Substrate with conductive film, reflective mask blank, reflective mask, and semiconductor device manufacturing method

Abstract

Provided is a substrate with a conductive film with which it is possible to manufacture a reflective mask capable of satisfying desired overlay accuracy in EUV lithography.　This substrate with a conductive film comprises a substrate having a first main surface and a second main surface facing the first main surface, and a conductive film provided on the second main surface, the substrate with a conductive film being characterized in that on the surface of the conductive film, when the surface shape of a quadrangular first inner region, which is a square with sides of 104 mm centered on the second main surface, is expressed using the Legendre polynomial (1), the absolute value of the coefficient akl of at least one term selected from among terms satisfying the conditions 4 ≤ k + l ≤ 10, where k + l is an even number and k is an even number of 2 or greater, is 2 nm or less.

Description

Conductive film coated substrate, reflective mask blank, reflective mask, and method for manufacturing a semiconductor device

[0001] The present invention relates to a conductive film-coated substrate, a reflective mask blank, a reflective mask, and a method for manufacturing a semiconductor device. In particular, the present invention relates to a conductive film-coated substrate and a reflective mask blank for manufacturing a reflective mask for use in EUV lithography in a method for manufacturing a semiconductor device.

[0002] In recent years, with the increasing demand for higher density and precision in ultra-large-scale integrated (ULSI) devices, EUV lithography, an exposure technique using extreme ultraviolet (EUV) light, has been developed.

[0003] A reflective mask has a multilayer reflective film formed on a substrate to reflect exposure light, and an absorber pattern, which is a patterned absorber film formed on the multilayer reflective film to absorb exposure light. The light image reflected by the multilayer reflective film is transferred to a semiconductor substrate (transfer target) such as a silicon wafer through a reflective optical system.

[0004] A reflective mask blank for manufacturing a reflective mask has a multilayer reflective film and an absorbent film on a substrate. A reflective mask can be manufactured by patterning the absorbent film of the reflective mask blank to create an absorbent pattern. As the substrate for manufacturing the reflective mask blank, a substrate with a conductive film for electrostatic chucks (referred to as a "conductive film substrate") can be used.

[0005] As an example of a substrate for manufacturing a reflective mask, Patent Document 1 describes a mask blank substrate having two main surfaces, a first main surface and a second main surface, each measuring 152 mm × 152 mm, and having a thickness of 6.35 mm. Patent Document 1 describes that, for the mask blank substrate of Patent Document 1, when the calculation area is defined as a 132 mm × 132 mm square area centered on the intersection of the diagonals of each of the first and second main surfaces, the flatness of the substrate surface of at least one of the calculation areas of the first and second main surfaces, relative to the least squares plane of the substrate surface in the calculation area, is 100 nm or less, and the difference (PV) between the highest and lowest height values ​​of the calculation surface, which is represented by the difference between the shape of the substrate surface before smoothing treatment by a Gaussian filter (10 mm × 10 mm) and the shape after the smoothing treatment, relative to the least squares plane, is 20 nm or less.

[0006] Patent Document 2 describes a mask blank comprising a glass substrate having a first main surface and a second main surface facing the first main surface, a film formed on the first main surface on which a circuit pattern is formed, and a conductive film formed on the second main surface. Patent Document 2 further describes that the film on which the circuit pattern is formed is an absorbing film that absorbs light, and that a reflective film that reflects light is provided between the absorbing film and the glass substrate. Furthermore, Patent Document 2 describes that, of the conductive film on the side opposite to the glass substrate, the central square region with dimensions of 142 mm vertically and 142 mm horizontally, excluding its rectangular outer peripheral region, is expressed by the following formula, and all a where the sum of k and l in the following formula is 3 or more and 25 or less ｋｌ P ｋ (x) P ｌ It is stated that the flatness of the component obtained by adding (y) is 20 nm or less. Patent Document 2 states that in the following formula, x is the horizontal coordinate, y is the vertical coordinate, and z is the height coordinate, and the horizontal, vertical, and height directions are perpendicular to each other, and k and l are natural numbers between 0 and 25, and the sum of k and l is between 3 and 25, N １ and N ２ It is stated that each of them is 25.

[0007] Patent Document 3 describes a mask blank substrate consisting of a substrate having two opposing main surfaces. Patent Document 3 describes that when difference data is obtained by performing shape fitting between a composite surface shape obtained by combining the surface shapes of the two main surfaces in a calculation region inside a circle with a diameter of 104 mm based on the center of the substrate and a virtual surface shape, the difference between the highest and lowest heights of the difference data within the calculation region is 25 nm or less, and the virtual surface shape is a Zernike polynomial expressed in polar coordinates, and has a shape defined by a Zernike polynomial that consists only of terms with a degree of 2 or less for the radius variable, and that includes one or more terms with a degree of 2 for the radius variable.

[0008] Japanese Patent Publication No. 2024-2066, Japanese Patent Publication No. 6229807, Japanese Patent Publication No. 6033987

[0009] 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 causes a discrepancy in the dimensions of the circuit pattern formed on the wafer, resulting in a semiconductor device that does not meet 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 semiconductor device that cannot achieve 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). As the circuit dimensions of the semiconductor device decrease, smaller overlay accuracy is required.

[0010] However, it has been found that even with substrates that meet conventional requirements such as flatness, the desired overlay accuracy may not be obtained when using reflective masks fabricated from these substrates during EUV lithography.

[0011] In the EUV lithography process for manufacturing semiconductor devices, a reflective mask is fixed to the exposure apparatus by an electrostatic chuck. A conductive film is formed on the second main surface (the main surface opposite to the main surface on which the multilayer reflective film is formed; also called the "back surface") of an insulating reflective mask blank substrate such as a glass substrate, in order to facilitate the fixing of the substrate by the electrostatic chuck. In this specification, a substrate on which a conductive film is formed is called a conductive film substrate. It has been found that, similar to the substrates described above, the desired overlay accuracy may not be obtained when using a reflective mask made with a conductive film substrate during EUV lithography.

[0012] Therefore, the present invention aims to provide a conductive film-coated substrate that can produce a reflective mask that can satisfy the desired overlay accuracy during EUV lithography.

[0013] Furthermore, the present invention aims to provide a reflective mask blank and a reflective mask manufactured using the above-mentioned conductive film-coated substrate, as well as a method for manufacturing a semiconductor device using the reflective mask.

[0014] To solve the above problems, the present invention has the following configuration.

