Reflective photomasks and methods for manufacturing reflective photomasks

Abstract

This disclosure provides a reflective photomask for patterning transfer that uses light of wavelengths in the extreme ultraviolet region as a light source, and a reflective photomask having good in-plane dimensional uniformity, and a method for manufacturing the same. [Solution] The reflective photomask 200b according to the embodiment of the present disclosure comprises a substrate 13, a reflective layer 12 formed on the substrate 13 and having a multilayer structure that reflects EUV light, and an absorbing layer 10 formed on the reflective layer 12 that absorbs EUV light, wherein the absorbing layer 10 has a main pattern region 20 on which a transfer pattern that is transferred to a photoreceptor by exposure is formed, and a peripheral region 211 that demarcates the main pattern region 20, and the peripheral region 211 has at least a plurality of fine patterns a having a width dimension smaller than the minimum width dimension that is transferred to the photoreceptor by exposure.

Description

[Technical Field]

[0001] The present invention relates to a reflective photomask used in lithography using ultraviolet light as a light source, and to a method for manufacturing a reflective photomask. [Background technology]

[0002] In semiconductor device manufacturing processes, the miniaturization of semiconductor devices has led to increased demand for miniaturization of photolithography technology. The minimum resolution dimension of a transfer pattern in photolithography largely depends on the wavelength of the exposure light source; the shorter the wavelength, the smaller the minimum resolution dimension can be. For this reason, exposure light sources are being replaced from conventional 193nm ArF excimer laser light to 13.5nm EUV (Extreme Ultra Violet) light.

[0003] Since light in the EUV region is absorbed to a high extent by most materials, reflective photomasks are used as photomasks for EUV exposure (EUV masks) (see, for example, Patent Document 1). Patent Document 1 discloses an EUV photomask obtained by forming a reflective layer consisting of a multilayer film in which Mo (molybdenum) layers and Si (silicon) layers are alternately stacked on a glass substrate, forming a light-absorbing layer mainly composed of Ta (tantalum) on top of that, and forming a pattern on this light-absorbing layer.

[0004] Furthermore, as mentioned above, EUV lithography cannot use refractive optics that utilize light transmission, so the optical components of the exposure machine are reflective (mirror) rather than lenses. This presents a problem in that the incident light on the reflective photomask (EUV mask) and the reflected light from the reflective photomask cannot be designed to be coaxial. Typically, EUV lithography employs a method in which the optical axis is tilted 6 degrees from the perpendicular direction of the EUV mask, and the reflected light, reflected at a -6 degree angle, is guided to the semiconductor substrate.

[0005] Currently, with the miniaturization of patterns using EUV lithography, the requirements for critical dimension uniformity (CDU) within the photomask surface are also becoming stricter. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 5418293 [Overview of the project] [Problems that the invention aims to solve]

[0007] The present invention has been made in view of the above problems, and aims to provide a reflective photomask for patterning transfer that uses light of wavelengths in the extreme ultraviolet region as a light source, and which has good in-plane uniformity of dimensions, and a method for manufacturing the same. [Means for solving the problem]

[0008] This disclosure has been made to solve the above problems, and a reflective photomask according to one aspect of this disclosure comprises a substrate, a reflective layer formed on the substrate and having a multilayer structure that reflects EUV light, and an absorbing layer formed on the reflective layer and absorbing EUV light, wherein the absorbing layer has a main pattern region on which a transfer pattern to be transferred to a photoreceptor by exposure is formed, and a peripheral region that demarcates the main pattern region, and the peripheral region has at least a plurality of fine patterns having a width dimension smaller than the minimum width dimension to be transferred to the photoreceptor by exposure It is characterized by having.

[0009] Furthermore, a reflective photomask according to one aspect of the present disclosure comprises a substrate, a reflective layer formed on the substrate and having a multilayer structure that reflects EUV light, and an absorbing layer formed on the reflective layer and absorbing EUV light, wherein the absorbing layer has a main pattern region on which a transfer pattern to be transferred to a photoreceptor by exposure is formed, and a main pattern non-formed region provided within the main pattern region and in which the transfer pattern is not formed, and the area of ​​the main pattern non-formed region is 50 μm in plan view. 2 The above is characterized in that the main pattern non-formed region has at least a plurality of fine patterns having a width dimension smaller than the minimum width dimension transferred to the photoreceptor by exposure.

[0010] Furthermore, the shape of the fine pattern in the reflective photomask according to one aspect of this disclosure may be a linear shape in plan view.

[0011] Furthermore, the width dimension of the fine pattern in a reflective photomask according to one aspect of this disclosure may be 30 nm or less in plan view if the shape of the fine pattern is linear in plan view.

[0012] Furthermore, the shape of the fine pattern in the reflective photomask according to one aspect of this disclosure may be square in plan view.

[0013] Furthermore, the side dimension of the fine pattern in a reflective photomask according to one aspect of this disclosure may be 60 nm or less in plan view if the shape of the fine pattern is square in plan view.

[0014] Furthermore, the shape of the fine pattern in the reflective photomask according to one aspect of this disclosure may be a regular octagon in plan view.

[0015] Furthermore, the side length of the fine pattern in a reflective photomask according to one aspect of this disclosure may be 50 nm or less in plan view if the shape of the fine pattern is a regular octagon in plan view.

[0016] Further, the aperture ratio (area of the fine pattern in the peripheral region / area of the peripheral region) of the fine pattern in the peripheral region of the reflective photomask according to one aspect of the present disclosure may be in the range of 1.0% or more and 50.0% or less.

[0017] Further, the aperture ratio (area of the fine pattern in the non-main pattern region / area of the non-main pattern region) of the fine pattern in the non-main pattern region of the reflective photomask according to one aspect of the present disclosure may be in the range of 1.0% or more and 50.0% or less.

[0018] Further, the reflective photomask according to one aspect of the present disclosure may include a protective layer between the reflective layer and the absorption layer.

[0019] Further, a method for manufacturing a reflective photomask according to one aspect of the present disclosure is a method for manufacturing a reflective photomask including a substrate, a reflective layer formed on the substrate and reflecting EUV light having a multilayer film structure, and an absorption layer formed on the reflective layer and absorbing EUV light, the method having a step of forming, in the absorption layer, a main pattern region in which a transfer pattern transferred to a photoreceptor by exposure is formed, and a peripheral region partitioning the main pattern region, and the peripheral region having at least a plurality of fine patterns having a width dimension smaller than the minimum width dimension transferred to the photoreceptor by exposure. characterized by having at least.

[0020] Further, a method for manufacturing a reflective photomask according to one aspect of the present disclosure is a method for manufacturing a reflective photomask including a substrate, a reflective layer formed on the substrate and reflecting EUV light having a multilayer film structure, and an absorption layer formed on the reflective layer and absorbing EUV light, the method having a step of forming, in the absorption layer, a main pattern region in which a transfer pattern transferred to a photoreceptor by exposure is formed, and a non-main pattern region provided within the main pattern region and being a region where the transfer pattern is not formed, and the area of the non-main pattern region being 50 μm in plan view. 2The above is characterized in that the main pattern non-formation region has at least a plurality of fine patterns having a width dimension smaller than the minimum width dimension transferred to the photosensitive member by exposure.

Effect of the Invention

[0021] According to one aspect of the present disclosure, a reflective photomask can be provided, which is a reflective photomask for patterning transfer using light having a wavelength in the extreme ultraviolet region as a light source and has good in-plane dimensional uniformity. Further, according to one aspect of the present disclosure, a method for manufacturing a reflective photomask can be provided, which is a method for manufacturing a reflective photomask for patterning transfer using light having a wavelength in the extreme ultraviolet region as a light source and has good in-plane dimensional uniformity.

