Phase-shifting masks for extreme ultraviolet lithography and their fabrication methods

Abstract

This invention provides a phase-shifting mask for extreme ultraviolet (EUV) lithography and its manufacturing method. The phase-shifting mask includes: a substrate, an etching stop layer, a patterned layer, a multilayer film, and a protective layer. The etching stop layer is formed on the substrate. The patterned layer is formed on the etching stop layer and includes a phase-shifting step structure with a predetermined depth formed by etching. The multilayer film is continuously formed on the patterned layer with the phase-shifting step structure. The phase-shifting step structure cooperates with the multilayer film covering the phase-shifting step structure to perform phase modulation of EUV light in different regions. The protective layer is formed on the multilayer film. This method eliminates the need for an absorber structure, which helps reduce the three-dimensional mask effect caused by oblique incidence and structural height. It avoids patterned etching of the multilayer film itself, which helps mitigate problems such as multilayer film interface damage, increased roughness, interlayer diffusion, and decreased reflectivity, thus balancing phase modulation capability, reflectivity, and structural stability.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a phase-shifting mask for extreme ultraviolet lithography and a method for manufacturing the same. Background Technology

[0002] Currently, extreme ultraviolet (EUV) lithography uses UV light with a wavelength of approximately 13.5 nm for exposure and is one of the key technologies in advanced integrated circuit manufacturing. Unlike the transmissive masks commonly used in deep ultraviolet (DUV) lithography, EUV lithography typically employs reflective mask structures and defines the exposure pattern by forming absorber patterns on multilayer films. With the continuous reduction in feature sizes of semiconductor devices and the increasing numerical aperture of projection optics systems, EUV lithography places higher demands on mask imaging quality, especially in terms of imaging contrast, edge slope, depth of focus, and critical dimension control. However, in practical applications, EUV light is usually incident on the mask surface at a certain angle, and the absorber layer itself has a certain thickness. Therefore, the mask is prone to significant three-dimensional effects, including shadowing effects, phase errors, and image position shifts caused by mask topographic undulations. These three-dimensional effects further lead to decreased imaging contrast, increased imaging deviations in different directions, uneven distribution of critical dimensions, and narrowing of the process window, thus limiting the stable transfer of high-resolution patterns.

[0003] Phase-shifting masks are considered a promising technology for improving the imaging resolution of extreme ultraviolet (EUV) lithography and mitigating mask 3D effects. The basic principle is to enhance the intensity gradient at the image plane edges by adjusting the optical path difference or phase difference introduced by different regions of the mask to incident EUV light, thereby increasing the normalized image logarithmic slope, improving spatial image contrast, and providing structural-level control over image quality. Compared to traditional absorber masks, this method offers advantages in improving the imaging performance of fine patterns, enhancing image fidelity, and expanding the process window.

[0004] Current research on extreme ultraviolet (EUV) phase-shifting masks mainly focuses on two technical approaches. The first is the attenuation-type phase-shifting scheme, which involves depositing a low-refractive-index absorber material on the surface of a multilayer film and achieving phase modulation through local complex reflectivity modulation. This approach essentially still relies on the absorber structure; although the absorber thickness is reduced, it is still difficult to completely avoid the three-dimensional mask effect caused by the structure height under oblique incidence conditions. Simultaneously, there are still issues regarding optical matching, interface stability, and interface mixing suppression between the low-refractive-index absorber material and the multilayer film, requiring further research into related material systems and process conditions. The second approach is the multilayer film etching-type phase-shifting route, which involves directly etching a molybdenum / silicon multilayer film to form a stepped structure, utilizing the structural height difference in different regions to introduce an equivalent optical path difference to obtain the target phase difference. Although this route can directly construct a phase-shifting structure in the multilayer film, the molybdenum / silicon multilayer film consists of a large number of nanoscale periodic layers, placing high demands on the precision of etching depth control, interlayer interface preservation, and etching uniformity, making the process difficult to implement. Furthermore, extreme ultraviolet light is extremely sensitive to the surface and interface roughness of multilayer films, with common roughness requirements reaching the sub-nanometer level. If interface damage, increased roughness, or intensified interlayer diffusion are introduced during the etching process, it may lead to a decrease in reflectivity, an increase in scattering loss, and a deterioration in phase modulation accuracy, thereby further affecting the mask imaging performance and long-term stability.

[0005] Therefore, a new phase-shifting mask structure and its manufacturing method for extreme ultraviolet lithography are needed to reduce the three-dimensional effect of the mask, while taking into account phase modulation capability, reflection characteristics and structural stability, thereby improving imaging performance. This is the key to the development of extreme ultraviolet lithography mask technology. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a phase-shifting mask for extreme ultraviolet (EUV) lithography and its manufacturing method. The phase-shifting mask is constructed by setting an etchable stop layer and an etchable patterned layer on a substrate, pre-constructing a phase-shifting step structure with a predetermined depth in the patterned layer, and then continuously forming a multilayer film and a protective layer on top of it. Thus, the phase-shifting step structure and the multilayer film together constitute an EUV reflective phase-shifting structure. This structure eliminates the need for direct patterned etching of the multilayer film, enabling EUV phase modulation while reducing the three-dimensional mask effect in traditional absorber-type phase-shifting structures. It also reduces problems such as multilayer film interface damage, interlayer diffusion, increased roughness, and degradation of reflective performance, thereby improving imaging performance and mask structure stability.

