EUV photomask and manufacturing method thereof

Abstract

The invention relates to an EUV photomask and a manufacturing method thereof. A method of manufacturing a photomask includes forming a boundary layer over a photomask blank. The photomask blank includes a substrate, a reflective multilayer disposed over the substrate, and an absorber layer disposed over the reflective multilayer. A portion of the boundary layer is removed to form a recess surrounded by the boundary layer, and some portions of the absorber layer are selectively removed in the recess to form a pattern in the absorber layer. The boundary layer has a refractive index ranging from 0.87 to 1 and an extinction coefficient greater than or equal to 0.02.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an EUV photomask and a method of manufacturing the same. BACKGROUND

[0002] Lithography operation is one of the key operations in semiconductor manufacturing process. Lithography techniques include ultraviolet lithography, deep ultraviolet lithography, and extreme ultraviolet lithography (EUVL). Photomask is an important component in lithography operation. It is critical to make an EUV photomask with high contrast having a high reflectivity portion and a high absorption portion. SUMMARY

[0003] According to one embodiment of the present disclosure, a method of manufacturing a photomask is provided, comprising: forming a boundary layer over a photomask blank, wherein the photomask blank comprises: a substrate; a reflective multilayer disposed over the substrate; and an absorber layer disposed over the reflective multilayer; removing a portion of the boundary layer to form a recess surrounded by the boundary layer; and selectively removing some portions of the absorber layer in the recess to form a pattern in the absorber layer, wherein the boundary layer has a refractive index ranging from 0.87 to 1 and an extinction coefficient greater than or equal to 0.02.

[0004] According to one embodiment of the present disclosure, a method of manufacturing a photomask is provided, comprising: forming a boundary layer over a photomask blank, wherein the photomask blank comprises: a substrate; a reflective multilayer disposed over the substrate; and an absorber layer disposed over the reflective multilayer; forming a pattern in a peripheral region of the boundary layer and an opening in a second region of the boundary layer surrounded by the peripheral region, wherein the pattern in the boundary layer comprises at least two spaced-apart grooves and two spaced-apart protrusions on each side of the boundary layer in a cross-sectional view; and selectively removing some portions of the absorber layer in the opening to form a pattern in the absorber layer, wherein the boundary layer comprises at least one selected from a group consisting of: Rh, Pd, Ir, Pt, Co, Ni, Te, Cr, W, Hf, Ta, PtRu, PtIr, PtRh, PtPd, PtNi, PtCo, PtTa, PtCr, PtTi, IrTa, IrCr, IrW, IrTe, IrNi, IrCo, CrN, NiCo, RhCo, RhNi, RhCr, RhW, and RhTa.

[0005] According to one embodiment of the present disclosure, a photomask is provided, comprising: a substrate; a reflective multilayer disposed over the substrate; an absorber layer disposed over the reflective multilayer, including a pattern in the absorber layer; and a boundary layer surrounding the pattern in the absorber layer in a plan view, wherein the refractive index of the boundary layer is in the range of 0.87 to 1, and the extinction coefficient is greater than or equal to 0.02. Attached Figure Description

[0006] This disclosure can be best understood from the following detailed description when read in conjunction with the accompanying drawings. It should be emphasized that, in accordance with industry standard practice, the various features are not drawn to scale but are for illustrative purposes only. In fact, the dimensions of the various features may be arbitrarily increased or decreased for clarity of explanation.

[0007] FIG. 1A and FIG. 1B A photomask blank according to an embodiment of the present disclosure is shown. FIG. 1C and FIG. 1D A photomask according to an embodiment of the present disclosure is shown. FIG. 1E and FIG. 1F A plan view of a photomask according to an embodiment of the present disclosure is shown.

[0008] FIG. 2A and FIG. 2B A photomask blank according to an embodiment of the present disclosure is shown.

[0009] FIG. 3A and FIG. 3B A photomask blank according to an embodiment of the present disclosure is shown.

[0010] FIG. 4A and FIG. 4B A photomask blank according to an embodiment of the present disclosure is shown.

[0011] FIG. 5A , FIG. 5B , FIG. 5C , FIG. 5D , FIG. 5E , FIG. 5F , FIG. 5G , FIG. 5H , FIG. 5I , FIG. 5J , FIG. 5K , FIG. 5L , FIG. 5M and FIG. 5N A method for manufacturing a photomask according to an embodiment of the present disclosure is illustrated schematically.

[0012] FIG. 6A , FIG. 6B , FIG. 6C , FIG. 6D , FIG. 6E, FIG. 6F , FIG. 6G , FIG. 6H , FIG. 6I , FIG. 6J , FIG. 6K , FIG. 6L , FIG. 6M and FIG. 6N A method for manufacturing a photomask according to an embodiment of the present disclosure is illustrated schematically.

[0013] FIG. 7 The illustration shows a photomask according to an embodiment of the present disclosure.

[0014] FIG. 8A , FIG. 8B , FIG. 8C , FIG. 8D , FIG. 8E , FIG. 8F , FIG. 8G , FIG. 8H , FIG. 8I and FIG. 9 Various boundary patterns according to embodiments of this disclosure are shown.

[0015] FIG. 10 A flowchart illustrating a method for manufacturing a photomask is shown.

[0016] FIG. 11 A flowchart illustrating a method for manufacturing a photomask is shown.

[0017] FIG. 12A A flowchart illustrating a method for manufacturing semiconductor devices is shown.

[0018] FIG. 12B A flowchart illustrating a method for manufacturing semiconductor devices is provided, and FIG. 12C , FIG. 12D , FIG. 12E and FIG. 1A The sequential manufacturing operations of a method for fabricating a semiconductor device according to embodiments of the present disclosure are illustrated. Detailed Implementation

[0019] To be understood, the following disclosure provides many different embodiments, or examples, for implementing different features of the invention. To simplify this disclosure, specific embodiments or examples of components and arrangements are described below. These are, of course, merely examples and are not intended to be limiting. For example, the dimensions of elements are not limited to the disclosed range or values, but may depend on process conditions and / or desired characteristics of the device. Furthermore, in the following description, forming a first feature above or on a second feature may include embodiments in which the first and second features are formed in direct contact, or embodiments in which an additional feature is formed between the first and second features such that the first and second features may not be in direct contact. For simplicity and clarity, various features may be drawn at any scale.

[0020] Additionally, spatially related terms, such as “below,” “lower,” “lower,” “higher,” and “upper,” may be used herein for ease of description to describe the relationship between one element or feature as shown in the accompanying drawings and another element(s) or feature(s). Besides the orientations depicted in the drawings, spatially related terms are also intended to cover different orientations of the device during use or operation. The device may be in other orientations (rotated 90 degrees or in other orientations), and the spatially related descriptions used herein may be interpreted similarly accordingly. Furthermore, the term “made of” may mean “comprising” or “constituting of.” In this disclosure, the phrase “one of A, B, and C” means “A, B, and / or C” (A, B, C, A and B, A and C, B and C, or A, B, and C), and not an element from A, an element from B, and an element from C, unless otherwise described. The materials, configurations, processes, and / or dimensions described with respect to one embodiment may be employed in other embodiments, and detailed descriptions thereof may be omitted.

[0021] Embodiments of this disclosure provide methods for manufacturing photomasks. More specifically, this disclosure provides techniques for preventing or suppressing the adjacent die effect.

[0022] In an EUV photomask preform, the thin film stack includes an absorber layer, a capping layer, a reflective multilayer, a low thermal expansion material (LTEM) substrate, and a back conductive film. To mitigate the proximity die effect, a black boundary can be formed in the peripheral region of the photomask preform by forming trenches in the thin film stack around the patterned region of the photomask preform by removing a portion of the absorber layer, capping layer, and reflective multilayer. However, etching of most thin films can introduce flatness variations and defects. Furthermore, two masks are required to expose the pattern and the black boundary, and splicing the two layers is a challenge. To address these issues, in embodiments of this disclosure, a boundary layer is formed above the absorber layer on the extreme ultraviolet (EUV) photomask preform. After the EUV mask formation process, the boundary layer, absorber layer, capping layer, and reflective multilayer remain in the peripheral region. The boundary layer mitigates EUV radiation reflection from the unpatterned region (boundary region or peripheral region) of the EUV mask to the patterned substrate.

[0023] EUV lithography (EUVL) employs a scanner that uses light in the extreme ultraviolet (EUV) region with wavelengths ranging from approximately 1 nm to 100 nm (e.g., 13.5 nm). The mask is a critical component of the EUVL system. In this disclosure, photomasks, masks, and reticles are used interchangeably. Because many optical materials are opaque to EUV radiation, EUV photomasks are often reflective masks. Circuit patterns are formed in an absorber layer disposed above the reflective structure. The absorber layer has a low EUV reflectivity, for example, less than about 3-5%.

