Method for manufacturing a mask blank substrate, a multilayer reflective film substrate, a mask blank, a transfer mask, and a semiconductor device.

Abstract

We provide a mask blank substrate, a multilayer reflective film substrate, and a mask blank that can be used to fabricate a transfer mask that can meet the desired overlay accuracy. [Solution] A mask blank substrate having two opposing main surfaces. Within the inner region of a rectangle with sides of 132 mm, with the center of the substrate as the reference point, a composite surface shape is generated from the surface shapes of the two main surfaces of the substrate, and the spatial frequency fr[mm] is calculated from the composite surface shape. -1 ] and power spectral density Pr[μm 2 / (mm -1 When calculating the relationship between ), 0.02[mm -1 ] or more 0.40[mm -1 Within the spatial frequency range fr below, at least 75% of the spatial frequency fr, Pr < (1.5141 × 10 -6 )×(fr -1.3717 The relationship ) is satisfied.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a mask blank substrate, a multilayer reflective film substrate, a mask blank, a transfer mask, and a semiconductor device, and more particularly to a method for manufacturing a mask blank substrate, a multilayer reflective film substrate, a mask blank, a transfer mask, and a semiconductor device for use in EUV lithography. [Background technology]

[0002] Generally, in the manufacturing process of semiconductor devices, fine patterns are formed using photolithography. This process typically involves the use of multiple transfer masks, also known as photomasks. These transfer masks generally consist of a fine pattern made of a thin metal film or similar material on a translucent glass substrate, and photolithography is also used in the manufacturing of these transfer masks.

[0003] In addition to the conventional binary-type mask, which has a light-shielding pattern made of chromium-based material on a translucent substrate, phase-shift type masks are also known as transfer masks. These phase-shift type masks have a structure in which a phase-shift film is present on a translucent substrate. This phase-shift film has a predetermined phase difference, and materials such as molybdenum silicide compounds are used. Furthermore, binary-type masks that use materials containing metal silicide compounds such as molybdenum as the light-shielding film are also coming into use. These binary-type masks and phase-shift type masks are collectively called transmissive masks, and the binary-type mask blanks and phase-shift type mask blanks used as master plates for transmissive masks are sometimes collectively called transmissive mask blanks.

[0004] Furthermore, in recent years, the semiconductor industry has seen a growing need for finer patterns that exceed the transfer limits of conventional photolithography methods using ultraviolet light, due to the increasing integration of semiconductor devices. To enable the formation of such fine patterns, EUV lithography, an exposure technique using extreme ultraviolet (EUV) light, is considered promising. Here, EUV light refers to light in the wavelength range of the soft X-ray region or vacuum ultraviolet region, specifically light with a wavelength of about 0.2 to 100 nm. Reflective masks have been proposed as transfer masks used in EUV lithography. Such reflective masks have a multilayer reflective film that reflects exposure light formed on a substrate, and an absorber film that absorbs exposure light is formed in a pattern on the multilayer reflective film.

[0005] The reflective mask is manufactured by forming an absorber pattern from a reflective mask blank having a substrate, a multilayer reflective film formed on the substrate, and an absorber film formed on the multilayer reflective film, using a method such as photolithography.

[0006] As a mask blank substrate used in the manufacture of such reflective masks, for example, the one disclosed in Patent Document 1 is known. In order to suppress the detection of false defects, the mask blank substrate in Patent Document 1 is measured using a white light interferometer at a resolution of 640 × 480 pixels in a 0.14 mm × 0.1 mm area on the main surface of the mask blank substrate on the side where the transfer pattern is formed, and the spatial frequency obtained is 1 × 10 -2 μm -1 More than 1μm -1 The power spectral density in the following cases is 4 × 10⁻⁶ 6 nm 4 The following is obtained by measuring a 1 μm × 1 μm region on the main surface with an atomic force microscope, and the spatial frequency is 1 μm. -1 The power spectral density in the above is 10 nm 4 It has the following structure: [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 5712336 [Overview of the project] [Problems that the invention aims to solve]

[0008] Exposure equipment used in semiconductor device manufacturing has evolved by gradually shortening the wavelength of the light source. To achieve finer pattern transfer, EUV lithography using EUV light with a wavelength of around 13.5 nm has been developed. To achieve such fine pattern transfer, high flatness is required for the mask blank substrate. If the flatness of the reflective mask blank deteriorates, when transferring the transfer pattern of the reflective mask made from the reflective mask blank onto the wafer, the imaging position of the pattern shifts from the wafer surface, degrading the pattern transfer accuracy. This results in a discrepancy in the dimensions of the circuit pattern formed on the wafer, and a problem arises in obtaining a semiconductor device that does not have the expected performance. Furthermore, if the flatness of the reflective mask blank deteriorates, when transferring the transfer pattern of the reflective mask onto the wafer, the position where the pattern is formed shifts from the desired position, resulting in a problem in obtaining a semiconductor device that does not have the expected characteristics such as transistor switching speed and leakage current. The amount of deviation of the pattern formation position from the desired position is called the overlay accuracy (superposition accuracy), and as the circuit dimensions of the semiconductor device decrease, smaller overlay accuracy is required.

[0009] However, it has been found that even with substrates that meet conventional requirements such as flatness, the desired overlay accuracy may not be obtained in reflective masks fabricated from these substrates.

[0010] Therefore, the present invention aims to provide a mask blank substrate, a multilayer reflective film substrate, and a mask blank that can produce a transfer mask that can satisfy a desired overlay accuracy.

[0011] The present invention also aims to provide a method for manufacturing a transfer mask manufactured using the above mask blank, and a method for manufacturing a semiconductor device using the transfer mask manufactured by the method for manufacturing the transfer mask. Means for Solving the Problems

[0012] The present invention has been made to solve the above problems and has the following configuration. (Configuration 1) A mask blank substrate having two opposing main surfaces, In the inner region of a square with a side of 132 mm based on the center of the substrate, a composite surface shape is generated from the surface shapes of the two main surfaces of the substrate, and from the composite surface shape, the spatial frequency fr [mm -1 and the power spectral density Pr [μm 2 / (mm -1 )] When the relationship is calculated, 0.02 [mm -1 or more and 0.40 [mm -1 or less, among the range of the spatial frequency fr, at least 75% or more of the spatial frequency fr, Pr <(1.5141 × 10 -6 ) × (fr -1.3717 ) satisfies the relationship A mask blank substrate characterized by the above.

[0013] (Configuration 2) The composite surface shape is obtained by adding the surface shape of one of the main surfaces, which is the in-plane distribution of the height from the reference plane serving as the reference for the surface shape of one of the main surfaces to one of the main surfaces, and the surface shape of the other main surface, which is the in-plane distribution of the height from the reference plane serving as the reference for the surface shape of the other main surface to the other main surface. The mask blank substrate according to Configuration 1, characterized by the above.

[0014] (Configuration 3) The power spectral density Pr is 1.0 × 10 -2 [mm -1A mask blank substrate according to configuration 1 or 2, characterized in that it is calculated for each interval of the spatial frequency fr as follows.

[0015] (Composition 4) A multilayer reflective substrate characterized in that a multilayer reflective film is provided on one of the main surfaces of the mask blank substrate described in any of configurations 1 to 3.