Brief Description of the Drawings

[0022] [Figure 1] It is a schematic cross-sectional view showing the structure of a reflective photomask blank according to the first embodiment of the present disclosure. [Figure 2] It is a schematic cross-sectional view showing the structure of a reflective photomask according to the prior art. [Figure 3] It is a schematic cross-sectional view showing the structure of a reflective photomask according to the first embodiment of the present disclosure. [Figure 4] It is a schematic plan view showing the structure of a reflective photomask according to the prior art. [Figure 5] It is a schematic plan view showing the structure of a reflective photomask according to the first embodiment of the present disclosure. [Figure 6] It is a schematic cross-sectional view showing the structure of a reflective photomask according to the second embodiment of the present disclosure. [Figure 7] It is a schematic plan view showing the structure of a reflective photomask according to the second embodiment of the present disclosure. [Figure 8] It is a schematic cross-sectional view showing the structure of a reflective photomask according to a modification of the first embodiment of the present disclosure. [Figure 9]This is a schematic cross-sectional view showing the structure of a reflective photomask according to a modification of the second embodiment of the present disclosure. [Figure 10] This is a schematic cross-sectional view showing the manufacturing process of a reflective photomask according to an embodiment of the present disclosure. [Figure 11] This is a schematic cross-sectional view showing the manufacturing process of a reflective photomask according to an embodiment of the present disclosure. [Figure 12] This is a schematic cross-sectional view showing the manufacturing process of a reflective photomask according to an embodiment of the present disclosure. [Figure 13] This is a schematic cross-sectional view showing the manufacturing process of a reflective photomask according to an embodiment of the present disclosure. [Figure 14] This is a schematic cross-sectional view showing the manufacturing process of a reflective photomask according to an embodiment of the present disclosure. [Figure 15] This is a schematic cross-sectional view showing the manufacturing process of a reflective photomask according to an embodiment of the present disclosure. [Figure 16] This is a schematic cross-sectional view showing the manufacturing process of a reflective photomask according to an embodiment of the present disclosure. [Figure 17] This is a schematic cross-sectional view showing the manufacturing process of a reflective photomask according to an embodiment of the present disclosure. [Figure 18] This is a schematic cross-sectional view showing the structure at the boundary between the main pattern region and the peripheral region in a comparative example of the reflective photomask according to the present disclosure. [Figure 19] This is a schematic plan view showing the structure of a conventional reflective photomask. [Modes for carrying out the invention]

[0023] As a result of diligent research, the inventors have discovered that dimensional uniformity within the photomask surface can be improved by forming a fine pattern with a width smaller than the minimum width transferred to the photoreceptor (resist on a silicon wafer) by exposure in the peripheral region that demarcates the main pattern region where the transfer pattern transferred to the photoreceptor by exposure is formed. This has led the inventors to invent a reflective photomask with improved dimensional uniformity within the photomask surface. Furthermore, the inventors have formed a main pattern non-formation region, which is a region where no transfer pattern is formed, within the main pattern region where a transfer pattern is formed on the photoreceptor by exposure, and the area of ​​this main pattern non-formation region is 50 μm in plan view. 2 Furthermore, we have found that by forming a fine pattern in the main pattern non-formation region having a width smaller than the minimum width transferred to the photoreceptor (resist on the silicon wafer) by exposure, dimensional uniformity within the photomask surface can be improved. As a result, the inventors have invented a reflective photomask with improved dimensional uniformity within the photomask surface.

[0024] In short, this disclosure proposes and provides a new design concept for improving dimensional uniformity within the surface of a reflective photomask. This point will be explained below. In conventional design approaches, in order to improve dimensional uniformity within the photomask surface, attention has been focused on the constituent materials of the absorption layer on which the transfer pattern transferred to the photoreceptor (resist on a silicon wafer) by exposure is formed. For example, the combination of constituent materials and the content of each constituent material have been adjusted.

[0025] In response to this, the inventors focused on the fact that forming specific fine patterns in the peripheral regions that demarcate the main pattern region and in the main pattern non-formed regions within the main pattern region results in differences in the test results for dimensional uniformity within the photomask surface, and found that these fine patterns affect the dimensional uniformity within the photomask surface. In other words, they newly discovered that in order to improve the dimensional uniformity within the photomask surface, it is important not only to adjust the combination of constituent materials and the content of constituent materials in the absorption layer, but also to form specific fine patterns in the peripheral regions that demarcate the main pattern region and in the main pattern non-formed regions within the main pattern region. Thus, the design concept presented in this disclosure differs significantly from conventional design concepts that focused solely on the combination of constituent materials and the adjustment of their content in the absorption layer. Instead, it aims to easily improve dimensional uniformity within the photomask surface by forming specific fine patterns in the peripheral regions that demarcate the main pattern region and in the non-main pattern regions formed within the main pattern region.

[0026] The embodiments of this disclosure will be described below with reference to the drawings. Here, the configuration shown in the drawings is schematic, and the relationship between thickness and planar dimensions, the ratio of the thickness of each layer, etc., will differ from reality. Furthermore, the embodiments shown below are illustrative examples of configurations for realizing the technical concept of this disclosure, and the technical concept of this disclosure is not limited to the materials, shapes, structures, etc. of the components described below. The technical concept of this disclosure can be modified in various ways within the technical scope defined by the claims described in the patent claims.

[0027] (First Embodiment) Figure 1 is a schematic cross-sectional view showing the structure of a reflective photomask blank 100 according to the first embodiment of the present disclosure. As shown in Figure 1, the reflective photomask blank 100 according to the first embodiment of the present disclosure comprises at least a substrate 13, a reflective layer 12 formed on the substrate 13 and having a multilayer structure that reflects EUV light, and an absorbing layer 10 formed on the reflective layer 12 that absorbs EUV light. Furthermore, as shown in Figure 1, it is more preferable that the reflective photomask blank 100 includes a protective layer 11 between the reflective layer 12 and the absorbing layer 10.

[0028] Before describing the structure of the reflective photomask according to the first embodiment of this disclosure, the basic configuration of a conventional reflective mask will be explained using Figures 2 and 4. Figure 2 is a cross-sectional view illustrating an example configuration of a conventional reflective photomask 200a. As shown in Figure 2, the main pattern region 20 in the conventional reflective photomask 200a is On one side of the substrate 13, a reflective layer 12, a protective layer 11, and an absorption pattern 101 are stacked in this order. The absorption pattern 101 is formed by patterning the absorption layer 10, which will be described later. A conductive film 14 may also be formed on the other side of the substrate.

[0029] Figure 4 is a plan view of a conventional reflective photomask 200a. The 200a has a single or multiple unit for forming semiconductor integrated circuit patterns on a silicon wafer. Multiple main pattern regions 20 are formed. Each main pattern region 20 is demarcated by a peripheral region 21 that does not contribute to the formation of the semiconductor integrated circuit pattern. The peripheral region 21 is covered with an absorption layer 10, except for some accessory patterns, to demarcate the chip on the silicon wafer, and is a region that does not contribute to transfer. Furthermore, a light-shielding band 22 is formed at the edge of the desired exposure region at the outermost periphery of the peripheral region 21. The light-shielding band 22 is surrounded by an outer peripheral region 23.

[0030] Next, the basic configuration of the reflective photomask 200b according to the first embodiment of this disclosure will be described with reference to Figures 3 and 5. Figure 3 is a cross-sectional view illustrating an example configuration of a reflective photomask 200b according to the first embodiment of this disclosure. As shown in Figure 3, in the reflective photomask 200b according to the first embodiment of this disclosure, the main pattern region 20 is formed by stacking a reflective layer 12, a protective layer 11, and an absorption pattern 101 in that order on one side of the substrate 13. The absorption pattern 101 is formed by patterning an absorption layer 10, which will be described later. A conductive film 14 may also be formed on the other side of the substrate.