[0024] FIG. 1B and FIG. 1C A reflective photomask blank according to an embodiment of the present disclosure is shown. FIG. 1D and FIG. 1E A cross-sectional view is shown of a patterned reflective photomask ready for use in EUV lithography. FIG. 1F and FIG. 1C They are FIG. 1D and FIG. 1A A plan view of a light mask.

[0025] In some embodiments, an EUV photomask with a circuit pattern is formed from a photomask blank 5a. The photomask blank 5a includes a substrate 10, a reflective multilayer Mo / Si stack 15 composed of multiple alternating layers of silicon and molybdenum, a capping layer 20, and an absorber layer 25. Additionally, as... FIG. 1B and FIG. 1A As shown, a back conductive layer 45 is formed on the back side of the substrate 10.

[0026] In some embodiments, the substrate 10 is formed of a low thermal expansion material. In some embodiments, the substrate is a low thermal expansion glass or quartz, such as fused silica or fused silica. In some embodiments, the low thermal expansion glass substrate transmits light of visible wavelengths, a portion of infrared wavelengths (near-infrared) near the visible spectrum, and a portion of ultraviolet wavelengths. In some embodiments, the low thermal expansion glass substrate absorbs extreme ultraviolet wavelengths and deep ultraviolet wavelengths near the extreme ultraviolet. In some embodiments, the substrate 10 has a size of approximately 152 mm × 152 mm (X1 × Y1) and a thickness of approximately 20 mm. In other embodiments, the size of the substrate 10 is less than 152 mm × 152 mm and equal to or greater than 148 mm × 148 mm. In some embodiments, the substrate 10 is square or rectangular in shape.

[0027] In some embodiments, the width of the functional layers (multilayer Mo / Si stack 15, capping layer 20, and absorber layer 25) above the substrate is smaller than the width of the substrate 10. In other embodiments, the absorber layer 25 is smaller than the substrate 10, the multilayer Mo / Si stack 15, and the capping layer 20, ranging from about 138 mm × 138 mm to about 142 mm × 142 mm. When the layers are formed, for example by sputtering, one or more smaller functional layers can be formed by using a frame-shaped cap with openings ranging from about 138 mm × 138 mm to about 142 mm × 142 mm. In other embodiments, all layers above the substrate 10 have the same size as the substrate 10.

[0028] In some embodiments, the Mo / Si multilayer stack 15 comprises from about 30 pairs of alternating silicon and molybdenum layers to about 60 pairs of alternating silicon and molybdenum layers. In some embodiments, about 40 to about 50 pairs of alternating silicon and molybdenum layers are formed. In some embodiments, the reflectivity is greater than about 70% for a wavelength of interest, such as 13.5 nm. In some embodiments, the silicon and molybdenum layers are formed by chemical vapor deposition (CVD), plasma-enhanced CVD (PECVD), atomic layer deposition (ALD), physical vapor deposition (PVD) (including sputtering), ion beam deposition (IBD), or any other suitable film formation method. The thickness of each silicon and molybdenum layer is from about 2 nm to about 10 nm. In some embodiments, the thickness of the silicon and molybdenum layers is substantially the same. In other embodiments, the thickness of the silicon and molybdenum layers is different. In some embodiments, the thickness of each silicon layer is about 4 nm, and the thickness of each molybdenum layer is about 3 nm. In some embodiments, the bottom layer of the multilayer stack 15 is a Si layer or a Mo layer.

[0029] In other embodiments, the multilayer stack 15 comprises alternating molybdenum and beryllium layers. In some embodiments, the number of layers in the multilayer stack 15 ranges from about 20 to about 100, although any number of layers is permissible as long as sufficient reflectivity is maintained for imaging the target substrate. In some embodiments, the reflectivity is greater than about 70% for the wavelength of interest (e.g., 13.5 nm). In some embodiments, the multilayer stack 15 comprises about 30 to about 60 alternating Mo and Be layers. In other embodiments of this disclosure, the multilayer stack 15 comprises about 40 to about 50 alternating Mo and Be layers.

[0030] In some embodiments, the capping layer 20 is disposed over the Mo / Si multilayer stack 15 to prevent oxidation of the multilayer stack 15. In some embodiments, the capping layer 20 is made of elemental ruthenium (more than 99% Ru, not a Ru compound), a ruthenium alloy (e.g., RuNb, RuZr, RuZrN, RuRh, RuNbN, RuRhN, RuV, RuVN, RuIr, RuTi, RuB, RuP, RuOs, RuPd, RuPt, or RuRe), or a ruthenium-based oxide (e.g., RuO2, RuNbO, RuVO, or RuON) with a thickness of about 2 nm to about 10 nm. In some embodiments, the capping layer 20 is a ruthenium compound Ru x M 1-x , where M is at least one of Nb, Ir, Rh, Zr, Ti, B, P, V, Os, Pd, Pt and Re, and x is greater than zero and less than or equal to about 0.5.

[0031] In some embodiments, the thickness of the capping layer 20 is from about 2 nm to about 5 nm. In some embodiments, the thickness of the capping layer 20 is 3.5 nm ± 10%. In some embodiments, the capping layer 20 is formed by CVD, PECVD, ALD, PVD, or any other suitable film formation method. In other embodiments, a Si layer is used as the capping layer 20. In some embodiments, one or more layers are disposed between the capping layer 20 and the multilayer 15.

[0032] In some embodiments, the capping layer 20 comprises two or more layers of different materials. In some embodiments, the capping layer 20 comprises two or more layers of different Ru-based materials. In some embodiments, the capping layer 20 comprises two layers having a lower layer and an upper layer, wherein the upper layer has higher carbon absorption resistance than the lower layer, and the lower layer has higher etching resistance during absorber etching. In some embodiments, the capping layer 20 comprises a RuNb-based layer (RuNb or RuNbN) disposed on a RuRh-based layer (e.g., RuRh or RuRhN).

[0033] An absorber layer 25 is disposed above the capping layer 20. The absorber layer comprises a high EUV absorbing material having a k-value (extinction coefficient) greater than about 0.03 or greater than about 0.045. In some embodiments, the absorber layer 25 is a Ta-based material. In some embodiments, the absorber layer 25 is made of at least one of TaN, TaO, TaB, TaBO, TaBN, TaRu, and TaRuN. In other embodiments, the absorber layer 25 comprises a Cr-based material, including at least one of CrN, CrBN, CrO, and CrON. In some embodiments, the absorber layer 25 has a multilayer structure of Cr, CrO, or CrON. In some embodiments, the absorber layer is an Ir or Ir-based material, including at least one of IrRu, IrPt, IrN, IrAl, IrSi, IrTi, IrRuN, and IrTaON. In some embodiments, the absorber layer is a Ru-based material, including at least one of RuPt, RuN, RuW, RuAl, RuSi, RuCr, and RuTi. In some embodiments, the absorber layer is a Pt-based material, including at least one of PtIr, PtN, PtAl, PtSi, PtTi, and PtRuN. In other embodiments, the absorber layer includes an Os-based material, including at least one of OsRu and OsRuN. In other embodiments, the absorber layer is a Rh-based material, including at least one of RhRu and RhRuN. In other embodiments, the absorber layer is an Hf-based material, including at least one of HfRu and HfRuN. In other embodiments, the absorber layer is a Pd-based material or a Re-based material. In some embodiments of this disclosure, an X-based material (where X is any element) refers to an amount of X equal to or greater than 50 atomic percent.

[0034] In other embodiments, the absorber layer material is made of A x B y The expression indicates that A and B are each one or more of Ir, Pt, Ru, Cr, Ta, Os, Pd, Al, or Re, and x:y is from about 0.25:1 to about 4:1. In some embodiments, x and y are different (smaller or larger). In some embodiments, the absorber layer further includes one or more of Si, B, or N in an amount greater than zero to about 10 atomic%. In some embodiments, the absorber layer includes about 40 atomic% to about 70 atomic% of Ru and about 2 atomic% to about 20 atomic% of N.

[0035] In some embodiments, the thickness of the absorber layer 25 ranges from about 15 nm to about 100 nm, while in other embodiments, the thickness of the absorber layer 25 ranges from about 20 nm to about 50 nm. In some embodiments, the absorber layer 25 is formed by CVD, PECVD, ALD, PVD, IBD, or any other suitable film-forming method.