[0016] (Composition 5) A multilayer reflective substrate having two opposing main surfaces, wherein one of the main surfaces is provided with a multilayer reflective film, and the other main surface is provided with a conductive film, Within the inner region of a rectangle with sides of 132 mm, with respect to the center of the substrate, a composite surface shape is generated from the surface shape of the multilayer reflective film and the surface shape of the conductive film, and the spatial frequency fr[mm] is obtained from this composite surface shape. -1 ] and power spectral density Pr[μm 2 / (mm -1 When calculating the relationship between ), 0.02 [mm] -1 ] or more 0.40[mm -1 Within the spatial frequency range fr below, at least 75% of the spatial frequency fr, Pr < (1.5141 × 10 -6 )×(fr -1.3717 The relationship satisfies A multilayer reflective film substrate characterized by the following features.

[0017] (Composition 6) The substrate with a multilayer reflective film according to configuration 5, characterized in that the composite surface shape is obtained by adding the surface shape of the multilayer reflective film, which is the in-plane distribution of height from a reference plane that serves as a reference for the surface shape of the multilayer reflective film to the surface of the multilayer reflective film, and the surface shape of the conductive film, which is the in-plane distribution of height from a reference plane that serves as a reference for the surface shape of the conductive film to the surface of the conductive film.

[0018] (Composition 7) The power spectral density Pr is 1.0 × 10⁻⁶ -2 [mm -1The multilayer reflective substrate according to configuration 5 or 6, characterized in that it is calculated for each interval of the spatial frequency fr as follows.

[0019] (Composition 8) A mask blank characterized in that a thin film for pattern formation is provided on the multilayer reflective film of a substrate with a multilayer reflective film as described in any of configurations 5 to 7.

[0020] (Composition 9) A mask blank comprising a pattern-forming thin film on one of the main surfaces of a substrate having two opposing main surfaces, and a conductive film on the other main surface, Within the inner region of a rectangle with sides of 132 mm, with respect to the center of the substrate, a composite surface shape is generated from the surface shape of the pattern-forming thin film and the surface shape of the conductive film, and the spatial frequency fr[mm] is obtained from the composite surface shape. -1 ] and power spectral density Pr[μm 2 / (mm -1 When calculating the relationship between ), 0.02 [mm] -1 ] or more 0.40[mm -1 Within the spatial frequency range fr below, at least 75% of the spatial frequency fr, Pr < (1.5141 × 10 -6 )×(fr -1.3717 The relationship satisfies A mask blank characterized by the following features.

[0021] (Composition 10) The mask blank according to configuration 9, characterized in that the composite surface shape is obtained by adding the surface shape of the pattern-forming thin film, which is the in-plane distribution of height from a reference plane that serves as the basis for the surface shape of the pattern-forming thin film to the surface of the pattern-forming thin film, and the surface shape of the conductive film, which is the in-plane distribution of height from a reference plane that serves as the basis for the surface shape of the conductive film to the surface of the conductive film.

[0022] (Composition 11) The power spectral density Pr is 1.0 × 10⁻⁶ -2 [mm-1 The mask blank according to configuration 9 or 10, characterized in that it is calculated for each interval of the spatial frequency fr as follows.

[0023] (Composition 12) A mask blank according to any one of configurations 9 to 11, characterized in that it has a multilayer reflective film between one of the main surfaces and the thin film for pattern formation.

[0024] (Composition 13) A method for manufacturing a transfer mask, characterized by comprising the step of forming a transfer pattern on the pattern-forming thin film of the mask blank described in any of configurations 9 to 12.

[0025] (Composition 14) A method for manufacturing a semiconductor device, characterized by setting a transfer mask manufactured by the method for manufacturing a transfer mask described in configuration 13 on the mask stage of an exposure apparatus, and transferring the transfer pattern of the transfer mask onto a semiconductor substrate by lithography. [Effects of the Invention]

[0026] This invention provides a mask blank substrate, a multilayer reflective film substrate, and a mask blank that can satisfy the desired overlay accuracy required for the fabricated mask. Furthermore, it provides a method for manufacturing a transfer mask using the above-mentioned mask blank, and a method for manufacturing a semiconductor device using the transfer mask manufactured by the method for manufacturing the transfer mask. [Brief explanation of the drawing]

[0027] [Figure 1] This is a cross-sectional view of a mask blank substrate, a multilayer reflective film substrate, and a mask blank according to an embodiment of the present invention. [Figure 2]This graph shows the average power spectral density of the OK substrate against spatial frequency, the average power spectral density of the NG substrate, and an approximation curve (threshold curve) calculated from the average power spectral density of the NG substrate. [Figure 3] This graph shows the power spectral density curve and threshold curve for the mask blank substrate of Example 1 against spatial frequency. [Figure 4] This graph shows the power spectral density curve and threshold curve for the mask blank substrate of Example 2 against spatial frequency. [Figure 5] This graph shows the power spectral density curve and threshold curve for the mask blank substrate of Example 3 against spatial frequency. [Figure 6] This graph shows the power spectral density curve and threshold curve for the mask blank substrate of Comparative Example 1 against spatial frequency. [Figure 7] This graph shows the power spectral density curve and threshold curve for the mask blank substrate of Comparative Example 2 against spatial frequency. [Figure 8] This graph shows the power spectral density curve and threshold curve for the mask blank substrate of Comparative Example 3 against spatial frequency. [Modes for carrying out the invention]

[0028] The embodiments of the present invention will be described below, but first, the background to the present invention will be explained. First, the inventors collected a predetermined number (approximately 100 of each) of mask blank substrates that met the desired flatness, met the desired overlay accuracy (hereinafter referred to as "OK substrates" as appropriate), and did not meet the desired accuracy (hereinafter referred to as "NG substrates" as appropriate), and diligently examined each. First, the inventors focused on the composite surface shape obtained from the surface shapes of the two main surfaces of the mask blank substrate in the inner region of a rectangle with sides of 132 mm based on the center of the substrate (the region where the transfer pattern is formed). This is because when a transfer mask manufactured using a mask blank substrate is set (chucked) in an exposure apparatus, the main surface on the chucked side becomes substantially flat, and the surface shape of the chucked main surface is added to the surface shape of the exposed main surface.

[0029] Next, the inventors calculated the spatial frequency fr[mm²] for the composite surface shapes of the OK substrate and the NG substrate described above, within a wide area that is the inner region of a rectangle with sides of 132 mm, with the center of the substrate as the reference point. -1 ] and power spectral density Pr[μm 2 / (mm -1 We focused on the relationship between ( ) and ( ). This makes it possible to calculate shape components with larger periods (smaller spatial frequencies) that could not be calculated conventionally.

[0030] Then, for each OK board and each NG board, the power spectral density against spatial frequency was calculated in the inner region of a rectangle with sides of 132 mm, based on the center of the board, and the average value for each OK board and each NG board was calculated, which was 0.02 [mm²]. -1 ] or more 0.40[mm -1 In the spatial frequency range fr below, the power spectral density Pr[μm] differs between the OK substrate and the NG substrate. 2 / (mm -1 A significant difference was found in ).

[0031] Therefore, we conducted a more detailed examination of these ranges. First, we calculated the average power spectral density of all OK substrates that met the desired overlay accuracy for each spatial frequency, and obtained the trend of the relationship between the spatial frequency and power spectral density of the OK substrates. Next, we calculated the average power spectral density of all NG substrates that did not meet the desired overlay accuracy for each spatial frequency, and obtained the trend of the relationship between the spatial frequency and power spectral density of the NG substrates. Furthermore, we calculated an approximate curve (threshold curve) from the relationship between the spatial frequency and power spectral density of the NG substrates. These results are shown in Figure 2. As shown in the figure, 0.02 [mm -1 ] or more 0.40[mm -1 In the spatial frequency range fr below, the average value Pr[μm] of the power spectral density of the OK substrate 2 / (mm -1 )] is the average value of the power spectral density of the NG substrate Pr[μm 2 / (mm -1 It can be seen that this is significantly lower than ). Furthermore, as shown in Figure 2, the inventors have found that the spatial frequency and power spectral density Pr[μm] of the NG substrate are significantly lower. 2 / (mm -1 For the relationship between ( ), we calculate the approximate curve using power approximation and obtain the threshold curve (Pr=(1.5141×10) -6 )×(fr -1.3717 )) was set to 0.02[mm -1 ] or more 0.40[mm -1 In the spatial frequency range fr below, the power spectral density Pr[μm] of this threshold curve is 2 / (mm -1 ) and the power spectral density Pr[μm] in the OK substrate. 2 / (mm -1 We examined the relationship between the two () and their relative magnitudes.

