EUV mask and method of forming same

Abstract

The EUV lithography mask includes: a substrate; a patterned absorber layer includes a first material and a second material. In some embodiments, the first material is a second row of transition metals, and the second material is either the first row of transition metals or the second row of transition metals. The disclosed EUV lithography mask reduces the undesirable mask 3D effect. The embodiment of the application also relates to an EUV mask and a method of forming the same.

Description

Technical Field

[0001] Embodiments of the present application relate to an EUV mask and a method for forming the same. Background Art

[0002] The semiconductor industry has experienced exponential growth. Technological advances in materials and design have produced generations of integrated circuits (ICs), each with smaller and more complex circuits than the previous generation. Over the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased, while geometry size (i.e., the smallest component or line that can be created using a manufacturing process) has decreased. This shrinking process generally provides benefits by increasing production efficiency and reducing associated costs.

[0003] Lithography using extreme ultraviolet radiation (EUV) can be used to achieve increased functional density. EUV lithography uses a mask to create a pattern of reflective EUV radiation used to expose a photosensitive material such as a photoresist. Summary of the invention

[0004] Some embodiments of the present application provide an extreme ultraviolet (EUV) mask, comprising: a substrate; a reflective multilayer stack located on the substrate; a covering layer located on the multilayer stack; and a patterned absorption layer having a thickness between 20-100 nanometers on the covering layer, wherein the patterned absorption layer comprises a first material and a second material, wherein the first material has an extreme ultraviolet refractive index (n) between 0.855-0.890 and an extreme ultraviolet extinction coefficient (k) between 0.035-0.075, and wherein the second material has an extreme ultraviolet refractive index (n) between 0.920-0.970 and an extreme ultraviolet extinction coefficient (k) between 0-0.035.

[0005] Some other embodiments of the present application provide an extreme ultraviolet (EUV) mask, comprising: a substrate; a reflective multilayer stack located on the substrate; a cover layer located on the multilayer stack; and a patterned absorption layer having a thickness between 20-100 nanometers on the cover layer, the patterned absorption layer comprising a first material and a second material, the first material having an extreme ultraviolet refractive index (n) and an extreme ultraviolet extinction coefficient (k), and the second material having an extreme ultraviolet refractive index (n) and an extreme ultraviolet extinction coefficient (k), wherein the extreme ultraviolet refractive index (n) and the extreme ultraviolet extinction coefficient (k) are used for the first material and the second material. In a graph of ultraviolet refractive index (n) and extreme ultraviolet extinction coefficient (k), a line between a first material coordinate defined by the extreme ultraviolet refractive index (n) and the extreme ultraviolet extinction coefficient (k) of the first material and a second material coordinate defined by the extreme ultraviolet refractive index (n) and the extreme ultraviolet extinction coefficient (k) of the second material passes through a polygon defined by four coordinates (n, k) in the graph, the four coordinates being (0.860, 0.070), (0.945, 0.025), (0.945, 0.015) and (0.860, 0.040).

[0006] Some other embodiments of the present application provide a method for forming an extreme ultraviolet mask, comprising: forming a reflective multilayer stack on a substrate; forming a covering layer on the multilayer stack; and forming a patterned absorption layer on the covering layer, wherein the patterned absorption layer has a thickness between 20-100 nanometers, and wherein the patterned absorption layer comprises a first material and a second material, wherein the first material has an extreme ultraviolet refractive index (n) between 0.855-0.890 and an extreme ultraviolet extinction coefficient (k) between 0.035-0.075, and wherein the second material has an extreme ultraviolet refractive index (n) between 0.920-0.970 and an extreme ultraviolet extinction coefficient (k) between 0-0.035. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] When read in conjunction with the accompanying drawings, various aspects of the disclosed embodiments can be best understood from the following detailed description. It should be noted that, in accordance with standard practice in the industry, the various components are not drawn to scale. In fact, for clarity of discussion, the size of the various components may be arbitrarily increased or reduced.

[0008] Figure 1 is a cross-sectional view of an extreme ultraviolet (EUV) mask blank according to some embodiments.

[0009] Figure 2 According to some embodiments, a method for manufacturing Figure 1 Flowchart of a method for EUV mask blanks.

[0010] FIG. 3A to FIG. 3DThe EUV mask blank according to some embodiments is Figure 2 Cross-sectional views of various stages of the manufacturing process.

[0011] Figures 3E to 3G are cross-sectional views of embodiments of EUV mask blanks having different embodiments of absorber layers configured according to embodiments of the present disclosure.

[0012] Figure 4 is a cross-sectional view of an EUV mask according to some embodiments.

[0013] Figure 5 According to some embodiments, a method for manufacturing Figure 4 Flowchart of the EUV mask method.

[0014] FIG. 6A to FIG. 6G According to some embodiments, the EUV mask Figure 5 Cross-sectional views of various stages of the manufacturing process.

[0015] Figure 7 is a schematic diagram of a lithography system according to some embodiments of the present disclosure.

[0016] Figure 8 is a flow chart of a method of using an EUV mask according to an embodiment of the present disclosure.

[0017] Fig. 9 A “green segment” is depicted for identifying a combination of a first material and a second material for an absorber layer of an EUV mask blank and mask for embodiments of the present disclosure. DETAILED DESCRIPTION

[0018] The following disclosure provides many different embodiments or examples for realizing the different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the disclosed embodiments. Of course, these are merely examples and are not intended to be limiting. For example, in the following description, forming a first component above or on a second component may include an embodiment in which the first component and the second component are directly contacted, and may also include an embodiment in which an additional component may be formed between the first component and the second component so that the first component and the second component may not be in direct contact. In addition, the disclosed embodiments may repeat reference numerals and / or characters in various examples. This repetition is for the purpose of simplicity and clarity, and does not itself indicate the relationship between the various embodiments and / or configurations discussed.

[0019] Additionally, for ease of description, spatially relative terms such as "below," "beneath," "lower," "above," "upper," etc. may be used herein to describe the relationship of one element or component to another (or additional) elements or components as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein should likewise be interpreted accordingly.

[0020] In the manufacture of integrated circuits (ICs), a series of reusable photomasks (also referred to herein as photolithography masks or masks) are used to create patterns representing different layers of the IC. During the semiconductor device manufacturing process, photomasks are used to transfer the design of each layer of the IC onto a semiconductor substrate.

[0021] As IC sizes shrink, various types of such lithography techniques are adopted in, for example, photolithography processes, such as immersion lithography using a wavelength of around 193 nm from an ArF laser or extreme ultraviolet (EUV) light having a wavelength of 13.5 nm, to enable very small patterns (e.g., nanoscale patterns) to be transferred from a mask to a semiconductor wafer.

[0022] The continued desire for integrated devices with denser packaging has produced changes in lithography processes to create smaller individual feature sizes. The minimum feature size or "critical dimension" (CD) achievable by a process is approximately determined by the formula CD = k1*λ / NA, where k1 is a process-specific factor, 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.

[0023] For the fabrication of densely packed features with a given k1 value, the ability to project a usable image of a small feature onto the wafer is limited by the wavelength λ and the ability of the projection optics to capture sufficient diffraction orders from the illuminated mask. When densely packed features or isolated features are made from a photomask or reticle of a certain size and / or shape, the transition between light and dark at the edge of the projected image may not be clearly defined enough to properly form the target photoresist pattern. Therefore, features of 150 nm or less in size may require the use of a phase shift mask (PSM) or techniques to enhance the image quality at the wafer, for example, sharpening the edges of the features to improve the resist profile.

[0024] Phase shifting generally involves selectively changing the phase of a portion of the energy passing through the photomask / reticle so that the phase shifted energy is added to or subtracted from the energy that is not phase shifted at the surface of the material on the wafer to be exposed and patterned. By carefully controlling the shape, position, and phase shift angle of the mask features, the resulting photoresist pattern can have more precisely defined edges. As feature size decreases, the imbalance in transmitted intensity between the 0° and 180° phase portions and the phase shift that varies from 180° can cause significant critical dimension (CD) variations and placement errors for the photoresist pattern.