[0015] (Configuration 1) Configuration 1 is a conductive film substrate having a first main surface and a second main surface facing the first main surface, and a conductive film provided on the second main surface, wherein, on the surface of the conductive film, when the surface shape of a first inner region of a rectangle with sides of 104 mm, with respect to the center of the second main surface, is expressed by Legendre polynomial (1), the coefficient a of at least one term selected from terms that satisfy 4 ≤ k + l ≤ 10, k + l is even, and k is an even number of 2 or more ｋｌ This is a conductive film-coated substrate characterized by having an absolute value of 2 nm or less. x: Position in a predetermined direction inside the first inner region y: Position in a direction orthogonal to the x direction inside the first inner region k and l: Integers of 0 or more respectively N １ = 10 N ２ = N １ - k

[0016] (Configuration 2) Configuration 2 is characterized in that the absolute value of the coefficient a of the fourth-order term P ４ (x) P ０ (y) is 2 nm or less, and it is a substrate with a conductive film of Configuration 1 ４０

[0017] (Configuration 3) Configuration 3 further has the absolute value of the coefficient a of the fourth-order term P ０ (x) P ４ (y) being 2 nm or less, and it is a substrate with a conductive film of Configuration 1 ０４

[0018] (Configuration 4) Configuration 4 further has the absolute value of the coefficient a of the fifth-order term P ０ (x) P ５ (y) being 2 nm or less, and it is a substrate with a conductive film of any one of Configurations 1 to 3 ０５

[0019] (Configuration 5) Configuration 5 has a flatness of 50 nm or less, and the flatness is the difference between the highest height and the lowest height when the 0th, 1st, and 2nd order components are removed in a second inner region of a square with a side of 142 mm centered on the center of the second main surface on the surface of the conductive film, and it is a substrate with a conductive film of any one of Configurations 1 to 4

[0020] (Configuration 6) Configuration 6 is characterized in that the conductive film contains at least one element selected from tantalum (Ta) and chromium (Cr), and it is a substrate with a conductive film of any one of Configurations 1 to 5

[0021] (Configuration 7) Configuration 7 is a reflective mask blank having a substrate having a first main surface and a second main surface facing the first main surface, a conductive film provided on the second main surface of the substrate, a multilayer reflective film provided on the first main surface of the substrate, and an absorber film provided on the multilayer reflective film, wherein on the surface of the conductive film, when the surface shape of a first inner region of a rectangle with sides of 104 mm with respect to the center of the second main surface is expressed by Legendre polynomial (1), the coefficient a of at least one term selected from terms that satisfy 4 ≤ k + l ≤ 10, k + l is even, and k is an even number of 2 or more ｋｌ This is a reflective mask blank characterized by having an absolute value of 2 nm or less. x: A position in a predetermined direction within the first inner region y: A position in a direction perpendicular to the direction of x within the first inner region k and l: Each an integer greater than or equal to 0 N １ = 10 N ２ = N １ -k

[0022] (Configuration 8) Configuration 8 is a quartic term P where k + l is 4 and k is 4. ４ (x) P ０ Coefficient a of (y) ４０ This is a reflective mask blank of configuration 7, characterized in that the absolute value of is 2 nm or less.

[0023] (Configuration 9) Configuration 9 further includes a quartic term P where k + l is 4 and k is 0. ０ (x) P ４ Coefficient a of (y) ０４ This is a reflective mask blank of configuration 7, characterized in that the absolute value of is 2 nm or less.

[0024] (Configuration 10) Configuration 10 further comprises a 5th-degree term P where k+l is 5 and k is 0. ０ (x) P ５ Coefficient a of (y) ０５ A reflective mask blank of any of configurations 7 to 9, characterized in that the absolute value of is 2 nm or less.

[0025] (Configuration 11) Configuration 11 is a reflective mask blank of any of Configurations 7 to 10, characterized in that the flatness is 50 nm or less, and the flatness is the difference between the highest and lowest heights when the 0th, 1st, and 2nd order components are removed in a second inner region of a rectangle with sides of 142 mm, with the center of the second main surface as the reference point, on the surface of the conductive film.

[0026] (Configuration 12) Configuration 12 is a reflective mask blank of any of Configurations 7 to 11, characterized in that the conductive film contains at least one element selected from tantalum (Ta) and chromium (Cr).

[0027] (Configuration 13) Configuration 13 is a reflective mask comprising: a substrate having a first main surface and a second main surface facing the first main surface; a conductive film provided on the second main surface of the substrate; a multilayer reflective film provided on the first main surface of the substrate; and an absorbent film provided on the multilayer reflective film on which a transfer pattern is formed, wherein, on the surface of the conductive film, when the surface shape of a first inner region of a rectangle with sides of 104 mm with respect to the center of the second main surface is expressed by Legendre polynomial (1), the coefficient a of at least one term selected from terms satisfying 4 ≤ k + l ≤ 10, k + l is even, and k is an even number of 2 or more ｋｌ This reflective mask is characterized by having an absolute value of 2 nm or less. x: A position in a predetermined direction within the first inner region y: A position in a direction perpendicular to the direction of x within the first inner region k and l: Each an integer greater than or equal to 0 N １ = 10 N ２ = N １ -k

[0028] (Configuration 14) Configuration 14 is a quartic term P where k + l is 4 and k is 4. ４ (x) P ０ Coefficient a of (y) ４０ This is a reflective mask with configuration 13, characterized in that the absolute value of is 2 nm or less.

[0029] (Configuration 15) Configuration 15 further includes a quartic term P where k + l is 4 and k is 0.０ (x) P ４ Coefficient a of (y) ０４ This is a reflective mask with configuration 13, characterized in that the absolute value of is 2 nm or less.

[0030] (Configuration 16) Configuration 16 further comprises a 5th-degree term P where k + l is 5 and k is 0. ０ (x) P ５ Coefficient a of (y) ０５ A reflective mask of any of configurations 13 to 15, characterized in that the absolute value of is 2 nm or less.

[0031] (Configuration 17) Configuration 17 is a reflective mask of any of Configurations 13 to 16, characterized in that the flatness is 50 nm or less, and the flatness is the difference between the highest and lowest heights when the 0th, 1st, and 2nd order components are removed in a second inner region of a rectangle with sides of 142 mm, with the center of the second main surface as the reference point, on the surface of the conductive film.

