin removed from the sample blocks is shown in Table 5 below.

[0054] The results in Table 5 show that the aqueous cleaning solution of the present invention has improved tin removal compared with conventional SPM cleaning compositions. Examples 16 to 17 Damage to TaBo and Ru

[0055] Aqueous sulfonic acid and SPM cleaning components were prepared in DI water. The cleaning components had a pH less than 1. The SPM (sulfuric acid / peroxide mixture) consisted of 96 wt% sulfuric acid and 31 wt% hydrogen peroxide (10:1 volume ratio).

[0056] Three EUV photomask substrates, each containing a 3.5 nm thick Ru and a 2 nm thick TaBO homogeneous film, were obtained from Toppan Photomask Inc. Each EUV photomask substrate was cut into 3 cm × 3 cm sample blocks. The sample blocks were immersed at 80 °C in the two aqueous cleaning components disclosed in Table 6 and SPM for 1 min. After 1 min, the sample blocks were removed, and the concentrations of Ru and TaBO in the aqueous cleaning solutions were measured using ICP-MS.

[0057] The etching rates of Ru and TaBO are determined using the following formula: ER(Å / min)=c(ppb)xw(g) / D(g / cm3)x A(cm2)xt(min)x 10, formula (I), The concentrations of Ru or TaBO in the c-series solution, the weight of the w-series cleaning solution, the area of ​​the A-series sample block, the t-series sample block immersion time in the cleaning solution, and the densities of Ru or TaBO in the D-series are specified. The density of Ru is 12.45 g / cm³, and the density of TaBO is 14.3 g / cm³.

[0058] Although SPM did not show detectable Ru in solution, Examples 16 and 17 still showed very low Ru etch rates, indicating that the damage to the Ru film caused by the MSA-containing solution was not significant.

[0059] SPM showed minimal damage to the TaBO membrane, but the damage caused by the MSA-containing solution to the TaBO membrane was still not significant. Examples 18 to 22 Removal of Al2O3 from silicon wafers

[0060] The water-based sulfonic acid cleaning composition was prepared as shown in Table 8. The pH of the cleaning composition was less than 1.

[0061] A silicon wafer coated with a 2,000 Å thick alumina film was immersed in the cleaning solution disclosed in Table 8 for 10 min. The wafer was removed and the alumina film thickness was measured using XPS. The etching rate was determined by formula (II), where h0 is the film thickness before immersion and h is the film thickness after immersion. t is the immersion time in min. ER(Å / min) = h0 - h / t, Formula (II)

[0062] Examples 21 and 22 are cleaning solutions of the present invention, and Examples 21 and 22 have the highest alumina ER rate. Examples 23 to 24 (Comparative Examples) Conventional tin etching removal formula

[0063] The aqueous sulfonic acid cleaning compositions were prepared as shown in Table 9. The pH of the cleaning compositions was less than 1. These aqueous cleaning compositions are conventional cleaning compositions used for stripping tin from printed circuit boards. However, during solution preparation, they were found to be heterogeneous and unsuitable for cleaning semiconductor wafers. Insoluble residues were observed precipitating from the solution. Examples 25 to 30 Removing tin particles from semiconductor wafers

[0064] The water-based sulfonic acid cleaning composition was prepared as shown in Table 10 below. The pH of the cleaning composition was less than 1. The semiconductor wafer containing PVD tin particles was provided by Taiyuan Technology Co., Ltd. The wafer was cut into sample blocks of 2.8cm × 2.8cm. The semiconductor wafer included tin particles instead of a homogeneous tin film to simulate tin on the EUV photomask after tin plasma deposition.

[0065] The semiconductor wafer sample block containing tin particles was then immersed in 100g of the solution (weight of water + weight of components) disclosed in Table 10, with the time and temperature listed in Table 10. Due to the instability of H2O2 when combined with other compounds, 1g of 31% H2O2 was mixed with 99g of solution just before immersing the sample block in the cleaning solution. The dissolved tin ions in each solution were then analyzed by ICP-MS.

[0066] The aqueous sulfonic acid cleaning compositions of Examples 25 to 30 are homogeneous and stable, and show good tin removal compared to the heterogeneous comparative Examples 23 to 24 above. 100: Light Mask 102: Base 104: Reflection ML 106: Overlay 108: Absorption Layer 112:ARC 114: Illumination beam 116: Soft defects

Claims

1. A method for removing contaminants from an extreme ultraviolet (EUV) photomask, the method comprising: a) Inspect the extreme ultraviolet photomask for contaminants; b) Provide an aqueous cleaning composition consisting of water, sulfonic acid or its salt, a chloride ion source and an oxidant; and c) bringing the extreme ultraviolet photomask into contact with the aqueous cleaning composition containing sulfonic acid and chloride ion source to remove at least tin from the extreme ultraviolet photomask.

2. The method as described in claim 1, wherein, The sulfonic acid has the following formula: RS(=O)2-OH (I), where R is an alkyl or aryl group.

3. The method as described in claim 2, wherein, R is CnH2n+1, and the variable n is an integer of 1 and larger.

4. The method as described in claim 3, wherein, R is CnH2n+1, and the variable n is an integer from 1 to 4.

5. The method as described in claim 1, wherein, The amount of the sulfonic acid is at least 10 wt%.

6. The method as described in claim 5, wherein, The amount of this sulfonic acid is 15-65 wt%.

7. The method as described in claim 1, wherein, The amount of the chloride ion source is at least 0.05 wt%.

8. The method as described in claim 7, wherein, The amount of the chloride ion source is at least 0.1-5 wt%.

9. The method as described in claim 1, wherein, The salt of this sulfonic acid has the following formula: RS(=O)2-O-Y+ (II), where R is an alkyl or aryl group and Y+ is a counter cation.

10. The method as described in claim 1, wherein, The water-based cleaning component is kept at a temperature of at least 30°C.

11. The method as described in claim 10, wherein, The water-based cleaning component is suitable for temperatures between 50°C and 85°C.

12. A method for removing contaminants from an extreme ultraviolet (EUV) photomask, the method comprising: a) Inspect the extreme ultraviolet photomask for contaminants; b) Provide an aqueous cleaning composition consisting of water, a chloride ion source, a sulfonic acid or a salt thereof having the following formula, an oxidant and a surfactant: RS(=O)2-OH (I), wherein R is an alkyl or aryl group; and c) Contact the extreme ultraviolet photomask with the aqueous cleaning composition to remove at least tin from the extreme ultraviolet photomask.

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