[0032] As a result, in all OK substrates, 0.02 [mm -1 ] or more 0.40[mm -1 In the spatial frequency range fr below ], at spatial frequencies fr of 75% or higher, Pr < (1.5141 × 10 -6 )×(fr -1.3717We found that the relationship ) is satisfied. Furthermore, if the above relationship is satisfied, the composite surface shape of the substrate is 0.02 [mm -1 Even if the power spectral density is high in the low spatial frequency (long wavelength) region below ], it is not a problem. This is because even if a transfer mask manufactured from such a substrate is set in an exposure apparatus and exposure transfer is performed, the exposure transfer image can be easily corrected by the correction function of the exposure apparatus.

[0033] This invention was made as a result of the diligent considerations described above. The best mode for carrying out the present invention will be described in detail below, including its concept, with reference to the drawings.

[0034] [Substrate for mask blanks and method for manufacturing the same] This section describes a mask blank substrate and a method for manufacturing the same. In this embodiment, a mask blank substrate for use in EUV lithography is described, but the mask blank substrate of the present invention is not limited to this and can also be applied to mask blank substrates for use in, for example, transmissive photolithography.

[0035] Figure 1 shows a mask blank substrate 1 in an embodiment of the present invention. As shown in the figure, the substrate 1 preferably has a low thermal expansion coefficient in the range of 0 ± 5 ppb / °C in order to prevent distortion of the transfer pattern (not shown) due to heat during exposure with EUV light. Examples of materials having a low thermal expansion coefficient in this range include SiO2-TiO2 glass and multi-component glass ceramics.

[0036] The substrate 1 has two opposing main surfaces 2 and 3. The main surface 2 on the side of the substrate 1 where the transfer pattern is formed is surface-processed to have high flatness, at least from the viewpoint of obtaining pattern transfer accuracy and positional accuracy. In the case of EUV exposure, the flatness of the main surface 2 on the side of the substrate 1 where the transfer pattern is formed 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 area. The main surface 3 on the opposite side from where the transfer pattern is formed is the surface that is electrostatically chucked when set in the exposure apparatus, and the flatness of the main surface 3 on the opposite side 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 area. Furthermore, the flatness of the main surface 3 side of the reflective mask blank 20 is preferably 1 μm or less in a 142 mm × 142 mm area, more preferably 0.5 μm or less, and particularly preferably 0.3 μm or less.

[0037] In this embodiment, the substrate 1 generates a composite surface shape from the surface shapes of the two main surfaces 2 and 3 of the substrate 1 within the inner region of a rectangle with sides of 132 mm, with the center of the substrate 1 as the reference point, and the spatial frequency fr[mm] is obtained from this composite surface shape. -1 ] and power spectral density Pr[μm 2 / (mm -1 When calculating the relationship between ), 0.02[mm -1 ] or more 0.40[mm -1 Within the spatial frequency range fr below, at least 75% of the spatial frequency fr, Pr < (1.5141 × 10 -6 )×(fr -1.3717 It is characterized by satisfying the relationship of ) Here, the composite surface shape is obtained by adding together the surface shape of one main surface 2, which is the in-plane distribution of height from the reference plane that serves as the basis for the surface shape of one main surface 2 to the other main surface 2, and the surface shape of the other main surface 3, which is the in-plane distribution of height from the reference plane that serves as the basis for the surface shape of the other main surface 3 to the other main surface 3.

[0038] The surface shapes of main surfaces 2 and 3 are acquired by a surface shape measuring device. The surface shape measuring device places measurement points in a grid pattern on the surface to be measured and acquires the surface shape in the form of height information for each measurement point. The reference plane is a plane approximated by the least squares method based on the height information of each measurement point (least squares plane). There are cases where the reference plane of main surface 2 and the reference plane of main surface 3 are not parallel. In that case, the resulting composite surface shape will contain an error due to the tilt component. However, this error is 0.02 [mm -1 ] or more 0.40[mm -1 The effect on the power spectral density Pr value at spatial frequencies fr below this level is virtually negligible.

[0039] Specifically, the power spectral density Pr is calculated using the following formula.

[0040]

number

[0041] The power spectral density Pr is 1.0 × 10⁻⁶. -2 [mm -1 It is preferable that the spatial frequency interval fr is calculated to be within the following range. By using the power spectral density Pr calculated with spatial frequency intervals fr within this range, a substrate that satisfies the desired overlay accuracy can be reliably obtained. Furthermore, the spatial frequency interval fr is 5.0 × 10 -3 [mm -1 It is more preferable that the following conditions apply. The difference between the highest and lowest heights (PV value) in the inner region of a rectangle with sides of 132 mm, based on the center of the substrate 1, is preferably 0.05 μm or less, more preferably 0.04 μm or less, and even more preferably 0.03 μm or less.

[0042] Furthermore, the surface smoothness of the substrate 1 is also an important factor. The surface roughness of the main surfaces 2 and 3 of the substrate 1 on which the transfer pattern is formed is preferably 0.2 nm or less, more preferably 0.15 nm or less, and even more preferably 0.1 nm or less in terms of root mean square roughness (RMS). Surface smoothness can be measured using an atomic force microscope.

[0043] Furthermore, it is preferable that the substrate 1 has high rigidity in order to suppress deformation due to film stress of the film (such as the multilayer reflective film 4) formed thereon. In particular, it is preferable that the substrate 1 has a high Young's modulus of 65 GPa or more.

[0044] Next, the manufacturing method of this substrate 1 will be described. Note that this manufacturing method is just one example and is not the only method that can be used. First, the substrate material is cut to the desired size (for example, 152.4 mm x 152.4 mm, 6.35 mm thick). Then, if necessary, the edges of this synthetic quartz glass substrate are chamfered and ground, and then rough polishing and fine polishing are performed with a polishing solution containing cerium oxide abrasive particles. After that, the surface shape of the main surface of the substrate 1 is obtained, and a local processing step is performed on the relatively convex areas on the main surface for each of the two main surfaces. After that, the substrate is set on the carrier of a double-sided polishing device and ultra-precision polishing is performed under predetermined conditions. After the ultra-precision polishing is completed, the glass substrate is immersed in a dilute hydrofluoric acid solution to remove colloidal silica abrasive particles. After that, the main surface and edges of the glass substrate are scrubbed, followed by spin washing with pure water and spin drying to obtain a substrate 1 with a polished surface.

[0045] [Multilayer reflective film coated substrate and method for manufacturing the same] Figure 1 also shows a multilayer reflective substrate 10 according to an embodiment of the present invention. As shown in the figure, the multilayer reflective substrate 10 has a multilayer reflective film 4 provided on one of the main surfaces 2 of a mask blank substrate 1.

