EUV mask with capping layer and method for manufacturing such an EUV mask

Abstract

Extreme ultraviolet mask, EUV mask (400), comprising a substrate (102); a reflective multilayer stack (110) on the substrate (102); a capping feature (125') on the reflective multilayer stack (110), wherein the capping feature (125') comprises a first capping layer (120', 120P') having a material with an amorphous structure, wherein the capping feature (125') further comprises a second capping layer (130', 130P') having a material with an amorphous structure, wherein the material of the second capping layer (130', 130P') differs from the material of the first capping layer (120', 120P') and is selected from alloys containing one or more elements selected from Rh, Ir, Pt, Au and Zr, or alloys thereof; and a structured absorber layer (140P) on the capping feature (125').

Description

PRIORITY CLAIM AND CROSS-REFERENCE

[0001] This application claims priority over the preliminary US patent application No. 63 / 282,289, filed on November 23, 2021, which is incorporated by reference into the present application. GENERAL STATE OF THE ART

[0002] The semiconductor industry is experiencing exponential growth. Technological advances in materials and design have spawned generations of integrated circuits (ICs), each generation featuring smaller and more complex circuits than the previous one. Throughout IC evolution, functional density (i.e., the number of interconnected devices per unit area of ​​the chip) has generally increased, while geometric size (i.e., the smallest component or trace that can be produced using a manufacturing process) has decreased. This miniaturization process generally offers advantages by increasing production efficiency and reducing associated costs.

[0003] Photolithography can be used to create components or traces on a semiconductor wafer. One example of a photolithographic technique uses extreme ultraviolet (EUV) energy and a structured absorber layer of an EUV mask. List of characters

[0004] Aspects of this disclosure are best understood with reference to the following detailed description in conjunction with the accompanying drawings. It should be noted that, in accordance with industry practice, various features are not shown to scale. In fact, the dimensions of the various features may have been arbitrarily enlarged or reduced for the sake of clarity. Fig. Figure 1 is a cross-sectional view of an extreme ultraviolet (EUV) mask according to a first embodiment. Fig. Figure 2 is a flowchart of a procedure for producing the EUV mask of Fig. 1 according to some embodiments. Fig. 3A to Fig. 3J are cross-sectional views of an EUV mask at various stages of the manufacturing process. Fig. 2 according to some embodiments. Fig. Figure 4 is a cross-sectional view of an extreme ultraviolet (EUV) mask according to a second embodiment. Fig. Figure 5 is a flowchart of a procedure for producing the EUV mask of Fig. 4 according to some embodiments. Fig. 6A to Fig. 6L are cross-sectional views of an EUV mask at various stages of the manufacturing process. Fig. 5 according to some embodiments. Fig. Figure 7 is a flowchart of a procedure for using an EUV mask according to some embodiments. Fig. Figure 8 is a flowchart of a procedure for using an EUV mask according to some embodiments. Fig. Figure 9 presents the results of an evaluation of the thickness of the carbon impurity on a capping layer according to embodiments of the present disclosure. DETAILED DESCRIPTION

[0005] The following disclosure provides many different embodiments or examples for implementing various features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to represent a limitation. For example, the formation of a first element over or on top of a second element in the following description may include embodiments in which the first and second elements are formed in direct contact, and also embodiments in which additional elements may be formed between the first and second elements, so that the first and second elements may not be in direct contact. Furthermore, reference numerals and / or letters may be repeated in the various examples in the present disclosure.This repetition serves the purpose of simplicity and clarity and does not in itself prescribe any relationship between the various designs and / or structures discussed.

[0006] Furthermore, spatially related terms such as "below," "under," "above," "above," and the like can be used here to simplify the description and describe the relationship of one element or feature to another element(s) or feature(s) as depicted in the figures. These spatially related terms are intended to encompass various orientations of the device in use or operation, in addition to the orientation shown in the figures. The device may be oriented differently (rotated by 90 degrees or in other orientations), and the spatially related terms used here can be interpreted accordingly.

[0007] In the fabrication of integrated circuits (ICs), during the process of manufacturing semiconductor devices, structures representing different layers of the ICs are produced using a series of reusable photomasks (also referred to in this application as photolithography masks or masks) to transfer the design of each layer of the ICs onto a semiconductor substrate.

[0008] With the miniaturization of integrated circuits (ICs), extreme ultraviolet (EUV) light with a wavelength of, for example, 13.5 nm is used in lithography processes to enable the transfer of very small structures (e.g., structures in the nanometer range) from a mask to a semiconductor wafer. Since most materials are highly absorbent at a wavelength of 13.5 nm, EUV lithography uses a reflective EUV mask with a reflective multilayer to reflect the incident EUV light and an absorber layer on top of the reflective multilayer to absorb the radiation in areas where the light should not be reflected by the mask. The reflective multilayer and the absorber layer are located on a substrate made of a material with low thermal expansion.The reflective multilayer reflects incident EUV light, and the structured absorber layer on the reflective multilayer absorbs the light in areas where the light should not be reflected by the mask. The mask structure is defined by the absorber layer and transferred to a semiconductor wafer by reflecting the EUV light from sections with a reflective surface of the EUV mask.

[0009] The ongoing demand for more densely packed integrated devices has led to modifications in the photolithography process to create smaller individual element sizes. The smallest element size, or "critical dimension" (CD), obtainable by a process is approximately determined by the formula CD = k1 * λ / NA, where k1 is a process-specific coefficient, λ is the wavelength of the applied light / energy, and NA is the numerical aperture of the optical lens as seen from the substrate or wafer.

[0010] The present disclosure describes various embodiments of an EUV mask that exhibits resistance to carbon contamination and employs durable capping features that continue to protect the underlying reflective multilayer stack from oxidizing agents even after exposure to etching or cleaning processes during mask fabrication. Carbon contamination can adversely affect the critical dimensions of elements formed in an absorber layer and a capping feature of the EUV mask. For example, some materials used as capping layers contain many free radicals that can react with carbon atoms near the EUV mask during EUV energy exposure.During exposure, hydrocarbon molecules near the surface of the EUV mask can be fractured when subjected to high energy and deposited on exposed surfaces (e.g., sidewalls and bottoms, or grooves in the absorber material). The fracture of these hydrocarbon molecules can generate carbon atoms that can react with free radicals. Carbon has been observed to deposit in greater thicknesses on exposed surfaces of the mask located near the center compared to exposed surfaces near the edges. In some embodiments, the amount of carbon forming on exposed surfaces near the center of the mask is three times greater than the amount forming on exposed surfaces near the edges.Hydrocarbons can originate from numerous sources, including outgassing from materials within the EUV tool, such as tool elements, photoresists, or hard masks used in the tool. The resulting carbon atoms or carbon-containing molecules react with or are absorbed by materials they come into contact with and accumulate on EUV mask surfaces. Carbon accumulation on EUV mask surfaces, such as capping layer surfaces or the sidewalls of elements in the absorber material, can adversely affect the EUV mask's ability to pattern elements that meet critical dimension uniformity (CDU) criteria onto a substrate. For example, carbon absorbs EUV wavelengths to a greater extent than other materials forming an EUV mask.Therefore, the exposure energy, or the amount of incident EUV energy required to achieve a desired level of EUV radiation reflected by the mask, is greater when unwanted carbon is present on the EUV mask than when it is absent. In some embodiments, the required exposure energy when carbon is present on the EUV mask can be 10% or more than when carbon is absent, depending on the critical dimensions of the elements on the wafer and the critical dimensions of the elements on the mask. This increased exposure energy requirement will increase the cost of the energy required for effective wafer exposure or lengthen the time needed to achieve a desired level of exposure.

[0011] Some embodiments of EUV masks of the present disclosure exhibit improved strength and / or resistance to etching and cleaning processes to which the EUV mask materials are subjected during the mask's manufacture. The strength and / or resistance to etching and cleaning processes to which the EUV mask materials are subjected during the mask's manufacture is important because a weak or damaged layer of the mask is susceptible to penetration by oxidizing agents such as oxygen. Oxygen penetrating a damaged or weak layer of the mask can react with materials of the reflective multilayer and form undesirable oxide layers on a top surface of the reflective multilayer.

[0012] Embodiments according to the present disclosure generally provide a photolithography mask having a capping feature over the reflective multilayer stack of the mask. In some embodiments, the capping feature comprises a single layer of a capping material, and in other embodiments, the capping feature comprises multiple capping layers of a capping material. In some embodiments, the capping feature has a first capping layer comprising a material with an amorphous structure. This first capping layer can be combined with a second capping layer comprising materials with an amorphous structure. In some embodiments, the material of the first capping layer comprises an element that has a carbon solubility in the solid state of less than 3 atomic percent at the eutectic point of a system containing the element and carbon.Examples of elements useful in a capping layer of a capping feature according to embodiments of this disclosure include Rh, Ir, Pt, Au, and Zr, or alloys thereof. In other embodiments, a capping layer of a capping feature according to this disclosure comprises Hf, Nb, or N. In other embodiments, a capping layer of a capping feature according to this disclosure comprises Ag or Cu. In other embodiments, a capping layer of a capping feature according to this disclosure comprises Pd. According to embodiments of this disclosure, a single-layer capping feature is used to reduce carbon accumulation or contamination on surfaces of the EUV mask.The materials of a capping layer formed according to the present disclosure reduce the susceptibility of the capping feature to contamination by hydrocarbon molecules or carbon atoms. The materials of a capping feature formed according to the present disclosure also protect an underlying reflective multilayer from the effects of oxidizing agents and the formation of undesirable oxide layers.

