MASK BLANK SUBSTRATE, SUBSTRATE WITH MULTILAYER REFLECTIVE FILM, REFLECTIVE MASK BLANK, REFLECTIVE MASK, AND METHOD FOR MANUFACTURING SEMICONDUCTOR DEVICE

Abstract

To provide a mask blank substrate that can satisfy required characteristics as a mask blank substrate while having a non-uniform portion therein, thereby contributing to enhancement in production yield.SOLUTION: A mask blank substrate includes two opposing main surfaces, comprises a glass material containing SiO2 and TiO2, and has a first region in one main surface. The first region is a region within a 132 mm×104 mm square including a center portion in the one main surface, and is a region extending from the one main surface toward the other main surface up to a position of 500 μm in depth. An inner region of the substrate excluding the first region has a locally non-uniform portion. A ratio (Ti / Si) of Ti content to Si content in the non-uniform portion differs from Ti / Si of the inner region excluding the non-uniform portion by 0.25% or more, and the variation of Ti content in the inner region of the substrate excluding the first region and the non-uniform portion is 0.06 mass% or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a mask blank substrate that is suitably used for producing an exposure mask used in the production of a semiconductor device, a substrate with a multilayer reflective film, a reflective mask blank, a reflective mask, and a method for producing a semiconductor device. [Background technology]

[0002] Exposure equipment used in semiconductor device manufacturing is evolving as the wavelength of the light source is gradually shortened. In order to achieve finer pattern transfer, EUV lithography using extreme ultraviolet light (EUV: Extreme Ultra Violet, hereafter sometimes referred to as EUV light) with a wavelength of around 13.5 nm has been developed. In EUV lithography, a reflective mask is used because there are few materials that are transparent to EUV light.

[0003] As substrates suitable for use in such reflective masks for EUV lithography and reflective mask blanks for producing such masks, materials with low thermal expansion are required so that distortion does not occur even when irradiated with EUV light, and low thermal expansion glass has been investigated.

[0004] Patent Document 1 describes TiO, which is produced by flame hydrolysis of glass-forming raw materials, as a material for such a substrate. 2 Silica glass containing TiO 2 -SiO 2 Glass) and TiO 2 Silica glass having a concentration of 1 to 12 mass % and TiO 2 A TiO film characterized in that the difference between the maximum and minimum concentrations is 0.06 mass% or less within an area of ​​30 mm x 30 mm in at least one plane. 2 A silica glass containing [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5716730 Summary of the Invention [Problem to be solved by the invention]

[0006] In general, in the manufacture of low thermal expansion glass materials, the composition inside (e.g., TiO 2 However, it is difficult to manufacture a glass material that does not have locally non-uniform portions in the concentration. A glass material is cut into the shape of a mask blank substrate, and the main surface of the mask blank substrate is polished, and then visually inspected. Substrates having localized compositional non-uniformities are rejected as rejected products through this visual inspection. However, as described above, it is difficult to manufacture a glass material that does not have localized compositional non-uniformities, and this has led to a problem of low yield.

[0007] Therefore, an object of the present invention is to provide a method for manufacturing a mask blank substrate, a substrate with a multilayer reflective film, a reflective mask blank, a reflective mask, and a semiconductor device, which can satisfy the required characteristics of a mask blank substrate despite having internal non-uniformities and contribute to improving the manufacturing yield. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention has the following configuration.

[0009] (Configuration 1) A mask blank substrate having two opposing main surfaces, The substrate is made of SiO 2 and TiO 2 The glass material contains A first region is provided on one main surface of the substrate; the first region is a region inside a rectangle of 132 mm×104 mm including a central portion of the one of the main surfaces, and extends from the one of the main surfaces toward the other of the main surfaces to a depth of 500 μm; a localized non-uniformity in an internal region of the substrate excluding the first region; The difference between the ratio of the Ti content to the Si content (Ti / Si) of the non-uniform portion and the Ti / Si of the internal region excluding the non-uniform portion is 0.25% or more; The variation in Ti content in the first region and the internal region of the substrate excluding the non-uniform portion is 0.06 mass % or less. A mask blank substrate comprising:

[0010] (Configuration 2) a second region on the other main surface side of the substrate; the second region is a region inside a rectangle of 132 mm×104 mm including a central portion of the other main surface, and extends from the other main surface toward the one main surface to a depth of 500 μm, The non-uniform portion is included in the second region. 2. A mask blank substrate according to claim 1.

[0011] (Configuration 3) 3. The mask blank substrate according to configuration 1 or 2, wherein the Ti content of the substrate excluding the non-uniform portion is 3 mass % or more. (Configuration 4) 4. A mask blank substrate according to any one of configurations 1 to 3, wherein Ti / Si in the non-uniform portion is smaller than Ti / Si in the internal region excluding the non-uniform portion.

[0012] (Configuration 5) A multilayer reflective film-coated substrate comprising a substrate having two opposing main surfaces and a multilayer reflective film provided on one of the main surfaces of the substrate, The substrate is made of SiO 2 and TiO 2 The glass material contains a first region on the one main surface side of the substrate; the first region is a region inside a rectangle of 132 mm×104 mm including a central portion of the one of the main surfaces, and extends from the one of the main surfaces toward the other of the main surfaces to a depth of 500 μm; a localized non-uniformity in an internal region of the substrate excluding the first region; The difference between the ratio of the Ti content to the Si content (Ti / Si) of the non-uniform portion and the Ti / Si of the internal region excluding the non-uniform portion is 0.25% or more; The variation in Ti content in the first region and the internal region of the substrate excluding the non-uniform portion is 0.06 mass % or less. A multilayer reflective film-coated substrate comprising:

[0013] (Configuration 6) a second region on the other main surface side of the substrate; the second region is a region inside a rectangle of 132 mm×104 mm including a central portion of the other main surface, and extends from the other main surface toward the one main surface to a depth of 500 μm, The non-uniform portion is included in the second region. 6. The multilayer reflective film-coated substrate according to configuration 5. (Configuration 7) 7. The multilayer reflective film coated substrate according to configuration 5 or 6, wherein the Ti content of the substrate excluding the non-uniform portion is 3 mass % or more.

[0014] (Configuration 8) 8. The multilayer reflective film coated substrate according to any one of configurations 5 to 7, wherein Ti / Si in the non-uniform portion is smaller than Ti / Si in the internal region excluding the non-uniform portion.

[0015] (Configuration 9) A reflective mask blank comprising a substrate having two opposing main surfaces, a multilayer reflective film provided on one of the main surfaces of the substrate, and a thin film for pattern formation provided on the multilayer reflective film, The substrate is made of SiO 2 and TiO 2The glass material contains a first region on the one main surface side of the substrate; the first region is a region inside a rectangle of 132 mm×104 mm including a central portion of the one of the main surfaces, and extends from the one of the main surfaces toward the other of the main surfaces to a depth of 500 μm; a localized non-uniformity in an internal region of the substrate excluding the first region; The difference between the ratio of the Ti content to the Si content (Ti / Si) of the non-uniform portion and the Ti / Si of the internal region excluding the non-uniform portion is 0.25% or more; The variation in Ti content in the first region and the internal region of the substrate excluding the non-uniform portion is 0.06 mass % or less. A reflective mask blank comprising:

[0016] (Configuration 10) a second region on the other main surface side of the substrate; the second region is a region inside a rectangle of 132 mm×104 mm including a central portion of the other main surface, and extends from the other main surface toward the one main surface to a depth of 500 μm, The non-uniform portion is included in the second region. 10. The reflective mask blank according to claim 9,

[0017] (Configuration 11) The TiO of the substrate excluding the non-uniform portion 2 11. The reflective mask blank according to configuration 9 or 10, wherein the concentration is 3% by mass or more. (Configuration 12) 12. The reflective mask blank according to any one of configurations 9 to 11, wherein Ti / Si in the non-uniform portion is smaller than Ti / Si in the internal region excluding the non-uniform portion.

