Reflective mask, blank substrate, method for manufacturing a reflective mask, and method for manufacturing a blank substrate

Abstract

The objective is to provide a blank substrate that exhibits excellent processability and can provide a reflective mask that can suppress the reduction in EUV reflectivity in the reflective region, a reflective mask that can suppress the reduction in EUV reflectivity in the reflective region, and a method for manufacturing a reflective mask. [Solution] A reflective mask comprising a substrate, a reflective layer, a cap layer containing a first metal, an oxide layer, and an absorption layer containing a second metal, laminated in at least this order, wherein the oxide layer contains an oxide of the first metal and / or the second metal, the reflective mask has a first surface on the absorption layer side and a second surface on the substrate side, the first surface has a mask pattern region on which a mask pattern is formed, and the mask pattern region includes an absorption region where the absorption layer exists and a reflective region where the absorption layer does not exist.

Description

Technical Field

[0006] , ,

[0005] , , ,

[0001] The present disclosure relates to a reflective mask, a blank substrate, a method for manufacturing a reflective mask, and a method for manufacturing a blank substrate.

Background Art

[0002] A reflective EUV mask used in extreme ultraviolet (EUV) lithography typically includes a reflective layer composed of a multilayer film on a substrate and an absorption layer having a predetermined pattern. The reflective layer has a very precise periodic structure to improve the reflection efficiency of EUV, and the reflection efficiency of EUV decreases due to damage caused by cleaning liquid or plasma treatment. Therefore, a cap layer for protecting the reflective layer may be disposed on the surface of the reflective layer. [[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​​​​For example, when an absorption layer containing metallic Ta and a capping layer containing metallic Ru are in direct contact, a migration layer made of a Ta-Ru alloy may be formed due to the diffusion of both metals. While such a migration layer has EUV absorption properties, it has a low etching rate when fabricating a reflective mask and is difficult to remove by etching a normal absorption layer. Therefore, when fabricating a reflective mask from a blank substrate, such a migration layer is likely to remain in the reflective region, and if it remains, it becomes a factor that reduces the EUV reflectivity of the resulting reflective mask.

[0007] Therefore, from the viewpoint of suppressing the decrease in EUV reflectivity in the reflective region and improving the processability of the blank substrate, it is desirable to suppress the migration of the absorption layer material.

[0008] This disclosure has been made in view of the above-mentioned problems, and aims to provide a blank substrate that has excellent processability and can provide a reflective mask that can suppress the reduction of EUV reflectivity in the reflective region, a reflective mask that can suppress the reduction of EUV reflectivity in the reflective region, a method for manufacturing a reflective mask, and a method for manufacturing a blank substrate. [Means for solving the problem]

[0009] A reflective mask in one embodiment of the present disclosure is A reflective mask comprising a substrate, a reflective layer, a cap layer containing a first metal, an oxide layer, and an absorbing layer containing a second metal, laminated in at least this order, The oxide layer comprises an oxide of the first metal and / or the second metal. The reflective mask has a first surface on the absorbent layer side and a second surface on the substrate side. The first surface has a mask pattern region in which a mask pattern is formed, The mask pattern region includes an absorption region where the absorption layer exists and a reflection region where the absorption layer does not exist.

[0010] A blank substrate in one embodiment of this disclosure is The device comprises a substrate, a reflective layer, a cap layer containing a first metal, an oxide layer, and an absorbing layer containing a second metal, laminated in at least this order. The oxide layer comprises an oxide of the first metal and / or the second metal.

[0011] A method for manufacturing a reflective mask according to one embodiment of the present disclosure is: A preparation step for preparing a blank substrate comprises a substrate, a reflective layer, a cap layer containing a first metal, an oxide layer, and an absorption layer containing a second metal, laminated in at least this order, wherein the oxide layer contains an oxide of the first metal and / or the second metal. A film formation step of forming a resist layer on the absorption layer of the blank substrate, A resist pattern formation step involves performing electron beam or laser light writing and development processing to form a resist pattern on the resist layer, The process includes a mask pattern formation step of selectively etching the region of the absorption layer in which the resist pattern does not exist, thereby forming a mask pattern region that includes an absorption region in which the absorption layer exists and a reflection region in which the absorption layer does not exist. The mask pattern formation step includes an oxide layer removal step in which the oxide layer is removed in the reflection region.

[0012] A method for manufacturing a blank substrate according to one embodiment of the present disclosure is: The blank substrate comprises a base material, a reflective layer, a cap layer containing a first metal, an oxide layer, and an absorption layer containing a second metal, laminated in at least this order. The oxide layer comprises an oxide of the first metal and / or the second metal. The process includes an oxide layer formation step in which the oxide layer is formed on the cap layer by sputtering or by oxidizing the surface of the cap layer. [Effects of the Invention]

[0013] According to the present disclosure, it is possible to provide a blank substrate that has excellent processability and can suppress a decrease in EUV reflectivity in a reflective region, a reflective mask that can suppress a decrease in EUV reflectivity in the reflective region, and a method for manufacturing the reflective mask.

Brief Description of the Drawings

[0014] [Figure 1A] It is an example of a cross-sectional view of the blank substrate of the present disclosure. [Figure 1B] It is another example of a cross-sectional view of the blank substrate of the present disclosure. [Figure 2A] It is an example of a plan view of the reflective mask of the present disclosure as viewed from the absorption layer side. [Figure 2B] It is an example of a plan view of the reflective mask of the present disclosure as viewed from the substrate side. [Figure 2C] It is an example of a cross-sectional view taken along line A-A in FIG. 1A. [Figure 2D] It is an enlarged view of the region surrounded by the broken line in FIG. 2C. [Figure 2E] It is another example of an enlarged cross-sectional view near the absorption layer in the mask pattern region. [Figure 2F] It is another example of a cross-sectional view of the reflective mask of the present disclosure. [Figure 2G] It is another example of a cross-sectional view of the reflective mask of the present disclosure. [Figure 2H] It is another example of a cross-sectional view of the reflective mask of the present disclosure. [Figure 2I] It is another example of an enlarged cross-sectional view near the absorption layer in the mask pattern region. [Figure 2J] It is another example of an enlarged cross-sectional view near the absorption layer in the mask pattern region. [Figure 2K] It is an example of a schematic diagram of an X-ray absorption fine structure spectrum. [Figure 3A] It is a schematic diagram showing an example of a method for manufacturing the reflective mask of the present disclosure. [Figure 3B] It is a schematic diagram showing an example of a method for manufacturing the reflective mask of the present disclosure. [Figure 3C]This is a schematic diagram showing an example of a method for manufacturing the reflective mask described herein. [Figure 3D] This is a schematic diagram showing an example of a method for manufacturing the reflective mask described herein. [Figure 3E] This is a schematic diagram showing an example of a method for manufacturing the reflective mask described herein. [Figure 3F] This is a schematic diagram showing an example of a method for manufacturing the reflective mask described herein. [Figure 3G] This is a schematic diagram showing an example of a method for manufacturing the reflective mask described herein. [Figure 3H] This is a schematic diagram showing an example of a method for manufacturing the reflective mask described herein. [Figure 3I] This is a schematic diagram showing an example of a method for manufacturing the reflective mask described herein. [Figure 3J] This is a schematic diagram showing an example of a method for manufacturing the reflective mask described herein. [Figure 3K] This is a schematic diagram showing an example of a method for manufacturing the reflective mask described herein. [Figure 3L] This is a schematic diagram showing an example of a method for manufacturing the reflective mask described herein. [Figure 3M] This is a schematic diagram showing an example of a method for manufacturing the reflective mask described herein. [Figure 3N] This is a schematic diagram showing an example of a method for manufacturing the reflective mask described herein. [Figure 3O] This is a schematic diagram showing an example of a method for manufacturing the reflective mask described herein. [Figure 3P] This is a schematic diagram showing an example of a method for manufacturing the reflective mask described herein. [Figure 3Q] This is a schematic diagram showing an example of a method for manufacturing the reflective mask described herein. [Figure 4] This is a schematic diagram illustrating an example of how to use the reflective mask of this disclosure. [Modes for carrying out the invention]

[0015] The embodiments of the present invention (hereinafter referred to as "the present disclosure") will be described in detail below, with reference to the drawings as necessary. However, the present disclosure is not limited thereto, and various modifications are possible without departing from its essence. In the drawings, the same elements will be denoted by the same reference numerals, and redundant explanations will be omitted. Furthermore, unless otherwise specified, positional relationships such as up, down, left, and right will be based on the positional relationships shown in the drawings. Moreover, the dimensional ratios in the drawings are not limited to those shown.

[0016] Unless otherwise specified in this specification and / or these drawings, the following interpretations shall apply:

[0017] In this specification and these drawings, unless otherwise specified, terms such as "substrate," "base material," and "sheet," which refer to the material that forms the basis of a certain configuration, are not distinguished from one another solely on the basis of differences in designation.

[0018] In this specification and these drawings, unless otherwise specified, terms that define shape, geometric conditions, and their degree, such as "parallel" and "orthogonal," as well as values ​​of length and angle, shall be interpreted not strictly, but to include a range that allows for the expectation of similar functionality.

[0019] In this specification and these drawings, unless otherwise specified, a configuration such as a member or region being "above," "below," "upper side," "lower side," or "upward" or "downward" of another configuration such as a member or region includes cases where one configuration is in direct contact with another configuration. Furthermore, this also includes cases where another configuration is included between one configuration and another configuration, i.e., cases where they are indirectly in contact. In addition, unless otherwise specified, the terms "above," "upper side," or "upward," or "below," "lower side," or "downward," may be used with the direction of up and down reversed.

[0020] In this specification and these drawings, unless otherwise specified, the state in which a face of element A "facing" a face of element B includes not only the case where a face of element A is in contact with a face of element B, but also the case where element C is located between the faces of element A and element B. In other words, the term "facing" is a term that describes the orientation of the two faces.

[0021] In this specification and these drawings, unless otherwise specified, identical or similarly functioning parts are denoted by the same or similar reference numerals, and repeated explanations may be omitted. Furthermore, the dimensional ratios in the drawings may differ from the actual ratios for illustrative purposes, and some components may be omitted from the drawings.

[0022] Unless otherwise specified, this specification and these drawings may be combined with other embodiments and modifications to the extent that they do not contradict each other. Furthermore, other embodiments may be combined with each other, and other embodiments with modifications to the extent that they do not contradict each other. Furthermore, modifications may be combined with each other to the extent that they do not contradict each other.

[0023] In this specification and these drawings, unless otherwise specified, when multiple steps are disclosed regarding a method such as a manufacturing method, other steps not disclosed may be performed between the disclosed steps. Furthermore, the order of the disclosed steps is arbitrary as long as it does not cause inconsistencies.

[0024] The numerical range described in this disclosure may be defined by combining any one of several candidate upper limits and any one of several candidate lower limits. In addition, unless otherwise specified, the numerical range may be defined by combining any two of several candidate upper limits, or by combining any two of several candidate lower limits.

[0025] In this disclosure, the lamination direction D3 is the lamination direction in which the substrate 10, the reflective layer 20, and the absorbent layer 40 are laminated. Directions D1 and D2 are in-plane directions of the reflective mask 1 and are perpendicular to direction D3. Directions D1 and D2 may also be perpendicular to each other.

[0026] In this disclosure, "plan view" refers to the field of view of the reflective mask 1 from the stacking direction D3. "Cross-sectional view" refers to the field of view of the cross-section of the reflective mask 1 parallel to the stacking direction D3.

[0027] One embodiment of this disclosure describes an example of forming a circuit pattern on a wafer by reflecting EUV light using a reflective mask. However, the applications of the reflective mask are not limited to this, and this disclosure can be applied to reflective masks used for various purposes. For example, alignment marks and inspection patterns may be formed on the wafer using a reflective mask in addition to circuit patterns. Furthermore, nanophotonic structures and minute fluid channels may be formed on any substrate other than a wafer using a reflective mask, in order to develop nanoscale devices and materials. Also, the light reflected by the reflective mask is not limited to EUV light.

[0028] A first aspect of the present disclosure is a reflective mask comprising a substrate, a reflective layer, a cap layer containing a first metal, an oxide layer, and an absorbing layer containing a second metal, laminated in at least this order. The oxide layer comprises an oxide of the first metal and / or the second metal. The reflective mask has a first surface on the absorbent layer side and a second surface on the substrate side. The first surface has a mask pattern region in which a mask pattern is formed, The mask pattern region includes an absorption region where the absorption layer exists and a reflection region where the absorption layer does not exist.