[0007] In a first aspect, embodiments of the present invention provide a phase-shifting mask for extreme ultraviolet (EUV) lithography. The phase-shifting mask for EUV lithography includes: a substrate, an etching stop layer, a pattern layer, a multilayer film, and a protective layer; the etching stop layer is formed on the substrate; the pattern layer is formed on the etching stop layer, and the pattern layer includes a phase-shifting step structure with a predetermined depth formed by etching; the multilayer film is continuously formed on the pattern layer with the phase-shifting step structure, and the phase-shifting step structure cooperates with the multilayer film covering the phase-shifting step structure to perform phase modulation of EUV light in different regions; the protective layer is formed on the multilayer film.

[0008] In optional embodiments of this application, the substrate includes: a low thermal expansion material substrate, a silicon substrate, a glass substrate, a quartz substrate, a ceramic substrate, or a combination of substrates; the etching stop layer includes a single layer, an oxide layer, a nitride layer, an oxynitride layer, or a combination layer formed of at least one element; wherein the element of the etching stop layer includes at least one of the following: aluminum, hafnium, zirconium, titanium, chromium, tantalum, or ruthenium; the pattern layer includes a single layer, an oxide layer, a nitride layer, an oxynitride layer, or a combination layer formed of at least one element; wherein the element of the pattern layer includes at least one of the following: silicon, tantalum, titanium, hafnium, zirconium, aluminum, chromium, or carbon; the protective layer includes a single layer, an alloy layer, a compound layer, or a combination layer formed of at least one element; wherein the element of the protective layer includes at least one of the following: ruthenium, silicon, zirconium, molybdenum, titanium, or tantalum.

[0009] In optional embodiments of this application, the etching stop layer includes at least one of the following: an aluminum oxide layer, a hafnium oxide layer, a zirconium oxide layer, a titanium oxide layer, an aluminum nitride layer, a titanium nitride layer, a chromium nitride layer, or a ruthenium layer; the patterning layer includes at least one of the following: a silicon oxide layer, a silicon nitride layer, a titanium oxide layer, a tantalum oxide layer, a tantalum nitride layer, a chromium nitride layer, a chromium oxynitride layer, an aluminum oxide layer, or an amorphous carbon layer; the protective layer includes at least one of the following: a ruthenium layer, a ruthenium-based alloy layer, a silicon-containing layer, or a composite structure.

[0010] In an optional embodiment of this application, the multilayer film includes: an alternately stacked first reflective layer and a second reflective layer; wherein the first reflective layer and the second reflective layer each include an element, alloy, or compound formed of at least one element; wherein the elements of the first reflective layer and the second reflective layer each include at least one of the following: molybdenum, silicon, ruthenium, beryllium, carbon, niobium, rhodium, or palladium.

[0011] In optional embodiments of this application, an interface control layer, a diffusion barrier layer, a hybrid layer, or a combination layer is provided between the first reflective layer and the second reflective layer; the interface control layer is used to improve the interface bonding state, interface stability, or interface reflection characteristics; the diffusion barrier layer is used to suppress interlayer diffusion or improve thermal stability; the hybrid layer is a transition layer formed by the mutual penetration of the first reflective layer material and the second reflective layer material at the interface.

[0012] Secondly, embodiments of the present invention also provide a method for manufacturing a phase-shifting mask for extreme ultraviolet lithography, for manufacturing the aforementioned phase-shifting mask for extreme ultraviolet lithography, the method comprising: providing a substrate; forming an etching stop layer on the substrate; forming a pattern layer on the etching stop layer; forming a resist layer on the pattern layer; performing patterned etching on the pattern layer using the resist layer as a mask to form a pattern layer with a phase-shifting step structure; removing the resist layer; forming a multilayer film on the pattern layer with the phase-shifting step structure; and forming a protective layer on the multilayer film to obtain a phase-shifting mask.

[0013] In an optional embodiment of this application, the step of forming an etching stop layer on the substrate includes: forming an etching stop layer on the substrate using an atomic layer deposition method.

[0014] In optional embodiments of this application, the above-mentioned photoresist layer includes: an electron beam photoresist layer; the electron beam photoresist layer includes at least: polymethyl methacrylate photoresist and / or styrene polymer photoresist.

[0015] In an optional embodiment of this application, the step of patterning the pattern layer using the resist layer as a mask includes: exposing and developing the resist layer, and etching the pattern layer using the developed resist layer as a mask.

[0016] In optional embodiments of this application, the step of removing the resist layer includes: removing the resist layer using an oxygen plasma cleaning process; the step of forming a multilayer film on a patterned layer with a phase-shifting step structure includes: depositing a multilayer film on a patterned layer with a phase-shifting step structure using a magnetron sputtering process.

[0017] The embodiments of the present invention bring the following beneficial effects: This invention provides a phase-shifting mask for extreme ultraviolet (EUV) lithography and its manufacturing method. By pre-constructing a phase-shifting step structure in a patterned layer and continuously forming multiple films on it, different regions form different equivalent optical paths, thereby creating a predetermined phase difference between the EUV reflected light from different regions. Compared with schemes that rely on absorbers to achieve phase-shifting modulation, this invention does not require an absorber structure, which helps reduce the three-dimensional effect of the mask caused by oblique incidence and structural height. Compared with schemes that directly etch multiple films to form a phase-shifting structure, this embodiment avoids patterned etching of the multiple films themselves, which helps reduce problems such as multilayer interface damage, increased roughness, interlayer diffusion, and decreased reflectivity, thus balancing phase modulation capability, reflectivity, and structural stability.

[0018] Other features and advantages of this disclosure will be set forth in the following description, or some features and advantages may be inferred from the description or determined without doubt, or may be learned by practicing the techniques described above.