[0018] (Configuration 13) A reflective mask comprising a substrate having two opposing main surfaces, a multilayer reflective film provided on one of the main surfaces of the substrate, and a thin film having a transfer pattern provided on the multilayer reflective film, The substrate is made of SiO 2 and TiO 2 The glass material contains a first region on the one main surface side of the substrate; the first region is a region inside a rectangle of 132 mm×104 mm including a central portion of the one of the main surfaces, and extends from the one of the main surfaces toward the other of the main surfaces to a depth of 500 μm; a localized non-uniformity in an internal region of the substrate excluding the first region; The difference between the ratio of the Ti content to the Si content (Ti / Si) of the non-uniform portion and the Ti / Si of the internal region excluding the non-uniform portion is 0.25% or more; The variation in Ti content in the first region and the internal region of the substrate excluding the non-uniform portion is 0.06 mass % or less. A reflective mask characterized by:

[0019] (Configuration 14) a second region on the other main surface side of the substrate; the second region is a region inside a rectangle of 132 mm×104 mm including a central portion of the other main surface, and extends from the other main surface toward the one main surface to a depth of 500 μm, The non-uniform portion is included in the second region. 14. The reflective mask according to claim 13. (Configuration 15) 15. The reflective mask according to claim 13, wherein the Ti content of the substrate excluding the non-uniform portion is 3 mass % or more.

[0020] (Configuration 16) 16. The reflective mask according to any one of configurations 13 to 15, wherein Ti / Si in the non-uniform portion is smaller than Ti / Si in the internal region excluding the non-uniform portion. (Configuration 17) 16. A method for manufacturing a semiconductor device, comprising exposing and transferring the transfer pattern onto a resist film on a semiconductor substrate using a reflective mask according to any one of configurations 13 to 15. Effect of the Invention

[0021] According to the present invention, it is possible to provide a mask blank substrate, a substrate with a multilayer reflective film, a reflective mask blank, a reflective mask, and a method for manufacturing a semiconductor device, which can satisfy the required properties of a mask blank substrate despite having internal non-uniformities and contribute to improving the manufacturing yield. [Brief description of the drawings]

[0022] [Figure 1] 1 is a schematic cross-sectional view of a main portion of a mask blank substrate according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a schematic cross-sectional view of a main part of a mask blank substrate, a multilayer reflective film substrate, and a reflective mask blank according to an embodiment of the present invention, and is a process diagram showing, in schematic cross-sectional views of a main part, a process for producing a reflective mask from a reflective mask blank. [Diagram 3] FIG. 2 is an explanatory diagram of a model substrate used in the finite element method. [Figure 4] 13 is a graph showing the relationship between the lateral position (X position) of a model non-uniform portion at each predetermined depth in the model substrate and the displacement at the upper end of the model substrate at that X position. [Diagram 5] 13 is a graph showing the relationship between the lateral position (X position) of a model non-uniform portion for each material in the model substrate and the displacement at the top end of the model substrate at that X position. [Figure 6] 1 is a photograph showing an uneven portion in a substrate. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below, but first, the background to the invention will be described. For example, in the case of a synthetic quartz glass substrate used in an ArF transfer mask, if there is a localized compositional non-uniformity inside, the amount of exposure light attenuates when it passes through the compositional non-uniformity during exposure transfer. For this reason, the presence of a localized compositional non-uniformity inside the synthetic quartz glass substrate is not permitted. In contrast, in the case of a low-thermal expansion glass substrate used in an EUV reflective mask, the EUV exposure light is not transmitted through the low-thermal expansion glass substrate, so there is no problem even if there is a localized compositional non-uniformity inside the low-thermal expansion glass substrate.

[0024] However, in the case of EUV reflective masks, the thermal expansion coefficient of the substrate used in the reflective mask is required to be very small. The reason for this is that when EUV light is irradiated onto the reflective mask, the EUV light is irradiated onto and absorbed by the substrate and multilayer reflective film, generating heat, which causes the substrate to expand thermally, and it is necessary to suppress the movement of the position of the transfer pattern (absorber pattern) on the multilayer reflective film. The effect of the presence of localized compositional nonuniformity inside the low thermal expansion glass substrate on the positional deviation of the absorber pattern on the multilayer reflective film was verified by simulation using the finite element method.

[0025] This will be explained with reference to FIG. 3. FIG. 3 is an explanatory diagram of a model substrate used in the finite element method. As shown in the figure, the thickness t of this model substrate 1' (hereinafter simply referred to as "substrate 1'") is set to 6.35 mm, and the length L in the horizontal direction (X direction) is set to 60 mm. The size of this substrate 1' is assumed to be about half of the substrate in the effective range of a 6025 size mask. For this substrate 1', a situation is assumed in which the right end in the X direction and the bottom end in the Y direction are each constrained. In addition, taking into consideration the exposure conditions, the upper end temperature of the substrate 1' is set to 20°C, and the lower end temperature is set to 10°C. The size of a model non-uniform portion 18' (hereinafter simply referred to as "non-uniform portion 18'") present in this substrate 1' is set to width 50 μm × height 50 μm, and the linear expansion coefficient CTE (Cofficient of Thermal Expansion) of this non-uniform portion 18' is set to 6.5 × 10 -7 / ℃ (equivalent to synthetic quartz glass, i.e., SiO 2 (corresponding to the part with high concentration). The linear expansion coefficient CTE of this substrate 1' was set to conform to the catalog of Corning's low thermal expansion glass (ULE (registered trademark) 7973 Low Expansion Glass). Under these conditions, the depth d and the lateral X position of the non-uniform portion 18' were set (in FIG. 3, the depth d=t / 2, and the lateral X position=L / 2), and the X displacement of the upper end of the substrate 1' (corresponding to the displacement of the pattern during exposure) was analyzed by the finite element method. The X displacement of the upper end of this substrate 1' was also analyzed for those in which the value of the depth d and the value of the lateral X position of the non-uniform portion 18' were changed. The analysis results will be described with reference to FIG. 4 and FIG. 5.

[0026] Fig. 4 is a graph showing the relationship between the lateral position (X position) of the model non-uniform portion at each predetermined depth in the model substrate and the displacement at the upper end of the model substrate at that X position. In the substrate 1' in Fig. 4, the non-uniform portion 18' is located at a depth of 0.5 mm, 3.75 mm, or 5.85 mm from the upper end of the substrate 1'. In Fig. 4, the lateral position (X position) of the non-uniform portion 18' is plotted on the horizontal axis, and the displacement (X displacement) at the upper end of the substrate 1' at the X position of the non-uniform portion 18' is plotted on the vertical axis. As shown in the figure, it was found that the value of this X displacement is on the order of pm, which is an extremely small value. 5 is a graph showing the relationship between the lateral position (X position) of the model nonuniform part for each material in the model substrate and the displacement at the upper end of the model substrate at that X position. The substrate 1' in FIG. 5 contains a synthetic quartz glass equivalent (SiO 2 (corresponding to the area with a high concentration (Si content)) and SUS (stainless steel) (TiO 2 It is assumed that the non-uniform portion 18' has a width of 50 μm, a height of 50 μm, and a depth d of 0.5 mm, as in FIG. 4. Also in FIG. 5, the horizontal axis indicates the lateral position (X position) of the non-uniform portion 18', and the vertical axis indicates the displacement (X displacement) at the upper end of the substrate 1' at the X position of the non-uniform portion 18'. As shown in the figure, it was found that the value of this X displacement is also on the order of pm, which is an extremely small value. As can be seen from these analysis results, it was found that the effect of the presence of local compositional non-uniformity within the substrate on the positional deviation of the absorber pattern is minor.