[0029] A second aspect of this disclosure relates to the reflective mask of the first aspect described above, The first metal comprises one or more selected from the group consisting of Ru, Rh, Hf, Cr, and Zr.

[0030] A third aspect of this disclosure relates to the reflective mask of the first or second aspect described above, The second metal includes one or more selected from the group consisting of Ta, W, Nb, Pt, Cr, Ni, Sn, In, Te, Sb, and Ti.

[0031] A fourth aspect of this disclosure is a reflective mask in any one of the first to third aspects described above, The thickness Ho of the oxide layer is 0.3 nm or more and 1.0 nm or less.

[0032] A fifth aspect of this disclosure is a reflective mask in any one of the first to fourth aspects described above, The ratio of the thickness Hk of the absorption layer to the thickness Ho of the oxide layer (Hk / Ho) is 20 or more and 250 or less.

[0033] A sixth aspect of this disclosure is a reflective mask in any one of the first to fifth aspects described above, In the reflective region, the cap layer is exposed.

[0034] A seventh aspect of this disclosure relates to a reflective mask in any one of the first to sixth aspects described above. The Ta peak intensity in the X-ray absorption fine structure spectrum of the reflection region is 1 / 50 or less of the Ta peak intensity in the X-ray absorption fine structure spectrum of the absorption region.

[0035] The eighth aspect of this disclosure relates to a reflective mask in any one of the first to seventh aspects described above, The concentration of Ta in the cap layer in the reflection region is 1000 ppm or less.

[0036] The ninth aspect of this disclosure relates to a reflective mask in any one of the first to eighth aspects described above, In a cross-sectional view, the laminate in the absorption region, including the absorption layer and the oxide layer, has a tapered shape that widens from the absorption layer side toward the boundary between the oxide layer and the cap layer.

[0037] A tenth aspect of this disclosure relates to the reflective mask of the ninth aspect described above, In a cross-sectional view, the tapered side surface of the laminate has a straight portion and a curved portion connected to the straight portion. The height from the boundary to the connection point between the straight section and the curved section is 0.1 nm or more and 15 nm or less. In a plan view, the distance between the connecting portion and the end of the laminate at the boundary is between 1.0 nm and 5.2 nm.

[0038] An eleventh aspect of this disclosure relates to the reflective mask of the ninth or tenth aspect described above, In a plan view, the distance between the edge of the upper surface of the laminate and the edge of the laminate at the boundary is between 1.0 nm and 6.0 nm.

[0039] A twelfth aspect of this disclosure relates to a reflective mask in any one of the first to eleventh aspects described above, In a cross-sectional view, the laminate in the absorption region, including the absorption layer and the oxide layer, has a shape in which the width narrows from the absorption layer side toward the boundary between the oxide layer and the cap layer.

[0040] A thirteenth aspect of this disclosure relates to a reflective mask in any one of the first to twelfth aspects described above. The side and top surfaces of the absorption layer in the absorption region are covered with a coating layer containing the oxide of the second metal.

[0041] A fourteenth aspect of this disclosure relates to the reflective mask of the thirteenth aspect described above, The thickness Hh of the aforementioned coating layer is 1 nm or more and 8 nm or less.

[0042] A fifteenth aspect of this disclosure relates to the reflective mask of the thirteenth or fourteenth aspect described above, The ratio of the thickness Hk of the absorption layer to the thickness Hh of the coating layer (Hk / Hh) is 3 or more and 80 or less.

[0043] A sixteenth aspect of this disclosure relates to a reflective mask in any one of the thirteenth to fifteenth aspects described above. On the side of the coating layer opposite to the substrate, there is a second absorbent layer or topcoat layer containing a third metal.

[0044] A 17th aspect of this disclosure relates to the reflective mask of the 16th aspect described above, The third metal includes one or more selected from the group consisting of Ru, Ta, W, Nb, Pt, Rh, Re, Cr, and Ti.

[0045] The eighteenth aspect of this disclosure is a blank substrate, The device comprises a substrate, a reflective layer, a cap layer containing a first metal, an oxide layer, and an absorbing layer containing a second metal, laminated in at least this order. The oxide layer comprises an oxide of the first metal and / or the second metal.

[0046] A 19th aspect of this disclosure relates to the blank substrate of the 18th aspect described above, The first metal comprises one or more selected from the group consisting of Ru, Rh, Hf, Cr, and Zr.

[0047] A 20th aspect of this disclosure relates to the blank substrate of the 18th or 19th aspect described above, The second metal includes one or more selected from the group consisting of Ta, W, Nb, Pt, Cr, Ni, Sn, In, Te, Sb, and Ti.

[0048] A 21st aspect of this disclosure relates to a blank substrate in any one of the 18th to 20th aspects described above, The thickness Ho of the oxide layer is 0.3 nm or more and 1.0 nm or less.

[0049] A 22nd aspect of this disclosure relates to a blank substrate in any one of the 18th to 21st aspects described above, The ratio of the thickness Hk of the absorption layer to the thickness Ho of the oxide layer (Hk / Ho) is 20 or more and 250 or less.

[0050] A 23rd aspect of this disclosure relates to a blank substrate in any one of the 18th to 22nd aspects described above, The absorption layer is provided on the side opposite to the substrate with a coating layer containing the oxide of the second metal.

[0051] A 24th aspect of this disclosure relates to the blank substrate of the 23rd aspect described above, The thickness Hh of the aforementioned coating layer is 1 nm or more and 8 nm or less.

[0052] A 25th aspect of this disclosure relates to the blank substrate of the 23rd or 24th aspect described above, The ratio of the thickness Hk of the absorption layer to the thickness Hh of the coating layer (Hk / Hh) is 3 or more and 80 or less.

[0053] A 26th aspect of this disclosure relates to a blank substrate in any one of the 23rd to 25th aspects described above. On the side of the coating layer opposite to the substrate, there is a second absorbent layer or topcoat layer containing a third metal.

[0054] A 27th aspect of this disclosure relates to the blank substrate of the 26th aspect described above, The third metal includes one or more selected from the group consisting of Ru, Ta, W, Nb, Pt, Rh, Re, Cr, and Ti.

[0055] A 28th aspect of this disclosure is a method for manufacturing a reflective mask, A preparation step for preparing a blank substrate comprises a substrate, a reflective layer, a cap layer containing a first metal, an oxide layer, and an absorption layer containing a second metal, laminated in at least this order, wherein the oxide layer contains an oxide of the first metal and / or the second metal. A film formation step of forming a resist layer on the absorption layer of the blank substrate, A resist pattern formation step involves performing electron beam or laser light writing and development processing to form a resist pattern on the resist layer, The process includes a mask pattern formation step of selectively etching the region of the absorption layer in which the resist pattern does not exist, thereby forming a mask pattern region that includes an absorption region in which the absorption layer exists and a reflection region in which the absorption layer does not exist. The mask pattern formation step includes an oxide layer removal step in which the oxide layer is removed in the reflection region.

[0056] A 29th aspect of this disclosure relates to the manufacturing method of the 28th aspect described above, The process includes an absorption layer oxidation step, in which the absorption layer in the absorption region is subjected to oxidation treatment.

[0057] A 30th aspect of this disclosure is a method for manufacturing a blank substrate, The blank substrate comprises a base material, a reflective layer, a cap layer containing a first metal, an oxide layer, and an absorption layer containing a second metal, laminated in at least this order. The oxide layer comprises an oxide of the first metal and / or the second metal. The process includes an oxide layer formation step in which the oxide layer is formed on the cap layer by sputtering or by oxidizing the surface of the cap layer.

[0058] A 31st aspect of this disclosure relates to the manufacturing method of the 30th aspect described above, The blank substrate comprises a coating layer containing the oxide of the second metal on the side of the absorption layer opposite to the substrate, The ratio of the thickness Hk of the absorption layer to the thickness Hh of the coating layer (Hk / Hh) is 3 or more and 80 or less.

[0059] Hereinafter, one embodiment of the present disclosure will be described in detail with reference to the drawings. The embodiment shown below is an example of the embodiments of the present disclosure, and the present disclosure shall not be construed as being limited to these embodiments only.

[0060] 1. Blank circuit board Figure 1A is an example of a cross-sectional view of a blank substrate of the present disclosure. As shown in Figure 1A, the blank substrate 2A of the present disclosure comprises a base material 10, a reflective layer 20, a cap layer 30 containing a first metal, an oxide layer 70, and an absorption layer 40 containing a second metal, laminated in at least this order, wherein the oxide layer 70 contains an oxide of the first metal and / or an oxide of the second metal. The blank substrate 2A may also have a coating layer 80 above the absorption layer 40 in the lamination direction D3, and a topcoat layer 90 above the coating layer 80 in the lamination direction D3. The blank substrate 2A may also have a conductive layer 60 on the side of the base material 10 opposite to the reflective layer 20.

[0061] The cap layer 30 contains a first metal, and the absorption layer 40 contains a second metal. The second metal also has the property of readily absorbing EUV light. Conventionally, in a configuration in which the cap layer 30 and the absorption layer 40 are in direct contact, when these layers are in contact for a long time or in a harsh environment such as high temperature or vacuum, the first metal of the cap layer 30 may migrate to the absorption layer 40, or the second metal of the absorption layer 40 may migrate to the cap layer 30. In this regard, in the blank substrate 2A of this disclosure, an oxide layer 70 containing oxides of the first metal and / or the second metal is located between the cap layer 30 and the absorption layer 40, thereby suppressing migration between the two layers and preventing the formation of an alloy layer containing the first and second metals. Migration is also suppressed between the oxide layer 70 and the cap layer 30 and the absorption layer 40. As a result, the reflective region of the reflective mask can be formed from the blank substrate of this disclosure by normal etching. Furthermore, it is possible to suppress the remaining presence of the second metal, which is the material of the absorption layer 40, in the reflective region without removal, thereby suppressing the decrease in EUV reflectivity in the reflective region. In other words, by using the blank substrate 2A of this disclosure, it is possible to improve the processability of the blank substrate while suppressing the decrease in EUV reflectivity in the reflective region.

[0062] In particular, in conventional blank substrates, when the absorption layer contains Ta and the capping layer contains Ru, the alloy layer of Ta and Ru that may be formed has a slow processing speed due to etching methods such as dry etching. Therefore, it was difficult to etch the alloy layer simultaneously with the absorption layer. In this respect, the blank substrate 2A of this disclosure suppresses the formation of the alloy layer of Ta and Ru, thereby suppressing the occurrence of the above-mentioned problem.

[0063] The oxides of the first and second metals possess strong metal-oxygen bonds and tend to be thermally and chemically stable, thus easily suppressing the migration of metal elements. Furthermore, the oxides of the first and second metals tend to have a dense structure, which also helps suppress the migration of metal elements. As a result, it is believed that by having an oxide layer 70 in the blank substrate 2A, migration of the second metal contained in the absorption layer 40 to the cap layer 30 can be suppressed, and migration of the first metal contained in the cap layer 30 to the absorption layer 40 can be suppressed.

[0064] The following details the various configurations that blank board 2A may have.

[0065] 1.1. Base material The substrate 10 supports each layer, such as the reflective layer 20 and the absorbing layer 40, that constitute the reflective EUV mask, and plays a role in minimizing the thermal and mechanical effects that occur during EUV irradiation. In particular, since the temperature rise associated with EUV irradiation affects the pattern transfer accuracy, the substrate requires a low coefficient of thermal expansion and high dimensional stability.

[0066] To satisfy these requirements, the base material 10 is not particularly limited, but examples include synthetic quartz glass, amorphous glass with a low coefficient of thermal expansion (e.g., SiO2-TiO2 glass), and crystallized glass with a β-quartz solid solution precipitated. The base material 10 may be used alone or two or more in combination.

[0067] When EUV light is irradiated onto the reflective mask 1, the temperature of the reflective mask 1 rises due to the absorption of the EUV light. To suppress the decrease in reflection accuracy when the temperature rises, it is preferable that the substrate 10 has a low coefficient of thermal expansion. For example, the coefficient of thermal expansion of the substrate 10 at 20°C is preferably 50 ppb / K or less, 25 ppb / K or less, 10 ppb / K or less, 5 ppb / K or less, and 1 ppb / K or less. The lower limit of the coefficient of thermal expansion is not particularly limited, but it may be below the detection limit.