[0013] In examples of the present disclosure relating to a multilayer capping feature, the material used for one capping layer of the multilayer element differs in composition from the material used for another capping layer of the multilayer capping feature. These materials may correspond to the description in the preceding paragraph regarding the materials for use in a capping feature having only a single capping layer. In some embodiments, the material of a capping layer exhibits a carbon solubility property in a solid state that differs from the carbon solubility property in a solid state of the material of another capping layer of the multilayer capping feature.For example, in some embodiments, a multilayer capping feature is provided, comprising a first capping layer formed from a material containing an element with a first carbon solubility property. The multilayer capping feature comprises at least one other capping layer formed from a material containing an element with a second carbon solubility property that differs from the first carbon solubility property of the element in the material of the first capping layer. In some embodiments, the carbon solubility in a solid state of the elements in the material of the first capping layer and the second capping layer at the eutectic point of a system containing the element and carbon is less than 3 atomic percent.The carbon solubility property in a solid state refers to the maximum carbon solubility in the solid phase of a system containing the element and carbon, which is in equilibrium with a liquid phase at a eutectic point of the system. The carbon solubility in a solid state of an element within a capping layer material indicates the tendency of that element to react with, retain, attract, or absorb carbon atoms or carbon-containing molecules. When carbon atoms are attracted to, retained, absorbed, or react with the capping layer material, they accumulate and contaminate the capping layer. In some situations, the carbon accumulation or contamination completely covers exposed portions of the capping layer.In other situations, the carbon accumulation or contamination partially covers the capping layer. In other situations, the carbon accumulation or contamination at least partially covers sections of the sidewalls of the mask's absorber material. The presence of a layer of carbon contamination alters the dimensions and EUV transmittance properties of the mask. Such changes in dimensions and / or changes in the incident EUV energy required to generate a desired level of reflected EUV energy cause the adverse effects described in the preceding paragraph. According to embodiments of this disclosure, a multilayer capping feature comprising several individual capping layers is used to protect EUV masks from carbon accumulation or contamination on the surfaces of the EUV mask.The materials of the capping layers formed according to the present disclosure reduce the susceptibility of the multilayer capping feature to contamination by hydrocarbon molecules or carbon atoms. The materials of a capping feature formed according to the present disclosure also protect an underlying reflective multilayer from the action of oxidizing agents and the formation of unwanted oxide layers.

[0014] In embodiments of the present disclosure, an EUV mask has a multilayer capping feature comprising at least one capping layer containing a material that includes an element with low carbon solubility in a solid state. An element exhibiting low carbon solubility in a solid state is characterized by a maximum carbon solubility in a solid phase of a system of the element and carbon in equilibrium with a liquid phase of the system at the eutectic point of the system. An example of an element with low carbon solubility in a solid state is one with a carbon solubility in a solid state of less than about 3 atomic percent. Examples of elements with low carbon solubility in a solid state that are less than about 3 at.-% includes, but is not limited to, materials with a carbon solubility in a solid state of less than 3 at.% and, in some embodiments, less than 2 at.%. For example, in some embodiments, capping layer materials do not exhibit a carbon solubility in a solid state of less than about 3 at.%, yet still offer resistance to carbon accumulation or contamination on the surface of the material. Elements with low carbon solubility in a solid state, which are useful in embodiments of the present disclosure, are alternatively characterized by an effective carbon solubility in a solid state in the element at 1000 °C of less than 1.6.The effective carbon solubility in a solid state in the element at 1000 °C is obtained by multiplying the value of the carbon solubility in a solid state at the eutectic point by 1000 °C / the eutectic point of the system consisting of the element and carbon. According to some embodiments of multilayer capping features of the present disclosure, the element(s) of the material of a capping layer exhibit a carbon solubility in a solid state that differs from the carbon solubility in a solid state of the element(s) of the material of another capping layer forming the multilayer capping feature.In some embodiments, the material of at least one layer of the multilayer capping feature includes an element having an EUV extinction coefficient for 13.5 nm EUV radiation that is greater or less than the EUV extinction coefficient for 13.5 nm EUV radiation of an element in another layer of the multilayer capping feature. If the individual capping layers of the multilayer capping feature contain materials with elements having different EUV extinction coefficients for 13.5 nm EUV radiation, the amount of incident EUV energy absorbed in one capping layer differs from the amount of EUV energy absorbed in another capping layer of the multilayer capping feature.For example, in some embodiments, an element of the material in a capping layer has an EUV extinction coefficient for EUV radiation with a wavelength of 13.5 nm between 0 and 0.1, and an element of the material in another capping layer has an EUV extinction coefficient for EUV radiation with a wavelength of 13.5 nm that differs from the EUV extinction coefficient of the element in the first capping layer. In other embodiments, the material of the first capping layer has an element with an EUV extinction coefficient for EUV radiation with a wavelength of 13.5 nm between 0 and 0.08, between 0 and 0.06, between 0 and 0.04, or between 0 and 0.02.Materials containing an element with an EUV extinction coefficient for EUV radiation with a wavelength of 13.5 nm in the regions described above do not reduce the transfer of EUV energy to such an extent that an undesirable increase in the amount of incident EUV energy is required. Materials for use in capping layers of multilayer capping features according to the present embodiments should not absorb so much EUV energy that the amount of EUV energy incident on the EUV mask needs to be increased or the exposure time extended undesirably.Furthermore, the materials for use in a single capping layer of a capping feature or in capping layers of multilayer capping features according to disclosed embodiments exhibit good adhesion to each other as well as to materials on which the capping layer(s) is / are deposited or to materials deposited on the capping layer(s). Elements suitable as materials for a capping layer according to embodiments of the present disclosure include elements exhibiting a carbon binding energy of less than approximately 285 electron volts (eV). Examples of elements exhibiting a carbon binding energy of less than approximately 285 eV include rh, ir, and pt. The elements exhibiting a carbon binding energy of less than approximately 285 eV are not limited to rh, ir, and pt.Other elements with a binding energy for carbon of less than about 285 eV are also useful as elements of a material used in capping layers according to the present disclosure.

[0015] In some embodiments, the capping feature comprises at least one capping layer comprising rhodium (Rh), iridium (Ir), platinum (Pt), gold (Au), and / or zirconium (Zr), or alloys thereof. Examples of alloys of Rh, Ir, Pt, Au, or Zr include RuZr, IrZr, RhZr, HfZr, NbZr, and ZnZr. Additional examples of alloys of Rh, Ir, Pt, Au, or Zr according to the present disclosure include RuRh, RuIr, RuPt, PtIr, RuIrPt, NbIr, NbPt, NbRh, RhN, IrN, RuRhN, RuIrN, RuPtN, PtIrN, RuIrPtN, NbIrN, NbPtN, and NbRhN. For example, a capping layer according to the present disclosure can be an alloy such as RuRh (5 at.% to 100 at.% Rh), RuIr (5 at.% to 100 at.% Ir), RuPt (5 at.% to 100 at.% Pt), PtIr (5 at.% to 100 at.% Ir), RuIrPt (5 at.% to 100 at.% Ir), RuIrPt (5 at.% to 100 at.% Pt), NbIr (5 at.% to 100 at.% Ir), NbPt (5 at.% to 100 at.% Pt), NbRh (5 at.% to 100 at.% Rh), RhN (5 at.% to 100 at.% Rh), IrN (5 at.% to 100 at.% Pt).-% Ir), RuRhN (5 at.% to 100 at.% Rh), RuRhN (5 at.% to 100 at.% N), RuIrN (5 at.% to 100 at.% Ir), RuIrN (5 at.% to 100 at.% N), RuPtN (5 at.% to 100 at.% Pt), RuPtN (5 at.% to 100 at.% N), PtIrN (5 at.% to 100 at.% Ir), PtIrN (5 at.% to 100 at.% N), RuIrPtN (5 at.% to 100 at.% Ir), RuIrPtN (5 at.% to 100 at.% Pt), RuIrPtN (5 at.% to 100 at.% N), NbIrN (5 at.% to 100 at.% Ir), NbPtN (5 at.% to 100 at.% Pt) or NbRhN (5 at.% to 100 at.% Rh). In other embodiments, a capping layer according to the present disclosure may comprise an alloy containing Hf, Nb, or N. In other embodiments, a capping layer according to the present disclosure may comprise an alloy containing Ag or Cu. In other embodiments, a capping layer according to the present disclosure may comprise an alloy containing Pd.

[0016] In some embodiments, the single- or multi-layer capping feature comprises at least one layer containing a material with an element having a refractive index greater than 0.87 and less than 0.97. Examples of materials with a refractive index greater than 0.87 and less than 0.97 include, but are not limited to, the materials described above.

[0017] Fig. Figure 1 is a cross-sectional view of an EUV mask 100 according to a first embodiment of the present disclosure. With reference to Fig. Figure 1 of the EUV mask 100 comprises a substrate 102, a reflective multilayer stack 110 over a front surface of the substrate 102, and a capping feature 125 over the reflective multilayer stack 110, which includes a first structured capping layer 120P and a structured absorber layer 140P over the capping feature 125. The EUV mask 100 further comprises a conductive layer 104 over a rear surface of the substrate 102 opposite the front surface.

[0018] The structured absorber layer 140P has a structure of openings 152, corresponding to structures of conductive or non-conductive elements to be formed on or in a semiconductor wafer. The structure of openings 152 is located in a feature area 100A of the EUV mask 100 and exposes a surface of the first capping layer 120P. Feature area 100A is surrounded by a peripheral area 100B of the EUV mask 100. The peripheral area 100B corresponds to an unstructured area of ​​the EUV mask 100 that is not used in an exposure process during IC fabrication. In some embodiments, the structural area 100A of the EUV mask 100 is located in a central region of the substrate 102, and the peripheral area 100B is located at an edge section of the substrate 102. The structural area 100A is separated from the peripheral area 100B by grooves 154.The trenches 154 extend through the structured absorber layer 140P, the first capping layer 120P and the reflective multilayer stack 110, exposing the front surface of the substrate 102.