[0027] On the other hand, it was found that when a localized compositionally non-uniform portion exists near the main surface of the substrate (preferably in a region within a depth of 500 μm), relatively small convex defects and concave defects are likely to occur on the main surface. It was also found that the cause of the occurrence of these convex defects and concave defects is the presence of a compositionally non-uniform portion. 2 The concentration (Ti content) is low (i.e., SiO 2When a compositionally non-uniform portion (high concentration (Si content)) is present in the substrate, the polishing rate of the compositionally non-uniform portion tends to be slower than that of the other portions when the main surface of the substrate is polished, and it is presumed that this difference in polishing rate causes convex defects to occur on the main surface of the substrate after polishing. 2 High concentration (Ti content) (i.e., SiO 2 It is presumed that when a compositionally non-uniform portion (having a low Si content) is present, there is a tendency for differences in resistance to a cleaning solution such as hydrofluoric acid used to clean the main surface of the substrate, and the compositionally non-uniform portion dissolves preferentially, causing a concave defect.

[0028] Furthermore, since the presence of these concave defects or convex defects on the main surface of the substrate on which the multilayer reflective film is formed has a large adverse effect on the formation of the multilayer reflective film, it is desirable that these concave defects or convex defects are not present. In contrast, even if these concave defects or convex defects are present on the main surface of the substrate on which the electrostatically chucked conductive film is formed, the effect on the formation of the conductive film is small.

[0029] As a result of these intensive studies, the inventors have come to the conclusion that although the presence of localized compositional non-uniformities cannot be tolerated near the main surface of the substrate on which the multilayer reflective film is formed, the presence of localized compositional non-uniformities can be tolerated in other internal regions of the substrate, and still sufficient characteristics can be obtained as a substrate for a reflective mask blank.

[0030] Although visual inspection of a substrate or a conventional inspection device can determine the presence of a compositionally nonuniform portion in the substrate, it is not possible to determine the depth from the main surface of the substrate at which the compositionally nonuniform portion exists. The present inventors have conducted extensive research into this problem. The present inventors have found that low-thermal expansion glass substrates generally contain TiO 2 The inventors focused on the fact that the TiO2 contained in the substrate emits fluorescence when irradiated with DUV light, and that the fluorescence is emitted over the entire area of ​​the substrate main surface irradiated with DUV light. 2 If there is a portion with a low concentration (Ti content), the amount of fluorescence emitted from that portion will be low or the portion will not emit fluorescence.2 If there is a part with a high concentration (Ti content), the amount of fluorescent light increases only in that part. Also, the DUV light irradiated onto the main surface of the substrate is converted into TiO 2 However, the light is converted into fluorescence by TiO and hardly reaches the inside of the substrate. These points will be explained with reference to FIG. 6. FIG. 6 is a photograph of an uneven portion near the main surface of the substrate. This photograph shows the cross section of the substrate when irradiated with DUV light having a wavelength of 266 nm. As shown in the figure, the presence of a dark uneven portion 18 was confirmed near the main surface of the substrate 1 (near the surface layer). Note that in the figure, TiO 2 The inhomogeneity of the low concentration (Ti content) areas is shown, but TiO 2 Non-uniform portions can also be seen in areas where the concentration (Ti content) is high (in this case, the non-uniform portions appear brighter than their surroundings in the vicinity of the main surface of the substrate). As a result of these intensive studies, it was found that by irradiating the main surface of the substrate with DUV light, TiO 2 It was concluded that it is possible to distinguish the presence of inhomogeneous areas with low or high concentration (Ti content). The present invention has been made as a result of the above-mentioned intensive studies.

[0031] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Note that the following embodiment is one form for embodying the present invention, and does not limit the scope of the present invention. Note that in the drawings, the same or corresponding parts are given the same reference numerals, and the description thereof may be simplified or omitted. <Mask blank substrate 1> The mask blank substrate 1 (or may simply be referred to as the substrate 1) is a rectangular plate-like body, and has two opposing main surfaces 11, 12 and an end surface 19. The two opposing main surfaces 11, 12 are the upper and lower surfaces of this plate-like body, and are formed to face each other. At least one of the two opposing main surfaces 11, 12 is the main surface 11 (sometimes referred to as one main surface) on which a multilayer reflective film or a thin film for pattern formation is to be formed. The main surface 12 opposite to the main surface 11 on which a multilayer reflective film or a thin film for pattern formation is to be formed is sometimes referred to as the back surface (or the other main surface).

[0032] The substrate 1 is preferably made of a material having a low thermal expansion coefficient within the range of 0±5 ppb / °C in order to prevent displacement of the absorber pattern 4a (see FIG. 2) due to heat generation during exposure of the substrate 1 and the multilayer reflective film 2 to EUV light. Examples of materials having a low thermal expansion coefficient within this range include SiO 2 -TiO 2 SiO-based glass containing halogens (fluorine (F) and chlorine (Cl)) 2 -TiO 2 Glasses, TiO 2 Oxides other than those mentioned above (e.g., B 2 O 3 , P 2 O 5 SiO containing 2 -TiO 2 Glass or the like can be used.

[0033] A mask blank substrate 1 having a size of 6025 (152.4 mm×152.4 mm×6.35 mm) is preferably used. The substrate 1 has a first region 15 on one main surface 11. The first region 15 is a region inside a rectangle A of 132 mm × 104 mm (pattern formation region) 13 including the central portion of one main surface 11 (a region excluding the region outside the rectangle A on the main surface 11), and extends from one main surface 11 toward the other main surface 12 to a position of a depth d1 of 500 μm. It is more preferable that the depth d1 is 250 μm.

[0034] The mask blank substrate 1 has a localized non-uniform portion 18 in an internal region 17 excluding the first region 15. The difference between the ratio of the Ti content to the Si content (Ti / Si) of this non-uniform portion 18 and the Ti / Si of the internal region 17 excluding the non-uniform portion 18 is 0.25% or more. This difference is calculated by subtracting the smaller value from the larger value. The variation in Ti content in inner region 17 excluding first region 15 and non-uniform portion 18 is 0.06 mass % or less. If the content variation is 0.06 mass % or less, it can be regarded as being substantially uniform, and the desired thermal expansion characteristics can be ensured.

[0035] As described above, it can be said that the influence on the positional deviation of the absorber pattern caused by the non-uniform portion 18 in the internal region 17 excluding the first region 15 is minor. That is, a mask blank substrate 1 having such a configuration satisfies the required characteristics of a mask blank substrate 1 even though it has the non-uniform portion 18 therein, and can contribute to improving the manufacturing yield. In particular, with a mask blank substrate 1 having such a configuration, it is possible to ensure desired thermal expansion characteristics even when the output of the exposure light source becomes high in the future (for example, 500 W or more). The composition of the non-uniform portion 18 is not particularly limited as long as it satisfies the above requirements. 2 It is acceptable for the area to have a low concentration (Ti content), and TiO 2 It may be a portion where the concentration (Ti content) is high, and may further contain other elements (Al, Cr, Fe, etc.).

[0036] The mask blank substrate 1 also has a second region 16 on the other main surface 12 side. This second region 16 is a region inside a rectangle B of 132 mm × 104 mm (pattern formation region) 14 located in the center of the other main surface 12 (a region on the main surface 12 excluding the region outside the rectangle B), and extends from the other main surface 12 toward the one main surface 11 to a position of a depth d2 of 500 μm. It is more preferable that the depth d2 is 250 μm. This mask blank substrate 1 may have a non-uniform portion 18 in the second region 16.

[0037] As described above, even if concave defects or convex defects are present on the main surface 12 of the substrate 1 on the side on which the electrostatically chucked conductive film 5 (see FIG. 2) is formed, the effect on the formation of the conductive film 5 is small. That is, even the mask blank substrate 1 having such a configuration satisfies the required characteristics of the mask blank substrate 1, and can further contribute to improving the manufacturing yield. In this embodiment, taking into consideration the area in which the minimum pattern is formed, the areas of the above-mentioned rectangles A and B are set to 132 mm x 104 mm, but this is not limited to this and may be, for example, 132 mm x 132 mm.

[0038] From the viewpoint of thermal expansion characteristics, the Ti content of the substrate 1 excluding the non-uniform portions 18 is preferably 3 mass % or more. Moreover, the Ti content of the substrate 1 excluding the non-uniform portions 18 is preferably 10 mass % or less. This is because if the Ti content exceeds 10 mass %, the thermal expansion coefficient may become negative. The Ti content is more preferably 5 to 9 mass %.