[0068] The reflective layer 20, which is placed on the substrate 10, may require high smoothness to accurately reflect EUV light in the intended direction. Therefore, it is preferable that the surface of the substrate 10 supporting the reflective layer 20 is also smooth. For example, the flatness (PV value) of the surface of the substrate 10 on the side of the reflective layer 20 is preferably 50 nm or less. In addition, the arithmetic mean roughness Ra of the surface of the substrate 10 on the side of the reflective layer 20 is preferably 0.06 nm or less.

[0069] The thickness of the base material 10 is not particularly limited, but may be, for example, 3 mm or more and 8 mm or less.

[0070] 1.2.Reflective layer The reflective layer 20 is located on the upper side of the substrate 10 in the stacking direction D3, and other layers may or may not be placed between the reflective layer 20 and the substrate 10. The reflective layer 20 is a layer that efficiently reflects incident extreme ultraviolet (EUV) light in a reflective EUV mask and accurately transfers fine patterns during the exposure process. Since EUV light (typically with a wavelength of about 13.5 nm) is extremely short compared to the wavelength of visible light, specular reflection by ordinary single-layer metal films is difficult. Therefore, EUV reflective layers generally employ a multilayer film structure in which multiple materials are stacked alternately at a constant period, and high reflectivity is obtained by utilizing Bragg reflection. From the viewpoint of reflectivity, the reflective layer 20 is typically configured as a thin film layer with a multilayer structure.

[0071] A common example of a reflective layer configuration is a Mo / Si multilayer film, in which molybdenum (Mo) and silicon (Si) layers are alternately stacked. Typically, 30 to 60 pairs (e.g., 40 pairs) of Mo and Si layers can be stacked alternately, totaling 60 to 120 layers. The film thickness ratio of each layer is adjusted to maximize Bragg reflection for EUV wavelengths, generally achieving a high reflectivity of approximately 60-70% for EUV light at a wavelength of 13.5 nm.

[0072] The specific layer configuration of the reflective layer 20 is not particularly limited, but examples include a Mo / Si periodic multilayer film in which Mo layers and Si layers are alternately stacked, a ruthenium (Ru) / Si periodic multilayer film, a Mo / beryllium (Be) periodic multilayer film, a Mo compound / Si compound periodic multilayer film, a Si / niobium (Nb) periodic multilayer film, a Si / Mo / Ru periodic multilayer film, a Si / Mo / Ru / Mo periodic multilayer film, and a Si / Ru / Mo / Ru periodic multilayer film. Among these, a Mo / Si periodic multilayer film is preferred. When the reflective layer 20 is a periodic multilayer film, it is preferable that the reflective layer 20 has a layer structure with 30 to 60 periods.

[0073] The thickness of each layer in the reflective layer 20 is not particularly limited, but may be, for example, 1 nm to 10 nm. Also, the thickness of the reflective layer 20 is not particularly limited, but may be, for example, 60 nm to 1200 nm.

[0074] 1.3. Capping layer The cap layer 30 is a layer that covers the top layer of the reflective layer 20 and is intended to protect the reflective layer 20 from oxidation, contamination, and damage during cleaning and repair. The cap layer 30 contains a first metal. The first metal is not particularly limited, but examples include Ru, Rh, Hf, Zr, and Cr, with Ru being preferred among these. The first metal may be used alone or in combination of two or more.

[0075] The thickness Hc of the cap layer 30 is not particularly limited, but for example it may be 2 nm or more, 3 nm or more, or 4 nm or more. Also, the thickness Hc of the cap layer 30 is not particularly limited, but for example it may be 15 nm or less, 14 nm or less, or 13 nm or less. Furthermore, the thickness Hc of the cap layer 30 may be determined by any combination of any one of the above-mentioned lower limit candidate values ​​and any one of the above-mentioned upper limit candidate values. Specifically, the thickness Hc of the cap layer 30 is not particularly limited, but for example it may be 2 nm or more and 15 nm or less, 3 nm or more and 14 nm or less, or 4 nm or more and 13 nm or less.

[0076] 1.4. Absorption layer The absorption layer 40 is positioned above the reflective layer 20 in the stacking direction D3. A cap layer 30 and an oxide layer 70 are positioned between the reflective layer 20 and the absorption layer 40. When a reflective mask is fabricated from a blank substrate 2A, the absorption layer 40 is patterned based on a desired circuit pattern to be formed on the wafer and configured to selectively absorb EUV light in a predetermined region.

[0077] By adjusting the thickness, refractive index, extinction coefficient, etc., of the absorption layer 40, it is possible to adjust the absorption rate and reflectance of EUV light in the absorption layer 40 as intended, and in some cases, to produce an optical phase shift effect.

[0078] The absorption layer 40 contains a second metal. The second metal is not particularly limited as long as it readily absorbs EUV, but examples include Ta, W, Nb, Pt, Cr, Ni, Sn, In, Te, Sb, and Ti, with Ta being preferred among these. The second metal may be used alone or in combination of two or more. Furthermore, the first metal and the second metal may be the same or different from each other.

[0079] The thickness Hk of the absorption layer 40 is preferably 25 nm or more, 30 nm or more, or 35 nm or more. Alternatively, the thickness Hk of the absorption layer 40 is preferably 75 nm or less, 70 nm or less, or 65 nm or less. Furthermore, the thickness Hk of the absorption layer 40 may be determined by a combination of any one of the above-mentioned lower limit candidate values ​​and any one of the above-mentioned upper limit candidate values. Specifically, for example, the thickness Hk of the absorption layer 40 is preferably 25 nm to 75 nm, 30 nm to 70 nm, or 35 nm to 65 nm. This improves the EUV absorption while preventing the blank substrate 2A from becoming too thick overall.

[0080] 1.5. Oxide layer The oxide layer 70 is positioned between the cap layer 30 and the absorption layer 40, suppressing the migration of the second metal contained in the absorption layer 40 to the cap layer 30 side, and suppressing the migration of the first metal contained in the cap layer 30 to the absorption layer 40 side. The oxide layer 70 contains oxides of the first metal and / or the second metal.

[0081] If the oxide layer 70 contains an oxide of the first metal, the oxide layer 70 may contain an oxide of the first metal using the same first metal as the cap layer 30. Also, if the oxide layer 70 contains an oxide of the second metal, the oxide layer 70 may contain an oxide of the second metal using the same second metal as the absorption layer 40. The oxide layer 70 may be made of a single material or two or more materials in combination.

[0082] The thickness Ho of the oxide layer 70 is preferably 0.3 nm or more, 0.4 nm or more, or 0.5 nm or more. Alternatively, the thickness Ho of the oxide layer 70 is preferably 1.0 nm or less, 0.9 nm or less, 0.8 nm or less, or 0.7 nm or less. Furthermore, the thickness Ho of the oxide layer 70 may be determined by any combination of any one of the above-mentioned lower limit candidate values ​​and any one of the above-mentioned upper limit candidate values. Specifically, for example, the thickness Ho of the oxide layer 70 is preferably 0.3 nm or more and 1.0 nm or less, 0.4 nm or more and 0.9 nm or less, 0.5 nm or more and 0.8 nm or less, or 0.5 nm or more and 0.7 nm or less. This suppresses migration of the second metal contained in the absorption layer 40 to the cap layer 30 side, and suppresses migration of the first metal contained in the cap layer 30 to the absorption layer 40 side, while preventing the blank substrate 2A from becoming too thick overall or reducing the processability of the blank substrate 2A.

[0083] The ratio (Hk / Ho) of the thickness of the absorption layer 40 to the thickness of the oxide layer 70 Ho is preferably 20 or more, 30 or more, or 40 or more. Furthermore, the ratio (Hk / Ho) is preferably 250 or less, 225 or less, or 200 or less. In addition, the ratio (Hk / Ho) may be determined by a combination of any one of the above-mentioned lower limit candidate values ​​and any one of the above-mentioned upper limit candidate values. Specifically, for example, the ratio (Hk / Ho) is preferably 20 to 250, 30 to 225, or 40 to 200. This tends to suppress the migration of the second metal in the absorption layer 40 and the migration of the first metal in the cap layer 30, suppress the decrease in the EUV absorption efficiency of the absorption layer 40, and suppress the overall thickness of the blank substrate 2A.

[0084] The ratio (Hc / Ho) of the thickness of the cap layer 30 to the thickness of the oxide layer 70 (Ho) is preferably 1.5 or more, 2.0 or more, and may be 5.0 or more. Furthermore, the ratio (Hc / Ho) is preferably 75.0 or less, 50.0 or less, 40.0 or less, 30.0 or less, 20.0 or less, and may be 10.0 or less. Additionally, the ratio (Hc / Ho) may be determined by any combination of any one of the above-mentioned lower limit candidate values ​​and any one of the above-mentioned upper limit candidate values. Specifically, for example, the ratio (Hc / Ho) is preferably 1.5 or more and 75.0 or less, 2.0 or more and 50.0 or less, 5.0 or more and 40.0 or less, 5.0 or more and 30.0 or less, 5.0 or more and 20.0 or less, and 5.0 or more and 10.0 or less. This tends to suppress migration of the second metal in the absorption layer 40 and the first metal in the cap layer 30, protect the reflective layer 20, and reduce the overall thickness of the blank substrate 2A.

[0085] 1.6. Conductive layer The conductive layer 60 is a conductive thin film provided on the second surface 1b side of the reflective EUV mask, and is provided for holding the reflective mask 1 in the exposure apparatus by an electrostatic chuck when in use. The material of the conductive layer 60 is not particularly limited, but examples include metals or metal compounds (e.g. oxides, nitrides) that exhibit conductivity, such as Cr and Ta. The conductive layer 60 may be made of one material alone, or two or more materials may be used in combination. The thickness of the conductive layer 60 is not particularly limited, but may be, for example, 30 nm to 150 nm.

[0086] 1.7.Coating layer The coating layer 80 is positioned above the absorption layer 40 in the stacking direction D3 and is intended to protect the absorption layer 40 from oxidation, contamination, and damage during cleaning. The coating layer 80 preferably contains an oxide of the second metal, and more preferably contains an oxide of Ta. It is also preferable that the coating layer 80 contains the same oxide of the second metal as the absorption layer 40. The material of the coating layer 80 may be one type alone or two or more types in combination.

[0087] The thickness Hh of the coating layer 80 is preferably 1.0 nm or more, 1.5 nm or more, 2.0 nm or more, or 3.0 nm or more. Alternatively, the thickness Hh of the coating layer 80 is preferably 8.0 nm or less, 7.5 nm or less, 7.0 nm or less, or 6.0 nm or less. Furthermore, the thickness Hh of the coating layer 80 may be determined by any combination of any one of the above-mentioned lower limit candidate values ​​and any one of the above-mentioned upper limit candidate values. Specifically, for example, the thickness Hh of the coating layer 80 is preferably 1.0 nm or more and 8.0 nm or less, 1.5 nm or more and 7.5 nm or less, 2.0 nm or more and 7.0 nm or less, or 3.0 nm or more and 6.0 nm or less. This makes it easier to protect the absorption layer 40 while suppressing the blank substrate 2A from becoming too thick overall or the processability of the blank substrate 2A being reduced.

[0088] The ratio (Hk / Hh) of the thickness Hk of the absorption layer 40 to the thickness Hh of the coating layer 80 is preferably 3 or more, 5 or more, and may be 10 or more. Furthermore, the ratio (Hk / Hh) is preferably 80 or less, 75 or less, and may be 70 or less. In addition, the ratio (Hk / Hh) may be determined by any combination of any one of the above-mentioned lower limit candidate values ​​and any one of the above-mentioned upper limit candidate values. Specifically, for example, the ratio (Hk / Hh) is preferably 3 or more and 80 or less, 5 or more and 75 or less, and may be 10 or more and 70 or less. This tends to make it easier to protect the absorption layer 40 while suppressing a decrease in EUV absorption efficiency.