[0032] (Configuration 18) Configuration 18 is a reflective mask according to any of Configurations 13 to 17, characterized in that the conductive film contains at least one element selected from tantalum (Ta) and chromium (Cr).

[0033] (Configuration 19) Configuration 19 is a method for manufacturing a semiconductor device, characterized by having a step of forming a transfer pattern on a transfer object by performing a lithography process using an exposure apparatus with a reflective mask of any of Configurations 13 to 15.

[0034] According to the present invention, it is possible to provide a conductive film-coated substrate that can produce a reflective mask that can satisfy the desired overlay accuracy during EUV lithography.

[0035] Furthermore, according to the present invention, it is possible to provide a reflective mask blank and a reflective mask manufactured using the above-mentioned conductive film-coated substrate, as well as a method for manufacturing a semiconductor device using the reflective mask.

[0036] This is a schematic cross-sectional diagram showing an example of a conductive film-coated substrate according to this embodiment. This is a schematic cross-sectional diagram showing an example of a conductive film-coated substrate (multilayer reflective film-coated substrate) according to this embodiment. This is a schematic cross-sectional diagram showing another example of a conductive film-coated substrate (multilayer reflective film-coated substrate) according to this embodiment. This is a schematic cross-sectional diagram showing an example of a reflective mask blank according to this embodiment. This is a schematic cross-sectional diagram showing another example of a reflective mask blank according to this embodiment. This is a schematic diagram showing an example of a reflective mask manufacturing method according to this embodiment. This is a schematic diagram showing an example of an EUV exposure apparatus. This is a schematic diagram showing an example of a surface on which a conductive film is formed on a conductive film-coated substrate according to this embodiment.

[0037] The embodiments of the present invention will be described in detail below with reference to the drawings. Note that the following embodiments are intended to illustrate the present invention in detail and do not limit the present invention to their scope.

[0038] Figure 1 is a schematic cross-sectional view showing an example of a conductive film-coated substrate 40 of this embodiment. The conductive film-coated substrate 40 of this embodiment has a structure in which a conductive film 42 is disposed on one main surface (second main surface, or back surface) of the substrate 1. In this specification, a conductive film-coated substrate 40 is defined as one in which a conductive film 42 is formed on at least one main surface (second main surface, or back surface) of the substrate 1. A multilayer reflective film-coated substrate 90 (see Figures 2 and 3), in which a multilayer reflective film 2 is formed on the other main surface (first main surface, or front surface) of the substrate 1 of the conductive film-coated substrate 40, and a reflective mask blank 100 (see Figures 4 and 5), in which an absorber film 4 is further formed, are also included in the conductive film-coated substrate 40.

[0039] Figure 2 shows an example of a multilayer reflective substrate 90. In the multilayer reflective substrate 90 shown in Figure 2, a multilayer reflective film 2 is formed on the first main surface of the substrate 1. A conductive film 42 is formed on the second main surface (back surface) of the substrate 1 of the multilayer reflective substrate 90 shown in Figure 2. Since the multilayer reflective substrate 90 shown in Figure 2 includes a conductive film 42 on the second main surface (back surface) of the substrate 1, it is a type of conductive substrate 40.

[0040] Figure 3 shows another example of a multilayer reflective substrate 90. A multilayer reflective film 2 and a protective film 3 are formed on the main surface of the multilayer reflective substrate 90 shown in Figure 3. A conductive film 42 is formed on the second main surface (back surface) of the substrate 1 of the multilayer reflective substrate 90 shown in Figure 3. Since the multilayer reflective substrate 90 shown in Figure 3 includes a conductive film 42 on the second main surface (back surface) of the substrate 1, it is a type of conductive substrate 40.

[0041] Figure 4 is a schematic cross-sectional view showing an example of a reflective mask blank 100 according to this embodiment. The reflective mask blank 100 in Figure 4 has a multilayer reflective film 2, a protective film 3, and an absorbent film 4. Furthermore, the reflective mask blank 100 shown in Figure 4 has a conductive film 42 on the second main surface (back surface). Therefore, the reflective mask blank 100 shown in Figure 4 is a type of conductive film-coated substrate 40.

[0042] Figure 5 is a schematic cross-sectional view showing another example of the reflective mask blank 100 of this embodiment. The reflective mask blank 100 shown in Figure 5 has an etching mask film 6 on an absorber film 4. When manufacturing a reflective mask 200 using the reflective mask blank 100 having the etching mask film 6, the etching mask film 6 may be peeled off after forming a transfer pattern on the absorber film 4, as described later. Furthermore, the reflective mask blank 100 of this embodiment includes a conductive film 42 on its back surface. Therefore, the reflective mask blank 100 shown in Figure 5 is a type of conductive film-coated substrate 40.

[0043] Furthermore, in the reflective mask blank 100 shown in Figure 4, which does not form an etching mask film 6, the absorber film 4 can be made into a multi-layered structure. The materials constituting these multiple layers may be materials having different etching properties, thereby creating a reflective mask blank 100 with an absorber film 4 that has etching mask functionality.

[0044] In this specification, "having a thin film B on a thin film A (or substrate)" means not only that thin film B is placed (formed) in contact with the surface of thin film A (or substrate), but also that there is another thin film C between thin film A (or substrate) and thin film B. Furthermore, in this specification, for example, "thin film B is placed (formed) in contact with thin film A (or substrate)" means that thin film A (or substrate) and thin film B are placed (formed) in direct contact without any other thin film in between. Furthermore, in this specification, "on top" does not necessarily mean the upper side in the vertical direction. "On top" merely indicates the relative positional relationship between the thin film and the substrate, etc. In this specification, "thin film B is placed (formed) in contact with thin film A" can mean that thin film B is placed (formed) in contact with the surface of thin film A opposite to the substrate.

[0045] The conductive film substrate 40, the multilayer reflective film substrate 90, the reflective mask blank 100, and the reflective mask 200 of this embodiment will be described in detail.

[0046] <Conductive film-coated substrate 40> This embodiment is a conductive film-coated substrate 40 having a substrate 1 having a first main surface and a second main surface facing the first main surface, and a conductive film 42 provided on the second main surface.

[0047] <<Substrate 1>> The substrate 1 used for the conductive film substrate 40 of this embodiment has a first main surface and a second main surface opposite the first main surface. The first main surface is the main surface on which the multilayer reflective film 2 is formed.

