EUV lithography mask blank, EUV mask and method

Abstract

The invention relates to an EUV photoetching mask blank, an EUV mask and a method. The EUV lithography mask includes a substrate, a patterned absorber layer including a rhodium alloy. In some embodiments, the rhodium alloy includes a Group 5, Group 6, Group 9, Group 10, or Group 11 transition metal having a particular EUV refractive index and a particular EUV extinction coefficient. The disclosed EUV lithography mask reduces the undesirable mask 3D effects.

Description

[0001] Priority claims and cross references

[0002] This disclosure claims the benefit of U.S. Provisional Patent Application No. 63 / 615,167, filed on December 27, 2023, and U.S. Patent Application No. 18 / 614,445, filed on March 22, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to an EUV lithography mask blank, an EUV mask and a method. Background Art

[0004] The semiconductor industry has experienced exponential growth. Technological advances in materials and design have produced successive generations of integrated circuits (ICs), each with smaller and more complex circuits than the previous one. Over the course of IC evolution, functional density (i.e., the number of interconnected devices per unit chip area) has generally increased, while geometry size (i.e., the smallest component or line that can be made using a manufacturing process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and reducing associated costs.

[0005] Lithography using extreme ultraviolet radiation (EUV) helps increase functional density. EUV lithography uses a mask to create a pattern of reflected EUV radiation for exposing a photosensitive material such as a photoresist. Summary of the invention

[0006] Some embodiments of the present invention relate to an extreme ultraviolet (EUV) mask, comprising: a substrate; a reflective multilayer stack on the substrate; a capping layer on the multilayer stack; a buffer layer on the capping layer; and a patterned absorption layer on the buffer layer having a thickness between 20-50 nanometers, wherein the patterned absorption layer comprises an alloy of a first material and a second material, wherein the first material is rhodium (Rh) having an EUV refractive index (n) and an EUV extinction coefficient (k), and wherein the second material is a transition metal of Group 5, Group 6, Group 9, Group 10 or Group 11, whose EUV refractive index (n) is greater than the EUV refractive index (n) of rhodium, and whose EUV extinction coefficient (k) is greater than the EUV extinction coefficient (k) of rhodium.

[0007] Some other embodiments of the present invention relate to an extreme ultraviolet (EUV) mask, comprising: a substrate; a reflective multilayer stack on the substrate; a capping layer on the multilayer stack; and a patterned absorption layer on the capping layer, the patterned absorption layer comprising an alloy of a first material and a second material, the first material having an EUV refractive index (n) and an EUV extinction coefficient (k), and the second material having an EUV refractive index (n) and an EUV extinction coefficient (k), wherein the EUV refractive index (n) of the first material and the second material is greater than the EUV refractive index (n) of the second material. ) and EUV extinction coefficient (k), a line between a first material coordinate defined by the EUV refractive index (n) and the EUV extinction coefficient (k) of the first material and a second material coordinate defined by the EUV refractive index (n) and the EUV extinction coefficient (k) of the second material passes through a polygon defined in the plot of four coordinates (n, k), and the four coordinates are (0.880, 0.030), (0.880, 0.050), (0.900, 0.050) and (0.900, 0.030), respectively.

[0008] According to other embodiments of the present invention, there is provided a method for forming an EUV mask, comprising the following steps: providing an EUV mask blank, the EUV mask blank comprising: a reflective multilayer stack on a substrate, a capping layer on the multilayer stack, a buffer layer on the capping layer, and an absorption layer on the buffer layer, wherein the thickness of the absorption layer is between 20-50 nanometers, and wherein the absorption layer comprises an alloy of a first material and a second material, wherein the first material is rhodium (Rh) having an EUV refractive index (n) and an EUV extinction coefficient (k), and wherein the second material is a transition metal of Group 5, Group 6, Group 9, Group 10 or Group 11, whose EUV refractive index (n) is greater than the EUV refractive index (n) of rhodium, and whose EUV extinction coefficient (k) is greater than the EUV extinction coefficient (k) of rhodium; and patterning the absorption layer to form a patterned absorption layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The various aspects of the present disclosure may be better understood by reading the following detailed description in conjunction with the accompanying drawings. It should be noted that, in accordance with industry standard practice, various features are not drawn to scale. In fact, the size of various features may be arbitrarily increased or decreased for ease of discussion.

[0010] Figure 1 is a cross-sectional view of an extreme ultraviolet (EUV) mask blank according to some embodiments.

[0011] Figure 2 According to some embodiments, a method for manufacturing Figure 1 A flow chart of a method for making an EUV mask blank is shown.

[0012] FIG. 3A to FIG. 3D According to some embodiments, an EUV mask blank is Figure 2 Cross-sectional views of various stages of the manufacturing process are shown.

[0013] Figures 3E to 3G are cross-sectional views of various embodiments of EUV mask blanks having different embodiments of absorber layers configured according to the present disclosure.

[0014] Figure 4 is a cross-sectional view of an EUV mask according to some embodiments.

[0015] Figure 5 According to some embodiments, a method for manufacturing Figure 4 A flow chart of the EUV mask method is shown.

[0016] FIG. 6A to FIG. 6G According to some embodiments, an EUV mask is Figure 5 Cross-sectional views of various stages of the manufacturing process are shown.

[0017] Figure 7 is a schematic diagram of a lithography system according to some embodiments of the present disclosure.

[0018] Figure 8 is a flow chart of a method of using an EUV mask according to an embodiment of the present disclosure.

[0019] Fig. 9 A "red area" is depicted to identify a combination of a first material and a second material used to form an alloy used in the absorber layer of the EUV mask blanks and masks of the present disclosure. DETAILED DESCRIPTION

[0020] The following disclosure provides many different embodiments or examples for realizing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. Of course, these are merely examples and are not restrictive. For example, in the following description, the formation of a first feature on a second feature or a first feature on a second feature may include an embodiment in which the first feature and the second feature are directly contacted, and may also include an embodiment in which additional features may be formed between the first feature and the second feature so that the first feature and the second feature may not be in direct contact. In addition, the present disclosure may repeat reference numbers and / or letters in various examples. This repetition is for simplicity and clarity, and does not itself determine the relationship between the various embodiments and / or configurations discussed.

[0021] In addition, 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 feature shown in the figures to another element or feature. Spatially relative terms also include different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may also be in other orientations (rotated 90 degrees or other orientations), and the spatially relative descriptors used herein may be interpreted accordingly.

[0022] During 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 manufacture of semiconductor devices, photomasks are used to transfer the designs of the various layers of the IC onto a semiconductor substrate.

[0023] As IC sizes shrink, various types of such lithography techniques, such as immersion lithography using ArF lasers with a wavelength of approximately 193 nm or extreme ultraviolet (EUV) light with a wavelength of 13.5 nm, are applied, for example, in lithography processes capable of transferring very small patterns (e.g., nanoscale patterns) from a mask onto a semiconductor wafer.

[0024] The desire to achieve more densely packed integrated devices has led to 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 visible to the substrate or wafer.

[0025] When densely packed features with a given k1 value are fabricated, the ability to project a usable image of small features onto the wafer is limited by the wavelength λ and the ability of the projection optics to capture sufficient diffraction order from the illuminated mask. When densely packed features or isolated features are fabricated with a photomask or reticle of a certain size and / or shape, the light-dark transitions at the edges of the projected image may not be defined sharply 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 improve the image quality at the wafer, for example, to sharpen the edges of the features to improve the resist profile.

[0026] Phase shifting generally refers to 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 non-phase-shifted energy at the surface of the material to be exposed and patterned on the wafer. By carefully controlling the shape, position, and phase shift angle of the mask features, the resulting photoresist pattern will have more precisely defined edges. As feature size decreases, the imbalance of transmitted intensity between the 0° to 180° phase portion and the phase shift different from 180° can cause significant changes in the critical dimension (CD) of the photoresist pattern and produce placement errors.

[0027] Phase shifting can be achieved in a variety of ways. For example, a process known as attenuated phase shifting (AttPSM) utilizes a mask that includes a layer of non-opaque material such that light passing through the non-opaque material has a phase shift compared to light passing through the transparent portion of the mask. Additionally, the non-opaque material can adjust the amount (intensity / amplitude) of light transmitted through the non-opaque material compared to the amount of light transmitted through the transparent portion of the mask.

[0028] Another technique is called alternating phase shift, in which the size of a transparent mask material (e.g., a quartz or SiO2 substrate) is designed (e.g., etched) to have regions of different depths or thicknesses. The depth is selected so that light passing through regions of different depths / thicknesses produces the desired relative phase difference. The mask thus produced is called an "alternating phase shift mask or alternating phase shifting mask" (AltPSM). AttPSM and AltPSM are referred to as "APSM" in this article. The description of the absorber material and absorber layer configuration provided herein refers to AltPSM; however, the embodiments described herein also apply to AttPSM. The portion with a larger depth in AltPSM is called a 0° phase portion, while the portion with a smaller depth in AltPSM is called a 180° phase portion. The depth difference allows light to propagate half of its wavelength in the transparent material, thereby producing a 180° phase difference between the 0° portion and the 180° portion. In some implementations, the patterned phase shift material or absorber layer is located above the portion of the transparent mask substrate that is not etched to different depths. A patterned phase-shift material is a material that affects the phase of light passing through the phase-shift material so that the phase of light passing through the phase-shift material is shifted relative to the phase of light that has not passed through the phase-shift material (e.g., has only passed through a transparent mask substrate material and not through the phase-shift material). The phase-shift material can also reduce the amount of light transmitted through the phase-shift material relative to the amount of incident light that passes through portions of the mask not covered by the phase-shift material.

[0029] AltPSM and AttPSM are not without their drawbacks. For example, when EUV radiation is incident on AltPSM or AttPSM at a certain angle, the reflection from the mask may produce shadowing effects or mask-induced imaging aberrations at the wafer. These types of effects are sometimes referred to as mask 3D effects (M3D). In addition, mask 3D effects may also reduce the contrast of the aerial image and the quality of the resulting photoresist profile.