[0036] In some embodiments, at least one hard mask layer is disposed over the absorber layer 25. In some embodiments, a first hard mask layer 30 is disposed over the absorber layer 28, and in some embodiments, a second hard mask layer 35 is disposed over the first hard mask layer 30, such as... FIG. 1B and FIG. 1A As shown. In some embodiments, the first hard mask layer 30 is made of at least one of TaBN, TaN, MoSi, MoSiN, SiN, SiC, and SiCN, and has a thickness of about 2 nm to about 20 nm. In some embodiments, the second hard mask layer 35 is made of at least one of TaBO, Ta2O5, TaO2, TaO, Ta2O, MoSiO, SiON, SiO2, and SiCON, and has a thickness of about 2 nm to about 20 nm. In some embodiments, the thickness of the second hard mask layer 35 is less than the thickness of the first hard mask layer 30. The first hard mask 30 is made of a material different from that of the absorber layer 25, and the second hard mask layer 35 is made of a material different from that of the first hard mask layer 30. In some embodiments, the first hard mask layer 30 and the second hard mask layer 35 are formed by CVD, PECVD, ALD, PVD, IBD, or any other suitable film formation method.

[0037] In some embodiments, at least one boundary layer is disposed over at least one hard mask layer. In some embodiments, a first boundary layer 40 is disposed over at least one hard mask layer 30, 35 and absorber layer 28, and in some embodiments, a second boundary layer 50 is disposed over the first boundary layer, such as... FIG. 1B and FIG. 1C-FIG. 1FAs shown. In some embodiments, the boundary layer is made of a material having an EUV refractive index n of about 0.87 to about 1 and an EUV extinction coefficient k greater than or equal to about 0.02. In some embodiments, the boundary layer is made of at least one material selected from the group consisting of: Rh, Pd, Ir, Pt, Co, Ni, Te, Cr, W, Hf, Ta, and alloys including PtRu, PtIr, PtRh, PtPd, PtNi, PtCo, PtTa, PtCr, PtTi, IrTa, IrCr, IrW, IrTe, IrNi, IrCo, CrN, NiCo, RhCo, RhNi, RhCr, RhW, and RhTa. In some embodiments, the boundary layer material may be doped with nitrogen, boron, oxygen, or oxynitrides. The first boundary layer 40 and the second boundary layer 50 are made of different materials. The microstructure of one or more of the first and second boundary layers may be polycrystalline with a grain size of about 1 nm to about 5 nm, or amorphous. In some embodiments, boundary layers 40 and 50 are formed by CVD, PECVD, ALD, PVD, IBD, or any other suitable film formation method. In some embodiments, the photomask preform 5a includes three or more boundary layers. In some embodiments, the thickness of the first boundary layer 40 ranges from about 10 nm to about 25 nm, and the thickness of the second boundary layer 50 ranges from about 2 nm to about 25 nm. In other embodiments, the thickness of the first boundary layer 40 ranges from about 12 nm to about 20 nm, and the thickness of the second boundary layer 50 ranges from 4 nm to about 20 nm. In some embodiments, the thickness of the first boundary layer 40 is greater than the thickness of the second boundary layer 50. In other embodiments, the thickness of the second boundary layer 50 is greater than the thickness of the first boundary layer 40.

[0038] In some embodiments, the total thickness of the layers disposed above the capping layer 20 (e.g., the absorber layer, the hard mask layer, and the boundary layer) is less than the total thickness of the reflective multilayer 15, the capping layer 20, and the absorber layer 25. In some embodiments, the total thickness of the layers disposed above the capping layer ranges from about 30 nm to about 90 nm, but this disclosure is not limited thereto.

[0039] In some embodiments, a back conductive layer 45 is disposed on a second main surface of a substrate 10, the second main surface being opposite a first main surface of the substrate 10, on which a Mo / Si reflective multilayer stack 15 is formed. In some embodiments, the back conductive layer 45 is made of TaB (tantalum boride) or other Ta-based conductive materials. In some embodiments, tantalum boride is crystalline. Crystalline tantalum boride includes TaB, Ta5B6, Ta3B4, and TaB2. In other embodiments, tantalum boride is polycrystalline or amorphous. In other embodiments, the back conductive layer 45 is made of a Cr-based conductive material (CrN or CrON). In some embodiments, the sheet resistance of the back conductive layer 45 is equal to or less than 20 Ω / □. In some embodiments, the sheet resistance of the back conductive layer 45 is equal to or greater than 0.1 Ω / □. In some embodiments, the surface roughness Ra of the back conductive layer 45 is equal to or less than 0.25 nm. In some embodiments, the surface roughness Ra of the back conductive layer 45 is equal to or greater than 0.05 nm. Additionally, in some embodiments, the flatness of the back conductive layer 45 is equal to or less than 50 nm. In some embodiments, the flatness of the back conductive layer 45 is greater than 1 nm. In some embodiments, the thickness of the back conductive layer 45 is in the range of about 50 nm to about 400 nm. In other embodiments, the thickness of the back conductive layer 45 is about 50 nm to about 100 nm. In some embodiments, the thickness is in the range of about 65 nm to about 75 nm. In some embodiments, the back conductive layer 45 is formed by atmospheric pressure CVD, low-pressure CVD, PECVD, laser-enhanced CVD, ALD, molecular beam epitaxy (MBE), physical vapor deposition (including thermal deposition), pulsed laser deposition, electron beam evaporation, ion beam assisted evaporation and sputtering, or any other suitable film formation method. When using CVD, the source gas includes TaCl5 and BCl3 in some embodiments.

[0040] Subsequently, the photomask blank 5a, including at least one boundary layer 40, 50 and at least one hard mask 30, 35, is patterned to form photomasks 100a, 100b, as shown below. FIG. 1C As shown. FIG. 1D and FIG. 1E These are cross-sectional views of photomasks 100a and 100b, and FIG. 1F and FIG. 1C-FIG. 1F These are planar views of photomasks 100a and 100b. (Example) FIG. 1E As shown, a mask pattern 80d is formed. Mask pattern 80d corresponds to the circuit pattern to be formed over the substrate patterned using masks 100a and 100b during subsequent processing. FIG. 1F and FIG. 1CAs shown, boundary layers 40 and 50 surround mask pattern 80d in a plan view. In some embodiments, at least one alignment mark 60 is formed in the outer portion of boundary layers 40 and 50. In some embodiments, alignment marks 60 are formed at the corners of photomasks 100a and 100b. FIG. 1F and FIG. 1C As shown, the boundary layers 40 and 50 surrounding the mask pattern 80d are patterned. FIG. 1C As shown, in some embodiments, the boundary pattern 85c includes alternating grooves and protrusions. According to embodiments of this disclosure, the boundary pattern 85c is not limited to... FIG. 8A-FIG. 8J The alternating grooves and protrusions shown (see FIG. 2A When the width of the protrusions or the spacing of the boundary patterns is small enough, destructive interference can be increased to reduce reflected light.

[0041] In some embodiments, the photomask blank 5b includes a buffer layer 55 located between the cover layer 20 and the absorber layer 25, such as FIG. 2B and FIG. 2A As shown. FIG. 2B An embodiment with a boundary layer 40 is shown, and FIG. 3A An embodiment with two boundary layers 40 and 50 is shown. In some embodiments, the buffer layer is made of at least one of TaBN, TaN, MoSi, MoSiN, SiN, SiC, SiCN, CrN, CrON, and RuCr, and has a thickness ranging from about 2 nm to about 20 nm. In some embodiments, the buffer layer 55 is formed by CVD, PECVD, ALD, PVD, IBD, or any other suitable film formation method.

[0042] In some embodiments, a third hard mask layer 90 is formed between the second hard mask layer 35 and the first boundary layer 40, such as FIG. 3B and FIG. 3A As shown. In the illustrated embodiment, the mask blank 5b includes a buffer layer 55 between the cover layer 20 and the absorber layer 25. In other embodiments, a third hard mask layer 90 is formed over the mask blank 5a, which does not include the buffer layer. FIG. 3B An embodiment with a boundary layer 40 is shown, and FIG. 4AAn embodiment with two boundary layers 40, 50 is shown. In some embodiments, the third hard mask layer 90 is made of at least one of GaN, CrON, CrCON, SiO, SiCO, Y2O3, SiCO, and SiCON, and has a thickness of about 2 nm to about 20 nm. In some embodiments, the third mask layer 90 is made of a material different from the second hard mask layer 35 and the first boundary layer. In some embodiments, the third hard mask layer 90 is formed by CVD, PECVD, ALD, PVD, IBD, or any other suitable film formation method.