[0031] Figure 5 is a plan view of a reflective photomask 200b according to the first embodiment of this disclosure. A single reflective photomask 200b has one or more main pattern regions 20 formed on it for forming a semiconductor integrated circuit pattern on a silicon wafer. Each main pattern region 20 is demarcated by a peripheral region 211 that does not contribute to the formation of the semiconductor integrated circuit pattern. The peripheral region 211 is a region that does not contribute to the transfer, and a plurality of fine patterns a (see Figure 3) having a width dimension smaller than the minimum width dimension that is transferred to the photoreceptor (resist on the silicon wafer) by exposure are formed in the peripheral region 211. The light-shielding band 22 is surrounded by an outer peripheral region 23.

[0032] Thus, the reflective photomask 200b according to the first embodiment of this disclosure is photosensitive by exposure in the peripheral region 21 of the conventional reflective photomask 200a shown in Figures 2 and 4. This involves forming multiple fine patterns a, each having a width smaller than the minimum width dimension that is transferred to the body (resist on a silicon wafer). More specifically, the reflective photomask 200b according to the first embodiment of this disclosure is A reflective photomask manufactured using a reflective photomask blank 100 according to the first embodiment, comprising a substrate 13, a reflective layer 12 formed on the substrate 13 and having a multilayer structure that reflects EUV light, and an absorbing layer 10 formed on the reflective layer 12 and absorbing EUV light, wherein the absorbing layer 10 has a main pattern region 20 on which a transfer pattern that is transferred to a photoreceptor (resist on a silicon wafer) by exposure is formed, and a peripheral region 211 that demarcates the main pattern region 20, and the peripheral region 211 has at least a plurality of fine patterns a having a width dimension smaller than the minimum width dimension that is transferred to the photoreceptor (resist on a silicon wafer) by exposure. Furthermore, the plurality of fine patterns a may be in contact with the main pattern region 20 if they are not transferred to the photoreceptor (resist on a silicon wafer) by exposure.

[0033] Here, "fine pattern a having a width smaller than the minimum width transferred to the photoreceptor by exposure" means a fine pattern on the absorption layer 10 of the reflective photomask 200b having a line width that is not resolved on the photoreceptor (resist on a silicon wafer), i.e., a line width below the resolution limit. The typical resolution limit line width in a single exposure using a conventional exposure apparatus is 32 nm to 56 nm. Furthermore, the fine pattern a in this embodiment is a pattern formed in such a way that the surface of the reflective layer 12 or the surface of the protective layer 11 is exposed, similar to the transfer pattern formed within the main pattern region 20.

[0034] The shape of the fine pattern a in the peripheral region 211 may, for example, be a straight line in plan view. If the shape of the fine pattern a is a straight line in plan view, the aperture ratio can be easily increased by making the aperture direction of the fine pattern a perpendicular to the aperture direction of the absorption pattern 101 in the main pattern region 20. Furthermore, if the shape of the fine pattern a is linear in plan view, the width dimension of the fine pattern a is preferably 30 nm or less in plan view from the viewpoint of resolution limit. There is no particular lower limit to the width dimension of the fine pattern a, but 21 nm to 25 nm is preferred from the viewpoint of manufacturing process.

[0035] Furthermore, the shape of the fine pattern a in the peripheral region 211 may be, for example, a square in plan view. When the shape of the fine pattern a is a square in plan view, the side dimension of the fine pattern a is preferably 60 nm or less in plan view from the viewpoint of the resolution limit. There is no particular lower limit to the side dimension of the fine pattern a, but 35 nm to 50 nm is preferred from the viewpoint of the manufacturing process.

[0036] Furthermore, the shape of the fine pattern a in the peripheral region 211 may be, for example, a regular octagon in plan view. If the shape of the fine pattern a is a regular octagon in plan view, the shape of the fine pattern a is resolved as a circle on the photoreceptor, and thus the shape of the etching pattern on the photoreceptor can be made circular. Furthermore, if the shape of the fine pattern a is a regular octagon in plan view, the side length of the fine pattern a is preferably 50 nm or less in plan view, from the viewpoint of resolution limit. There is no particular lower limit to the side length of the fine pattern a, but from the viewpoint of manufacturing process, 35 nm to 50 nm is preferred.

[0037] Furthermore, the aperture ratio of the fine pattern a in the peripheral region 211 relative to the area of ​​the peripheral region 211 is preferably within the range of 1.0% to 50.0%, more preferably within the range of 5.0% to 40.0%, and even more preferably within the range of 10.0% to 30.0%. Furthermore, it is preferable that the aperture ratio of the fine pattern a in the peripheral region 211 relative to the area of ​​the peripheral region 211 is close to the aperture ratio of the main pattern region 20. Here, "aperture ratio (%) of the fine pattern a in the peripheral region 211" means the ratio of the area of ​​the fine pattern a formed within the peripheral region 211 to the area of ​​the peripheral region 211 (area of ​​fine pattern a / area of ​​peripheral region 211). In other words, an aperture ratio of "50%" for the fine pattern a in the peripheral region 211 means that the area where the fine pattern a is formed in the peripheral region 211 is "50%", and the area where the absorption layer 10 is formed in the peripheral region 211 (the remaining area) is "50%". Also, an aperture ratio of "1.0%" for the fine pattern a in the peripheral region 211 means that the area where the fine pattern a is formed in the peripheral region 211 is "1.0%", and the area where the absorption layer 10 is formed in the peripheral region 211 (the remaining area) is "99.0%".

[0038] Note that while accessory patterns used for alignment and other purposes are typically present in the surrounding region 211, these regions are not included in the above calculation (calculation of aperture ratio). If the aperture ratio of the fine pattern a in the peripheral region 211 is 1.0% or higher, the effect of improving dimensional uniformity within the photomask surface is achieved. Furthermore, if the aperture ratio of the fine pattern a in the peripheral region 211 is 50.0% or lower, resolution onto the photoreceptor (resist on the silicon wafer) can be prevented. In this embodiment, the formation area (area) of the main pattern region 20 is, for example, 104 mm × 132 mm. Furthermore, the line width of the transfer pattern in this embodiment is, for example, 75 nm.

[0039] According to the reflective photomask 200b of the first embodiment of the present disclosure described above, by forming a plurality of fine patterns a smaller than the minimum size transferred to the photoreceptor on the absorption layer 10 of the peripheral region 211 that demarcates the main pattern region 20 which is transferred to the resist (photoreceptor) on the silicon wafer for semiconductor circuit pattern formation, the difference in pattern density near the peripheral region 211 of the main pattern region 20 is mitigated, thereby suppressing local bias in developer concentration during the lithography process of the resist in transfer pattern formation and improving the in-plane uniformity of dimensions within the main pattern region 20. Furthermore, the in-plane uniformity of dimensions within the main pattern region 20 is improved, thereby increasing the transfer accuracy (transfer reliability) of the reflective photomass.

[0040] The resolution limit of EUV lithography, according to Rayleigh's formula, is approximately 14 nm (56 nm on the photomask) for an NA of 0.33 and approximately 8 nm (32 nm on the photomask) for an NA of 0.55. However, the minimum dimensions transferred to the photoreceptor (resist on the silicon wafer) can be adjusted by changing the pattern shape and illumination conditions. For example, regarding the shape of the fine pattern a, if it is linear, it is desirable from the viewpoint of increasing the aperture ratio that the aperture is perpendicular to the aperture direction of the absorption pattern 101 of the main pattern region 20. Furthermore, since the photomask becomes hot during EUV exposure, increasing the aperture of the absorption layer 10 reduces heat accumulation in the photomask, which is expected to extend the lifespan of the photomask.

[0041] The following describes in detail each layer constituting the reflective photomask blank 100 and the reflective photomask 200b according to the first embodiment of this disclosure. (substrate) The substrate 13 is the base layer for the reflective photomask 200b. A flat Si substrate or a synthetic quartz substrate can be used for the substrate 13. While titanium-doped low thermal expansion glass can be used for the substrate 13, this embodiment is not limited to these materials, as long as they have a low coefficient of thermal expansion.