[0030] In EUV lithography, in order to avoid the overlap of incident light and reflected light, the EUV mask is illuminated in an oblique manner using incident light tilted 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 or partially absorbed by the absorber layer. In this case, if the absorber layer is thick enough, a shadow will be formed around the absorption line, making the shape of the absorber appear wider. The mask shadow effect, also known as the mask 3D (M3D) effect, will cause unwanted feature size-dependent focus and pattern placement shifts. As the technology node develops, the mask 3D effect will become more and more serious, so the thickness of the absorber must be reduced as much as possible to minimize the impact of the mask 3D effect.

[0031] In an embodiment of the present disclosure, an APSM structure and a method for producing such an APSM structure are described. The APSM structure according to the embodiments described herein includes a patterned absorption layer, wherein the absorption layer includes one or more absorption material sublayers, for example, one absorption material layer constitutes the absorption layer, two absorption material sublayers constitute the absorption layer, three absorption material sublayers constitute the absorption layer, or more than three absorption material sublayers constitute the absorption layer. In other embodiments, the absorption layer is configured as a plurality of nanolayers of absorption material of nano-lamination, wherein each nanolayer includes a different alloy absorption material. In some embodiments, the thickness of a single nanolayer is less than 2 nm, and the thickness of the nano-lamination is between 15-70 nm. In other embodiments, the thickness of the nano-lamination is 20-50 nm. The absorption material of the absorption material layer or absorption material sublayer can be a polycrystalline microstructure (for example, a grain size of 1-5 nanometers) or an amorphous microstructure. In some embodiments, the absorbing material of each layer or sublayer is an alloy of a first material and a second material, wherein the first material is rhodium (Rh), and the EUV refractive index (n) of the second material (i.e., the refractive index of EUV radiation centered at a wavelength of 13.5 nanometers) is greater than the EUV refractive index of rhodium, and the EUV extinction coefficient (k) of the second material (i.e., the extinction coefficient of EUV radiation centered at a wavelength of 13.5 nanometers) is greater than the EUV extinction coefficient of rhodium. In some embodiments, the absorbing material contains oxygen (O), nitrogen (N), or boron (B). In some embodiments, the thickness of the absorbing layer is about 15-70 nanometers. In other embodiments, the thickness of the patterned absorbing layer is about 20-50 nanometers. In some embodiments, the first material has an EUV refractive index (n) of about 0.875 and an EUV extinction coefficient (k) of about 0.031. As used herein, the term "about" means within 5% of the listed value. In some embodiments, the EUV refractive index of the second material is greater than the EUV refractive index of the first material (e.g., rhodium), and its EUV extinction coefficient is greater than the EUV extinction coefficient of the first material. The APSM structure including the absorber layer formed according to the embodiments disclosed herein exhibits a smaller thickness, which makes the mask less susceptible to undesirable mask 3D effects, which can lead to unwanted feature size dependent focus and pattern placement shifts. The APSM structure including the absorber layer formed according to the above embodiments exhibits a higher spatial image contrast using the Normalized Image Log Slope (NILS) evaluation. The use of the APSM structure formed according to the present disclosure can achieve a desirable low mask enhancement factor (MEEF).

[0032] The manufacture of photolithography mask is described below, which involves mask blank manufacturing process and mask manufacturing process. In the mask blank manufacturing process, a mask blank is formed by depositing a suitable reflective layer (e.g., multiple reflective layers), a capping layer, a buffer layer, (multiple) absorbing layers and (one or more) hard mask layers on a suitable substrate (e.g., a low thermal expansion material (LTEM)). The conductive layer can be arranged on the back side of the low thermal expansion material substrate. The mask is formed by patterning the mask blank during the mask manufacturing process. The formed mask will have a positive or reverse design of the semiconductor device layer to be manufactured using the formed mask.

[0033] Figure 1 is a cross-sectional view of an EUV mask blank 100 according to a first embodiment of the present disclosure.

[0034] Reference Figure 1 , the EUV mask blank 100 includes a substrate 102, a reflective multilayer stack 110 on a front surface of the substrate 102, a capping layer 120 on the reflective multilayer stack 110, a buffer layer 125 on the capping layer 120, an absorber layer 130 on the buffer layer 125, and a hard mask layer 140 on the absorber layer 130. The EUV mask blank 100 also includes a conductive layer 104 on a rear surface opposite to the front surface of the substrate 102. The absorber layer 130 includes an alloy of a first material and a second material, the first material having an EUV refractive index (n) and an EUV extinction coefficient (k), and the second material having an EUV refractive index (n) and an EUV extinction coefficient (k). In a plot of the EUV refractive index (n) and the EUV extinction coefficient (k) of a first material and a second material, a line between a first material coordinate defined by the EUV refractive index (n) and the EUV extinction coefficient (k) of the first material and a second material coordinate defined by the EUV refractive index (n) and the EUV extinction coefficient (k) of the second material passes through a plot of the four coordinates (n, k) (e.g., Fig. 9 ), the four coordinates are (0.880, 0.030), (0.880, 0.050), (0.900, 0.050) and (0.900, 0.030). Further details about the alloy of the first material and the second material and the deployment of the alloy in one or more layers will be described in more detail below.

[0035] Figure 2 is a method for manufacturing an EUV mask blank (e.g., Figure 1 Flowchart of a method 200 of forming an EUV mask blank 100 in FIG. FIG. 3A to FIG. 3D2 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 will be 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 features described below are replaced or eliminated. It will be appreciated by those of ordinary skill in the art that although operations are performed in a particular order when discussing some embodiments, the operations may be performed in another logical order.

[0036] Reference Figure 2 and Figure 3A , method 200 includes operation 202 , in which a reflective multilayer stack 110 is formed on a substrate 102 , according to some embodiments. Figure 3A is a cross-sectional view of the initial structure of the EUV mask blank 100 after forming a reflective multilayer stack 110 over a substrate 102 according to some embodiments.

[0037] Reference 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 the use of the EUV mask formed by 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 thickness of the substrate 102 ranges from about 1 mm to about 7 mm. If the thickness of the substrate 102 is too small, then in some cases, the risk of cracking or warping of the EUV mask blank 100 increases. On the other hand, if the thickness of the substrate is too large, then in some cases, the weight of the EUV mask blank 100 is unnecessarily increased. Excessive weight can cause mask warping and distortion from the mask blank 100.

[0038] In some embodiments, the conductive layer 104 is disposed on the rear surface of the substrate 102. In some embodiments, the conductive layer 104 is in direct contact with the rear surface of the substrate 102. The conductive layer 104 is suitable for electrostatically coupling the EUV mask blank 100 to an electrostatic mask chuck (not shown) during the manufacturing process 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 rear surface of the substrate 102.

[0039] The reflective multilayer stack 110 is disposed on a front surface opposite to the rear surface of the substrate 102. In some embodiments, the reflective multilayer stack 110 is in direct contact with the front surface of the substrate 102. The reflective multilayer stack 110 has a high reflectivity to EUV light incident on the reflective multilayer stack 110. 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 at 13.5nm). Specifically, when EUV light is irradiated to the surface of the reflective multilayer stack 110 at an incident angle of 4-7°, the desired light reflectivity can be achieved. For example, when the incident angle is 6°, the maximum reflectivity of light near a wavelength of 13.5nm is about 60%, about 62%, about 65%, about 68%, about 70%, about 72%, or about 75%.

[0040] In some embodiments, the reflective multilayer stack 110 includes alternating layers of high refractive index materials and low refractive index materials. On the one hand, materials with a high refractive index tend to scatter EUV light, and on the other hand, materials with a low refractive index tend to transmit EUV light. Pairing these two materials together can produce resonant reflection. In some embodiments, the reflective multilayer stack 110 includes alternating layers of molybdenum (Mo) and silicon (Si). In some embodiments, the reflective multilayer stack 110 includes alternating layers of Mo and Si, wherein the Si layer is the top layer. In some embodiments, the Mo layer is in direct contact with the front surface of the substrate 102. In some other embodiments, the Si layer is in direct contact with the front surface of the substrate 102. Alternatively, the reflective multilayer stack 110 includes alternating layers of Mo and beryllium (Be).

[0041] 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 fine-tuned to maximize the constructive interference of the EUV light reflected at each interface and minimize the overall 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. The thickness of each pair of Mo layers and Si layers can vary from about 2 nm to about 7 nm, with a total thickness ranging from about 100 nm to about 300 nm.

[0042] In some embodiments, each layer in the reflective multilayer stack 110 is deposited on the substrate 102 and the underlying layer 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 argon (Ar) (gas pressure of 1.3×10 -2 Pa to 2.7×10 -2 Pa) as the sputtering gas, the Mo layer was deposited at an ion acceleration voltage of 300 V to 1500 V and a deposition rate of 0.03 to 0.30 nm / sec, and then a Si target was used as the sputtering target, and Ar gas (gas pressure of 1.3×10 -2 Pa to 2.7×10 -2 Pa) as a sputtering gas, the Si layer is deposited at an ion acceleration voltage of 300 V to 1500 V and a deposition rate of 0.03 to 0.30 nm / sec. The Mo / Si reflective multilayer stack is deposited by stacking the Si layer and the Mo layer for 20 to 60 cycles (each cycle includes the above steps).

[0043] Reference Figure 2 and Figure 3B , the method 200 proceeds to operation 204 , where a capping layer 120 is deposited over the reflective multilayer stack 110 , according to some embodiments. Figure 3B According to some embodiments, after depositing a capping layer 120 on the reflective multilayer stack 110 Figure 3A Cross-sectional view of the structure shown.