[0025] Phase shifting can be achieved in a variety of ways. For example, a process called attenuated phase shifting (AttPSM) utilizes a mask that includes a layer of non-opaque material that causes light passing through the non-opaque material to change in phase compared to light passing through the transparent portion of the mask. In addition, the non-opaque material can adjust the amount (intensity / magnitude) of light passing through the non-opaque material compared to the amount of light passing through the transparent portion of the mask.

[0026] Another technique is called alternating phase shift, in which a transparent mask material (e.g., a quartz or SiO2 substrate) is sized (e.g., etched) to have regions of different depths or thicknesses. The depth is selected so that the desired relative phase difference is produced in the light passing through the regions of different depths / thicknesses. The resulting mask is called an "alternating phase shift mask" or "alternating phase shifting mask" (AltPSM). AttPSM and AltPSM are referred to herein as "APSM" The description provided herein refers to AttPSM; however, the embodiments described herein also apply to AltPSM. The portion of AltPSM with a thicker depth is called a 0° phase portion, while the portion of AltPSM with a smaller depth is called a 180° phase portion. The depth difference allows light to propagate half of its wavelength in the transparent material, generating a 180° phase difference between the 0° and 180° portions. In some embodiments, a patterned phase shift material or absorption layer is located above portions of the transparent mask substrate that are not etched to different depths. Patterned phase shift materials are materials that affect the phase of light passing through the phase shift material, so that the phase of light passing through the phase shift material is offset relative to the phase of light that does not pass through the phase shift material, for example, only passes through the transparent mask substrate material and not through the phase shift material. The phase shift material can also reduce the amount of light that passes through the phase shift material relative to the amount of incident light that passes through the portion of the mask not covered by the phase shift material.

[0027] AttPSM is not without its disadvantages. For example, when EUV radiation is incident on AttPSM at an angle, the reflection from the mask is potentially subject to shadowing effects or imaging aberrations caused by the mask at the wafer. These types of effects are sometimes referred to as mask 3D effects (M3D). Mask 3D effects may (among other examples) cause a reduction in the contrast of the aerial image and also reduce the quality of the resulting photoresist profile.

[0028] In EUV lithography, in order to avoid overlapping of incident light and reflected light, the EUV mask is illuminated with oblique incident light at an angle of 6 degrees relative to the axis perpendicular to the mask plane. The obliquely incident EUV light is reflected by the reflective multilayer or absorbed by the absorber layer. In this case, if the absorber layer is thicker, a shadow is formed around the absorber line, which may make the absorber shape look wider. The mask shadowing effect, also known as the mask 3D (M3D) effect, may produce undesirable feature size-dependent focus and pattern placement shifts. As the technology node advances, the mask 3D effect becomes worse, and therefore, the absorber thickness must be reduced as much as possible to minimize the impact of the mask 3D effect.

[0029] A newly manufactured APSM may include defects, or defects may form in an APSM that has been in use for an extended period of time. Such defects may be the result of a material forming a portion of the APSM (e.g., a chromium-based material used in the absorption layer) or a combination of the material used to form the APSM and the conditions to which the APSM is subjected during the extended period of use. Defects in components of an APSM that include chromium-based materials may be repaired using the chromium-based materials. Repair of such defects may be an expensive and time-consuming process. In addition, it has been observed that an APSM with repaired defects may not perform as well as a defect-free APSM, for example, not as effectively as a defect-free APSM in reducing the M3D effect. An APSM with an absorption layer according to embodiments of the present disclosure addresses some of these disadvantages.

[0030] In embodiments of the present disclosure, an APSM structure and a method of producing such an APSM structure are described. The APSM structure according to the embodiments described herein includes a patterned absorption layer, the patterned absorption layer including at least two different materials, for example, a first material and a second material. In some embodiments, the patterned absorption layer has a thickness of about 20-100 nanometers. In some embodiments, the first material has an EUV refractive index (n) between 0.855-0.890 and an EUV extinction coefficient (k) between 0.035-0.075. In some embodiments, the second material has an EUV refractive index between 0.920-0.970 and an EUV extinction coefficient between 0-0.035. In some embodiments, the first material and the second material are located in separate layers, for example, two separate layers or multiple, alternating, separate layers. In other embodiments, the first material and the second material are combined to form an alloy in a single layer. The APSM structure including an absorption layer formed according to the embodiments disclosed herein is effective in reducing mask 3D effects, which may produce undesirable feature size-dependent focus and pattern placement offsets.

[0031] The following description relates to a mask manufacturing process, which includes two steps, a mask blank manufacturing process and a mask manufacturing process. During the mask blank manufacturing process, a mask blank is formed by depositing suitable layers (e.g., multiple reflective layers) on a suitable substrate. During the mask manufacturing process, the mask blank is patterned to form a mask having a design of a layer of an IC device.

[0032] Figure 1 is a cross-sectional view of an EUV mask blank 100 according to a first embodiment of the present disclosure. Figure 1 , the EUV mask blank 100 includes a substrate 102, a reflective multilayer stack 110 over the front side of the substrate 102, a capping layer 120 over the reflective multilayer stack 110, an absorber layer 130 over the capping layer 120, and a hard mask layer 140 over the absorber layer 130. The EUV mask blank 100 also includes a conductive layer 104 over the back side of the substrate 102 opposite the front side. The absorber layer 130 includes a first material and a second material, wherein the first material has an EUV refractive index (n) between 0.855-0.890 and an EUV extinction coefficient (k) between 0.035-0.075, and wherein the second material has an EUV refractive index (n) between 0.920-0.970 and an EUV extinction coefficient (k) between 0-0.035. Further details of their arrangement in the first material, the second material, and the multilayer or as an alloy are described in more detail below.

[0033] Figure 2is a flow chart of a method 200 for manufacturing an EUV mask blank (eg, EUV mask blank 100 ), according to some embodiments. FIG. 3A to FIG. 3D 2 is a cross-sectional view of an EUV mask blank 100 at various stages of a manufacturing process according to some embodiments. The method 200 is discussed in detail below with reference to the EUV mask blank 100. In some embodiments, additional operations are performed before, during, and / or after the method 200, or some of the operations described are replaced and / or eliminated. In some embodiments, some of the components described below are replaced or eliminated. One of ordinary skill in the art will appreciate that while some embodiments with operations performed in a particular order are discussed, the operations may be performed in another logical order.

[0034] refer to Figure 2 and Figure 3A According to some embodiments, method 200 includes operation 202 , in which a reflective multilayer stack 110 is formed over a substrate 102 . Figure 3A is a cross-sectional view of an initial structure of an EUV mask blank 100 after forming a reflective multilayer stack 110 over a substrate 102 , according to some embodiments.

[0035] refer to Figure 3A , the initial structure of the EUV mask blank 100 includes a substrate 102 made of glass, silicon, quartz or other low thermal expansion materials. The low thermal expansion material helps to minimize image distortion caused by mask heating during use of the EUV mask blank 100. In some embodiments, the substrate 102 includes fused silica, fused quartz, calcium fluoride, silicon carbide, black diamond, or silicon oxide doped with titanium oxide (SiO2 / TiO2). In some embodiments, the substrate 102 has a thickness ranging from about 1 mm to about 7 mm. In some instances, if the thickness of the substrate 102 is too small, the risk of the EUV mask blank 100 breaking or warping increases. On the other hand, in some instances, if the thickness of the substrate is too large, the weight of the EUV mask blank 100 is unnecessarily increased.

[0036] In some embodiments, the conductive layer 104 is disposed on the back side of the substrate 102. In some embodiments, the conductive layer 104 is in direct contact with the back side of the substrate 102. The conductive layer 104 is suitable for providing an electrostatic coupling of the EUV mask blank 100 to an electrostatic mask chuck (not shown) during the manufacture of the EUV mask blank 100. In some embodiments, the conductive layer 104 includes 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 (PECVD), or physical vapor deposition (PVD). The thickness of the conductive layer 104 is controlled so that the conductive layer 104 is optically transparent. In other embodiments, the conductive layer 104 is not disposed on the back side of the substrate 102.

