Mask blank, method of manufacturing a transfer mask, and method of manufacturing a semiconductor device

Abstract

A mask substrate with fewer minute defects on the surface of a patterning thin film is provided. The mask substrate has a patterning thin film on a substrate. The patterning thin film is a single-layer film containing chromium and nitrogen, or a multilayer film containing a chromium nitride system layer containing chromium and nitrogen. A quadrangular inner region (i.e., a central region) with a side length of 1 μm and a reference center of the substrate is defined on the surface of the patterning thin film. When the arithmetic mean roughness Sa and the maximum height Sz are measured in this central region, Sa is 1.0 nm or less, and Sz / Sa is 14 or less.

Description

Technical Field

[0001] This disclosure relates to a mask substrate, a method for manufacturing a transfer mask using the mask substrate, and a method for manufacturing a semiconductor device using the transfer mask manufactured by the method. Prior Technology Generally, photolithography is used in the manufacturing process of semiconductor devices to form fine patterns. Furthermore, the formation of these fine patterns typically involves multiple substrates called transfer masks (photomasks). These transfer masks are generally made of transparent glass substrates with fine patterns formed by thin metal films, and photolithography is also used in their manufacturing. Since the transfer mask serves as the original for mass transfer of the same fine pattern, the dimensional accuracy of the pattern formed on the transfer mask directly affects the dimensional accuracy of the fine pattern produced using that mask. In recent years, the miniaturization of semiconductor device patterns has significantly improved. Correspondingly, in addition to the miniaturization of the mask pattern formed by the transfer mask, higher precision is also required for the pattern. Furthermore, besides the miniaturization of the transfer mask pattern, the wavelength of the exposure light source used in photolithography has evolved towards shorter wavelengths. Specifically, the exposure light source used in semiconductor device manufacturing has, in recent years, shifted from KrF excimer lasers (wavelength 248nm) to ArF excimer lasers (wavelength 193nm) with increasingly shorter wavelengths. Furthermore, besides binary masks (see, for example, Patent Document 1) which have a light-shielding film pattern made of chromium-based material on a light-transmitting substrate, a type of halftone phase-shifting mask (see, for example, Patent Document 2) is known for use in transfer printing. This halftone phase-shifting mask has a semi-transparent film pattern on a light-transmitting substrate. This semi-transparent film (halftone phase-shifting film) allows light to pass through at an intensity that does not substantially contribute to exposure, and causes a specific phase difference between the light passing through the semi-transparent film and the light that travels the same distance in air, thereby producing a so-called phase-shifting effect. [Previous Technical Documents] [Patent Literature] Patent Document 1: Japanese Patent Application Publication No. 2001-305713 Patent Document 2: International Publication No. 2004 / 090635 As mentioned above, significant progress has been made in the miniaturization of mask patterns in recent years, leading to a demand for forming fine patterns, such as those with dimensions of 50 nm or less, with high pattern precision. To obtain a transfer mask with such fine patterns formed with high pattern precision, the mask substrate used in manufacturing the transfer mask is also required to be a high-quality mask substrate with, for example, fewer surface defects. Although the mask substrate has a pattern-forming film on, for example, a substrate, defects on the surface of this pattern-forming film, even minute defects (convex defects) with very small height and size, are considered to have a potential adverse effect when forming such fine patterns with high pattern precision. Furthermore, in recent years, the most advanced defect inspection device using inspection light with a wavelength of 193nm has been used for defect inspection of mask substrates. If the defect inspection is performed using the aforementioned defect inspection device, even if the defects on the surface of the pattern forming film of the mask substrate are small, the number of defects is very large, and there may still be a problem of inspection termination (overflow) during the inspection. This disclosure is an invention made in view of the aforementioned prior issues, and its first objective is to provide a mask substrate having a structure of a pattern forming film on a substrate, and a mask substrate having fewer minute defects on the surface of the pattern forming film. The second objective of this disclosure is to provide a masking substrate that will not cause adverse effects when performing defect inspection on the masking substrate using the aforementioned state-of-the-art defect inspection device. The third objective of this disclosure is to provide a method for manufacturing a transfer mask that forms a high-precision micro-transfer pattern by using the mask substrate. The fourth objective of this disclosure is to provide a method for manufacturing a semiconductor device that can use the transfer mask to perform high-precision pattern transfer on a resistive film on a semiconductor substrate. Summary of the Invention After persistent and painstaking research to solve the above-mentioned problems, the inventor of this case completed this disclosure. In other words, in order to solve the above-mentioned problems, this disclosure has the following structure. (Component 1) A masking substrate has a pattern forming film on a substrate; the pattern forming film is a single-layer film containing chromium and nitrogen, or a multilayer film containing a chromium nitride system layer containing chromium and nitrogen; for the surface of the pattern forming film, a quadrangular inner region (i.e., a central region) with the center of the substrate as a reference and one side being 1 μm is set, and when the arithmetic mean roughness Sa and the maximum height Sz are measured in the central region, Sa is 1.0 nm or less, and Sz / Sa is 14 or less. (Component 2) For example, the mask substrate constituting 1 is configured with eight quadrilateral inner regions of 1 μm each, which are adjacent regions that do not overlap, in a manner that is adjacent to and surrounds the entire outer perimeter of the central region. When the arithmetic mean roughness Sa and the maximum height Sz of all the adjacent regions are measured, all Sa are less than 1.0 nm and all Sz / Sa are less than 14. (Component 3) If a masking substrate is formed as 1 or 2, the maximum height Sz of the central region is less than 10 nm. (Component 4) If any of the masking substrates in 1 to 3 are formed, the root mean square roughness Sq of the central region is less than 1.0 nm. (Component 5) If any of the masking substrates in 1 to 4 is used to perform defect inspection on the surface of the pattern forming film using a defect inspection device with an inspection light of 193 nm wavelength, and the distribution of convex defects in the inner quadrilateral region (i.e., the pattern forming region) with a side length of 132 mm is obtained, there are convex defects (i.e., micro-defects) with a height of less than 10 nm in the pattern forming region, and the number of such micro-defects in the pattern forming region is less than 100. (Composition 6) If any of the masking substrates in 1 to 5 are formed, the nitrogen content of the portion of the single-layer film excluding the surface layer opposite to the substrate is 8 atomic% or more, or the nitrogen content of the chromium nitride layer of the multilayer film is 8 atomic% or more. (Component 7) If any of the masking substrates 1 to 6 are formed, the chromium content of the single-layer film, excluding the surface layer opposite to the substrate, is 60 atomic% or more, or the chromium content of the chromium nitride layer of the multilayer film is 60 atomic% or more. (Composition 8) Such as forming any of the masking substrates in 1 to 7, wherein the multilayer film has a hard masking layer containing silicon and oxygen on the chromium nitride base layer. (Composition 9) Such as forming any of the masking substrates 1 to 7, wherein the multilayer film has an upper layer containing chromium, oxygen and nitrogen on the chromium nitride base layer. (Composition 10) For example, the masking substrate that constitutes 9, wherein the multilayer film has a hard masking layer containing silicon and oxygen on the upper layer. (Composition 11) If any of the masking substrates 1 to 10 are formed, a phase-shifting film is provided between the substrate and the pattern-forming film. (Composition 12) The masking substrate comprising 11 has the function of allowing the exposure light of an ArF excimer laser (wavelength 193nm) to pass through with a transmittance of 8% or more, and the function of causing a phase difference of 150 degrees or more and 210 degrees between the exposure light passing through the phase shift film and the exposure light passing through the same distance in the air as the thickness of the phase shift film. (Composition 13) If the masking substrate constitutes 11 or 12, wherein the optical concentration of the phase-shifting film and the pattern-forming film in the laminated structure is 3.3 or higher relative to the exposure light of the ArF excimer laser (wavelength 193 nm). (Composition 14) A method for manufacturing a transfer mask, comprising a method for manufacturing a transfer mask using a mask substrate as described in any of 1 to 10, includes a step of forming a transfer pattern on a thin film for pattern formation by dry etching using a resist film having a transfer pattern as a mask. (Composition 15) A method for manufacturing a transfer mask, comprising: a step of forming a transfer pattern on a pattern-forming thin film by dry etching using a resist film having a transfer pattern as a mask; and a step of forming a transfer pattern on a phase-shifting film by dry etching using a pattern-forming thin film having the transfer pattern as a mask. (Composition 16) A method for manufacturing a semiconductor device includes a step of exposing and transferring a transfer pattern onto a resist film on a semiconductor substrate using a transfer mask obtained by a manufacturing method of a transfer mask, such as 14 or 15. According to the masking substrate disclosed herein, by making the masking substrate a structure having a patterning thin film on a substrate, wherein the patterning thin film is a single-layer film containing chromium and nitrogen, or a multilayer film containing a chromium nitride system layer containing chromium and nitrogen, and setting a quadrilateral inner region (i.e., a central region) with the center of the substrate as a reference and one side being 1 μm for