[0048] To prevent distortion of the transfer pattern due to heat during exposure with EUV light, the substrate 1 is preferably made of a material with a low thermal expansion coefficient in the range of 0 ± 5 ppb / °C. Examples of materials with a low thermal expansion coefficient in this range include SiO ２ -TiO ２ Glass-based glass, multi-component glass-ceramics, etc., can be used.

[0049] The main surface (first main surface) of the substrate 1 on the side where the transfer pattern (absorber pattern 4a described later) is formed is preferably processed to increase its flatness. By increasing the flatness of the main surface of the substrate 1, the positional accuracy and transfer accuracy of the pattern can be improved. For example, in the case of EUV exposure, the flatness of the 132 mm × 132 mm area of ​​the first main surface of the substrate 1 on the side 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. The second main surface (back surface) on the side opposite to the side where the transfer pattern is formed is the surface that is fixed to the exposure apparatus by an electrostatic chuck. In the 142 mm × 142 mm area of ​​the back surface, the flatness is preferably 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less. In this specification, flatness is the absolute value of the height difference between the highest position and the lowest position when the 0th, 1st, and 2nd order components are removed from all components of the surface of the substrate 1. In this specification, flatness may sometimes be referred to as the "PV value."

[0050] In the case of EUV exposure, the surface roughness of the first main surface on the side of the substrate 1 where the transfer pattern is formed is preferably 0.1 nm or less in terms of root mean square roughness (Rq). The surface roughness can be measured using an atomic force microscope.

[0051] The substrate 1 is preferably made of high rigidity in order to prevent deformation due to film stress of the thin film (such as the multilayer reflective film 2) formed thereon. In particular, the substrate 1 is preferably made of a high Young's modulus of 65 GPa or more.

[0052] <<Conductive film 42>> The conductive film-coated substrate 40 of this embodiment has a conductive film 42 for electrostatic chucks on the second main surface (back surface) of the substrate 1.

[0053] For electrostatic chucks, the sheet resistance required for the conductive film 42 is usually 100 Ω / □ (Ω / square) or less. The conductive film 42 can be formed, for example, by magnetron sputtering or ion beam sputtering using a target of a metal such as chromium or tantalum, or an alloy thereof. The material of the conductive film 42 is preferably a material containing chromium (Cr) or tantalum (Ta). For example, the material of the conductive film 42 is preferably a Cr compound containing Cr and at least one selected from boron, nitrogen, oxygen, and carbon. Examples of Cr compounds include CrN, CrON, CrCN, CrCON, CrBN, CrBON, CrBCN, and CrBOCN. Alternatively, the material of the conductive film 42 is preferably Ta (tantalum), an alloy containing Ta, or a Ta compound containing at least one of boron, nitrogen, oxygen, and carbon in any of these. Examples of Ta compounds include TaB, TaN, TaO, TaON, TaCON, TaBN, TaBO, TaBON, TaBCON, TaHf, TaHfO, TaHfN, TaHfON, TaHfCON, TaSi, TaSiO, TaSiN, TaSION, and TaSiCON.

[0054] In this embodiment, the conductive film 42 of the conductive film-coated substrate 40 preferably contains at least one element selected from tantalum (Ta) and chromium (Cr). By containing a predetermined element in the conductive film 42, appropriate conductivity can be obtained.

[0055] The conductive film 42 of the conductive film-coated substrate 40 in this embodiment can be a single-layer thin film or a multilayer film with multiple layers. The conductive film 42 of the conductive film-coated substrate 40 in this embodiment may include a thin film that does not have conductivity, such as an oxide film, as the outermost layer on the surface.

[0056] The thickness of the conductive film 42 is not particularly limited as long as it functions as a film for an electrostatic chuck. The thickness of the conductive film 42 is, for example, 10 nm to 200 nm.

[0057] <<Indicators of Surface Flatness of Conductive Film 42>> Figure 7 shows an example of a schematic diagram of an EUV exposure apparatus 50. In exposure using a reflective mask 200, there are two types of distortion that affect the overlay accuracy: in-plane distortion (IPD) and out-of-plane distortion (OPD). In-plane distortion (IPD) represents the displacement of the absorber pattern 4a caused by chucking the substrate 1 when the reflective mask 200 is electrostatically chucked, and depends only on the shape of the back surface. On the other hand, out-of-plane distortion (OPD) originates from the height difference of the first main surface during chucking and depends on the shape of both the front and back surfaces. By flattening both sides of the substrate 1, these two types of overlay accuracy can be improved.

[0058] Conventionally, the PV value has been commonly used as an indicator of flatness to estimate overlay accuracy. The PV value is a numerical value (absolute value) that represents the height difference between the highest and lowest positions when the 0th, 1st, and 2nd order components are removed from all components of the surface of the substrate 1. In this specification, the PV value may be referred to as "flatness."

[0059] Furthermore, Patent Document 2 describes how out-of-plane distortion (OPD) can be improved by setting the sum of the third to 25th order terms to 20 nm or less as a flatness index when the shape of the substrate surface is fitted with Legendre polynomials.

[0060] However, the method of managing overlay accuracy using the flatness index described above does not take into account the following two effects in EUV lithography.

[0061] One factor is the effect of correction by the EUV exposure apparatus 50 to improve overlay accuracy. In the case of in-plane distortion (IPD), the shape components of the back surface (second main surface) of order 3 or lower can be corrected by the EUV exposure apparatus 50. However, the current flatness index includes lower-order components that can be corrected by the EUV exposure apparatus 50. In other words, it is unnecessary to include lower-order components in the flatness index of the reflective mask 200.

[0062] Another factor is the effect of the electrostatic chuck on the second main surface (back surface) used to fix the reflective mask 200 to the exposure apparatus. According to structural mechanics, the higher the order of the flatness component of the surface shape of the substrate 1, that is, the higher the spatial frequency, the more difficult it becomes to flatten the surface when using the electrostatic chuck, and the smaller its contribution to in-plane distortion (IPD). However, current flatness indices treat each order with the same weight, which is considered to be physically incorrect.

[0063] From the above considerations, the inventors concluded that the PV value is not the optimal indicator for controlling overlay accuracy. Therefore, considering the correction function of the exposure apparatus and the frequency components of the surface shape of the substrate 1, the inventors found a new indicator for more accurately predicting overlay accuracy, leading to the present invention. The surface of the conductive film 42 on the conductive film-coated substrate 40 corresponds to the second main surface of the substrate 1. Therefore, on the surface of the conductive film 42 on the conductive film-coated substrate 40, the overlay accuracy can be controlled by the new indicator described above, just as on the substrate 1. Specifically, this indicator is as follows.