[0019] To make the above-mentioned objects, features and advantages of this disclosure more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of a phase-shifting mask for extreme ultraviolet lithography provided in an embodiment of the present invention; Figure 2 A flowchart illustrating a method for manufacturing a phase-shifting mask for extreme ultraviolet lithography, provided as an embodiment of the present invention; Figure 3 This is a comparative schematic diagram of an existing extreme ultraviolet mask structure provided in an embodiment of the present invention; Figure 4 This is a schematic diagram illustrating different patterns that can be formed using a phase-shifting mask, as provided in an embodiment of the present invention. Figure 5 This is a schematic diagram illustrating the imaging effects corresponding to different pattern types provided in an embodiment of the present invention; Figure 6 This is a schematic diagram illustrating a phase-shifting mask manufacturing process and the formation of a phase-shifting step structure, provided by an embodiment of the present invention. Figure 7 This is a schematic diagram of a multilayer film continuously formed on a phase-shift step structure and further forming a protective layer, as provided in an embodiment of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Currently, there is a need for a new phase-shifting mask structure and its manufacturing method for extreme ultraviolet (EUV) lithography to reduce the three-dimensional effect of the mask while taking into account phase modulation capability, reflection characteristics and structural stability, thereby improving imaging performance. This is the key to the development of EUV lithography mask technology.

[0024] Based on this, the present invention provides a phase-shifting mask for extreme ultraviolet lithography and its manufacturing method, specifically providing an extreme ultraviolet reflective phase-shifting mask based on prefabricated steps in a patterned layer and its manufacturing method, which is applied in the fields of semiconductor manufacturing and lithography masks. By prefabricating a phase-shifting step structure in a patterned layer and continuously forming multiple layers of films and protective layers thereon, the phase modulation of extreme ultraviolet light is achieved by utilizing the structural height difference.

[0025] To facilitate understanding of this embodiment, a phase-shifting mask for extreme ultraviolet lithography disclosed in this embodiment of the invention will first be described in detail.

[0026] Example 1: This invention provides a phase-shifting mask for extreme ultraviolet lithography, see [link to relevant documentation]. Figure 1 The diagram shows a schematic of a phase-shifting mask for extreme ultraviolet (EUV) lithography. The mask includes a substrate, an etching stop layer, a pattern layer, a multilayer film, and a protective layer. The etching stop layer is formed on the substrate. The pattern layer is formed on the etching stop layer and includes a phase-shifting step structure with a predetermined depth formed by etching. The multilayer film is continuously formed on the pattern layer with the phase-shifting step structure. The phase-shifting step structure cooperates with the multilayer film covering the phase-shifting step structure to modulate the phase of EUV light in different regions. The protective layer is formed on the multilayer film.

[0027] The phase-shifting step structure in this embodiment may include a step region and a non-step region. After the step region and the non-step region are continuously covered by a multilayer film, they form a reflection region with different equivalent optical paths, so that a preset phase difference is formed between the extreme ultraviolet reflected light of adjacent regions.

[0028] The aforementioned preset phase difference can be a phase difference that can enhance the interference effect of adjacent reflection regions, preferably a phase difference close to 180°.

[0029] In this embodiment, the phase-shifting mask can be a reflective phase-shifting mask that does not rely on an absorber to achieve phase-shifting functionality. The phase modulation can be determined by the phase-shifting step structure and the extreme ultraviolet reflection characteristics of the multilayer film covering it.

[0030] In some embodiments, the substrate includes: a low thermal expansion material substrate, a silicon substrate, a glass substrate, a quartz substrate, a ceramic substrate, or a combination of substrates; the etching stop layer includes a single layer, an oxide layer, a nitride layer, an oxynitride layer, or a combination layer formed of at least one element; wherein the element of the etching stop layer includes at least one of the following: aluminum, hafnium, zirconium, titanium, chromium, tantalum, or ruthenium; the pattern layer includes a single layer, an oxide layer, a nitride layer, an oxynitride layer, or a combination layer formed of at least one element; wherein the element of the pattern layer includes at least one of the following: silicon, tantalum, titanium, hafnium, zirconium, aluminum, chromium, or carbon; the protective layer includes a single layer, an alloy layer, a compound layer, or a combination layer formed of at least one element; wherein the element of the protective layer includes at least one of the following: ruthenium, silicon, zirconium, molybdenum, titanium, or tantalum.

[0031] In some embodiments, the etching stop layer includes at least one of the following: an aluminum oxide layer, a hafnium oxide layer, a zirconium oxide layer, a titanium oxide layer, an aluminum nitride layer, a titanium nitride layer, a chromium nitride layer, or a ruthenium layer; the patterning layer includes at least one of the following: a silicon oxide layer, a silicon nitride layer, a titanium oxide layer, a tantalum oxide layer, a tantalum nitride layer, a chromium nitride layer, a chromium oxynitride layer, an aluminum oxide layer, or an amorphous carbon layer; the protective layer includes at least one of the following: a ruthenium layer, a ruthenium-based alloy layer, a silicon-containing layer, or a composite structure.

[0032] In some embodiments, the multilayer film includes: alternatingly stacked first reflective layers and second reflective layers; wherein both the first reflective layer and the second reflective layer include an element, alloy, or compound formed of at least one element; wherein the elements of both the first reflective layer and the second reflective layer include at least one of the following: molybdenum, silicon, ruthenium, beryllium, carbon, niobium, rhodium, or palladium.

[0033] In some embodiments, an interface control layer, a diffusion barrier layer, a hybrid layer, or a combined layer is provided between the first reflective layer and the second reflective layer; the interface control layer is used to improve the interface bonding state, interface stability, or interface reflection characteristics; the diffusion barrier layer is used to suppress interlayer diffusion or improve thermal stability; the hybrid layer is a transition layer formed by the mutual penetration of the first reflective layer material and the second reflective layer material at the interface.