[0037] The reflective multilayer stack 110 is disposed above the front side of the substrate 102 opposite to the back side. In some embodiments, the reflective multilayer stack 110 is in direct contact with the front side of the substrate 102. The reflective multilayer stack 110 provides high reflectivity to EUV light. In some embodiments, the reflective multilayer stack 110 is configured to achieve a reflectivity of about 60% to about 75% at a peak EUV illumination wavelength (e.g., EUV illumination of 13.5 nm). Specifically, when EUV light is applied to the surface of the reflective multilayer stack 110 at an incident angle of 4-7°, the desired reflectivity of the light is achieved. For example, when the incident angle is 6°, the maximum reflectivity of light near a wavelength of 13.5 nm is about 60%, about 62%, about 65%, about 68%, about 70%, about 72%, or about 75%.

[0038] In some embodiments, the reflective multilayer stack 110 includes alternating stacked layers of high refractive index material and low refractive index material. On the one hand, the material with a high refractive index has a tendency to scatter EUV light, and on the other hand, the material with a low refractive index has a tendency to transmit EUV light. Pairing these two types of materials together provides resonant reflectivity. In some embodiments, the reflective multilayer stack 110 includes alternating stacked molybdenum (Mo) layers and silicon (Si) layers. In some embodiments, the reflective multilayer stack 110 includes alternating stacked Mo layers and Si layers, wherein the Si layer is the top layer. In some embodiments, the Mo layer is in direct contact with the front side of the substrate 102. In some other embodiments, the Si layer is in direct contact with the front side of the substrate 102. Optionally, the reflective multilayer stack 110 includes alternating stacked layers of Mo and beryllium (Be).

[0039] The thickness of each layer in the reflective multilayer stack 110 depends on the EUV wavelength and the incident angle of the EUV light. The thickness of the alternating layers in the reflective multilayer stack 110 is adjusted to maximize the constructive interference of the EUV light reflected at each interface and minimize the total absorption of the EUV light. In some embodiments, the reflective multilayer stack 110 includes 20 to 60 pairs of alternating Mo layers and Si layers. Each Mo layer and Si layer pair can have a thickness ranging from about 2 nm to about 7 nm, with a total thickness ranging from about 100 nm to about 300 nm.

[0040] In some embodiments, each layer in the reflective multilayer stack 110 is deposited over the substrate 102 and underlying layers using ion beam deposition (IBD) or DC magnetron sputtering. The deposition method used helps ensure that the thickness uniformity of the reflective multilayer stack 110 across the substrate 102 is better than about 0.85. For example, to form the Mo / Si reflective multilayer stack 110, a Mo target is used as a sputtering target and an argon (Ar) gas (with a carbon content of 1.3×10 -2 Pa to 2.7×10 -2 Pa) as a sputtering gas, with an ion acceleration voltage of 300 V to 1500 V, a Mo layer is deposited at a deposition rate of 0.03 to 0.30 nm / sec, and then a Si target is used as a sputtering target and an Ar gas (with a pressure of 1.3×10 -2 Pa to 2.7×10 -2 The Si layer is deposited at a deposition rate of 0.03 to 0.30 nm / sec with an ion acceleration voltage of 300 V to 1500 V using a gas pressure of 1.5 Pa as a sputtering gas. The Mo / Si reflective multilayer stack is deposited by stacking the Si layer and the Mo layer in 20 to 60 cycles, each of the cycles including the above steps.

[0041] refer to Figure 2 and Figure 3B According to some embodiments, the method 200 proceeds to operation 204 where a capping layer 120 is deposited over the reflective multilayer stack 110 . Figure 3B After depositing a capping layer 120 over the reflective multilayer stack 110 according to some embodiments Figure 3A A cross-sectional view of the structure.

[0042] refer to Figure 3B , a capping layer 120 is disposed over the topmost surface of the reflective multilayer stack 110. The capping layer 120 helps protect the reflective multilayer stack 110 from oxidation and any chemical etchants to which the reflective multilayer stack 110 may be exposed during subsequent mask blank and mask manufacturing processes.

[0043] In some embodiments, the capping layer 120 includes a material that is resistant to oxidation and corrosion and has low chemical reactivity with common atmospheric gas species such as oxygen, nitrogen, and water vapor. In some embodiments, the capping layer 120 includes a transition metal such as, for example, ruthenium (Ru), iridium (Ir), rhodium (Rh), platinum (Pt), palladium (Pd), osmium (Os), rhenium (Re), vanadium (V), tantalum (Ta), hafnium (Hf), tungsten (W), molybdenum (Mo), zirconium (Zr), manganese (Mn), technetium (Tc), or alloys thereof.

[0044] In some embodiments, the capping layer 120 is formed using a deposition process such as, for example, IBD, CVD, PECVD, PVD, or atomic layer deposition (ALD). The deposition of the capping layer 120 is generally performed at a relatively low temperature, for example, less than 150° C., to prevent internal diffusion of the reflective multilayer stack 110. In an example where IBD is used to form a Ru layer as the capping layer 120, the deposition can be performed in an Ar atmosphere using a Ru target as a sputtering target.

[0045] refer to Figure 2 and Figure 3C According to some embodiments, the method 200 proceeds to operation 206 where an absorber layer 130 is deposited or formed over the cap layer 120 . Figure 3C According to some embodiments, after depositing the absorber layer 130 on the cap layer 120 Figure 3B A cross-sectional view of the structure.

[0046] The absorption layer 130 can be used to absorb radiation projected onto the EUV mask. The absorption layer 130 includes a combination of at least two different absorption materials. In some embodiments, the at least two different absorption materials include: a first absorption material having an extinction coefficient k in the EUV wavelength range that is higher than the extinction coefficient in the EUV wavelength range of the second absorption material constituting the absorption layer 130, and having a refractive index n in the EUV wavelength range that is lower than the refractive index n in the EUV wavelength range of the second material. In some embodiments, the absorption layer 130 includes a first absorption material and a second absorption material having the aforementioned extinction coefficient k and refractive index n characteristics for an EUV wavelength of 13.5 nm. In some embodiments, the extinction coefficient k in the EUV wavelength range of the first material is between 0.035-0.075, and the extinction coefficient k in the EUV wavelength range of the second material is between 0-0.035. In some embodiments, the refractive index n in the EUV wavelength range of the first material of the absorption layer 130 is between 0.855-0.890, and the refractive index n in the EUV wavelength range of the second material of the absorption layer is between 0.920-0.970.

[0047] In some embodiments, the absorber layer 130 includes a first material and a second material that, when combined in a manner described in more detail below, shifts the phase of EUV radiation (R') reflected from the surface of the patterned absorber layer 130 by 1.05π to 1.65π compared to the phase of EUV radiation (R) reflected from the surface of the cover layer 120. By deploying the absorber layer materials according to embodiments of the present disclosure, mask 3D effects caused by EUV phase distortion can be reduced. According to some embodiments, the reflectivity of the patterned absorber layer 130 to EUV radiation incident on the patterned absorber layer is 1-15% of the reflectivity of the cover layer 120 to EUV radiation incident on the cover layer. As used herein, reflectivity refers to the amount of electromagnetic radiation reflected from a surface or optical element. Reflectivity can be expressed as a ratio of reflected electromagnetic energy to incident electromagnetic energy. Therefore, focus shifts and pattern placement errors caused by mask 3D effects can be reduced, while the normalized image log slope (NILS) can be increased.

[0048] In some embodiments, the first material is a second row transition metal such as yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), or cadmium (Cd). This series of transition metals involves the filling of 4d orbitals. In some embodiments, the first material is a second row transition metal selected from Group IVB (niobium), Group VB (molybdenum), Group VIIB (ruthenium), or Group VIIIB (palladium).

[0049] In some embodiments, the second material is a first row transition metal such as scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), or zinc (Zn) or a second row transition metal such as yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), or cadmium (Cd) or a third row transition metal such as hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Rh), osmium (Os), iridium (Ir), platinum (Pt), gold (Au), or mercury (Hg). In some embodiments, the second material is not a first row transition metal, a second row transition metal, or a third row transition metal. For example, the second material is indium (In), tin (Sn), tellurium (Te), bismuth (Bi), or lead (Pb).