[0064] The surface of the conductive film 42 of the conductive film substrate 40 of this embodiment can be represented as follows. That is, on the surface of the conductive film 42 of the conductive film substrate 40 of this embodiment, when the surface shape of the first inner region 46 of a rectangle with sides of 104 mm based on the center of the second main surface is represented by Legendre polynomial (1), the coefficient a of at least one term selected from terms that satisfy 4 ≤ k + l ≤ 10, k + l is even, and k is an even number of 2 or more is ｋｌ The absolute value of is 2 nm or less. Coefficient a ｋｌ The absolute value of is preferably 2.0 nm or less, more preferably 1.5 nm or less, even more preferably 1.0 nm or less, and particularly preferably 0.5 nm or less. ｋｌ The absolute value of is greater than 0 nm.

[0065]

[0066] Note that x corresponds to a position in a predetermined direction within the first inner region 46. The x-direction is the same direction as any one side of the first inner region 46 of the quadrilateral. y corresponds to a position in the direction perpendicular to the x-direction (y-direction) within the first inner region 46. k and l are each integers greater than or equal to 0. N １ It is 10, N ２ is, N １ -k.

[0067] As described above, the flatness component of the back surface (second main surface) of order 3 or lower in the x-direction can be corrected by the EUV exposure apparatus 50. Furthermore, the higher the order of the frequency component of the surface shape of the substrate 1, the less it contributes to in-plane distortion (IPD). On the other hand, the 4th to 10th order terms P ｋ (x) P ｌ (y) (i.e., 4 ≤ k + l ≤ 10), and terms where k + l is even and k is 2 or more are presumed to correlate with the shape polished in the polishing process, and it was found that they contribute significantly to in-plane distortion (IPD). Therefore, by having the surface shape of the first inner region 46 of the conductive film 42 of the conductive film substrate 40 of this embodiment be the surface shape described above, in-plane distortion (IPD) can be reduced. As a result, by manufacturing a reflective mask 200 using the conductive film substrate 40 of this embodiment, the reflective mask 200 can satisfy the desired overlay accuracy during EUV lithography.

[0068] Furthermore, in-plane distortion (IPD) can be calculated using the following equation (2). The in-plane distortion (IPD) is the maximum value in the x-direction of the IPD calculated by the following equation. In this specification, unless otherwise specified, IPD is in the x-direction. IPD = 1 / 2 × T × Φ(x,y) × 1 / 4 ... (2) T: Thickness of the substrate Φ(x,y): First-order partial derivative of the shape of the second main surface (back surface)

[0069] The desired overlay accuracy can be within the following range: that is, coefficient a ｋｌ If the absolute value of is 2 nm or less, the in-plane strain (IPD) can be reduced to 0.17 nm or less. Coefficient a ｋｌIf the absolute value of is 1.5 nm or less, the in-plane distortion (IPD) can be reduced to 0.15 nm or less. Coefficient a ｋｌ If the absolute value of is 1 nm or less, the in-plane strain (IPD) can be reduced to 0.12 nm or less. Coefficient a ｋｌ If the absolute value of is 0.5 nm or less, the in-plane distortion (IPD) can be reduced to 0.1 nm or less.

[0070] Figure 8 shows a schematic diagram of an example of a surface on which the conductive film 42 is formed on the conductive film substrate 40 of this embodiment. In this specification, the surface on which the conductive film 42 is formed on the conductive film substrate 40 is referred to as the "second main surface of the conductive film substrate 40" (or simply the "second main surface"). The substrate 1 of the conductive film substrate 40 shown in Figure 8 can be a rectangle with dimensions of 152.4 mm × 152.4 mm. On the second main surface of the conductive film substrate 40 shown in Figure 8, the first inner region 46 has sides of length L. １ It is a rectangle of (mm). The center position of the first inner region 46 is the same as the center position of the substrate 1.

[0071] The length L of one side of the first inner region 46 １ (mm) is L １ = 104 mm. When a reflective mask 200 manufactured using the conductive film substrate 40 is electrostatically chucked, the planarization area where the second main surface of the reflective mask 200 is planarized may include the first inner region 46.

[0072] In the second main surface of the conductive film-coated substrate 40 shown in Figure 8, the x-direction of the first inner region 46 is horizontal. Let X (mm) be the x-coordinate of the first inner region 46. The center of the x-direction of the first inner region 46 is X. ０ to X ０ Set to = 0 mm, and set the right end of the first inner region 46 in the x direction to X １ = + L １ Let it be / 2 (mm), and set the left end in the x direction to X ２ = -L １ It can be set to / 2 (mm). In this case, the range of the first inner region 46 in the x direction is -L １ / 2 to +L １The range is 2 / L. Legendre polynomial (1) is a polynomial whose domain is orthogonal in the range of -1 to +1. Therefore, x in Legendre polynomial (1) is x = 2 * X / L １ Therefore, the range of x in Legendre polynomial (1) is from -1 to +1.

[0073] In the second main surface of the conductive film-coated substrate 40 shown in Figure 8, the y-direction of the first inner region 46 is perpendicular to the x-direction. Therefore, in Figure 8, the y-direction of the first inner region 46 is the vertical direction. Similar to the x-direction, the center Y-direction of the first inner region 46 is also defined. ０ to Y ０ Set = 0 mm, and set the upper end of the first inner region 46 in the y direction to Y １ = + L １ Let it be / 2 (mm), and the lower end in the y direction be Y ２ = -L １ It can be set to / 2 (mm). In this case, the range in the y direction of the first inner region 46 is -L １ / 2 to +L １ It is in the range of / 2. The value of y in Legendre polynomial (1) is y = 2 * Y / L １ Therefore, the range of y in Legendre polynomial (1) is from -1 to +1.

[0074] As described above, if z(x,y) is the surface height of the first inner region 46 of the conductive film 42 on the second main surface of the conductive film substrate 40, then z(x,y) can be expressed by Legendre polynomial (1). When the surface shape in the x direction of the first inner region 46 is expressed by Legendre polynomial (1), the fourth-order term where k+l is 4 and k is 4 is a ４０ P ４ (x) P ０ It can be expressed as (y). a ４０ P ４ (x) P ０ This is the coefficient of (y).