[0034] The substrate in this embodiment may include a low thermal expansion material substrate, a silicon substrate, a glass substrate, a quartz substrate, a ceramic substrate, or a combination thereof, and is more preferably a low thermal expansion material substrate and a silicon substrate.

[0035] The etching stop layer in this embodiment may include a single layer, oxide layer, nitride layer, oxynitride layer or combination layer formed of one or more elements selected from aluminum, hafnium, zirconium, titanium, chromium, tantalum and ruthenium, and more preferably at least one of aluminum oxide layer, hafnium oxide layer, zirconium oxide layer, titanium oxide layer, aluminum nitride layer, titanium nitride layer, chromium nitride layer or ruthenium layer.

[0036] The patterned layer in this embodiment may include a single layer, oxide layer, nitride layer, oxynitride layer or combination layer formed of one or more elements selected from silicon, tantalum, titanium, hafnium, zirconium, aluminum, chromium and carbon, and is more preferably at least one of silicon oxide layer, silicon nitride layer, titanium oxide layer, tantalum oxide layer, tantalum nitride layer, chromium nitride layer, chromium oxynitride layer, aluminum oxide layer or amorphous carbon layer.

[0037] The multilayer film in this embodiment may include alternatingly stacked first and second reflective layers; wherein the first and second reflective layers are each independently selected from one or more elements, alloys, or compounds selected from molybdenum, silicon, ruthenium, beryllium, carbon, niobium, rhodium, and palladium.

[0038] In this embodiment, an interface control layer or a diffusion blocking layer may be provided between the first reflective layer and the second reflective layer. The interface control layer or diffusion blocking layer is used to suppress interlayer diffusion, reduce interface roughness, or improve interface thermal stability, thereby ensuring the stability of the interface optical reflection properties.

[0039] The protective layer in this embodiment may include a single layer, alloy layer, compound layer or combination layer formed of one or more elements selected from ruthenium, silicon, zirconium, molybdenum, titanium and tantalum, and is more preferably a ruthenium layer, a ruthenium-based alloy layer, a silicon-containing layer or a composite structure thereof.

[0040] This invention provides a phase-shifting mask for extreme ultraviolet (EUV) lithography. By pre-constructing a phase-shifting step structure in a patterned layer and continuously forming multiple films on it, different regions form different equivalent optical paths, thereby creating a predetermined phase difference between the EUV reflected light from different regions. Compared with schemes that rely on absorbers to achieve phase-shifting modulation, this invention does not require an absorber structure, which helps reduce the three-dimensional mask effect caused by oblique incidence and structure height. Compared with schemes that directly etch multiple films to form a phase-shifting structure, this embodiment avoids patterned etching of the multiple films themselves, which helps reduce problems such as multilayer interface damage, increased roughness, interlayer diffusion, and decreased reflectivity, thus balancing phase modulation capability, reflectivity, and structural stability.

[0041] Example 2: This invention provides a method for manufacturing a phase-shifting mask for extreme ultraviolet (EUV) lithography, based on the aforementioned embodiments, and is used to manufacture the EUV lithography phase-shifting mask provided in the aforementioned embodiments. See also... Figure 2 The flowchart illustrates a method for manufacturing a phase-shifting mask for extreme ultraviolet (EUV) lithography. This method includes the following steps: Step S202, provide the substrate.

[0042] Step S204: An etching stop layer is formed on the substrate.

[0043] In this embodiment, a substrate can be provided, and an etching stop layer is formed on the substrate.

[0044] In some embodiments, an etching stop layer may be formed on the substrate using an atomic layer deposition method.

[0045] The etching stop layer in this embodiment may include an aluminum oxide layer with a thickness of 4 nm to 15 nm. The etching stop layer can be used to improve the control accuracy of the etching depth of the patterned layer, reduce the impact of the etching process on the substrate, help suppress the increase in surface roughness caused by etching, improve the interface smoothness, and provide good surface conditions for the subsequent deposition of multilayer films.

[0046] Step S206: A pattern layer is formed on the etch stop layer.

[0047] In this embodiment, a pattern layer can be formed on the etching stop layer, and the pattern layer is used to form a phase shift step structure.

[0048] Step S208: A resist layer is formed on the patterned layer; the patterned layer is patterned and etched using the resist layer as a mask to form a patterned layer with a phase-shifting step structure; the resist layer is removed; and a multilayer film is formed on the patterned layer with the phase-shifting step structure.

[0049] In this embodiment, multiple films can be continuously formed on the phase-shifting step structure so that the phase-shifting step structure and the multiple films together constitute an extreme ultraviolet reflective phase-shifting structure.

[0050] In some embodiments, the resist layer may be exposed and developed, and the pattern layer may be etched using the developed resist layer as a mask.

[0051] In this embodiment, a resist layer can be formed on the pattern layer, and the resist layer can be exposed and developed to form a resist pattern. The pattern layer is etched using the resist pattern as a mask to form a phase-shift step structure with a preset depth; the resist layer is removed and the etched structure is cleaned to obtain a pattern layer with a phase-shift step structure.

[0052] In some embodiments, the resist layer includes: an electron beam resist layer; the electron beam resist layer includes at least: a polymethyl methacrylate resist and / or a styrene polymer resist.

[0053] In some embodiments, an oxygen plasma cleaning process can be used to remove the resist layer; a magnetron sputtering process can be used to deposit a multilayer film on a patterned layer with a phase-shifted step structure.

[0054] In this embodiment, the multilayer film can continuously cover the area where the phase-shift step structure is located and the non-step area.

[0055] Step S210: A protective layer is formed on the multilayer film to obtain a phase-shifting mask.

[0056] In this embodiment, a protective layer can be formed on a multilayer film to obtain a phase-shifting mask for extreme ultraviolet lithography.