[0019] According to some embodiments of the present disclosure, the structured absorber layer 140P is a layer of an absorber material that is an alloy of a transition metal, e.g. tantalum (Ta), ruthenium (Ru), chromium (Cr), platinum (Pt), gold (Au), iridium (Ir), titanium (Ti), niobium (Nb), rhodium (Rh), molybdenum (Mo), tungsten (W) or palladium (Pd), and at least one alloying element selected from ruthenium (Ru), chromium (Cr), tantalum (Ta), platinum (Pt), palladium (Pd), tungsten (W), gold (Au), iridium (Ir), titanium (Ti), niobium (Nb), rhodium (Rh), molybdenum (Mo), hafnium (Hf), boron (B), nitrogen (N), oxygen (O), silicon (Si), zirconium (Zr) or vanadium (V).

[0020] Fig. Figure 2 is a flowchart of a process 200 for manufacturing an EUV mask according to an embodiment of the present disclosure, for example the EUV mask 100. Fig. 3A to Fig. Figures 3L are cross-sectional views of the EUV mask 100 at various stages of the manufacturing process according to some embodiments. The process 200 is discussed in detail below with reference to the EUV mask 100. In some embodiments, additional activities are performed before, during, and / or after the process 200, or some of the described activities are replaced and / or eliminated. In some embodiments, some of the features described below are replaced or eliminated. A person skilled in the art would understand that although some embodiments are discussed with activities performed in a particular sequence, these activities may be performed in a different logical order.

[0021] With reference to Fig. 2 and Fig. 3A the method 200 comprises an activity 202 in which a reflective multilayer stack 110 is formed over a substrate 100, according to some embodiments. Fig. Figure 3A is a cross-sectional view of an initial setup of an EUV mask 100 after forming the reflective multilayer stack 110 over the substrate 102 according to some embodiments.

[0022] With reference to Fig. 3A The initial setup of the EUV mask 100 includes a substrate 102 made of glass, silicon, quartz, or other materials with low thermal expansion. The low thermal expansion material helps to minimize image distortion due to heating of the mask during use of the EUV mask 100. In some embodiments, the substrate 102 comprises fused silica, quartz glass, calcium fluoride, silicon carbide, black diamond, or titanium oxide-doped silicon dioxide (SiO₂). 2 / TiO2). In some embodiments, the substrate 102 has a thickness ranging from approximately 1 mm to approximately 7 mm. If the thickness of the substrate 102 is too small, the risk of breakage or rejection of the EUV mask 100 increases in some cases. Conversely, if the thickness of the substrate is too large, the weight and cost of the EUV mask 100 are unnecessarily increased in some cases.

[0023] In some embodiments, a conductive layer 104 is deposited on a rear surface of the substrate 102. In some embodiments, the conductive layer 104 is in direct contact with the rear surface of the substrate 102. The conductive layer 104 is designed to provide electrostatic coupling of the EUV mask 100 to an electrostatic clamping device (not shown) during its manufacture and use. In some embodiments, the conductive layer 104 comprises chromium nitride (CrN) or tantalum boride (TaB). In some embodiments, the conductive layer 104 is formed by a deposition process such as, for example, chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECV), or physical vapor deposition (PVD).The thickness of the conductive layer 104 is controlled so that the conductive layer 104 is optically transparent.

[0024] The reflective multilayer stack 110 is arranged above a front surface of the substrate 102 opposite the back surface. In some embodiments, the reflective multilayer stack 110 is in direct contact with the front surface of the substrate 102. The reflective multilayer stack 110 provides high reflectivity to the EUV light. In some embodiments, the reflective multilayer stack 110 is configured to achieve a reflectivity of approximately 60% to approximately 70% at the peak EUV irradiation wavelength, e.g., EUV irradiation at 13.5 nm. In particular, the maximum reflectance of the light in the vicinity of a wavelength of 13.5 nm when the EUV light is applied at an angle of incidence of 6° to the surface of the reflecting multilayer stack 110 is approximately 60%, approximately 62%, approximately 65%, approximately 68%, approximately 70%, approximately 72%, or approximately 75%.

[0025] In some embodiments, the reflective multilayer stack 110 comprises alternating stacked layers of a material with a high refractive index and a material with a low refractive index. On the one hand, a material with a high refractive index tends to scatter EUV light, while on the other hand, a material with a low refractive index tends to transmit EUV light. A pairing of these two types of materials provides resonant reflectivity. In some embodiments, the reflective multilayer stack 110 comprises alternating stacked layers of molybdenum (Mo) and silicon (Si). In some embodiments, the reflective multilayer stack 110 comprises alternating stacked Mo and Si layers, with Si located in the topmost layer. In some embodiments, a molybdenum layer is in direct contact with the front surface of the substrate 102.In some other embodiments, a silicon layer is in direct contact with the front surface of the substrate 102. Alternatively, the reflective multilayer stack 110 has alternating stacked layers of Mo and beryllium (Be).

[0026] The thickness of each layer in the reflective multilayer stack 110 depends on the EUV wavelength and the angle of incidence of the EUV light. The thickness of alternating layers in the reflective multilayer stack 110 is tuned to maximize the constructive interference of the EUV light reflected at each interface and to minimize the total absorption of the EUV light. In some embodiments, the reflective multilayer stack 110 has 30 to 60 pairs of alternating Mo and Si layers. Each Mo / Si pair has a thickness ranging from about 2 nm to about 7 nm, with a total thickness ranging from about 100 nm to about 300 nm. In some embodiments, the thicknesses of the alternating layers in the reflective multilayer stack 110 vary.

[0027] In some embodiments, each layer in the reflective multilayer stack 110 is deposited over the substrate 102 and the underlying layer using ion beam deposition (IBD) or direct current magnetron sputtering. The deposition method used helps to ensure that the thickness uniformity of the reflective multilayer stack 110 across the substrate 102 is better than 0.85. For example, to form a reflective multilayer Mo / Si stack 110, a Mo layer is deposited using a Mo target as the sputtering target and an argon gas (Ar gas) (at a gas pressure of 1.3 × 10⁻⁶). -2 Pa up to 2.7 × 10 -2Pa) as a sputtering gas with an ion acceleration voltage of 300 V to 1,500 V at a deposition rate of 0.03 to 0.30 nm / s and then a deposition of a Si layer using a Si target as a sputtering target and an Ar gas (with a gas pressure of 1.3 × 10 -2 Pa up to 2.7 × 10 -2 Pa) as a sputtering gas with an ion acceleration voltage of 300 V to 1,500 V at a deposition rate of 0.03 to 0.30 nm / s. The reflective multilayer Mo / Si stack is deposited by stacking Si layers and Mo layers in 40 to 50 cycles, each cycle comprising the steps above.

[0028] With reference to Fig. 2 and Fig. 3B transitions from the process 200 to an activity 204 in which a first capping layer 120 is deposited over the reflective multilayer stack 110, according to some embodiments. Fig. 3B is a cross-sectional view of the structure of Fig. 3A after the deposition of the first capping layer 120 over the reflective multilayer stack 110 according to some embodiments.

[0029] With reference to Fig. 3B will be the first capping layer 120 (of the capping feature 125 in Fig. 1 and Fig. 3C) is deposited over the top surface of the reflective multilayer stack 110. As described in this application, the first capping layer 120 comprises a material in an amorphous state. In some embodiments, the material exhibits low carbon solubility in a solid state, which serves to prevent or reduce carbon contamination of the mask.

[0030] Materials in an amorphous state include materials that are solid and lack the long-range order characteristic of a crystal. Materials in an amorphous state are sometimes described as being in a glassy or vitreous state. A "glassy solid" or an "amorphous solid" is considered the all-encompassing concept, with glass being a special case, as glass is an amorphous solid stabilized below its glass transition temperature. Polymers are frequently amorphous. Other types of amorphous solids include gels, thin films, and nanostructured materials. Materials in an amorphous state possess an internal structure made up of linked structural blocks. These blocks may be similar to the basic structural units found in the corresponding crystalline phase of the same material.Nanocrystalline materials are examples of materials in an amorphous state and are characterized in the present disclosure by a grain size of less than 5 nm, less than 4 nm, less than 3 nm, or less than 2 nm. Materials in an amorphous state that are suitable as capping material according to the present disclosure include the capping material described above.

[0031] In some embodiments, the first capping layer 120 comprises a material that is less susceptible to carbon contamination compared to the use of conventional materials as capping layers. Such materials were described above. As described above, these materials include elements with a low effective carbon solubility in the element of the material at 1000 °C, e.g., an effective carbon solubility in a solid state of less than 1.6 at.% at 1000 °C. Other examples of materials comprising elements with a low atomic percent effective carbon solubility in a solid state at 1000 °C include, but are not limited to, materials comprising elements comprising an effective carbon solubility in a solid state at 1000 °C of less than approximately 1.3 at.%.In some embodiments, materials of a capping layer include elements that do not exhibit effective carbon solubility in a solid state of less than about 1.6 at.% or less than about 1.3 at.%, but nevertheless offer resistance to carbon accumulation or contamination on the surface of the material. In some embodiments according to... Fig. 1. The material of the first capping layer 120 comprises an element with an EUV extinction coefficient for EUV radiation with a wavelength of 13.5 nm between 0 and 0.1, 0 and 0.08, 0 and 0.06, 0 and 0.04, or between 0 and 0.02. Materials comprising elements with an EUV extinction coefficient for EUV radiation with a wavelength of 13.5 nm in the above ranges do not reduce the transfer of EUV energy to an extent that necessitates an undesirable increase in the amount of incident EUV energy. The materials for use in capping layers of the capping features according to the present embodiments should not absorb so much EUV energy that the amount of EUV energy incident on the EUV mask needs to be increased or the exposure time needs to be extended undesirably.Furthermore, the materials for use in capping layers of the capping features according to the present embodiment exhibit good adhesion to materials on which the capping layers are deposited or to materials deposited on the capping layers. According to embodiments of the present disclosure, carbides of the elements described above are undesirable for use as material for the first capping layer 120 because, during their heat treatment, carbon atoms can diffuse from the carbide into a lower layer. In some embodiments, the multilayer capping feature 125 has at least one layer 120 comprising a material containing an element with a refractive index for EUV radiation with a wavelength of 13.5 nm of less than 0.97.In some embodiments, the multilayer capping feature 125 includes at least one layer 120 comprising a material containing an element with a refractive index for EUV radiation at a wavelength of 13.5 nm greater than 0.87. Examples of materials comprising elements with a refractive index for EUV radiation at a wavelength of 13.5 nm less than 0.97 or greater than 0.87 include, but are not limited to, the materials described above. In some embodiments, the first capping layer 120 has a thickness in the range of about 0.5 to 5 nm. A first capping layer 120 with a thickness in the range of 0.5 to 5 nm is thick enough to prevent or reduce carbon contamination without being so thick as to reduce EUV transmission by an undesirable amount.Embodiments according to the present disclosure are not limited to EUV masks having a first capping layer 120 with a thickness of 0.5 to about 5 nm. Embodiments according to the present disclosure include EUV masks having a first capping layer 120 with a thickness of less than 0.5 nm and EUV masks having a first capping layer 120 with a thickness of more than about 5 nm.