[0075] Similarly, for the y-direction of the first inner region 46, when the surface shape of the first inner region 46 in the y-direction is expressed by Legendre polynomial (1), the fourth-order term where k+l is 4 and k is 0 is a ０４ P０ (x)P ４ can be expressed as (y). a ０４ is the coefficient of P ０ (x)P ４ (y).

[0076] The x direction can be set in the same direction as any one side of the quadrilateral of the first inner region 46. The y direction can be set in a direction orthogonal to the x direction.

[0077] By fitting the height z(x, y) of the surface of the first inner region 46 with the Legendre polynomial (1), z(x, y) can be expressed by the Legendre polynomial (1) in the x direction and the y direction. As the Legendre polynomial (1) for fitting, a Legendre polynomial (1) with k + l being 4, 6, 8 or 10 and a maximum degree N １ being a Legendre polynomial (1) of 4th degree or higher and 10th degree or lower can be used. Specifically, z(x, y) can be fitted with a Legendre polynomial (1) having a maximum degree of 4th, 6th, 8th or 10th. At least one term selected from the 4th, 6th, 8th and 10th terms of the Legendre polynomial (1) obtained by fitting, and at least one of k being 2, 4, 6, 8 or 10 is selected, and a predetermined coefficient a ｋｌ can be evaluated whether it is within a predetermined range.

[0078] The predetermined coefficient a ｋｌ is specifically as follows. In the 4th-degree term, P ４ (x)P ０ (y)'s coefficient a ４０ , and P ２ (x)P ２ (y)'s coefficient a ２２ is at least one selected from. In the 6th-degree term, P ６ (x)P ０ (y)'s coefficient a ６０ , P ４ (x)P ２ (y)'s coefficient a ４２ , and P ２ (x)P ４ (y)'s coefficient a ２４ is at least one selected from. In the 8th-degree term, P ８(x) P ０ Coefficient a of (y) ８０ , P ６ (x) P ２ Coefficient a of (y) ６２ , P ４ (x) P ４ Coefficient a of (y) ４４ , and P ２ (x) P ６ Coefficient a of (y) ２６ It is at least one selected from the following. In the next term, P １０ (x) P ０ Coefficient a of (y) １００ , P ８ (x) P ２ Coefficient a of (y) ８２ , P ６ (x) P ４ Coefficient a of (y) ６４ , P ４ (x) P ６ Coefficient a of (y) ４６ , and P ２ (x) P ８ Coefficient a of (y) ２８ It is at least one selected from the following.

[0079] The surface height z(x,y) of the first inner region 46 can be measured using a known surface shape measuring device. Specifically, the entire second main surface of the conductive film-coated substrate 40 is measured using a surface shape measuring device, and the z(x,y) data of the first inner region 46 is fitted with a predetermined Legendre polynomial (1) to express the z(x,y) of the first inner region 46 in terms of the Legendre polynomial (1).

[0080] The above explanation states that one side of the first inner region 46 is L １ We have explained the case where the value is 104 mm, but this is not the only case. For example, even when the first inner region 46 is 104 mm × 132 mm, the 4th to 10th order terms P are explained in the same way as above. ｋ (x) P ｌ (y) (i.e., 4 ≤ k + l ≤ 10), where k + l is even and k is an even number greater than or equal to 2, and at least one coefficient a ｋｌBy keeping the absolute value of within a predetermined range, the desired overlay accuracy can be achieved during EUV lithography. When the first inner region 46 is 104 mm × 132 mm, the x-direction can be the direction with 104 mm as one side of the first inner region 46.

[0081] When the height z(x,y) of the surface of the first inner region 46 of the conductive film 42 on the second main surface of the conductive film substrate 40 is expressed by Legendre polynomial (1), it is preferable that the coefficients of terms of order higher than 10 are also smaller. However, the influence of the coefficients of terms of order higher than 10 on overlay accuracy is smaller than that of the coefficients of the 4th to 10th order terms. Therefore, in order to improve overlay accuracy, it is basically necessary to reduce the coefficients of the 4th to 10th order terms to a predetermined range.

[0082] The above explanation also applies to the second main surface of the substrate 1 before the conductive film 42 is formed. Therefore, when the surface shape of the first inner region 46, a rectangle with sides of 104 mm, with respect to the center of the second main surface, is expressed by Legendre polynomial (1), the 4th to 10th order terms P ｋ (x) P ｌ (y) where k+l is even and k is an even number greater than or equal to 2, and at least one coefficient a ｋｌ Since the absolute value of is within the same range as that of the conductive film-coated substrate 40 described above, the reflective mask 200 obtained by manufacturing using the substrate 1 can satisfy the desired overlay accuracy during EUV lithography.

[0083] The above explanation also applies to the surface (back surface) corresponding to the second main surface of the multilayer reflective substrate 90, which will be described later. Therefore, on the back surface of the multilayer reflective substrate 90, the 4th to 10th order terms P when the surface shape of the first inner region 46, a rectangle with sides of 104 mm based on the center of the second main surface, is expressed by Legendre polynomial (1) ｋ (x) P ｌ (y) where k+l is even and k is an even number greater than or equal to 2, and at least one coefficient a ｋｌSince the absolute value of is within the same range as that of the conductive film-coated substrate 40 described above, the reflective mask 200 obtained by manufacturing using the multilayer reflective film-coated substrate 90 can satisfy the desired overlay accuracy during EUV lithography.

[0084] The above explanation also applies to the surface (back surface) corresponding to the second main surface of the reflective mask blank 100, which will be described later. Therefore, on the back surface of the reflective mask blank 100, the 4th to 10th order terms P when the surface shape of the first inner region 46, a rectangle with sides of 104 mm relative to the center of the second main surface, is expressed by Legendre polynomial (1) ｋ (x) P ｌ (y) where k+l is even and k is an even number greater than or equal to 2, and at least one coefficient a ｋｌ Since the absolute value of is within the same range as that of the conductive film-coated substrate 40 described above, the reflective mask 200 obtained by manufacturing using the reflective mask blank 100 can satisfy the desired overlay accuracy during EUV lithography.

[0085] Furthermore, on the back surface of the reflective mask blank 100, the surface shape of the first inner region 46, a rectangle with sides of 104 mm relative to the center of the second main surface, is expressed by Legendre polynomial (1), and the 4th to 10th order terms P ｋ (x) P ｌ (y) where k+l is even and k is 2 or greater, all coefficients a ｋｌ Since the absolute value of is within the same range as in the case of the conductive film-coated substrate 40 described above, the reflective mask 200 obtained by manufacturing using the reflective mask blank 100 can further satisfy the desired overlay accuracy during EUV lithography.