[0039] The substrate 1 in this embodiment is not particularly limited, but can be selected by the following method. First, a substrate 1 is prepared by cutting out a glass material to a predetermined size and shaping it, and then at least the main surfaces 11 and 12 of the substrate are polished to a predetermined degree, and the presence or absence of unevenness in the internal region is detected using a substrate defect inspection device or the like with an inspection wavelength of 300 nm to 500 nm. With an inspection wavelength in this range, the presence or absence of unevenness over the entire substrate can be detected. Next, for the substrate on which the non-uniformity was detected, DUV light with an inspection wavelength of 300 nm or less (e.g., 266 nm) is irradiated onto each main surface of the base material, and cross-sectional images are obtained. By using DUV light with an inspection wavelength of 300 nm or less, it is possible to perform inspection to a depth of 500 μm from the main surface. Then, the degree of fluorescence emission is compared from the acquired cross-sectional images to determine whether or not there is a non-uniform portion, and a substrate determined to have no non-uniform portion in the first region can be selected as the mask blank substrate 1. Note that the detection of the presence or absence of the internal non-uniform portion described above may be performed by visual inspection.

[0040] Moreover, the size of the unacceptable non-uniformity 18 in the first region 15 is preferably 50 μm or more, and more preferably 75 μm or more. This size makes it possible to detect it by the inspection using the above-mentioned DUV light. If the size is less than this size, the effect on the thermal expansion characteristics is significantly reduced.

[0041] The Ti / Si ratio of the non-uniform portion 18 may be smaller than the Ti / Si ratio of the internal region excluding the non-uniform portion 18. In this case, the SiO 2 The concentration (Si content) is high, and as shown in FIG. 6, the presence of dark non-uniform parts 18 can be confirmed in the vicinity of the main surface (near the surface layer) of substrate 1.

[0042] The main surface 11 of the substrate 1 on which the multilayer reflective film 2 and the thin film 4 for pattern formation are formed is surface-processed to have a high flatness from the viewpoint of obtaining at least pattern transfer accuracy and positional accuracy. In the case of EUV exposure, the flatness is preferably 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less in a 132 mm×132 mm region located in the center of the main surface 11 on which the multilayer reflective film 2 and the thin film 4 for pattern formation are formed. In addition, the main surface 12 on the opposite side to the side on which the transfer pattern is formed is a surface that is electrostatically chucked when set in an exposure device, and the flatness is preferably 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less in a 132 mm×132 mm region located in the center of the main surface 12. The flatness of the main surface 12 of the reflective mask blank 100 in a 142 mm × 142 mm region located in the center of the main surface 12 is preferably 1 μm or less, more preferably 0.5 μm or less, and particularly preferably 0.3 μm or less.

[0043] In addition, the surface smoothness of the substrate 1 is also an extremely important item. The surface roughness of the main surface 11 of the substrate 1 on which the absorber pattern 4a is formed is preferably 0.1 nm or less in terms of root mean square roughness (RMS). The surface smoothness can be measured by an atomic force microscope.

[0044] Furthermore, the substrate 1 preferably has high rigidity in order to suppress deformation due to film stress of films (such as the multilayer reflective film 2) formed thereon. In particular, the substrate 1 preferably has a high Young's modulus of 65 GPa or more.

[0045] <Substrate with multilayer reflective film> Next, a multilayer reflective film-coated substrate 10 in an embodiment of the present invention will be described. The multilayer reflective film-coated substrate 10 includes a substrate 1 having two opposing main surfaces 11, 12, and a multilayer reflective film 2 provided on one of the main surfaces 11 of the substrate 1 (see FIG. 2(a)). The substrate 1 has a similar configuration to the mask blank substrate 1 described above. In this specification, "having a multilayer reflective film 2 on the main surface of the substrate 1" means that the multilayer reflective film 2 is disposed in contact with the surface of the substrate 1, and also includes the case where another film is disposed between the substrate 1 and the multilayer reflective film 2. The same applies to other films. For example, "having a film B on a film A" means that the films A and B are disposed so as to be in direct contact with each other, and also includes the case where another film is disposed between the films A and B. In addition, in this specification, for example, "having a film A in contact with the surface of film B" means that the films A and B are disposed so as to be in direct contact with each other, without another film being disposed between the films A and B.

[0046] <<Multilayer reflective film 2>> The multilayer reflective film 2 imparts a function of reflecting EUV light to the reflective mask 200, and is a multilayer film in which layers containing elements with different refractive indices as main components are periodically laminated.

[0047] Generally, a multilayer film in which a thin film (high refractive index layer) of a light element or its compound, which is a high refractive index material, and a thin film (low refractive index layer) of a heavy element or its compound, which is a low refractive index material, are alternately stacked for about 40 to 60 periods, is used as the multilayer reflective film 2. The multilayer film may be stacked multiple times, with a high refractive index layer / low refractive index layer stacked in this order from the substrate 1 side as one period. The multilayer film may also be stacked multiple times, with a low refractive index layer / high refractive index layer stacked in this order from the substrate 1 side as one period. Note that the top layer of the multilayer reflective film 2, that is, the surface layer of the multilayer reflective film 2 on the opposite side to the substrate 1, is preferably a high refractive index layer. In the above-mentioned multilayer film, when a high refractive index layer / low refractive index layer stacked in this order from the substrate 1 is stacked multiple times, with a high refractive index layer / low refractive index layer stacked in this order as one period, the top layer is a low refractive index layer. In this case, if the low refractive index layer constitutes the top surface of the multilayer reflective film 2, it is easily oxidized, and the reflectance of the reflective mask 200 decreases. For this reason, it is preferable to further form a high refractive index layer on the uppermost low refractive index layer to form the multilayer reflective film 2. On the other hand, in the above-mentioned multilayer film, when a laminate structure of low refractive index layer / high refractive index layer in which a low refractive index layer and a high refractive index layer are laminated in this order from the substrate 1 side is one period, the uppermost layer is the high refractive index layer and may be left as it is.

[0048] In this embodiment, a layer containing silicon (Si) is used as the high refractive index layer. In addition to simple Si, a Si compound containing boron (B), carbon (C), nitrogen (N), and oxygen (O) in addition to Si can be used as the material containing Si. Furthermore, a simple metal selected from molybdenum (Mo), ruthenium (Ru), rhodium (Rh), and platinum (Pt), or an alloy thereof, is used as the low refractive index layer. For example, as the multilayer reflective film 2 for EUV light with a wavelength of 13 nm to 14 nm, a Mo / Si periodic laminated film in which Mo films and Si films are alternately laminated for about 40 to 60 periods is preferably used. Note that the high refractive index layer, which is the top layer of the multilayer reflective film 2, may be formed of silicon (Si).

[0049] The reflectance of the multilayer reflective film 2 alone is usually 65% ​​or more, with the upper limit usually being 73%. The thickness and period of each constituent layer of the multilayer reflective film 2 may be appropriately selected according to the exposure wavelength, and are selected so as to satisfy the law of Bragg reflection. The multilayer reflective film 2 has a plurality of high refractive index layers and a plurality of low refractive index layers, but the thicknesses of the high refractive index layers and the low refractive index layers do not have to be the same. The thickness of the outermost Si layer of the multilayer reflective film 2 can be adjusted within a range that does not reduce the reflectance. The thickness of the outermost Si layer (high refractive index layer) can be in the range of 3 nm to 10 nm.

[0050] The method of forming the multilayer reflective film 2 is known in the art. For example, the multilayer reflective film 2 can be formed by depositing each layer by ion beam sputtering. In the case of the Mo / Si periodic multilayer film described above, a Si film having a thickness of about 4 nm is first deposited on the substrate 1 by using a Si target by, for example, ion beam sputtering. Then, a Mo film having a thickness of about 3 nm is deposited by using a Mo target. This Si film / Mo film is regarded as one period, and 40 to 60 periods are stacked to form the multilayer reflective film 2 (the outermost layer is a Si layer). For example, when the multilayer reflective film 2 has 60 periods, the number of steps increases compared to 40 periods, but the reflectance to EUV light can be increased.