[0032] In some embodiments, the first capping layer 120 is formed using a deposition process such as, for example, IBD, chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), thermal ALD, PE-ALD, PECVD, electron beam evaporation, thermal evaporation, ion beam induced deposition, sputtering, electrodeposition or electroless deposition.

[0033] With reference to Fig. 2 and Fig. 3C transitions the process 200 to an activity 208 in which an absorber layer 140 is deposited over the first capping layer 120, according to various embodiments. Fig. 3C is a cross-sectional view of the structure of Fig. 3B after the deposition of the absorber layer 140 over the first capping layer 120 according to some embodiments.

[0034] With reference to Fig. In step 3C, the absorber layer 140 is arranged in direct contact with the first capping layer 120. The absorber layer 140 can be used to absorb radiation with the EUV wavelength projected onto the EUV mask 100.

[0035] The absorber layer 140 comprises an absorber material with a high extinction coefficient κ and a low refractive index n for EUV wavelengths. In some embodiments, the absorber layer 140 comprises an absorber material with a high extinction coefficient and a low refractive index at a wavelength of 13.5 nm. In other embodiments, the absorber layer comprises an absorber material with a low extinction coefficient and a high refractive index for EUV radiation with a wavelength of 13.5 nm. According to some embodiments of the present disclosure, the refractive index and the extinction coefficient of the material of the absorber layer 140 refer to light with a wavelength of approximately 13.5 nm. According to some embodiments, the thickness of the absorber layer 140 is less than approximately 80 nm. According to other embodiments, the thickness of the absorber layer 140 is less than approximately 60 nm.Other embodiments use an absorber layer 140 of less than about 50 nm.

[0036] In some embodiments, the absorber material is in a polycrystalline state characterized by grains, grain boundaries, and distinct formation phases. In other embodiments, the absorber material is in an amorphous state, characterized, for example, by grains on the order of less than 5 nanometers, less than 3 nanometers, less than 2 nanometers, or no grain boundaries and a single phase. According to some embodiments of the present disclosure, the absorber material has interstitial elements selected from nitrogen (N), oxygen (O), boron (B), carbon (C), or combinations thereof. Interstitial elements, as used in this application, refer to elements located in the spaces between materials with a main alloy and an alloying element of absorber materials formed according to the present disclosure.

[0037] The absorber layer 140 is formed by deposition techniques such as PVD, CPD, ALD, RF magnetron sputtering, DC magnetron sputtering, or IBD. The deposition process can be carried out in the presence of elements described as interstitials, such as boron or nitrogen. Performing the deposition in the presence of these interstitials results in the incorporation of the interstitials into the material of the absorber layer 140.

[0038] According to embodiments of the present disclosure, numerous combinations of different families of alloy materials are useful as absorber materials. Each of the different families of alloys has a principal alloying element selected from a transition metal and at least one alloying element. In some embodiments, the principal alloying element comprises up to 90 atm% of the alloy used as the absorber material. In some embodiments, the principal alloying element comprises more than 50 atm% of the alloy used as the absorber material. In some embodiments, the principal alloying element comprises approximately 50 to 90 atm% of the alloy used as the absorber material.

[0039] In some embodiments, the principal alloying element is a transition metal selected from ruthenium (Ru), chromium (Cr), tantalum (Ta), platinum (Pt), gold (Au), iridium (Ir), titanium (Ti), niobium (Nb), rhodium (Rh), molybdenum (Mo), tungsten (W), and palladium (Pd). In some embodiments, the at least one alloying element is a transition metal, a metalloid, or a reactive nonmetal. Examples of a transition metal as the at least one alloying element include ruthenium (Ru), chromium (Cr), tantalum (Ta), platinum (Pt), palladium (Pd), tungsten (W), gold (Au), iridium (Ir), titanium (Ti), niobium (Nb), rhodium (Rh), molybdenum (Mo), hafnium (Hf), zirconium (Zr), and vanadium (V). Examples of a metalloid as the at least one alloying element include boron (B) and silicon (Si). Examples of a reactive nonmetal as having at least one alloying element include nitrogen (N) or oxygen (O).

[0040] To etch the various absorber materials of the present disclosure, different materials can be used, and with the various absorber materials, different materials can be used as the hard mask layer. For example, in some embodiments, the absorber layer 140 is dry-etched with a gas containing chlorine, such as Cl₂ or BCl₃, or with a gas containing fluorine, such as NF₃. Ar can be used as the carrier gas. In some embodiments, oxygen (O₂) can also be used as the carrier gas. For example, a chlorine-based etchant, a chlorine-based etchant plus oxygen, or a mixture of chlorine-based and fluorine-based etchants (e.g.,Carbon tetrafluoride and carbon tetrachloride) etch alloys comprising a major alloying element comprising ruthenium (Ru), chromium (Cr), tantalum (Ta), platinum (Pt) or gold (Au), and at least one alloying element selected from ruthenium (Ru), chromium (Cr), tantalum (Ta), platinum (Pt), palladium (Pd), tungsten (W), gold (Au), iridium (Ir), niobium (Nb), rhodium (Rh), molybdenum (Mo), hafnium (Hf) or vanadium (V). In some embodiments, a fluorine-based etchant is suitable for etching alloys comprising a major alloying element comprising iridium (Ir), titanium (Ti), niobium (Nb) or rhodium (Rh) and at least one alloying element selected from boron (Bo), nitrogen (N), oxygen (O), silicon (Si), tantalum (Ta), zirconium (Zr), niobium (Nb), molybdenum (Mo), rhodium (Rh), titanium (Ti) or ruthenium (Ru).In some embodiments, a fluorine-based or fluorine-based plus oxygen etching agent is suitable for etching alloys comprising a major alloying element comprising molybdenum (Mo), tungsten (Wo) or palladium (Pd) and at least one alloying element selected from ruthenium (Ru), palladium (Pd), tungsten (W), iridium (Ir), titanium (Ti), niobium (Nb), rhodium (Rh), molybdenum (Mo), silicon (Si) or zirconium (Zr).

[0041] According to some embodiments, SiN, TaBO, TaO, SiO, SiON and SiOB are examples of materials that are useful as a hard mask layer 160 for an absorber layer 140, which uses alloys with a major alloying element comprising ruthenium (Ru), chromium (Cr), tantalum (Ta), platinum (Pt) or gold (Au), and at least one alloying element selected from ruthenium (Ru), chromium (Cr), tantalum (Ta), platinum (Pt), palladium (Pd), tungsten (W), gold (Au), iridium (Ir), niobium (Nb), rhodium (Rh), molybdenum (Mo), hafnium (Hf) or vanadium (V).CrO and CrON are examples of materials suitable as a hard mask layer 160 for an absorber layer 140, which are alloys with a major alloying element comprising iridium (Ir), titanium (Ti), niobium (Nb), or rhodium (Rh), and at least one alloying element selected from boron (B), nitrogen (N), oxygen (O), silicon (Si), tantalum (Ta), zirconium (Z), niobium (Nb), molybdenum (Mo), rhodium (Rh), titanium (Ti), or ruthenium (Ru). SiN, TaBO, TaO, CrO, and CrON are examples of materials suitable as a hard mask layer 160 for an absorber layer 140, which are alloys with a major alloying element comprising molybdenum (Mo), tungsten (W), or palladium (Pd), and at least one alloying element selected from ruthenium (Ru), palladium (Pd), tungsten (W), or iridium (Ir). Titanium (Ti), niobium (Nb), rhodium (Rh), molybdenum (Mo), silicon (Si) or zirconium (Zr) are used as alloying elements and are useful.In other embodiments, a buffer layer (not shown) with a composition similar to that of the hard mask layer may be present between the capping feature 125 and the layer 140 of the absorber material. In some embodiments, the material of the hard mask layer 160 is the same material as that of the buffer layer or a different material. Embodiments according to the present disclosure are not limited to the above types of materials for the hard mask layer 160 or the buffer layer.

[0042] In some embodiments, the absorber layer 140 is deposited as an amorphous layer. Maintaining an amorphous phase improves the overall roughness of the absorber layer 140. The thickness of the absorber layer 140 is controlled to provide EUV light absorption at 13.5 nm between 95% and 99.5%. In some embodiments, the absorber layer 140 can have a thickness in the range of approximately 30 to 70 nm. Embodiments according to the present disclosure include absorber layers with thicknesses of less than 30 nm and thicknesses of more than 70 nm. If the thickness of the absorber layer 140 is too small, the absorber layer 140 cannot absorb a sufficient amount of EUV light to create contrast between the reflective and non-reflective areas.On the other hand, the accuracy of a structure to be formed in the absorber layer 140 is usually low if the thickness of the absorber layer 140 is too large.

[0043] With reference to Fig. 2 and Fig. In 3D, the process 200 proceeds to an activity 210 in which a resist stack comprising a hard mask layer 160 and a photoresist layer 170 is deposited over the absorber layer 140, according to some embodiments. Fig. 3E is a cross-sectional view of the structure of Fig. 3C after the successive deposition of the hard mask layer 160 and the photoresist layer 170 over the absorber layer 140 according to some embodiments.