[0050] In some embodiments of the present disclosure, the first material includes one or more second-row transition metals selected from niobium (Nb), molybdenum (Mo), ruthenium (Ru) and palladium (Pd), and the second material includes one or more transition metals selected from titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), hafnium (Hf), tantalum (Ta), tungsten (W), iridium (Ir), platinum (Pt) and gold (Au).

[0051] In some embodiments of the present disclosure, the first material includes technetium (Tc), and the second material includes one or more of scandium (Sc), yttrium (Y), zirconium (Zr), palladium (Pd), silver (Ag), cadmium (Cd), indium (In), tin (Sn), tellurium (Te), rhenium (Re), mercury (Hg) or lead (Pb).

[0052] The first material and the second material of the absorbent layer 130 can be arranged in a variety of different ways. Figure 3E , the absorber layer 130 includes a layer A 131 above a layer B 133. In some embodiments, the layer A 131 includes a first material and the layer B 133 includes a second material. In other embodiments, the layer A 131 includes a second material and the layer B 133 includes a first material. In some embodiments, the layer A 131 or the layer B 133 or both include two or more of the elements that can be used as the first material (e.g., RuTa or RuPt) or a combination of two or more of the elements that can be used as the second material.

[0053] In some embodiments, the absorber layer 130 including layer A and layer B has a total thickness between 20-100 nanometers. In other embodiments, layer A and layer B have a combined thickness between 30-65 nanometers. In some embodiments, the thickness of layer B is between 1-75% of the thickness of layer A. In some embodiments, the thickness of layer A is between 10 nanometers and 90 nanometers, and the thickness of layer B is between 90 nanometers and 10 nanometers. When the absorber layer 130, layer A, and layer B have thicknesses within the aforementioned ranges, the combination of layer A and layer B may fall within the following descriptions: Fig. 9The green segment 900 of FIG. 1 is within the green segment 900 of FIG. 1 , and the absorber layer provides a desired level of phase shift and a desired level of reflectivity. When the absorber layer 130, layer A, and layer B have thicknesses outside the aforementioned range, the combination of the materials of layer A and layer B may not fall within the green segment 900, and the absorber layer may not provide a desired level of phase shift or a desired level of reflectivity. The embodiments according to the present disclosure are not limited to the aforementioned thicknesses of layer A and layer B, for example, layer A may have a thickness that falls outside the aforementioned range, and layer B may have a thickness that falls outside the aforementioned range. In some embodiments, the mass of the second material in the absorber layer is between 1% and 80% of the total mass of the absorber layer. In some embodiments, the mass of the first material in the absorber layer is greater than 20% of the total mass of the absorber layer and less than 99% of the total mass of the absorber layer.

[0054] exist Figure 3F In other embodiments shown in , the absorbent layer 130 includes a plurality of alternating layers of a first material 131 and a second material 133. Figure 3F In the embodiment shown in , eight layers of the first material 131 and eight layers of the second material 133 are shown; however, embodiments according to the present disclosure are not limited to eight layers of the first material 131 and eight layers of the second material 133. In other embodiments, more than eight layers of the first material or the second material may be provided. Figure 3F In the embodiment shown in , the uppermost layer is the first material layer; however, in other embodiments, the uppermost layer may be the second material layer. Figure 3F In the embodiment shown in , the bottom layer is a layer of the second material; however, in other embodiments, the bottom layer can be a layer of the first material. The thickness of the independent layers of the first material and the second material can vary. For example, the thickness of each layer of the first material and the second material is between 0.5nm and 1.5nm. In other embodiments, the thickness of each layer of the first material and the second material is less than 0.5nm or greater than 1.5nm. In some embodiments, the thickness of the first material layer is not equal to the thickness of the adjacent layer of the second material. In some embodiments, the absorption layer 130 including multiple layers of the first material and the second material has a total thickness between 20-100 nanometers. In other embodiments, Figure 3F The absorber layer 130 has a thickness between 30-65 nanometers. In some embodiments, the combined thickness of the multiple layers of the second material is between 1-75% of the combined thickness of the multiple layers of the first material. In some embodiments, the combined thickness of the independent layers of the first material is between 10 nanometers and 90 nanometers, and the combined thickness of the independent layers of the second material is between 90 nanometers and 10 nanometers. When the absorber layer 130, the first material 131 layer, and the second material 133 layer have thicknesses within the aforementioned ranges, the combination of the first material and the second material falls within the range described below. Fig. 9, and the absorption layer provides a desired level of phase shift and a desired level of reflectivity. When the absorption layer 130, the first material 131 layer, and the second material 133 layer have thicknesses that fall outside the aforementioned ranges, the combination of the first material and the second material does not fall within the green segment 900, and the absorption layer may not provide a desired level of phase shift or a desired level of reflectivity. The embodiments according to the present disclosure are not limited to the aforementioned combined thickness of the first material layer and the second material layer. For example, the combined thickness of the first material layer may fall outside the aforementioned range, and the combined thickness of the second material layer may fall outside the aforementioned range. Figure 3F In some embodiments of the arrangement, the total mass of the second material in the absorbent layer is greater than 1% and less than 80% of the total mass of the absorbent layer. In some embodiments, the total mass of the first material in the absorbent layer is greater than 20% and less than 99% of the total mass of the absorbent layer.

[0055] In another embodiment, the absorbent layer 130 is formed as a single layer of an alloy 135 of a first material and a second material. An alloy is a substance composed of two components of a metal or a metal and a non-metal in close combination, usually by being fused together and dissolving into each other when melted. Figure 3G An example of such an embodiment of the present disclosure is shown. Figure 3G In some embodiments of the embodiments, the absorption layer 130 including the alloy of the first material and the second material has a total thickness between 20-100 nanometers. In other embodiments, the absorption layer 130 has a combined thickness between 30-65 nanometers. The embodiments according to the present disclosure are not limited to the aforementioned thicknesses, for example, Figure 3G The absorbent layer may have a thickness outside the aforementioned range. In some embodiments, the mass of the second material in the absorbent layer is greater than 1% and less than 80% of the total mass of the absorbent layer. In some embodiments, the mass of the first material in the absorbent layer is greater than 20% and less than 99% of the total mass of the absorbent layer. Figure 3G In some embodiments, the atomic ratio of the first material to the second material of the absorber layer 130 is between 0.5:1 and 1.5:1. When the atomic ratio of the first material to the second material of the absorber layer 130 falls within the aforementioned range, the combination of the first material and the second material falls within the range described below. Fig. 9 The green segment 900 of the absorber layer 130 is within the green segment 900, and the absorber layer provides a desired level of phase shift and a desired level of reflectivity. When the atomic ratio of the first material to the second material of the absorber layer 130 falls outside the aforementioned range, the combination of the first material and the second material of the absorber layer may not fall within the green segment 900, and may not provide a desired level of phase shift and / or a desired level of reflectivity. Figure 3GThe embodiment is not limited to the atomic ratio of the first material to the second material of the absorption layer 130 being within the aforementioned range. Figure 3G The atomic ratio of the first material to the second material of the absorption layer may fall above or below the aforementioned range.

[0056] According to an embodiment of the present disclosure, exemplary combinations of the first material and the second material are listed in Tables 1-5 below. The combination of the first material and the second material that meets the criteria listed in Tables 1-5 provides a combination of the first material and the second material that falls within the following description Fig. 9 Combinations of first materials and second materials that fall outside the criteria listed in Tables 1-5 below result in combinations of first materials and second materials that fall outside the green segment 900.