[0042] (Conductive film) A conductive film 14 may be formed on the surface of the substrate 13 that does not have a reflective layer 12. The conductive film 14 is formed on the electrostatic chuck principle when the reflective photomask 200b is placed in the exposure machine. This is a film used for fixation. The conductive film 14 is generally composed of CrN, but any material made of a conductive material will suffice.

[0043] (reflective layer) The reflective layer 12 is a layer having a multilayer structure formed on the substrate 13, and is provided in the reflective photomask 200b to reflect EUV light (extreme ultraviolet light), which is the exposure light. The reflective layer 12 is composed of multiple reflective films made from combinations of materials with significantly different refractive indices for EUV light. For example, the reflective layer 12 can be formed by repeatedly stacking layers of combinations such as Mo (molybdenum) and Si (silicon), or Mo (molybdenum) and Be (beryllium), for about 40 cycles.

[0044] (protective layer) The protective layer 11 is a layer formed on the reflective layer 12 and functions as an etching stopper to prevent damage to the reflective layer 12 when the absorption pattern 101 is formed by etching. Typically, the protective layer 11 is made of a material that is resistant to dry etching performed when the pattern of the absorption layer 10 is formed, but depending on the material of the reflective layer 12 and the etching conditions, the protective layer 11 may be omitted.

[0045] (Absorption layer) The absorption layer 10 is a layer formed on the protective layer 11 and absorbs EUV light, which is the exposure light, in the reflective photomask 200b. The absorption layer 10 is also the layer that forms the absorption pattern 101, which is a fine pattern for transfer. By removing a portion of the absorption layer 10 of the reflective photomask blank 100 shown in Figure 1, that is, by patterning the absorption layer 10, the absorption pattern 101 of the reflective photomask 200b is formed. While conventional absorption layers 10 use Ta (tantalum) as the main material, the absorption layer 10 according to this embodiment is not limited to this, and can also use one or more metallic materials such as Pt (platinum), Nb (niobium), Ru (ruthenium), Ir (iridium), Ti (titanium), Cr (chromium), and In (indium). Furthermore, the absorption layer 10 may also contain non-metallic materials such as O (oxygen), N (nitrogen), B (boron), and C (carbon) in addition to the main metallic material.

[0046] (Light-blocking strip) When exposing a silicon wafer to form semiconductor integrated circuit patterns, multiple exposures are typically performed using a single reflective photomask. However, because the reflectivity of EUV light on the absorption layer 10 is usually around 0.5% to 2%, multiple exposures sometimes resulted in the outer edges of the chip being exposed. Therefore, for mass production of semiconductor integrated circuits using EUV lithography, it is necessary to provide a light-shielding band 22 on the outer edge of the chip on the mask that has a higher light-shielding capability against EUV light than a normal absorption layer. In reflective photomasks, the light-shielding band 22 is often formed by carving into the reflective layer 12, which is formed by a multilayer film.

[0047] (Second embodiment) The basic configuration of the reflective photomask 201b according to the second embodiment of this disclosure will be explained with reference to Figures 6 and 7. Figure 6 is a cross-sectional view illustrating an example configuration of a reflective photomask 201b according to the second embodiment of this disclosure. As shown in Figure 6, in the main pattern region 20 of the reflective photomask 201b according to the second embodiment of this disclosure, a reflective layer 12, a protective layer 11, and an absorption pattern 101 are stacked in this order on one side of the substrate 13. Note that the absorption pattern 101 is The absorption layer 10 is formed by patterning. A conductive film 14 may also be formed on the other surface of the substrate.

[0048] Figure 7 is a plan view of a reflective photomask 201b according to a second embodiment of the present disclosure. A single reflective photomask 201b has one or more main pattern regions 20 formed on it for forming a semiconductor integrated circuit pattern on a silicon wafer. Each main pattern region 20 is demarcated by a peripheral region 21 that does not contribute to the formation of the semiconductor integrated circuit pattern. The peripheral region 21 is covered with an absorption layer 10, except for some accessory patterns, to demarcate chips on the silicon wafer, and does not contribute to transfer. Furthermore, a light-shielding band 22 is formed at the edge of the desired exposure region at the outermost periphery of the peripheral region 21. The light-shielding band 22 is surrounded by an outer peripheral region 23.

[0049] Thus, the reflective photomask 201b according to the second embodiment of this disclosure has a semiconductor within the main pattern region 20 of the conventional reflective photomask 200a shown in Figures 2 and 4. A main pattern non-formation region 241 is formed, which is an area where an integrated circuit pattern (transfer pattern) is not formed, and the area of ​​the main pattern non-formation region 241 is 50 μm in plan view. 2 In addition, a plurality of fine patterns a having a width smaller than the minimum width dimension that is transferred to the photoreceptor (resist on the silicon wafer) by exposure are formed in the main pattern non-formed region 241. Furthermore, multiple fine patterns a may be in contact with the main pattern region 20 as long as they are not transferred to the photoreceptor (resist on the silicon wafer) by exposure.

[0050] More specifically, the reflective photomask 201b according to the second embodiment of this disclosure is a reflective photomask manufactured using the reflective photomask blank 100 according to the first embodiment of this disclosure, comprising a substrate 13, a reflective layer 12 formed on the substrate 13 and having a multilayer structure that reflects EUV light, and an absorbing layer 10 formed on the reflective layer 12 and absorbing EUV light, wherein the absorbing layer 10 has a main pattern region 20 on which a transfer pattern is formed that is transferred to a photoreceptor (resist on a silicon wafer) by exposure, and a main pattern non-formed region 241 provided within the main pattern region 20 and in which no transfer pattern is formed, and the area of ​​the main pattern non-formed region 241 is 50 μm in plan view. 2 The above describes a reflective photomask having at least a plurality of fine patterns a in the main pattern non-formed region 241, each having a width dimension smaller than the minimum width dimension transferred to the photoreceptor (resist on a silicon wafer) by exposure.

[0051] Here, "a fine pattern a having a width smaller than the minimum width transferred to the photoreceptor by exposure" means a fine pattern having a line width that is not resolved on the photoreceptor (resist on a silicon wafer), i.e., a line width below the resolution limit. The typical resolution limit line width in a single exposure using a conventional exposure apparatus is 32 nm to 56 nm. Furthermore, the fine pattern a in this embodiment is a pattern formed in such a way that the surface of the reflective layer 12 or the surface of the protective layer 11 is exposed, similar to the transfer pattern formed within the main pattern region 20.

[0052] The shape of the fine pattern a of the reflective photomask 201b according to the second embodiment of this disclosure may be the same as the shape of the fine pattern a of the reflective photomask 200b according to the first embodiment of this disclosure. In other words, the shape of the fine pattern a in the main pattern non-formed region 241 may be, for example, a straight line in plan view. If the shape of the fine pattern a is a straight line in plan view, the aperture ratio can be easily increased by making the aperture direction of the fine pattern a perpendicular to the aperture direction of the absorption pattern 101 in the main pattern region 20. Furthermore, if the shape of the fine pattern a is a straight line in plan view, the width dimension of the fine pattern a From the viewpoint of resolution limits, it is preferable that the nanometer is 30 nm or less in plan view. While there are no particular restrictions on the lower limit of the width dimension of the fine pattern a, 21 nm to 25 nm is preferred from a manufacturing process perspective.

[0053] Furthermore, the shape of the fine pattern a in the main pattern non-formation region 241 may be, for example, a square in plan view. When the shape of the fine pattern a is a square in plan view, the side dimension of the fine pattern a is preferably 60 nm or less in plan view from the viewpoint of resolution limit. There is no particular lower limit to the side dimension of the fine pattern a, but 35 nm to 50 nm is preferred from the viewpoint of manufacturing process.