[0044] With reference to Fig. In 3D, the hard mask layer 160 is arranged over the absorber layer 140. In some embodiments, the hard mask layer 160 is in direct contact with the absorber layer 140. In some embodiments, the hard mask layer 160 comprises a dielectric oxide such as silicon dioxide or a dielectric nitride such as silicon nitride. In some embodiments, the hard mask layer 160 is formed using a deposition process such as, for example, CVD, PECVD, or PVD. In some embodiments, the hard mask layer 160 has a thickness in the range of approximately 2 to 10 nm. Embodiments according to the present disclosure are not limited to a hard mask layer 160 with a thickness in the range of 2 to 10 nm.

[0045] The photoresist layer 170 is arranged above the hard mask layer 160. The photoresist layer 170 comprises a photosensitive material that can be used to be patterned by radiation. In some embodiments, the photoresist layer 170 comprises a positive-tone photoresist material, a negative-tone photoresist material, or a hybrid-tone photoresist material. In some embodiments, the photoresist layer 170 is applied to the surface of the hard mask layer 160, for example, by spin coating.

[0046] With reference to Fig. 2 and Fig. 3E transitions from method 200 to activity 212, in which the photoresist layer 170 is lithographically structured to form a structured photoresist layer 170P, according to some embodiments. Fig. 3F is a cross-sectional view of the structure of Fig. 3D after lithographic structuring of the photoresist layer 170 to form the structured photoresist layer 170P, according to some embodiments.

[0047] With reference to Fig. In step 3E, the photoresist layer 170 is structured by first exposing it to an irradiation pattern. Then, depending on whether a positive-tone or negative-tone resist was used in the photoresist layer 170, the exposed or unexposed sections of the photoresist layer 170 are removed with a resist developer, forming the structured photoresist layer 170P with a structure of openings 172. The openings 172 expose sections of the hard mask layer 160. The openings 172 are located in the structure region 100A and correspond to locations where the structure of openings 152 is present in the EUV mask 100. Fig. 1).

[0048] With reference to Fig. 2 and Fig. 3F goes to the process of activity 214 in which the hard mask layer 160 is etched using the structured photoresist layer 170P as an etching mask to form a structured hard mask layer 160P, according to some embodiments. Fig. 3F is a cross-sectional view of the structure of Fig. 3E after etching the hard mask layer 161 to form the structured hard mask layer 160P according to some embodiments.

[0049] With reference to Fig. In 3F, sections of the hard mask layer 160 exposed by the openings 172 are etched to form openings 162 extending through the hard mask layer 160. The openings 162 expose sections of the underlying absorber layer 140. In some embodiments, the hard mask layer 160 is etched using an anisotropic etchant employing fluorine- or chlorine-containing gases such as CF4, SF6, or Cl2. In some embodiments, the anisotropic etching is a dry etching such as reactive ion etching (RIE), wet etching, or a combination thereof. The etching selectively removes the material providing the hard mask layer relative to the material providing the absorber layer 140. The remaining sections of the hard mask layer 160 form the structured hard mask layer 160P.If the structured photoresist layer 170P was not completely consumed during the etching of the hard mask layer 160, it is removed after the etching of the hard mask layer 160, for example, by using a wet wipe or plasma ashing followed by wet cleaning from the surfaces of the structured hard mask layer 160P.

[0050] With reference to Fig. 2 and Fig. 3G transitions the process 200 to an activity 216 in which the absorber layer 140 is etched using the structured hard mask layer 160P as an etching mask to form a structured absorber layer 140P, according to some embodiments. Fig. 3G is a cross-sectional view of the structure of Fig. 3F after etching the absorber layer 140 to form the structured absorber layer 140P according to some embodiments.

[0051] With reference to Fig. In 3G, sections of the absorber layer 140 exposed by the openings 162 are etched to form openings 142 extending through the absorber layer 140. The openings 142 expose sections of the first capping layer 120. In some embodiments, the absorber layer 140 is etched using an anisotropic etching process. In some embodiments, the anisotropic etching is a dry etching process, such as RIE, wet etching, or a combination thereof, which selectively removes the material providing the absorber layer 140 from the material providing the underlying first capping layer 120. For example, in some embodiments, the absorber layer 140 is dry etched using a gas containing chlorine, such as Cl₂ or BCl₃, or a gas containing fluorine, such as CF₄, SF₃, or NF₃. Ar can be used as a carrier gas.In some embodiments, the carrier gas may also contain oxygen (O2). The etch rate and etch selectivity depend on the etchant gas, the etchant flow rate, the power, the pressure, and the substrate temperature. After etching, the remaining sections of the absorber layer 140 form the structured absorber layer 140P. According to embodiments of the present disclosure, if the absorber layer 140 has several layers of absorber material and the individual absorber material layers have different etching properties, it is possible to etch the individual absorber material layers separately using different etchants. If the individual absorber material layers do not have different etching properties, the individual absorber material layers can be etched simultaneously.

[0052] In some embodiments, etching the absorber layer 140 also removes part of the first capping layer 120. In other embodiments, etching the absorber layer 140 does not remove any part of the first capping layer 120. The openings 142 expose sections of the underlying first capping layer 120 at the bottom of trenches formed in the absorber layer 140. After etching the absorber layer 140, the structured hard mask layer 160P is removed from the surfaces of the structured absorber layer 140P, for example, using an oxygen plasma or a wet process.

[0053] The openings 142 in the structured absorber layer 140P define the structure of openings 152 in the EUV mask 100. According to embodiments of the present disclosure, the sections of the structured first capping layer 120 exposed by the structured absorber layer 140P exhibit reduced susceptibility to carbon deposition or contamination. Furthermore, thanks to the amorphous structure of the material of the first capping layer 120, the first capping layer 120 resists weakening by etching agents, cleaning agents, or processes using such etching agents or cleaning agents carried out during the manufacture of the EUV mask 100.Such resistance to weakening by etchants, cleaning agents or processes using such etchants or cleaning agents not only extends the lifespan of the mask, but also increases the ability of the first capping layer 120 to resist penetration by oxidizing agents that can react with the underlying reflective multilayer stack, thereby forming undesirable oxides.

[0054] With reference to Fig. 2 and Fig. 3H transitions from the method 200 to an activity 220 in which a structured photoresist layer 180P, having a structure of openings 182, is formed over the structured absorber layer 140P and the first capping layer 120, according to some embodiments. Fig. 3H is a cross-sectional view of the structure of Fig. 3G after forming the structured photoresist layer 180P, which includes openings 182, over the structured absorber layer 140P and the first capping layer 120 according to some embodiments.

[0055] With reference to Fig. 3H exposes the openings 182 sections of the structured absorber layer 140P around the perimeter of the structured absorber layer 140P. The openings 182 correspond to the trenches 154 in the peripheral region 100B of the EUV mask 100 that are to be formed. To form the structured photoresist layer 180P, a photoresist layer (not shown) is applied over the first capping layer 120 and the structured absorber layer 140P. The photoresist layer fills the openings 142 in the structured absorber layer 140P. In some embodiments, the photoresist layer comprises a positive-tone photoresist material, a negative-tone photoresist material, or a hybrid-tone photoresist material. In some embodiments, the photoresist layer comprises the same material as the one described above. Fig. The photoresist layer 170 is described in 3D. In some embodiments, the photoresist layer has a material that differs from that of photoresist layer 170. In some embodiments, for example, the photoresist layer is formed by centrifugal coating. The photoresist layer is then structured by exposing the photoresist layer with a radiation pattern and, depending on whether a positive or negative resist was used, removing the exposed or unexposed sections of the photoresist layer using a resist developer. The remaining sections of the photoresist layer form the structured photoresist layer 180P.

[0056] With reference to Fig. 2 and Fig. 3I the process 200 proceeds to an activity 222 in which the structured absorber layer 140P, the first capping layer 120 and the reflective multilayer stack 110 are etched using the structured photoresist layer 180 as an etching mask to form trenches 154 in the peripheral area 100B of the substrate 102, according to some embodiments. Fig. 3I is a cross-sectional view of the structure of Fig. 3H after etching the structured absorber layer 140P, the first capping layer 120 and the reflective multilayer stack 110 to form the trenches 154 in the peripheral area 100B of the substrate 102 according to some embodiments.

[0057] With reference to Fig. The trenches 154 extend through the structured absorber layer 140P, the first capping layer 120, and the reflective multilayer stack 110 to expose the surface of the substrate 102. The trenches 154 surround the structural area 100A of the EUV mask 100, thereby separating the structural area 100A from the peripheral area 100B.

[0058] In some embodiments, the structured absorber layer 140P, the first capping layer 120, and the reflective multilayer stack 110 are etched using a single anisotropic etching process. The anisotropic etching can be a dry etching process, such as RIE, a wet etching process, or a combination thereof, selectively removing the respective materials of the structured absorber layer 140P, the first capping layer 120, and the reflective multilayer stack 110 from the material provided by the substrate 102. In other embodiments, the structured absorber layer 140P, the first capping layer 120, and the reflective multilayer stack 110 are etched using several different anisotropic etching processes. Each anisotropic etching process can be a dry etching process, such as RIE, a wet etching process, or a combination thereof.

[0059] With reference to Fig. 2 and Fig. In some embodiments, the process 200 proceeds to activity 224 in which the structured photoresist layer 180P is removed. Fig. 3J is a cross-sectional view of the structure of Fig. 3I after removal of the structured photoresist layer 180P according to some embodiments.

[0060] With reference to Fig. 3J, for example, removes the structured photoresist layer 180P from the structural region 100A and the peripheral region 100B of the substrate 102 by wet stripping or plasma ashing. Removing the structured photoresist layer 180P from the openings 142 in the structured absorber layer 140P re-exposes the surfaces of the first capping layer 120 in the structural region 100A.