[0057] Table 1. Ru first material

[0058]

[0059]

[0060] Table 2. Pd first material

[0061]

[0062] Table 3. Mo first material

[0063]

[0064] Table 4. Nb first material

[0065]

[0066]

[0067] Table 5. RuPt first material

[0068]

[0069] Fig. 9 is a graph of the extinction coefficient k and the refractive index n of a first material and a second material that may be used as a material for an absorption layer or may be used as a material for repairing a defect in an absorption layer according to some embodiments of the present disclosure. Fig. 9 The graph of includes a "green segment" 900 identified by shading. The green segment 900 falls within Fig. 9 In the diagram of FIG. 9 , polygon 902 includes four corners 904, 906, 908, and 910. The four corners correspond to Fig. 9 The specific coordinates corresponding to the refractive index n and extinction coefficient k coordinates (n, k). Fig. 9In an embodiment of the present invention, the four coordinates are (0.86, 0.07) 904, (0.945, 0.025) 906, (0.945, 0.015) 908, and (0.86, 0.04) 910. As explained in more detail below, the green segment 900 is used to identify a combination of a first material and a second material that provides an absorbing layer that meets the APSM criteria of a refractive index between 0.860-0.945, an extinction coefficient of 0.070-0.015, and a thickness of 30-65 nm. In some embodiments, the first material and the second material are selected such that the connection Fig. 9 The line of two materials in passes through at least a portion of polygon 902 (e.g., through green segment 900). Fig. 9 , the line between the first material ruthenium (Ru) and the second material iridium (Ir) passes through a portion of the green segment 900. Similarly, the line between molybdenum (Mo) and iridium (Ir), the line between palladium (Pd) and titanium (Ti), and the line between niobium (Nb) and gold (Au) pass through the green segment 900. The combination of the first material and the second material that is selected to meet the aforementioned criteria provides an absorption layer for the APSM that exhibits satisfactory phase shift and reflection properties while effectively reducing the M3D effect before and after being subjected to the repair process. In addition, the combination of the first material and the second material that meets the aforementioned criteria provides a material that can be used to repair defects in the APSM using the first material and the second material in its absorption layer. The combination of the first material and the second material that does not meet the aforementioned criteria does not provide an absorption layer that exhibits satisfactory phase shift and reflection properties while effectively reducing the M3D effect. The combination of the first material and the second material that does not meet the aforementioned criteria cannot be used to repair defects in the absorption layer of the APSM.

[0070] The absorption layer 130 is formed by a deposition technique, such as PVD, CVD, ALD, RF magnetron sputtering, DC magnetron sputtering, or IBD.

[0071] In the embodiments of the present disclosure, by deploying the absorber layer material as described above, the mask 3D effect caused by EUV phase distortion can be reduced. Therefore, the best focus offset and pattern placement error can be reduced, while the normalized image logarithmic slope (NILS) can be increased.

[0072] refer to Figure 2 and Figure 3D According to some embodiments, method 200 proceeds to operation 208 where a hard mask layer 140 is deposited over absorber layer 130 . Figure 3D After depositing a hard mask layer 140 over the absorber layer 130 according to some embodiments Figure 3C A cross-sectional view of the structure.

[0073] refer to Figure 3D, a hard mask layer 140 is disposed over the absorption layer 130. The hard mask layer 140 has different etching characteristics from the absorption layer 130 and thus serves as an etch stop layer to prevent damage to the absorption layer 130 during the photolithography process. In some embodiments, the hard mask layer 140 serves as an anti-reflective layer for reducing reflection of EUV radiation. In some embodiments, the hard mask layer 140 includes a dielectric material such as, for example, SiN, TaBO, TaO, CrO, or CrON.

[0074] In some embodiments, the hard mask layer 140 is formed using a deposition process such as, for example, CVD, PECVD, or PVD.

[0075] In some embodiments, the absorber layer surface includes a thin oxide layer, which may be formed by oxidizing the upper surface of the absorber layer, or deposited / formed on the upper surface of the absorber layer. Such a thin oxide layer may be less than 10 nanometers thick.

[0076] Additionally or alternatively, in some embodiments, a buffer layer (not shown) is formed on the capping layer 120 as an etch stop layer for patterning the absorption layer 130 and the sacrificial layer during a subsequent focused ion beam defect repair process for the absorption layer 130. The buffer layer may include silicon dioxide (SiO2), silicon oxynitride (SiON), or other suitable materials.

[0077] Figure 4 is a cross-sectional view of an EUV mask 400 formed by patterning the absorption layer 130 of the EUV mask blank 100 according to a second embodiment of the present disclosure. Figure 4 The EUV mask 400 includes a substrate 102, a reflective multilayer stack 110 over a front side of the substrate 102, a capping layer 120 over the reflective multilayer stack 110, and a patterned absorption layer 130P over the capping layer 120. The EUV mask 400 also includes a conductive layer 104 over a back side of the substrate 102 opposite to the front side.

[0078] The patterned absorption layer 130P includes a pattern of openings 152 corresponding to a circuit pattern to be formed on a semiconductor wafer. The pattern of the openings 152 is located in a pattern region 400A of the EUV mask 400, exposing the surface of the cover layer 120. The pattern region 400A is surrounded by a peripheral region 400B of the EUV mask 400. The peripheral region 400B corresponds to a non-patterned region of the EUV mask 400 that is not used in an exposure process during IC manufacturing. In some embodiments, the pattern region 400A of the EUV mask 400 is located in a central region of the substrate 102, and the peripheral region 400B is located at an edge portion of the substrate 102. The pattern region 400A is separated from the peripheral region 400B by a groove 154. The groove 154 extends through the patterned absorption layer 130P, the cover layer 120, and the reflective multilayer stack 110, exposing the front side of the substrate 102.

[0079] Figure 5 is a flow chart of a method 500 for manufacturing an EUV mask (eg, EUV mask 400 ), according to some embodiments. FIG. 6A to FIG. 6G 4 is a cross-sectional view of an EUV mask 400 at various stages of a manufacturing process according to some embodiments. The method 500 is discussed in detail below with reference to the EUV mask 400. In some embodiments, additional operations are performed before, during, and / or after the method 500, or some of the operations described are replaced and / or eliminated. In some embodiments, some of the components described below are replaced or eliminated. One of ordinary skill in the art will appreciate that although some embodiments are discussed with operations performed in a particular order, the operations may be performed in another logical order.

[0080] refer to Figure 5 and Fig. 6A According to some embodiments, method 500 includes operation 502 , in which a photoresist layer 610 is deposited over hard mask layer 140 . Fig. 6A is a cross-sectional view of the structure after depositing a photoresist layer 610 over the hard mask layer 140 , according to some embodiments.

[0081] refer to Fig. 6A , a photoresist layer 610 is disposed above the topmost surface of the EUV mask blank 100 (i.e., the hard mask layer 140). The photoresist layer 610 includes a photosensitive material operable to be patterned by radiation. In some embodiments, the photoresist layer 610 includes a positive photoresist material and a negative photoresist material or a mixed photoresist material. In some embodiments, the photoresist layer 610 is applied to the surface of the hard mask layer 140, for example, by spin coating.

[0082] refer to Figure 5 and Figure 6BAccording to some embodiments, the method 500 proceeds to operation 504 , where the photoresist layer 610 is photolithographically patterned to form a patterned photoresist layer 610P. Figure 6B According to some embodiments, after photolithography patterning the photoresist layer 610 to form the patterned photoresist layer 610P Fig. 6A A cross-sectional view of the structure.

[0083] refer to Figure 6B , the photoresist layer 610 is patterned by first subjecting the photoresist layer 610 to a pattern of radiation. Next, depending on whether a positive resist or a negative resist is used in the photoresist layer 610, the exposed or unexposed portions of the photoresist layer 610 are removed with a resist developer, thereby forming a patterned photoresist layer 610P having a pattern of openings 612 formed therein. The openings 612 expose portions of the hard mask layer 140. The openings 612 are located in the pattern area 400A, and a pattern corresponding to the openings 152 exists at locations in the EUV mask 400 ( Figure 4 ).

[0084] refer to Figure 5 and Figure 6C According to some embodiments, the method 500 proceeds to operation 506 , where the hard mask layer 140 is etched using the patterned photoresist layer 610P as an etching mask to form a patterned hard mask layer 140P. Figure 6C According to some embodiments, after etching the hard mask layer 140 to form the patterned hard mask layer 140P Figure 6B A cross-sectional view of the structure.