[0089] The ratio (Hh / Ho) of the thickness of the coating layer 80 to the thickness of the oxide layer 70 Ho is preferably 1 or more, 3 or more, or 5 or more. Furthermore, the ratio (Hh / Ho) is preferably 30 or less, 25 or less, or 20 or less. In addition, the ratio (Hh / Ho) may be determined by any combination of any one of the above-mentioned lower limit candidate values ​​and any one of the above-mentioned upper limit candidate values. Specifically, for example, the ratio (Hh / Ho) is preferably 1 to 30, 3 to 25, or 5 to 20. This tends to achieve a balance between suppressing migration of the absorption layer 40 material, protecting the absorption layer 40, and preventing the overall thickness of the blank substrate 2A from becoming too large.

[0090] 1.8. Top coat layer The topcoat layer 90 may constitute the surface of the blank substrate 2A opposite to the substrate 10. For example, the topcoat layer 90 may be located above the stacking direction D3 of the absorption layer 40, or above the stacking direction D3 of the coating layer 80. That is, the topcoat layer 90 may be located on the opposite side of the coating layer 80 from the substrate 10. The topcoat layer 90 is a layer intended to protect the blank substrate 2A and the entire reflective mask 1 manufactured from the blank substrate 2A from oxidation, contamination, and damage during cleaning.

[0091] The material for the topcoat layer 90 is preferably a metal such as Ru, Ta, W, Nb, Pt, Rh, Re, Cr, or Ti; an oxide such as SiO2; or a carbon-based material such as diamond-like carbon or B4C. Among these, metals are preferred, and Ru is more preferred. The metal contained in the topcoat layer 90 is also called the third metal, in distinction from the first and second metals. The material for the topcoat layer 90 may be used alone or two or more materials may be used in combination.

[0092] The thickness of the top coat layer 90 is preferably 2 nm or more, 3 nm or more, or 4 nm or more. Alternatively, the thickness of the top coat layer 90 is preferably 15 nm or less, 14 nm or less, or 13 nm or less. Furthermore, the thickness of the top coat layer 90 may be determined by any combination of any one of the above-mentioned lower limit candidate values ​​and any one of the above-mentioned upper limit candidate values. Specifically, for example, the thickness of the top coat layer 90 is preferably 2 nm or more and 15 nm or less, 3 nm or more and 14 nm or less, or 4 nm or more and 13 nm or less. This tends to provide better protection for the blank substrate 2A and the entire reflective mask 1 manufactured from the blank substrate 2A from oxidation, contamination, and damage during cleaning.

[0093] Figure 1B is another example of a cross-sectional view of a blank substrate of the present disclosure. As shown in Figure 1B, the blank substrate 2B of the present disclosure may include a second absorption layer 100 on the upper side of the coating layer 80 in the lamination direction D3.

[0094] 1.9. Second absorption layer The second absorption layer 100 may be located above the absorption layer 40 in the stacking direction D3, or above the coating layer 80 in the stacking direction D3. That is, the second absorption layer 100 may be located on the opposite side of the coating layer 80 from the substrate 10. The second absorption layer 100 has the function of complementing the EUV absorption of the absorption layer 40, and further improves the EUV absorption in the absorption region of the reflective mask 1 manufactured from the blank substrate 2B.

[0095] Furthermore, if the blank substrate 2B includes a second absorption layer 100, the aforementioned absorption layer 40 may be referred to as the first absorption layer 40.

[0096] Preferably, the material for the second absorption layer 100 is a metal such as Ru, Ta, W, Nb, Pt, Rh, Re, Cr, or Ti, with Ru being the most preferred among these. Since these metals are also suitable as materials for the topcoat layer 90, the second absorption layer 100 containing these metals can be said to also function as the topcoat layer 90. Furthermore, by using the same material as the first absorption layer 40 as the material for the second absorption layer 100, the absorption of EUV can be further improved. In addition, a phase shift effect with respect to EUV can be introduced to improve the exposure margin and resolution during transfer, the reflectivity of EUV can be suppressed to improve contrast, and the reflectivity of inspection light (light with wavelengths ranging from UV to visible light) can be suppressed to improve inspection sensitivity.

[0097] The metal contained in the second absorption layer 100 is also referred to as the third metal, to distinguish it from the first and second metals. The material for the second absorption layer 100 may be a single material or two or more materials may be used in combination. The third metal may be the same as at least one of the first and second metals, the same as both the first and second metals, or different from both the first and second metals.

[0098] The thickness of the second absorption layer 100 is preferably 15 nm or more, 20 nm or more, or 25 nm or more. Alternatively, the thickness of the second absorption layer 100 is preferably 50 nm or less, 45 nm or less, or 40 nm or less. Furthermore, the thickness of the second absorption layer 100 may be determined by any combination of any one of the above-mentioned lower limit candidate values ​​and any one of the above-mentioned upper limit candidate values. Specifically, for example, the thickness of the second absorption layer 100 is preferably 15 nm or more and 50 nm or less, 20 nm or more and 45 nm or less, or 25 nm or more and 40 nm or less. This improves the EUV absorption while preventing the blank substrate 2B from becoming too thick overall.

[0099] Furthermore, if the topcoat layer 90 and the second absorption layer 100 are composed of the same material, they may perform both functions. That is, a layer on the first absorption layer 40 may serve both a complementary function for EUV absorption to the absorption layer 40 (second absorption layer 100) and a protective function on the top surface of the mask (topcoat layer 90). By providing such a layer, it is possible to provide a phase shift effect with respect to EUV, improve exposure margin and resolution during transfer, suppress EUV reflectivity to improve contrast, and suppress the reflectivity of inspection light (light with wavelengths ranging from UV to visible light) to improve inspection sensitivity.

[0100] Furthermore, if the topcoat layer 90 and the second absorption layer 100 are composed of different materials, the blank substrate 2 may have both the topcoat layer 90 and the second absorption layer 100 separately. In this case, the topcoat layer 90, which is responsible for the protective function of the reflective mask, is located on the outermost layer (top surface), and the second absorption layer 100 is located between the first absorption layer 40 and the topcoat layer 90. This allows for adjustment of EUV absorption in the absorption region while protecting the top surface of the mask from oxidation, contamination, and damage during cleaning.

[0101] Furthermore, when a topcoat layer 90 containing a third metal (such as Ru) or a second absorption layer 100 is provided on the upper side of the absorption layer 40 in the lamination direction D3, the second metal and the third metal may be in contact at the interface between the first absorption layer 40 and these layers. In this case, a mixed layer containing the second metal and the third metal may be formed at that interface. This improves the adhesion between the first absorption layer 40 and the topcoat layer 90 or the second absorption layer 100, allowing the protective or absorption function of the upper metal layer to be stably exhibited.

[0102] When the blank substrates 2A and 2B of this disclosure are not distinguished, they are simply referred to as blank substrate 2.

[0103] 2. Reflective mask The reflective mask of this disclosure is manufactured from the blank substrate 2 of this disclosure. Figure 2A is an example of a plan view of the reflective mask of this disclosure as seen from the absorption layer side, Figure 2B is an example of a plan view of the reflective mask 1A of this disclosure as seen from the substrate side, and Figure 2C is an example of a cross-sectional view along line AA in Figure 2A.

[0104] As shown in Figures 2A to 2C, the reflective mask (hereinafter also simply referred to as "mask") 1A comprises a substrate 10, a reflective layer 20, a cap layer 30 containing a first metal, an oxide layer 70, and an absorption layer 40 containing a second metal, laminated in at least this order. The oxide layer 70 contains oxides of the first metal and / or the second metal. The mask 1 has a first surface 1a on the side of the absorption layer 40 and a second surface 1b on the side of the substrate 10. The first surface 1a is the surface to which EUV light is incident and has a mask pattern region 10a on which a desired pattern is formed. The mask pattern region 10a also includes an absorption region 10a1 where the absorption layer 40 is present and a reflective region 10a2 where the absorption layer 40 is not present. The second surface 1b is the surface opposite to the first surface 1a. The reflective mask 1A may have a conductive layer 60 on the second surface 1b side.

[0105] This reflective mask 1A is used, for example, in EUV lithography in the manufacturing process of semiconductor devices. In the exposure step of EUV lithography, as shown in Figure 4, EUV light emitted from the exposure apparatus is incident on the first surface 1a of the reflective mask 1A via multiple reflectors and is reflected by the reflective layer 20. At this time, EUV light incident on the region where the absorption layer 40 is present is absorbed by the absorption layer 40 and reflection is suppressed, and only EUV light incident on the region where the absorption layer 40 is absent is selectively reflected by the reflective layer 20. In this way, the reflection region of EUV light is selected according to the pattern formed by the absorption layer 40, and the desired circuit pattern is precisely transferred to the wafer.

[0106] In the reflective mask 1A of this disclosure, since the oxide layer 70 is located between the cap layer 30 and the absorption layer 40, the metal contained in the absorption layer 40 is less likely to migrate to each layer (e.g., the cap layer 30) located below the absorption layer 40 in the stacking direction D3. This suppresses the inclusion of components of the absorption layer 40 in the cap layer 30 located in the reflective region 10a2 in a plan view, thereby suppressing a decrease in EUV reflectivity in the reflective region 10a2.

[0107] In a plan view of the first surface 1a, the reflective mask 1A has a mask pattern region 10a, and may also have a recessed region 10b and / or an outer edge region 10c.

[0108] The mask pattern region 10a is a region in which the absorption layer 40 is selectively patterned according to a desired circuit pattern to be transferred to the wafer. The desired pattern is formed on the wafer by EUV light selectively reflected in the mask pattern region 10a. As shown in Figure 2C, the mask pattern region 10a includes an absorption region 10a1 in which the absorption layer 40 is present and a reflection region 10a2 in which the absorption layer 40 is absent.

[0109] An absorption layer 40 is located in the absorption region 10a1 and absorbs EUV light. Here, the absorption layer 40 is patterned based on a desired circuit pattern to be formed on the wafer and has the function of selectively absorbing EUV light in a predetermined region. As a result, reflection of EUV light is suppressed in the absorption region 10a1, and in the reflection region 10a2, EUV light is selectively reflected by the reflection layer 20. With this configuration, it becomes possible to transfer the pattern formed on the absorption layer 40 to the wafer to be exposed with high precision.

[0110] In the reflection region 10a2, it is preferable that the oxide layer 70 is absent and the cap layer 30 is exposed. This tends to improve the EUV reflection efficiency in the reflection region 10a2.

[0111] In the reflection region 10a2, it is preferable that there are no or very few Ta elements that readily absorb EUV. From this viewpoint, it is preferable that the Ta peak intensity in the X-ray absorption fine structure spectrum of the reflection region 10a2 is 1 / 50 or less, more preferably 1 / 60 or less, and even more preferably 1 / 70 or less, of the Ta peak intensity in the X-ray absorption fine structure spectrum of the absorption region 10a1.

[0112] In this disclosure, the X-ray absorption fine structure spectrum is specifically measured under the following conditions, and the spectrum shown in Figure 2K is obtained. Specifically, the upper spectrum in Figure 2K is a schematic diagram of the X-ray absorption fine structure spectrum of the absorption region 10a1, and the lower spectrum in Figure 2K is a schematic diagram of the X-ray absorption fine structure spectrum of the reflection region 10a2. • Facility name: 3GeV High-Brightness Synchrotron Radiation Facility NanoTerasu • Beam size: 800 μm x 400 μm • Angle of incidence on the sample: 45° (0° is defined as the direction perpendicular to the sample) • Measurement method: Partial fluorescence yield method

[0113] Of the spectra obtained from the measurements described above, the maximum value of the peak in the energy range of 9781 to 10018 eV, corresponding to the Ta L3-edge, is defined as the Ta peak intensity. The Ta peak intensity ratio refers to the ratio of the Ta peak intensities (reflection region peak intensity / absorption region peak intensity) in the X-ray absorption fine structure spectra of each Ta L3-edge obtained under the same measurement conditions for the absorption region 10a1 and reflection region 10a2 of the same sample. When measuring different regions of the same sample under the same light source conditions, detector conditions, incident angle conditions, etc., factors that commonly affect the measurement, such as the absolute sensitivity of the instrument, fluctuations in light source intensity, detector gain, and monochromator settings, are canceled out by taking the ratio. Therefore, the Ta peak intensity ratio serves as an indicator that reflects the difference in the abundance of Ta.