[0043] In some embodiments, a fourth hard mask layer 95 is formed between the absorber layer 25 and the first hard mask layer 30, such as FIG. 4B and FIG. 4A As shown. In the illustrated embodiment, the mask blank 5b includes a buffer layer 55 between the cover layer 20 and the absorber layer 25. In other embodiments, a fourth hard mask layer 90 is formed over the mask blank 5a, which does not include the buffer layer. FIG. 4B An embodiment with a boundary layer 40 is shown, and FIG. 5A-FIG. 5N An embodiment with two boundary layers 40, 50 is shown. In some embodiments, the fourth hard mask layer 95 is made of at least one of CrN, CrON, or RuCr, and has a thickness of about 2 nm to about 20 nm. In some embodiments, the fourth mask layer 95 is made of a material different from the first hard mask layer 30 and the absorber layer 25. In some embodiments, the fourth hard mask layer 95 is formed by CVD, PECVD, ALD, PVD, IBD, or any other suitable film formation method.

[0044] FIG. 5A-FIG. 5N A method for manufacturing a photomask according to an embodiment of the present disclosure is illustrated schematically. The materials, configurations, processes, and / or dimensions described with respect to the foregoing embodiments may be used in the following embodiments, and detailed descriptions thereof may be omitted. FIG. 5A-FIG. 5N In the illustrated embodiment, the photomask includes two boundary layers 40, 50 and three hard mask layers 30, 35, 90, while in other embodiments, the photomask includes one or more boundary layers and one or more hard mask layers. Although in FIG. 5A-FIG. 5N The buffer layer is not shown in this embodiment, but in other embodiments, FIG. 5A The operation shown in the middle diagram is performed on a photomask blank that includes a buffer layer.

[0045] According to any of the embodiments disclosed herein, a photomask blank is provided having at least one hard mask layer 30, 35 and at least one boundary layer 40, 50 disposed thereon, such as FIG. 5BAs shown. In one embodiment, the photomask blank includes an absorber layer 25 made of CrN, a first hard mask layer 30 made of TaBN, a second hard mask layer 35 made of TaBON, a third hard mask layer 90 made of CrON, a first boundary layer 40 made of Pt, and a second boundary layer 50 made of CrN disposed thereon, but the structure is not limited to these materials. In some embodiments, alignment marks 60 are formed in the peripheral regions of the boundary layers 40, 50, such as FIG. 5B As shown. Alignment marks 60 are configured to align the photomask in subsequent processing operations. In some embodiments, alignment marks 60 are formed using appropriate photolithography and etching operations. Alignment marks may be formed around the outer periphery of the structure, or may be formed on one or more sides of the structure. In some embodiments, alignment marks 60 are formed in the first and second boundary layers 40, 50, exposing a portion of the third hard mask layer 90.

[0046] exist FIG. 5C A first photoresist layer 65 is formed over the structure, and then the photoresist layer 65 is selectively exposed to photochemical radiation and developed to form an opening 70a that exposes a portion of the second boundary layer 50, such as... FIG. 5D As shown. In some embodiments, the photoresist layer 65 undergoes exposure-to-baking before the development operation. The exposed portion of the second boundary layer corresponds to the mask pattern region in the subsequently formed mask. In some embodiments, the photoresist layer 65 is made of a chemically amplified resist or a metal-organic resist, and the photochemical radiation is deep ultraviolet radiation, extreme ultraviolet radiation, or an electron beam.

[0047] Using the remaining photoresist layer 65 as a mask, the second boundary layer is removed through a suitable etching operation, thereby exposing the first boundary layer 40 through the extended opening 70b, as shown. FIG. 5E As shown. Then, the first photoresist layer is removed by a suitable photoresist removal operation, such as photoresist stripping or plasma ashing, as... FIG. 5F As shown.

[0048] exist FIG. 5F Then, through appropriate etching operations, the first boundary layer 40 exposed in the opening 70b is removed, thereby exposing a portion of the third hard mask layer 90 through the extended opening 70c. Subsequently in FIG. 5G A second photoresist layer 75 is formed above the structure, such as... FIG. 5H As shown. The second photoresist layer 75 can be formed of the same material as the first photoresist layer 65, or it can be formed of a different suitable photoresist.

[0049] Subsequently, the second photoresist layer 75 is selectively exposed to photochemical radiation and developed to form a second pattern 80a, thereby exposing a portion of the uppermost hard mask layer. In some embodiments, the second photoresist layer 75 undergoes post-exposure baking before the development operation. In this embodiment, some portions of the third hard mask layer 90 are exposed by the second pattern 80a, such as... FIG. 5I As shown.

[0050] Using the second pattern 80a as a mask, the third hard mask layer 90 is etched using a suitable etchant to form the pattern 80b in the third hard mask layer 90, as shown. FIG. 5J As shown. In some embodiments, the etching operation is a dry etching operation. In some embodiments, the etching is anisotropic etching. The pattern 80b in the third hard mask layer 90 is an extension of the second pattern 80a in the second photoresist layer 75. The remaining photoresist layer is then removed by a suitable photoresist removal operation, such as photoresist stripping or plasma ashing, as shown. FIG. 5K As shown.

[0051] Then, using a suitable etchant selectively applied to the second hard mask layer 35 and the first hard mask layer 30, the pattern 80b in the third hard mask layer 90 is extended into the second and third hard mask layers 35 and 30, forming a pattern 80c in the second and first hard mask layers 35 and 30, as shown. FIG. 5L As shown. In some embodiments, the etching operation is dry anisotropic etching. Then, the remaining portion of the third hard mask layer in the opening 70c is removed using a suitable etchant that is selective for the third hard mask layer, as... FIG. 5M As shown. In some embodiments, a portion of the second boundary layer 50 is removed when etching the third hard mask layer 90.

[0052] Using a suitable etchant that is selective for the absorber layer 25, a pattern 80d is formed in the absorber layer 25, such as... FIG. 5N As shown. The pattern 80d in the absorber layer 25 corresponds to the pattern 80c formed in the first and second hard mask layers 30, 35. By removing the remaining portions of the first and second hard mask layers 30, 35 in the opening 70c, in FIG. 6A-FIG. 6N A patterned photomask 100a is formed. Boundary layers 40 and 50 extend above and around the absorber layer pattern 80d. The first and second hard mask layers 30 and 35 are removed using a suitable etchant that is selective to the first and second hard mask layers 30 and 35. In some embodiments, the etchant is a dry anisotropic etchant.

[0053] FIG. 6A-FIG. 6NA method for manufacturing a photomask according to an embodiment of the present disclosure is illustrated schematically. The materials, configurations, processes, and / or dimensions described with respect to the foregoing embodiments may be used in the following embodiments, and detailed descriptions thereof may be omitted. FIG. 6A-FIG. 6N In the illustrated embodiment, the photomask includes two boundary layers 40, 50 and three hard mask layers 30, 35, 90, while in other embodiments, the photomask includes one or more boundary layers and one or more hard mask layers. Although in FIG. 6A-FIG. 6N The buffer layer is not shown in this embodiment, but in other embodiments, FIG. 6A The operation shown in the middle diagram is performed on a photomask blank that includes a buffer layer.

[0054] According to any of the embodiments disclosed herein, a photomask blank is provided having at least one hard mask layer 30, 35 and at least one boundary layer 40, 50 disposed thereon, such as FIG. 6B As shown. In one embodiment, the photomask blank includes an absorber layer 25 made of CrN, a first hard mask layer 30 made of TaBN, a second hard mask layer 35 made of TaBON, a third hard mask layer 90 made of CrON, a first boundary layer 40 made of Pt, and a second boundary layer 50 made of CrN disposed thereon, but the structure is not limited to these materials. In some embodiments, alignment marks 60 are formed in the peripheral regions of the boundary layers 40, 50, such as FIG. 6B As shown. Alignment marks 60 are configured to align the photomask in subsequent processing operations. In some embodiments, alignment marks 60 are formed using appropriate photolithography and etching operations. Alignment marks may be formed around the outer periphery of the structure, or may be formed on one or more sides of the structure. In some embodiments, alignment marks 60 are formed in the first and second boundary layers 40, 50, exposing a portion of the third hard mask layer 90.

[0055] exist FIG. 6C A first photoresist layer 65 is formed over the structure, and then the photoresist layer 65 is selectively exposed to photochemical radiation and developed to form an opening 70a exposing a portion of the second boundary layer 50, and a pattern 85a including a plurality of alternating protrusions and depressions surrounding the opening 70a, such as... FIG. 6D As shown. In some embodiments, the photoresist layer 65 undergoes post-exposure baking before the development operation. In some embodiments, the photoresist layer 65 is made of a chemically amplified resist or a metal-organic resist, and the photochemical radiation is deep ultraviolet radiation, extreme ultraviolet radiation, or an electron beam.