[0085] refer to Figure 6C , the portion of the hard mask layer 140 exposed by the opening 612 is etched to form an opening 142 extending through the hard mask layer 140. The opening 142 exposes a portion of the underlying absorption layer 130. In some embodiments, the hard mask layer 140 is etched using anisotropic etching. In some embodiments, the anisotropic etching is a dry etch, such as, for example, reactive ion etching (RIE), wet etching, or a combination thereof. The etching removes the material providing the hard mask layer 140 that is selective to the material providing the absorption layer 130. The remaining portion of the hard mask layer 140 constitutes the patterned hard mask layer 140P. If not completely consumed during the etching of the hard mask layer 140, the patterned photoresist layer 610P is removed from the surface of the patterned hard mask layer 140P, for example, using wet stripping or plasma ashing, after etching the hard mask layer 140.

[0086] refer to Figure 5 and Fig.6D According to some embodiments, the method 500 proceeds to operation 508 , where the absorption layer 130 is etched using the patterned hard mask layer 140P as an etch mask to form a patterned absorption layer 130P. Fig.6D According to some embodiments, after etching the absorption layer 130 to form the patterned absorption layer 130P Figure 6C A cross-sectional view of the structure.

[0087] refer to Fig.6D , the portion of the absorption layer 130 exposed by the opening 142 is etched to form an opening 132 extending through the absorption layer 130. The opening 132 exposes a portion of the underlying capping layer 120. The opening 132 in the patterned absorption layer 130P defines the pattern of the opening 152 in the EUV mask 400. In some embodiments, the absorption layer 130 is etched using an anisotropic etching process. In some embodiments, the anisotropic etching is a dry etch, such as, for example, RIE, wet etching, or a combination thereof, which removes the material providing the absorption layer 130 selective to the material providing the underlying capping layer 120. For example, in some embodiments, the absorption layer 130 is dry etched with a gas containing chlorine (such as Cl2 or BCl3) or with a gas containing fluorine (such as NF3). Argon (Ar) can be used as a carrier gas. In some embodiments, oxygen (O2) can also be included as a carrier gas. The etching rate and etching selectivity depend on the etchant gas, the etchant flow rate, the power, the pressure, and the substrate temperature. After etching, the remaining portion of the absorption layer 130 constitutes the patterned absorption layer 130P.

[0088] refer to Figure 5 and Fig. 6E According to some embodiments, the method 500 proceeds to operation 510 , where a patterned photoresist layer 620P including a pattern of openings 622 is formed over the patterned hard mask layer 140P and the capping layer 120 . Fig. 6E According to some embodiments, after forming a patterned photoresist layer 620P including an opening 622 over the patterned hard mask layer 140P and the capping layer 120 Fig.6D A cross-sectional view of the structure.

[0089] refer to Fig. 6E , the opening 622 exposes a portion of the patterned hard mask layer 140P located at the periphery of the patterned absorption layer 130P. The opening 622 corresponds to the groove 154 ( Figure 4 ). To form the patterned photoresist layer 620P, a photoresist layer (not shown) is applied over the patterned hard mask layer 140P and the capping layer 120. The photoresist layer fills the opening 142 in the patterned hard mask layer 140P and the opening 132 in the patterned absorption layer 130P. In some embodiments, the photoresist layer includes a positive photoresist material, a negative photoresist material, or a mixed photoresist material. In some embodiments, the photoresist layer includes the same Fig. 6AIn some embodiments, the photoresist layer comprises a material different from the photoresist layer 610. In some embodiments, the photoresist layer is formed, for example, by spin coating. Subsequently, the photoresist layer is patterned by: exposing the photoresist layer to a pattern of radiation; and removing the exposed or unexposed portions of the photoresist layer using a resist developer depending on whether a positive or negative resist is used. The remaining portion of the photoresist layer constitutes the patterned photoresist layer 620P.

[0090] refer to Figure 5 and Fig. 6F According to some embodiments, the method 500 proceeds to operation 512 , where the patterned hard mask layer 140P, the patterned absorption layer 130P, the capping layer 120 , and the reflective multilayer stack 110 are etched using the patterned photoresist layer 620P as an etching mask to form a trench 154 in the peripheral region 400B of the substrate 102 . Fig. 6F After etching the patterned hard mask layer 140P, the patterned absorption layer 130P, the capping layer 120, and the reflective multilayer stack 110 to form the trench 154 in the peripheral region 400B of the substrate 102 according to some embodiments. Fig. 6E A cross-sectional view of the structure.

[0091] refer to Fig. 6F The trench 154 extends through the patterned hard mask layer 140P, the patterned absorber layer 130P, the capping layer 120, and the reflective multilayer stack 110 to expose the surface of the substrate 102. The trench 154 surrounds the pattern region 400A of the EUV mask 400, separating the pattern region 400A from the peripheral region 400B.

[0092] In some embodiments, a single anisotropic etching process is used to etch the patterned hard mask layer 140P, the patterned absorption layer 130P, the capping layer 120, and the reflective multilayer stack 110. The anisotropic etching may be a dry etch, such as, for example, RIE, a wet etch, or a combination thereof, which removes the material of the corresponding patterned hard mask layer 140P, the patterned absorption layer 130P, the capping layer 120, and the reflective multilayer stack 110 that is selective to the material providing the substrate 102. In some embodiments, a plurality of different anisotropic etching processes are used to etch the patterned hard mask layer 140P, the patterned absorption layer 130P, the capping layer 120, and the reflective multilayer stack 110. Each anisotropic etching may be a dry etch, such as, for example, RIE, a wet etch, or a combination thereof.

[0093] Subsequently, the patterned photoresist layer 620P is removed from the patterned area 400A and the peripheral area 400B of the substrate 102, for example, by wet stripping or plasma ashing. Removing the patterned photoresist layer 620P from the openings 142 in the patterned hard mask layer 140P and the openings 132 in the patterned absorption layer 130P re-exposes the surface of the capping layer 120 in the patterned area 400A.

[0094] refer to Figure 5 and Figure 6G According to some embodiments, the method 500 proceeds to operation 514 where the patterned hard mask layer 140P is removed. Figure 6G According to some embodiments, after removing the patterned hard mask layer 140P Fig. 6F A cross-sectional view of the structure.

[0095] refer to Figure 6G , removing the patterned hard mask layer 140P exposes the surface of the patterned absorption layer 130P. In some embodiments, the patterned hard mask layer 140P is removed by an etching process, which can be anisotropic etching or isotropic etching. In some embodiments, the etching can be a dry etch (such as RIE) or a wet chemical etch that selectively removes the patterned hard mask layer 140P without removing the remaining patterned absorption layer 130P, the capping layer 120, the reflective multilayer stack 110, and the substrate 102.

[0096] After removing the patterned hard mask layer 140P, the EUV mask 400 may be cleaned to remove any contaminants therefrom. In some embodiments, the EUV mask 400 is cleaned by immersing the EUV mask 400 in an ammonium hydroxide (NH4OH) solution. In some embodiments, the EUV mask 400 is cleaned by immersing the EUV mask 400 in a dilute hydrofluoric acid (HF) solution.

[0097] The EUV mask 400 is then illuminated with UV light, for example, having a wavelength of 193 nm, for inspection of any defects in the patterned area 400A. Foreign matter can be detected from the diffusely reflected light. If defects are detected, the EUV mask 400 is further cleaned using a suitable cleaning process.

[0098] The patterned absorption layer 130P includes a first material and a second material that provide a combination of independent refractive index, EUV extinction coefficient, and thickness characteristics, which allows the formation of an absorption layer that reduces the mask 3D effect. Therefore, the pattern on the EUV mask 400 can be accurately projected onto a semiconductor wafer.

[0099] Figure 7is a schematic diagram of a lithography system 700 according to some embodiments of the present disclosure. The lithography system 700 may also be referred to herein as a "scanner" that is operable to perform a lithography exposure process with a corresponding radiation source and exposure mode.