[0046] Furthermore, in this embodiment, the multilayer reflective substrate 10 has a conductive film 5 provided on the other main surface 2 of the mask blank substrate 1. In this embodiment, the multilayer reflective substrate 10 generates a composite surface shape from the surface shape of the multilayer reflective film 4 and the surface shape of the conductive film 5 in the inner region of a rectangle with sides of 132 mm based on the center of the substrate 1, and the spatial frequency fr[mm] is calculated from this composite surface shape. -1 ] and power spectral density Pr[μm 2 / (mm -1 When calculating the relationship between ), 0.02[mm -1 ] or more 0.40[mm -1 Within the spatial frequency range fr below, at least 75% of the spatial frequency fr, Pr < (1.5141 × 10 -6 )×(fr -1.3717 It is characterized by satisfying the relationship of ) Here, the composite surface shape is obtained by adding together the surface shape of the multilayer reflective film 4, which is the in-plane distribution of the height from the reference plane serving as the reference for the surface shape of the multilayer reflective film 4 to the surface of the multilayer reflective film 4, and the surface shape of the conductive film 5, which is the in-plane distribution of the height from the reference plane serving as the reference for the surface shape of the conductive film 5 to the surface of the conductive film 5.

[0047] The reference plane of the multilayer reflective film 4 (or the conductive film 5) is a plane (least-squares plane) approximated by the least-squares method based on the height information of each measurement point of the multilayer reflective film 4 (or the conductive film 5) measured by a surface shape measuring device. The power spectral density Pr is preferably calculated at intervals of the spatial frequency fr of 1.0×10 -2 [mm -1 or less. Also, the interval of the spatial frequency fr is more preferably 5.0×10 -3 [mm -1 or less.

[0048] As described above, in the substrate 10 with a multilayer reflective film, the same method as that for the mask blank substrate 1 can be used. This is due to the following reasons. When thin films (multilayer reflective film 4, conductive film 5, protective film 6) are formed evenly on the substrate 1, deformation due to film stress from each thin film occurs in the substrate 1. However, the distribution of the film stress acts such that these thin films contract or expand the substrate 1 substantially evenly. That is, the composite surface shape of the substrate 10 with a multilayer reflective film becomes a shape in which a component of a quadratic surface is further added to the composite surface shape of the mask blank substrate 1. However, when the main surface 3 (or the conductive film 5) of the substrate 10 with a multilayer reflective film is chucked by the exposure apparatus, the substrate 10 with a multilayer reflective film is deformed in a direction in which the component of the quadratic surface of this composite surface shape is canceled out. For this reason, it is not necessary to consider the film stress of the thin films formed on the substrate 1. On the other hand, the spatial frequency of the power spectral density corresponding to the component of the quadratic surface generated by the stress of the thin film is much lower than 0.02 [mm -1 . Therefore, the same method as for the mask blank substrate 1 can be used for the multilayer reflective film substrate 10. Here, the power spectral density Pr can also be calculated using the above formula when the measurement points of the composite surface shape of the multilayer reflective film 4 (or protective film 6 if a protective film 6 is formed) and the conductive film 5 on the multilayer reflective film substrate 10 are defined in an xy coordinate system.

[0049] The multilayer reflective film 4 provides the function of reflecting EUV light in a reflective mask (not shown), and is a multilayer film in which layers mainly composed of elements with different refractive indices are periodically stacked. Generally, a multilayer film is used as the multilayer reflective film 4, in which thin films of light elements or compounds that are high refractive index materials (high refractive index layer) and thin films of heavy elements or compounds that are low refractive index materials (low refractive index layer) are alternately stacked for about 40 to 60 periods. The multilayer film may be stacked in multiple periods, with one period being a stacked structure of high refractive index layer / low refractive index layer, where the high refractive index layer and the low refractive index layer are stacked in this order from the main surface 2 side of the substrate 1. Alternatively, the multilayer film may be stacked in multiple periods, with one period being a stacked structure of low refractive index layer / high refractive index layer, where the low refractive index layer and the high refractive index layer are stacked in this order from the main surface 2 side of the substrate 1. It is preferable that the outermost layer of the multilayer reflective film 4, i.e., the surface layer of the multilayer reflective film 4 opposite to the substrate 1, be a high refractive index layer. In the above-described multilayer film, when multiple periods are stacked with one period being a stacked structure of high refractive index layer / low refractive index layer, where the high refractive index layer and the low refractive index layer are stacked in this order from the substrate 1, the uppermost layer is a low refractive index layer. In this case, if the low refractive index layer constitutes the outermost surface of the multilayer reflective film 4, it will be easily oxidized, reducing the reflectivity of the reflective mask. Therefore, it is preferable to further form a high refractive index layer on the uppermost low refractive index layer to form the multilayer reflective film 4. On the other hand, in the above-described multilayer film, if a low refractive index layer and a high refractive index layer are stacked in this order from the substrate 1 side, and multiple periods of stacking are performed with this low refractive index layer / high refractive index layer stacking structure as one period, the uppermost layer will be the high refractive index layer, so it is fine as is.

[0050] In this embodiment, a layer containing silicon (Si) is used as the high refractive index layer. As the Si-containing material, in addition to elemental Si, Si compounds containing boron (B), carbon (C), nitrogen (N), and oxygen (O) can be used. By using a Si-containing layer as the high refractive index layer, a reflective mask for EUV lithography with excellent EUV light reflectivity can be obtained. Furthermore, in this embodiment, a glass substrate is preferably used as the substrate 1. Si also exhibits excellent adhesion to the glass substrate. As the low refractive index layer, elemental metals selected from molybdenum (Mo), ruthenium (Ru), rhodium (Rh), and platinum (Pt), or alloys thereof, can be used. For example, as the multilayer reflective film 4 for EUV light with wavelengths of 13 nm to 14 nm, a Mo / Si periodic multilayer film is preferably used, in which Mo films and Si films are alternately stacked for approximately 40 to 60 periods. The high refractive index layer, which is the uppermost layer of the multilayer reflective film 4, may also be formed of silicon (Si).

[0051] The reflectivity of the multilayer reflective film 4 alone is typically 65% ​​or higher, with an upper limit of typically 73%. The film thickness and period of each constituent layer of the multilayer reflective film 4 can be appropriately selected according to the exposure wavelength, and are chosen to satisfy Bragg's law of reflection. While multiple high-refractive-index layers and low-refractive-index layers exist in the multilayer reflective film 4, the film thicknesses of the high-refractive-index layers and the low-refractive-index layers do not necessarily have to be the same. Furthermore, the film thickness of the outermost Si layer of the multilayer reflective film 4 can be adjusted within a range that does not reduce reflectivity. The film thickness of the outermost Si layer (high-refractive-index layer) can be in the range of 3 nm to 10 nm.

[0052] The method for forming the multilayer reflective film 4 is known in the art. For example, it can be formed by depositing each layer of the multilayer reflective film 4 using an ion beam sputtering method. In the case of the Mo / Si periodic multilayer film described above, for example, an Si film with a thickness of about 4 nm is first deposited on the substrate 1 using a Si target by an ion beam sputtering method. Then, an Mo film with a thickness of about 3 nm is deposited using a Mo target. This Si film / Mo film is considered as one period, and 40 to 60 periods are stacked to form the multilayer reflective film 4 (the outermost layer is the Si layer). For example, if the multilayer reflective film 4 has 60 periods, the number of steps increases compared to 40 periods, but the reflectivity to EUV light can be increased. Furthermore, it is preferable to form the multilayer reflective film 4 by supplying krypton (Kr) ion particles from an ion source and performing ion beam sputtering during the deposition of the multilayer reflective film 4.