the surface of the patterning thin film, when measuring the arithmetic mean roughness Sa and the maximum height Sz in the central region, if Sa is 1.0 nm or less and Sz / Sa is 14 or less, a masking substrate with fewer minute defects on the surface of the patterning thin film can be provided. Furthermore, according to the masking substrate disclosed herein, when performing defect inspection on the masking substrate using the aforementioned state-of-the-art defect inspection apparatus, problems such as inspection overflow will not occur during inspection. Furthermore, by using this mask substrate, a transfer mask with high-precision micro-transfer patterns can be manufactured. Moreover, by using this transfer mask to transfer patterns onto resist films on semiconductor substrates, high-quality semiconductor devices with excellent pattern precision can be manufactured. Simple Explanation of the Diagram Figure 1 is a schematic cross-sectional view showing a first embodiment of the masking substrate related to this disclosure. Figure 2 is a schematic cross-sectional view showing a specific example of the configuration of the first embodiment of the masking substrate related to this disclosure. Figure 3 is a schematic cross-sectional view showing other specific examples of the configuration of the first embodiment of the masking substrate related to this disclosure. Figure 4 is a schematic cross-sectional view showing a second embodiment of the masking substrate related to this disclosure. Figure 5 is a schematic cross-sectional view showing the manufacturing process of a transfer mask using the mask substrate of the first embodiment of this disclosure. Figure 6 is a schematic cross-sectional view showing the manufacturing process of a transfer mask using the mask substrate of the second embodiment of this disclosure. Figure 7 is a top view showing the central region and adjacent regions of the masking base related to this disclosure. Implementation The following describes in detail the forms used to implement this disclosure with reference to the diagrams. First, the process by which this disclosure was completed will be explained. In order to form a light-shielding film with higher optical density (OD) on a masking substrate having a light-shielding film composed of chromium-based materials, when sputtering to form a film containing chromium, oxygen, and carbon (CrOC film) with a film thickness of, for example, 30 nm or more, many micro-defects may occur. Furthermore, the micro-defects referred to in this disclosure are convex defects with a height of 10 nm or less and a size of 70 nm or less. It is believed that the presence of such minute defects on the surface of the light-shielding film may have an adverse effect when forming the fine patterns required in recent years with high pattern precision. Furthermore, if the mask substrate is inspected using the most advanced defect inspection equipment with an inspection light wavelength of 193nm, even if the defects on the surface of the pattern forming film (light-shielding film) of the mask substrate are minute, the sheer number of defects may still cause inspection to be interrupted (overflow) during the inspection process. Therefore, after reviewing the constituent elements of the chromium-based material film, the inventors of this case found that by making the chromium-based light-shielding film contain chromium and nitrogen, the number of the aforementioned micro-defects could be reduced. However, it has been found that micro-defects in chromium-based light-shielding films are difficult to suppress simply by limiting the constituent elements of the film. It is necessary to suppress the growth of crystals generated by the light-shielding film by adjusting the film formation conditions when the light-shielding film is gradually formed on the substrate by sputtering. However, these film formation conditions largely depend on the film formation equipment used. Therefore, new indicators are needed to specify the inherent film formation conditions of the sputtering equipment that can suppress the occurrence of micro-defects. After reviewing the data, the inventors found that measuring the surface of the pattern-forming film (e.g., a light-shielding film) on the mask substrate using atomic force microscopy (AFM) revealed significant differences between the measured areas with and without minute defects in the arithmetic mean roughness Sa and the ratio of maximum height Sz to arithmetic mean roughness Sa (maximum height Sz / arithmetic mean roughness Sa). Therefore, it was determined that the values ​​of Sa and Sz / Sa calculated from AFM measurements of the pattern-forming film within a 1μm quadrilateral area on each side are preferable as parameters for determining the presence or absence of minute defects on the pattern-forming film of the mask substrate. The inventors of this case, after comprehensively considering the circumstances, arrived at the following conclusions and thus completed this disclosure: In order to solve the above-mentioned problems, it is preferable to have a masking substrate with a pattern forming film on the substrate; the pattern forming film is a single-layer film containing chromium and nitrogen, or a multilayer film containing a chromium nitride system layer containing chromium and nitrogen; for the surface of the pattern forming film, a quadrangular inner region (i.e., a central region) with the center of the substrate as a reference and one side being 1 μm is set, and when the arithmetic mean roughness Sa and the maximum height Sz are measured in the central region, Sa is 1.0 nm or less, and Sz / Sa is 14 or less. The following describes this disclosure in detail according to the implementation type. [Mask Base] First, the masking substrate disclosed herein will be explained. [Implementation Type 1] Figure 1 is a schematic cross-sectional view showing a first embodiment of the masking substrate related to this disclosure. As shown in Figure 1, the mask substrate 10 of the first embodiment of this disclosure is a mask substrate having a pattern forming thin film 2 on a substrate 1. Here, the aforementioned substrate 1 is preferably a light-transmitting substrate. Examples of such light-transmitting substrates include glass substrates. Because glass substrates have excellent flatness and smoothness, when using a transfer mask to transfer patterns onto the substrate, high-precision pattern transfer can be performed without deformation of the transferred pattern. Besides synthetic quartz glass, the light-transmitting substrate can be formed from glass materials such as quartz glass, aluminosilicate glass, soda lime glass, and low thermal expansion glass (SiO2-TiO2 glass, etc.). Among these, synthetic quartz glass has a very high transmittance relative to, for example, ArF excimer laser light (wavelength 193nm), which is used for exposure light, making it particularly suitable as the material for the substrate 1 forming the mask substrate 10. The aforementioned pattern-forming thin film 2 is a single-layer film containing chromium and nitrogen, or a multilayer film containing a chromium nitride system layer containing chromium and nitrogen. The thickness of the single-layer film containing chromium and nitrogen can be 30 nm or more, preferably 35 nm or more, and even more preferably 40 nm or more. Furthermore, the thickness of the chromium nitride system layer containing chromium and nitrogen can be 30 nm or more, preferably 35 nm or more, and even more preferably 40 nm or more. When the thin film 2 used to form the above pattern is a single-layer film containing chromium and nitrogen (hereinafter also referred to as "chromium nitride single-layer film"), it is, for example, a light-shielding film, and CrN is a preferred material. The nitrogen content of the chromium nitride monolayer film, excluding the surface layer opposite to the substrate 1, is preferably 8 atomic% or more, more preferably 10 atomic% or more, and even more preferably 12 atomic% or more. By containing 8 atomic% or more of nitrogen, the occurrence of minute defects on the surface of the pattern-forming thin film 2 can be suppressed. Here, the reason for omitting the surface layer of the chromium nitride monolayer film opposite to substrate 1 is that during the cleaning and other treatments performed on the sputtered chromium nitride monolayer film, chromium oxide formation on the surface layer is unavoidable. Furthermore, the surface layer refers to the region extending 5 nm from the surface of the chromium nitride monolayer film opposite to substrate 1 in the depth direction. Furthermore, if the nitrogen content in the chromium nitride-based material is too high, the optical concentration of the chromium nitride monolayer film relative to the exposed light will decrease. Therefore, the nitrogen content of the aforementioned chromium nitride monolayer film is preferably 30 atomic% or less, and more preferably 20 atomic% or less. Furthermore, the chromium content of the aforementioned chromium nitride monolayer film, excluding the surface layer opposite to substrate 1, is preferably 60 atomic% or more, more preferably 70 atomic% or more, and even more preferably 80 atomic% or more. Since the aforementioned chromium nitride monolayer film is, for example, a light-shielding film, a specific optical concentration must be ensured relative to the exposure light. From the above perspective, the aforementioned chromium content is preferably 60 atomic% or more. Furthermore, the aforementioned chromium nitride monolayer film can also be a material containing elements such as oxygen and carbon in addition to chromium and nitrogen (e.g., CrOCN). Moreover, from the viewpoint of suppressing the occurrence of minute defects on the surface of the aforementioned pattern-forming film, the content of each of the aforementioned elements such as oxygen, carbon, boron, and hydrogen is preferably less than 5 atomic%, more preferably less than 3 atomic%. Furthermore, the total content of the aforementioned elements such as oxygen, carbon, boron, and hydrogen is preferably less than 10 atomic%, more preferably less than 5 atomic%. Furthermore, the thickness of the aforementioned chromium nitride monolayer film can be 30 nm or more. This disclosure solves the previous problem that, in order to form a light-shielding film with a higher optical concentration (e.g., an optical concentration of 3.3 or more relative to the exposure light of an ArF excimer laser (wavelength 193 nm), for example, when sputtering to form a CrOC film with a thickness of 30 nm or more, many micro-defects would occur. Furthermore, when the thin film 2 used for forming the above pattern is a multilayer film containing a chromium nitride-based layer containing chromium and nitrogen, the multilayer film is, for example, a light-shielding film. A preferred example of the material for the chromium nitride-based layer is CrN. The nitrogen content of the chromium nitride layer in the multilayer film is the same as that in the case of the chromium nitride single-layer