[0054] Furthermore, the shape of the fine pattern a in the main pattern non-formed region 241 may be, for example, a regular octagon in plan view. If the shape of the fine pattern a is a regular octagon in plan view, the shape of the fine pattern a is resolved as a circle on the photoreceptor, and thus the shape of the etching pattern on the photoreceptor can be made circular. Furthermore, if the shape of the fine pattern a in the main pattern non-formation region 241 is a regular octagon in plan view, the side dimension of the fine pattern a is preferably 50 nm or less in plan view from the viewpoint of resolution limit. There is no particular lower limit to the side dimension of the fine pattern a, but from the viewpoint of manufacturing process, 35 nm to 50 nm is preferred.

[0055] Furthermore, the aperture ratio, etc., of the fine pattern a of the reflective photomask 201b according to the second embodiment of this disclosure may be the same as the aperture ratio, etc., of the fine pattern a of the reflective photomask 200b according to the first embodiment of this disclosure. In other words, the aperture ratio of the fine pattern a in the main pattern non-formed region 241 relative to the area of ​​the main pattern non-formed region 241 is preferably in the range of 1.0% to 50.0%, more preferably in the range of 5.0% to 40.0%, and even more preferably in the range of 10.0% to 30.0%. Furthermore, it is preferable that the aperture ratio of the fine pattern a in the non-main pattern region 241 relative to the area of ​​the non-main pattern region 241 is close to the aperture ratio of the main pattern region 20.

[0056] Here, "the aperture ratio (%) of the fine pattern a in the main pattern non-formation region 241" means the ratio of the area of ​​the fine pattern a formed within the main pattern non-formation region 241 to the area of ​​the main pattern non-formation region 241 (area of ​​fine pattern a / area of ​​the main pattern non-formation region 241). In other words, an aperture ratio of "50%" for the fine pattern a in the main pattern non-formation region 241 means that the formation area (area) of the fine pattern a in the main pattern non-formation region 241 is "50%", and the formation area (remaining area) of the absorption layer 10 in the main pattern non-formation region 241 is "50%". Also, an aperture ratio of "1.0%" for the fine pattern a in the main pattern non-formation region 241 means that the formation area (area) of the fine pattern a in the main pattern non-formation region 241 is "1.0%", and the formation area (remaining area) of the absorption layer 10 in the main pattern non-formation region 241 is "99.0%". If the aperture ratio of the fine pattern a in the main pattern non-formation region 241 is 1.0% or higher, the effect of improving dimensional uniformity within the photomask surface is achieved. Furthermore, if the aperture ratio of the fine pattern a in the main pattern non-formation region 241 is 50.0% or lower, resolution onto the photoreceptor (resist on the silicon wafer) can be prevented.

[0057] Furthermore, although the peripheral region 21 of the reflective photomask 201b according to this embodiment does not have a fine pattern a formed thereon, it is more preferable if a fine pattern a is formed thereon. In this embodiment, the formation area (area) of the main pattern region 20 is, for example, 104 mm × 132 mm. Also, the line width of the transfer pattern in this embodiment is, for example, 7 It is 5nm.

[0058] 50 μm within the main pattern area 20 2If there are areas where the main pattern is not formed, a difference in pattern density will occur between these areas and nearby patterns, which can lead to a difference in developer concentration and potentially worsen the in-plane uniformity of dimensions within the main pattern area 20. However, within the main pattern region 20, the area is 50 μm in plan view. 2 Even when there are areas where the main pattern is not formed, the effects of this disclosure can be obtained by forming multiple fine patterns a, which are smaller than the minimum size transferred to the photoreceptor, in the areas where the main pattern is not formed.

[0059] In other words, the area of ​​the region where the main pattern is not formed is 50 μm in plan view. 2 Even in the above cases, according to the reflective photomask 201b of the second embodiment of this disclosure described above, by forming a plurality of fine patterns a smaller than the minimum dimensions transferred to the photoreceptor on the absorption layer 10 of the non-main pattern region formed within the main pattern region 20 that is transferred to the resist (photoreceptor) on the silicon wafer for semiconductor circuit pattern formation, the difference in pattern density near the non-main pattern region 241 of the main pattern region 20 is mitigated, thereby suppressing local bias in developer concentration during the lithography process of the resist in transfer pattern formation and improving in-plane uniformity of dimensions within the main pattern region 20.

[0060] Furthermore, the in-plane uniformity of dimensions within the main pattern region 20 is improved, thereby increasing the transfer accuracy (transfer reliability) of the reflective photomass. The resolution limit of EUV lithography, according to Rayleigh's formula, is approximately 14 nm (56 nm on the photomask) for an NA of 0.33 and approximately 8 nm (32 nm on the photomask) for an NA of 0.55. However, the minimum dimensions transferred to the photoreceptor (resist on the silicon wafer) can be adjusted by changing the pattern shape and illumination conditions. For example, regarding the shape of the fine pattern a, if it is linear, it is desirable from the viewpoint of increasing the aperture ratio that the aperture is perpendicular to the aperture direction of the absorption pattern 101 of the main pattern region 20. Furthermore, since the photomask becomes hot during EUV exposure, increasing the aperture of the absorption layer 10 reduces heat accumulation in the photomask, which is expected to extend the lifespan of the photomask.

[0061] Since the layers constituting the reflective photomask blank 100 and reflective photomask 201b according to the second embodiment of this disclosure are the same as the layers constituting the reflective photomask blank 100 and reflective photomask 200b according to the first embodiment of this disclosure, a detailed explanation thereof is omitted here.

[0062] (Modifications of the first and second embodiments) In the first embodiment, a configuration was described in which the fine pattern a is a pattern formed such that the surface of the reflective layer 12 or the surface of the protective layer 11 is exposed, similar to the transfer pattern formed within the main pattern region 20, but the disclosure is not limited thereto. For example, the transfer pattern formed within the main pattern region 20 may be a pattern formed such that the surface of the reflective layer 12 or the surface of the protective layer 11 is exposed, while the fine pattern a may be a pattern formed so that the surface of the reflective layer 12 or the surface of the protective layer 11 is not exposed. Figure 8 shows a configuration (a modified example of the first embodiment) in which the transfer pattern formed within the main pattern region 20 is a pattern formed such that the surface of the protective layer 11 is exposed, and the fine pattern a is a pattern formed so that the surface of the protective layer 11 is not exposed.

[0063] In the second embodiment, the fine pattern a is formed such that the surface of the reflective layer 12 or the surface of the protective layer 11 is exposed, similar to the transfer pattern formed within the main pattern region 20. While the patterns described have been explained, this disclosure is not limited to them. For example, the transfer pattern formed within the main pattern region 20 may be a pattern formed such that the surface of the reflective layer 12 or the surface of the protective layer 11 is exposed, while the fine pattern a may be a pattern formed so that the surface of the reflective layer 12 or the surface of the protective layer 11 is not exposed. Figure 9 shows a configuration (a modified example of the second embodiment) in which the transfer pattern formed within the main pattern region 20 is a pattern formed such that the surface of the protective layer 11 is exposed, and the fine pattern a is a pattern formed so that the surface of the protective layer 11 is not exposed.

[0064] Furthermore, in the first embodiment, the depth of the fine pattern a is preferably 40% or more of the thickness of the absorption layer 10 in the peripheral region 211, and more preferably 60% or more. Of course, it is most preferable that the depth of the fine pattern a is 100% of the thickness of the absorption layer 10 in the peripheral region 211, that is, that the fine pattern a is formed such that the surface of the reflective layer 12 or the surface of the protective layer 11 is exposed. In the second embodiment, the depth of the fine pattern a is preferably 40% or more of the thickness of the absorption layer 10 in the main pattern non-formed region 241, and more preferably 60% or more. Of course, it is most preferable when the depth of the fine pattern a is 100% of the thickness of the absorption layer 10 in the main pattern non-formed region 241, that is, when the fine pattern a is formed such that the surface of the reflective layer 12 or the surface of the protective layer 11 is exposed.