[0057] The method for manufacturing a phase-shifting mask for extreme ultraviolet lithography provided in this invention has the following advantages: 1. The method provided in this embodiment of the invention preconstructs a phase-shifting step structure in the patterned layer and continuously forms a multilayer film thereon, so that the phase-shifting function is achieved by the step structure and the multilayer film in synergy, without relying on the absorber structure, thereby helping to reduce the three-dimensional effect of the mask.

[0058] 2. The method provided in this embodiment of the invention does not require direct patterning etching of the multilayer film, which helps to reduce multilayer film interface damage, interlayer diffusion, increased roughness and degradation of reflective performance, and improves the stability of the mask structure and the consistency of reflective performance.

[0059] 3. The method provided in this embodiment of the invention, through the combination of phase-shifting step structure and multilayer film, forms a preset phase difference between extreme ultraviolet reflected light in different regions, which is beneficial to improving imaging contrast, edge slope and image fidelity.

[0060] 4. The method provided in the embodiments of the present invention has a clear process path. It can realize the construction of extreme ultraviolet phase shift structure by first patterning the pattern layer and then depositing a multilayer film, which has good process feasibility.

[0061] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the manufacturing method of the phase shift mask for extreme ultraviolet lithography described above can be referred to the corresponding process in the aforementioned embodiments of the phase shift mask for extreme ultraviolet lithography, and will not be repeated here.

[0062] Example 3: This invention provides another phase-shifting mask for extreme ultraviolet lithography, which is implemented based on the aforementioned embodiments. The focus is on describing the pattern types and imaging effects that can be achieved.

[0063] See Figure 3The diagram illustrates a comparison of existing extreme ultraviolet (EUV) mask structures, including binary absorber masks, attenuation-type phase-shift masks, and etching-type phase-shift masks. Binary absorber masks typically define the exposure pattern by forming an absorber pattern on a multilayer film. Due to the thickness of the absorber, under oblique incidence of EUV light, three-dimensional mask effects such as shadowing and image position shift can easily occur, affecting image quality. Attenuation-type phase-shift masks typically use low-refractive-index absorbing materials to introduce phase modulation while reducing the absorber height. However, this approach still essentially retains the absorber structure, making it difficult to fundamentally avoid shadowing and other three-dimensional mask effects caused by the structure height. Etching-type phase-shift masks typically form the phase-shift structure by directly etching a multilayer film. While this can introduce a phase difference, it easily leads to problems such as multilayer film interface damage, increased roughness, interlayer diffusion, and degradation of reflectivity.

[0064] like Figure 1 As shown, the phase-shifting mask for extreme ultraviolet (EUV) lithography provided in this embodiment includes a substrate, an etching stop layer formed on the substrate, a pattern layer formed on the etching stop layer, a multilayer film continuously formed on the pattern layer, and a protective layer formed on the multilayer film. The pattern layer, after patterned etching, forms a phase-shifting step structure. This phase-shifting step structure, together with the multilayer film continuously covering it, constitutes an EUV reflective phase-shifting structure to modulate the phase of EUV light.

[0065] In this embodiment, the phase-shifting step structure is not obtained by directly etching multiple layers, but is pre-formed in a patterned layer. Subsequently, by continuously forming multiple layers on the phase-shifting step structure, different equivalent optical paths are formed in the step region and the non-step region during extreme ultraviolet light reflection, thereby creating a preset phase difference between the reflected light from different regions. Compared with schemes that rely on thick absorbers to achieve pattern definition or phase-shifting modulation, this embodiment does not rely on a thick absorber structure; compared with schemes that directly etch multiple layers to form steps, this embodiment does not require patterning etching of the multiple layers themselves, thus facilitating a balance between phase modulation capability, reflection characteristics, and structural stability.

[0066] See Figure 4 The diagram illustrates different patterns that can be formed using a phase-shifting mask. This embodiment demonstrates that the phase-shifting mask can form various types of patterns. For example, it can form one-dimensional line patterns, rectangular array patterns, checkerboard patterns, and characters or other complex two-dimensional graphics. After the aforementioned different patterns are patterned and etched to form a phase-shifting step structure, multiple layers are continuously formed on top of it, all of which can constitute the corresponding extreme ultraviolet reflection phase-shifting pattern. This shows that this embodiment is not limited to a single wire grid structure but is applicable to a variety of one-dimensional and two-dimensional patterns.

[0067] See Figure 5The diagram shows the imaging effect corresponding to different pattern types. Figure 5 The imaging effects of the "E"-type pattern and the grating-type pattern are shown. To verify the optical response of the phase-shifting mask in this embodiment, a representative pattern can be selected as the analysis object to evaluate its diffraction response and imaging effect.

[0068] In some implementations, the corresponding image plane intensity distribution can be obtained using Fourier optics based on the reflection field distribution of the phase-shifting mask. Results show that, due to the combined effect of the phase-shifting step structure and the continuous multilayer film, a predetermined phase difference can be formed between the extreme ultraviolet reflected light in different regions, thereby modulating the diffraction energy distribution and further improving image plane contrast and edge steepness. For representative patterns such as wire gratings, the phase-shifting mask in this embodiment can obtain a relatively clear spatial image distribution, indicating its feasibility for extreme ultraviolet imaging.

[0069] In this embodiment, by prefabricating a phase-shifting step structure in the patterned layer and continuously forming multiple films thereon, the significant shadowing effect caused by traditional thick absorber structures is avoided, as well as the interface damage and reflection performance degradation that may be caused by directly etching the multilayer films. Furthermore, the reflective phase-shifting structure formed in this embodiment is applicable to various pattern types, and its phase modulation capability can be verified through diffraction response and imaging effect analysis, thus providing a new mask structure scheme for improving the imaging quality of extreme ultraviolet lithography.