[0056] Using photoresist layer 65 as a mask, a portion of the second boundary layer is removed through appropriate etching operations, thereby exposing the first boundary layer 40 through the extended opening 70b and photoresist pattern 85a. FIG. 6EAs shown. Then, the first photoresist layer is removed by a suitable photoresist removal operation, such as photoresist stripping or plasma ashing, as... FIG. 6F As shown.

[0057] exist FIG. 6F In the middle, the exposed portion of the first boundary layer is then removed by appropriate etching operations, thereby exposing a portion of the third hard mask layer through the extended opening 70c and the extended photoresist pattern 85b. Subsequently in FIG. 5G A second photoresist layer 75 is formed above the structure, such as... FIG. 6H As shown. The second photoresist layer 75 can be formed of the same material as the first photoresist layer 65, or it can be formed of a different suitable photoresist.

[0058] Subsequently, the second photoresist layer 75 is selectively exposed to photochemical radiation and developed to form a second pattern 80a, thereby exposing a portion of the uppermost hard mask layer. In some embodiments, the second photoresist layer 75 undergoes post-exposure baking before the development operation. In this embodiment, some portions of the third hard mask layer 90 are exposed by the second pattern 80a, such as... FIG. 6I As shown.

[0059] Using the second pattern 80a as a mask, the third hard mask layer 90 is etched using a suitable etchant to form the pattern 80b in the third hard mask layer 90, as shown. FIG. 6J As shown. In some embodiments, the etching operation is a dry etching operation. In some embodiments, the etching is anisotropic etching. The pattern 80b in the third hard mask layer 90 is an extension of the second pattern 80a in the second photoresist layer 75. The remaining photoresist layer is then removed by a suitable photoresist removal operation, such as photoresist stripping or plasma ashing, as shown. FIG. 6K As shown.

[0060] Then, using a suitable etchant selectively applied to the second hard mask layer 35 and the first hard mask layer 30, the third pattern 80b in the third hard mask layer 90 is extended into the second and third hard mask layers 35 and 30, forming a pattern 80c in the second and first hard mask layers 35 and 30, as shown. FIG. 6L As shown. In some embodiments, the etching operation is dry anisotropic etching. Then, the remaining portion of the third hard mask layer in the opening 70c is removed using a suitable etchant that is selective for the third hard mask layer, as... FIG. 6M As shown. In some embodiments, a portion of the second boundary layer 50 is removed when etching the third hard mask layer 90.

[0061] Using a suitable etchant that is selective for the absorber layer 25, a pattern 80d is formed in the absorber layer 25, such as... FIG. 6NAs shown. The pattern 80d in the absorber layer 25 corresponds to the pattern 80c formed in the first and second hard mask layers 30, 35. By removing the remaining portions of the first and second hard mask layers 30, 35 in the opening 70c, in FIG. 7 A patterned photomask 100b is formed. Patterned boundary layers 40, 50 extend above and around the absorber layer pattern 80d. The first and second hard mask layers 30, 35 are removed using a suitable etchant that is selective to the first and second hard mask layers 30, 35. In some embodiments, the etchant is a dry anisotropic etchant.

[0062] FIG. 6A-FIG. 6N The illustration is based on the references in this article. FIG. 8A The disclosed embodiments fabricate a photomask 100b. In some embodiments, when the width W of the boundary layer pattern 85c features or the spacing P of the boundary pattern 85c is sufficiently small, destructive interference is increased, thereby reducing the amount of reflected light. In some embodiments, the width of the boundary layer protrusions in the boundary layer pattern 85c is equal to or less than about 25 nm. In some embodiments, the spacing of the boundary layer pattern 85c features is equal to or less than about 50 nm.

[0063] In some embodiments, the boundary pattern 85c is a pattern different from alternating grooves and protrusions. For example, in some embodiments, the boundary pattern 85c is composed of checkerboard-shaped holes 85d with a width of about 5 nm to about 39 nm and a spacing of about 10 nm to about 40 nm, such as... FIG. 8B As shown. In other embodiments, the boundary pattern consists of a series of staggered holes 85d, as... FIG. 8C As shown. The width of the aperture 85d can be from about 5 nm to about 40 nm. In some embodiments, the direction of the boundary pattern 85c of the protrusions and trenches is at an angle to the boundary of the photomask or the main pattern, such as... FIG. 8D As shown. In other embodiments, the boundary pattern 85c of the protrusions and grooves is curved, as shown. FIG. 8E As shown. In some embodiments, the boundary pattern 85c is composed of polygonal holes 85d, which can be arranged regularly, such as... FIG. 8F As shown, or they may be staggered. In some embodiments, the spacing of the boundary patterns 85c is not fixed and can vary between adjacent protrusions, such as... FIG. 8G As shown. In other embodiments, the widths of the protrusions and grooves of the boundary pattern 85c are not fixed and can vary between adjacent protrusions and grooves, such as... FIG. 8H As shown. The boundary pattern 85c can be composed of combinations of different patterns, such as... FIG. 8I As shown. In some embodiments, the boundary pattern 85c overlaps with or is attached to the main pattern 80d, as shown respectively. FIG. 9 and 8JAs shown. A boundary pattern overlapping with or attached to the main pattern 80d may include a series or array of sub-resolution assist features (SRAFs) 85e. The boundary pattern designs covered by this disclosure are not limited to the disclosed embodiments. When the width or spacing of the protrusions or holes in the boundary pattern is sufficiently small, destructive interference can be increased to reduce reflected light.

[0064] FIG. 10 A flowchart of a method 900 for manufacturing a photomask according to an embodiment of the present disclosure is shown. The materials, configurations, processes, and / or dimensions described with respect to the foregoing embodiments may be employed in the following embodiments, and detailed descriptions thereof may be omitted. Method 900 includes an operation S905 of forming boundary layers 40, 50 over a photomask blank 5a. The photomask blank 5a includes a substrate 10, a reflective multilayer 15 disposed over the substrate 10, and an absorber layer 25 disposed over the reflective multilayer 15. In operation S910, a portion of the boundary layers 40, 50 is removed to form a recess 70a surrounded by the boundary layers 40, 50, and in operation S915, a portion of the absorber layer 25 is selectively removed from the recess to form a pattern 80d in the absorber layer 25. In some embodiments, the refractive index of the boundary layers 40, 50 ranges from about 0.87 to about 1, and the extinction coefficient is greater than or equal to about 0.02. In some embodiments, the extinction coefficient of the boundary layers 40, 50 ranges from 0.02 to 0.1. In some embodiments, method 900 includes an operation S920 of forming hard mask layers 30, 35, 90 over a photomask blank 5a, and then forming boundary layers 40, 50 over the photomask blank. In one embodiment, forming the boundary layers includes an operation S925 of forming a first boundary layer 40 over the hard mask layers 30, 35, 90 and forming a second boundary layer 50 over the first boundary layer 40, wherein the first boundary layer and the second boundary layer are made of different materials. In some embodiments, forming the hard mask layers further includes an operation S930 of forming a first hard mask layer 30 over a photomask blank 5b and forming a second hard mask layer 35 over the first hard mask layer 30, wherein the first hard mask layer 30 and the second hard mask layer 35 are made of different materials. In one embodiment, method 900 includes an operation of forming a third hard mask layer 90 over the second hard mask layer 35, wherein the third hard mask layer is made of a different material than the second hard mask layer.

[0065] FIG. 11A flowchart 1000 of a method for manufacturing a photomask 100b according to an embodiment of the present disclosure is shown. The materials, configurations, processes, and / or dimensions described with respect to the foregoing embodiments may be employed in the following embodiments, and detailed descriptions thereof may be omitted. Method 1000 includes operation S1005 of forming boundary layers 40, 50 over a photomask blank 5a. The photomask blank 5a includes a substrate 10, a reflective multilayer 15 disposed over the substrate, and an absorber layer 25 disposed over the reflective multilayer. In operation S1010, a pattern 85c is formed in a peripheral region of the boundary layers 40, 50, and an opening 70c is formed in a second region of the boundary layers surrounded by the peripheral regions, wherein the pattern in the boundary layers includes at least two spaced-apart trenches and two spaced-apart protrusions on each side of the boundary layers in a cross-sectional view. In operation S1015, portions of the absorber layer in the openings are selectively removed to form a pattern in the absorber layer. Boundary layers 40 and 50 comprise at least one selected from the group consisting of: Rh, Pd, Ir, Pt, Co, Ni, Te, Cr, W, Hf, Ta, PtRu, PtIr, PtRh, PtPd, PtNi, PtCo, PtTa, PtCr, PtTi, IrTa, IrCr, IrW, IrTe, IrNi, IrCo, CrN, NiCo, RhCo, RhNi, RhCr, RhW, and RhTa. In some embodiments, boundary layers 40 and 50 are doped with at least one of nitrogen, boron, oxygen, or oxynitrides. In some embodiments, the method includes forming hard mask layers 30, 35, and 90 over absorber layer 25 prior to forming boundary layers 40 and 50.