[0114] Alternatively, the concentration of Ta in the cap layer 30 in the reflective region 10a2 is preferably 1000 ppm or less, more preferably 900 ppm or less, and even more preferably 800 ppm or less.

[0115] Furthermore, since the detection limit in X-ray absorption fine structure analysis is approximately a few ppm to 10 ppm, if the Ta peak intensity in the reflection region 10a2 is 1 / 50 or less of the Ta peak intensity in the absorption region 10a1 where Ta elements are abundant, then the concentration of Ta in the reflection region 10a2 can be said to be 1000 ppm or less. In other words, if the Ta peak intensity in the reflection region 10a2 is 1 / 50 or less of the Ta peak intensity in the absorption region 10a1, then the concentration of Ta in the cap layer 30 exposed in the reflection region 10a2 can be said to be 1000 ppm or less.

[0116] The mask 1A of this disclosure is fabricated from the blank substrate 2 described above. Specifically, in the blank substrate 2, an oxide layer 70 is placed between the absorption layer 40 and the cap layer 30, thereby suppressing the migration of Ta from the absorption layer 40 to the cap layer 30. Therefore, in the reflection region 10a2 of the mask 1A of this disclosure fabricated from the blank substrate 2 described above, the amount of Ta element present is reduced or almost nonexistent.

[0117] There are no particular limitations on the method for adjusting the amount of Ta element in the reflection region 10a2. For example, by forming a thicker oxide layer 70 on the blank substrate 2, the migration of Ta from the absorption layer 40 to the cap layer 30 can be further suppressed, thereby reducing the amount of Ta element in the reflection region 10a2. That is, by forming a thicker oxide layer 70 on the blank substrate 2, the Ta peak intensity in the X-ray absorption fine structure spectrum of the reflection region 10a2 can be reduced relative to the Ta peak intensity in the X-ray absorption fine structure spectrum of the absorption region 10a1, thereby reducing the concentration of Ta in the cap layer 30 in the reflection region 10a2.

[0118] In this disclosure, the apparatus for performing X-ray absorption fine structure analysis is not particularly limited, but it may be the "3GeV High-Brightness Synchrotron Radiation Facility NanoTerasu," which enables high-sensitivity detection.

[0119] The etched region 10b is located around the mask pattern region 10a and is an area where the reflective layer 20 is not located. For example, the etched region 10b can be formed by etching from the absorption layer 40 side up to the substrate 10. In this case, the substrate 10 may be exposed in the etched region 10b. The etched region 10b may also be an area where the alignment marks used to form the desired pattern in the mask pattern region 10a and their surroundings have been removed. Since EUV light is not reflected in this region, it can function as a light-shielding region that suppresses the reflection and irradiation of light onto the wafer.

[0120] The recessed area 10b may be positioned to continuously surround the mask pattern area 10a, for example, as shown in Figure 2A. By arranging the recessed area 10b to surround the mask pattern area 10a, for example in a frame shape, the function as a light-shielding area is improved.

[0121] The outer edge region 10c is an area positioned on the outer perimeter of the mask so as to surround the mask pattern region 10a and the recessed region 10b, as shown in Figures 2A and 2C. This outer edge region 10c may include reticle alignment marks, barcodes, characters / symbols, various evaluation patterns, etc.

[0122] Figure 2D shows an enlarged view of the area enclosed by the dashed line in Figure 2C, i.e., an enlarged cross-sectional view of the vicinity of the absorption layer 40 in the mask pattern region 10a. As shown in Figure 2D, in cross-sectional view, the laminate including the absorption layer 40 and the oxide layer 70 in the absorption region 10a1 may have a tapered shape that widens from the absorption layer 40 side toward the boundary between the oxide layer 70 and the cap layer 30.

[0123] Furthermore, the side surface of the tapered laminate may have a straight portion and a curved portion connected to the straight portion, and the curved portion may be located between the straight portion and the boundary between the oxide layer 70 and the cap layer 30.

[0124] The height Hv from the boundary to the connection point V between the straight section and the curved section is preferably 0.1 nm or more, 0.2 nm or more, or 0.3 nm or more. Furthermore, the height Hv is preferably 15.0 nm or less, 12.5 nm or less, or 10.0 nm or less. In addition, the height Hv may be determined by a combination of any one of the above-mentioned lower limit candidate values ​​and any one of the above-mentioned upper limit candidate values. Specifically, for example, the height Hv is preferably 0.1 nm or more and 15.0 nm or less, 0.2 nm or more and 12.5 nm or less, or 0.3 nm or more and 10.0 nm or less. This allows for the formation of a continuous structure from the absorption layer 40 side to the cap layer 30 side while widening the boundary area between the oxide layer 70 and the cap layer 30, and tends to suppress peeling of the absorption layer 40. It also tends to suppress the occurrence of shadows caused by the shape of the absorption layer 40 when using the reflective mask 1A. Shadow refers to the phenomenon where, when EUV is incident from an oblique direction, shifted from the direction perpendicular to the in-plane direction of the reflective mask 1A, the reflected EUV is absorbed by the absorption layer 40, resulting in the wafer not being irradiated as intended.

[0125] In a plan view, the distance W1 between the connection portion V and the end portion Po of the laminate at the boundary (i.e., the distance W1 between the connection portion V and the end portion Po in the in-plane direction) is preferably 1.0 nm or more, 1.1 nm or more, or 1.2 nm or more. Furthermore, the distance W1 is preferably 5.2 nm or less, 5.1 nm or less, or 5.0 nm or less. In addition, the distance W1 may be determined by any combination of any one of the above-mentioned lower limit candidate values ​​and any one of the above-mentioned upper limit candidate values. Specifically, for example, the distance W1 is preferably 1.0 nm or more and 5.2 nm or less, 1.1 nm or more and 5.1 nm or less, or 1.2 nm or more and 5.0 nm or less. This allows for the formation of a continuous structure from the absorption layer 40 side to the cap layer 30 side while widening the boundary area between the oxide layer 70 and the cap layer 30, and tends to suppress peeling of the absorption layer 40. Furthermore, when using the reflective mask 1A, it tends to suppress the occurrence of shadows caused by the shape of the absorption layer 40. Note that, as shown in Figure 2D, distance W1 refers to the distance between the connection part V and the end part Po on the same side with respect to the central axis parallel to the D3 direction of the absorption layer 40 in any cross section perpendicular to the in-plane direction.

[0126] In a plan view, the distance W2 between the end Pj of the upper surface of the tapered laminate and the end Po of the laminate at the boundary (i.e., the distance W2 between end Pj and end Po in the in-plane direction) is preferably 1.0 nm or more, 1.1 nm or more, or 1.2 nm or more. Furthermore, the distance W2 is preferably 6.0 nm or less, 5.9 nm or less, or 5.8 nm or less. Additionally, the distance W2 may be determined by any combination of any one of the above-mentioned lower limit candidate values ​​and any one of the above-mentioned upper limit candidate values. Specifically, for example, the distance W2 is preferably 1.0 nm or more and 6.0 nm or less, 1.1 nm or more and 5.9 nm or less, or 1.2 nm or more and 5.8 nm or less. This allows for the formation of a continuous structure from the absorption layer 40 side toward the cap layer 30 side, while widening the boundary area between the oxide layer 70 and the cap layer 30, and tends to suppress peeling of the absorption layer 40. Furthermore, when using the reflective mask 1A, it tends to suppress the occurrence of shadows caused by the shape of the absorption layer 40. Note that, as shown in Figure 2D, distance W2 refers to the distance between end Pj and end Po on the same side with respect to the central axis parallel to the D3 direction of the absorption layer 40 in any cross section perpendicular to the in-plane direction.

[0127] Figure 2E shows another example of an enlarged cross-sectional view near the absorption layer 40 in the mask pattern region 10a. As shown in Figure 2E, in cross-sectional view, the laminate including the absorption layer 40 and the oxide layer 70 in the absorption region 10a1 may have a shape in which the width narrows from the side of the absorption layer 40 toward the boundary between the oxide layer 70 and the cap layer 30. Specifically in Figure 2E, the entire oxide layer 70 and a portion of the lower side of the absorption layer 40 in the stacking direction D3 are shown to have a shape in which the width narrows from the upper side of the stacking direction D3 of the laminate including the absorption layer 40 and the oxide layer 70 toward the boundary between the oxide layer 70 and the cap layer 30. However, the "shape in which the width narrows from the side of the absorption layer 40 toward the boundary between the oxide layer 70 and the cap layer 30" is not limited to this. For example, the entire oxide layer 70 may have a shape that narrows in width towards the boundary between the oxide layer 70 and the cap layer 30, or the absorption layer 40 may have a shape that widens in width from the upper side to the lower side in the stacking direction D3, and the oxide layer 70 may have a shape that widens in width from the boundary between the absorption layer 40 and the oxide layer 70 toward the lower side in the stacking direction D3 up to a certain point in the oxide layer 70, and then narrows in width from that point toward the lower side in the stacking direction D3 up to the boundary between the oxide layer 70 and the cap layer 30. In other words, the oxide layer 70 may have a bulging portion that widens in width when viewed in cross-section.

[0128] The laminate containing the absorption layer 40 and the oxide layer 70 has the shape shown in Figure 2E, which tends to suppress the occurrence of shadows caused by the shape of the laminate. For example, even when the incident angle of EUV is 6°, the occurrence of shadows tends to be suppressed.

[0129] Furthermore, the upper side of the laminate including the absorption layer 40 and the oxide layer 70 shown in Figure 2E, in the stacking direction D3, can be said to have a tapered shape in cross-sectional view, widening from the absorption layer 40 side towards the boundary between the oxide layer 70 and the cap layer 30.

[0130] Furthermore, regarding the preferred structure of the absorption layer 40 in the mask pattern region 10a described above, it is preferable that at least a portion of the absorption layer 40 has the said structure.

[0131] The specific details of each component that the reflective mask 1A may have, namely the substrate 10, reflective layer 20, cap layer 30, absorption layer 40, conductive layer 60, and oxide layer 70, are as described in detail in the blank substrate 2.

[0132] 2.1. Pellicle The reflective mask of this disclosure may have a pellicle on the first surface 1a side, although this is not shown. If foreign matter adheres to the first surface of the reflective mask, the reflection of EUV light may become unintended due to the foreign matter, which may prevent the formation of an accurate circuit pattern on the wafer. In this regard, by having a pellicle in the reflective mask of this disclosure, foreign matter is more likely to adhere to the surface of the pellicle instead of the first surface 1a, thereby suppressing the formation of an unintended circuit pattern on the wafer due to the foreign matter.

[0133] The pellicle is preferably located above the stacking direction D3 of the absorption layer 40 and not in contact with the first surface 1a. The pellicle may also be supported by columns located outside the mask pattern region 10a (for example, the outer edge region 10c).

[0134] The pellicle material is not particularly limited, but examples include carbon nanotubes, silicon oxide films, silicon nitride films, and boron-based films containing boron. One type of pellicle material may be used alone, or two or more types may be used in combination.

[0135] The pellicle thickness is not particularly limited, but may be, for example, 50 nm or more and 100 nm or less.

[0136] 2.2.Coating layer Figure 2F is another example of a cross-sectional view of the reflective mask of the present disclosure. As shown in Figure 2F, in the reflective mask 1B of the present disclosure, the upper surface 40a of the absorption layer 40 of the absorption region 10a1 may be covered with a coating layer 80 containing an oxide of the second metal, and the upper surface 40a and side surface 40b of the absorption layer 40 of the absorption region 10a1 may be covered with a coating layer 80 containing an oxide of the second metal. This makes it easier to protect the absorption layer 40 from oxidation, contamination, and damage during cleaning.

[0137] Furthermore, it is preferable that the coating layer 80 covering the upper surface 40a of the absorption layer 40 and the coating layer 80 covering the side surface 40b contain the same components. This improves the continuity of the coating layer 80, making it less likely for the coating layer 80 to peel off from the absorption layer 40, and tends to improve washing resistance.