film, preferably 8 atomic% or more, more preferably 10 atomic% or more, and even more preferably 12 atomic% or more. By containing 8 atomic% or more of nitrogen, the occurrence of minute defects on the surface of the thin film 2 for pattern formation can be suppressed. Furthermore, if the nitrogen content in the chromium nitride material is too high, the optical concentration of the chromium nitride layer relative to the exposed light will decrease. Therefore, the nitrogen content of the aforementioned chromium nitride layer is preferably 30 atomic% or less, and more preferably 20 atomic% or less. Furthermore, the chromium content of the chromium nitride layer in the aforementioned multilayer film is, similarly to that in the case of the aforementioned chromium nitride single-layer film, preferably 60 atomic% or more, more preferably 70 atomic% or more, and even more preferably 80 atomic% or more. Since the aforementioned chromium nitride layer is, for example, a major component of a light-shielding film, a specific optical concentration must be ensured relative to the exposure light. From the above perspective, the aforementioned chromium content is preferably 60 atomic% or more. Furthermore, similarly to the case of the chromium nitride-based single-layer film, the chromium nitride-based multilayer film described above can also contain elements such as oxygen and carbon (e.g., CrOCN) in addition to chromium and nitrogen. Moreover, from the viewpoint of suppressing the occurrence of minute defects on the surface of the thin film used for pattern formation, the content of the aforementioned oxygen, carbon, boron, hydrogen, and other elements is preferably less than 5 atomic%, more preferably less than 3 atomic%. Furthermore, the total content of the aforementioned oxygen, carbon, boron, hydrogen, and other elements is preferably less than 10 atomic%, more preferably less than 5 atomic%. Furthermore, the thickness of the chromium nitride layer in the aforementioned multilayer film, which is, for example, the main part of the light-shielding film, can be 30 nm or more, just like in the case of the aforementioned chromium nitride monolayer film. This disclosure solves the previous problem that, in order to form a light-shielding film with a higher optical concentration (e.g., an optical concentration of 3.3 or more relative to the exposure light of an ArF excimer laser (wavelength 193 nm), many minute defects would occur, for example, when sputtering to form a CrOC film with a thickness of 30 nm or more. Furthermore, the masking substrate 10 of this first embodiment may be configured to have a hard masking layer containing silicon and oxygen on the chromium nitride layer of the multilayer film that serves as the pattern forming film 2. Figure 2 is a schematic cross-sectional view showing a specific configuration example of the first embodiment of the masking substrate disclosed herein. As shown in Figure 2, the masking substrate has a structure in which a chromium nitride base layer 5 and a hard masking layer 7 are sequentially deposited on a substrate 1 to serve as a thin film for pattern formation. The structure of the chromium nitride layer 5 described above is as follows, so the explanation is omitted here. Furthermore, the aforementioned hard mask layer 7 functions as an etching mask during the formation of a transfer pattern on the aforementioned chromium nitride layer 5. Therefore, the aforementioned hard mask layer 7 must be a material with high etching selectivity with the directly below chromium nitride layer 5. In this first embodiment, by selecting a silicon-based material as the material of the hard mask layer 7, high etching selectivity with the chromium nitride layer 5 can be ensured. In this first embodiment, the hard masking layer 7 is composed of a material containing silicon and oxygen, preferably a material composed of silicon and oxygen (SiO-based material), or a material that also contains elements such as nitrogen (SiNO-based material). Alternatively, the hard masking layer 7 can also be formed of a tantalum-containing material. In this case, the tantalum-containing material, besides tantalum metal, includes materials containing one or more elements selected from nitrogen, oxygen, boron, and carbon. Examples include Ta, TaN, TaO, TaON, TaBN, TaBO, TaBON, TaCN, TaCO, TaCON, TaBCN, and TaBOCN. While the thickness of the aforementioned hard mask layer 7 is not particularly limited, since it functions as an etching mask when patterning the underlying chromium nitride layer 5 (light-shielding film) using dry etching with chlorine-based gases, its thickness must be at least sufficient to prevent it from disappearing before the etching of the underlying chromium nitride layer 5 is complete. On the other hand, if the hard mask layer 7 is too thick, it will be difficult to thin the resist pattern directly above. From this perspective, the thickness of the hard mask layer 7 is preferably in the range of, for example, 2 nm to 15 nm, and more preferably 3 nm to 10 nm. Furthermore, the masking substrate 10 of this first embodiment may be configured to have an upper layer containing chromium, oxygen and nitrogen on the chromium nitride layer of the multilayer film that serves as the pattern forming film 2. Figure 3 is a schematic cross-sectional view showing other specific configuration examples of the mask substrate related to the first embodiment disclosed herein. As shown in Figure 3, the mask substrate has a structure in which a chromium nitride-based layer 5, a chromium-based material upper layer 6, and a hard mask layer 7 are sequentially deposited on a substrate 1 to serve as a thin film for pattern formation. In this configuration example, the laminated structure of the chromium nitride-based layer 5 and the chromium-based material upper layer 6 serves as a light-shielding film. The structure of the chromium nitride layer 5 described above is as follows, so the explanation is omitted here. In this first embodiment, the upper layer 6 is composed of a material containing chromium, oxygen, and nitrogen. For example, it is preferably a material composed of chromium, oxygen, and nitrogen (CrON-based material), or a material that also contains elements such as carbon (CrOCN-based material). In addition to chromium, oxygen, and nitrogen, the upper layer 6 may also contain elements such as carbon, boron, and hydrogen. The chromium content of the upper layer 6 is preferably less than 60 atomic%, more preferably less than 55 atomic%. The chromium content of the upper layer 6 is preferably 30 atomic% or more, more preferably 40 atomic% or more. The oxygen content of the upper layer 6 is preferably 10 atomic% or more, more preferably 15 atomic% or more. The oxygen content of the upper layer 6 is preferably less than 40 atomic%, more preferably less than 30 atomic%. The nitrogen content of the upper layer 6 is preferably 5 atomic% or more, more preferably 7 atomic% or more. The nitrogen content of the upper layer 6 is preferably less than 20 atomic%, more preferably less than 15 atomic%. The carbon content of the upper layer 6 is preferably 5 atomic% or more, more preferably 7 atomic% or more. The carbon content of the upper layer 6 is preferably less than 20 atomic%, more preferably less than 15 atomic%. Because the chromium nitride layer 5 has an upper layer 6 composed of chromium-based materials, the surface reflectivity of the light-shielding film can be reduced (for example, the reflectivity relative to the exposure light of an ArF excimer laser (wavelength 193 nm) is less than 35%). From the above viewpoint, the film thickness of the upper layer 6 is preferably in the range of, for example, 2 nm to 10 nm, and more preferably 3 nm to 7 nm. Furthermore, in the configuration example shown in Figure 3, as described above, a hard mask layer 7 is provided on the upper layer 6. The configuration of the hard mask layer 7 is as described above, so the description will be omitted here. Furthermore, the masking substrate 10 of this first embodiment can be manufactured by forming the pattern forming thin film 2 on the substrate 1. The pattern forming thin film 2 is a chromium nitride monolayer film, a laminated film including a chromium nitride layer 5 and a hard masking layer 7 (Fig. 2), or a laminated film including a chromium nitride layer 5, an upper layer 6 composed of a chromium-based material, and a hard masking layer 7 (Fig. 3). While there are no particular limitations on the method for forming the thin film 2 used to form the above-mentioned pattern, sputtering is preferred as an example. Sputtering can form a uniform film with a fixed thickness, which is therefore preferable. Furthermore, the masking substrate 10 of this first embodiment is characterized by setting a quadrangular inner region (i.e., central region 21) with the center of the substrate 1 as a reference and one side being 1 μm on the surface of the thin film 2 for pattern formation (Fig. 7). When the arithmetic mean roughness Sa and the maximum height Sz are measured in the central region 21, Sa is 1.0 nm or less and Sz / Sa is 14 or less. Here, the arithmetic mean roughness Sa refers to the parameter used to evaluate surface roughness as defined in ISO 25178, and it extends the parameter Ra (arithmetic mean height of the line) currently used to represent the two-dimensional surface properties defined in ISO 4287 and JIS B0601 to a three-dimensional (surface) parameter. Specifically, it represents the average of the absolute values ​​of the height differences (Z(x, y)) measured from the average surface (minimum square plane, etc.) of each measurement point in the reference region A. The calculation formula is shown below. Furthermore, the maximum height Sz refers to the parameter Rz (maximum height) of the line roughness extended to three dimensions (surface), and is the sum of the maximum mountain height Sp and the maximum valley depth Sv in the reference region A. That is, the maximum height Sz is as follows. Sz=Sp+Sv Here, the aforementioned maximum mountain height Sp and maximum valley depth Sv refer to the parameters Rp and Rv of the line roughness, respectively, extended to three dimensions (surface). The maximum mountain height Sp represents the maximum height of the mountain top in the reference region A, and the maximum valley depth Sv represents the maximum depth of the valley bottom in the reference region A. These parameters Sz, Sp, and Sv are also defined according to ISO 25178. In this disclosure, the reference region A refers to the inner quadrilateral region (i.e., central region 21) with the center of the substrate 1 as a reference and one side being 1 μm, relative to the surface of the pattern forming film 2, and the adjacent region 22 described later (see FIG7). Furthermore, in this disclosure, the arithmetic mean roughness Sa, maximum height Sz, and Sz / Sa values ​​are calculated by performing AFM measurements on the surface of the pattern-forming thin film 2 using a 1 μm square. As mentioned above, after reviewing the data, the inventors found that when using AFM to