[0053] The conductive film 5 generally possesses the electrical properties (sheet resistance) required for electrostatic chucks, which are typically 100 Ω / □ (Ω / Square) or less. The conductive film 5 can be formed, for example, by magnetron sputtering or ion beam sputtering, using metal and alloy targets such as chromium (Cr) and tantalum (Ta).

[0054] The thickness of the conductive film 5 is not particularly limited as long as it satisfies its function as an electrostatic chuck. The thickness of the conductive film 5 is usually between 10 nm and 200 nm. In addition, this conductive film 5 also serves to adjust the stress on the main surface 3 side of the mask blank 20. That is, the conductive film 5 is adjusted to balance the stress from the various films formed on the main surface 2 side so that a flat reflective mask blank 20 can be obtained.

[0055] Furthermore, the substrate 10 with the multilayer reflective film may also be provided with a protective film 6 on top of the multilayer reflective film 4. To protect the multilayer reflective film 4 from dry etching and cleaning in the manufacturing process of the reflective mask described later, the protective film 6 can be formed on top of the multilayer reflective film 4 or in contact with the surface of the multilayer reflective film 4. The protective film 6 is made of a material that is resistant to the etchant used when patterning the absorber film 11 and to cleaning solutions. By forming the protective film 6 on top of the multilayer reflective film 4, damage to the surface of the multilayer reflective film 4 can be suppressed when manufacturing a reflective mask (EUV mask) using the substrate 1 having the multilayer reflective film 4 and the protective film 6. As a result, the reflectivity characteristics of the multilayer reflective film 4 with respect to EUV light are improved. The protective film 6 is preferably formed from, for example, elemental Ru, or from a material containing Ru with at least one element selected from titanium (Ti), niobium (Nb), molybdenum (Mo), zirconium (Zr), yttrium (Y), boron (B), lanthanum (La), cobalt (Co), rhenium (Re), and rhodium (Ph). Alternatively, the protective film 6 can also be formed from silicon-based materials such as silicon (Si), materials containing silicon (Si) and oxygen (O), materials containing silicon (Si) and nitrogen (N), or materials containing silicon (Si), oxygen (O), and nitrogen (N).

[0056] [Mask blank and method for manufacturing the same] Figure 1 also shows a mask blank 20 in an embodiment of the present invention. As shown in the figure, the mask blank 20 has a pattern-forming thin film (absorber film 11) provided on the multilayer reflective film 4 (or on the protective film 6 if a protective film 6 is provided) of the multilayer reflective film substrate 10.

[0057] In addition, the mask blank 20 in the present embodiment includes a pattern-forming thin film (absorber film 11) on one main surface 2 of the mask blank substrate 1, and a conductive film 5 is provided on the other main surface 3. And the mask blank 20 in the present embodiment generates a composite surface shape from the surface shape of the absorber film 11 which is a pattern-forming thin film and the surface shape of the conductive film 5 in the inner region of a square with one side of 132 mm based on the center of the substrate 1, and from the composite surface shape, the spatial frequency fr [mm -1 and the power spectral density Pr [μm 2 / (mm -1 )] relationship is calculated, 0.02 [mm -1 or more and 0.40 [mm -1 or less, among the range of the spatial frequency fr, at least 75% or more of the spatial frequency fr satisfies the relationship of Pr <(1.5141×10 -6 )×(fr -1.3717 ). Here, the composite surface shape is obtained by adding the surface shape of the absorber film 11 which is the in-plane distribution of the height from the reference plane serving as the reference for the surface shape of the absorber film 11 to the surface of the absorber film 11, and the surface shape of the conductive film 5 which is the in-plane distribution of the height from the reference plane serving as the reference for the surface shape of the conductive film 5 to the surface of the conductive film 5.

[0058] The reference plane of the absorber film 11 (or the conductive film 5) is a plane (least-squares plane) approximated by the least-squares method based on the height information of each measurement point of the absorber film 11 (or the conductive film 5) measured by a surface shape measuring device. The power spectral density Pr is preferably calculated at intervals of the spatial frequency fr of 1.00×10 -2 [mm -1 or less. Also, the interval of the spatial frequency fr is more preferably 5.0×10 -3 [mm -1 or less.

[0059] As described above with respect to the multilayer reflective film substrate 10, the same method as for the mask blank substrate 1 can be used for the mask blank 20. Here, the power spectral density Pr can also be calculated using the above formula when the measurement points of the combined surface shape of the absorber film 11 and conductive film 5 in the mask blank 20 are defined in an xy coordinate system.

[0060] The absorber film 11 has the function of absorbing EUV light, which is the exposure light, and in a reflective mask made using the mask blank 20, it is sufficient that there is a desired reflectance difference between the light reflected by the multilayer reflective film 4 and protective film 6 and the light reflected by the absorber pattern. For example, the absolute reflectance of the absorber film 11 with respect to EUV light is set to be between 0.1% and 40%. In addition to the above reflectance difference, there may also be a desired phase difference between the reflected light from the multilayer reflective film 4 and protective film 6 and the reflected light from the absorber pattern. When a desired phase difference is provided between the reflected light to improve the contrast of the reflected light of the resulting reflective mask, it is preferable to set the phase difference in the range of 130 degrees to 230 degrees, the absolute reflectance of the absorber film 11 to be between 1.5% and 30%, and the relative reflectance of the absorber film 11 (reflectance when the reflectance of the multilayer reflective film 4 with respect to EUV light is set to 100%) to be between 2% and 40%.

[0061] The absorber film 11 described above may be a single layer or a laminated structure. In the case of a laminated structure, it may be a laminated film of the same material or a laminated film of different materials. The laminated film may have materials and composition that change stepwise and / or continuously in the direction of film thickness. The material of the absorber film 11 is not particularly limited, but it is preferable that it contains a metallic element. For example, a material that has the function of absorbing EUV light may be used, such as pure tantalum (Ta) or a material mainly composed of Ta.

[0062] The absorber membrane 11 may be made of a material containing tantalum (Ta) and at least one element selected from tellurium (Te), antimony (Sb), platinum (Pt), iodine (I), bismuth (Bi), iridium (Ir), osmium (Os), tungsten (W), rhenium (Re), tin (Sn), indium (In), polonium (Po), iron (Fe), gold (Au), mercury (Hg), gallium (Ga), and aluminum (Al). The absorber membrane 11 may also be formed from a material containing tantalum (Ta) and iridium (Ir). Alternatively, the absorber membrane 11 may be formed from a material containing ruthenium (Ru) and chromium (Cr). The absorber membrane 11 may be formed from a material containing ruthenium (Ru) and chromium (Cr) along with at least one element selected from nitrogen (N), oxygen (O), boron (B), and carbon (C).

[0063] Furthermore, an etching mask film may be provided on the absorber film 11 as a pattern-forming thin film. In this case, the mask blank 20 has a pattern-forming thin film (absorber film 11 and etching mask film) on one main surface 2 of the mask blank substrate 1, and a conductive film 5 on the other main surface 3. In this case, the mask blank 20 generates a composite surface shape from the surface shape of the etching mask film, which is the pattern-forming thin film, and the surface shape of the conductive film 5 in the inner region of a rectangle with sides of 132 mm with respect to the center of the substrate 1, and the spatial frequency fr[mm] is obtained from this composite surface shape. -1 ] and power spectral density Pr[μm 2 / (mm -1 When calculating the relationship between ), 0.02 [mm] -1 ] or more 0.40[mm -1 Within the spatial frequency range fr below, at least 75% of the spatial frequency fr, Pr < (1.5141 × 10 -6 )×(fr -1.3717 It is characterized by satisfying the relationship of )

[0064] Here, the composite surface shape is obtained by adding the surface shape of the etching mask film, which is the in-plane distribution of height from a reference plane that serves as the basis for the surface shape of the etching mask film to the surface of the etching mask film, and the surface shape of the conductive film 5, which is the in-plane distribution of height from a reference plane that serves as the basis for the surface shape of the conductive film 5 to the surface of the conductive film 5. The reference plane of the etching mask film (or conductive film 5) is a plane (least squares plane) approximated by the least squares method based on the height information of each measurement point of the etching mask film (or conductive film 5) measured by the surface shape measuring device. The power spectral density Pr is 1.00 × 10⁻⁶ -2 [mm -1 It is preferable that the spatial frequency interval fr is calculated to be 5.0 × 10. -3 [mm -1 It is more preferable that the following conditions apply.