[0044] Reference Figure 3B, capping layer 120 is disposed above the uppermost surface of reflective multilayer stack 110. Capping layer 120 helps protect reflective multilayer stack 110 from oxidation and any chemical etchants to which reflective multilayer stack 110 may be exposed during subsequent mask blank and mask manufacturing processes. In some embodiments, capping layer 120 has a thickness of 2 nanometers to 5 nanometers. Embodiments according to the present disclosure are not limited to capping layers having a thickness of 2 nanometers to 5 nanometers. For example, in other embodiments, the thickness of capping layer 20 may be less than 2 nanometers or greater than 5 nanometers.

[0045] In some embodiments, the capping layer 120 comprises an oxidation-resistant, corrosion-resistant material and has low chemical reactivity with common atmospheric gas species such as oxygen, nitrogen, and water vapor. In some embodiments, the capping layer 120 comprises 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. In some embodiments, the capping layer 130 comprises a combination of one or more of oxygen (O), niobium (Nb), nitrogen (N) and one or more of the above transition metals.

[0046] 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 typically performed at a relatively low temperature, for example, below 150° C., to prevent inter-diffusion of the reflective multilayer stack 110. In the case of using IBD to form a Ru layer as the capping layer 120, a Ru target may be used as a sputtering target and the deposition may be performed in an Ar atmosphere.

[0047] Reference Figure 2 and Figure 3C , the method 200 proceeds to operation 206 , in which the buffer layer 125 is deposited or formed on the capping layer 120 , and then the absorber layer 130 is deposited or formed on the buffer layer 125 , according to some embodiments. Figure 3C According to some embodiments, a buffer layer 125 is deposited on the capping layer 120, and then an absorber layer 130 is deposited on the buffer layer 125. Figure 3B Cross-sectional view of the structure shown.

[0048] In some embodiments, a buffer layer 125 is formed on the capping layer 120 as an etch stop layer for patterning the absorption layer 130. The buffer layer 125 can also be used as a sacrificial layer in the subsequent focused ion beam defect repair process of the absorption layer 130. In some embodiments, the buffer layer is formed of a tantalum (Ta), silicon (Si) or molybdenum (Mo) material with or without other elements such as boron, oxygen, nitrogen or carbon. The buffer layer can be formed of TaBO, TaBN, TaN, Ta2O5, TaO2, TaO, Ta2O, MoSi, MoSiN, MoSiO, SiN, SiON, SiO2, SiCON, SiC, SiCN or other suitable materials. In some embodiments, the thickness of the buffer layer 125 is between 2 nanometers and 20 nanometers. The embodiments according to the present disclosure are not limited to the thickness of the buffer layer 125 being between 2nm and 20nm. In other embodiments, the thickness of the buffer layer 125 is less than 2nm or greater than 20nm.

[0049] The absorption layer 130 can be used to absorb radiation projected onto an EUV mask formed from an EUV mask blank. The absorption layer 130 includes an absorption material, the absorption material including an alloy of a first material and a second material, the first material having an EUV refractive index (n) and an EUV extinction coefficient (k), and the second material having an EUV refractive index (n) and an EUV extinction coefficient (k). In some embodiments, the relationship between the first material and the second material is as follows. In a plot of the EUV refractive index (n) and the EUV extinction coefficient (k) of the first material and the second material (e.g., Fig. 9 ), a line connecting a first material coordinate defined by the EUV refractive index (n) and the EUV extinction coefficient (k) of the first material and a second material coordinate defined by the EUV refractive index (n) and the EUV extinction coefficient (k) of the second material passes through a red area defined in a graph plotted by four coordinates (n, k), which are (0.880, 0.030), (0.880, 0.050), (0.900, 0.050), and (0.900, 0.030), respectively. As will be described in more detail below Fig. 9 An example of a polygon 900 is included to represent this red area. In some embodiments, the second material is one or more of tantalum (Ta), chromium (Cr), cobalt (Co), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), silver (Ag), gold (Au), aluminum (Al), or tellurium (Te). In some embodiments, the alloy includes one or more of oxygen (O), nitrogen (N), or boron (B). In some embodiments, the absorber layer 130 includes two or more of the foregoing alloys.

[0050] In some embodiments, the absorber material of the absorber layer 130 includes an alloy of a first material and a second material, wherein the first material is a Group 9 transition metal, such as rhodium (Rh), and the rhodium has an EUV refractive index (n) and an EUV extinction coefficient (k). The second material is a Group 5, Group 6, Group 9, Group 10, or Group 11 transition metal, whose EUV refractive index (n) is greater than the EUV refractive index (n) of rhodium, and whose EUV extinction coefficient (k) is greater than the EUV extinction coefficient (k) of rhodium. In embodiments where the first material is rhodium, the alloy of the absorber material contains 10 to 75 atomic % of rhodium. In some embodiments where the first material is rhodium, the second material is one or more of tantalum (Ta), chromium (Cr), cobalt (Co), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), silver (Ag), gold (Au), aluminum (Al), or tellurium (Te). In some embodiments, the rhodium-containing alloy includes one or more of oxygen (O), nitrogen (N), or boron (B). In some embodiments, absorber layer 130 includes two or more of the foregoing alloys.

[0051] In some embodiments, an EUV mask including an absorber layer 130 including an absorber material according to an embodiment described herein causes the phase of EUV radiation incident on the patterned absorber layer 130 to shift by 1.17π to 1.20π (i.e., phase shift) compared to the phase of EUV radiation reflected from the surface of the capping layer 120. Embodiments according to the present disclosure are not limited to absorbers capable of shifting the phase of EUV radiation within the above range. In other embodiments, the absorber material is capable of shifting the phase of EUV radiation by less than 1.17π or greater than 1.20π. When the absorber material is capable of shifting the phase of EUV radiation by 1.17π to 1.20π, the aerial image will be sharp with minimal blur. In addition, the level of mask 3D effect, near field effect, and reflection phase shift will be more ideal compared to the case where the phase shift is less than 1.17π or greater than 1.20π. According to some embodiments, the reflectance of EUV radiation incident on portions of the patterned absorber layer 130 of the EUV mask is 1-15% of the reflectance of EUV radiation incident on portions of the EUV mask not covered by the patterned absorber layer 130. As used herein, reflectance refers to the amount of electromagnetic radiation reflected from a surface or optical element. Reflectance can be expressed as the ratio of reflected electromagnetic energy to incident electromagnetic energy. Therefore, focus shift and pattern placement error caused by the mask 3D effect can be reduced, while the normalized image logarithmic slope (NILS) can be increased.

[0052] As described above, in some embodiments, the first material in the alloy is rhodium (Rh). Rhodium has an EUV refractive index (n) and an EUV extinction coefficient (k). According to the present disclosure, the second material in the alloy of the absorbing material has an EUV refractive index (n) and an EUV extinction coefficient (k). According to the present disclosure, in a plot of the EUV refractive index (n) and the EUV extinction coefficient (k) of the first material (e.g., rhodium) and the second material, the line between the first material coordinate defined by the EUV refractive index (n) and the EUV extinction coefficient (k) of the first material and the second material coordinate defined by the EUV refractive index (n) and the EUV extinction coefficient (k) of the second material passes through a polygon defined in the plot of the four coordinates (n, k), which are (0.880, 0.030), (0.880, 0.050), (0.900, 0.050), and (0.900, 0.030), respectively.

[0053] In some embodiments, the second material is a transition metal of Group 5, Group 6, Group 9, Group 10, or Group 11, whose EUV refractive index (n) is greater than that of rhodium, and whose EUV extinction coefficient (k) is greater than that of rhodium. Examples of such transition metals include tantalum (Ta), chromium (Cr), cobalt (Co), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), silver (Ag), and gold (Au). In some embodiments, the second material is a transition metal of Period 4, Period 5, or Period 6. In some embodiments, the second material is aluminum (Al) or tellurium (Te). In some embodiments, the alloy of the first material and the second material includes one or more of oxygen (O), nitrogen (N), or boron (B). In some embodiments, the absorber layer 130 includes two or more of the foregoing alloys.

[0054] The absorbent layer 130 can be arranged in a variety of different ways. Figure 3E, the absorber layer 130 can be disposed as layer A 131 on layer B 133, where the composition of layer A is different from that of layer B. In some embodiments, layer A 131 includes an alloy of the first material and the second material, and layer B 133 includes a different alloy of the first material and the second material. For example, in some embodiments, layer A 131 includes a rhodium-containing alloy including oxygen, oxygen and nitrogen, or oxygen and boron and a second material. For example, layer A 131 may include an alloy selected from RhPdO, RhAgO, RhPtO, RhAuO, RhCoO, RhNiO, RhIrO, RhTeO, RhCrO, RhTaO, RhAlO, RhPdON, RhAgON, RhPtON, RhAuON, RhCoON, RhNiON, RhIrON, RhTeON, RhCrON, RhTaON, RhAlON, RhPdOB, RhAgOB, RhPtOB, RhAuOB, RhCoOB, RhNiOB, RhIrOB, RhTeOB, RhCrOB, RhTaOB, and RhAlOB. In some embodiments, layer A 131 has a thickness of 10-40 nm, a rhodium content of 20-75 atomic %, and an oxygen / nitrogen / boron content of 2-20 atomic %. The embodiments according to the present disclosure are not limited to the thickness of layer A being 10-40 nm. In some embodiments, the thickness of layer A may be less than 10 nm or greater than 40 nm. If the thickness of layer A131 of the absorption layer 130 is too small, the absorption layer 130 may not absorb a sufficient amount of EUV light to produce the desired phase shift, and thus may not be able to produce the desired image contrast between the portions of the mask covered by the absorption layer 130 and the portions of the mask not covered by the absorption layer 130. On the other hand, if the thickness of layer A131 of the absorption layer 130 is too large, the accuracy of the pattern to be formed in the absorption layer 130 is often low. The embodiments according to the present disclosure are not limited to the rhodium content of layer A being 20-75 atomic %. In some embodiments, the rhodium content of layer A is less than 20 atomic % or greater than 75 atomic %. If the rhodium content of layer A is too low or too high, the absorber layer 130 may not absorb a sufficient amount of EUV light incident on the absorber layer 130 to produce the desired phase shift, and thus may not produce the desired image contrast between the portions of the mask covered by the absorber layer 130 and the portions of the mask not covered by the absorber layer 130, or the accuracy of the pattern to be formed in the absorber layer 130 may be lower than the desired accuracy. Embodiments according to the present disclosure are not limited to the oxygen / nitrogen / boron content of layer A being 2-20 atomic %. For example, in some embodiments, the oxygen / nitrogen / boron content of layer A may be less than 2 atomic % or greater than 20 atomic %.If the oxygen / nitrogen / boron content of layer A is too low or too high, the absorption layer 130 may not absorb a sufficient amount of EUV light to produce the required phase shift, and thus may not produce the required image contrast between the portions of the mask covered by the absorption layer 130 and the portions of the mask not covered by the absorption layer 130, or the accuracy of the pattern to be formed in the absorption layer 130 may be lower than the required accuracy.