[0051] <Configuration of the Reflective Mask Blank 100 and Its Manufacturing Method> FIG. 2(a) is a schematic cross-sectional view of a main part for explaining the configuration of the reflective mask blank 100 of this embodiment. As shown in FIG. 2(a), the reflective mask blank 100 has a substrate 1, a multilayer reflective film 2, a protective film 3, and an absorber film (a thin film for patterning) 4, which are laminated in this order. The multilayer reflective film 2 is formed on the main surface 11 side and reflects EUV light, which is the exposure light, with high reflectance. The substrate 1 and the multilayer reflective film 2 have the same configuration as the multilayer reflective film-coated substrate 10 described above. The protective film 3 is provided to protect the multilayer reflective film 2, and is made of a material that is resistant to an etchant and a cleaning solution used when patterning the absorber film 4 described later. The absorber film 4 absorbs EUV light. In addition, a conductive film 5 for electrostatic chuck is formed on the main surface 12 side of the substrate 1. Moreover, the reflective mask blank 100 further has an etching mask film 6 on the absorber film 4, as shown in FIG. 2(a).

[0052] Hereinafter, this embodiment will be described layer by layer. The substrate 1 and the multilayer reflective film 2 have the same configuration as those described above, so their description will be omitted.

[0053] <<Protective film 3>> The reflective mask blank 100 of this embodiment preferably includes a protective film 3 between the multilayer reflective film 2 and the absorber film 4 .

[0054] In order to protect the multilayer reflective film 2 from dry etching and cleaning in the manufacturing process of the reflective mask 200 described later, a protective film 3 can be formed on the multilayer reflective film 2 or in contact with the surface of the multilayer reflective film 2. The protective film 3 also serves to protect the multilayer reflective film 2 when repairing black defects in the absorber pattern 4a using an electron beam (EB). Here, FIG. 2 shows the case where the protective film 3 is a single layer, but the protective film 3 can also have a laminated structure of two or more layers. The protective film 3 is formed of a material that is resistant to an etchant used in patterning the absorber film 4 and a cleaning solution. By forming the protective film 3 on the multilayer reflective film 2, damage to the surface of the multilayer reflective film 2 can be suppressed when manufacturing the reflective mask 200 (EUV mask) using the substrate 1 having the multilayer reflective film 2 and the protective film 3. Therefore, the reflectance characteristic of the multilayer reflective film 2 for EUV light is improved.

[0055] In the reflective mask blank 100 of this embodiment, a material that is resistant to the etching gas used in the dry etching for patterning the absorber film 4 formed on the protective film 3 can be selected as the material of the protective film 3.

[0056] When the layer of the absorber film 4 in contact with the surface of the protective film 3 is a thin film made of a material containing ruthenium (Ru) (Ru-based material), such as the lower layer 41 in this embodiment, the material of the protective film 3 can be selected from silicon-based materials such as silicon (Si), a material containing silicon (Si) and oxygen (O), a material containing silicon (Si) and nitrogen (N), or a material containing silicon (Si), oxygen (O) and nitrogen (N).

[0057] The thickness of the protective film 3 is not particularly limited as long as it can function to protect the multilayer reflective film 2. From the viewpoint of the reflectance of EUV light, the thickness of the protective film 3 is preferably 1.0 nm or more and 8.0 nm or less, more preferably 1.5 nm or more and 6.0 nm or less.

[0058] The method for forming the protective film 3 can be any known film formation method without any particular limitations, and specific examples include sputtering and ion beam sputtering.

[0059] <<Absorber film (thin film for pattern formation) 4>> In the reflective mask blank 100 of this embodiment, an absorber film 4 that reduces the reflectance of EUV light is formed on the multilayer reflective film 2 or on the protective film 3 formed on the multilayer reflective film 2. As shown in FIG. 2 , the absorber film 4 of the reflective mask blank 100 of this embodiment includes a lower layer 41 and an uppermost layer 42.

[0060] In the reflective mask blank 100 of this embodiment, in the portion where the absorber film 4 (absorber pattern 4a) is provided, the EUV light is absorbed and reduced, while a part of the light is reflected at a level that does not adversely affect pattern transfer. On the other hand, in the opening (the portion where the absorber film 4 is not provided), the EUV light is reflected from the multilayer reflective film 2 (from the multilayer reflective film 2 via the protective film 3, if the protective film 3 is provided). The reflected light from the portion where the absorber film 4 is formed has a desired reflectance difference with the reflected light from the opening. In addition, the reflected light from the portion where the absorber film 4 is formed may have a desired phase difference with the reflected light from the opening. When the reflected light from the portion where the absorber film 4 is formed and the reflected light from the opening have a phase difference, the absorber film 4 is formed so that the phase difference is 130 degrees to 230 degrees. The light with an inverted phase difference of about 180 degrees or about 220 degrees interferes with each other at the pattern edge portion, thereby improving the image contrast of the projected optical image. With the improvement in image contrast, the resolution increases and various latitudes relating to exposure, such as exposure dose latitude and focus latitude, are expanded.

[0061] Although it depends on the pattern and exposure conditions, in order to obtain a phase shift effect, the relative reflectance of the absorber pattern 4a to EUV light is preferably 2% to 40%, more preferably 6% to 35%, even more preferably 15% to 35%, and particularly preferably 15% to 25%. Here, the relative reflectance of the absorber film 4 (absorber pattern 4a) is the reflectance of EUV light reflected from the absorber pattern 4a when the reflectance of EUV light reflected from the multilayer reflective film 2 (including the multilayer reflective film 2 with the protective film 3) in a portion without the absorber pattern 4a is 100%. In this specification, the relative reflectance may be simply referred to as "reflectance".

[0062] Although it depends on the pattern and exposure conditions, in order to obtain a phase shift effect, the absolute reflectance of the absorber film 4 (or the absorber pattern 4a) to EUV light is preferably 4% to 27%, and more preferably 10% to 17%.

[0063] The absorber film 4 preferably includes a lower layer 41 and a top layer 42. The top layer 42 is a layer located on the outermost surface of the absorber film 4 opposite to the multilayer reflective film 2. The lower layer 41 is a layer located at any position between the top layer 42 and the multilayer reflective film 2 in the absorber film 4. In terms of simplifying the film formation process, the absorber film 4 preferably includes two layers, the lower layer 41 and the top layer 42. The lower layer 41 is preferably composed of simple ruthenium (Ru) or a material containing ruthenium (Ru).

[0064] From the viewpoint of increasing the verticality of the pattern sidewall shape, the absorber film 4 preferably includes a top layer 42 formed of a material containing ruthenium (Ru). The same etching gas can be used when patterning the absorber film 4 by dry etching. The top layer 42 preferably contains oxygen. By including oxygen in the Ru-based compound, the crystal structure can be made more amorphous. The top layer 42 may contain a metal element other than ruthenium (Ru). Examples of such metal elements include chromium (Cr) and iridium (Ir), and in particular, chromium (Cr) is preferred from the viewpoint of etching rate and crystallinity.

[0065] The phase difference and reflectance of the absorber film 4 can be adjusted by changing the refractive index n, the extinction coefficient k, and the film thickness. The film thickness of the absorber film 4 is preferably 60 nm or less, more preferably 50 nm or less, and even more preferably 45 nm or less. The film thickness of the absorber film 4 is preferably 25 nm or more. In addition, when the protective film 3 is provided, the phase difference and reflectance of the absorber film 4 can also be adjusted in consideration of the refractive index n, the extinction coefficient k, and the film thickness of the protective film 3.