[0066] FIG. 12A A flowchart of a method 1100 for manufacturing a semiconductor device according to some embodiments of the present disclosure is shown. The materials, configurations, processes, and / or dimensions described with respect to the foregoing embodiments may be employed in the following embodiments, and detailed descriptions thereof may be omitted. The method 1100 for manufacturing a semiconductor device includes operation S1110, which selectively exposes a photoresist layer PR to photochemical radiation reflected from reflective masks (100a, 100b) to form a latent pattern in the photoresist layer PR. The reflective masks 100a, 100b may be any masks disclosed herein, including a substrate 10, a reflective multilayer 15 disposed over the substrate, an absorber layer 25 disposed over the reflective multilayer (including a pattern 80d in the absorber layer), and boundary layers 40, 50 surrounding the pattern in the absorber layer in a plan view. The refractive index of the boundary layers ranges from 0.87 to 1, and the extinction coefficient is greater than or equal to 0.02. In operation S1120, the selectively exposed photoresist layer is developed to form a pattern in the photoresist layer.

[0067] FIG. 12BA flowchart illustrating a method for manufacturing semiconductor devices is provided, and FIG. 12C , FIG. 12D , FIG. 12E and FIG. 12A The sequential manufacturing operations of a method for fabricating a semiconductor device according to embodiments of the present disclosure are illustrated. The materials, configurations, processes, and / or dimensions described with respect to the foregoing embodiments may be employed in the following embodiments, and detailed descriptions thereof may be omitted.

[0068] A semiconductor substrate or other suitable substrate is provided to be patterned for forming an integrated circuit thereon. In some embodiments, the semiconductor substrate comprises silicon. Alternatively or additionally, the semiconductor substrate comprises germanium, silicon-germanium, or other suitable semiconductor materials, such as group III-V semiconductor materials. FIG. 12B In operation S1210, a target layer to be patterned is formed over a semiconductor substrate. In some embodiments, the target layer is a semiconductor substrate. In some embodiments, the target layer includes a conductive layer, such as a metal layer or a polysilicon layer; a dielectric layer, such as silicon oxide, silicon nitride, SiON, SiOC, SiOCN, SiCN, hafnium oxide, or aluminum oxide; or a semiconductor layer, such as an epitaxially formed semiconductor layer. In some embodiments, the target layer is formed over an underlying structure (e.g., an isolation structure, a transistor, or wiring). In operation S1220, a photoresist layer PR is formed over the target layer TL, such as... FIG. 12C As shown. During the subsequent photolithography exposure process, the photoresist layer PR is sensitive to radiation from the exposure source. In this embodiment, the photoresist layer PR is sensitive to EUV light used in the photolithography exposure process. The photoresist layer PR can be formed over the target layer by spin coating or other suitable techniques. The coated photoresist layer can be further baked to remove solvent from the photoresist layer. In operation S1230, the photoresist layer is patterned using EUV reflective masks 100a, 100b as described in any embodiment herein, such as FIG. 12DAs shown. Patterning of the photoresist layer includes performing a photolithographic exposure process using EUV reflective masks 100a and 100b through an EUV exposure system. During the exposure process, an integrated circuit (IC) design pattern defined on the EUV reflective masks 100a and 100b is imaged onto the photoresist layer PR to form a latent pattern thereon. Patterning of the photoresist layer PR also includes developing the exposed photoresist layer to form a patterned photoresist layer with one or more openings. In one embodiment where the photoresist layer is a positive-toned photoresist layer, the exposed portions of the photoresist layer PR are removed during the development process. In another embodiment where the photoresist layer PR is a negative-toned photoresist, the unexposed portions of the photoresist layer PR are removed during development. Patterning of the photoresist layer may also include other process steps, such as various baking steps at different stages. For example, a post-exposure-baking (PEB) process may be performed after the photolithographic exposure process and before the development process.

[0069] In operation S1240, a patterned photoresist layer is used as an etching mask to pattern the target layer, such as... FIG. 12E As shown. In some embodiments, patterning the target layer includes applying an etching process to the target layer using a patterned photoresist layer as an etching mask. The portion of the target layer exposed within the openings of the patterned photoresist layer is etched, while the remainder remains un-etched. Alternatively, the patterned photoresist layer can be removed by wet stripping or plasma ashing, such as... ​ As shown.

[0070] Embodiments of this disclosure provide techniques for preventing or suppressing proximity die effects, thereby improving semiconductor device yield. In some embodiments, according to embodiments of this disclosure, a boundary layer surrounding a mask patterned region effectively mitigates proximity die effects, much like a black boundary, without the problems encountered when forming a black boundary, such as flatness variations and defects, the use of multiple exposed masks, and two-layer splicing issues. The boundary layer mitigates EUV radiation reflection from the unpatterned region (boundary region or peripheral region) of the EUV mask to the patterned substrate. In some embodiments including a patterned boundary layer, when the width W of the boundary layer pattern feature or the spacing of the boundary pattern 85c is sufficiently small, destructive interference is increased, thereby reducing the amount of reflected light.

[0071] In some embodiments, a 16.5 nm thick PtRu boundary layer 40 is disposed over a third hard mask layer 90 made of CrON, a second hard mask layer 35 made of TaBO, and a first hard mask layer 30 made of TaBN. In another embodiment, the 16.5 nm thick PtRu boundary layer 40 is disposed over the third hard mask layer 90 made of CrON, the second hard mask layer 35 made of TaBO, and the first hard mask layer 30 made of TaBN, and the PtRu boundary layer 40 is patterned to have a spacing of 22 nm.

[0072] In other embodiments, the first boundary layer 40 and the second boundary layer 50 have different thicknesses. In these embodiments, the CrN first boundary layer 40 and the second TaBN boundary layer 50 are disposed over the TaBN first hard mask layer 30, the TaBN second hard mask layer 35, and the CrON third hard mask layer 90. In one embodiment, the thickness of the first boundary layer 40 is approximately 18 nm, and the thickness of the second boundary layer 50 is approximately 19 nm. In another embodiment, the thickness of the first boundary layer 40 is approximately 19 nm, and the thickness of the second boundary layer 50 is approximately 18 nm. In another embodiment, the thickness of the first boundary layer 40 is approximately 17 nm, and the thickness of the second boundary layer 50 is approximately 20 nm. In yet another embodiment, the thickness of the first boundary layer 40 is approximately 17 nm, and the thickness of the second boundary layer 50 is approximately 13 nm.

[0073] In another embodiment, the first boundary layer 40 is made of Pt and has a thickness of approximately 20 nm, and the second boundary layer 50 is made of TaBN and has a thickness of approximately 4 nm. In another embodiment, the first boundary layer 40 is made of Pt and has a thickness of approximately 13 nm, and the second boundary layer is made of TaBN and has a thickness of approximately 11 nm. In yet another embodiment, the first boundary layer 40 is made of Pt and has a thickness of approximately 12 nm, and the second boundary layer 50 is made of TaBN and has a thickness of approximately 19 nm.

[0074] In another embodiment, the first boundary layer 40 is made of CrN and has a thickness of approximately 4 nm, and the second boundary layer 50 is made of Pt and has a thickness of approximately 20 nm. In another embodiment, the first boundary layer 40 is made of TaBN and has a thickness of approximately 19 nm, and the second boundary layer 50 is made of CrN and has a thickness of approximately 18 nm. In yet another embodiment, the first boundary layer 40 is made of CrN and has a thickness of approximately 11 nm, and the second boundary layer 50 is made of PtRu and has a thickness of approximately 20 nm.

[0075] It should be understood that this document does not necessarily discuss all advantages, and not all embodiments or examples claim a particular advantage; other embodiments or examples may offer different advantages.