[0070] Example 4: This invention provides another method for manufacturing a phase-shifting mask for extreme ultraviolet lithography, which is implemented based on the aforementioned embodiments. The specific manufacturing process of the phase-shifting mask for extreme ultraviolet lithography is described in detail.

[0071] The fabrication process for the phase-shifting mask used in extreme ultraviolet (EUV) lithography in this embodiment can be as follows: First, an etching stop layer and a pattern layer are formed on a substrate; then, a phase-shifting step structure with a preset depth is formed in the pattern layer through patterned etching; next, multiple layers are continuously formed on the phase-shifting step structure; finally, a protective layer is formed on the multiple layers, thereby obtaining the phase-shifting mask for EUV lithography. Through this fabrication path, the phase-shifting step structure is formed beneath the multiple layers, rather than through direct etching of the multiple layers, thus improving the accuracy of step depth control and reducing the impact on the integrity of the multiple layers.

[0072] See Figure 6 The diagram illustrates a phase-shifting mask manufacturing process and the formation of a phase-shifting step structure. It shows the structural states after forming an etching stop layer, a patterned layer, and a patterned resist layer on the substrate; after etching to the etching stop layer; and after removing the resist and cleaning to obtain the phase-shifting step structure. Figure 6As shown, the manufacturing method of this embodiment includes the following steps: First, such as Figure 6 As shown, a substrate is provided, and an etching stop layer is formed on the substrate. In this embodiment, the substrate may be a low thermal expansion material substrate, a silicon substrate, a quartz substrate, or other substrate materials suitable for extreme ultraviolet mask preparation. Preferably, an atomic layer deposition method can be used to form the etching stop layer on the substrate surface. In some embodiments, the etching stop layer may be an alumina layer, preferably with a thickness of about 5 nm. The etching stop layer can serve as a transition layer for subsequent pattern layer deposition, and also as a termination layer or a layer that significantly inhibits etching during the pattern layer etching process. This improves the accuracy of etching endpoint control, reduces the impact of the etching process on the substrate itself, helps suppress the increase in surface roughness caused by etching, improves interface smoothness, and provides good surface conditions for subsequent multilayer film deposition.

[0073] Subsequently, as Figure 6 As shown, a patterned layer is formed on the etched stop layer. In this embodiment, the patterned layer can be made of silicon oxide, silicon nitride, titanium oxide, tantalum oxide, tantalum nitride, aluminum oxide, amorphous carbon, or other materials suitable for forming phase-shift step structures. The thickness of the patterned layer can be selected according to the design requirements of the target phase-shift structure so that the subsequently formed phase-shift step structure achieves the predetermined phase modulation effect after continuous formation of multilayer films. Preferably, when the target is to obtain a phase difference close to 180°, the patterned layer thickness or step height can be determined according to the corresponding equivalent optical path difference; in other embodiments, other step heights can also be designed according to the target phase modulation requirements to form different preset phase differences.

[0074] Next, as Figure 6 As shown, a resist layer is formed on the surface of the pattern layer, and the resist layer is patterned to form a preset pattern mask. In this embodiment, to achieve higher resolution pattern definition and subsequent dry etching, an electron beam resist that is sensitive to electron beam exposure and has good etching resistance can be selected. Preferably, ZEP520A type electron beam resist can be used, and it is formed on the surface of the pattern layer by spin coating and baking. Subsequently, the resist layer is subjected to electron beam exposure and development, so that the retained part of the resist layer serves as the mask area for subsequent pattern layer etching, and the opening area corresponds to the position of the step to be etched in the pattern layer.

[0075] Based on this, such as Figure 6As shown, the patterned resist layer is used as a mask to etch the patterned layer, preferably controlling the etching endpoint at the etching stop layer to form a phase-shift step structure with a preset depth. In this embodiment, the opening region of the patterned layer is etched to the surface of the etching stop layer, which serves to terminate or significantly inhibit further etching. The bottom of the resulting step essentially corresponds to the upper surface of the etching stop layer, which helps improve the accuracy of step depth control, structural consistency, and repeatability of subsequent phase modulation design. Subsequently, as... Figure 6 As shown, after etching, residual resist can be removed using an oxygen plasma cleaning process, and the surface of the structure can be cleaned to obtain a phase-shifted step structure. At this point, a predetermined height difference is formed between the step area and the non-step area in the patterned layer, providing a structural basis for the subsequent continuous formation of multilayer films.

[0076] In some embodiments, the phase-shift step structure can be characterized after the resist is removed. Preferably, a scanning electron microscope (SEM) can be used to observe the sample surface pattern to confirm the linewidth, period, and boundary morphology of the step pattern; an atomic force microscope (AFM) can be used to measure the height difference between the step region and the non-step region to confirm the actual depth and surface roughness of the phase-shift step structure; a profilometer, ellipsometry, or other thin film thickness measurement methods can also be used to assist in measuring the thickness of the remaining film layer after etching to improve the accuracy of the assessment of step depth and etching uniformity. Through the above characterization, the impact of the etching process on the surface quality of the structure can be further evaluated, and it can be verified whether the roughness control level of the phase-shift step structure meets the requirements of subsequent multilayer film deposition. In some embodiments, the root mean square roughness of the phase-shift step structure can be controlled below 1 nm, preferably below 0.5 nm, and more preferably below 0.3 nm.

[0077] See Figure 7 The diagram shows a continuous formation of multiple films on a phase-shifting step structure followed by the formation of a protective layer. It illustrates the structural state after the formation of the multiple films and the final phase-shifting mask structure after the formation of the protective layer.