[0055] exist Figure 3EIn some embodiments shown, layer B 133 includes a rhodium alloy that does not contain oxygen but may contain nitrogen and / or boron. In addition, layer B 133 also includes a second material as described above. For example, layer B 133 may include an alloy selected from RhPd, RhAg, RhPt, RhAu, RhCo, RhNi, RhIr, RhTe, RhCr, RhTa, RhAl, RhPdN, RhAgN, RhPtN, RhAuN, RhCoN, RhNiN, RhIrN, RhTeN, RhCrN, RhTaN, RhAlN, RhPdB, RhAgB, RhPtB, RhAuB, RhCoB, RhNiB, RhIrB, RhTeB, RhCrB, RhTaB, and RhAlB. In some embodiments, layer B 133 has a thickness of 5-30 nanometers, a rhodium content of 20-75 atomic %, and a nitrogen / boron content of 2-20 atomic %. Embodiments according to the present disclosure are not limited to a thickness of layer B of 5-30 nm. In some embodiments, the thickness of layer B may be less than 5 nm or greater than 30 nm. If the thickness of layer B 133 of the absorber layer 130 is too small, the absorber layer 130 may not absorb a sufficient amount of EUV light, thereby failing to produce a desired contrast between the portions of the mask covered by the absorber layer 130 and the portions of the mask not covered by the absorber layer 130. On the other hand, if the thickness of layer B 133 of the absorber layer 130 is too large, the accuracy of the pattern to be formed in the absorber layer 130 may be lower than the desired accuracy. Embodiments according to the present disclosure are not limited to a rhodium content of layer B of 20-75 atomic %. In some embodiments, the rhodium content of layer B is less than 20 atomic % or greater than 75 atomic %. If the rhodium content of layer B is too low or too high, the absorber layer 130 may not absorb a sufficient amount of EUV light to produce a desired contrast between the portions of the mask covered by the absorber layer 130 and the portions of the mask not covered by the absorber layer 130, or the accuracy of the pattern to be formed in the absorber layer 130 may be lower than the desired accuracy. Embodiments according to the present disclosure are not limited to the nitrogen / boron content of layer B being 2-20 atomic%. For example, in some embodiments, the nitrogen / boron content of layer B may be less than 2 atomic% or greater than 20 atomic%. If the nitrogen / boron content of layer B is too low or too high, the absorber layer 130 may not absorb a sufficient amount of EUV light to produce a desired contrast between the portions of the mask covered by the absorber layer 130 and the portions of the mask not covered by the absorber layer 130, or the accuracy of the pattern to be formed in the absorber layer 130 may be lower than the desired accuracy.

[0056] according to Figure 3E In the embodiment shown, layer B 133 may be located above or below layer A 131. Figure 3EIn some embodiments, the buffer layer 125 is selected from TaBN, TaN, MoSi, MoSiN, SiN, SiC, SiCN, and has a thickness of 2 to 20 nanometers. Figure 3E In the same embodiment of , the capping layer 120 is selected from Ru, RuO, RuNb, RuNbO, RuZr, RuZrN, RuRh, RuON, RuNbN, RuRhN, RuVO, RuV, RuVN, and has a thickness of 2 to 5 nanometers. Figure 3E In other embodiments shown, the buffer layer 125 is selected from CrN and Cr2N, and has a thickness of 2-20 nanometers. Figure 3E In the same embodiment shown, the capping layer 120 is selected from Ru, RuO, RuNb, RuNbO, RuZr, RuZrN, RuRh, RuON, RuNbN, RuRhN, RuVO, RuV, RuVN, and has a thickness of 2 to 5 nanometers.

[0057] In some embodiments, the total thickness of the absorption layer 130 including layer A and layer B is between 10-75 nanometers. In other embodiments, the combined thickness of layer A and layer B is between 20-50 nanometers. In some embodiments, the thickness of layer B is between 12%-50% of the thickness of layer A. When the thickness of layer A and layer B are within the aforementioned ranges, the combination of layer A and layer B can provide a refractive index and an extinction coefficient falling within the ranges described below. Fig. 9 The absorber layer 130 is shown within the red region 902. When the refractive index and extinction coefficient of the absorber layer fall within the red region 902, the absorber layer 130 can provide a desired level of phase shift and a desired level of reflectivity. When the thickness of the absorber layer 130, layer A, and layer B are outside the above ranges, the refractive index and extinction coefficient of the absorber layer 130 including the combination of the layer A and layer B materials may not fall within the red region 902, and the absorber layer may not provide a desired level of phase shift or a desired level of reflectivity.

[0058] for Figure 3E The above description of the capping layer 120 and the buffer layer 125 is also applicable to the embodiment shown in FIG. Figure 3E The capping layer 120 and buffer layer used in the illustrated embodiment.

[0059] exist Figure 3F In another embodiment shown in FIG. 1 , the absorption layer 130 includes a plurality of alternating first alloy 131 layers of the first material and the second material and a second alloy 133 layers of the first material and the second material having different compositions from the first alloy 130 . Figure 3FIn the illustrated embodiment, eight layers of the first alloy 131 and eight layers of the second alloy 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 or less than eight layers of the first material or the second material may be provided. Figure 3F In the illustrated embodiment, the uppermost layer is a layer of the first alloy 131; however, in other embodiments, the uppermost layer may be a layer of the second alloy 133. Figure 3F In the illustrated embodiment, the bottom layer is a layer of the second alloy 133; however, in other embodiments, the bottom layer may be a layer of the first alloy 131. The thickness of each layer of the first alloy 131 and the second alloy 133 may be different. For example, the thickness of each layer of the first alloy 131 and the second alloy 133 may be between 0.5 nm and 1.5 nm. In other embodiments, the thickness of each layer of the first alloy and the second alloy is less than 0.5 nm or greater than 1.5 nm. In some embodiments, the thickness of the first alloy layer is not equal to the thickness of the adjacent second alloy layer, and vice versa. In some embodiments, the total thickness of the absorption layer 130 including multiple layers of the first alloy and the second alloy is between 15-75 nanometers. In other embodiments, the combined thickness of the stack of multiple layers of the first alloy 131 and the second alloy 133 is between 20-50 nanometers. In some embodiments, the combined thickness of the multiple layers of the second alloy is between 1%-75% of the combined thickness of the multiple layers of the first alloy. When the thicknesses of the absorption layer 130 and the first alloy 131 layer and the second alloy 133 layer are within the aforementioned ranges, the refractive index and extinction coefficient of the combination of the first alloy and the second alloy forming the absorption layer 130 fall within the ranges described below. Fig. 9 , and the absorption layer 130 will provide the desired level of phase shift and the desired level of reflectivity. When the thickness of the absorption layer 130, the first material 131 layer, and the second material 133 layer exceed the aforementioned range, the refractive index and extinction coefficient of the combination of the first alloy and the second alloy may not fall within the red region 902, and the absorption layer 130 may not provide the desired level of phase shift, nor the desired level of reflectivity. The embodiments according to the present disclosure are not limited to the aforementioned combined thickness of the first alloy layer and the second alloy layer. For example, the combined thickness of the first alloy layer may exceed the aforementioned range, and the combined thickness of the second material layer may also exceed the aforementioned range.

[0060] for Figure 3F The above description of the capping layer 120 and the buffer layer 125 is also applicable to the embodiment shown in FIG. Figure 3F The capping layer 120 and buffer layer used in the illustrated embodiment.

[0061] In another embodiment, the absorption layer 130 is formed as a single layer of an alloy 135 of the first material and the second material. The alloy 135 is a substance composed of two or more metals or metals and non-metals that are closely combined by melting together and dissolving each other when melting. Figure 3G An example of such an implementation of the present disclosure is shown. Figure 3G In some embodiments shown, the absorber layer 130 includes an alloy 135 of a first material and a second material, and the total thickness thereof is between 15-75 nanometers. In other embodiments, the combined thickness of the absorber layer 130 is between 20-50 nanometers. Embodiments according to the present disclosure are not limited to the aforementioned thicknesses, for example, Figure 3G The thickness of the absorption layer shown can exceed the aforementioned range. In some embodiments, the atomic % of the first material in the alloy is between 20% and 75%. The embodiments according to the present disclosure are not limited to alloys having the aforementioned atomic % of the first material. For example, the embodiments according to the present disclosure include alloys having an atomic content of the first material less than 20 atomic % or greater than 75 atomic %. When the atomic % of the first material of the absorption layer 130 falls within the aforementioned range, the refractive index and extinction coefficient of the combination of the first material and the second material fall within the range described below. Fig. 9 The absorption layer 130 is preferably within the red region 902, and the absorption layer will provide the desired level of phase shift and the desired level of reflectivity. When the atomic % of the first material in the alloy forming the absorption layer 130 exceeds the aforementioned range, the refractive index and extinction coefficient of the absorption layer 130 may not fall within the red region 902, and may not provide the desired level of phase shift and / or the desired level of reflectivity. Figure 3G The illustrated embodiment is not limited to the atomic % of the first material of the absorber layer 130 being within the aforementioned range. Figure 3G The atomic % of the first material in the absorption layer may be higher or lower than the aforementioned range.