[0138] Furthermore, the oxide layer 70 preferably contains an oxide of the second metal, and preferably contains the same components as the coating layer 80 that covers the upper surface 40a and side surface 40b of the absorption layer 40. That is, it is preferable that the upper surface 40a, side surface 40b, and lower surface of the absorption layer 40 are covered with the same oxide of the second metal. This improves the continuity of the coating layer 80, making it less likely for the coating layer 80 to peel off from the absorption layer 40, and tends to improve cleaning resistance. It also tends to suppress changes in the shape of the absorption layer 40. In addition, by reducing the difference in thermal expansion coefficients within the coating layer 80, it tends to suppress stress concentration at specific locations in the coating layer 80, thereby suppressing defects such as peeling. Moreover, when the absorption layer 40 has a coating layer 80 on its side surface 40b, the coating layer 80 and the oxide layer 70 can be continuously connected, thereby suppressing an increase in the brittleness of the oxide film and tending to prevent an increase in the roughness of the pattern edge in a plan view.

[0139] The coating layer 80 preferably contains an oxide of Ta. Furthermore, the coating layer 80 preferably contains an oxide of the same second metal as the absorption layer 40. The coating layer 80 may be made of one material alone, or two or more materials may be used in combination.

[0140] The thickness Hh of the coating layer 80 is preferably 1.0 nm or more, 1.5 nm or more, or 2.0 nm or more. Furthermore, the thickness Hh of the coating layer 80 is preferably 8.0 nm or less, 7.5 nm or less, or 7.0 nm or less. In addition, the thickness Hh of the coating layer 80 may be determined by any combination of any one of the above-mentioned lower limit candidate values ​​and any one of the above-mentioned upper limit candidate values. Specifically, for example, the thickness Hh of the coating layer 80 is preferably 1.0 nm or more and 8.0 nm or less, 1.5 nm or more and 7.5 nm or less, or 2.0 nm or more and 7.0 nm or less. This makes it easier to protect the absorption layer 40 while preventing the blank substrate 2 as a whole from becoming too thick.

[0141] Figure 2I shows another example of an enlarged cross-sectional view near the absorption layer 40 in the mask pattern region 10a. As shown in Figure 2I, in a cross-sectional view, if the laminate including the absorption layer 40 and the oxide layer 70 in the absorption region 10a1 has a tapered shape that widens from the absorption layer 40 towards the boundary between the oxide layer 70 and the cap layer 30, the coating layer 80 may be positioned along its periphery. That is, in a cross-sectional view, the laminate including the absorption layer 40, the oxide layer 70 and the coating layer 80 in the absorption region 10a1 may have a tapered shape that widens from the absorption layer 40 towards the boundary between the oxide layer 70 and the cap layer 30.

[0142] Figure 2J shows another example of an enlarged cross-sectional view near the absorption layer 40 in the mask pattern region 10a. As shown in Figure 2J, in a cross-sectional view, if the laminate in the absorption region 10a1, including the absorption layer 40 and the oxide layer 70, has a shape in which the width narrows from the absorption layer 40 towards the boundary between the oxide layer 70 and the cap layer 30, the coating layer 80 may be positioned along its periphery. That is, in a cross-sectional view, the laminate in the absorption region 10a1, including the absorption layer 40, the oxide layer 70, and the coating layer 80, may have a shape in which the width narrows from the absorption layer 40 towards the boundary between the oxide layer 70 and the cap layer 30.

[0143] For example, if the taper is small, as shown in Figure 2F, the coating layer 80 may be located above the oxide layer 70 in the stacking direction D3, and the coating layer 80 may not be in contact with the cap layer 30. On the other hand, if the taper is large, as shown in Figures 2I and 2J, the thickness of the absorption layer 40 at the tapered end is thin, so the oxidation treatment promotes modification to the oxide layer 70, and it becomes closer in quality to the coating layer 80 covering the side surface 40b, and the coating layer 80 may come into contact with the cap layer 30. In addition, when the surface of the absorption layer 40 oxidizes and changes into the coating layer 80, volume changes and shape changes occur, and the coating layer 80 may come into contact with the cap layer 30.

[0144] 2.3. Top coat layer Figure 2G is another example of a cross-sectional view of the reflective mask of the present disclosure. As shown in Figure 2G, the reflective mask 1C of the present disclosure may include a topcoat layer 90 containing a third metal on the side of the coating layer 80 opposite to the substrate 10. The topcoat layer 90 is located above the absorption layer 40 in the lamination direction D3 in the absorption region 10a1 and protects the entire reflective mask 1 from oxidation, contamination, and damage during cleaning. Furthermore, from the viewpoint of suppressing a decrease in EUV reflectivity, it is preferable that the topcoat layer 90 is not located in the reflective region 10a2 in a plan view.

[0145] The material for the top coat layer 90 is preferably a metal such as Ru, Ta, W, Nb, Pt, Rh, Re, Cr, or Ti; an oxide such as SiO2; or a carbon-based material such as diamond-like carbon or B4C. Among these, a third metal containing one or more selected from the group consisting of Ru, Ta, W, Nb, Pt, Rh, Re, Cr, and Ti is preferred, with Ru being more preferred. The material for the top coat layer 90 may be used alone or two or more in combination.

[0146] The thickness of the topcoat layer 90 is preferably 2 nm or more, 5 nm or more, or 10 nm or more. Alternatively, the thickness of the topcoat layer 90 is preferably 75 nm or less, 70 nm or less, or 65 nm or less. Furthermore, the thickness of the topcoat layer 90 may be determined by any combination of any one of the above-mentioned lower limit candidate values ​​and any one of the above-mentioned upper limit candidate values. Specifically, for example, the thickness of the topcoat layer 90 is preferably 2 nm to 75 nm, 5 nm to 70 nm, or 10 nm to 65 nm. This tends to provide better protection for the entire reflective mask 1 from oxidation, contamination, and damage during cleaning.

[0147] 2.4. Second absorption layer Figure 2H is another example of a cross-sectional view of the reflective mask of the present disclosure. As shown in Figure 2H, the reflective mask 1D of the present disclosure may include a second absorption layer 100 containing a third metal on the side of the coating layer 80 opposite to the substrate 10. The second absorption layer 100 has the function of complementing the EUV absorption of the absorption layer 40 and further improves the EUV absorption in the absorption region of the reflective mask 1 manufactured from the blank substrate 2. Furthermore, from the viewpoint of suppressing a decrease in EUV reflectivity, it is preferable that the second absorption layer 100 is not located in the reflective region 10a2 in a plan view.

[0148] Furthermore, if the reflective mask 1 includes a second absorption layer 100, the aforementioned absorption layer 40 may be referred to as the first absorption layer 40.

[0149] Preferably, the material for the second absorption layer 100 is a metal such as Ru, Ta, W, Nb, Pt, Rh, Re, Cr, or Ti, with Ru being the most preferred among these. Since these metals are also suitable as materials for the topcoat layer 90, the second absorption layer 100 can also function as the topcoat layer 90. Furthermore, by using the same material for the second absorption layer 100 as for the first absorption layer 40, the EUV absorption can be further improved. The material for the second absorption layer 100 may be used alone or in combination of two or more materials.

[0150] The thickness of the second absorption layer 100 is preferably 15 nm or more, 20 nm or more, or 25 nm or more. Alternatively, the thickness of the second absorption layer 100 is preferably 75 nm or less, 70 nm or less, or 65 nm or less. Furthermore, the thickness of the second absorption layer 100 may be determined by any combination of any one of the above-mentioned lower limit candidate values ​​and any one of the above-mentioned upper limit candidate values. Specifically, for example, the thickness of the second absorption layer 100 is preferably 15 nm or more and 75 nm or less, 20 nm or more and 70 nm or less, or 25 nm or more and 65 nm or less. This makes it possible to improve the absorption of EUV while suppressing the overall thickness of the reflective mask 1.

[0151] Furthermore, in embodiments where a topcoat layer 90 or a second absorption layer 100 is provided, the coating layer 80 on the first absorption layer 40 (second metal) may be formed on the side surfaces of the first absorption layer 40 and at the interface between the first absorption layer 40 and the topcoat layer 90 or the second absorption layer 100 (see Figures 2G and 2H). On the other hand, the coating layer 80 does not need to be formed on the side surfaces of the topcoat layer 90 or the second absorption layer 100. In this configuration, the coating layer 80 is formed on the side surfaces 40b and the top surface 40a of the absorption layer 40, thereby ensuring the cleaning resistance and dimensional stability of the absorption layer 40 while suppressing migration at the interface between the absorption layer 40 and the topcoat layer 90 or the second absorption layer 100.

[0152] When the reflective masks 1A, 1B, 1C, and 1D of this disclosure are not distinguished, they are simply referred to as reflective mask 1.

[0153] 3. Method for manufacturing a reflective mask The present disclosure provides a method for manufacturing a reflective mask, comprising stacking a substrate, a reflective layer, a cap layer containing a first metal, an oxide layer, and an absorption layer containing a second metal in at least this order, wherein the oxide layer contains an oxide of the first metal and / or the second metal, comprising a preparation step of preparing a blank substrate, a film formation step of forming a resist layer on the absorption layer of the blank substrate, a resist pattern formation step of forming a resist pattern on the resist layer by performing electron beam or laser light writing and development processing, and a mask pattern formation step of forming a mask pattern region including an absorption region where the absorption layer exists and a reflective region where the absorption layer does not exist by selectively etching the region of the absorption layer where the resist pattern does not exist, wherein the mask pattern formation step comprises an oxide layer removal step of removing the oxide layer in the reflective region.

[0154] The following describes in detail each step that the manufacturing method of the reflective mask described herein may include, with reference to Figures 3A to 3Q.

[0155] 3.1. Preparation process In the preparation process of this disclosure, as shown in Figure 3A, a blank substrate 2 is prepared, comprising a base material 10, a reflective layer 20, a cap layer 30 containing a first metal, an oxide layer 70, and an absorption layer 40 containing a second metal, stacked in at least this order. A reflective mask 1 can be manufactured by etching or the like on the blank substrate 2.

[0156] The blank substrate 2 may have a hard mask H on the side of the absorption layer 40 opposite to the substrate 10. Alternatively, the blank substrate 2 may have a conductive layer 60 on the side of the substrate 10 opposite to the absorption layer 40.

[0157] The material for the hard mask H is not particularly limited, but examples include Cr, Zr, and Hf, as well as their nitrides and oxides. One material may be used alone for the hard mask H, or two or more materials may be used in combination. The thickness of the hard mask H is not particularly limited, but for example, it may be between 5 nm and 15 nm.

[0158] The blank substrate 2 may be prepared by purchasing a commercially available product, or by manufacturing it using a sputtering method or the like. When manufacturing the blank substrate 2, it may be manufactured as follows.

[0159] First, a reflective layer 20 is formed on the substrate 10. When the reflective layer 20 is a Mo / Si periodic multilayer film, the method for forming the reflective layer 20 is not particularly limited, but examples include ion beam sputtering and magnetron sputtering, using Mo and Si as sputtering targets. The deposition atmosphere is not particularly limited, but examples include an argon atmosphere.

[0160] Next, a cap layer 30, an oxide layer 70, and an absorption layer 40 are formed on the reflective layer 20 in this order. Then, a hard mask H is formed on the absorption layer 40. The method for forming the cap layer 30, oxide layer 70, absorption layer 40, and hard mask H is not particularly limited, but examples include ion beam sputtering and magnetron sputtering. The deposition atmosphere is not particularly limited, but examples include argon atmosphere, nitrogen atmosphere, and oxygen atmosphere. For example, when depositing an oxide film, an oxygen atmosphere may be selected, when depositing a nitride film, a nitrogen atmosphere may be selected, and when depositing the target material as is, an argon atmosphere may be selected. Note that the nitrogen atmosphere and oxygen atmosphere mean an atmosphere containing nitrogen and an atmosphere containing oxygen, respectively, and may contain gases other than nitrogen and oxygen. For example, the nitrogen atmosphere may be a mixed atmosphere of nitrogen and argon, and the oxygen atmosphere may be a mixed atmosphere of oxygen and argon.

[0161] In preparing the blank substrate 2, the coating layer 80 and the absorption layer 40 may be formed such that the ratio of the thickness Hk of the absorption layer 40 to the thickness Hh of the coating layer 80 (Hk / Hh) is between 3 and 80.

[0162] The oxide layer 70 may be formed by sputtering, or by subjecting the surface of the cap layer 30 to an oxidation treatment such as heating in an oxygen atmosphere or oxygen plasma treatment.