measure the surface of a pattern-forming film (e.g., a light-shielding film) on a mask substrate, there were significant differences in the arithmetic mean roughness Sa and the ratio of maximum height Sz to arithmetic mean roughness Sa (maximum height Sz / arithmetic mean roughness Sa) between measurement areas with and without minor defects. Therefore, it was determined that it is preferable to use the arithmetic mean roughness Sa and Sz / Sa values ​​calculated by performing AFM measurements on the pattern-forming film within a quadrangular region with one side measuring 1 μm as parameters to define the presence or absence of minor defects on the pattern-forming film of the mask substrate. The mask substrate 10 of this first embodiment has a rectangular inner region (i.e., central region 21) with a side length of 1 μm, defined on the surface of the pattern forming film 2, with the center of the substrate 1 as a reference. When the arithmetic mean roughness Sa and the maximum height Sz are measured in the central region 21, Sa is 1.0 nm or less, and Sz / Sa is 14 or less, thereby becoming a mask substrate with fewer minute defects on the surface of the pattern forming film. Furthermore, Sz / Sa is preferably 12 or less, and Sa is preferably 0.6 or less. Therefore, when using a defect inspection device with the highest wavelength of 193nm inspection light as described above to inspect the mask substrate for defects, there will be no problem such as inspection overflow during the inspection. Furthermore, this disclosure defines a quadrilateral inner region (i.e., central region 21) with the center of the substrate 1 as a reference and one side being 1 μm on the surface of the aforementioned pattern forming film 2, and limits the values ​​of Sa and Sz / Sa when measuring the arithmetic mean roughness Sa and the maximum height Sz in this central region 21. Based on the inventors' review, it was found that when many micro-defects occur in the pattern forming area of ​​the pattern forming film (e.g., a quadrilateral mask substrate with one side being 6 inches, and the pattern forming area being 132 nm × 132 nm), the probability that micro-defects also exist in the central region 21 of the pattern forming film is quite high. Therefore, the fewer micro-defects in the aforementioned central region 21 of the pattern forming film are related to whether the number of micro-defects in at least the pattern forming area of ​​the pattern forming film will be the number that will not cause adverse effects during defect inspection (e.g., less than 100). Based on the above, this disclosure is limited to the values ​​of Sa and Sz / Sa when measured in the aforementioned central region 21. When a minor defect occurs in the chromium nitride monolayer film 2 used for pattern forming, even if a hard masking layer 7 is formed on it, minor defects originating from the minor defect in the chromium nitride monolayer film will still occur on the surface of the hard masking layer 7. Similarly, if a minor defect occurs in the chromium nitride monolayer film 2 used for pattern forming, even if an upper layer 6 or a hard masking layer 7 is formed on it, minor defects originating from the minor defect in the chromium nitride monolayer film will still occur on the surface of the upper layer 6 or the hard masking layer 7. Therefore, Sa and Sz / Sa, calculated by performing AFM measurements on the surface of the uppermost layer 6 or the hard masking layer 7 of the pattern forming film 2 within a quadrangular area with one side measuring 1 μm, can be used as indicators to judge the minor defects on the surface of the chromium nitride monolayer film or the chromium nitride layer 5. Furthermore, as shown in Figure 7, this disclosure pertains to the surface of the aforementioned pattern-forming thin film 2, where eight quadrilateral inner regions (i.e., adjacent regions 22) with one side measuring 1 μm are defined around the central region 21 and adjacent to its outer perimeter (including four sides and four corners). When measuring the arithmetic mean roughness Sa and maximum height Sz of all the aforementioned adjacent regions 22, preferably, all Sa are 1.0 nm or less, and all Sz / Sa are 14 or less. More preferably, all Sz / Sa are 12 or less, and all Sa are 0.6 or less. None of the eight adjacent regions 22 overlap with other adjacent regions; rather, the entire outer perimeter of the central region 21 is surrounded by the eight adjacent regions 22. That is, the sides of four of the eight adjacent regions 22 correspond to the four sides of the central region 21, respectively. Furthermore, each of the other four adjacent regions has a corner that is connected to one of the four corners of the central region 21. Each adjacent region 22, in addition to having a side that corresponds to one side of the central region 21, has two sides that correspond to one side of each of the two other adjacent regions 22. By ensuring that all Sa values ​​in the adjacent region 22 of the mask substrate are below 1.0 nm and all Sz / Sa values ​​are below 14, the reliability of miniature defects on the surface of the thin film for pattern formation is further improved. Furthermore, in this disclosure, the maximum height Sz of the aforementioned central region 21 is preferably 10 nm or less. By ensuring that the Sz / Sa ratio of the mask substrate measured in the aforementioned central region 21 is 14 or less, and the maximum height Sz is 10 nm or less, the reliability of miniature defects on the surface of the patterned thin film is further improved. Furthermore, in all the aforementioned adjacent regions 22, the maximum height Sz is also preferably 10 nm or less. Furthermore, in this disclosure, the root mean square roughness Sq of the aforementioned central region 21 is preferably below 1.0 nm. Here, the root mean square roughness Sq refers to a parameter used to evaluate surface roughness as defined by ISO 25178, similar to the arithmetic mean roughness Sa or the maximum height Sz mentioned above. It extends the parameter Rq (root mean square roughness of lines) currently used to represent two-dimensional surface properties as defined by ISO 4287 and JIS B0601 to three-dimensional (surface) surfaces. The formula for calculating Sq is as follows. [Formula 2] By ensuring that the root mean square roughness Sq of the central region 21 is 1.0 nm or less, the Line Edge Roughness (LER) of the pattern sidewalls when the pattern is patterned using a thin film will be improved. The root mean square roughness Sq is preferably 0.8 nm or less. Furthermore, in all the aforementioned adjacent regions 22, the root mean square roughness Sq is preferably 1.0 nm or less, and more preferably 0.8 nm or less. Furthermore, in this first embodiment, when the mask substrate 10 performs defect inspection on the surface of the pattern forming film 2 using a defect inspection device with an inspection light of 193 nm wavelength, and obtains the distribution of convex defects in the inner quadrilateral region (i.e., the pattern forming region) with a side length of 132 mm, there are convex defects (i.e., micro-defects) with a height of 10 nm or less in the pattern forming region, and the number of such micro-defects in the pattern forming region is 100 or less. That is, the number of micro-defects in at least the pattern forming region of the pattern forming film 2 is the number that will not cause adverse effects during defect inspection. For example, specifically, a defect inspection device using an inspection light with a wavelength of 193nm can be used to inspect the surface of a pattern-forming film (light-shielding film or hard masking film, etc.) on a mask substrate to obtain a coordinate map of the defect. AFM is then used to measure the height of the defect in all areas where defects exist (except for obvious traditional foreign matter defects or dent defects) and to count the number of micro-defects. [Second Implementation Type] Figure 4 is a schematic cross-sectional view showing a second embodiment of the masking substrate related to this disclosure. As shown in Figure 4, the masking substrate 30 related to the second embodiment of this disclosure is a masking substrate having a phase shift film 8 between the substrate 1 and the pattern forming film 2. The aforementioned phase-shifting film 8 is a film having, for example, the following functions: allowing exposure light from an ArF excimer laser (wavelength 193 nm) to pass through with a transmittance of 8% or more; and causing a phase difference of 150 degrees to 210 degrees between the exposure light passing through the phase-shifting film 8 and the exposure light passing through the same distance in air as the thickness of the phase-shifting film 8. The aforementioned mask substrate 30, equipped with the phase-shifting film 8 having the above-described functions, is a mask substrate for manufacturing a halftone phase-shifting mask. The light-shielding film provided on a phase-shifting film with a high transmittance of 8% or more is required to have a high optical density relative to the exposure light. Therefore, the effect obtained by applying the aforementioned chromium nitride monolayer film or chromium nitride layer 5 (Figs. 2 and 3) to the pattern-forming thin film 2 is very significant. In the masking substrate 30 of this second embodiment, although the phase shift film 8 is formed of, for example, a silicon-containing material, the composition of the phase shift film 8 used in this second embodiment is not particularly limited. For example, the composition of the phase shift film in the phase shift mask currently used can be applied. In addition to materials containing silicon, transition metals and silicon, the aforementioned phase-shifting film 8 is formed of a material containing at least one element among nitrogen, oxygen and carbon in order to improve the film's optical properties (light transmittance, phase difference, etc.) and physical properties (etching rate, etching selectivity with other films (layers), etc.). Specifically, the aforementioned silicon-containing materials are preferably silicon-containing nitrides, oxides, carbides, nitrogen oxides (nitrogen oxides), carbon oxides (carbon oxides), or carbon oxynitrides (carbon oxynitrides). Furthermore, the aforementioned materials containing transition metals and silicon are preferably transition metal silicides, or nitrides, oxides, carbides, oxynitrides, or carbon oxides of transition metal silicides, or materials containing carbon oxynitrides. Transition metals that can be used include molybdenum, tantalum, tungsten, titanium, chromium, hafnium, nickel, vanadium, zirconium, ruthenium, rhodium, and niobium. Among these, molybdenum is particularly preferred. Alternatively, the phase-shifting film 8 described above can be applied to either a single-layer structure or a laminated structure consisting of a low-transmittance layer and a high-transmittance layer. While the preferred thickness of the phase-shifting film 8 varies depending on the material, it is best to adjust it appropriately from the