[0065] (Examples) The following describes an example of the reflective photomask 200b according to the first embodiment of this disclosure.

[0066] [Example 1] As shown in Figure 10, the method for fabricating a reflective photomask involves a substrate 13 made of low thermal expansion glass with added Ti (titanium), a reflective layer 12 made of Mo (molybdenum) and Si (silicon) laminated on one side of the substrate 13, a protective layer 11 made of Ru (ruthenium) laminated on the reflective layer 12, and TaO (tantalum oxide) and TaN (tar nitride) laminated on the protective layer 11. It comprises an absorption layer 10 made of (aluminum) and a conductive film 1 made of CrN (chromium nitride) on the other surface. A reflective photomask blank 100 equipped with 4 was prepared. Subsequently, as shown in Figure 10, a positive-type chemically amplified resist (XFP- 355: (Manufactured by Fujifilm Electronic Materials Co., Ltd.) Spin-coated to 100nm A resist film 15 was formed by coating and baking at 110°C for 10 minutes. Subsequently, as shown in Figure 11, an electron beam lithography (EB) system is used with known lithography techniques. Exposure using M7500T (manufactured by Newflare Technology Co., Ltd.) followed by alkaline water solution Developing was performed using a solution to simultaneously pattern the positive-type chemically amplified resist in the main pattern region 20 and the peripheral region 211.

[0067] Subsequently, as shown in Figure 12, dry etching was performed using fluorine-based gas and chlorine-based gas to simultaneously form the absorption pattern 101 in the main pattern region 20 and the fine pattern a in the peripheral region 211. After removing the resist residue by washing, a light-shielding band 22 was formed again using known lithography techniques to obtain a reflective photomask 200b as shown in Figures 5 and 13, which contained absorption patterns 101 with a width dimension of 75 nm in nine main pattern regions 20. In Example 1, the shape of the fine pattern a formed in the peripheral region 211 was set to a linear shape, the width dimension of the fine pattern a was set to 25 nm, the pitch of the fine pattern a (distance between the centers of the fine pattern a) was set to 100 nm, and the aperture ratio (%) of the fine pattern a was set to 25.0%.

[0068] For the reflective photomask 200b, 81 linear patterns formed with a width dimension of 75 nm within the main pattern region 20 were photographed using a scanning electron microscope for length measurement (LWM9045: manufactured by VISTEC). The actual dimensions of the line width at each location were measured from the images, and 3σ was calculated. It was defined as uniformity. If the in-plane dimensional uniformity was 1.00 nm or less, it was judged as "○ (Pass)" as good uniformity; if the in-plane dimensional uniformity was between 1.00 nm and 1.50 nm, it was judged as "△ (Pass)" as usable; and if the in-plane uniformity was greater than 1.50 nm, it was judged as "× (Fail)" as poor uniformity. The dimensional in-plane uniformity of the reflective photomask 200b according to Example 1 was 0.88 nm.

[0069] [Example 2] A reflective photomask 200b according to Example 2 was obtained in the same manner as the reflective photomask 200b according to Example 1, except that a linear fine pattern a (aperture ratio 10.0%) with a width of 25 nm and a pitch of 250 nm was formed in the peripheral region 211 when patterning the resist in the main pattern region 20. When the in-plane dimensional uniformity was measured in the same manner as in Example 1, the in-plane dimensional uniformity of the reflective photomask 200b according to Example 2 was 0.89 nm.

[0070] [Example 3] A reflective photomask 200b according to Example 3 was obtained in the same manner as the reflective photomask 200b according to Example 1, except that a linear fine pattern a (aperture ratio 2.5%) with a width of 25 nm and a pitch of 1000 nm was formed in the peripheral region 211 when patterning the resist in the main pattern region 20. When the in-plane dimensional uniformity was measured in the same manner as in Example 1, the in-plane dimensional uniformity of the reflective photomask 200b according to Example 3 was 0.91 nm.

[0071] [Example 4] A reflective photomask 200b according to Example 4 was obtained in the same manner as the reflective photomask 200b according to Example 1, except that a linear fine pattern a (aperture ratio 1.3%) with a width of 25 nm and a pitch of 2000 nm was formed in the peripheral region 211 when patterning the resist in the main pattern region 20. When the in-plane dimensional uniformity was measured in the same manner as in Example 1, the in-plane dimensional uniformity of the reflective photomask 200b according to Example 4 was 0.95 nm.

[0072] [Example 5] A reflective photomask 200b according to Example 5 was obtained in the same manner as the reflective photomask 200b according to Example 1, except that a linear fine pattern a (aperture ratio 0.8%) with a width of 25 nm and a pitch of 3000 nm was formed in the peripheral region 211 when patterning the resist in the main pattern region 20. When the in-plane dimensional uniformity was measured in the same manner as in Example 1, the in-plane dimensional uniformity of the reflective photomask 200b according to Example 5 was 1.08 nm.

[0073] [Example 6] A reflective photomask 200b according to Example 6 was obtained in the same manner as the reflective photomask 200b according to Example 1, except that a linear fine pattern a (aperture ratio 3.0%) with a width of 30 nm and a pitch of 1000 nm was formed in the peripheral region 211 when patterning the resist in the main pattern region 20. When the dimensional plane uniformity was measured in the same manner as in Example 1, the reflection according to Example 6 was obtained. The dimensional in-plane uniformity of the type photomask 200b was 0.95 nm.

[0074] [Example 7] A reflective photomask 200b according to Example 7 was obtained in the same manner as the reflective photomask 200b according to Example 1, except that a linear fine pattern a (aperture ratio 1.5%) with a width of 30 nm and a pitch of 2000 nm was formed in the peripheral region 211 when patterning the resist in the main pattern region 20. When the in-plane dimensional uniformity was measured in the same manner as in Example 1, the in-plane dimensional uniformity of the reflective photomask 200b according to Example 7 was 0.93 nm.

[0075] [Example 8] A reflective photomask 200b according to Example 8 was obtained in the same manner as the reflective photomask 200b according to Example 1, except that a linear fine pattern a (aperture ratio 1.0%) with a width of 30 nm and a pitch of 3000 nm was formed in the peripheral region 211 when patterning the resist in the main pattern region 20. When the in-plane dimensional uniformity was measured in the same manner as in Example 1, the in-plane dimensional uniformity of the reflective photomask 200b according to Example 8 was 0.93 nm.

[0076] [Example 9] A reflective photomask 200b according to Example 9 was obtained in the same manner as the reflective photomask 200b according to Example 1, except that a square fine pattern a (aperture ratio 2.3%) with sides of 45 nm and a pitch of 300 nm was formed in the peripheral region 211 when patterning the resist in the main pattern region 20. When the in-plane dimensional uniformity was measured in the same manner as in Example 1, the in-plane dimensional uniformity of the reflective photomask 200b according to Example 9 was 0.93 nm.

[0077] [Example 10] A reflective photomask 200b according to Example 10 was obtained in the same manner as the reflective photomask 200b according to Example 1, except that a square fine pattern a (aperture ratio 1.3%) with sides of 45 nm and a pitch of 400 nm was formed in the peripheral region 211 when patterning the resist in the main pattern region 20. When the in-plane dimensional uniformity was measured in the same manner as in Example 1, the in-plane dimensional uniformity of the reflective photomask 200b according to Example 10 was 0.99 nm.

[0078] [Example 11] A reflective photomask 200b according to Example 11 was obtained in the same manner as the reflective photomask 200b according to Example 1, except that a square fine pattern a (aperture ratio 0.8%) with sides of 45 nm and a pitch of 500 nm was formed in the peripheral region 211 when patterning the resist in the main pattern region 20. When the in-plane dimensional uniformity was measured in the same manner as in Example 1, the in-plane dimensional uniformity of the reflective photomask 200b according to Example 11 was 1.15 nm.