[0100] In some embodiments, the lithography system 700 includes a high brightness light source 702, an illuminator 704, a mask stage 706, a photomask (ie, EUV mask 400), a projection optical module 710, and a substrate stage 712. In some embodiments, the lithography system may include Figure 7 In further embodiments, one or more of the high brightness light source 702, the illuminator 704, the mask stage 706, the projection optics module 710, and the substrate stage 712 may be omitted from the lithography system 700, or may be integrated into a combined component.

[0101] High brightness light source 702 can be configured to emit radiation having a wavelength in the range of approximately 1 nanometer (nm) to 250 nm. In some embodiments, high brightness light source 702 generates EUV light having a wavelength centered around approximately 13.5 nanometers; therefore, high brightness light source 702 may also be referred to as an “EUV light source.”

[0102] In an embodiment where the lithography system 700 is an EUV lithography system, the illuminator 704 includes various reflective optical components, such as a single mirror or a mirror system including a plurality of mirrors. The illuminator 704 can direct light from the high brightness light source 702 onto the mask stage 706, and more specifically, onto the EUV mask 400 fixed on the mask stage 706.

[0103] The mask stage 706 may be configured to hold the EUV mask 400. In some examples, the mask stage 706 may include an electrostatic chuck (e-chuck) to hold the EUV mask 400. This is because gas molecules absorb EUV light, and the lithography system 700 for EUV lithography patterning is maintained in a vacuum environment to minimize EUV intensity loss.

[0104] In some examples, a pellicle 714 can be positioned above the EUV mask 400, for example, between the EUV mask 400 and the substrate stage 712. The pellicle 714 can protect the EUV mask 400 from particles and can keep the particles out of focus so that the particles do not create an image (which could cause defects on the wafer during the lithography process).

[0105] The projection optical module 710 can be configured to image the pattern of the EUV mask 400 onto a semiconductor wafer 716 fixed on a substrate stage 712. In some embodiments, the projection optical module 710 includes a reflective optical device for an EUV lithography system. Light directed from the EUV mask 400 (carrying an image of the pattern defined on the EUV mask 400) can be collected by the projection optical module 710. The illuminator 704 and the projection optical module 710 can be collectively referred to as the "optical module" of the lithography system 700.

[0106] In some embodiments, semiconductor wafer 716 may be a bulk semiconductor wafer. For example, semiconductor wafer 716 may include a silicon wafer. Semiconductor wafer 716 may include silicon or another element semiconductor material, such as germanium. In some embodiments, semiconductor wafer 716 may include a compound semiconductor. Compound semiconductors may include gallium arsenide, silicon carbide, indium arsenide, indium phosphide, another suitable material, or a combination thereof. In some embodiments, semiconductor wafer 716 includes a silicon on insulator (SOI) substrate. The SOI substrate may be manufactured using an oxygen implantation isolation (SIMOX) process, a wafer bonding process, another applicable process, or a combination thereof. In some embodiments, semiconductor wafer 716 includes an undoped substrate. However, in other embodiments, semiconductor wafer 716 includes a doped substrate, such as a p-type substrate or an n-type substrate.

[0107] In some embodiments, the semiconductor wafer 716 includes various doped regions (not shown) depending on the design requirements of the semiconductor device structure. The doped regions may include, for example, a p-type well and / or an n-type well. In some embodiments, the doped regions are doped with p-type dopants. For example, the doped regions may be doped with boron or boron fluoride. In other examples, the doped regions are doped with n-type dopants. For example, the doped regions may be doped with phosphorus or arsenic. In some examples, some of the doped regions are p-doped and other doped regions are n-doped.

[0108] In some embodiments, an interconnect structure may be formed over the semiconductor wafer 716. The interconnect structure may include multiple interlayer dielectric layers, including dielectric layers. The interconnect structure may also include multiple conductive features formed in the interlayer dielectric layers. The conductive features may include conductive wires, conductive vias, and / or conductive contacts.

[0109] In some embodiments, various device elements are formed in the semiconductor wafer 716. Examples of various device elements may include transistors (e.g., metal oxide semiconductor field effect transistors (MOSFETs), complementary metal oxide semiconductor (CMOS) transistors, bipolar junction transistors (BJTs), high voltage transistors, high frequency transistors, p-channel and / or n-channel field effect transistors (PFETs and / or NFETs)), diodes, or other suitable elements. Various processes may be used to form various device elements, including deposition, etching, implantation, photolithography, annealing, and / or other suitable processes.

[0110] The device elements may be interconnected by interconnect structures over the semiconductor wafer 716 to form an integrated circuit device. The integrated circuit device may include a logic device, a memory device (e.g., a static random access memory (SRAM) device), a radio frequency (RF) device, an input / output (I / O) device, a system on a chip (SoC) device, an image sensor device, other applicable devices, or a combination thereof.

[0111] In some embodiments, semiconductor wafer 716 may be coated with a photoresist that is sensitive to EUV light. Various components including those described above may be integrated together and may be operable to perform a photolithography exposure process.

[0112] Figure 8 A method 800 for using an EUV mask according to an embodiment of the present disclosure is shown. The method 800 includes a step 802 of exposing the EUV mask to incident radiation (e.g., EUV radiation). Examples of EUV masks that can be used in step 802 include the EUV mask 400 described above. In step 804, a portion of the incident radiation is absorbed by the patterned absorption layer 130P of the EUV mask 400. In step 806, a portion of the incident radiation is reflected from the reflective multilayer stack 110. In step 808, the portion of the incident radiation reflected by the reflective multilayer stack 110 is directed to a photoresist disposed on a semiconductor wafer. In step 810, after the patterned photoresist has been exposed to the radiation reflected from the EUV mask 400, the portion of the photoresist exposed to or not exposed to the radiation reflected from the EUV mask 400 is removed. In step 812, the pattern in the patterned photoresist is transferred to the semiconductor wafer.

[0113] One aspect of the specification relates to an extreme ultraviolet mask. The EUV mask includes a substrate, a reflective multilayer stack on the substrate, a cover layer on the reflective multilayer stack, and a patterned absorption layer on the cover layer. The patterned absorption layer includes a first material and a second material, wherein the first material has an EUV refractive index (n) between 0.855-0.890 and an EUV extinction coefficient (k) between 0.035-0.075, and wherein the second material has an EUV refractive index (n) between 0.920-0.970 and an EUV extinction coefficient (k) between 0-0.035.

[0114] Another aspect of the present specification relates to a method for patterning a photoresist using an EUV mask. The method includes exposing the EUV mask to incident radiation. The EUV mask includes a reflective multilayer stack on a substrate, a cover layer on the reflective multilayer stack, and a patterned absorption layer on the cover layer. The patterned absorption layer has a thickness between 20-100 nanometers and includes a first material and a second material. The first material has an EUV refractive index (n) between 0.855-0.890 in the EUV wavelength range and an EUV extinction coefficient (k) between 0.035-0.075 in the EUV wavelength range. The second material has an EUV refractive index (n) between 0.920-0.970 in the EUV wavelength range and an EUV extinction coefficient (k) between 0-0.035 in the EUV wavelength range. The method also includes: reflecting EUV radiation incident on the patterned absorption layer from the patterned absorption layer; and reflecting EUV radiation incident on the cover layer from the cover layer. The method includes shifting the phase of EUV radiation reflected from the patterned absorber layer by 1.05π to 1.65π compared to the phase of EUV radiation reflected from the capping layer.

[0115] Another aspect of the specification relates to an extreme ultraviolet (EUV) mask. The EUV mask includes a substrate, a reflective multilayer stack on the substrate, a cover layer on the reflective multilayer stack, and a patterned absorption layer on the cover layer. The patterned absorption layer includes a first material and a second material, wherein the first material has an EUV refractive index (n) between 0.855-0.890 and an EUV extinction coefficient (k) between 0.035-0.075, and wherein the second material has an EUV refractive index (n) between 0.920-0.970 and an EUV extinction coefficient (k) between 0-0.035.