[0078] like Figure 7As shown, after forming the phase-shifting step structure, a multilayer film is continuously formed on it. In this embodiment, the multilayer film can be formed using magnetron sputtering, and is preferably an alternating stacked multilayer reflective structure suitable for the extreme ultraviolet (EUV) band. In some embodiments, the multilayer film can be a molybdenum / silicon alternating stacked structure, and its number of layers, period thickness, and interface modulation method can be selected according to the reflectivity and phase modulation requirements at the target EUV wavelength. Its double-layer period thickness can be 6.0 nm to 7.2 nm, preferably 6.5 nm to 7.0 nm. The number of periods of the multilayer film can be 30 to 80, preferably 40 to 60. Since the multilayer film continuously covers the step region and non-step region, different regions can form different EUV reflection phase responses under the combined action of the bottom structure and the multilayer film, thereby constituting an EUV reflection phase-shifting structure.

[0079] like Figure 7 As shown, after the multilayer film is formed, a protective layer can be further formed on its surface to improve the surface stability, oxidation resistance, and environmental adaptability of the phase-shift mask during subsequent storage, transmission, characterization, and application. In this embodiment, the protective layer can be formed on the surface of the multilayer film using magnetron sputtering, atomic layer deposition, or other processes suitable for thin film deposition. Preferably, the protective layer can be a ruthenium layer, a ruthenium-based alloy layer, a silicon-containing layer, or a composite structure thereof, and more preferably a ruthenium layer. The ruthenium layer not only protects the underlying multilayer film but also has good surface stability and process compatibility in the extreme ultraviolet band, which is beneficial for maintaining the reflectivity of the multilayer film.

[0080] After the formation of the multilayer film and protective layer, the sample can be further characterized in terms of film structure and surface morphology. Preferably, scanning electron microscopy can be used to observe the surface morphology and film coverage of the sample to confirm the continuous coverage of the multilayer film over the step and non-step regions; atomic force microscopy can be used to measure the surface undulations and roughness after deposition to evaluate the surface smoothness, interface quality, and roughness retention after the formation of the multilayer film and protective layer. In some embodiments, the root mean square roughness of the final structure surface can be controlled below 1 nm, preferably below 0.5 nm, and more preferably below 0.3 nm; transmission electron microscopy can also be used to characterize the layered stacking structure, interface quality, and film continuity of the multilayer film as needed; X-ray reflectance can be used to analyze the periodic structure, interface state, and film thickness uniformity of the multilayer film; and X-ray photoelectron spectroscopy can be used to characterize the film composition and surface chemical state. Through one or more of the above characterization methods, it can be confirmed that the multilayer film and protective layer have been formed on the phase-shift step structure and have the expected layered structure, coverage quality, and surface roughness control level, which is beneficial to maintaining the reflectivity and phase modulation characteristics of the multilayer film.

[0081] In this embodiment, by first forming a phase-shift step structure in the patterned layer and then continuously forming multilayer films and a protective layer, direct patterning etching of the multilayer films is avoided, which helps to reduce interface damage and degradation of reflective properties. Simultaneously, controlling the etching endpoint using an etching stop layer improves the depth consistency and processing stability of the phase-shift step structure, thus providing a solid technological foundation for the subsequent realization of the extreme ultraviolet reflective phase modulation structure.

[0082] Example 5: This invention provides another phase-shifting mask for extreme ultraviolet lithography, which is implemented based on the aforementioned embodiments. The focus is on describing the specific method of selecting the etching mode of the pattern layer according to the different depths of the target phase-shifting step structure.

[0083] In this embodiment, when the required depth of the phase-shift step structure is large, inductively coupled plasma (ICP) etching can be used to pattern the layer. ICP etching mainly relies on the chemical reaction between active particles in the plasma and the material surface, as well as the ion bombardment effect. It has the characteristics of high etching rate and good processing efficiency, and is suitable for forming relatively deep step structures.

[0084] In other embodiments, when the required depth of the phase-shift step structure is small, especially in the sub-10 nm range, ion beam etching is preferably used to pattern the patterned layer. Compared to ICP etching, ion beam etching (IBE) primarily uses an ion beam to physically remove material from the surface. Its etching rate is relatively slower, which is more conducive to achieving fine control of the step depth at the sub-10 nm scale, thereby improving the processing accuracy and consistency of the phase-shift step structure.

[0085] In this embodiment, the choice between ICP etching and IBE etching can be made based on the target step depth, pattern size, processing accuracy requirements, and etching response characteristics of the pattern layer material. Preferably, IBE is used for shallow step structures below 10 nm, while ICP is used for deeper step structures. By selecting the etching method described above, the step depth control accuracy can be improved while maintaining processing efficiency, which is more conducive to the subsequent realization of the extreme ultraviolet reflection phase modulation structure.

[0086] Except for the different etching methods, the material selection, deposition method and subsequent characterization methods of the etching stop layer, pattern layer, multilayer film and protective layer in this embodiment can be referred to the aforementioned embodiments, and will not be repeated here.

[0087] In summary, the phase-shifting mask for extreme ultraviolet (EUV) lithography and its manufacturing method provided in this embodiment of the invention include a substrate, an etch stop layer formed on the substrate, a pattern layer formed on the etch stop layer, a multilayer film continuously formed on the pattern layer having a phase-shifting step structure, and a protective layer formed on the multilayer film. The phase-shifting step structure in the pattern layer and the multilayer film covering it together constitute an EUV reflective phase-shifting structure to modulate the phase of EUV light. The manufacturing method includes: providing a substrate; forming an etch stop layer and a pattern layer on the substrate; forming a resist layer on the pattern layer; patterning the pattern layer using the resist layer as a mask to form a phase-shifting step structure; removing the resist layer; continuously forming a multilayer film on the phase-shifting step structure; and forming a protective layer on the multilayer film. By first constructing the phase-shifting step structure in the pattern layer and then continuously depositing the multilayer film and protective layer, this invention eliminates the need for direct patterning etching of the multilayer film, which helps reduce the three-dimensional effect of the mask, decreases damage at the multilayer film interface, and improves the stability and process feasibility of the mask structure.