[0065] As described above with respect to the multilayer reflective film substrate 10, the same method as for the mask blank substrate 1 can be used for the mask blank 20. Here, the power spectral density Pr can also be calculated using the above formula when the measurement points of the composite surface shape of the etching mask film and conductive film 5 on the mask blank 20 are defined in an xy coordinate system.

[0066] While the material for the etching mask film is not particularly limited, it is preferable to use a material that has a high etching selectivity ratio of the absorber film 11 to the etching mask film (etching rate of the absorber film 11 / etching rate of the etching mask film). The etching mask film may be formed from a material containing at least one element selected from chromium (Cr), tantalum (Ta), and silicon (Si). Alternatively, it may be a material to which at least one element selected from N, O, C, and H has been added.

[0067] The method for manufacturing the mask blank 20 of the present invention includes a step of providing a pattern-forming thin film (an absorber film 11, or, if an etching mask film is present, the absorber film 11 and the etching mask film) on the protective film 6 of the multilayer reflective film substrate 10 described above. In the method for manufacturing the mask blank 20 of the present invention, in the step of forming the absorber film 11, the absorber film 11 is preferably formed by a reactive sputtering method using a sputtering target made of the material contained in the absorber film 11, and is formed so as to contain components contained in the atmospheric gas during reactive sputtering. Furthermore, when manufacturing a mask blank 20 having an etching mask film, in addition to the step of forming the absorber film 11 described above, it is preferable that in the step of forming the etching mask film, the etching mask film is formed by a reactive sputtering method using a sputtering target made of the material contained in the etching mask film, and that it is formed so as to contain components contained in the atmospheric gas during reactive sputtering.

[0068] Thus, the mask blank substrate 1, the multilayer reflective film substrate 10, and the mask blank 20 in the embodiment of the present invention can be used to produce a transfer mask that can satisfy the desired overlay accuracy.

[0069] [Method for manufacturing transfer masks] The present invention provides a method for manufacturing a transfer mask, comprising the step of patterning the absorber film (pattern-forming thin film) 11 in the mask blank 20 to form an absorber film (absorber pattern) having a transfer pattern on the multilayer reflective film 4 or the protective film 6. Furthermore, if an etching mask film is included, the absorber film 11 is patterned after the etching mask film is patterned to form an absorber film (absorber pattern) having a transfer pattern on the multilayer reflective film 4 or the protective film 6. The transfer mask manufactured in this manner according to this embodiment can be used as a lithography transfer mask when exposed to exposure light such as EUV light. In the areas of the transfer mask surface where the absorber film 11 is present, the exposure light is absorbed, while in the areas where the absorber film 11 has been removed, the exposure light is reflected by the exposed protective film 6 and multilayer reflective film 4, thus enabling its use as a lithography transfer mask. According to the reflective mask of the present invention, by having an absorber pattern on the multilayer reflective film 4 (or protective film 6), a predetermined pattern can be transferred to the object to be transferred using EUV light.

[0070] [Manufacturing method for semiconductor devices] By setting the transfer mask manufactured using the method described above onto the mask stage of an exposure apparatus and transferring the transfer pattern of the transfer mask onto a semiconductor substrate using lithography, it is possible to manufacture a semiconductor device on which various transfer patterns are formed on a substrate or other transfer target. In other words, the present invention is a method for manufacturing a semiconductor device, comprising the step of forming a transfer pattern on a transfer object by performing a lithography process using an exposure apparatus with the above-described transfer mask. According to the semiconductor device manufacturing method of the present invention, exposure transfer can be performed using a transfer mask that satisfies the desired overlay accuracy, and positional displacement of the transfer mask during pattern transfer can be suppressed, making it possible to manufacture semiconductor devices having fine and highly accurate transfer patterns.

[0071] The following describes the mask blank substrate 1, multilayer reflective film substrate 10, mask blank 20, and reflective mask in Examples 1 to 3 of the present invention, as well as the mask blank substrate, multilayer reflective film substrate, mask blank, and reflective mask in Comparative Examples 1 to 3.

[0072] <Manufacturing of substrates for mask blanks> The mask blank substrate 1 in Examples 1 to 3, and the mask blank substrate in Comparative Examples 1 to 3, were manufactured as follows.

[0073] First, a SiO2-TiO2 glass substrate measuring 152mm x 152mm and 6.35mm thick was prepared. Using a double-sided polishing device, the front and back surfaces of the glass substrate were polished in stages with cerium oxide abrasive grains and colloidal silica abrasive grains, and then the surface was treated with low-concentration hydrofluoric acid. Within a 148mm x 148mm measurement area on both the front and back surfaces of the glass substrate, 256 x 256 measurement points were set in a grid pattern. Surface shape (surface form, flatness) and TTV (thickness variation) were measured using a wavelength-shift interferometer with a wavelength-modulated laser. The measurement results for the surface shape (flatness) of the glass substrate surface were stored in a computer as height information relative to a reference plane for each measurement point. This information was then compared with the required reference values ​​of 50nm for surface flatness (convex shape) and 50nm for back surface flatness, and the difference (required removal amount) was calculated by computer.

[0074] Next, processing conditions for local surface processing were set for each processing spot shape region within the glass substrate surface, according to the required removal amount. Using a dummy substrate, the dummy substrate was processed in the same way as the actual processing, without moving the substrate for a certain period of time. The shape was measured using the same measuring instrument as the one used to measure the surface shapes of the front and back surfaces, and the processing volume of the spot per unit time was calculated. Then, the scanning speed when raster scanning the glass substrate was determined according to the required removal amount obtained from the spot information and the surface shape information of the glass substrate. According to the set processing conditions, the surface shape of the glass substrate was adjusted by local surface processing using a magneto-viscoelastic fluid substrate finishing apparatus and magneto-viscoelastic fluid polishing (MRF) method so that the flatness of the front and back surfaces of the glass substrate was below the above-mentioned standard value. The magneto-viscoelastic fluid used at this time contained iron components, and the polishing slurry was an alkaline aqueous solution containing approximately 2 wt% cerium oxide as an abrasive. After that, the glass substrate was immersed in a washing tank containing an aqueous hydrochloric acid solution of approximately 10% concentration (at a temperature of approximately 25°C) for about 10 minutes, followed by rinsing with pure water and drying with isopropyl alcohol (IPA).

[0075] Subsequently, both the front and back surfaces of the glass substrate were polished using a double-sided polishing device under polishing conditions that maintained or improved the surface shape of the glass substrate surface. The glass substrate was then cleaned with an alkaline aqueous solution (NaOH).