[0062] for Figure 3G The above description of the capping layer 120 and the buffer layer 125 is also applicable to the embodiment shown in FIG. Figure 3G The capping layer 120 and buffer layer used in the illustrated embodiment.

[0063] according to Figure 3GIn some embodiments, exemplary alloys 135 for the absorber layer 130 are as follows. In some embodiments, the alloy 135 used in the absorber layer 130 includes RhPd, RhAg, RhPt, RhAu, RhCo, RhNi, RhIr, RhTe, RhCr, RhTa, RhAl, RhPdN, RhAgN, RhPtN, RhAuN, RhCoN, RhNiN, RhIrN, RhTeN, RhCrN, RhTaN, RhAlN, RhPdB, RhAgB, RhPtB, RhAuB, RhCoB, RhNiB, RhIrB, RhTeB, RhCrB, RhTaB, and RhAlB. In other embodiments, the alloy 135 of the absorber layer 130 includes oxygen, nitrogen, and / or boron. For example, the alloy 135 used in the absorption layer 130 includes RhPdO, RhAgO, RhPtO, RhAuO, RhCoO, RhNiO, RhIrO, RhTeO, RhCrO, RhTaO, RhAlO, RhPdON, RhAgON, RhPtON, RhAuON, RhCoON, RhNiON, RhIrON, RhTeON, RhCrON, RhTaON, RhAlON, RhPdOB, RhAgOB, RhPtOB, RhAuOB, RhCoOB, RhNiOB, RhIrOB, RhTeOB, RhCrOB, RhTaOB and RhAlOB.

[0064] Fig. 9 is a plot of extinction coefficient k versus refractive index n for a first material and a second material according to some embodiments of the present disclosure, which may be used as materials to form alloys for use in an absorber layer or as materials to repair defects in an absorber layer. The plotted n and k values ​​are for EUV radiation centered at 13.5 nanometers and are determined in a 0th order approximation using atomic scattering factors. Another source of these n and k values ​​is a database of such values ​​maintained by the Center for X-Ray Optics (CXRO) of the Materials Sciences Division at Lawrence Berkeley National Laboratory. Fig. 9 The drawing in FIG. 1 includes a “red area” 902 identified by a border 900. The red area 902 is Fig. 9 The polygon in the drawing is defined as including four corners 904, 906, 908 and 910. These four corners correspond to Fig. 9 The specific coordinates of the refractive index n and the extinction coefficient k coordinates (n, k). Fig. 9In some embodiments, the four coordinates are (0.880, 0.030) 904, (0.880, 0.050) 906, (0.900, 0.050) 908, and (0.900, 0.030) 910. As will be explained in more detail below, the red region 902 is used to identify a combination of a first material and a second material that would provide an alloy for use in the absorber layer 130 that meets the APSM standard of a refractive index between 0.88-0.9, an extinction coefficient between 0.03-0.05, and a thickness between 20-50 nm or a thickness between 15-70 nm. In some embodiments, the first material and the second material are selected so that Fig. 9 The line connecting the refractive index and extinction coefficient coordinates of the two materials in at least one embodiment passes through a portion of polygon 902 (e.g., through red region 902). Fig. 9 , the line connecting the refractive index and extinction coefficient coordinates of the first material rhodium (Rh) and the second material tellurium (Te) passes through a portion of the red region 902. Similarly, the line connecting the coordinates of rhodium and gold (Au), the line connecting the coordinates of rhodium and platinum (Pt), the line connecting the coordinates of rhodium and tantalum (Ta), and the line connecting the coordinates of rhodium and silver (Ag) pass through a portion of the red region 902. The combination of the first material and the second material that meets the aforementioned criteria is selected to provide an absorption layer for the APSM that exhibits satisfactory phase shift and reflectivity performance while effectively reducing the M3D effect before and after the repair process is performed. 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 the absorption layer. The combination of the first material and the second material that does not meet the aforementioned criteria may not provide an absorption layer that exhibits satisfactory phase shift and reflectivity performance while effectively reducing the M3D effect. The combination of the first material and the second material that does not meet the aforementioned criteria may not be used to repair defects in the absorption layer of the APSM.

[0065] The absorption layer 130 is formed by a deposition technique such as PVD, CVD, ALD, RF magnetron sputtering, DC magnetron sputtering, or IBD. When oxygen, nitrogen, or boron is to be included in the alloy of the absorption layer 130, the oxygen, nitrogen, or boron may be implanted into the deposited alloy that does not contain oxygen, nitrogen, or boron. Alternatively, the target material for the physical vapor deposition process may include a material containing oxygen, nitrogen, or boron, for example, RhN, PdN, RhO, PdO, RhB, and PdB.

[0066] In the embodiments of the present disclosure, by deploying the absorber layer material as described above, the mask 3D effect caused by the EUV phase distortion of the EUV mask can be reduced. Therefore, the size-dependent focus offset and pattern placement error can be reduced, and the ideal spatial image contrast can be achieved, such as the ideal normalized image logarithmic slope (NILS).

[0067] Reference Figure 2 and Figure 3D , the method 200 proceeds to operation 208 , where a hard mask layer 140 is deposited over the absorber layer 130 , according to some embodiments. Figure 3D According to some embodiments, after depositing a hard mask layer 140 on the absorber layer 130 Figure 3C Cross-sectional view of the structure shown.

[0068] Reference Figure 3D A hard mask layer 140 is disposed on the absorption layer 130. The hard mask layer 140 has different etching characteristics from the absorption layer 130, the buffer layer 125, and the capping layer 130, and thus, as an etching stop layer, allows the absorption layer 130, the buffer layer 125, and the capping layer 120 to be selectively etched. Figure 3DIn the illustrated embodiment, the hard mask layer 140 is shown as a single layer. In other embodiments, the hard mask layer 140 includes two or more sublayers of dissimilar materials. For example, in some embodiments, the hard mask layer 140 includes two sublayers, three sublayers, or four sublayers of dissimilar materials. According to embodiments of the present disclosure, different combinations of hard mask sublayers and buffer layers produce improved patterning using dry etching. Several materials for the buffer layer have been described above. Materials that can be used in the sublayers of the hard mask layer 140 include dielectric materials such as CrO, GaN, CrON, CrCON, SiO, SiCO, Y2O3, SiCO, SiCON, SiN, TaBO, TaBN, TaN, Ta2O5, TaO2, TaO, Ta2O, MoSi, MoSiN, MoSiO, SiN, SiON, SiO2, SiCON, SiC, and SiCN. As described above, when two or more sublayers are used to form the hard mask layer 140, the material used in one sublayer is different from the material used in the other sublayer. For example, in some embodiments of the hard mask layer 140 including two sublayers, the first sublayer includes one or more of GaN, CrON, CrCON, SiO, SiCO, Y2O3, SiCO, or SiCON, and the second sublayer includes one or more of TaBO, TaBN, TaN, Ta2O5, TaO2, TaO, Ta2O, MoSi, MoSiN, MoSiO, SiN, SiON, SiO2, SiCON, SiC, or SiCN. In such a two-sublayer embodiment, the thickness of the first sublayer is between 2-20nm, and the thickness of the second sublayer is between 2-20nm. The embodiments according to the present disclosure are not limited to the first sublayer and the second sublayer of the hard mask layer 140 having such thicknesses. For example, the thickness of the first sublayer and the second sublayer may be less than 2nm or greater than 20nm. If the thickness of the sub-layer is too small, the hard mask will not be able to protect portions of the absorber layer 130, buffer layer 125, or capping layer 120 from the exposure and etching processes used to pattern the absorber layer 130, buffer layer 125, and capping layer 120. If the thickness of the sub-layer is too large, patterning of the sub-layer will become more difficult, resulting in less precise patterning of the hard mask sub-layer, which may result in less defined or inaccurate features formed in the absorber layer 130, buffer layer 125, and / or capping layer 120.

[0069] In some embodiments of the hard mask layer 140 according to the disclosed embodiments, the hard mask layer 140 includes three sublayers, the first sublayer includes one or more of GaN, CrON, CrCON, SiO, SiCO, Y2O3, SiCO, or SiCON; the second sublayer includes one or more of TaBO, Ta2O5, TaO2, TaO, Ta2O, MoSiO, SiON, SiO2, or SiCON; and the third sublayer includes one or more of TaBN, TaN, MoSi, MoSiN, SiN, SiC, or SiCN. In such three-sublayer embodiments, the first sublayer has a thickness between 2-20 nm, the second sublayer has a thickness between 2-20 nm, and the third sublayer has a thickness between 2-20 nm. The embodiments according to the present disclosure are not limited to the first sublayer, the second sublayer, and the third sublayer of the hard mask layer 140 having such thicknesses. For example, the thicknesses of the first sublayer, the second sublayer, and the third sublayer may be less than 2 nm or greater than 20 nm. If the thickness of the sub-layer is too small, the hard mask will not be able to protect portions of the absorber layer 130, buffer layer 125, or capping layer 120 from the exposure and etching processes used to pattern the absorber layer 130, buffer layer 125, and capping layer 120. If the thickness of the sub-layer is too large, patterning of the sub-layer will become more difficult, resulting in less defined or accurate patterning of the hard mask sub-layer, which will be transferred to features formed in the absorber layer 130, buffer layer 125, and / or capping layer 120.