[0066] The thin films (e.g., the lower layer 41 and the uppermost layer 42) constituting the absorber film 4 of the above-mentioned predetermined material can be formed by known methods such as sputtering methods such as DC sputtering and RF sputtering, and reactive sputtering using oxygen gas or the like. An alloy target of Ru and Cr can be used as the target. The thin film constituting the absorber film 4 can be formed by co-sputtering using a Ru target and a Cr target.

[0067] The absorber film 4 can be a multilayer film further including layers other than the lower layer 41 and the top layer 42. For example, the absorber film 4 can further include a layer between the lower layer 41 and the protective film 3 for improving the etching selectivity with the protective film 3. The absorber film 4 can further include a layer between the top layer 42 and the lower layer 41 for improving the optical properties. From the viewpoint of productivity, it is preferable that the number of layers of the absorber film 4 is not too large. Therefore, the absorber film 4 of this embodiment is preferably composed of two layers, the lower layer 41 and the top layer 42. However, the absorber film 4 in the present invention only needs to include at least the lower layer 41, and may be composed of a single layer structure using the material constituting the lower layer 41.

[0068] <<Etching mask film 6>> An etching mask film 6 can be formed on the absorber film 4 or in contact with the surface of the absorber film 4. The material of the etching mask film 6 is one that has a high etching selectivity of the absorber film 4 to the etching mask film 6. Here, the "etching selectivity of B to A" refers to the ratio of the etching rate of A, which is a layer that does not need to be etched (a layer that serves as a mask), to B, which is a layer that needs to be etched. Specifically, it is specified by the formula "etching selectivity of B to A=etching rate of B / etching rate of A". In addition, "high selectivity" refers to a high selectivity value as defined above with respect to a comparison target. The etching selectivity of the absorber film 4 to the etching mask film 6 is preferably 1.5 or more, more preferably 3 or more.

[0069] The absorber film 4 made of a Ru-based material in this embodiment can be etched by dry etching using a chlorine-based gas containing oxygen or oxygen gas. As a material having a high etching selectivity of the absorber film 4 made of a Ru-based material to the etching mask film 6, silicon (Si) or a silicon compound material can be used.

[0070] Examples of silicon compounds that can be used for the etching mask film 6 include materials containing silicon (Si) and at least one element selected from nitrogen (N), oxygen (O), carbon (C) and hydrogen (H), as well as materials such as metal silicon (metal silicide) or metal silicon compound (metal silicide compound) in which silicon or a silicon compound contains a metal. Examples of metal silicon compounds include materials containing a metal, Si, and at least one element selected from N, O, C and H.

[0071] The thickness of the etching mask film 6 is desirably 2 nm or more from the viewpoint of obtaining the function as an etching mask for accurately forming a transfer pattern in the absorber film 4. Moreover, the thickness of the etching mask film 6 is desirably 15 nm or less from the viewpoint of making the thickness of the resist film 8 thin.

[0072] <<Conductive film 5>> A conductive film 5 for an electrostatic chuck is generally formed on the main surface 12 side of the substrate 1 (opposite the surface on which the multilayer reflective film 2 is formed). The electrical characteristics (sheet resistance) required for the conductive film 5 for an electrostatic chuck are usually 100 Ω / □ (Ω / Square) or less. The conductive film 5 can be formed, for example, by magnetron sputtering or ion beam sputtering using targets of metals and alloys such as chromium (Cr) and tantalum (Ta).

[0073] The chromium (Cr)-containing material of the conductive film 5 is preferably a Cr compound that contains Cr and further contains at least one selected from boron (B), nitrogen (N), oxygen (O), and carbon (C).

[0074] The material containing tantalum (Ta) for the conductive film 5 is preferably Ta, an alloy containing Ta, or a Ta compound containing any of these with at least one of boron, nitrogen, oxygen, and carbon.

[0075] The thickness of the conductive film 5 is not particularly limited as long as it satisfies the function for electrostatic chuck. The thickness of the conductive film 5 is usually 10 nm to 200 nm. The conductive film 5 also serves to adjust the stress on the main surface 12 side of the mask blank 100. That is, the conductive film 5 is adjusted to obtain a flat reflective mask blank 100 by balancing with the stress from various films formed on the main surface 11 side.

[0076] <Reflection mask 200 and its manufacturing method> In this embodiment, a reflective mask 200 includes a multilayer reflective film 2 and an absorber film 4 on which a transfer pattern is formed, in this order, on the main surface of a substrate 1. The substrate 1, the multilayer reflective film 2, the protective film 3, and the conductive film 5 in the reflective mask 200 each have the same configuration as those in the above-mentioned reflective mask blank 100. The absorber film 4 of the above-mentioned reflective mask blank 100 of this embodiment can be patterned to form an absorber pattern 4a (transfer pattern). The absorber film 4 can be patterned by a predetermined dry etching gas. The absorber pattern 4a of the reflective mask 200 can absorb EUV light and reflect a part of the EUV light with a predetermined reflectance and phase difference from the opening (a portion where the absorber pattern 4a is not formed). The predetermined dry etching gas can be a mixed gas of a chlorine-based gas and an oxygen gas, or oxygen gas. In order to pattern the absorber film 4, an etching mask film 6 can be provided on the absorber film 4 as necessary. In this case, the absorber film 4 can be dry-etched using the etching mask pattern 6a as a mask to form the absorber pattern 4a.

[0077] A method for manufacturing a reflective mask 200 using the reflective mask blank 100 of this embodiment will be described with reference to FIG.

[0078] Fig. 2 is a schematic cross-sectional view of a main part showing a process for producing a reflective mask 200 from a reflective mask blank 100. As shown in Fig. 2(a), a reflective mask blank 100 is prepared. As shown in Fig. 2(b), a resist film 8 is formed on the etching mask film 6 on the main surface 11 (not necessary if the reflective mask blank 100 is provided with a resist film 8). As shown in Fig. 2(c), a desired pattern is drawn (exposed) on this resist film 8, which is then developed and rinsed to form a predetermined resist pattern 8a.

[0079] Next, as shown in FIG. 2(d), the etching mask film 6 is etched using the resist pattern 8a as a mask to form an etching mask pattern 6a. Next, the resist pattern 8a is removed by ashing or a resist stripper. Using the etching mask pattern 6a as a mask, the absorber film 4 is etched to form an absorber pattern 4a as shown in FIG. 2(e). Next, the etching mask pattern 6a is removed to form the absorber pattern 4a as shown in FIG. 2(f). Finally, wet cleaning is performed using an acidic or alkaline aqueous solution to manufacture a reflective mask 200. If necessary, a mask defect inspection is performed after the wet cleaning, and mask defect correction can be performed as appropriate.

[0080] By the above steps, a reflective mask 200 having highly accurate and fine absorber patterns 4a can be obtained.

[0081] <Method of manufacturing semiconductor devices> The present embodiment is a method for manufacturing a semiconductor device, which includes the use of the above-described reflective mask 200. The reflective mask 200 of the present embodiment is set in an exposure tool having an exposure light source of EUV light, and a transfer pattern is exposed and transferred to a resist film formed on a semiconductor substrate, which is a substrate of a transfer object, to thereby manufacture a semiconductor device.

[0082] Specifically, by performing EUV exposure using the reflective mask 200 of the above-described embodiment, a desired transfer pattern can be formed on a semiconductor substrate based on the absorber pattern 4a of the reflective mask 200. In addition to this lithography process, various processes such as etching of the film to be processed, formation of an insulating film and a conductive film, introduction of a dopant, and annealing can be performed to manufacture a semiconductor device having a desired electronic circuit formed thereon. EXAMPLES

[0083] Examples will be described below with reference to the drawings. The present embodiment is not limited to these examples. Note that the same reference numerals are used for similar components in the examples, and descriptions thereof will be simplified or omitted.