[0076] According to one embodiment of this disclosure, a method of manufacturing a photomask includes forming a boundary layer over a photomask blank. The photomask blank includes: a substrate, a reflective multilayer disposed over the substrate, and an absorber layer disposed over the reflective multilayer. A portion of the boundary layer is removed to form a recess surrounded by the boundary layer, and a portion of the absorber layer is selectively removed within the recess to form a pattern in the absorber layer. The refractive index of the boundary layer ranges from 0.87 to 1, and the extinction coefficient is greater than or equal to 0.02. In one embodiment, the extinction coefficient of the boundary layer ranges from 0.02 to 0.1. In one embodiment, the method includes forming a hard mask layer over the photomask blank before forming the boundary layer over the photomask blank. In one embodiment, a portion of the hard mask layer is exposed during the removal of a portion of the boundary layer. In one embodiment, forming the boundary layer includes: forming a first boundary layer over the hard mask layer, and forming a second boundary layer over the first boundary layer, wherein the first boundary layer and the second boundary layer are made of different materials. In one embodiment, forming the hard mask layer further includes: forming a first hard mask layer over a photomask blank, and forming a second hard mask layer over the first hard mask layer, wherein the first hard mask layer and the second hard mask layer are made of different materials. In one embodiment, the method includes forming a third hard mask layer over the second hard mask layer, wherein the third hard mask layer is made of a different material than the second hard mask layer. In one embodiment, the photomask blank includes a capping layer disposed between a reflective multilayer and an absorber layer. In one embodiment, portions of the capping layer are exposed during selective removal of portions of the absorber layer.

[0077] In another embodiment of this disclosure, a method of manufacturing a photomask includes forming a boundary layer over a photomask blank. The photomask blank includes: a substrate, a reflective multilayer disposed over the substrate, and an absorber layer disposed over the reflective multilayer. A pattern is formed in a peripheral region of the boundary layer, and an opening is formed in a second region of the boundary layer surrounded by the peripheral region, wherein the pattern in the boundary layer includes at least two spaced-apart trenches and two spaced-apart protrusions on each side of the boundary layer in a cross-sectional view. A portion of the absorber layer in the opening is selectively removed to form the pattern in the absorber layer. The boundary layer comprises at least one selected from the group consisting of: Rh, Pd, Ir, Pt, Co, Ni, Te, Cr, W, Hf, Ta, PtRu, PtIr, PtRh, PtPd, PtNi, PtCo, PtTa, PtCr, PtTi, IrTa, IrCr, IrW, IrTe, IrNi, IrCo, CrN, NiCo, RhCo, RhNi, RhCr, RhW, and RhTa. In one embodiment, the boundary layer is doped with at least one of: nitrogen, boron, oxygen, or oxynitride. In one embodiment, the absorber layer comprises at least one of the following: PtRu, IrRu, OsRu, HfRu, RhRu, TaRu, PtRuN, IrRuN, OsRuN, HfRuN, RhRuN, RuCr, IrTaON, CrN, TaBN, TaN, RuW, RuN, and TaRuN. In one embodiment, the method includes forming a hard mask layer over the absorber layer prior to forming a boundary layer. In one embodiment, a pattern in the boundary layer exposes the hard mask layer. In one embodiment, the protrusions in the pattern in the boundary layer have a width of less than or equal to 25 nm in a cross-sectional view.

[0078] In another embodiment of this disclosure, a method of manufacturing a semiconductor device includes selectively exposing a photoresist layer to photochemical radiation reflected from a reflective mask to form a latent pattern in the photoresist layer. The reflective mask includes: a substrate; a reflective multilayer disposed over the substrate; an absorber layer disposed over the reflective multilayer, including a pattern in the absorber layer; and a boundary layer surrounding the pattern in the absorber layer in a plan view. The boundary layer has a refractive index ranging from 0.87 to 1 and an extinction coefficient greater than or equal to 0.02. The selectively exposed photoresist layer is developed to form a pattern in the photoresist layer. In one embodiment, the photochemical radiation is extreme ultraviolet radiation. In one embodiment, the boundary layer includes a pattern having at least two spaced-apart trenches and two spaced-apart protrusions on each side of the boundary layer in a cross-sectional view. In one embodiment, the boundary layer comprises at least one selected from the group consisting of: Rh, Pd, Ir, Pt, Co, Ni, Te, Cr, W, Hf, Ta, PtRu, PtIr, PtRh, PtPd, PtNi, PtCo, PtTa, PtCr, PtTi, IrTa, IrCr, IrW, IrTe, IrNi, IrCo, CrN, NiCo, RhCo, RhNi, RhCr, RhW, and RhTa. In one embodiment, the boundary layer comprises at least a first boundary layer disposed above the absorber layer and a second boundary layer disposed above the first boundary layer, formed of a material different from the first boundary layer.

[0079] In another embodiment of this disclosure, a photomask includes a substrate and a reflective multilayer disposed above the substrate. An absorber layer is disposed above the reflective multilayer, including a pattern in the absorber layer, and a boundary layer surrounds the pattern in the absorber layer in a plan view. The refractive index of the boundary layer ranges from 0.87 to 1, and the extinction coefficient is greater than or equal to 0.02. In one embodiment, the extinction coefficient of the boundary layer ranges from 0.02 to 0.1. In one embodiment, the position of the uppermost surface of the boundary layer is at a greater distance from the uppermost surface of the substrate than the uppermost surface of the absorber layer. In one embodiment, the photomask includes a hard mask layer disposed between the absorber layer and the boundary layer. In one embodiment, the boundary layer includes a first boundary layer disposed above the hard mask layer and a second boundary layer disposed above the first boundary layer, wherein the first boundary layer and the second boundary layer are made of different materials. In one embodiment, the hard mask layer includes a first hard mask layer disposed above the absorber layer and a second hard mask layer disposed above the first hard mask layer, wherein the first hard mask layer and the second hard mask layer are made of different materials. In one embodiment, the photomask includes a third hard mask layer disposed above the second hard mask layer, wherein the third hard mask layer is made of a different material than the second hard mask layer. In one embodiment, the photomask includes a capping layer disposed between a reflective multilayer and an absorber layer, wherein the capping layer is made of a different material than the reflective multilayer and the absorber layer. In one embodiment, the photomask includes a buffer layer disposed between a substrate and a reflective multilayer, wherein the buffer layer is made of a different material than the substrate and the reflective multilayer.

[0080] In another embodiment of this disclosure, a photomask includes a substrate and a reflective multilayer disposed over the substrate. A patterned absorber layer including a first pattern is disposed over the reflective multilayer, and a patterned boundary layer having a second pattern surrounds the first pattern in a plan view. The second pattern includes a pattern of at least two spaced-apart trenches and two spaced-apart protrusions on each side of the boundary layer in a cross-sectional view. The width of the protrusions in the pattern in the boundary layer in a cross-sectional view is less than or equal to 25 nm. In one embodiment, the position of the uppermost surface of the boundary layer is greater than the distance from the uppermost surface of the substrate than the uppermost surface of the absorber layer. In one embodiment, the photomask includes a hard mask layer disposed between the absorber layer and the boundary layer, wherein the hard mask layer is made of a different material than the absorber layer and the boundary layer. In one embodiment, the second pattern exposes the hard mask layer. In one embodiment, the hard mask layer includes a first hard mask layer disposed over the absorber layer and a second hard mask layer disposed over the first hard mask layer, wherein the first hard mask layer and the second hard mask layer are made of different materials. In one embodiment, the boundary layer includes a first boundary layer disposed over the hard mask layer and a second boundary layer disposed over the first boundary layer, wherein the first boundary layer and the second boundary layer are made of different materials.

[0081] In another embodiment of this disclosure, a photomask includes a substrate and a reflective multilayer disposed over the substrate. A patterned absorber layer including a first pattern is disposed over the reflective multilayer, and a boundary layer surrounds the first pattern in a plan view. The boundary layer includes at least one selected from the group consisting of: Rh, Pd, Ir, Pt, Co, Ni, Te, Cr, W, Hf, Ta, PtRu, PtIr, PtRh, PtPd, PtNi, PtCo, PtTa, PtCr, PtTi, IrTa, IrCr, IrW, IrTe, IrNi, IrCo, CrN, NiCo, RhCo, RhNi, RhCr, RhW, and RhTa. The absorber layer includes at least one of the following: PtRu, IrRu, OsRu, HfRu, RhRu, TaRu, PtRuN, IrRuN, OsRuN, HfRuN, RhRuN, RuCr, IrTaON, CrN, TaBN, TaN, RuW, RuN, and TaRuN. In one embodiment, the photomask includes a hard mask layer disposed between the absorber layer and the boundary layer, wherein the hard mask layer is made of a different material than the absorber layer and the boundary layer. In one embodiment, the hard mask layer includes a first hard mask layer disposed over the absorber layer and a second hard mask layer disposed over the first hard mask layer, wherein the first hard mask layer and the second hard mask layer are made of different materials. In one embodiment, the boundary layer includes a first boundary layer disposed over the hard mask layer and a second boundary layer disposed over the first boundary layer, wherein the first boundary layer and the second boundary layer are made of different materials. In one embodiment, the photomask includes a cover layer disposed between a reflective multilayer and an absorber layer, wherein the cover layer is made of a different material from the reflective multilayer and the absorber layer.