[0061] In this way, an EUV mask 100 is formed. The EUV mask 100 comprises a substrate 102, a reflective multilayer stack 110 over a front surface of the substrate 102, a first capping layer 120P over the reflective multilayer stack 110, and a structured absorber layer 140P over the first capping layer 120P. The EUV mask 100 further comprises a conductive layer 104 over a rear surface of the substrate 102 opposite the front surface. According to embodiments of the present disclosure, the first capping layer 120 protects the EUV mask from carbon contamination by reducing or preventing the deposition, formation, or absorption of carbon on exposed surfaces of the first capping layer 120. As a result, the adverse effects (e.g.,The need for increased EUV energy or negative effects on the CDU due to carbon buildup or carbon contamination of an EUV mask is reduced or prevented, and a structure on the EUV mask 100 can be accurately projected onto a silicon wafer. Thanks to the amorphous structure of the material of the first capping layer 120, the first capping layer 120 resists weakening caused by etchants, cleaning agents, or processes that use such etchants or cleaning agents and are carried out during the fabrication of the EUV mask 100. This resistance to weakening caused by etchants, cleaning agents, or processes that use such etchants or cleaning agents increases the ability of the first capping layer 120 to resist penetration by oxidizing agents that can react with the underlying reflective multilayer stack, thereby forming undesirable oxides.

[0062] After removing the structured photoresist layer 180P, the EUV mask 100 is cleaned to remove any remaining contaminants. In some embodiments, the EUV mask 100 is cleaned by immersing it in an ammonium hydroxide solution (NH4OH solution). In other embodiments, the EUV mask 100 is cleaned by immersing it in a dilute hydrofluoric acid solution (HF solution).

[0063] The EUV mask 100 is then examined for any defects in structural area 100A, for example, by irradiating it with UV light at a wavelength of 193 nm. Foreign substances can be detected by diffusively reflected light. If defects are found, the EUV mask 100 is further cleaned using appropriate cleaning processes.

[0064] Fig. Figure 4 is a cross-sectional view of an EUV mask 400 according to a second embodiment of the present disclosure. The EUV mask 400 is in some respects the one described above with reference to Fig. 1 to Fig. The EUV mask 400 is similar to the EUV mask 100 described in section 3. The EUV mask 400 differs from the EUV mask 1010 in that the EUV mask 400 has a multi-layered capping feature, comprising two or more capping layers, as described in more detail below. Structures and elements common to the EUV mask 400 and the EUV mask 100 are identified by the same reference numerals, and the above description applies to these elements. With reference to Fig. 4. The EUV mask 400 comprises a substrate 102, a reflective multilayer stack 110 over a front surface of the substrate 102, a structured first capping layer 120P' over the reflective multilayer stack 110, a structured second capping layer 130P', and a structured absorber layer 140P over the second structured capping layer 130P'. The composition of the structured first capping layer 120P' of the EUV mask 400 differs from the composition of the structured second capping layer 130P'. According to embodiments of the present disclosure with respect to Fig. 4. The above description regarding the composition or material of the first capping layer 120 applies to the structured first capping layer 120P' and the structured second capping layer 130P'. In other words, the materials of the first capping layer 120P' and the second capping layer 130P' can be made from the materials described above for use in the first capping layer 120 of the embodiment of Fig. 1 to Fig. 3 described, can be selected. The EUV mask 400 further comprises a conductive layer 104 over a rear surface of the substrate 102 opposite the front surface. Although the embodiment of Fig. 4, which is illustrated and described with reference to a multilayer capping feature 125 having two capping layers, embodiments of the present disclosure include EUV masks having a multilayer capping feature with more than two capping layers, e.g. three, four or more capping layers.

[0065] Fig. Figure 5 is a flowchart of a process 500 for manufacturing an EUV mask, for example the EUV mask 400, according to some embodiments. Fig. 6A to Fig. Figure 6L shows cross-sectional views of the EUV mask 400 at various stages of the manufacturing process according to some embodiments. The process 500 is discussed in detail below with reference to the EUV mask 400. In some embodiments, additional activities are performed before, during, or after the process 500, or some of the described activities are replaced and / or eliminated. In some embodiments, some of the features described below are replaced or eliminated. A person skilled in the art would understand that although some embodiments are discussed with activities performed in a particular sequence, these activities may be performed in a different logical order.

[0066] With reference to Fig. 5 and Fig. 6A the method 500 has an activity 502 in which a reflective multilayer stack 110 is formed over a substrate 102, according to some embodiments. Fig. Figure 6A is a cross-sectional view of an initial setup of an EUV mask 400 after the formation of the reflective multilayer stack 110 over the substrate 102 according to some embodiments. The materials and formation processes for the reflective multilayer stack 110 are the same as those described above. Fig. Section 3A is described and therefore will not be described in detail here.

[0067] With reference to Fig. 5 and Fig. 6B transitions from the method 500 to an activity 504 in which a first capping layer 120' is deposited over the reflective multilayer stack 110, according to some embodiments. Fig. 6B is a cross-sectional view of the structure of Fig. 6A after the deposition of the first capping layer 120' over the reflective multilayer stack 110 according to some embodiments. The materials and formation processes for the first capping layer 120' are those described above in connection with the materials and formation of the first capping layer 120 in Fig. 3B described similarly and are therefore not described in detail here.

[0068] With reference to Fig. 5 and Fig. 6C transitions from the process 500 to an activity 506 in which a second capping layer 130' is deposited over the first capping layer 120', according to some embodiments. Fig. 6C is a cross-sectional view of the structure of Fig. 6B after the deposition of the second capping layer 130' over the first capping layer 120' according to some embodiments. In the embodiment of Fig. 6C form the first capping layer 120' and the second capping layer 130', forming the multilayer capping feature 125'.

[0069] With reference to Fig. In 6C, the second capping layer 130' is arranged on top of the first capping layer 120'. In some embodiments, the second capping layer 130' has different etching properties than an absorber layer subsequently formed on it and can therefore serve as an etch stop layer to prevent damage to the capping layer 120' during the structuring of an absorber layer. Furthermore, the second capping layer 130' can also later serve as a sacrificial layer for focused ion beam repair of defects in the absorber layer. In some embodiments, the second capping layer 130' is made of one of the materials described above, which can be used as the material for the first capping layer 120' in the embodiments of Fig. 1 to Fig. Three useful properties are selected. For example, the material of the second capping layer 130' has an element with an extinction coefficient κ in the range between 0 and 0.1 and a refractive index n between 0.87 and 0.97 with respect to EUV wavelengths. By using a material with an extinction coefficient κ and a refractive index n in these ranges, the material of capping layer 130' is able to transmit a desired amount of incident EUV light without undesirably affecting the phase of the incident EUV light.

[0070] In some embodiments, the second capping layer 130' is deposited by thermal ALD, PE-ALD, CVD, PECVD, PVD, electron beam evaporation, thermal evaporation, ion beam induced deposition, sputtering, electrodeposition, or electroless deposition. In some embodiments, the second capping layer 130' has a thickness in the range of approximately 0.5 to 5 nm. A second capping layer 130' with a thickness in the range of approximately 0.5 to 5 nm is thick enough to protect the underlying first capping layer 120' and / or the multilayer stack 110 from oxidizing agents or chemical etching agents during the masking process or the semiconductor process using the mask. If the second capping layer is 130' 0.5 to 5 nm thick, it is not so thick that it reduces EUV transmission by an undesirable amount.Embodiments according to the present disclosure are not limited to EUV masks having a second capping layer 130' with a thickness of 0.5 to about 5 nm. Embodiments according to the present disclosure include EUV masks having a second capping layer 130' with a thickness of less than 0.5 nm and EUV masks having a second capping layer 130' with a thickness of more than about 5 nm.

[0071] In some embodiments, the material of the second capping layer 130' contains elements exhibiting a solid-state carbon solubility that differs from that of the elements in the material of the first capping layer 120'. For example, in some embodiments, the solid-state carbon solubility of the element in the material of the second capping layer 130' is greater or less than the solid-state carbon solubility of the material of the first capping layer 120'. According to some embodiments of Fig. 4. The material of the second capping layer 130' includes an element having an EUV extinction coefficient that is lower than the EUV extinction coefficient of an element in the material of another layer, e.g., the first capping layer 120' of the multilayer capping feature 125'. In other embodiments of Fig. 4. The element of the material of the second capping layer 130' has an EUV extinction coefficient for EUV radiation with a wavelength of 13.5 nm that is greater than the EUV extinction coefficient for EUV radiation with a wavelength of 13.5 nm of an element of the material of the first capping layer 120' of the multilayer capping feature 125'. In addition, the materials for use in the second capping layer 130' of the multilayer capping features according to the present embodiment show good adhesion to the first capping layer 120' as well as to materials deposited on the second capping layer 130'.

[0072] The formation processes for the second capping layer 130' are those described above in connection with the formation of the first capping layer 120. Fig. 3C, which were described, are similar and therefore will not be described in detail.

[0073] With reference to Fig. 5 and Fig. 6D the process 500 goes to an activity 508 in which an absorber layer 140 is deposited over the second capping layer 130' according to various embodiments. Fig. 6D is a cross-sectional view of the structure of Fig. 6C after the deposition of the absorber layer 140 over the second capping layer 130' according to some embodiments. The materials and formation processes for the absorber layer 140 are described above. Fig. 3C described similarly and are therefore not described in detail here.

[0074] With reference to Fig. 5 and Fig. 6E transitions from method 500 to activity 509 in which a resist stack comprising a hard mask 120 and a photoresist layer 170 is deposited over the absorber layer 140, according to some embodiments. Fig. 6E is a cross-sectional view of the structure of Fig. 6D after the successive deposition of the hard mask layer 160 and the photoresist layer 170 over the absorber layer 140 according to some embodiments. The respective materials and formation processes for the hard mask layer 160 and the photoresist layer 170 are described in Fig. 3D models are similar and therefore will not be described in detail here.