[0086] In this embodiment, the conductive film-coated substrate 40 has a fourth-order term P such that when the surface shape of the first inner region 46 is expressed by Legendre polynomial (1), k + l is 4 and k is 4. ４ (x) P ０ Coefficient a of (y) ４０ It is preferable that the absolute value of the absolute value of is 2 nm or less. Furthermore, the fourth-order term P is such that k + l is 4 and k is 0. ０ (x) P４ Coefficient a of (y) ０４ The absolute value of is preferably 2 nm or less. The y-direction is perpendicular to the x-direction. This further reduces the in-plane distortion (IPD) in the y-direction. The coefficient a in the x-direction as described above. ４０ and coefficient a in the y direction ０４ The absolute value of is preferably 2.0 nm or less, more preferably 1.5 nm or less, even more preferably 1.0 nm or less, and particularly preferably 0.5 nm or less. ４ (x) P ０ Coefficient a of (y) ４０ , and P ０ (x) P ４ Coefficient a of (y) ０４ The absolute value of is greater than 0 nm. The coefficient a of the conductive film-coated substrate 40 of this embodiment. ４０ and coefficient a ０４ If the value is within a predetermined range, manufacturing a reflective mask 200 using this conductive film-coated substrate 40 makes it more certain that the reflective mask 200 will meet the desired overlay accuracy during EUV lithography.

[0087] The conductive film-coated substrate 40 of this embodiment has the above coefficient a ４０ and coefficient a ０４ Preferably, the absolute value of at least one coefficient selected from is 1 nm or less, and coefficient a ４０ and coefficient a ０４ It is more preferable that the absolute values ​​of both are 1 nm or less. The coefficient a of the conductive film-coated substrate 40 of this embodiment ４０ and coefficient a ０４ If the value is within a predetermined range, manufacturing a reflective mask 200 using this conductive film-coated substrate 40 makes it even more certain that the reflective mask 200 will meet the desired overlay accuracy during EUV lithography.

[0088] Furthermore, by setting the absolute value of the coefficient of the fifth-order term in the y-direction, which cannot be corrected by the EUV exposure apparatus 50, to a predetermined range, the in-plane distortion (IPD) in the y-direction can be reduced. Specifically, the fifth-order term P is such that k+l is 5 and k is 0. ０(x) P ５ Coefficient a of (y) ０５ The absolute value of is preferably 2.0 nm or less, more preferably 1.5 nm or less, even more preferably 1.0 nm or less, and particularly preferably 0.5 nm or less.

[0089] Furthermore, if the first inner region 46 is rectangular, the shorter side can be the x-direction and the longer side can be the y-direction. For example, if the first inner region 46 is 104 mm x 132 mm, the x-direction can be the direction of the 104 mm side of the first inner region 46, and the y-direction can be the direction of the 132 mm side of the first inner region 46.

[0090] In this embodiment, the conductive film-coated substrate 40 preferably has a flatness of 50 nm or less in the second inner region 48. As shown in Figure 8, in this specification, the "second inner region 48" refers to a region where one side is L relative to the center of the second main surface. ２ This is the area inside the rectangle of (mm). Therefore, the second inner area 48 also includes the first inner area 46. Side length L ２ is, L ２ = 142 mm. In this specification, "flatness" ("PV value") is the difference between the highest and lowest heights when the 0th, 1st, and 2nd order components are removed from all components of the surface of the conductive film 42. The flatness can be calculated by measuring the surface shape of the second inner region 48 which includes the first inner region 46 described above. Alternatively, the coefficient a described above can be calculated using the measurement results of the first inner region 46 included in the second inner region 48. ｋｌ It is possible to calculate this.

[0091] While various surface shape measuring devices such as white light interferometers, laser interferometers, laser displacement meters, ultrasonic displacement meters, and contact displacement meters can be used, it is preferable to use a white light interferometer (e.g., Zygo's NewView 6300) or a laser interferometer (e.g., Tropel's "UltraFlat 200").

[0092] <<Multilayer Reflective Film 2>> The substrate 90 with the multilayer reflective film (substrate 40 with conductive film) of this embodiment includes the multilayer reflective film 2 and the conductive film 42 described above, as shown in Figures 2 and 3. The multilayer reflective film 2 provides the function of reflecting EUV light in the reflective mask 200. The multilayer reflective film 2 is a multilayer film in which each layer, mainly composed of elements with different refractive indices, is periodically stacked.

[0093] Generally, the multilayer reflective film 2 is a multilayer film in which thin films of light elements or compounds thereof, which are high refractive index materials (high refractive index layers), and thin films of heavy elements or compounds thereof, which are low refractive index materials (low refractive index layers), are alternately stacked for about 40 to 60 periods.

[0094] The multilayer film used as the multilayer reflective film 2 can have a structure in which a high refractive index layer / low refractive index layer stacked in this order from the substrate 1 side is stacked for multiple periods, with one period being the stacked high refractive index layer / low refractive index layer structure. Alternatively, the multilayer film can have a structure in which a low refractive index layer / high refractive index layer stacked in this order from the substrate 1 side is stacked for multiple periods, with one period being the stacked low refractive index layer / high refractive index layer structure. It is preferable that the outermost layer of the multilayer reflective film 2, that is, the surface layer of the multilayer reflective film 2 on the side opposite to the substrate 1 side, is a high refractive index layer. In the above-described multilayer film, when a high refractive index layer / low refractive index layer stacked in this order from the substrate 1 side is stacked for multiple periods, the uppermost layer becomes a low refractive index layer. In this case, if the low refractive index layer constitutes the outermost surface of the multilayer reflective film 2, it will be easily oxidized, so the reflectivity of the reflective mask 200 will decrease. 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 2. On the other hand, in the above-mentioned multilayer film, if a low refractive index layer and a high refractive index layer are stacked in that order from the substrate 1 side, and multiple periods of stacking are performed with this low refractive index / high refractive index layer structure as one period, the uppermost layer will be the high refractive index layer. Therefore, in this case, it is not necessary to form any further high refractive index layers.