[0076] For each of the mask blank substrates 1 obtained in Examples 1 to 3 and the mask blank substrates obtained in Comparative Examples 1 to 3, the surface shapes of the two main surfaces 2 and 3 were measured using a surface shape measuring device (Corning Tropel UltraFlat200M). As a result, the difference between the highest and lowest heights (flatness) in the inner region of a rectangle with sides of 132 mm, based on the center of the substrate 1, was 0.05 μm or less for all of the two main surfaces 2 and 3 of the mask blank substrate 1 in Examples 1 to 3 and the two main surfaces of the mask blank substrates in Comparative Examples 1 to 3. Furthermore, for each of the mask blank substrates in Examples 1 to 3 and Comparative Examples 1 to 3, a composite surface shape was generated in the inner region of a rectangle with sides of 132 mm, centered on the center of substrate 1. As a result, for all composite surface shapes, the difference between the highest and lowest heights (PV value) in the inner region of the rectangle with sides of 132 mm, centered on the center of the substrate, was 0.05 μm or less.

[0077] Then, for each of the mask blank substrates 1 in Examples 1 to 3, the spatial frequency fr[mm] was determined from the composite surface shape. -1 ] and power spectral density Pr[μm 2 / (mm -1 The relationship between ) was calculated for each of them. Similarly, for Comparative Examples 1 to 3, the spatial frequency fr[mm] was calculated from the composite surface shape. -1 ] and power spectral density Pr[μm 2 / (mm -1 The relationship between ( ) and ( ) was calculated. In the calculation of power spectral density Pr in all of Examples 1-3 and Comparative Examples 1-3, the data interval L was set to 132 [mm] and the number of data points N to 228 [points], and 4.59 × 10⁻¹⁰ was calculated. -3 [mm -1 These were calculated at intervals of spatial frequency fr.

[0078] Figures 3 to 5 are graphs showing the power spectral density curve and threshold curve for the mask blank substrate of Example 1 against spatial frequency. As shown in Figure 3, in Example 1, 0.02 [mm -1 ] or more 0.40[mm -1 In the spatial frequency range fr below, all power spectral densities are within the threshold curve (Pr=(1.5141×10) -6 )×(fr -1.3717 It had a value smaller than the curve of ). That is, in Example 1, it was 0.02 [mm -1 ] or more 0.40[mm -1 In the spatial frequency range fr below ], Pr < (1.5141 × 10 -6 )×(fr -1.3717 The spatial frequency fr that satisfies the relationship ) is 100%, and it also satisfies the condition of being 75% or higher.

[0079] Furthermore, as shown in Figure 4, in Example 2, 0.02 [mm -1 ] or more 0.40[mm -1In the spatial frequency range fr below ], the power spectral density at 86% had a value smaller than the threshold curve. That is, in Example 2, at the spatial frequency fr of 86%, Pr < (1.5141 × 10 -6 )×(fr -1.3717 The relationship ) was satisfied and the condition of 75% or more was met. Furthermore, as shown in Figure 5, in Example 3, 0.02 [mm -1 ] or more 0.40[mm -1 In the spatial frequency range fr below ], the power spectral density at 78% had a value smaller than the threshold curve. That is, in Example 3, at spatial frequency fr of 78%, Pr < (1.5141 × 10 -6 )×(fr -1.3717 The relationship ) was satisfied and the condition of 75% or more was met.

[0080] On the other hand, Figures 6 to 8 are graphs showing the power spectral density curves and threshold curves of the mask blank substrates for Comparative Examples 1 to 3 against spatial frequency. As shown in Figures 6 to 8, in Comparative Examples 1 to 3, 0.02 [mm -1 ] or more 0.40[mm -1 In the following spatial frequency range fr, the power spectral densities of 44%, 17%, and 2%, respectively, are defined by the threshold curve (Pr=(1.5141×10) -6 )×(fr -1.3717 The curve of the ) only had small values. That is, all of Comparative Examples 1 to 3 had values ​​of 0.02 [mm -1 ] or more 0.40[mm -1 In the spatial frequency range fr below ], at spatial frequencies fr of 75% or higher, Pr < (1.5141 × 10 -6 )×(fr -1.3717 It did not satisfy the relationship.

[0081] <Manufacturing of multilayer reflective film substrates> Next, using the mask blank substrate 1 from Examples 1 to 3 and the mask blank substrate from Comparative Examples 1 to 3, respectively, the multilayer reflective film substrate 10 from Examples 1 to 3 and the multilayer reflective film substrate from Comparative Examples 1 to 3 were fabricated. The film deposition of the multilayer reflective film substrate 10 in Examples 1 to 3 was carried out as follows. Specifically, using a Mo target and a Si target, Mo layers (low refractive index layer, thickness 2.8 nm) and Si layers (high refractive index layer, thickness 4.2 nm) were alternately stacked (40 pairs of stacks) by ion beam sputtering, and the multilayer reflective film 4 was formed on the mask blank substrate 1 described above. After the formation of the multilayer reflective film 4, a protective film 6 (Ru film, thickness 2.5 nm) was continuously formed on the multilayer reflective film 4 by DC sputtering. Subsequently, a conductive film 5 (TaBN film) was formed on the main surface 3 by sputtering to form the multilayer reflective film substrate 10. As described above, the multilayer reflective film substrates 10 in Examples 1 to 3 were manufactured. The same procedure was followed to manufacture the multilayer reflective film substrates in Comparative Examples 1 to 3.

[0082] For the multilayer reflective film substrates 10 in Examples 1 to 3 and the multilayer reflective film substrates in Comparative Examples 1 to 3 obtained in this manner, the composite surface shape was calculated in the same way as for the mask blank substrate 1 in Examples 1 to 3 and the mask blank substrates in Comparative Examples 1 to 3. Specifically, in Examples 1 to 3, a composite surface shape was generated from the surface shape of the protective film 6 and the surface shape of the conductive film 5 in the inner region of a rectangle with sides of 132 mm based on the center of the substrate 1, and the spatial frequency fr[mm] was calculated by removing the substrate deformation component caused by film stress from the composite surface shape. -1 ] and power spectral density Pr[μm 2 / (mm -1 The relationship between ( ) and ( ) was calculated. The same calculation was also performed for the multilayer reflective film substrates of Comparative Examples 1 to 3.

[0083] As a result, in all of the multilayer reflective film substrates 10 of Examples 1 to 3, the thickness was 0.02 [mm -1 ] or more 0.40[mm -1 In the spatial frequency range fr below ], at spatial frequencies fr of 75% or higher, Pr < (1.5141 × 10 -6 )×(fr -1.3717 It satisfied the relationship of ). On the other hand, in all of the multilayer reflective film substrates of Comparative Examples 1 to 3, 0.02 [mm -1 ] or more 0.40[mm -1 In the spatial frequency range fr below ], at spatial frequencies fr of 75% or higher, Pr < (1.5141 × 10 -6 )×(fr -1.3717 It did not satisfy the relationship.

[0084] <Manufacturing of mask blanks> Next, an absorber film 11 (TaBN film, thickness 55 nm) was deposited on the surface of the protective film 6 of the multilayer reflective film substrate 10 in Examples 1 to 3 described above by DC magnetron sputtering. In this manner, mask blanks 20 for Examples 1 to 3 were obtained. Mask blanks for Comparative Examples 1 to 3 were prepared in the same manner. For the mask blanks 20 obtained in Examples 1 to 3 in this manner, the composite surface shape was calculated in the same way as for the mask blank substrate 1. For each of these, a composite surface shape was generated from the surface shape of the absorber film 11, which is a thin film for pattern formation, and the surface shape of the conductive film 5 within the inner region of a rectangle with sides of 132 mm, with the center of the substrate 1 as the reference point. From this composite surface shape, the substrate deformation component caused by film stress was removed to obtain a spatial frequency fr[mm]. -1 ] and power spectral density Pr[μm 2 / (mm -1 The relationship between ( ) and ( ) was calculated. The same relationship was calculated for Comparative Examples 1 to 3.