[0070] In some embodiments of the hard mask layer 140 according to the disclosed embodiments, the hard mask layer 140 includes four sublayers, the first sublayer includes one or more of CrON, CrCON, SiO, SiCO, Y2O3, SiCO, or SiCON; the second sublayer includes one or more of TaBO, Ta2O5, TaO2, TaO, Ta2O, MoSiO, SiON, SiO2, or SiCON; the third sublayer includes one or more of TaBN, TaN, MoSi, MoSiN, SiN, SiC, or SiCN; and the fourth sublayer includes one or more of CrN or Cr2N. In such a four-sublayer embodiment, the first sublayer has a thickness between 2-20 nm, the second sublayer has a thickness between 2-20 nm, the third sublayer has a thickness between 2-20 nm, and the fourth sublayer has a thickness between 2-20 nm. Embodiments according to the present disclosure are not limited to the first, second, third, and fourth sublayers of the hard mask layer 140 having such thicknesses. For example, the thickness of the first sublayer, the second sublayer, the third sublayer, and the fourth sublayer can be less than 2 nm or greater than 20 nm. If the thickness of the sublayer is too small, the hard mask will not be able to protect the portions of the absorption layer 130, the buffer layer 125, or the capping layer 120 from the exposure and etching processes used to pattern the absorption layer 130, the buffer layer 125, and the capping layer 120. If the thickness of the sublayer is too large, the patterning of the sublayer will become more difficult, resulting in the patterning of the hard mask sublayer being less clear or inaccurate, which will be transferred to the features formed in the absorption layer 130, the buffer layer 125, and / or the capping layer 120.

[0071] In some embodiments, the sub-layers of the hard mask layer 140 are formed using a deposition process such as, for example, CVD, PECVD, or PVD.

[0072] In some embodiments, the upper surface of the absorber layer includes an oxide, for example, an intentionally formed oxide. Such an oxide can be formed by oxidizing the upper surface of the absorber layer, or the oxide can be deposited / formed on the upper surface of the absorber layer. In other embodiments, the oxide can be dispersed in the absorber layer, thereby providing at least a portion of the oxygen present in some embodiments of the absorber layer material. In some embodiments, the native oxide is formed after the absorber layer is formed, for example, during the process of etching the absorber layer to pattern it, or during the process of removing the hard mask layer. Such a native oxide can be a thin layer having a thickness of less than 10 nanometers (for example, 0.5-5 nanometers thick). The thickness of such a native oxide layer may not be uniform. In such cases, in order to improve the uniformity of the oxide layer thickness, the intentionally formed oxide layer can be formed as described above. After the oxide layer is intentionally formed, the oxide layer has a uniform thickness between 20 and 50 nanometers.

[0073] Figure 4 4 is a cross-sectional view of an EUV mask 400 formed by patterning the absorption layer 130 of the above EUV mask blank 100 according to the second aspect of the present disclosure. Figure 4 The EUV mask 400 includes a substrate 102, a reflective multilayer stack 110 on the front surface of the substrate 102, and a capping layer 120 (on the Figure 4 The EUV mask 400 further includes a conductive layer 104 on a rear surface opposite to the front surface of the substrate 102.

[0074] The patterned absorption layer 130P includes an opening pattern 152, which corresponds to a feature pattern to be formed on the semiconductor wafer. The opening pattern 152 is located in the pattern area 400A of the EUV mask 400, exposing the surface of the capping layer 120. The pattern area 400A is surrounded by the peripheral area 400B of the EUV mask 400. The peripheral area 400B corresponds to the non-patterned area of ​​the EUV mask 400, which is not used for the exposure process during the IC manufacturing process. In some embodiments, the pattern area 400A of the EUV mask 400 is located in the central area of ​​the substrate 102, and the peripheral area 400B is located at the edge portion of the substrate 102. The pattern area 400A is separated from the peripheral area 400B by a groove 154. The groove 154 extends through the patterned absorption layer 130P, the buffer layer 125, the capping layer 120, and the reflective multilayer stack 110, exposing the front surface of the substrate 102.

[0075] 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 will be 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 these operations are replaced and / or eliminated. In some embodiments, some of the features described below are replaced or eliminated. It will be appreciated by those of ordinary skill in the art that although the operations are performed in a particular order when discussing some embodiments, the operations may be performed in another logical order.

[0076] Reference Figure 5 and Fig. 6AThe method 500 includes operation 502 , in which a photoresist layer 610 is deposited over a hard mask layer formed by a first hard mask sublayer 140 a on the absorption layer 130 and a second hard mask layer 140 b on the first hard mask sublayer 140 a , according to some embodiments. Fig. 6A 6 is a cross-sectional view of the structure after deposition of a photoresist layer 610 over the hard mask sublayers 140a and 140b according to some embodiments. The formation of the mask is discussed below with reference to a hard mask layer including two sublayers 140a and 140b. As described above, the hard mask layer can include more than two sublayers of material. When the hard mask layer includes more than two sublayers, the steps described herein for forming and patterning the first sublayer 140a and the second sublayer 140b are applicable to the additional sublayers of the hard mask layer 140.

[0077] Reference Fig. 6A , a photoresist layer 610 is disposed on the uppermost surface of the EUV mask blank 100 (i.e., the upper surface of the sublayer 140b of the hard mask layer 140). The photoresist layer 610 includes a photosensitive material that can be patterned by radiation. In some embodiments, the photoresist layer 610 includes a positive-tuning photoresist material, a negative-tuning photoresist material, or a hybrid-tuning photoresist material. In some embodiments, the photoresist layer 610 can be applied to the surface of the hard mask layer 140b by spin coating or the like.

[0078] Reference Figure 5 and Figure 6B , the method 500 proceeds to operation 504 , in which the photoresist layer 610 is photolithographically patterned to form a patterned photoresist layer 610P according to some embodiments. Figure 6B According to some embodiments, the photoresist layer 610 is patterned by photolithography to form a patterned photoresist layer 610P. Fig. 6A Cross-sectional view of the structure shown.

[0079] Reference Figure 6B First, the photoresist layer 610 is placed under the irradiation pattern to pattern the photoresist layer 610. Next, depending on whether a positive tone photoresist or a negative tone photoresist is used in the photoresist layer 610, a photoresist developer is used to remove the exposed or unexposed portion of the photoresist layer 610, thereby forming a patterned photoresist layer 610P in which an opening pattern 612 is formed. The opening 612 exposes a portion of the hard mask sublayer 140b. The opening 612 is located in the pattern area 400A and corresponds to the position where the opening pattern 152 exists in the EUV mask 400A ( Figure 4 ).

[0080] Reference Figure 5 and Figure 6C, the method 500 proceeds to operation 506 , where the sub-layers 140 b and 140 a of the hard mask layer 140 are etched using the patterned photoresist layer 610P as an etch mask to form a patterned hard mask layer 140P, according to some embodiments. Figure 6C After etching the sub-layers 140b and 140a of the hard mask layer 140 to form a patterned hard mask layer 140P according to some embodiments Figure 6B Cross-sectional view of the structure shown.

[0081] Reference Figure 6C , portions of the sub-layers 140b and 140a of the hard mask layer 140 exposed by the opening 612 are etched away to form an opening 142 extending through the patterned hard mask layer 140P. The opening 142 exposes a portion of the underlying absorber layer 130. In some embodiments, the sub-layers 140b and 140a of the hard mask layer 140 are etched using an anisotropic etch. In some embodiments, the anisotropic etch is a dry etch (such as, for example, a reactive ion etch (RIE)), a wet etch, or a combination thereof. The etch will remove the material providing the sub-layers 140b and 140a of the hard mask layer 140 and selectively remove the material providing the absorber layer 130. The remaining portions of the hard mask layers 140a and 140b constitute the patterned hard mask layer 140P. If the patterned photoresist layer 610P is 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 after etching the hard mask layers 140a and 140b, for example, using wet stripping or plasma ashing.

[0082] Reference Figure 5 and Fig.6D 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, according to some embodiments. Fig.6D According to some embodiments, after etching the absorption layer 130 to form a patterned absorption layer 130P Figure 6C Cross-sectional view of the structure shown.

[0083] Reference Fig.6D, the portion of the absorption layer 130 exposed through the opening 142 is etched away to form an opening 132 extending through the absorption layer 130. In some embodiments, this etching exposes a portion of the underlying buffer layer 125. The opening 132 in the patterned absorption layer 130P defines an opening pattern 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 dry etching (such as, for example, RIE), wet etching, or a combination thereof, which can selectively remove the material providing the absorption layer 130 to the material providing the underlying buffer layer 125. For example, in some embodiments, the absorption layer 130 is dry etched with a chlorine-containing gas (such as Cl2 or BCl3) or a fluorine-containing gas (such as NF3). Argon (Ar) can be used as a carrier gas. In some embodiments, oxygen (O2) can also be used as a carrier gas. The etching rate and etching selectivity depend on the etchant gas, etchant flow rate, power, pressure, and substrate temperature. After etching, the remaining portion of the absorption layer 130 constitutes the patterned absorption layer 130P. Then, the portion of the buffer layer 125 exposed through the opening 142 is etched to selectively remove the exposed portion of the buffer layer to the remaining portion of the underlying capping layer 120 and the patterned absorption layer 130P. Fig.6D The patterned buffer layer 125P is shown. Fig.6D Not shown, but in some embodiments according to the present disclosure, the portion of the capping layer 120 exposed through the opening 132 may be etched to expose the upper surface of the reflective multilayer stack 110 .

[0084] Reference Figure 5 and Fig. 6E The method 500 proceeds to operation 510 , where a patterned photoresist layer 620P including an opening pattern 622 is formed over the patterned hard mask layer 140P, the patterned buffer layer 125P, and the capping layer 120 , according to some embodiments. Fig. 6E According to some embodiments, after forming a patterned photoresist layer 620P including an opening 622 on the patterned hard mask layer 140P, the patterned buffer layer 125P, and the capping layer 120 Fig.6D Cross-sectional view of the structure shown.