viewpoint of phase-shifting function and light transmittance. A typical film thickness is, for example, below 100 nm, and more preferably below 80 nm. The method for forming the phase-shifting film 8 is not particularly limited; sputtering is a preferred example. Furthermore, since the details of the substrate 1 and the pattern forming film 2 in the masking substrate 30 of this second embodiment are the same as those in the first embodiment, they are omitted here for repetition. Furthermore, the method for forming the pattern-forming thin film 2 in the masking substrate 30 of this second embodiment is also preferably sputtering, just as in the first embodiment. Also, the thicknesses of each film constituting the pattern-forming thin film 2, whether it is a chromium nitride monolayer film or a laminated film including the chromium nitride layer 5 shown in Figures 2 and 3, an upper layer 6 made of chromium-based material, a hard masking layer 7, etc., are the same as in the first embodiment. In the masking substrate 30 of this second embodiment, in the laminated structure of the phase-shifting film 8 and the pattern-forming thin film 2, the optical density (OD) relative to the exposure light of the ArF excimer laser (wavelength 193 nm) is preferably 3.3 or higher. In the masking substrate 30 of this second embodiment, the feature is that a quadrilateral inner region (i.e., central region 21) with the center of the substrate 1 as a reference and one side of 1 μm is set on the surface of the above-mentioned pattern forming film 2. When the arithmetic mean roughness Sa and the maximum height Sz are measured in the central region 21, Sa is 1.0 nm or less and Sz / Sa is 14 or less. The mask substrate 30 of this second embodiment has a rectangular inner region (i.e., a central region 21) with a side length of 1 μm, defined on the surface of the pattern-forming thin film 2, with the center of the substrate 1 as a reference. When the arithmetic mean roughness Sa and the maximum height Sz are measured in the central region 21, Sa is 1.0 nm or less, and Sz / Sa is 14 or less, thus providing a mask substrate with fewer minute defects on the surface of the pattern-forming thin film. Furthermore, Sz / Sa is preferably 12 or less, and Sa is preferably 0.6 nm or less. Furthermore, regarding this second embodiment, for the surface of the aforementioned pattern-forming thin film 2, eight quadrilateral inner regions (i.e., adjacent regions 22) with sides of 1 μm are set adjacent to the outer periphery of the aforementioned central region 21. When measuring the arithmetic mean roughness Sa and the maximum height Sz of all the aforementioned adjacent regions 22, preferably, all Sa are 1.0 nm or less, and all Sz / Sa are 14 or less. More preferably, all Sz / Sa are 12 or less, and even more preferably, all Sa are 0.6 nm or less. By ensuring that all Sa values ​​in the aforementioned eight adjacent regions 22 of the masking substrate are below 1.0 nm and all Sz / Sa values ​​are below 14, the reliability of miniature defects on the surface of the thin film used for pattern formation will be further improved. Furthermore, regarding this second embodiment, the maximum height Sz of the aforementioned central region 21 is preferably 10 nm or less. By ensuring that the Sz / Sa ratio of the mask substrate measured in the aforementioned central region 21 is 14 or less, and the maximum height Sz is 10 nm or less, the reliability of miniature defects on the surface of the patterned thin film is further improved. Furthermore, in all of the aforementioned adjacent regions 22, the maximum height Sz is also preferably 10 nm or less. Furthermore, regarding this second embodiment, the root mean square roughness Sq of the central region 21 is preferably 1.0 nm or less. By ensuring that the root mean square roughness Sq of the central region 21 is 1.0 nm or less, the Line Edge Roughness (LER) of the pattern sidewalls when the pattern is patterned with a thin film will be improved. The root mean square roughness Sq of the central region 21 is preferably 0.8 nm or less. Further, in all the aforementioned adjacent regions 22, the root mean square roughness Sq is preferably 1.0 nm or less, and more preferably 0.8 nm or less. Furthermore, regarding the mask substrate 30 of this second embodiment, when the surface of the pattern forming film 2 is inspected using a defect inspection device with an inspection light of 193 nm to obtain the distribution of convex defects in the inner quadrilateral region (i.e., the pattern forming region) with a side length of 132 mm, there are convex defects (i.e., micro-defects) with a height of 10 nm or less in the pattern forming region, and the number of such micro-defects in the pattern forming region is 100 or less. That is, the number of micro-defects in at least the pattern forming region of the pattern forming film 2 is such that they will not cause adverse effects during defect inspection. [Manufacturing method for transfer printing mask] This disclosure also provides a method for manufacturing a transfer mask made from the mask substrate described above. Figure 5 is a schematic cross-sectional view showing the manufacturing process of the transfer mask using the mask substrate 10 of the first embodiment described above. The manufacturing method of the transfer mask disclosed herein includes at least a step of forming a transfer pattern on the pattern forming film 2 by dry etching using a resist film having a transfer pattern as a mask. The method for manufacturing a transfer mask disclosed herein first involves forming a resist film 3 for electron line drawing on the surface of a mask substrate 10 using, for example, a spin coating method, to a specific film thickness. Next, a specific pattern is drawn onto the resist film using electron lines. After drawing, a specific resist film pattern 3a is formed by development (see Figures 5(a) to (c)). This resist film pattern 3a has the element pattern required to become the final transfer pattern. Next, using the aforementioned resist film pattern 3a as a mask, a transfer pattern 2a is formed on the pattern forming film 2 (light shielding film) whose main part is composed of chromium-based materials by dry etching using a mixture of chlorine-based gas and oxygen (see Figure 5(d)). After removing the remaining resist film pattern 3a, the binary transfer mask 20 is completed, which has a fine pattern 2a on the substrate 1 that becomes the transfer pattern for the pattern forming film (light shielding film) (see Figure 5(e)). In this way, by using a mask substrate 10 with fewer minute defects on the surface of the pattern forming film, a transfer mask 20 with a high-precision micro-transfer pattern can be manufactured. Furthermore, when the aforementioned pattern-forming thin film 2 has a hard mask layer 7 made of silicon-based material, the process includes a step of forming a transfer pattern on the hard mask layer 7 by using the aforementioned resist film pattern 3a as a mask and dry etching with fluorine-based gas. Then, a transfer pattern is formed on the chromium-based light-shielding film in the pattern-forming thin film made of chromium-based material by dry etching with the hard mask layer 7 having the transfer pattern as a mask. Figure 6 is a schematic cross-sectional view showing the manufacturing process of the transfer mask using the mask substrate 30 of the aforementioned second embodiment. The manufacturing method of the transfer mask using the mask substrate 30 includes at least the following steps: forming a transfer pattern on the pattern forming thin film 2 by dry etching using a resist film with a transfer pattern as a mask, and forming a transfer pattern on the phase shift film 8 by dry etching using a pattern forming thin film 2 with a transfer pattern as a mask. The method for manufacturing the transfer mask first involves forming a resist film for electron line drawing on the surface of the mask substrate 30 using, for example, spin coating and with a specific film thickness. A specific pattern is drawn onto the resist film using electron lines, and after drawing, a specific resist film pattern 9a is formed by development (see Figure 6(a)). The resist film pattern 9a has the required element pattern that will become the final transfer pattern and should be formed on the phase shift film 8. Next, using the aforementioned resist film pattern 9a as a mask, a transfer pattern 2a is formed on the pattern forming film 2 (light shielding film) whose main part is composed of chromium-based materials by dry etching using a mixture of chlorine-based gas and oxygen (see Figure 6(b)). Next, using the transfer pattern 2a formed on the above-mentioned pattern forming film 2 as a mask, and by dry etching using fluorine gas, a transfer pattern 8a is formed on the phase shift film 8 made of silicon material (see Figure 6(c)). Next, the same resist film as described above is formed on the entire surface of the mask substrate on which the above-mentioned transfer patterns 2a and 8a are formed, and a specific light-shielding pattern (e.g., a light-shielding strip pattern) is drawn on the resist film. After drawing, a resist film pattern 9b with a specific light-shielding pattern is formed on the above-mentioned transfer pattern 2a by development (see Figure 6(d)). Next, by dry etching using a mixture of chlorine-based gas and oxygen, and using the resist pattern 9b as a mask, a pattern 2b having the light-shielding pattern is formed on the pattern forming film 2 (see Figure 6(e)). In the manner described above, a halftone phase shift mask (transfer mask) 40 is completed, which has a fine pattern 8a of the phase shift film 8 that becomes a transfer pattern and a light-shielding pattern (light-shielding strip pattern) 2b of the outer peripheral region on the substrate 1 (see Figure 6(e)). Furthermore, in the aforementioned manufacturing process, when the pattern forming film 2 has a hard mask layer 7 made of silicon-based material, it also includes a process of forming a transfer pattern on the hard mask layer 7 by using the resist film pattern 9a as a mask and dry etching with fluorine-based gas. Then, by dry etching with the hard mask layer 7 having the transfer pattern as a mask, the aforementioned transfer pattern 2a is formed on the chromium-based light-shielding film in the pattern forming film made of chromium-based material. In this way, by using a mask substrate 30 with fewer minute defects on the surface of the pattern forming film, a transfer mask (half-tone phase shift mask) 40 with a high-precision micro-transfer pattern can be manufactured. [Semiconductor device manufacturing methods] This disclosure also provides a method for manufacturing a semiconductor device, which includes a step of using a transfer mask manufactured by the above-described method for manufacturing a transfer mask to expose and transfer a transfer pattern onto a resist film on a semiconductor substrate. The semiconductor device manufacturing method disclosed herein includes a step of using a transfer mask 20 manufactured from, for