[0085] As a result, in all of the mask blanks 20 of Examples 1 to 3, the result was 0.02 [mm -1 ] or more 0.40[mm -1 In the spatial frequency range fr below ], at spatial frequencies fr of 75% or higher, Pr < (1.5141 × 10 -6 )×(fr -1.3717 It satisfied the relationship of ). On the other hand, in all of the mask blanks 20 of Comparative Examples 1 to 3, 0.02 [mm -1 ] or more 0.40[mm -1In the spatial frequency range fr below ], at spatial frequencies fr of 75% or higher, Pr < (1.5141 × 10 -6 )×(fr -1.3717 It did not satisfy the relationship.

[0086] <Fabrication of a reflective mask> A resist was applied to the surface of the absorber film 11 of the reflective mask blank 20 of Examples 1 to 3 by spin coating, forming a resist film with a thickness of 100 nm. Next, a resist pattern was formed by drawing and developing the desired pattern. Using this resist pattern as a mask, the absorber film 11 was patterned by predetermined dry etching, forming an absorber pattern on the protective film 6. Subsequently, the resist film was removed, and chemical cleaning was performed to prepare the reflective masks of Examples 1 to 3. The same procedure was followed to prepare the reflective masks of Comparative Examples 1 to 3.

[0087] <Manufacturing of semiconductor devices> Using the reflective masks obtained in Examples 1-3, we performed pattern transfer onto a semiconductor substrate using an exposure apparatus that uses EUV light as the exposure light. As a result, we confirmed that it is possible to form patterns that meet the required desired overlay accuracy, without misalignment, and with high positional accuracy. On the other hand, when pattern transfer was performed onto a semiconductor substrate using the reflective masks prepared as Comparative Examples 1 to 3 and an exposure apparatus that uses EUV light as the exposure light, the required desired overlay accuracy was not met, resulting in misalignment of the transferred pattern and failure to perform high-precision pattern transfer. [Explanation of Symbols]

[0088] 1…Mask blank substrate, 2…(one) main surface, 3…(the other) main surface, 4...Multilayer reflective film, 5...Conductive film, 6...Protective film 10…Multilayer reflective film substrate, 11…Absorbing film (thin film for pattern formation), 20… Mask Blank

Claims

1. A mask blank substrate having two opposing main surfaces, Within the inner region of a rectangle with sides of 132 mm, with respect to the center of the substrate, a composite surface shape is generated from the surface shapes of the two main surfaces of the substrate, and the spatial frequency fr[mm] is obtained from this composite surface shape. －１ ] and power spectral density Pr [μm ２ / (mm －１ When calculating the relationship between ) ], 0.02 [mm] －１ ] or more 0.40 [mm －１ Within the following range of spatial frequencies fr, at least 75% of spatial frequencies fr must be such that Pr < (1.5141 × 10⁻¹⁰ －６ ) × (fr －１．３７１７ The relationship satisfies A substrate for mask blanks characterized by the following features.

2. The composite surface shape is obtained by adding together the surface shape of one main surface, which is the in-plane distribution of height from a reference plane that serves as the basis for the surface shape of one main surface to the one main surface, and the surface shape of the other main surface, which is the in-plane distribution of height from a reference plane that serves as the basis for the surface shape of the other main surface to the other main surface. This is the mask blank substrate according to claim 1.

3. The power spectral density Pr is 1.0 × 10 －２ [mm －１ or less, and is calculated for each interval of the spatial frequency fr, and the substrate for a mask blank according to claim 1 or 2, characterized in that

4. A multilayer reflective substrate characterized in that a multilayer reflective film is provided on one of the main surfaces of the mask blank substrate according to any one of claims 1 to 3.

5. A multilayer reflective substrate having two opposing main surfaces, wherein one of the main surfaces is provided with a multilayer reflective film, and the other main surface is provided with a conductive film, Within the inner region of a rectangle with sides of 132 mm, with respect to the center of the substrate, a composite surface shape is generated from the surface shape of the multilayer reflective film and the surface shape of the conductive film, and the spatial frequency fr[mm] is obtained from this composite surface shape. －１ ] and power spectral density Pr [μm ２ / (mm －１ When calculating the relationship between ) ], 0.02 [mm] －１ ] or more 0.40 [mm －１ Within the following range of spatial frequencies fr, at least 75% of spatial frequencies fr must be such that Pr < (1.5141 × 10⁻¹⁰ －６ ) × (fr －１．３７１７ The relationship satisfies A multilayer reflective film substrate characterized by the following features.

6. The substrate with a multilayer reflective film according to claim 5, characterized in that the composite surface shape is obtained by adding the surface shape of the multilayer reflective film, which is the in-plane distribution of height from a reference plane that serves as the basis for the surface shape of the multilayer reflective film to the surface of the multilayer reflective film, and the surface shape of the conductive film, which is the in-plane distribution of height from a reference plane that serves as the basis for the surface shape of the conductive film to the surface of the conductive film.

7. The power spectral density Pr is 1.0 × 10⁻⁶ －２ [mm －１ The multilayer reflective substrate according to claim 5 or 6, characterized in that it is calculated for each interval of the spatial frequency fr as follows.

8. A mask blank characterized in that a thin film for pattern formation is provided on the multilayer reflective film of a substrate with a multilayer reflective film according to any one of claims 5 to 7.

9. A mask blank comprising a pattern-forming thin film on one of the main surfaces of a substrate having two opposing main surfaces, and a conductive film on the other main surface, Within the inner region of a rectangle with sides of 132 mm, with respect to the center of the substrate, a composite surface shape is generated from the surface shape of the pattern-forming thin film and the surface shape of the conductive film, and the spatial frequency fr[mm] is obtained from the composite surface shape. －１ ] and power spectral density Pr [μm ２ / (mm －１ When calculating the relationship between ) ], 0.02 [mm] －１ ] or more 0.40 [mm －１ Within the following range of spatial frequencies fr, at least 75% of spatial frequencies fr must be such that Pr < (1.5141 × 10⁻¹⁰ －６ ) × (fr －１．３７１７ The relationship satisfies A mask blank characterized by the following features.

10. The mask blank according to claim 9, characterized in that the composite surface shape is obtained by adding the surface shape of the pattern-forming thin film, which is the in-plane distribution of height from a reference plane that serves as the basis for the surface shape of the pattern-forming thin film to the surface of the pattern-forming thin film, and the surface shape of the conductive film, which is the in-plane distribution of height from a reference plane that serves as the basis for the surface shape of the conductive film to the surface of the conductive film.

11. The power spectral density Pr is 1.0 × 10⁻⁶ －２ [mm －１ The mask blank according to claim 9 or 10, characterized in that it is calculated for each interval of the spatial frequency fr as follows.

12. A mask blank according to any one of 9 to 11, characterized in that it has a multilayer reflective film between one of the main surfaces and the pattern-forming thin film.

13. A method for manufacturing a transfer mask, characterized by comprising the step of forming a transfer pattern on the pattern-forming thin film of the mask blank according to any one of claims 9 to 12.

14. A method for manufacturing a semiconductor device, characterized by setting a transfer mask manufactured by the method for manufacturing a transfer mask described in claim 13 on a mask stage of an exposure apparatus, and transferring the transfer pattern of the transfer mask onto a semiconductor substrate by lithography.

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