[0163] In other words, the method for manufacturing a blank substrate of the present disclosure, comprising a substrate, a reflective layer, a cap layer containing a first metal, an oxide layer, and an absorption layer containing a second metal, laminated in at least this order, wherein the oxide layer contains an oxide of the first metal and / or the second metal, may include an oxide layer formation step of forming the oxide layer on the cap layer by sputtering or by oxidizing the surface of the cap layer.

[0164] After forming the absorption layer 40, alignment marks may be formed on the absorption layer 40. Positional information of the alignment marks can be obtained by scanning the alignment marks with an electron beam or laser light. Based on the positional information of the alignment marks obtained in this way, a mask pattern is formed in the mask pattern formation process described later.

[0165] 3.2.First film formation process In the film deposition process of this disclosure, a resist layer R is deposited on a blank substrate 2 as shown in Figure 3B.

[0166] The method for forming the resist layer R is not particularly limited, but examples include spin coating, spray coating, dip coating, slot die coating, inkjet coating, blade coating, and vapor phase deposition. Among these, spin coating is preferred. Furthermore, after forming the resist layer R, the resist layer R may be subjected to a bake treatment.

[0167] The resist layer R may contain positive-type resists or negative-type resists. Examples of such resist materials are not particularly limited, but include chemically amplified resists (CAR) and radioactively decomposed positive-type ZEP resists (manufactured by Zeon Corporation). The thickness of the resist layer R is not particularly limited, but may be, for example, 30 nm to 600 nm.

[0168] Furthermore, if a resist layer is formed after the first absorption layer oxidation process described later, this process may be referred to as the first film formation process and distinguished from the film formation process after the first absorption layer oxidation process. On the other hand, if there is no need to distinguish this process from the film formation process after the first absorption layer oxidation process, this process may simply be called the "film formation process."

[0169] 3.3. First resist pattern formation process In the first resist pattern formation step of this disclosure, electron beam or laser light drawing and development processing are performed based on the positional information of alignment marks obtained by scanning to form a resist pattern RP for forming a mask pattern region 10a on the resist layer R, as shown in Figure 3C.

[0170] More specifically, in this process, for example, first, the coordinate system on the mask substrate and the drawing pattern data are precisely aligned based on the position information of the alignment marks. Then, based on the drawing pattern data, the resist layer R is irradiated with an electron beam or laser light to perform electron beam or laser light drawing and pattern the resist layer R into the desired shape. If the resist layer R is a positive-type resist, the exposed areas are removed in the subsequent development process, and the hard mask H is exposed in those areas. If the resist layer R is a negative-type resist, the unexposed areas are removed in the subsequent development process, and the hard mask H is exposed in those areas.

[0171] Next, the exposed resist layer R is developed with a developer to reveal the resist pattern RP. The development process is not particularly limited, but for example, a chemically amplified resist may be developed by immersing the blank substrate 2 after electron beam or laser light writing in a developer such as tetramethylammonium hydroxide, or a positive-type ZEP resist (manufactured by Zeon Corporation) may be developed using amyl acetate (ZED-N50 (product name)). After development, the substrate may be rinsed with pure water or IPA (isopropyl alcohol), dried, and the resist pattern RP may be obtained. This forms a pattern on the absorption layer 40 having parts not protected by the resist mask and parts protected by the resist pattern RP. Note that if the resist pattern is formed after the first absorption layer oxidation process described later, this process may be distinguished as the first resist pattern formation process from the resist pattern formation process after the first absorption layer oxidation process. On the other hand, if there is no need to distinguish it from the resist pattern formation process after the first absorption layer oxidation process, this process is simply called the "resist pattern formation process".

[0172] 3.4. Mask Pattern Formation Process In the mask pattern formation process of this disclosure, as shown in Figures 3D to 3H, the region of the absorption layer 40 in which the resist pattern RP does not exist is selectively etched to form the mask pattern region 10a. The steps that the mask pattern formation process may comprise will be described in detail below.

[0173] 3.4.1. Hard Mask Etching Process The mask pattern formation process of this disclosure may include a hard mask etching step in which the exposed hard mask H is etched, as shown in Figure 3D. This allows the pattern to be transferred to the absorption layer with higher precision. Specifically, a hard mask H of several nm in thickness, such as a Cr-based thin film, an SiO2 thin film, or a TiN thin film, may be provided on the absorption layer 40, and the hard mask H may be etched via a resist pattern RP, followed by a two-step process in which the absorption layer 40 is etched using the hard mask H as a mask. This tends to further improve the controllability of the line width of the mask pattern.

[0174] In the hard mask etching process, the hard mask H may be wet-etched or dry-etched, but dry etching is preferred from the viewpoint of pattern accuracy and edge straightness. Specifically, a TaO film that also serves as a low-reflectivity layer can be formed as the hard mask H on the absorption layer 40, and this can be selectively removed by dry etching with CF4 gas to expose the underlying absorption layer 40. For example, when removing the TaO film, a fluorine-based plasma mainly composed of CF4 gas is used. Then, the exposed absorption layer 40 can be anisotropically dry-etched with a chlorine-based plasma mainly composed of Cl2 gas to form a pattern with high precision. When wet etching is performed, although not particularly limited, strong acids such as cerium-dic ammonium nitrate or a sulfuric acid mixture may be used. Note that SiO2 or TiN may be used as the hard mask H.

[0175] 3.4.2. Absorption layer etching process The mask pattern formation process of this disclosure may include an absorption layer etching step in which the absorption layer 40 exposed after the hard mask etching step is etched, as shown in Figure 3E. In the absorption layer etching step, the absorption layer 40 may be wet etched or dry etched.

[0176] For example, if the absorption layer 40 is made of a Ta-based material, anisotropic dry etching may be performed using an inductively coupled plasma reactive ion etching (ICP-RIE) apparatus, with Cl2 or O2 gas as the main component. Specifically, the absorption layer can be etched anisotropically by plasma discharge of gases such as Cl2 / O2 / N2.

[0177] Furthermore, although Figures 3D and 3E illustrate embodiments using the same resist layer R, when etching the absorption layer, the resist layer used for etching the hard mask may be removed once and then etched. Alternatively, a new resist layer may be formed. In this case, an unscanned alignment mark is used to form a pattern on the newly formed resist layer. That is, when etching different layers, the same resist layer R and hard mask H may be used for etching all layers, or a different resist layer R may be used for etching each layer.

[0178] The method for etching the absorption layer 40 in the region corresponding to the absorption area so that it has a tapered shape as shown in Figure 2D is not particularly limited, but one example is to use a mixed gas of CF4 and CHF3, which has strong deposition properties, as the etching gas. As a result, the etching reaction proceeds simultaneously with the formation of a thin deposited film on the sidewall, so the etching rate of the sidewall changes gradually from the top to the base, and as a result it is easy to obtain a tapered shape. Such tapered formation can also be controlled by adjusting the mixing ratio of CF4 / CHF3. In addition, other deposition gases (CH2F2, C4F8, etc.) may be used in combination.

[0179] 3.4.3. Oxide layer removal process The mask pattern formation process of this disclosure may include an oxide layer removal step to remove the oxide layer 70 exposed after the absorption layer etching step, as shown in Figure 3F. In the oxide layer removal step, the oxide layer 70 may be removed by etching. Specifically, the oxide layer 70 may be wet etched or dry etched.

[0180] For example, if the oxide layer 70 is composed of a Ta-based material, anisotropic dry etching may be performed using an inductively coupled plasma reactive ion etching (ICP-RIE) apparatus, with Cl2 or O2 gas as the main component. Specifically, the absorption layer can be etched anisotropically by plasma discharge of gases such as Cl2 / O2 / N2.

[0181] Alternatively, if the oxide layer 70 is made of a Ru-based material, dry etching may be performed using a fluorine-based gas such as CF4 gas.

[0182] After the oxide layer removal process, the resist pattern RP may be removed to expose the hard mask H, as shown in Figure 3G.

[0183] 3.4.4. First Absorption Layer Oxidation Process The manufacturing method of the reflective mask of this disclosure may include a first absorption layer oxidation step, as shown in Figure 3H, in which the side surface of the absorption layer 40 is oxidized. This oxidizes the side surface of the absorption layer 40 in the later absorption region 10a1, forming a coating layer 80. The method for oxidizing the absorption layer 40 in the later absorption region 10a1 is not particularly limited, but examples include oxygen plasma treatment and heat treatment in an oxygen atmosphere. The first absorption layer oxidation step may be performed after the oxide layer removal step or after the absorption layer etching step.

[0184] 3.5. Second film formation process and second resist pattern formation process The method for manufacturing a reflective mask according to this disclosure may include, as shown in Figure 3I, a second film formation step of forming a resist layer on an absorption layer 40, and a second resist pattern formation step of performing electron beam or laser light writing and development to form a resist pattern on the resist layer. As a result, the area corresponding to the mask pattern region 10a is protected by the resist pattern RP, while the area corresponding to the recessed region 10b is not covered by the resist pattern RP and is exposed. The specific embodiments of the second film formation step and the second resist pattern formation step are the same as the specific embodiments of the first film formation step and the first resist pattern formation step, respectively.

[0185] The second film formation step and the second resist pattern formation step may be performed after the first absorption layer oxidation step or before the first absorption layer oxidation step.

[0186] Furthermore, if it is not necessary to distinguish the second film deposition process and the second resist pattern formation process from the first film deposition process and the first resist pattern formation process, both processes will simply be referred to as the "film deposition process" and the "resist pattern formation process," respectively.

[0187] 3.6. Cap layer etching process (light shielding formation) The method for manufacturing a reflective mask according to this disclosure may include, as shown in Figure 3J, an oxide layer removal step, a first absorption layer oxidation step, or a cap layer etching step in which the cap layer 30 is etched after the second resist pattern formation step. The cap layer etching step is performed on the region corresponding to the etched region 10b, but not on the region corresponding to the mask pattern region 10a. In the cap layer etching step, the cap layer 30 may be wet etched or dry etched.

[0188] As shown in Figure 3J, when the cap layer etching process is performed after the second resist pattern formation process, the absorption layer 40 and oxide layer 70 may be removed in advance by the absorption layer etching process and oxide layer removal process described above, thereby exposing the cap layer 30.

[0189] Alternatively, although not shown in the diagram, the absorption layer 40 and oxide layer 70 in the region corresponding to the etched region 10b may be removed at the same timing as the absorption layer etching process and oxide layer removal process described above. In that case, the second film formation process and the second resist pattern formation process may not be performed.

[0190] For example, if the cap layer 30 is made of a Ru-based material, the cap layer 30 may be dry-etched using a fluorine-based gas such as CF4 gas.

[0191] 3.7. Etching process of the reflective layer The manufacturing method of the reflective mask of this disclosure may include a reflective layer etching step in which the reflective layer 20 is etched after the cap layer etching step, as shown in Figure 3K. The reflective layer etching step is performed on the region corresponding to the recessed region 10b, but not on the region corresponding to the mask pattern region 10a. In the reflective layer etching step, the reflective layer 20 may be wet etched or dry etched.

[0192] For example, if the reflective layer 20 is composed of a periodic multilayer film of Si and Mo, the reflective layer 20 may be dry-etched using a fluorine-based gas such as CF4 gas.

[0193] As shown in Figure 3K, the first reflective layer etching step may partially etch the exposed substrate 10. This makes it possible to reliably remove the reflective layer 20 by etching.

[0194] 3.8. Resist Pattern Removal Process The method for manufacturing a reflective mask according to this disclosure may include a resist pattern removal step after the reflective layer etching step, as shown in Figure 3L, in which the resist pattern RP is removed. The resist pattern RP is not particularly limited, but may be removed, for example, with oxygen plasma or with an aqueous solution of sulfuric acid and hydrogen peroxide.

[0195] If a mask pattern is to be formed after the resist pattern removal step, the first film deposition step, the first resist pattern formation step, and the mask pattern formation step may be performed further.

[0196] Furthermore, although Figure 3L illustrates the formation of an etched region via a hard mask H, the etched region may also be formed using only the resist layer without the hard mask H. That is, the second film formation step, the second resist pattern formation step, the cap layer etching step, the reflective layer etching step, and the resist pattern removal step may be performed after the hard mask removal step described later.