example, the mask substrate 10 of the first embodiment described above, or a transfer mask 40 manufactured from the mask substrate 30 of the second embodiment described above, and exposing and transferring the transfer pattern of the transfer mask onto a resist film on a semiconductor substrate using photolithography. According to this semiconductor device manufacturing method, high-quality semiconductor devices with device patterns having excellent pattern precision can be manufactured. <Example> The following examples will illustrate the implementation of this disclosure in more detail. (Example 1) This embodiment 1 relates to a mask substrate 30 used in the manufacture of a transfer mask that uses an ArF excimer laser with a wavelength of 193 nm as the exposure light. The masking substrate 30 used in this embodiment 1 has a structure in which a phase-shifting film 8, a chromium nitride-based layer 5 as a pattern-forming thin film 2, an upper layer 6 made of chromium-based material, and a hard masking layer 7 are sequentially deposited on a light-transmitting substrate 1 (refer to Figures 4 and 3 above. The symbols correspond to the symbols in the figures). In this embodiment 1, the light-shielding film is formed by the deposition of the aforementioned chromium nitride-based layer 5 and the upper layer 6 made of chromium-based material. The mask base 30 is made in the following manner. A light-transmitting substrate 1 (approximately 152 mm × 152 mm × approximately 6.35 mm thick) made of synthetic quartz glass is prepared. The main surface and end face of the light-transmitting substrate 1 are ground to a specific surface roughness (e.g., the root mean square roughness Rq of the main surface is less than 0.2 nm). First, the aforementioned transparent substrate 1 is placed in a monolithic DC sputtering apparatus. A mixed target of molybdenum (Mo) and silicon (Si) (Mo:Si = 8 atomic%: 92 atomic%) is used, and a mixed gas of argon (Ar), oxygen (O2), nitrogen (N2) and helium (He) is used as the sputtering gas. By DC sputtering, a phase-shifting film 8 consisting of a MoSiON film (Mo: 10 atomic%, Si: 45 atomic%, O: 5 atomic%, N: 40 atomic%) containing molybdenum, silicon, oxygen and nitrogen is formed on the surface of the aforementioned transparent substrate 1 with a thickness of 68 nm. Next, the transparent substrate 1 on which the phase-shifting film 8 is formed was removed from the sputtering apparatus, and the phase-shifting film 8 on the transparent substrate was subjected to heat treatment in the atmosphere. The heat treatment was performed at 450°C for 30 minutes. After measuring the transmittance and phase shift of the heat-treated phase-shifting film 8 at the wavelength (193 nm) of the ArF excimer laser using a phase shift measurement device, the results were a transmittance of 8.9% and a phase shift of 175.2 degrees. Next, the transparent substrate 1 on which the phase shift film 8 is formed is introduced into the sputtering apparatus again. Using a target material made of chromium and a mixed gas of argon (Ar), nitrogen (N2) and helium (He) (flow ratio Ar:N2:He=15:10:30, pressure 0.2Pa) as the sputtering gas, a chromium nitride layer 5 containing chromium and nitrogen (Cr:86 atomic%, N:14 atomic%) is formed on the phase shift film 8 with a thickness of 43 nm by DC sputtering. Next, using the same chromium target as described above, and a mixture of argon (Ar), carbon dioxide (CO2), nitrogen (N2), and helium (He) (flow rate ratio Ar:CO2:N2:He = 16:30:10:30, pressure 0.2 Pa) as the sputtering gas, a light-shielding film consisting of chromium, oxygen, carbon, and nitrogen (Cr: 55 atomic%, O: 24 atomic%, C: 11 atomic%, N: 10 atomic%) was formed on the aforementioned chromium nitride layer 5 using DC sputtering to achieve a thickness of 6 nm. A two-layer chromium-based light-shielding film with a total thickness of 49 nm was thus formed. In the laminated structure of the phase-shifting film 8 and the light-shielding film (the lamination of the chromium nitride layer 5 and the upper layer 6), the optical concentration of the exposure light relative to the ArF excimer laser (wavelength 193nm) is 3.5. Next, the light-transmitting substrate 1, up to the light-shielding film, is placed in a monolithic DC sputtering apparatus. A target material made of silicon (Si) is used, and a mixture of argon (Ar), oxygen (O2), and nitrogen (N2) is used as the sputtering gas. By DC sputtering, a hard mask layer 7 consisting of a SiON film (Si: 34 atomic%, O: 60 atomic%, N: 6 atomic%) containing silicon, oxygen, and nitrogen is formed on the upper layer 6 with a thickness of 8 nm. The masking substrate 30 of this embodiment 1 is produced in the manner described above. For the surface of the mask substrate 30 of this embodiment (i.e., the surface of the hard mask layer 7), a quadrilateral inner region (i.e., central region 21) with a side length of 1 μm and the center of the substrate 1 as a reference is set. AFM measurements are performed in this central region 21, and the arithmetic mean roughness Sa, maximum height Sz, and Sz / Sa values ​​are calculated from the measurement results. The results are: in the mask substrate of this embodiment, Sa = 0.594 nm, Sz = 6.71 nm, and Sz / Sa = 11.30. Furthermore, the root mean square roughness Sq of the central region 21 is 0.75 nm. Furthermore, for the surface of the hard mask layer 7 of the mask substrate 30 in this embodiment 1, eight quadrilateral inner regions (i.e., adjacent regions 22) with one side of 1 μm are set in a manner that is adjacent to the outer periphery of the central region 21. AFM measurement is performed on these adjacent regions 22. After measuring the arithmetic mean roughness Sa and the maximum height Sz in all adjacent regions 22, the results confirm that Sa is less than 1.0 nm in all adjacent regions 22, and Sz / Sa is less than 14 in all of them. Furthermore, a defect inspection device, Teron (manufactured by KLA Corporation), using inspection light with a wavelength of 193 nm, was used to inspect the surface of the mask substrate 30 of this embodiment for defects, thereby obtaining the distribution of defects (defect coordinate map) in the inner quadrilateral region (i.e., the pattern forming region) with a side length of 132 mm. Then, for all areas where defects exist (excluding obvious foreign matter defects or dent defects), the height of the defect was measured using AFM, and the number of convex defects (i.e., micro-defects) with a height of less than 10 nm in the pattern forming region was calculated. The result showed that there were 2 such micro-defects in the pattern forming region of the mask substrate 30 of this embodiment. As can be seen from the above, the masking substrate 30 of this embodiment 1 is a masking substrate with fewer surface defects by making the arithmetic mean roughness Sa of the central region 21 less than 1.0 nm and Sz / Sa less than 14. Next, a transfer mask is manufactured using the mask substrate 30 and in accordance with the manufacturing process shown in FIG6. First, a chemically amplified resist (PRL009 manufactured by FUJIFILM Electronic Materials) for electron wire drawing is coated onto the mask substrate 30 using spin coating, and then subjected to a specific baking process to form a resist film with a thickness of 80 nm. Next, a specific element pattern (a pattern corresponding to the transfer pattern to be formed on the phase shift film 8) is drawn on the resist film using an electron wire drawing machine, and then the resist film is developed to form a resist pattern 9a. Next, using the aforementioned resist film pattern 9a as a mask, a transfer pattern is formed on the hard mask layer 7 by dry etching using fluorine-based gas. Next, after removing the remaining resist film pattern 9a, the transfer pattern formed on the hard mask layer 7 is used as a mask, and the two-layer structure of the light-shielding film of CrN (chromium nitride layer 5) and CrOCN (upper layer 6) is continuously etched by dry etching using a mixed gas of chlorine (Cl2) and oxygen (O2) (Cl2:O2=13:1 (flow ratio)) to form the transfer pattern on the light-shielding film. Next, the transfer pattern is formed on the phase shift film 8 (phase shift film pattern 8a) by dry etching with fluorine gas (SF6) and using the transfer pattern formed on the light-shielding film of the above two-layer structure as a mask. Next, a resist film identical to the one described above is formed on the entire surface of the mask substrate on which the patterns of the light-shielding film and the phase-shifting film are formed, and a specific light-shielding pattern (light-shielding strip pattern) is drawn on this resist film. After drawing, a resist film pattern 9b with a specific light-shielding pattern is formed on the pattern of the light-shielding film by development. Next, by dry etching with a mixture of chlorine and oxygen gases, and using the resist pattern 9b as a mask, a pattern with the light-shielding pattern (equivalent to pattern 2b in FIG6) is formed on the light-shielding film with the above two-layer structure. In the manner described above, a halftone phase-shift mask (transfer mask) 40 is completed, which has a pattern 8a of a phase-shift film that becomes a transfer pattern and a light-shielding pattern (light-shielding strip pattern) in the outer peripheral region on a light-transmitting substrate 1 (see Figure 6(e)). After inspecting the phase shift mask 40 obtained by the mask inspection device, it can be confirmed that a fine pattern of phase shift film is formed within the allowable range of the design value. Furthermore, an AIMS193 (manufactured by Carl Zeiss) was used to simulate the exposure transfer image of the phase shift mask 40 when the resist film transferred onto the semiconductor device is exposed with exposure light at a wavelength of 193 nm. After verifying the exposure transfer image obtained from the simulation, it was found to fully meet the design specifications. Therefore, the phase shift mask 40 manufactured from the mask substrate 30 of Example 1 can perform high-precision exposure transfer of the resist film on the semiconductor device. (Example 2) This embodiment 2 relates to a mask substrate 30 used in the manufacture of a transfer mask that uses an ArF excimer laser with a wavelength of 193 nm as the exposure light. The masking substrate 30 used in this embodiment 2 has a structure in which a phase-shifting film 8, a chromium nitride-based layer 5 serving as a pattern-forming thin film 2, and a hard masking layer 7 are sequentially deposited on a light-transmitting substrate 1 (refer to Figures 4 and 2 above. The symbols correspond to the symbols in the figures). In this embodiment 2, the light-shielding film is formed by a single layer of the aforementioned chromium nitride-based layer 5. The mask base 30 is made in the following manner. First, a transparent substrate 1 (synthetic quartz substrate) prepared in the same manner as in Example 1 is placed in a monolithic DC sputtering apparatus to form a phase-shifting film 8, which is the same as in Example 