[0079] [Example 12] A reflective photomask 200b according to Example 12 was obtained in the same manner as the reflective photomask 200b according to Example 1, except that a square fine pattern a (aperture ratio 2.8%) with sides of 50 nm and a pitch of 300 nm was formed in the peripheral region 211 when patterning the resist in the main pattern region 20. When the in-plane dimensional uniformity was measured in the same manner as in Example 1, the in-plane dimensional uniformity of the reflective photomask 200b according to Example 12 was 0.90 nm.

[0080] [Example 13] A reflective photomask 200b according to Example 13 was obtained in the same manner as the reflective photomask 200b according to Example 1, except that a square fine pattern a (aperture ratio 1.6%) with sides of 50 nm and a pitch of 400 nm was formed in the peripheral region 211 when patterning the resist in the main pattern region 20. When the in-plane dimensional uniformity was measured in the same manner as in Example 1, the in-plane dimensional uniformity of the reflective photomask 200b according to Example 13 was 0.95 nm.

[0081] [Example 14] A reflective photomask 200b according to Example 14 was obtained in the same manner as the reflective photomask 200b according to Example 1, except that a square fine pattern a (aperture ratio 1.0%) with sides of 50 nm and a pitch of 500 nm was formed in the peripheral region 211 when patterning the resist in the main pattern region 20. When the in-plane dimensional uniformity was measured in the same manner as in Example 1, the in-plane dimensional uniformity of the reflective photomask 200b according to Example 14 was 0.96 nm.

[0082] [Example 15] A reflective photomask 200b according to Example 15 was obtained in the same manner as the reflective photomask 200b according to Example 1, except that a square fine pattern a (aperture ratio 1.4%) with sides of 60 nm and a pitch of 500 nm was formed in the peripheral region 211 when patterning the resist in the main pattern region 20. When the in-plane dimensional uniformity was measured in the same manner as in Example 1, the in-plane dimensional uniformity of the reflective photomask 200b according to Example 15 was 0.94 nm.

[0083] [Example 16] A reflective photomask 200b according to Example 16 was obtained in the same manner as the reflective photomask 200b according to Example 1, except that a rectangular fine pattern a (aperture ratio 3.1%) with a short dimension of 50 nm, a long dimension of 100 nm, and a pitch of 400 nm was formed in the peripheral region 211 when patterning the resist in the main pattern region 20. When the in-plane dimensional uniformity was measured in the same manner as in Example 1, the in-plane dimensional uniformity of the reflective photomask 200b according to Example 16 was 0.94 nm.

[0084] [Example 17] A reflective photomask 200b according to Example 17 was obtained in the same manner as the reflective photomask 200b according to Example 1, except that a fine octagonal pattern a (aperture ratio 3.0%) with sides of 20 nm (dimension 48.3 nm) and a pitch of 300 nm was formed in the peripheral region 211 when patterning the resist in the main pattern region 20. When the in-plane dimensional uniformity was measured in the same manner as in Example 1, the in-plane dimensional uniformity of the reflective photomask 200b according to Example 17 was 0.95 nm.

[0085] [Example 18] A reflective photomask 200b according to Example 18 was obtained in the same manner as the reflective photomask 200b according to Example 1, except that a fine octagonal pattern a (aperture ratio 1.6%) with sides of 20 nm (dimension 48.3 nm) and a pitch of 400 nm was formed in the peripheral region 211 when patterning the resist in the main pattern region 20. When the in-plane dimensional uniformity was measured in the same manner as in Example 1, the in-plane dimensional uniformity of the reflective photomask 200b according to Example 18 was 0.98 nm.

[0086] [Example 19] When patterning the resist in the main pattern area 20, the surrounding area 211 has a side length of 20n A reflective photomask 200b according to Example 19 was obtained in the same manner as the reflective photomask 200b according to Example 1, except that a fine pattern a (aperture ratio 0.9%) of a regular octagon with dimensions m (48.3 nm) and a pitch of 500 nm was formed. When the in-plane dimensional uniformity was measured in the same manner as in Example 1, the in-plane dimensional uniformity of the reflective photomask 200b according to Example 19 was 1.18 nm.

[0087] [Comparative Example 1] A reflective photomask 200a according to Comparative Example 1 was obtained in the same manner as the reflective photomask 200b according to Example 1, except that a fine pattern a was not formed in the peripheral region 21 (aperture ratio 0.0%) when patterning the resist in the main pattern region 20. When the in-plane dimensional uniformity was measured in the same manner as in Example 1, the in-plane dimensional uniformity of the reflective photomask 200a according to Comparative Example 1 was 1.52 nm.

[0088] The following describes an example of the reflective photomask 201b according to the second embodiment of this disclosure. [Example 20] As a method for manufacturing a reflective photomask, as shown in FIG. 14, a substrate 13 made of a low thermal expansion glass added with Ti (titanium), a reflective layer 12 made of Mo (molybdenum) and Si (silicon) laminated on one surface of the substrate 13, a protective layer 11 made of Ru (ruthenium) laminated on the reflective layer 12, and an absorption layer 10 made of TaO (tantalum oxide) and TaN (tantalum nitride) laminated on the protective layer 11 are provided. A conductive film 14 made of CrN (chromium nitride) is provided on the other surface, and a reflective photomask blank 100 is prepared. Then, as shown in FIG. 14, a positive chemically amplified resist (XFP-355: manufactured by Fuji Film Electronic Materials Co., Ltd.) is spin-coated to a thickness of 100 nm on the exposed surface of the absorption layer 10, and baked at 110 °C for 10 minutes to form a resist film 15. Thereafter, as shown in FIG. 15, using a known lithography technique, exposure is performed with an electron beam drawing apparatus (EB-M7500T: manufactured by NuFlare Technology Inc.), and subsequent development is performed using an alkaline aqueous solution to simultaneously perform patterning of the positive chemically amplified resist for the main pattern region 20 and the main pattern non-formation region 241. Then, as shown in FIG. 16, dry etching is performed using a fluorine-based gas and a chlorine-based gas to simultaneously form an absorption pattern 101 in the main pattern region 20 and a fine pattern a in the main pattern non-formation region 241. After removing the resist residue by cleaning, a light-shielding band 22 is formed again using a known lithography technique, so that two main pattern non-formation regions 241 and an absorption pattern 101 with a dimension of 75 nm are included in one main pattern region 20, and the main pattern non-formation regions 241 are each 55 μm, as shown in FIGS. 7 and 17, a reflective photomask 201b is obtained.

[0089]

[0089] 2 2 Furthermore, in Example 20, when patterning the resist in the main pattern region 20, a fine square pattern a (open) with sides of 45 nm and a pitch of 300 nm was formed in the main pattern non-formed region 241. Except for forming a 2.3% aperture, it is the same as the reflective photomask 200b according to Example 1. Thus, a reflective photomask 201b according to Example 20 was obtained. When the in-plane dimensional uniformity was measured in the same manner as in Example 1, the in-plane dimensional uniformity of the reflective photomask 201b according to Example 20 was 0.96 nm.

[0090] [Comparative Example 2] A reflective photomask 200a according to Comparative Example 2 was obtained in the same manner as the reflective photomask 200b according to Example 1, except that a fine pattern a was not formed in the main pattern non-formed region 241 (aperture ratio 0.0%) when patterning the resist in the main pattern region 20. When the in-plane dimensional uniformity was measured in the same manner as in Example 1, the in-plane dimensional uniformity of the reflective photomask 200a according to Comparative Example 2 was 1.56 nm.