[0088] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working process described above can be referred to the corresponding process in the foregoing embodiments, and will not be repeated here.

[0089] Furthermore, in the description of the embodiments of the present invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention based on the specific circumstances.

[0090] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0091] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A phase-shifting mask for extreme ultraviolet lithography, characterized in that, The phase-shift mask used for extreme ultraviolet lithography includes: a substrate, an etching stop layer, a patterning layer, a multilayer film, and a protective layer; The etching stop layer is formed on the substrate; The patterned layer is formed on the etch stop layer, and the patterned layer includes a phase-shift step structure with a preset depth formed by etching; The multilayer film is continuously formed on the patterned layer having the phase-shifting step structure, and the phase-shifting step structure cooperates with the multilayer film covering the phase-shifting step structure to perform phase modulation of extreme ultraviolet light in different regions; The protective layer is formed on the multilayer film.

2. The phase-shifting mask for extreme ultraviolet lithography according to claim 1, characterized in that, The substrate includes: a low thermal expansion material substrate, a silicon substrate, a glass substrate, a quartz substrate, a ceramic substrate, or a combination of substrates; The etching stop layer comprises a single layer, oxide layer, nitride layer, oxynitride layer, or combination layer formed of at least one element; wherein the element of the etching stop layer includes at least one of the following: aluminum, hafnium, zirconium, titanium, chromium, tantalum, or ruthenium; The patterned layer comprises a single layer, oxide layer, nitride layer, oxynitride layer, or combination layer formed of at least one element; wherein the element of the patterned layer includes at least one of the following: silicon, tantalum, titanium, hafnium, zirconium, aluminum, chromium, or carbon; The protective layer comprises a single layer, alloy layer, compound layer, or combination layer formed of at least one element; wherein the element of the protective layer includes at least one of the following: ruthenium, silicon, zirconium, molybdenum, titanium, or tantalum.

3. The phase-shifting mask for extreme ultraviolet lithography according to claim 2, characterized in that, The etching stop layer includes at least one of the following: an aluminum oxide layer, a hafnium oxide layer, a zirconium oxide layer, a titanium oxide layer, an aluminum nitride layer, a titanium nitride layer, a chromium nitride layer, or a ruthenium layer; The patterned layer includes at least one of the following: silicon oxide layer, silicon nitride layer, titanium oxide layer, tantalum oxide layer, tantalum nitride layer, chromium nitride layer, chromium oxynitride layer, aluminum oxide layer, or amorphous carbon layer. The protective layer includes at least one of the following: a ruthenium layer, a ruthenium-based alloy layer, a silicon-containing layer, or a composite structure.

4. The phase-shifting mask for extreme ultraviolet lithography according to any one of claims 1-3, characterized in that, The multilayer film includes: an alternately stacked first reflective layer and a second reflective layer; wherein the first reflective layer and the second reflective layer each include an element, alloy, or compound formed of at least one element; wherein the elements of the first reflective layer and the second reflective layer each include at least one of the following: molybdenum, silicon, ruthenium, beryllium, carbon, niobium, rhodium, or palladium.

5. The phase-shifting mask for extreme ultraviolet lithography according to claim 4, characterized in that, An interface control layer, a diffusion blocking layer, a hybrid layer, or a combination layer is disposed between the first reflective layer and the second reflective layer. The interface control layer is used to improve the interface bonding state, interface stability, or interface reflection characteristics. The diffusion barrier layer is used to suppress interlayer diffusion or improve thermal stability; The hybrid layer is a transition layer formed by the mutual penetration of the first reflective layer material and the second reflective layer material at the interface.

6. A method for manufacturing a phase-shifting mask for extreme ultraviolet lithography, characterized in that, The method for manufacturing the phase-shifting mask for extreme ultraviolet lithography as described in any one of claims 1-5 includes: Provide a base; An etching stop layer is formed on the substrate; A patterned layer is formed on the etch stop layer; A resist layer is formed on the patterned layer; the patterned layer is patterned and etched using the resist layer as a mask to form a patterned layer with a phase-shift step structure; the resist layer is removed; and a multilayer film is formed on the patterned layer with the phase-shift step structure. A protective layer is formed on the multilayer film to obtain a phase-shifting mask.

7. The method for manufacturing a phase-shifting mask for extreme ultraviolet lithography according to claim 6, characterized in that, The step of forming an etching stop layer on the substrate includes: An etching stop layer is formed on the substrate using atomic layer deposition.

8. The method for manufacturing a phase-shifting mask for extreme ultraviolet lithography according to claim 6, characterized in that, The resist layer includes: an electron beam resist layer; the electron beam resist layer includes at least: polymethyl methacrylate resist and / or styrene polymer resist.

9. The method for manufacturing a phase-shifting mask for extreme ultraviolet lithography according to claim 6, characterized in that, The step of patterning the patterned layer using the resist layer as a mask includes: The resist layer is exposed and developed, and the pattern layer is etched using the developed resist layer as a mask.

10. The method for manufacturing a phase-shifting mask for extreme ultraviolet lithography according to claim 6, characterized in that, The step of removing the resist layer includes: removing the resist layer using an oxygen plasma cleaning process; The step of forming a multilayer film on the patterned layer having the phase-shift step structure includes: depositing a multilayer film on the patterned layer having the phase-shift step structure using a magnetron sputtering process.

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