[0084] [Example 1] As Example 1, a SiO 2 low thermal expansion glass substrate having a size of 6025 (approximately 152 mm×152 mm×6.35 mm) and both the first and second main surfaces are polished is used. 2 -TiO 2 A glass substrate of this type was prepared as substrate 1. To obtain a flat and smooth main surface, polishing was carried out through a rough polishing process, a precision polishing process, a local polishing process, and a touch polishing process. This substrate 1 was selected using the following process. First, the presence or absence of non-uniformity 18 over the entire substrate 1 was detected by a substrate defect inspection device using inspection light (laser light) with an inspection wavelength of 300 nm to 500 nm. As a result, the presence of non-uniformity 18 in an internal region 17 of substrate 1 was confirmed. Next, an inspection device manufactured by Olympus Corporation was used to irradiate each of the main surfaces 11 and 12 of the substrate 1 with DUV light having an inspection wavelength of 266 nm, and cross-sectional images were obtained. The degree of fluorescence emission was then compared from the acquired cross-sectional images to determine the presence or absence of non-uniform areas. The cross-sectional images including the first region 15 had no localized dark or white areas and had a uniform brightness overall. In other words, no non-uniform areas with a size of 50 μm or more were detected in the first region 15. On the other hand, in the cross-sectional image including the second region 16, a localized dark area was detected with a size of 50 μm compared to the surroundings. Thus, the substrate 1 in Example 1 had a non-uniform portion 18 in the internal region 17 of the substrate 1 excluding the first region 15. The substrate 1 also had a non-uniform portion 18 in the second region 16. The size of the non-uniform portion 18 in the internal region 17 was 50 μm, and the size of the non-uniform portion 18 in the second region 16 was 200 μm.

[0085] Furthermore, the ratio (Ti / Si) of the Ti content to the Si content of non-uniform portion 18 was 11.25%, and the Ti / Si of internal region 17 excluding non-uniform portion 18 was 10.75%. Therefore, the difference between the Ti / Si of non-uniform portion 18 and the Ti / Si of internal region 17 excluding non-uniform portion 18 was 0.5%, which was 0.25% or more. The Ti / Si was calculated by performing elemental analysis of elements (C, O, Al, Si, Ti) contained in substrate 1 by energy dispersive X-ray analysis (EDX) in a region of about 300 μm depth from main surface 12 of the substrate toward internal region 17 at intervals of about 3 μm, and then calculating Ti / Si in non-uniform portion 18 and Ti / Si in internal region 17 as a moving average value of 10 intervals (points). Ti / Si in non-uniform portion 18 was taken as the maximum value of Ti / Si, and Ti / Si in internal region 17 was taken as the average value of 30 points of the moving average value in internal region 17 excluding non-uniform portion 18. Hereinafter, Ti / Si was calculated in the same manner for Comparative Example 1. In the substrate 1 of Example 1, the variation in Ti content in the internal region 17 excluding the first region 15 and the non-uniform portion 18 was 0.04 mass %, which was 0.06 mass % or less. The Ti content of substrate 1 excluding non-uniform portion 18 was 4 mass %, which was 3 mass % or more. Furthermore, the Ti / Si ratio of non-uniform portion 18 was smaller than the Ti / Si ratio of internal region 17 excluding non-uniform portion 18.

[0086] Using the substrate of Example 1, a reflective mask blank 100 having the structure shown in FIG. 2(a) was manufactured as follows. First, the conductive film 5 made of a CrN film was formed on the main surface 12 of the substrate 1 by magnetron sputtering (reactive sputtering) under the following conditions. The conductive film 5 was formed by sputtering a Cr target with argon (Ar) gas and nitrogen (N 2 ) gas mixture atmosphere to a film thickness of 20 nm.

[0087] Next, a multilayer reflective film 2 was formed on the main surface 11 of the substrate 1 on the side opposite to the side on which the conductive film 5 was formed. The multilayer reflective film 2 formed on the substrate 1 was a periodic multilayer reflective film made of molybdenum (Mo) and silicon (Si) in order to make the multilayer reflective film 2 suitable for EUV light with a wavelength of 13.5 nm. The multilayer reflective film 2 was formed by alternately laminating Mo layers and Si layers on the substrate 1 by ion beam sputtering in a krypton (Kr) gas atmosphere using a Mo target and a Si target. First, a Si film was formed with a thickness of 4.2 nm, and then a Mo film was formed with a thickness of 2.8 nm. This constitutes one period, and 40 periods were laminated in the same manner, and finally a Si film was formed with a thickness of 4.0 nm to form the multilayer reflective film 2.

[0088] Next, in an Ar gas atmosphere, SiO 2 The surface of the multilayer reflective film 2 is coated with SiO by RF sputtering using a target. 2 The protective film 3 made of a film was formed to a thickness of 2.6 nm.

[0089] Next, a thin film (RuCrNO film) made of ruthenium (Ru), chromium (Cr), nitrogen (N) and oxygen (O) was formed as the lower layer 41 of the absorber film 4 in Example 1 by DC magnetron sputtering. The lower layer 41 was formed by sputtering krypton (Kr) gas and nitrogen (N 2 ) gas and oxygen gas (O 2 The film was formed to a thickness of 33.5 nm in a mixed gas atmosphere of Kr:N. 2 :O 2 = 12:8:1. The film was formed by applying a power of 1500 W to the Ru target and a power of 500 W to the Cr target.

[0090] Next, a thin film (RuCrO film) made of ruthenium (Ru), chromium (Cr) and oxygen (O) was formed as the top layer 42 of the absorber film 4 by DC magnetron sputtering (reactive sputtering). The top layer 42 was formed by sputtering krypton (Kr) gas and oxygen (O) using a Ru target and a Cr target. 2 ) gas mixture atmosphere, the film was formed by reactive sputtering to a thickness of 8.5 nm.

[0091] Next, on the absorber film 4, Si 3 N 4 An etching mask film 6 made of a Si film was formed. 3 N 4 The film was formed to a thickness of 20 nm by reactive sputtering in a nitrogen gas atmosphere using a Si target. By the above-mentioned procedure, the reflective mask blank 100 of Example 1 was manufactured.

[0092] Next, the reflective mask blank 100 was used to manufacture a reflective mask 200 of Example 1, as shown in FIG.

[0093] The reflective mask 200 produced in Example 1 was set in an EUV scanner, and EUV exposure was performed on a wafer on which a film to be processed and a resist film were formed on a semiconductor substrate. The exposed resist film was then developed to form a resist pattern on the semiconductor substrate on which the film to be processed was formed. This resist pattern was transferred to the film to be processed by etching, and various processes such as the formation of an insulating film and a conductive film, the introduction of a dopant, and annealing were performed to manufacture a semiconductor device having desired characteristics. Thus, the substrate 1 of Example 1 satisfied the required characteristics as a mask blank substrate, even though it had an internal non-uniform portion. It can be said that the use of the substrate 1 of Example 1 as a mask blank substrate can contribute to improving the manufacturing yield.

[0094] [Comparative Example 1] As Comparative Example 1, a SiO 2 low-thermal expansion glass substrate having a size of 6025 (approximately 152 mm×152 mm×6.35 mm) and both the first and second main surfaces of which were polished, was used as the substrate in the same manner as in Example 1. 2 -TiO 2 A glass substrate of this type was prepared as substrate 1. To obtain a flat and smooth main surface, polishing was carried out through a rough polishing process, a precision polishing process, a local polishing process, and a touch polishing process. When this substrate 1 was also subjected to the same inspection as in Example 1, the presence of non-uniform portions 18 was confirmed not only in the internal region 17 and the second region 16 of the substrate 1, but also in the first region 15. The size of the non-uniform portions 18 confirmed in the first region 15 was 150 μm.

[0095] Furthermore, the Ti / Si of non-uniform portion 18 of internal region 17 was 11.25%, and the Ti / Si of internal region 17 excluding non-uniform portion 18 was 10.75%. Therefore, the difference between the Ti / Si of non-uniform portion 18 and the Ti / Si of internal region 17 excluding non-uniform portion 18 was 0.5%, which was greater than or equal to 0.25%. In substrate 1 of Comparative Example 1, the variation in Ti content in first region 15 excluding non-uniform portion 18 and in internal region 17 excluding non-uniform portion 18 was 0.04 mass %, which was 0.06 mass % or less. The Ti content of substrate 1 excluding non-uniform portion 18 was 4 mass %, which was 3 mass % or more. Furthermore, the Ti / Si ratio of non-uniform portion 18 was smaller than the Ti / Si ratio of internal region 17 excluding non-uniform portion 18.