[0197] 3.9. Hard Mask Removal Process The method for manufacturing a reflective mask according to this disclosure may include a hard mask removal step to remove the remaining hard mask H after the resist pattern removal step, as shown in Figure 3M. The formation of the resist pattern RP may be completed before the hard mask removal step. In the hard mask removal step, the hard mask H may be wet-etched or dry-etched. The specific method for removing the hard mask H is the same as described in detail in the hard mask etching step. Note that the hard mask removal step may be performed after the cap layer etching step.

[0198] The hard mask removal step may be performed after the first absorption layer oxidation step shown in Figure 3H. In this case, the second absorption layer oxidation step, described later, may be performed after the hard mask removal step.

[0199] 3.10. Second absorption layer oxidation process The manufacturing method of the reflective mask of this disclosure may include a second absorption layer oxidation step, as shown in Figure 3N, in which the upper surface of the absorption layer 40 in the absorption region 10a1 is oxidized. This oxidizes the surface of the absorption layer 40 in the absorption region 10a1 and forms a coating layer 80. The method for oxidizing the absorption layer 40 in the absorption region 10a1 is not particularly limited, but examples include oxygen plasma treatment and heat treatment under an oxygen atmosphere. The first absorption layer oxidation step and the second absorption layer oxidation step described above are collectively referred to as the absorption layer oxidation step. Furthermore, if only one of the first absorption layer oxidation step and the second absorption layer oxidation step is performed, that step is simply referred to as the absorption layer oxidation step.

[0200] The second absorption layer oxidation step may be performed after the hard mask removal step. Alternatively, the coating layer 80 may be formed in advance on the lower side of the hard mask H in the stacking direction D3 at the blank substrate stage, eliminating the need to perform the second absorption layer oxidation step.

[0201] The absorption layer oxidation step may be performed after the absorption layer etching step and before the oxide layer removal step. In this case, by forming a thicker coating layer 80 during the absorption layer oxidation step, the coating layer 80 can be maintained even after the oxide layer removal step.

[0202] Furthermore, the absorption layer oxidation process may be performed after the oxide layer removal process and before the cap layer etching process. This process may cause oxidation of the cap layer 30 in the reflection region 10a2. In that case, the oxidized region of the cap layer 30 can be subjected to reduction treatment with OH radicals or H radicals to return the cap layer 30 to its pre-oxidation state.

[0203] In the preparation step for the manufacturing method of the reflective mask of this disclosure, as shown in Figure 3O, a blank substrate 2' may be prepared, comprising a base material 10, a reflective layer 20, a cap layer 30 containing a first metal, an oxide layer 70, an absorption layer 40 containing a second metal, a coating layer 80, and a top coat layer 90, laminated in at least this order. The blank substrate 2' may also have a hard mask H on the side of the absorption layer 40 opposite to the base material 10, and a conductive layer 60 on the side of the base material 10 opposite to the absorption layer 40.

[0204] The coating layer 80 and the topcoat layer 90 are not particularly limited, but may be formed by sputtering methods such as ion beam sputtering or magnetron sputtering. The deposition atmosphere is not particularly limited, but examples include an argon atmosphere, a nitrogen atmosphere, or an oxygen atmosphere.

[0205] The method for manufacturing the reflective mask according to this disclosure, when a blank substrate 2' is prepared in the preparation step, will be described in detail below. However, the steps that are the same as those for manufacturing the reflective mask according to this disclosure when a blank substrate 2 is prepared in the preparation step will be omitted from the explanation.

[0206] 3A.1. Topcoat layer etching process The method for manufacturing a reflective mask according to this disclosure may include a topcoat layer etching step, after the hard mask etching step, etching the topcoat layer 90 as shown in Figure 3P.

[0207] In the topcoat layer etching process, the topcoat layer 90 may be wet-etched or dry-etched.

[0208] For example, if the topcoat layer 90 is made of a Ru-based material, the topcoat layer 90 may be dry-etched using a fluorine-based gas such as CF4 gas.

[0209] 3A.2. Coating Layer Etching Process The method for manufacturing a reflective mask according to this disclosure may include a coating layer etching step in which the coating layer 80 is etched after the top coat layer etching step.

[0210] In the coating layer etching process, the coating layer 80 may be wet-etched or dry-etched.

[0211] For example, the coating layer 80 may be dry-etched using a fluorine-based gas such as CF4 gas, or it may be dry-etched using Cl2 or O2 gas. In the case of the coating layer 80, dry etching using a fluorine-based gas is preferred from the viewpoint of improving the processing speed.

[0212] 3A.3. Absorption layer oxidation process The method for manufacturing a reflective mask according to this disclosure may include an oxidation treatment step in which the side surface of the absorption layer 40 in the absorption region 10a1 is oxidized, as shown in Figure 3Q. If the coating layer 80 on the blank substrate 2' contains the same second metal oxide as the absorption layer 40, the coating layer 80 formed on the side surface of the absorption layer 40 in the absorption layer oxidation step and the coating layer 80 on the blank substrate 2 (i.e., the coating layer 80 located between the absorption layer 40 and the top coat layer 90) will have the same components, improving the continuity of the coating layer 80. As a result, the coating layer 80 is less likely to peel off from the absorption layer 40, and cleaning resistance tends to improve. The absorption layer oxidation step may be performed after the hard mask removal step or before the hard mask removal step.

[0213] 3B.1. Second absorption layer etching process Furthermore, the reflective mask of this disclosure may have a second absorbent layer 100 instead of the topcoat layer 90. In that case, the method for manufacturing the reflective mask of this disclosure may have a second absorbent layer etching step instead of a topcoat layer etching step.

[0214] In the second absorption layer etching step, the second absorption layer 100 is etched. In the second absorption layer etching step, the second absorption layer 100 may be wet etched or dry etched.

[0215] For example, if the second absorption layer 100 is made of a Ru-based material, the top coat layer 90 may be dry-etched using a fluorine-based gas such as CF4 gas.

[0216] 4. How to use a reflective mask Figure 4 is a schematic diagram showing an example of how to use the reflective mask of this disclosure. An example of how to use the reflective mask 1 will be explained using Figure 4.

[0217] Figure 4 illustrates a method in which EUV light emitted from an EUV light source L is reflected multiple times by a reflective mask 1 and a reflector RM, and then incident on a wafer W on a wafer stage WS to form a circuit pattern. As shown in Figure 4, the EUV light is shaped and focused by being reflected multiple times by the reflector RM. Subsequently, the EUV light is reflected by the reflective mask 1 to form a shape based on a predetermined circuit pattern. After being reflected by the reflective mask 1, the EUV light is reflected multiple times again by the reflector RM to form a reduced version of that shape.

[0218] Since EUV light is absorbed by air and other elements, it is preferable that the atmosphere of an optical system using EUV light be a vacuum. [Explanation of Symbols]

[0219] 1...Reflective mask, 1a...First surface, 1b...Second surface, 2A, B...Blank substrate, 10...Substrate, 10a...Mask pattern area, 10a1...Absorption area, 10a2...Reflection area, 10b...Erection area, 10c...Outer edge area, 20...Reflection layer, 30...Cap layer, 40...Absorption layer, 40a...Top surface, 40b...Side surface, 60...Conductive layer, 70...Oxide layer, 80...Coating layer, 90...Top coat layer, 100...Second absorption layer, R...Resist layer, RP...Resist pattern, H...Hard mask, L...Light source, RM...Reflector, MS...Mask stage, W...Wafer, WS...Wafer stage.

Claims

1. A reflective mask comprising a substrate, a reflective layer, a cap layer containing a first metal, an oxide layer, and an absorption layer containing a second metal, laminated in at least this order, The oxide layer comprises an oxide of the first metal and / or the second metal. The reflective mask has a first surface on the absorption layer side and a second surface on the substrate side. The first surface has a mask pattern region on which a mask pattern is formed, The mask pattern region includes an absorption region where the absorption layer exists and a reflection region where the absorption layer does not exist. In the reflective region, the cap layer is exposed. Reflective mask.

2. The first metal includes one or more selected from the group consisting of Ru, Rh, Hf, Cr, and Zr. The reflective mask according to claim 1.

3. The second metal includes one or more selected from the group consisting of Ta, W, Nb, Pt, Cr, Ni, Sn, In, Te, Sb, and Ti. The reflective mask according to claim 1.

4. The thickness Ho of the oxide layer is 0.3 nm or more and 1.0 nm or less. The reflective mask according to claim 1.

5. The ratio of the thickness Hk of the absorption layer to the thickness Ho of the oxide layer (Hk / Ho) is 20 or more and 250 or less. The reflective mask according to claim 1.

6. The Ta peak intensity in the X-ray absorption fine structure spectrum of the reflection region is 1 / 50 or less of the Ta peak intensity in the X-ray absorption fine structure spectrum of the absorption region. The reflective mask according to claim 1.

7. The concentration of Ta in the cap layer in the reflection region is 1000 ppm or less. The reflective mask according to claim 1.

8. A reflective mask comprising a substrate, a reflective layer, a cap layer containing a first metal, an oxide layer, and an absorbing layer containing a second metal, laminated in at least this order, The oxide layer comprises an oxide of the first metal and / or the second metal. The reflective mask has a first surface on the absorption layer side and a second surface on the substrate side. The first surface has a mask pattern region on which a mask pattern is formed, The mask pattern region includes an absorption region where the absorption layer exists and a reflection region where the absorption layer does not exist. In a cross-sectional view, the laminate including the absorption layer and the oxide layer in the absorption region has a tapered shape that widens from the absorption layer side toward the boundary between the oxide layer and the cap layer. Reflective mask.

9. In a cross-sectional view, the tapered side surface of the laminate has a straight portion and a curved portion connected to the straight portion. The height from the boundary to the connection point between the straight section and the curved section is 0.1 nm or more and 15 nm or less. In a plan view, the distance between the connecting portion and the end of the laminate at the boundary is 1.0 nm or more and 5.2 nm or less. The reflective mask according to claim 8.

10. In a plan view, the distance between the edge of the upper surface of the laminate and the edge of the laminate at the boundary is 1.0 nm or more and 6.0 nm or less. The reflective mask according to claim 8.

11. A reflective mask comprising a substrate, a reflective layer, a cap layer containing a first metal, an oxide layer, and an absorbing layer containing a second metal, laminated in at least this order, The oxide layer comprises an oxide of the first metal and / or the second metal. The reflective mask has a first surface on the absorption layer side and a second surface on the substrate side. The first surface has a mask pattern region on which a mask pattern is formed, The mask pattern region includes an absorption region where the absorption layer exists and a reflection region where the absorption layer does not exist. In a cross-sectional view, the laminate in the absorption region, including the absorption layer and the oxide layer, has a shape in which the width narrows from the absorption layer side toward the boundary between the oxide layer and the cap layer. Reflective mask.

12. The side and top surfaces of the absorption layer in the absorption region are covered with a coating layer containing the oxide of the second metal. A reflective mask according to claim 1, 8, or 11.

13. The thickness Hh of the aforementioned coating layer is 1 nm or more and 8 nm or less. The reflective mask according to claim 12.

14. The ratio of the thickness Hk of the absorption layer to the thickness Hh of the coating layer (Hk / Hh) is 3 or more and 80 or less. The reflective mask according to claim 12.

15. On the side of the coating layer opposite to the substrate, a second absorbent layer or topcoat layer containing a third metal is provided. The reflective mask according to claim 12.

16. The third metal includes one or more selected from the group consisting of Ru, Ta, W, Nb, Pt, Rh, Re, Cr, and Ti. The reflective mask according to claim 15.

17. A preparation step for preparing a blank substrate comprises a substrate, a reflective layer, a cap layer containing a first metal, an oxide layer, and an absorption layer containing a second metal, laminated in at least this order, wherein the oxide layer contains an oxide of the first metal and / or the second metal. A film formation step of forming a resist layer on the absorption layer of the blank substrate, A resist pattern formation step involves performing electron beam or laser light writing and development processing to form a resist pattern on the resist layer, The process includes a mask pattern formation step of selectively etching the region of the absorption layer in which the resist pattern does not exist, thereby forming a mask pattern region that includes an absorption region in which the absorption layer exists and a reflection region in which the absorption layer does not exist. The mask pattern formation step includes an oxide layer removal step in which the oxide layer is removed in the reflection region. A method for manufacturing a reflective mask.

18. The process includes an absorption layer oxidation step, in which the absorption layer in the absorption region is oxidized. The manufacturing method according to claim 17.

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