[0075] With reference to Fig. 5 and Fig. 6F transitions from the process 500 to an activity 510 in which the photoresist layer 170 is lithographically structured to form a structured photoresist layer 170P, according to some embodiments. Fig. 6F is a cross-sectional view of the structure of Fig. 6E after lithographic structuring of the photoresist layer 170 to form the structured photoresist layer 170P according to some embodiments. The etching processes for the photoresist layer 170 are those described in Fig. 3E described similarly and are therefore not described in detail here.

[0076] With reference to Fig. 5 and Fig. 6G transitions the process 500 to an activity 512 in which the hard mask layer 160 is etched using the structured photoresist layer 170' as an etching mask to form a structured hard mask layer 160P, according to some embodiments. Fig. 6G is a cross-sectional view of the structure of Fig. 6F after etching the hard mask layer 160 to form the structured hard mask layer 160P according to some embodiments. The etching processes for the hard mask layer 160 are those described in Fig. 3F described similarly and are therefore not described in detail here.

[0077] With reference to Fig. 5 and Fig. 6G transitions from method 500 to activity 514, in which the absorber layer 140 is etched using the structured hard mask layer 160P as an etching mask to form a structured absorber layer 140P, according to some embodiments. Fig. 6H is a cross-sectional view of the structure of Fig. 6G after etching the absorber layer 140 to form the structured absorber layer 140P according to some embodiments. The etching processes for the absorber layer 140 are those described in Fig. 3G described similarly and are therefore not described in detail here. The structured absorber layer 140P has several openings 142 that expose the underlying second capping layer 130'. After etching the absorber layer 140, the structured hard mask layer 160P is removed from the surfaces of the structured absorber layer 140P, for example, using an oxygen plasma or a wet process. The resulting structure is shown in Fig. 61 shown.

[0078] In some embodiments according to Fig. 4 to Fig. 6. The steps of etching the absorber layer 140 to form the structured absorber layer 140P, and / or the step of removing the photoresist layer 170 and / or the structured hard mask layer 160P, can remove parts of an upper surface of the second capping layer 130'. Such embodiments are described in Fig. 4, represented by reference numeral 131, wherein a portion of the structured second capping layer 130P' is removed by the step of etching the absorber layer 140 or the step of removing the photoresist layer 170 and / or the structured hard mask layer 160P. According to some embodiments in which a portion of the upper surface of the structured second capping layer 130P' is removed, a portion of the upper surface of the structured second capping layer 130P' remains; for example, at least a few nanometers of the structured second capping layer 130P' remain. Examples of a few nanometers include 1 to 2 nm. In other embodiments according to Fig. 4 to Fig. 6. The steps of etching the absorber layer 140 to form the structured absorber layer 140P do not eliminate, and / or the step of removing the photoresist layer 170 and / or the structured hard mask layer 160P does not eliminate any part of the second capping layer 130'. Such embodiments are described in Fig. 4 represented by reference numeral 133. Fig. Figure 6I shows an embodiment in which none of the second capping layer 130' was removed by the steps of removing the absorber layer, the photoresist or the hard mask.

[0079] With reference to Fig. 5 and Fig. 6J the process 500 proceeds to an activity 516 in which a structured photoresist layer 180P, having a structure of openings 182, is formed over the structured absorber layer 140P and the second capping layer 130', according to some embodiments. Fig. 6J is a cross-sectional view of the structure of Fig. 6I after forming the structured photoresist layer 180P, which has openings 182, over the structured absorber layer 140P and the second capping layer 130' according to some embodiments. The materials and manufacturing processes for the structured photoresist layer 180P are those described in Fig. 3H described similarly and are therefore not described in detail here.

[0080] With reference to Fig. 5 and Fig. In 6K, the process 500 is transferred to an activity 518 in which the structured absorber layer 140P, the second capping layer 130', the first capping layer 120' and the reflective multilayer stack 110 are etched using the structured photoresist layer 180P as an etching mask to form trenches 154 in the peripheral area 100B of the substrate 102, according to some embodiments. Fig. 6K is a cross-sectional view of the structure of Fig. 6J after etching the structured absorber layer 140P, the second capping layer 130', the first capping layer 120' and the reflective multilayer stack 110 to form the trenches 154 in the peripheral area 100B of the substrate 102 according to some embodiments.

[0081] With reference to Fig. The trenches 152 extend 6K through the structured absorber layer 140P, the second capping layer 130', the first capping layer 120', and the reflective multilayer stack 110 to expose the surface of the substrate 102. The trenches 152 surround the structural area 100A of the EUV mask 100, thus separating the structural area 100A from the peripheral area 100B.

[0082] In some embodiments, the structured absorber layer 140P, the second capping layer 130', the first capping layer 120', and the reflective multilayer stack 110 are etched using a single anisotropic etching process. The anisotropic etching can be dry etching, such as RIE, wet etching, or a combination thereof, selectively etching the respective materials of the structured absorber layer 140P, the second capping layer 130', the first capping layer 120', and the reflective multilayer stack 110 relative to the material provided by the substrate 102. In some embodiments, the structured absorber layer 140P, the second capping layer 130', the first capping layer 120', and the reflective multilayer stack 110 are etched using several different anisotropic etching processes.Any anisotropic etching process can be a dry etching such as, for example, a RIE, a wet etching, or a combination thereof.

[0083] With reference to Fig. 5 and Fig. 6L transitions from process 500 to activity 520 in which the structured photoresist layer 180P is removed, according to some embodiments. Fig. 6L is a cross-sectional view of the structure of Fig. 6K after removal of the structured photoresist layer 180P according to some embodiments.

[0084] With reference to Fig. In step 6L, the structured photoresist layer 180P is removed from the feature area 100A and the peripheral area 100B of the substrate 102, for example, by wet stripping or plasma ashing. Removing the structured photoresist layer 180P from the openings 142 in the structured absorber layer 140P exposes the surfaces of the second capping layer 130' in feature area 100A. The openings 142 in the structured absorber layer 140P define the structure of openings in the EUV mask 400, which correspond to circuit structures to be formed on a semiconductor wafer.

[0085] In this way, an EUV mask 400 is formed. The EUV mask 400 comprises a substrate 102, a reflective multilayer stack 110 over a front surface of the substrate 102, a first structured capping layer 120P' over the reflective multilayer stack 110, a second structured capping layer 130P' over the first structured capping layer 120P', and a structured absorber layer 140P over the second structured capping layer 130P'. The EUV mask 400 further comprises a conductive layer 104 over a rear surface of the substrate 102 opposite the front surface. According to embodiments of Fig. 4 to Fig. 6. The second capping layer 130' is resistant to carbon contamination and protects the underlying first capping layer 120' and the reflective multilayer stack 110 from carbon contamination by reducing or preventing carbon deposition, formation, or absorption on exposed surfaces of the second capping layer 130'. As a result, the adverse effects (e.g., the need for increased EUV energy or negative effects on the CDU) caused by carbon formation on or carbon contamination of an EUV mask are reduced or prevented, and a structure on the EUV mask 100 can be accurately projected onto a silicon wafer.Thanks to the amorphous structure of the material of the first capping layer 120' and / or the second capping layer 130', the first capping layer 120' and / or the second capping layer 130' resist weakening caused by etchants, cleaning agents, or processes using such etchants or cleaning agents during the manufacture of the EUV mask 400. This resistance to weakening caused by etchants, cleaning agents, or processes using such etchants or cleaning agents increases the ability of the first capping layer 120' and the second capping layer 130' to resist penetration by oxidizing agents that can react with the underlying reflective multilayer stack, forming undesirable oxides.

[0086] After removing the structured photoresist layer 180P, the EUV mask 400 is cleaned to remove any remaining contaminants. In some embodiments, the EUV mask 400 is cleaned by immersing it in an ammonium hydroxide solution (NH4OH solution). In other embodiments, the EUV mask 400 is cleaned by immersing it in a dilute hydrofluoric acid solution (HF solution).

[0087] The EUV mask 400 is then examined for any defects in structural area 100A, for example, by irradiating it with UV light at a wavelength of 193 nm. Foreign substances can be detected by diffusively reflected light. If defects are found, the EUV mask 400 is further cleaned using appropriate cleaning processes.

[0088] Fig. Figure 7 shows a method 1200 for using an EUV mask according to embodiments of the present disclosure. The method 1200 comprises a step 1202 in which an EUV mask is exposed to incident radiation, e.g., EUV radiation. An example of an EUV mask useful in step 1202 includes the EUV mask 100 or 400 described above. In step 1204, a portion of the incident radiation is absorbed in a structured absorber layer of the EUV mask. In step 1206, a portion of the incident radiation is transmitted through a capping layer having an amorphous structure. An example of a capping layer having an amorphous structure includes the first capping layer 120 described above with reference to Fig. 1 to Fig. 3. In an optional step 1208, which relates to a method employing a multilayer capping feature according to embodiments of the present disclosure, a portion of the incident radiation is transmitted through a second capping layer having a second carbon solubility in a solid state or a second EUV extinction property that differs from the first carbon solubility or the first EUV extinction property of the first capping layer. Examples of capping layers having a second carbon solubility in a solid state or a second EUV extinction property include the first capping layer 120' or the second capping layer 130' described above. In step 1209, a portion of the incident radiation is reflected by the reflecting multilayer stack.In step 1210, a portion of the incident radiation reflected by the reflective multilayer stack is directed toward the material to be patterned. In the embodiment omitting optional step 1208, the reflected incident radiation is retransmitted through the first capping layer, which has an amorphous structure. In the embodiment including optional step 1208, the reflected incident radiation is retransmitted through the first and second capping layers on its path to the material to be patterned. After the material to be patterned has been exposed with the radiation reflected by the EUV mask, in step 1212, sections of the material that were exposed or not exposed with the radiation reflected by the EUV mask are removed.