1. Next, the transparent substrate 1 on which the phase-shifting film 8 is formed is again introduced into the sputtering apparatus. Using a chromium target, a mixture of argon (Ar), nitrogen (N2), and helium (He) gas (flow ratio Ar:N2:He=30:5:50, pressure 0.3Pa) is used as the sputtering gas. By DC sputtering, a chromium nitride layer 5 containing chromium and nitrogen (Cr:94 atomic%, N:6 atomic%) is formed on the phase-shifting film 8 to a thickness of 48 nm. In this way, a single-layer chromium-based light-shielding film is formed. In the laminated structure of the phase-shifting film 8 and the light-shielding film (the chromium nitride layer 5), the optical concentration of the exposure light relative to the ArF excimer laser (wavelength 193nm) is 3.6. Next, the light-transmitting substrate 1, up to the light-shielding film described above, is placed in a monolithic DC sputtering apparatus, and a hard shielding layer 7 composed of SiON film is formed in the same manner as in Example 1. The masking substrate 30 of this embodiment 2 is produced in the manner described above. For the surface of the mask substrate 30 in Embodiment 2 (i.e., the surface of the hard mask layer 7), a quadrilateral inner region (i.e., central region 21) with a side length of 1 μm and the center of the light-transmitting substrate 1 as a reference is defined. AFM measurements are performed in this central region 21, and the arithmetic mean roughness Sa, maximum height Sz, and Sz / Sa values ​​are calculated from the measurement results. The results are as follows: in the mask substrate of Embodiment 2, Sa = 0.462 nm, Sz = 6.22 nm, and Sz / Sa = 13.46. Furthermore, the root mean square roughness Sq in the central region 21 is 0.592 nm. Furthermore, for the surface of the hard mask layer 7 of the mask substrate 30 in this embodiment 2, eight quadrilateral inner regions (i.e., adjacent regions 22) with one side of 1 μm are set in a manner that is adjacent to the outer periphery of the central region 21. AFM measurement is performed on these adjacent regions 22. After measuring the arithmetic mean roughness Sa and the maximum height Sz in all adjacent regions 22, the results confirm that Sa is less than 1.0 nm in all adjacent regions 22, and Sz / Sa is less than 14 in all of them. Furthermore, for the surface of the mask substrate 30 in Embodiment 2, a defect inspection device, Teron (manufactured by KLA Corporation), using inspection light with a wavelength of 193 nm, was used to perform defect inspection to obtain the distribution (defect coordinate map) of convex defects in the inner quadrilateral region (i.e., the pattern forming region) with a side length of 132 mm. Then, for all areas where defects exist (excluding obvious foreign matter defects or dent defects), the height of the defects was measured using AFM, and the number of convex defects (i.e., micro-defects) with a height of less than 10 nm in the pattern forming region was calculated. The result was that the number of such micro-defects existing in the pattern forming region of the mask substrate 30 in Embodiment 2 was 72. As can be seen from the above, the masking substrate 30 of this embodiment 2 is also a masking substrate with fewer surface micro-defects by making Sa in the central region 21 less than 1.0 nm and Sz / Sa less than 14. If we take into account the results of the above embodiment 1, it can be seen that by making the arithmetic mean roughness Sa of the pattern forming film of the mask substrate in the central region 21 less than 1.0 nm and all Sz / Sa less than 14, it can be ensured that the mask substrate has fewer micro-defects in at least the pattern forming region of the pattern forming film (the number of defects that will not cause adverse effects when performing defect inspection, for example, less than 100). Next, a transfer mask is manufactured using the mask substrate 30 described above and through the same process as in Example 1. First, a chemically amplified resist (PRL009 manufactured by FUJIFILM Electronic Materials) for electron wire drawing is coated onto the mask substrate 30 using spin coating, and then subjected to a specific baking process to form a resist film with a thickness of 80 nm. Next, a specific element pattern (a pattern corresponding to the transfer pattern to be formed on the phase shift film 8) is drawn on the resist film using an electron wire drawing machine, and then the resist film is developed to form a resist pattern 9a. Next, using the aforementioned resist film pattern 9a as a mask, a transfer pattern is formed on the hard mask layer 7 by dry etching using fluorine-based gas. Next, after removing the remaining resist film pattern 9a, the transfer pattern formed on the hard mask layer 7 is used as a mask, and the light-shielding film composed of CrN film (chromium nitride layer 5) is dry-etched by using a mixed gas of chlorine (Cl2) and oxygen (O2) (Cl2:O2=13:1 (flow ratio)) to form a transfer pattern on the light-shielding film. Next, the transfer pattern is formed on the phase shift film 8 (phase shift film pattern 8a) by dry etching with fluorine gas (SF6) and using the transfer pattern formed on the above-mentioned CrN light-shielding film as a mask. Next, a resist film identical to the one described above is formed on the entire surface of the mask substrate on which the patterns of the light-shielding film and the phase-shifting film are formed, and a specific light-shielding pattern (light-shielding strip pattern) is drawn on this resist film. After drawing, a resist film pattern 9b with a specific light-shielding pattern is formed on the pattern of the light-shielding film by development. Next, by dry etching with a mixture of chlorine-based gas and oxygen, and using the resist pattern 9b as a mask, a pattern with the light-shielding pattern (equivalent to pattern 2b in FIG. 6) is formed on the CrN light-shielding film. In the manner described above, a halftone phase-shift mask (transfer mask) 40 is completed, which has a pattern 8a of a phase-shift film that becomes a transfer pattern and a light-shielding pattern (light-shielding strip pattern) in the outer peripheral region on a light-transmitting substrate 1 (see Figure 6(e)). After inspecting the phase shift mask 40 of this embodiment 2 with a mask inspection device, it can be confirmed that a fine pattern of phase shift film is formed within the allowable range of the design value. Furthermore, an AIMS193 (manufactured by Carl Zeiss) was used to simulate the exposure transfer image of the phase shift mask 40 when the resist film transferred onto the semiconductor device is exposed with exposure light at a wavelength of 193 nm. After verifying the exposure transfer image obtained from the simulation, it was found to fully meet the design specifications. Therefore, the phase shift mask 40 manufactured from the mask substrate 30 of Example 2 can perform high-precision exposure transfer of the resist film on the semiconductor device. (Comparative Example 1) The masking substrate of Comparative Example 1 was fabricated in the same manner as that of Example 1, except that the light-shielding film was a single layer of CrOC. That is, the masking substrate of Comparative Example 1 has a structure in which a light-shielding film composed of a phase-shifting film and a CrOC film and a hard masking layer are sequentially deposited on a light-transmitting substrate. The mask base for Comparative Example 1 is created as follows. First, a transparent substrate (synthetic quartz substrate) prepared in the same manner as in Example 1 is placed in a monolithic DC sputtering apparatus to form a phase-shifting film similar to that in Example 1. Next, the substrate with the aforementioned phase-shifted film is again fed into a sputtering apparatus. Using a chromium target and a mixture of argon (Ar), carbon dioxide (CO2), and helium (He) as the sputtering gas (flow ratio Ar:CO2:He = 16:30:30, pressure 0.2 Pa), a light-shielding film containing chromium, oxygen, and carbon (Cr: 71 atomic%, O: 15 atomic%, C: 14 atomic%) is formed on the aforementioned phase-shifted film with a thickness of 48 nm. A single-layer chromium-based light-shielding film is thus formed. In the laminated structure of the phase-shifting film and the light-shielding film (CrOC film), the optical concentration of the exposure light relative to the ArF excimer laser (wavelength 193nm) is 3.5. Next, a light-transmitting substrate with the aforementioned light-shielding film is placed in a monolithic DC sputtering apparatus, and a hard mask layer consisting of a SiON film containing silicon, oxygen, and nitrogen is formed on the aforementioned light-shielding film in the same manner as in Example 1. The mask base of Comparative Example 1 was made in the manner described above. For the surface of the mask substrate of Comparative Example 1 (i.e., the surface of the aforementioned hard mask layer), a quadrilateral inner region (i.e., central region 21) with a side length of 1 μm and the center of the substrate as a reference was defined. AFM measurements were performed on this central region 21, and the arithmetic mean roughness Sa, maximum height Sz, and Sz / Sa values ​​were calculated from the measurement results. The results for the mask substrate of Comparative Example 1 were: Sa = 0.515 nm, Sz = 11.1 nm, and Sz / Sa = 21.55. Furthermore, the root mean square roughness Sq of the central region 21 was 0.681 nm. Furthermore, on the surface of the hard mask layer of the mask substrate of Comparative Example 1, eight quadrilateral inner regions (i.e., adjacent regions 22) with one side of 1 μm were set in a manner that is adjacent to the outer periphery of the central region 21. AFM measurement was performed in these adjacent regions 22. After measuring Sa and Sz in all adjacent regions 22, the results showed that Sa was less than 1.0 nm in all adjacent regions 22, and Sz / Sa was greater than 14 in all of them. Furthermore, after performing defect inspection on the surface of the mask substrate of Comparative Example 1 using a Teron (manufactured by KLA Corporation) defect inspection device with a wavelength of 193nm inspection light and a pattern formation area in a quadrilateral inner region with one side of 132mm, many tiny defects were found. Due to the large number of defects, the inspection was terminated midway through (overflow). As can be seen from the above, a mask substrate that does not meet the conditions disclosed herein (i.e., in the central region 21, Sa is 1.0 nm or less and Sz / Sa is 14 or less) cannot be guaranteed to be a mask substrate with fewer minute defects in at least the patterning area of ​​the patterning film (the number of defects that will not cause adverse effects when performing defect inspection, for example, 100 or less). 1: Transparent substrate 2: Thin film for pattern formation 3: Resistor film 5: Chromium nitride series 6: Upper layer 7: Hard mask layer 8: Phase Shifting Film 10, 30: Masking base 20: Transfer mask (binary mask) 21: Central Region 22: Adjacent Area 40: Transfer mask (halftone phase shift mask)