[0091] [Table 1]

[0092] Table 1 shows the evaluation conditions and in-plane dimensional uniformity in the examples and comparative examples. Peripheral region 21 By providing a fine pattern a, the dimensional uniformity within the main pattern area 20 is improved, and it was confirmed that further improvement can be expected if the aperture ratio of the fine pattern a is 1.0% or higher. Furthermore, if the aperture ratio exceeds 50%, the pattern will be transferred to the photoreceptor during exposure, rendering the absorption layer ineffective. Furthermore, generally speaking, patterns with large, regularly spaced apertures have a higher transfer margin due to the effects of diffracted light. Therefore, when the width dimension of a linear shape exceeds 30 nm, the width dimension of a square exceeds 60 nm, and the width dimension of a regular octagon exceeds 50 nm, the likelihood of the pattern being transferred to the photoreceptor increases depending on the exposure conditions and pattern arrangement. While the uniformity within the plane of dimensions is improved even with a rectangular fine pattern a, the likelihood of the pattern being transferred to the photoreceptor is higher compared to squares and regular octagons.

[0093] In the comparative example, Figure 18 shows a cross-sectional view of the boundary between the main pattern region 20 and the peripheral region 21 after patterning the resist (photoreceptor) by development. In the resist (photoreceptor) development process, a localized difference in developer concentration occurs at the boundary between the main pattern region 20, where the developer is consumed by the dissolution of the resist (photoreceptor), and the peripheral region 21, where the developer is not consumed. This is thought to cause fluctuations in the dimensions of the finished resist, resulting in a larger dimensional difference between the central part of the main pattern region 20 and the peripheral region 21. Therefore, by forming the fine pattern a in the peripheral region 211 in the embodiments of this disclosure, it is possible to mitigate the effects of localized differences in developer concentration, thereby improving dimensional uniformity.

[0094] Furthermore, within the main pattern area 20, there is a 50 μm area where the developer is not consumed. 2 A similar phenomenon has been observed in a conventional reflective photomask 201a (see Figure 19) which has the above area and in which a main pattern non-formation region 24 that does not have a fine pattern a is arranged. In contrast, it has a fine pattern a and is 50 μm 2 By forming a main pattern non-formation region 241 having the above area, it is possible to mitigate the effects of localized differences in developer concentration. Therefore, in the embodiments of this disclosure, forming it in the main pattern non-formation region 241 having a fine pattern a improves in-plane dimensional uniformity.

[0095] Furthermore, for example, the reflective photomask and the method for manufacturing the reflective photomask according to this disclosure can have the following configuration. (1) circuit board and A reflective layer that reflects EUV light and has a multilayer structure is formed on the substrate, The reflective layer comprises an absorbing layer formed on the reflective layer that absorbs EUV light, The absorption layer has a main pattern region on which a transfer pattern is formed to be transferred to the photoreceptor by exposure, and a peripheral region that demarcates the main pattern region. A reflective photomask characterized in that the peripheral region has at least a plurality of fine patterns having a width dimension smaller than the minimum width dimension transferred to the photoreceptor by exposure. (2) circuit board and A reflective layer that reflects EUV light and has a multilayer structure is formed on the substrate, The reflective layer comprises an absorbing layer formed on the reflective layer that absorbs EUV light, The absorption layer has a main pattern region on which a transfer pattern is formed to be transferred to the photoreceptor by exposure, and a main pattern non-formed region provided within the main pattern region, which is a region on which the transfer pattern is not formed. The area of ​​the region where the main pattern is not formed is 50 μm in plan view. 2 That's all. A reflective photomask characterized in that the main pattern non-formed region has at least a plurality of fine patterns having a width dimension smaller than the minimum width dimension transferred to the photoreceptor by exposure. (3) The reflective photomask according to (1) or (2) above, characterized in that the shape of the fine pattern is linear in plan view. (4) The reflective photomask according to (3) above, characterized in that the width dimension of the fine pattern is 30 nm or less in a plan view. (5) The reflective photomask according to (1) or (2) above, characterized in that the shape of the fine pattern is square in plan view. (6) The reflective photomask according to (5) above, characterized in that the dimension of one side of the fine pattern is 60 nm or less in a plan view. (7) The reflective photomask according to (1) or (2) above, characterized in that the shape of the fine pattern is a regular octagon in plan view. (8) The reflective photomask according to (7) above, characterized in that the dimension of one side of the fine pattern is 50 nm or less in a plan view. (9) The reflective photomask according to (1) above, characterized in that the aperture ratio of the fine pattern in the peripheral region with respect to the area of ​​the peripheral region (area of ​​the fine pattern in the peripheral region / area of ​​the peripheral region) is within the range of 1.0% to 50.0%. (10) The reflective photomask according to (2) above, characterized in that the aperture ratio of the fine pattern in the region where the main pattern is not formed (area of ​​the fine pattern in the region where the main pattern is not formed / area of ​​the region where the main pattern is not formed) is within the range of 1.0% to 50.0%. (11) A reflective photomask according to any one of (1) to (10) above, characterized in that a protective layer is provided between the reflective layer and the absorbing layer. (12) A method for manufacturing a reflective photomask according to claim 1, The absorption layer comprises a main pattern region on which a transfer pattern to be transferred to a photoreceptor by exposure is formed, and a peripheral region that demarcates the main pattern region. A method for manufacturing a reflective photomask, characterized in that the peripheral region has at least a plurality of fine patterns having a width dimension smaller than the minimum width dimension transferred to the photoreceptor by exposure. (13) A method for manufacturing a reflective photomask according to claim 2, The absorption layer comprises a main pattern region on which a transfer pattern is formed to be transferred to a photoreceptor by exposure, and a main pattern non-formation region provided within the main pattern region, on which the transfer pattern is not formed. The area of ​​the region where the main pattern is not formed is 50 μm in plan view. 2 That's all. A method for manufacturing a reflective photomask, characterized in that the main pattern non-formed region has at least a plurality of fine patterns having a width dimension smaller than the minimum width dimension transferred to the photoreceptor by exposure. [Industrial applicability]

[0096] The reflective photomask according to the present invention can be suitably used in the manufacturing process of semiconductor integrated circuits and the like to form fine patterns by EUV exposure. [Explanation of Symbols]

[0097] 10. Absorption layer 11...protective layer 12...Reflection layer 13... Circuit board 14. Conductive film 15. Resist film 100...Reflective Photomask Blanks 101... Absorption Pattern 20...Main pattern area 21... Peripheral area 211...Peripheral region having fine pattern a 22. Shading band 23...outer area 24···50μm 2 Main pattern non-formed region having the above area 241...Has a fine pattern a and is 50 μm 2 Main pattern non-formed region having the above area 200a, 200b, 201a, 201b... Reflective photomasks a... fine pattern

Claims

1. circuit board and A reflective layer formed on the substrate and having a multilayer structure that reflects EUV light, The reflective layer comprises an absorbing layer formed on the reflective layer that absorbs EUV light, The absorption layer has a main pattern region on which a transfer pattern is formed to be transferred to the photoreceptor by exposure, and a main pattern non-formed region provided within the main pattern region, which is a region on which the transfer pattern is not formed. The area of ​​the region where the main pattern is not formed is 50 μm in plan view. ２ That's all. A reflective photomask characterized in that the main pattern non-formed region has at least a plurality of fine patterns having a width dimension smaller than the minimum width dimension transferred to the photoreceptor by exposure.

2. The reflective photomask according to claim 1, characterized in that the aperture ratio of the fine pattern in the region where the main pattern is not formed (area of ​​the fine pattern in the region where the main pattern is not formed / area of ​​the region where the main pattern is not formed) is within the range of 1.0% to 50.0%.

3. A method for manufacturing a reflective photomask according to claim 1, The absorption layer comprises a main pattern region on which a transfer pattern is formed to be transferred to a photoreceptor by exposure, and a main pattern non-formation region provided within the main pattern region, on which the transfer pattern is not formed. The area of ​​the region where the main pattern is not formed is 50 μm in plan view. ２ That's all. A method for manufacturing a reflective photomask, characterized in that the main pattern non-formed region has at least a plurality of fine patterns having a width dimension smaller than the minimum width dimension transferred to the photoreceptor by exposure.

Images