[0089] Fig. Figure 8 shows a method 800 for using an EUV mask according to embodiments of the present disclosure. The method 800 comprises a step 802 in which an EUV mask is exposed to incident radiation, e.g., EUV radiation. An example of an EUV mask useful in step 802 includes the EUV masks 400 described above. In step 804, a portion of the incident radiation is absorbed in a structured absorber layer of the EUV mask. In step 806, a quantity of a first portion of the incident radiation is absorbed in the first capping layer, which has an element with a first carbon solubility in a solid state and a first EUV extinction coefficient. An example of a capping layer having a first carbon solubility and a first EUV extinction property includes the second capping layers 130' described above.In step 808, a portion of a second part of the incident radiation is absorbed by a second capping layer comprising an element with a second carbon solubility in a solid state and / or a second EUV extinction coefficient, which differs from the first carbon solubility in a solid state and / or the first EUV extinction coefficient. In some embodiments, the amount of the first part of the incident radiation absorbed by the first capping layer differs from the amount of incident radiation absorbed by the second capping layer. Examples of the second capping layer include the first capping layers described above in 120'. In step 809, a portion of the incident radiation is reflected by the reflecting multilayer stack.In step 810, a portion of the incident radiation reflected by the reflective multilayer stack is directed toward the material to be patterned. The reflected incident radiation is then transferred back through the first and second capping layers on its path to the material to be patterned. After the material to be patterned has been exposed with the radiation reflected by the EUV mask, in step 812, sections of the material that were exposed or not exposed with the radiation reflected by the EUV mask are removed.

[0090] Fig. Figure 9 shows the results of an analysis of the thickness of the carbon impurity on a capping feature containing an rhr-containing alloy, e.g., RuRh, according to embodiments of the present disclosure. As in Fig. As shown in Figure 9, the thickness of the carbon impurity is on the order of 6.5 nm. In contrast, it was observed that the thickness of the carbon impurity on a capping feature not formed according to the present disclosure and subjected to the same lithographic conditions as the capping feature of Fig. 9, which was exposed, was larger and, for example, on the order of 11.7 nm. Thus, capping layers according to the present disclosure achieve an approximately 40% reduction in the thickness of the carbon impurity.

[0091] One aspect of this description concerns an EUV mask. The EUV mask comprises a substrate, a reflective multilayer stack on the substrate, and a capping feature on the reflective multilayer stack. The capping feature includes a first capping layer composed of a material with an amorphous structure. In some embodiments, the amorphous structure has a nanocrystalline structure with a grain size of less than 2 nm. The EUV mask also includes a structured absorber layer on the multilayer capping feature. In some embodiments, the first capping layer comprises a material containing an element with a carbon solubility in the solid state at a eutectic point of a system containing the element and carbon of less than 3 at%.Such EUV masks exhibit a reduced tendency for carbon accumulation or contamination, which can adversely affect the mask's ability to create structures that meet critical dimensional criteria. Furthermore, these EUV capping features demonstrate resistance to degradation caused by etching agents or cleaning agents to which the capping layer is exposed during EUV mask manufacturing.

[0092] Another aspect of this description concerns a method for using an EUV mask. The method involves exposing an EUV mask to incident radiation. The EUV mask has a substrate, a reflective multilayer stack on the substrate, and a multilayer capping feature on the reflective multilayer stack. The multilayer capping feature has a first capping layer containing a rh, ir, pt, au, or zr-containing first alloy, and a second capping layer containing a rh, ir, pt, au, or zr-containing second alloy that is different from the first alloy. The EUV mask has a structured absorber layer on the multilayer capping feature. The method involves absorbing a portion of the incident radiation in the structured absorber layer. A portion of the incident radiation is transmitted through the first capping layer and the second capping layer.Part of the incident radiation is reflected by the reflecting multilayer stack and directed towards the material to be structured. In some embodiments, the first and second alloys are selected from RuZr, IrZr, RhZr, HfZr and NbZr, respectively, with the Zr content of the first and second alloys being at least 5 at.%.

[0093] Another aspect of this description concerns a different method for using an EUV mask. This method involves exposing the EUV mask to incident radiation. The EUV mask comprises a substrate, a reflective multilayer stack on the substrate, a capping feature, and a structured absorber layer on the capping feature. The capping feature comprises a material containing an element with a carbon solubility in the solid state at a eutectic point of a system containing the element and carbon of less than 3 at%. The method further involves absorbing a portion of the incident radiation in the structured absorber layer. In this method, a portion of the incident radiation is absorbed in the capping layer.The process continues with the reflection of part of the incident radiation from the reflecting multilayer stack and its direction onto a material that is to be structured.

[0094] In the foregoing, features of several embodiments were explained to enable those skilled in the art to better understand the aspects of the present disclosure. Those skilled in the art should recognize that they can readily use the present disclosure as a basis for designing or modifying other processes and setups to achieve the same purposes and / or the same advantages as the embodiments presented herein. They should also recognize that such equivalent setups do not deviate from the spirit and scope of the present disclosure, and that they can make various changes, substitutions, and modifications therein without departing from the spirit and scope of the present disclosure. 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] US 63282289

[0001]

Claims

[1] Extreme ultraviolet mask (EUV mask), featuring a substrate; a reflective multilayer stack on the substrate; a capping feature on the reflective multilayer stack, wherein the capping feature has a first capping layer having a material with an amorphous structure; and a structured absorber layer on the capping feature [2] EUV mask according to claim 1, wherein the amorphous structure has a nanocrystalline structure with a grain size of less than 5 nanometers. [3] EUV mask according to claim 1, wherein the amorphous structure has a nanocrystalline structure with a grain size of less than 2 nanometers. [4] EUV mask according to one of the preceding claims, wherein the capping feature further comprises a second capping layer having a material with an amorphous structure, wherein the material of the second capping layer differs from the material of the first capping layer. [5] EUV mask according to claim 4, wherein the material of the first capping layer comprises an element having an EUV extinction coefficient for EUV radiation with a wavelength of 13.5 nm that differs from an EUV extinction coefficient for EUV radiation with a wavelength of 13.5 nm of an element of the material of the second capping layer. [6] EUV mask according to claim 5, wherein the EUV extinction coefficient for EUV radiation with a wavelength of 13.5 nm of the element of the material of the first capping layer is between 0 and 0.

1. [7] EUV mask according to claim 5, wherein the EUV extinction coefficient for EUV radiation with a wavelength of 13.5 nm of the element of the material of the second capping layer is between 0 and 0.

1. [8] EUV mask according to any one of the preceding claims 4 to 7, wherein the material of the first capping layer comprises an element having a carbon solubility in a solid state at a eutectic point of a system containing the element and carbon of less than 3 at%. [9] EUV mask according to any one of the preceding claims 4 to 8, wherein the material of the second capping layer comprises an element having a carbon solubility in a solid state at a eutectic point of a system containing the element and carbon of less than 3 at%. [10] EUV mask according to any of the preceding claims, wherein the material of the first capping layer is selected from alloys containing one or more elements selected from Rh, Ir, Pt, Au and Zr. [11] EUV mask according to any one of the preceding claims 4 to 10, wherein the material of the second capping layer is selected from alloys containing one or more elements selected from Rh, Ir, Pt, Au and Zr, or alloys thereof. [12] EUV mask according to claim 10, wherein the alloy of the first capping layer further comprises HF, Nb or N. [13] EUV mask according to claim 11, wherein the alloy of the second capping layer further comprises HF, Nb or N. [14] Method for using an EUV mask, wherein the method an exposure of the EUV mask with incident radiation, whereby the EUV mask a substrate, a reflective multilayer stack on the substrate; a multi-layer capping feature on the reflective stack, wherein the multi-layer capping feature comprises a first capping layer having a first alloy containing Rh, Ir, Pt, Au or Zr, and a second capping layer having a second alloy containing Rh, Ir, Pt, Au or Zr that is different from the first alloy; and features a structured absorber layer on the multilayer capping feature; an absorption of part of the incident radiation in the structured absorber layer; a transmission of part of the incident radiation through the first capping layer and the second capping layer; a reflection of part of the incident radiation from the reflecting multilayer stack; and This involves directing a portion of the incident radiation, which is reflected by the reflecting multilayer stack, towards a material that is to be structured. [15] Method according to claim 14, wherein the first alloy and the second alloy are selected from RuZr, IrZr, RhZr, HfZr and NbZr, wherein the Zr content of the first alloy and the second alloy is at least 5 at%. [16] Method according to claim 14, wherein the first alloy and the second alloy are selected from RuRh, RuIr, RuPt, PtIr, RuIrPt, NbIr, NbPt, NbRh, RhN, IrN, RuRhN, RuIrN, RuPtN, PtIrN, RuIrPtN, NbIrN, NbPtN and NbRhN. [17] Structuring procedures, comprehensive an exposure of an EUV mask with incident radiation, wherein the EUV mask a substrate, a reflective multilayer stack on the substrate; a capping feature on the reflective multilayer stack, wherein the capping feature comprises a material that includes an element with a carbon solubility in a solid state at a eutectic point of a system of the element and carbon of less than 3 at%; and has a structured absorber layer on the capping feature; an absorption of part of the incident radiation in the structured absorber layer; an absorption of a portion of the incident radiation in the capping feature; a reflection of a portion of the incident radiation from the reflecting multilayer stack; and Directing a portion of the incident radiation, which is reflected by the reflecting multilayer stack, towards a material that is to be structured. [18] Method according to claim 17, wherein the material of the capping feature comprises RuZr, IrZr, RhZr, HfZr or NbZr, wherein the Zr content is at least 5 at%. [19] Method according to claim 17, wherein the material of the capping feature is an alloy selected from RuRh, RuIr, RuPt, PtIr, RuIrPt, NbIr, NbPt, NbRh, RhN, IrN, RuRhN, RuIrN, RuPtN, PtIrN, RuIrPtN, NbIrN, NbPtN and NbRhN. [20] Method according to any one of the preceding claims 17 to 19, wherein the carbon solubility in a solid state at the eutectic point is less than 2 at%.

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