[0085] Reference Fig. 6E , the opening 622 exposes a portion of the sublayer 140b of the patterned hard mask layer 140P at the periphery of the patterned absorber layer 130P. The opening 622 corresponds to the trench 154 in the peripheral region 400B of the EUV mask 400 ( Figure 4). To form the patterned photoresist layer 620P, a photoresist layer (not shown) is applied on the patterned hard mask layer 140P and the capping layer 120. The photoresist layer fills the openings 142 in the patterned hard mask layer 140P and the openings 132 in the patterned absorption layer 130P and the patterned buffer layer 125P. In some embodiments, the photoresist layer includes a positive-tuning photoresist material, a negative-tuning photoresist material, or a hybrid-tuning photoresist material. In some embodiments, the photoresist layer includes Fig. 6A In some embodiments, the photoresist layer includes a material different from the photoresist layer 610. In some embodiments, the photoresist layer is formed by spin coating or the like. Subsequently, the photoresist layer is patterned by exposing the photoresist layer to a radiation pattern and removing the exposed or unexposed portions of the photoresist layer using a photoresist developer (depending on whether a positive photoresist or a negative photoresist is used). The remaining portion of the photoresist layer constitutes the patterned photoresist layer 620P.

[0086] Reference Figure 5 and Fig. 6F , method 500 proceeds to operation 512, in which, according to some embodiments, the patterned photoresist layer 620P is used as an etching mask to etch the patterned hard mask layer 140P, the patterned absorption layer 130P, the patterned buffer layer 125P, the capping layer 120, and the reflective multilayer stack 110 to form a groove 154 in the peripheral area 400B of the substrate 102. Fig. 6F According to some embodiments, the patterned hard mask layer 140P, the patterned absorption layer 130P, the patterned buffer layer 125P, the capping layer 120, and the reflective multilayer stack 110 are etched to form the trench 154 in the peripheral region 400B of the substrate 102. Fig. 6E Cross-sectional view of the structure shown.

[0087] Reference Fig. 6F The trench 154 extends through the sub-layers 140b and 140a of the patterned hard mask layer 140P, the patterned absorption layer 130P, the patterned buffer layer 125P, 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.

[0088] In some embodiments, the patterned hard mask layer 140P, the patterned absorption layer 130P, the patterned buffer layer 125P, the capping layer 120, and the reflective multilayer stack 110 are etched using a single anisotropic etching process. The anisotropic etching can be a dry etch (such as, for example, RIE), a wet etch, or a combination thereof, which selectively removes the exposed portions of the material of the corresponding patterned hard mask layer 140P, the patterned absorption layer 130P, the patterned buffer layer 125P, the capping layer 120, and the reflective multilayer stack 110 to provide the material of the substrate 102. In some embodiments, the patterned hard mask layer 140P, the patterned absorption layer 130P, the patterned buffer layer 125P, the capping layer 120, and the reflective multilayer stack 110 are etched using a plurality of different anisotropic etching processes. Each anisotropic etching can be a dry etch (such as, for example, RIE), a wet etch, or a combination thereof.

[0089] Subsequently, the patterned photoresist layer 620P is removed from the patterned region 400A and the peripheral region 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 and the patterned buffer layer 125P re-exposes the surface of the capping layer 120 in the patterned region 400A.

[0090] Reference 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, the patterned hard mask layer 140P is removed. Fig. 6F Cross-sectional view of the structure shown.

[0091] Reference Figure 6G , removing the patterned hard mask layer 140P exposes the surface of the patterned absorption layer 130P. In some embodiments, the sublayers 140b and 140a of the patterned hard mask layer 140P are removed by an etching process, and the etching process can be anisotropic etching or isotropic etching. In some embodiments, the etching can be dry etching (such as, RIE) or wet chemical etching, which can selectively remove the sublayers of the patterned hard mask layer 140P without removing the remaining patterned absorption layer 130P, the patterned buffer layer 125P, the capping layer 120, the reflective multilayer stack 110, and the substrate 102.

[0092] After removing the patterned hard mask layer 140P, the EUV mask 400 can be cleaned to remove any contaminants. 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.

[0093] Subsequently, the EUV mask 400 is irradiated with UV light, for example, having a wavelength of 193 nm, to inspect any defects in the patterned region 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.

[0094] The patterned absorption layer 130P includes an alloy of a first material and a second material, and the alloy has a combination of refractive index, EUV extinction coefficient and thickness characteristics to form an absorption layer that reduces the 3D effect of the mask. Therefore, the pattern on the EUV mask 400 can be accurately projected onto the semiconductor wafer.

[0095] Figure 7 is 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", which can perform a lithography exposure process using a corresponding radiation source and an exposure mode.

[0096] 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 modular component.

[0097] High brightness light source 702 can be configured to emit radiation having a wavelength in the range of about 1 nanometer (nm) to 250 nm. In some embodiments, high brightness light source 702 generates EUV light having a wavelength centered at about 13.5 nm; therefore, high brightness light source 702 can also be referred to as an "EUV light source."

[0098] In the 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 multiple mirrors. The illuminator 704 can direct the light from the high brightness light source 702 onto the mask stage 706, especially onto the EUV mask 400 fixed on the mask stage 706.

[0099] The mask stage 706 may be configured to fix the EUV mask 400. In some examples, the mask stage 706 may include an electrostatic chuck (e-chuck) for fixing the EUV mask 400.

[0100] In some examples, a pellicle 714 may be disposed over the EUV mask 400, for example, between the EUV mask 400 and the substrate stage 712. The pellicle 714 may protect the EUV mask 400 from particles and may prevent the particles from being focused so that the particles do not generate an image that may cause defects on the wafer during the lithography process.

[0101] 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. The projection optical module 710 can collect light guided by the EUV mask 400 that carries an image of the pattern defined on the EUV mask 400. The illuminator 704 and the projection optical module 710 can be collectively referred to as an "optical module" of the lithography system 700.

[0102] In some embodiments, the semiconductor wafer 716 may be a bulk semiconductor wafer. For example, the semiconductor wafer 716 may include a silicon wafer. The semiconductor wafer 716 may include silicon or another elemental semiconductor material, such as germanium. In some embodiments, the semiconductor wafer 716 may include a compound semiconductor. The compound semiconductor may include gallium arsenide, silicon carbide, indium arsenide, indium phosphide, another suitable material, or a combination thereof. In some embodiments, the 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, the semiconductor wafer 716 includes an undoped substrate. However, in other embodiments, the semiconductor wafer 716 includes a doped substrate, such as a p-type substrate or an n-type substrate.

[0103] In some embodiments, the semiconductor wafer 716 includes various doped regions (not shown) according to 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 doped regions are p-type doped regions, while other doped regions are n-type doped regions.

[0104] In some embodiments, an interconnect structure may be formed on 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 lines, conductive through-holes, and / or conductive contacts.

[0105] 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 the various device elements, including deposition, etching, implantation, photolithography, annealing, and / or other suitable processes.

[0106] The device elements may be interconnected through an interconnect structure on 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.

[0107] In some embodiments, a photoresist sensitive to EUV light may be coated on the semiconductor wafer 716. Various components including the above components may be integrated together, and a photolithography exposure process may be performed.

[0108] 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, a portion of the incident radiation reflected by the reflective multilayer stack 110 is directed onto a photoresist disposed on a semiconductor wafer. After the photoresist to be patterned is exposed to the radiation reflected from the EUV mask 400, the portions of the photoresist that are exposed or not exposed to the radiation reflected from the EUV mask 400 are removed in step 810. In step 812, the pattern in the patterned photoresist is transferred to the semiconductor wafer.

[0109] 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 capping layer on the reflective multilayer stack, a buffer layer on the capping layer, and a patterned absorption layer on the buffer layer. The patterned absorption layer has a thickness between 10-50 nanometers and includes an alloy of a first material and a second material, wherein the first material is rhodium (Rh) having an EUV refractive index (n) and an EUV extinction coefficient (k), and wherein the second material is a transition metal of Group 5, Group 6, Group 9, Group 10, or Group 11, whose EUV refractive index (n) is greater than the EUV refractive index (n) of rhodium, and whose EUV extinction coefficient (k) is greater than the EUV extinction coefficient (k) of rhodium.

[0110] Another aspect of the present specification relates to a method for forming an EUV mask. The method includes providing an EUV mask blank including a reflective multilayer stack on a substrate. The EUV mask blank also includes a capping layer on the multilayer stack and a buffer layer on the capping layer. According to this aspect of the present disclosure, there is an absorption layer on the buffer layer of the mask blank. The thickness of the absorption layer is between 20-50 nanometers, and the absorption layer includes an alloy of a first material and a second material. The first material is rhodium (Rh) having an EUV refractive index (n) and an EUV extinction coefficient (k). The second material is a transition metal of Group 5, Group 6, Group 9, Group 10 or Group 11, whose EUV refractive index (n) is greater than the EUV refractive index (n) of rhodium, and whose EUV extinction coefficient (k) is greater than the EUV extinction coefficient (k) of rhodium. The method includes the step of patterning the absorption layer to form a patterned absorption layer 130P.

[0111] 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 capping layer on the reflective multilayer stack, a buffer layer on the capping layer, and a patterned absorption layer on the buffer layer. The patterned absorption layer includes an alloy of a first material and a second material, the first material having an EUV refractive index (n) and an EUV extinction coefficient (k), and the second material having an EUV refractive index (n) and an EUV extinction coefficient (k). According to this aspect of the present disclosure, in a plot of the EUV refractive index (n) and the EUV extinction coefficient (k) of a first material and a second material, a line between a first material coordinate defined by the EUV refractive index (n) and the EUV extinction coefficient (k) of the first material and a second material coordinate defined by the EUV refractive index (n) and the EUV extinction coefficient (k) of the second material passes through a polygon defined in the plot of the four coordinates (n, k), which are (0.880, 0.030), (0.880, 0.050), (0.900, 0.050), and (0.900, 0.030), respectively.