[0082] The foregoing outlines the features of several embodiments or examples to enable those skilled in the art to better understand various aspects of this disclosure. Those skilled in the art will understand that they can readily use this disclosure as the basis for designing or modifying other processes and structures to achieve the same purpose and / or realize the same advantages of the embodiments or examples described herein. Those skilled in the art will also recognize that such equivalent constructions do not depart from the spirit and scope of this disclosure, and that various changes, substitutions, and alterations can be made to this document without departing from the spirit and scope of this disclosure.

[0083] Example 1 is a method of manufacturing a photomask, comprising: forming a boundary layer over a photomask blank, wherein the photomask blank comprises: a substrate; a reflective multilayer disposed over the substrate; and an absorber layer disposed over the reflective multilayer; removing a portion of the boundary layer to form a recess surrounded by the boundary layer; and selectively removing a portion of the absorber layer in the recess to form a pattern in the absorber layer, wherein the refractive index of the boundary layer is in the range of 0.87 to 1, and the extinction coefficient is greater than or equal to 0.02.

[0084] Example 2. The method according to claim 1, wherein the extinction coefficient of the boundary layer ranges from 0.02 to 0.1.

[0085] Example 3. The method of claim 1 further comprises: forming a hard mask layer over the photomask blank before forming the boundary layer over the photomask blank.

[0086] Example 4. The method of claim 3, wherein a portion of the hard mask layer is exposed during the removal of a portion of the boundary layer.

[0087] Example 5. The method of claim 3, wherein forming the boundary layer further comprises: forming a first boundary layer over the hard mask layer; and forming a second boundary layer over the first boundary layer, wherein the first boundary layer and the second boundary layer are made of different materials.

[0088] Example 6. The method of claim 3, wherein forming the hard mask layer further comprises: forming a first hard mask layer over the photomask blank; and forming a second hard mask layer over the first hard mask layer, wherein the first hard mask layer and the second hard mask layer are made of different materials.

[0089] Example 7. The method of claim 6 further comprises: forming a third hard mask layer over the second hard mask layer, wherein the third hard mask layer is made of a different material than the second hard mask layer.

[0090] Example 8. The method of claim 1, wherein the photomask blank includes a cover layer disposed between the reflective multilayer and the absorber layer.

[0091] Example 9. The method of claim 8, wherein, during the selective removal of portions of the absorber layer, portions of the cover layer are exposed.

[0092] Example 10 is a method of manufacturing a photomask, comprising: forming a boundary layer over a photomask blank, wherein the photomask blank comprises: a substrate; a reflective multilayer disposed over the substrate; and an absorber layer disposed over the reflective multilayer; forming a pattern in a peripheral region of the boundary layer and forming an opening in a second region of the boundary layer surrounded by the peripheral region, wherein the pattern in the boundary layer comprises at least two spaced-apart trenches and two spaced-apart protrusions on each side of the boundary layer in a cross-sectional view; and selectively removing [something] in the opening. Some portions of the absorber layer are patterned in the absorber layer, wherein the boundary layer comprises at least one selected from the group consisting of: Rh, Pd, Ir, Pt, Co, Ni, Te, Cr, W, Hf, Ta, PtRu, PtIr, PtRh, PtPd, PtNi, PtCo, PtTa, PtCr, PtTi, IrTa, IrCr, IrW, IrTe, IrNi, IrCo, CrN, NiCo, RhCo, RhNi, RhCr, RhW, and RhTa.

[0093] Example 11. The method of claim 10, wherein the boundary layer is doped with at least one of the following: nitrogen, boron, oxygen, or oxynitride.

[0094] Example 12. The method of claim 10, wherein the absorber layer comprises at least one of the following: PtRu, IrRu, OsRu, HfRu, RhRu, TaRu, PtRuN, IrRuN, OsRuN, HfRuN, RhRuN, RuCr, IrTaON, CrN, TaBN, TaN, RuW, RuN, and TaRuN.

[0095] Example 13. The method of claim 10 further comprises: forming a hard mask layer over the absorber layer prior to forming the boundary layer.

[0096] Example 14. The method of claim 13, wherein the pattern in the boundary layer exposes the hard mask layer.

[0097] Example 15. The method of claim 10, wherein the width of the protrusions in the pattern in the boundary layer in a cross-sectional view is less than or equal to 25 nm.

[0098] Example 16 is a photomask comprising: a substrate; a reflective multilayer disposed over the substrate; an absorber layer disposed over the reflective multilayer, including a pattern in the absorber layer; and a boundary layer surrounding the pattern in the absorber layer in a plan view, wherein the refractive index of the boundary layer is in the range of 0.87 to 1, and the extinction coefficient is greater than or equal to 0.02.

[0099] Example 17. The photomask of claim 16, wherein the extinction coefficient of the boundary layer ranges from 0.02 to 0.1.

[0100] Example 18. The photomask of claim 16, wherein the distance between the uppermost surface of the boundary layer and the uppermost surface of the substrate is greater than that between the uppermost surface of the absorber layer.

[0101] Example 19. The photomask of claim 16 further includes: a hard mask layer disposed between the absorber layer and the boundary layer.

[0102] Example 20. The photomask of claim 19, wherein the boundary layer comprises: a first boundary layer disposed over the hard mask layer; and a second boundary layer disposed over the first boundary layer, wherein the first boundary layer and the second boundary layer are made of different materials.

Claims

1. A method for manufacturing a photomask, comprising: A boundary layer is formed above the photomask blank. The photomask blank includes: Substrate; A reflective multilayer is disposed above the substrate; and An absorber layer is disposed above the reflective multilayer; A portion of the boundary layer is removed to form a recess surrounded by the boundary layer; and Selectively removing portions of the absorber layer in the recess to form a pattern in the absorber layer. The refractive index of the boundary layer ranges from 0.87 to 1, and the extinction coefficient is greater than or equal to 0.

02.

2. The method according to claim 1, wherein, The extinction coefficient of the boundary layer ranges from 0.02 to 0.

1.

3. The method according to claim 1, further comprising: Before forming the boundary layer on the photomask blank, a hard mask layer is formed on the photomask blank.

4. The method according to claim 3, wherein, During the removal of a portion of the boundary layer, a portion of the hard mask layer is exposed.

5. The method according to claim 3, wherein, Forming the boundary layer further includes: A first boundary layer is formed above the hard mask layer; and A second boundary layer is formed above the first boundary layer. The first boundary layer and the second boundary layer are made of different materials.

6. The method according to claim 3, wherein, Forming the hard mask layer further includes: A first hard mask layer is formed on top of the photomask blank; and A second hard mask layer is formed above the first hard mask layer. The first hard mask layer and the second hard mask layer are made of different materials.

7. The method according to claim 6, further comprising: A third hard mask layer is formed above the second hard mask layer, wherein the third hard mask layer is made of a different material than the second hard mask layer.

8. The method according to claim 1, wherein, The photomask blank includes a cover layer disposed between the reflective multilayer and the absorber layer.

9. A method for manufacturing a photomask, comprising: A boundary layer is formed above the photomask blank. The photomask blank includes: Substrate; A reflective multilayer is disposed above the substrate; and An absorber layer is disposed above the reflective multilayer; A pattern is formed in the outer region of the boundary layer, and an opening is formed in the second region of the boundary layer surrounded by the outer region. The pattern in the boundary layer includes at least two spaced-apart grooves and two spaced-apart protrusions on each side of the boundary layer in a cross-sectional view; and Selectively removing portions of the absorber layer within the opening to form a pattern within the absorber layer. The boundary layer includes at least one selected from the group consisting of: Rh, Pd, Ir, Pt, Co, Ni, Te, Cr, W, Hf, Ta, PtRu, PtIr, PtRh, PtPd, PtNi, PtCo, PtTa, PtCr, PtTi, IrTa, IrCr, IrW, IrTe, IrNi, IrCo, CrN, NiCo, RhCo, RhNi, RhCr, RhW, and RhTa.

10. A photomask, comprising: Substrate; A reflective multilayer is disposed above the substrate; An absorber layer, disposed above the reflective multilayer, including a pattern in the absorber layer; as well as Boundary layer, in a plan view, surrounding the pattern within the absorber layer. The refractive index of the boundary layer ranges from 0.87 to 1, and the extinction coefficient is greater than or equal to 0.02.

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