Claims

1. A masking substrate having a pattern forming film on a substrate; the pattern forming film is a monolayer film containing chromium and nitrogen, or a multilayer film containing a chromium nitride system layer containing chromium and nitrogen; a quadrangular inner region (i.e., a central region) with the center of the substrate as a reference and one side being 1 μm is set on the surface of the pattern forming film, and when the arithmetic mean roughness Sa and the maximum height Sz are measured in the central region, Sa is 1.0 nm or less, and Sz / Sa is 14 or less; the chromium content of the monolayer film, excluding the surface layer on the opposite side of the substrate, is 60 atomic% or more, or the chromium content of the chromium nitride system layer of the multilayer film is 60 atomic% or more.

2. A masking substrate having a pattern forming film on a substrate; the pattern forming film is a monolayer film containing chromium and nitrogen, or a multilayer film containing a chromium nitride layer containing chromium and nitrogen; for the surface of the pattern forming film, a quadrangular inner region (i.e., a central region) with the center of the substrate as a reference and one side being 1 μm is set, and when the arithmetic mean roughness Sa and the maximum height Sz are measured in the central region, Sa is 1.0 nm or less, and Sz / Sa is 14 or less; the oxygen content of the monolayer film is less than 5 atomic%, or the oxygen content of the chromium nitride layer of the multilayer film is less than 5 atoms.

3. The masking substrate of claim 2, wherein the chromium content of the portion of the single-layer film excluding the surface layer opposite to the substrate is 60 atomic% or more, or the chromium content of the chromium nitride layer of the multilayer film is 60 atomic% or more.

4. The masking substrate of any one of claims 1 to 3 is configured with eight quadrilateral inner regions of 1 μm each, which are adjacent regions that do not overlap, on the surface of the pattern forming film, in a manner that is adjacent to and surrounds the entire outer perimeter of the central region. When the arithmetic mean roughness Sa and the maximum height Sz of all the adjacent regions are measured, all Sa are 1.0 nm or less, and all Sz / Sa are 14 or less.

5. The masking substrate of any one of claims 1 to 3, wherein the maximum height Sz of the central region is less than 10 nm.

6. The masking substrate of any one of claims 1 to 3, wherein the root mean square roughness Sq of the central region is less than 1.0 nm.

7. If the masking substrate of any one of the claims 1 to 3 is subjected to defect inspection on the surface of the pattern forming film by using a defect inspection device with an inspection light of 193 nm wavelength to obtain the distribution of convex defects in the inner quadrilateral region (i.e., the pattern forming region) with a side length of 132 mm, there are convex defects (i.e., micro-defects) with a height of less than 10 nm in the pattern forming region, and the number of such micro-defects in the pattern forming region is less than 100.

8. The masking substrate of any one of claims 1 to 3, wherein the nitrogen content of the portion of the single-layer film excluding the surface layer opposite to the substrate is 8 atomic% or more, or the nitrogen content of the chromium nitride layer of the multilayer film is 8 atomic% or more.

9. The masking substrate of any one of claims 1 to 3, wherein the multilayer film has a hard masking layer containing silicon and oxygen on the chromium nitride base layer.

10. The masking substrate of any one of claims 1 to 3, wherein the multilayer film has an upper layer containing chromium, oxygen and nitrogen on the chromium nitride layer.

11. The masking substrate of claim 10, wherein the multilayer film has a hard masking layer containing silicon and oxygen on the upper layer.

12. The masking substrate of any one of claims 1 to 3 has a phase-shifting film between the substrate and the pattern-forming film.

13. The mask substrate of claim 12, wherein the phase shift film has the function of allowing the exposure light of ArF excimer laser (wavelength 193nm) to pass through with a transmittance of 8% or more, and the function of causing the exposure light passing through the phase shift film to have a phase difference of 150 degrees or more and 210 degrees or less between the exposure light passing through the phase shift film and the exposure light passing through the same distance in the air as the thickness of the phase shift film.

14. The masking substrate of claim 12, wherein the optical concentration of the phase-shifting film and the pattern-forming film in the laminated structure is 3.3 or more relative to the exposure light of the ArF excimer laser (wavelength 193 nm).

15. A method for manufacturing a transfer mask, comprising a method for manufacturing a transfer mask using a mask substrate as described in any one of claims 1 to 11, comprising: a step of forming a transfer pattern on a thin film for pattern formation by dry etching using a resist film having a transfer pattern as a mask.

16. A method for manufacturing a transfer mask, comprising: a step of forming a transfer pattern on a pattern-forming thin film by dry etching using a resist film having a transfer pattern as a mask; and a step of forming a transfer pattern on a phase-shifting film by dry etching using a pattern-forming thin film having the transfer pattern as a mask.

17. A method for manufacturing a semiconductor device, comprising: a step of exposing and transferring a transfer pattern onto a resist film on a semiconductor substrate using a transfer mask obtained by a method for manufacturing a transfer mask as described in claims 15 or 16.

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