[0096] Using this substrate of Comparative Example 1, a reflective mask blank 100 having the structure shown in FIG. 2(a) was produced in the same manner as in Example 1 as follows. Next, the reflective mask blank 100 was used to manufacture a reflective mask 200 of Comparative Example 1, as shown in FIG. The reflective mask 200 produced in Comparative Example 1 was set in an EUV scanner, and EUV exposure was performed on a wafer on which a film to be processed and a resist film were formed on a semiconductor substrate. The exposed resist film was then developed to form a resist pattern on the semiconductor substrate on which the film to be processed was formed. When the resist pattern was checked, an unacceptable positional deviation occurred with respect to the desired position. This positional deviation is believed to be due to thermal expansion of the substrate 1 in the reflective mask 200 of Comparative Example 1. Unlike the case of Example 1, when the reflective mask 200 produced in Comparative Example 1 was used, a semiconductor device having the desired characteristics could not be manufactured. [Explanation of symbols]

[0097] 1 Substrate (Mask blank substrate) 1' Model board 2 Multilayer reflective film 3 Protective film 4. Absorber film (thin film for pattern formation) 4a Absorber pattern (thin film with transfer pattern) 5 Conductive Film 6 Etching mask film 6a Etching mask pattern 8. Resist film 8a Resist pattern 10. Substrate with multilayer reflective film 11 Main surface (one of the main surfaces) 12 Main surface (other main surface) 13 Pattern Formation Area 14 Pattern Formation Area 15 First area 16 Second area 17 Internal area 18 Uneven Part 18' Model Board 19 End face 41 Lower layer 41a Lower Pattern 42 Top Floor 42a Top layer pattern 100 Reflective mask blank 200 Reflective mask A Rectangle showing the dimensions of the first area B Rectangle showing the dimensions of the second area

Claims

1. A mask blank substrate having two opposing main surfaces, The substrate is made of SiO ２ and TiO ２ The glass material contains A first region is provided on one main surface of the substrate; the first region is a region inside a rectangle of 132 mm × 104 mm including a central portion of the one main surface, and extends from the one main surface toward the other main surface to a depth of 500 μm, a localized non-uniformity in an internal region of the substrate excluding the first region; a ratio (Ti / Si) of a Ti content to a Si content of the non-uniform portion is 0.25% or more relative to the Ti / Si content of the internal region excluding the non-uniform portion; The variation in Ti content in the first region and the internal region of the substrate excluding the non-uniform portion is 0.06 mass % or less. A mask blank substrate comprising:

2. a second region on the other main surface side of the substrate; the second region is a region inside a rectangle of 132 mm × 104 mm including a central portion of the other main surface, and extends from the other main surface toward the one main surface to a depth of 500 μm, The non-uniform portion is included in the second region.

2. The mask blank substrate according to claim 1.

3. 3. The mask blank substrate according to claim 1, wherein the Ti content of the substrate excluding the non-uniform portion is 3 mass % or more.

4. 4. The mask blank substrate according to claim 1, wherein the Ti / Si ratio in the non-uniform portion is smaller than the Ti / Si ratio in the internal region excluding the non-uniform portion.

5. A multilayer reflective film-coated substrate comprising a substrate having two opposing main surfaces and a multilayer reflective film provided on one of the main surfaces of the substrate, The substrate is made of SiO ２ and TiO ２ The glass material contains a first region on the one main surface side of the substrate; the first region is a region inside a rectangle of 132 mm × 104 mm including a central portion of the one main surface, and extends from the one main surface toward the other main surface to a depth of 500 μm, a localized non-uniformity in an internal region of the substrate excluding the first region; a ratio (Ti / Si) of a Ti content to a Si content of the non-uniform portion is 0.25% or more relative to the Ti / Si content of the internal region excluding the non-uniform portion; The variation in Ti content in the first region and the internal region of the substrate excluding the non-uniform portion is 0.06 mass % or less. A multilayer reflective film-coated substrate comprising:

6. a second region on the other main surface side of the substrate; the second region is a region inside a rectangle of 132 mm × 104 mm including a central portion of the other main surface, and extends from the other main surface toward the one main surface to a depth of 500 μm, The non-uniform portion is included in the second region.

6. The multilayer reflective film-coated substrate according to claim 5.

7. 7. The multilayer reflective film coated substrate according to claim 5, wherein the Ti content of the substrate excluding the non-uniform portion is 3 mass % or more.

8. 8. The multilayer reflective film coated substrate according to claim 5, wherein Ti / Si in the non-uniform portion is smaller than Ti / Si in the internal region excluding the non-uniform portion.

9. A reflective mask blank comprising: a substrate having two opposing main surfaces; a multilayer reflective film provided on one of the main surfaces of the substrate; and a thin film for pattern formation provided on the multilayer reflective film, The substrate is made of SiO ２ and TiO ２ The glass material contains a first region on the one main surface side of the substrate; the first region is a region inside a rectangle of 132 mm × 104 mm including a central portion of the one main surface, and extends from the one main surface toward the other main surface to a depth of 500 μm, a localized non-uniformity in an internal region of the substrate excluding the first region; a ratio (Ti / Si) of a Ti content to a Si content of the non-uniform portion is 0.25% or more relative to the Ti / Si content of the internal region excluding the non-uniform portion; The variation in Ti content in the first region and the internal region of the substrate excluding the non-uniform portion is 0.06 mass % or less. A reflective mask blank comprising:

10. a second region on the other main surface side of the substrate; the second region is a region inside a rectangle of 132 mm × 104 mm including a central portion of the other main surface, and extends from the other main surface toward the one main surface to a depth of 500 μm, The non-uniform portion is included in the second region. The reflective mask blank according to claim 9 .

11. 11. The reflective mask blank according to claim 9, wherein the Ti content of the substrate excluding the non-uniform portion is 3 mass % or more.

12. 12. The reflective mask blank according to claim 9, wherein Ti / Si in the non-uniform portion is smaller than Ti / Si in the internal region excluding the non-uniform portion.

13. A reflective mask comprising: a substrate having two opposing main surfaces; a multilayer reflective film provided on one of the main surfaces of the substrate; and a thin film having a transfer pattern provided on the multilayer reflective film, The substrate is made of SiO ２ and TiO ２ The glass material contains a first region on the one main surface side of the substrate; the first region is a region inside a rectangle of 132 mm × 104 mm including a central portion of the one main surface, and extends from the one main surface toward the other main surface to a depth of 500 μm, a localized non-uniformity in an internal region of the substrate excluding the first region; The difference between the ratio of the Ti content of the non-uniform portion to the Si content of the non-uniform portion (Ti / Si) and the Ti / Si content of the internal region excluding the non-uniform portion is 0.25% or more; The variation in Ti content in the first region and the internal region of the substrate excluding the non-uniform portion is 0.06 mass % or less. A reflective mask characterized by:

14. a second region on the other main surface side of the substrate; the second region is a region inside a rectangle of 132 mm × 104 mm including a central portion of the other main surface, and extends from the other main surface toward the one main surface to a depth of 500 μm, The non-uniform portion is included in the second region.

14. The reflective mask according to claim 13.

15. 15. The reflective mask according to claim 13, wherein the Ti content of the substrate excluding the non-uniform portion is 3 mass % or more.

16. 16. The reflective mask according to claim 13, wherein the Ti / Si ratio in the non-uniform portion is smaller than the Ti / Si ratio in the internal region excluding the non-uniform portion.

17. 16. A method for manufacturing a semiconductor device, comprising the steps of: exposing and transferring said transfer pattern onto a resist film on a semiconductor substrate using a reflective mask according to claim 13.

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