[0112] The present application also includes the following exemplary embodiments:

[0113] Embodiment 1. An extreme ultraviolet (EUV) mask, comprising:

[0114] substrate;

[0115] a reflective multilayer stack on the substrate;

[0116] a capping layer on the multi-layer stack;

[0117] A buffer layer on the capping layer; and

[0118] A patterned absorption layer with a thickness between 20-50 nanometers on the buffer layer, wherein the patterned absorption layer comprises an alloy of a first material and a second material, wherein the first material is rhodium (Rh) having an EUV refractive index (n) and an EUV extinction coefficient (k), and wherein the second material is a transition metal of Group 5, Group 6, Group 9, Group 10 or Group 11, whose EUV refractive index (n) is greater than the EUV refractive index (n) of rhodium, and whose EUV extinction coefficient (k) is greater than the EUV extinction coefficient (k) of rhodium.

[0119] Embodiment 2. The EUV mask according to embodiment 1, wherein the second material is a period 4, period 5, or period 6 transition metal.

[0120] Embodiment 3. The EUV mask of embodiment 1, wherein the alloy includes one or more of oxygen (O), nitrogen (N), or boron (B).

[0121] Embodiment 4. The EUV mask according to embodiment 3, wherein the alloy includes oxygen (O) and one of nitrogen (N) or boron (B).

[0122] Embodiment 5. The EUV mask of embodiment 1, wherein the alloy provides a phase shift between 1.17π and 1.2π.

[0123] Embodiment 6. The EUV mask of embodiment 1, wherein the alloy contains 10-75 atomic % rhodium.

[0124] Embodiment 7. The EUV mask according to embodiment 3, wherein the alloy contains 2-20 atomic % of oxygen (O), nitrogen (N), boron (B), or a combination thereof.

[0125] Embodiment 8. The EUV mask of embodiment 1, wherein the alloy forms a first sublayer of the patterned absorber layer, and the patterned absorber layer further comprises a second sublayer comprising an alloy of rhodium (Rh).

[0126] Embodiment 9. The EUV mask of embodiment 8, wherein the alloy of rhodium of the second sub-layer comprises a Group 5, Group 6, Group 9, Group 10, or Group 11 transition metal.

[0127] Embodiment 10. The EUV mask according to embodiment 9, wherein the alloy of rhodium of the second sub-layer includes nitrogen (N) or boron (B), but does not include oxygen (O).

[0128] Embodiment 11. The EUV mask of embodiment 1, wherein the EUV refractive index (n) of rhodium is approximately equal to 0.875 and the EUV extinction coefficient (k) of rhodium is approximately equal to 0.031.

[0129] Embodiment 12. An extreme ultraviolet (EUV) mask comprising:

[0130] substrate;

[0131] a reflective multilayer stack on the substrate;

[0132] a capping layer on the multilayer stack; and

[0133] A patterned absorption layer on the capping layer, the patterned absorption layer comprising an alloy of a first material and a second material, the first material having an EUV refractive index (n) and an EUV extinction coefficient (k), and the second material having an EUV refractive index (n) and an EUV extinction coefficient (k), wherein, in a plot of the EUV refractive index (n) and the EUV extinction coefficient (k) of the first material and the second material, a line between a first material coordinate defined by the EUV refractive index (n) and the EUV extinction coefficient (k) of the first material and a second material coordinate defined by the EUV refractive index (n) and the EUV extinction coefficient (k) of the second material passes through a polygon defined in the plot of four coordinates (n, k), the four coordinates being (0.880, 0.030), (0.880, 0.050), (0.900, 0.050) and (0.900, 0.030), respectively.

[0134] Embodiment 13. The EUV mask according to embodiment 12, wherein the first material includes rhodium (Rh), and the second material is a transition metal of Group 5, Group 6, Group 9, Group 10, or Group 11 in the periodic table.

[0135] Embodiment 14. An extreme ultraviolet mask according to embodiment 13, wherein the second material includes one or more transition metals selected from tantalum (Ta), chromium (Cr), cobalt (Co), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), silver (Ag) and gold (Au).

[0136] Embodiment 15. The EUV mask according to embodiment 12, wherein the first material includes rhodium (Rh), and the second material is aluminum (Al) or tellurium (Te).

[0137] Embodiment 16. The EUV mask of embodiment 12, wherein the alloy comprises one or more of oxygen (O), nitrogen (N), or boron (B).

[0138] Embodiment 17. An extreme ultraviolet mask according to embodiment 12, wherein the patterned absorption layer includes a first sublayer, the first sublayer includes an alloy of the first material and the second material, and the patterned absorption layer also includes a second sublayer, the second sublayer includes an alloy of rhodium (Rh).

[0139] Embodiment 18. The EUV mask of embodiment 17, wherein the alloy of rhodium of the second sub-layer comprises a Group 5, Group 6, Group 9, Group 10, or Group 11 transition metal.

[0140] Embodiment 19. A method of forming an EUV mask, comprising the following steps:

[0141] An EUV mask blank is provided, wherein the EUV mask blank comprises:

[0142] Reflective multilayer stack on substrate,

[0143] a capping layer on the multilayer stack,

[0144] a buffer layer on the capping layer, and

[0145] an absorbing layer on the buffer layer, wherein the absorbing layer has a thickness between 20-50 nanometers, and wherein the absorbing layer comprises an alloy of a first material and a second material, wherein the first material is rhodium (Rh) having an EUV refractive index (n) and an EUV extinction coefficient (k), and wherein the second material is a Group 5, Group 6, Group 9, Group 10, or Group 11 transition metal, whose EUV refractive index (n) is greater than the EUV refractive index (n) of rhodium, and whose EUV extinction coefficient (k) is greater than the EUV extinction coefficient (k) of rhodium; and

[0146] The absorption layer is patterned to form a patterned absorption layer.

[0147] Embodiment 20. A method according to embodiment 18, wherein, in a plot of the EUV refractive index (n) and the EUV extinction coefficient (k) of rhodium and the second material, a line between a first rhodium coordinate defined by the EUV refractive index (n) and the EUV extinction coefficient (k) of rhodium and a second material coordinate defined by the EUV refractive index (n) and the EUV extinction coefficient (k) of the second material passes through a polygon defined in the plot of four coordinates (n, k), the four coordinates being (0.880, 0.030), (0.880, 0.050), (0.900, 0.050) and (0.900, 0.030), respectively.

[0148] The features of several embodiments are summarized above so that those skilled in the art can better understand the various aspects of the present disclosure. It should be understood by those skilled in the art that they can easily design or modify other processes and structures based on the present disclosure to achieve the same purpose and / or achieve the same advantages of the embodiments described herein. It should also be recognized by those skilled in the art that such equivalent structures do not depart from the spirit and scope of the present disclosure, and they can make various changes, substitutions and modifications to this article without departing from the spirit and scope of the present disclosure.

Claims

1. An extreme ultraviolet (EUV) mask, comprising: substrate; a reflective multilayer stack on said substrate; a capping layer on the multi-layer stack; a buffer layer on the capping layer; as well as A patterned absorption layer with a thickness between 20-50 nanometers on the buffer layer, wherein the patterned absorption layer comprises an alloy of a first material and a second material, wherein the first material is rhodium (Rh) having an EUV refractive index (n) and an EUV extinction coefficient (k), and wherein the second material is a transition metal of Group 5, Group 6, Group 9, Group 10 or Group 11, whose EUV refractive index (n) is greater than the EUV refractive index (n) of rhodium, and whose EUV extinction coefficient (k) is greater than the EUV extinction coefficient (k) of rhodium.

2. The EUV mask according to claim 1, wherein: The second material is a period 4, period 5 or period 6 transition metal.

3. The EUV mask according to claim 1, wherein: The alloy includes one or more of oxygen (O), nitrogen (N), or boron (B).

4. The EUV mask according to claim 3, wherein: The alloy includes oxygen (O) and one of nitrogen (N) or boron (B).

5. The EUV mask according to claim 1, wherein: The alloy provides a phase shift between 1.17π and 1.2π.

6. The EUV mask according to claim 1, wherein: The alloy contains 10-75 atomic % rhodium.

7. The EUV mask according to claim 3, wherein: The alloy contains 2-20 atomic % of oxygen (O), nitrogen (N), boron (B) or a combination thereof.

8. The EUV mask according to claim 1, wherein: The alloy forms a first sublayer of the patterned absorption layer, and the patterned absorption layer further includes a second sublayer including an alloy of rhodium (Rh).

9. An extreme ultraviolet (EUV) mask comprising: substrate; a reflective multilayer stack on said substrate; a capping layer on the multi-layer stack; as well as A patterned absorption layer on the capping layer, the patterned absorption layer comprising an alloy of a first material and a second material, the first material having an EUV refractive index (n) and an EUV extinction coefficient (k), and the second material having an EUV refractive index (n) and an EUV extinction coefficient (k), wherein, in a plot of the EUV refractive index (n) and the EUV extinction coefficient (k) of the first material and the second material, a line between a first material coordinate defined by the EUV refractive index (n) and the EUV extinction coefficient (k) of the first material and a second material coordinate defined by the EUV refractive index (n) and the EUV extinction coefficient (k) of the second material passes through a polygon defined in the plot of four coordinates (n, k), the four coordinates being (0.880, 0.030), (0.880, 0.050), (0.900, 0.050) and (0.900, 0.030), respectively.

10. A method for forming an EUV mask, comprising the following steps: An EUV mask blank is provided, wherein the EUV mask blank comprises: Reflective multilayer stack on substrate, a capping layer on the multilayer stack, a buffer layer on the capping layer, and an absorbing layer on the buffer layer, wherein the absorbing layer has a thickness between 20-50 nanometers, and wherein the absorbing layer comprises an alloy of a first material and a second material, wherein the first material is rhodium (Rh) having an EUV refractive index (n) and an EUV extinction coefficient (k), and wherein the second material is a Group 5, Group 6, Group 9, Group 10, or Group 11 transition metal, whose EUV refractive index (n) is greater than the EUV refractive index (n) of rhodium, and whose EUV extinction coefficient (k) is greater than the EUV extinction coefficient (k) of rhodium; and The absorption layer is patterned to form a patterned absorption layer.

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