[0116] Some embodiments of the present application provide an extreme ultraviolet (EUV) mask, comprising: a substrate; a reflective multilayer stack located on the substrate; a covering layer located on the multilayer stack; and a patterned absorption layer having a thickness between 20-100 nanometers on the covering layer, wherein the patterned absorption layer comprises a first material and a second material, wherein the first material has an extreme ultraviolet refractive index (n) between 0.855-0.890 and an extreme ultraviolet extinction coefficient (k) between 0.035-0.075, and wherein the second material has an extreme ultraviolet refractive index (n) between 0.920-0.970 and an extreme ultraviolet extinction coefficient (k) between 0-0.035.

[0117] In some embodiments, the substrate is formed of quartz. In some embodiments, the reflective multilayer stack comprises a MoSi compound. In some embodiments, the weight percent of the second material of the patterned absorption layer is between 1 and 80% of the combined weight of the first material and the second material. In some embodiments, the first material is a second row transition metal. In some embodiments, the first material comprises palladium (Pd). In some embodiments, the second material is a first row transition metal, a second row transition metal, or a third row transition metal. In some embodiments, the first row transition metal, the second row transition metal, or the third row transition metal of the second material comprises one or more transition metals selected from titanium (Ti), vanadium (V), hafnium (Hf), tungsten (W), molybdenum (Mo), niobium (Nb), or zirconium (Zr). In some embodiments, the patterned absorption layer has a thickness between 30 and 65 nanometers. In some embodiments, the patterned absorption layer comprises a first layer of the first material and a second layer of the second material. In some embodiments, the patterned absorption layer comprises more than one first layer or more than one second layer. In some embodiments, the patterned absorption layer comprises a single layer comprising an alloy of the first material and the second material.

[0118] Some other embodiments of the present application provide an extreme ultraviolet (EUV) mask, comprising: a substrate; a reflective multilayer stack located on the substrate; a cover layer located on the multilayer stack; and a patterned absorption layer having a thickness between 20-100 nanometers on the cover layer, the patterned absorption layer comprising a first material and a second material, the first material having an extreme ultraviolet refractive index (n) and an extreme ultraviolet extinction coefficient (k), and the second material having an extreme ultraviolet refractive index (n) and an extreme ultraviolet extinction coefficient (k), wherein the extreme ultraviolet refractive index (n) and the extreme ultraviolet extinction coefficient (k) are used for the first material and the second material. In a graph of ultraviolet refractive index (n) and extreme ultraviolet extinction coefficient (k), a line between a first material coordinate defined by the extreme ultraviolet refractive index (n) and the extreme ultraviolet extinction coefficient (k) of the first material and a second material coordinate defined by the extreme ultraviolet refractive index (n) and the extreme ultraviolet extinction coefficient (k) of the second material passes through a polygon defined by four coordinates (n, k) in the graph, the four coordinates being (0.860, 0.070), (0.945, 0.025), (0.945, 0.015) and (0.860, 0.040).

[0119] In some embodiments, the first material comprises one or more second row transition metals selected from niobium (Nb), molybdenum (Mo), ruthenium (Ru), palladium (Pd), and technetium (Tc). In some embodiments, the second material comprises one or more transition metals selected from titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), hafnium (Hf), tantalum (Ta), tungsten (W), iridium (Ir), platinum (Pt), and gold (Au). In some embodiments, the absorber layer has a thickness in a range between 30-65 nanometers.

[0120] Some other embodiments of the present application provide a method for forming an extreme ultraviolet mask, comprising: forming a reflective multilayer stack on a substrate; forming a covering layer on the multilayer stack; and forming a patterned absorption layer on the covering layer, wherein the patterned absorption layer has a thickness between 20-100 nanometers, and wherein the patterned absorption layer comprises a first material and a second material, wherein the first material has an extreme ultraviolet refractive index (n) between 0.855-0.890 and an extreme ultraviolet extinction coefficient (k) between 0.035-0.075, and wherein the second material has an extreme ultraviolet refractive index (n) between 0.920-0.970 and an extreme ultraviolet extinction coefficient (k) between 0-0.035.

[0121] In some embodiments, the first material comprises palladium. In some embodiments, the second material comprises a first row transition metal, a second row transition metal, or a third row transition metal selected from titanium (Ti), vanadium (V), hafnium (Hf), tungsten (W), molybdenum (Mo), niobium (Nb), or zirconium (Zr). In some embodiments, forming a patterned absorption layer on the capping layer comprises forming a first layer of the first material and forming a second layer of the second material.

[0122] The features of several embodiments are summarized above so that those skilled in the art can better understand the various aspects of the embodiments of the present disclosure. Those skilled in the art should understand that they can easily use the embodiments of the present disclosure as a basis to design or modify other processes and structures for performing the same purpose and / or achieving the same advantages as the embodiments introduced herein. Those skilled in the art should also appreciate that such equivalent constructions do not deviate from the spirit and scope of the embodiments of the present disclosure, and that they can make various changes, substitutions and modifications herein without departing from the spirit and scope of the embodiments of the present disclosure.

Claims

1. An extreme ultraviolet (EUV) mask, comprising: substrate; a reflective multilayer stack disposed on the substrate; a cover layer disposed on the multi-layer stack; as well as A patterned absorption layer having a thickness between 20-100 nanometers on the covering layer, wherein the patterned absorption layer comprises a first material and a second material, wherein the first material has an extreme ultraviolet refractive index (n) between 0.855-0.890 and an extreme ultraviolet extinction coefficient (k) between 0.035-0.075, and wherein the second material has an extreme ultraviolet refractive index (n) between 0.920-0.970 and an extreme ultraviolet extinction coefficient (k) between 0-0.

035.

2. The EUV mask according to claim 1, wherein: The substrate is formed of quartz.

3. The EUV mask according to claim 1, wherein: The reflective multilayer stack includes a MoSi compound.

4. The EUV mask according to claim 1, wherein: The weight percent of the second material of the patterned absorber layer is between 1 and 80 percent of the combined weight of the first material and the second material.

5. The EUV mask according to claim 1, wherein: The first material is a second row transition metal.

6. The EUV mask according to claim 5, wherein: The first material includes palladium (Pd).

7. The EUV mask according to claim 5, wherein: The second material is a first row transition metal, a second row transition metal, or a third row transition metal.

8. The EUV mask according to claim 7, wherein: The first row transition metal, the second row transition metal or the third row transition metal of the second material includes one or more transition metals selected from titanium (Ti), vanadium (V), hafnium (Hf), tungsten (W), molybdenum (Mo), niobium (Nb) or zirconium (Zr).

9. An extreme ultraviolet (EUV) mask comprising: substrate; a reflective multilayer stack disposed on the substrate; a cover layer disposed on the multi-layer stack; as well as A patterned absorption layer having a thickness between 20-100 nanometers on the covering layer, the patterned absorption layer comprising a first material and a second material, the first material having an extreme ultraviolet refractive index (n) and an extreme ultraviolet extinction coefficient (k), and the second material having an extreme ultraviolet refractive index (n) and an extreme ultraviolet extinction coefficient (k), wherein, in a graph of extreme ultraviolet refractive index (n) and extreme ultraviolet extinction coefficient (k) for the first material and the second material, a line between a first material coordinate defined by the extreme ultraviolet refractive index (n) and the extreme ultraviolet extinction coefficient (k) of the first material and a second material coordinate defined by the extreme ultraviolet refractive index (n) and the extreme ultraviolet extinction coefficient (k) of the second material passes through a polygon defined by four coordinates (n, k) in the graph, the four coordinates being (0.860, 0.070), (0.945, 0.025), (0.945, 0.015), and (0.860.0.040).

10. A method of forming an extreme ultraviolet mask, comprising: forming a reflective multilayer stack on a substrate; forming a cover layer on the multi-layer stack; as well as A patterned absorption layer is formed on the covering layer, wherein the patterned absorption layer has a thickness between 20-100 nanometers, and wherein the patterned absorption layer includes a first material and a second material, wherein the first material has an extreme ultraviolet refractive index (n) between 0.855-0.890 and an extreme ultraviolet extinction coefficient (k) between 0.035-0.075, and wherein the second material has an extreme ultraviolet refractive index (n) between 0.920-0.970 and an extreme ultraviolet extinction coefficient (k) between 0-0.035.

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