[0095] As the high refractive index layer, a layer containing silicon (Si) can be used. As the Si-containing material, in addition to elemental Si, a Si compound containing boron (B), carbon (C), nitrogen (N), oxygen (O), and / or hydrogen (H) can be used. By using a high refractive index layer containing Si, a reflective mask 200 with excellent EUV light reflectivity can be obtained. Furthermore, 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. In addition, boron (B), carbon (C), nitrogen (N), oxygen (O), and / or hydrogen (H) may be added to these elemental metals or alloys. In the multilayer reflective film substrate 90 of this embodiment, it is preferable that the low refractive index layer is a molybdenum (Mo) layer and the high refractive index layer is a silicon (Si) layer. For example, as the multilayer reflective film 2 for reflecting EUV light with a wavelength of 13 nm to 14 nm (for example, a wavelength of 13.5 nm), a Mo / Si periodic multilayer film in which Mo layers and Si layers are alternately stacked for about 40 to 60 periods can be preferably used. Furthermore, in the substrate 90 with the multilayer reflective film of this embodiment, it is preferable that the low refractive index layer is a ruthenium (Ru) layer and the high refractive index layer is a silicon (Si) layer. For example, as the multilayer reflective film 2 for reflecting EUV light with a wavelength of 13 nm to 14 nm (for example, a wavelength of 13.5 nm), a Ru / Si periodic multilayer film in which Ru layers and Si layers are alternately stacked for about 30 to 40 periods can be preferably used.

[0096] The reflectivity of the multilayer reflective film 2 on its own is usually 65% ​​or higher, with an upper limit of usually 73%. The film thickness and period of each constituent layer of the multilayer reflective film 2 can be appropriately selected depending on the exposure wavelength. Specifically, the film thickness and period of each constituent layer of the multilayer reflective film 2 can be selected to satisfy Bragg's law of reflection. In the multilayer reflective film 2, there are multiple high-refractive-index layers and multiple low-refractive-index layers, but the film thicknesses of the high-refractive-index layers or the low-refractive-index layers do not necessarily have to be the same.

[0097] The method for forming the multilayer reflective film 2 is known in the art. The multilayer reflective film 2 can be formed by depositing each layer, for example, by ion beam sputtering. In the case of the Mo / Si periodic multilayer film described above, for example, by ion beam sputtering or magnetron sputtering, first a Si film with a thickness of about 4 nm is deposited on the substrate 1 using a Si target, and then a Mo film with a thickness of about 3 nm is deposited using a Mo target. This constitutes one period, and 40 to 60 periods are stacked to form the multilayer reflective film 2 (the outermost layer is a Si film). Note that if 60 periods are used, the number of steps increases compared to 40 periods, but the reflectivity to EUV light can be increased.

[0098] <<Protective film 3>> As shown in Figure 3, it is preferable that the conductive film substrate 40 (multilayer reflective film substrate 90) of this embodiment has a protective film 3 on the multilayer reflective film 2.

[0099] To protect the multilayer reflective film 2 from dry etching and cleaning during the manufacturing process of the reflective mask 200 described later, a protective film 3 can be formed on the multilayer reflective film 2 or in contact with its surface. The protective film 3 also has the function of protecting the multilayer reflective film 2 when correcting black defects in the transfer pattern (absorber pattern 4a) using an electron beam (EB). By forming the protective film 3 on the multilayer reflective film 2, damage to the surface of the multilayer reflective film 2 during the manufacturing of the reflective mask 200 can be suppressed. As a result, the reflectivity characteristics of the multilayer reflective film 2 to EUV light are improved.

[0100] The protective film 3 is formed from a material containing Ru as the main component, for example. Examples of materials containing Ru as the main component include elemental Ru metal, Ru alloys containing Ru and at least one metal selected from titanium (Ti), niobium (Nb), rhodium (Rh), molybdenum (Mo), zirconium (Zr), yttrium (Y), boron (B), lanthanum (La), cobalt (Co), and rhenium (Re), and materials further containing nitrogen. The protective film 3 is formed from a material containing rhodium (Rh) as the main component, for example. Materials containing Rh as the main component include elemental Rh metal, Rh alloys containing Rh and at least one metal selected from titanium (Ti), niobium (Nb), ruthenium (Ru), molybdenum (Mo), zirconium (Zr), yttrium (Y), boron (B), lanthanum (La), cobalt (Co), and rhenium (Re), and materials further containing nitrogen.

[0101] In this embodiment, the protective film 3 of the multilayer reflective substrate 90 preferably includes at least one selected from Ru and Rh. In the multilayer reflective substrate 90 of this embodiment, the protective film 3 includes at least one selected from Ru and Rh, thereby providing more reliable protection for the multilayer reflective film 2.

[0102] The Ru content of the Ru alloy used in the protective film 3 is 50 atomic% or more and less than 100 atomic%, preferably 80 atomic% or more and less than 100 atomic%, and more preferably 95 atomic% or more and less than 100 atomic%. The Rh content of the Rh alloy used in the protective film 3 is 50 atomic% or more and less than 100 atomic%, preferably 80 atomic% or more and less than 100 atomic%, and more preferably 95 atomic% or more and less than 100 atomic%. In this case, the protective film 3 can combine sufficient reflectivity of EUV light with functions such as resistance to mask washing, etching stopper function when the absorber film 4 is etched, and prevention of changes in the multilayer reflective film 2 over time.

[0103] The thickness of the protective film 3 is not particularly limited as long as it can perform its function as a protective film 3. From the viewpoint of EUV light reflectance, the thickness of the protective film 3 is preferably 1.0 nm to 8.0 nm, more preferably 1.5 nm to 6.0 nm.

[0104] The protective film 3 may be a single layer or a multilayer film consisting of multiple layers (for example, a lower protective film and an upper protective film). If the protective film 3 is a single layer, the number of steps in mask blank manufacturing can be reduced, improving production efficiency. If the protective film 3 is a multilayer film, the material and thickness of the upper protective film can be selected so that the upper absorber film has an excellent etching stopper function. In addition, the material and thickness of the lower protective film can be selected so that the lower protective film has good adhesion to the uppermost layer of the multilayer reflective film 2.

[0105] As for the method of forming the protective film 3, any known film formation method can be used without particular limitation. Specific examples of methods for forming the protective film 3 include magnetron sputtering methods such as ion beam sputtering, DC sputtering, and RF sputtering, vapor deposition (CVD), and vacuum deposition.

[0106] <Reflective Mask Blank 100> Next, the reflective mask blank 100 of this embodiment will be described.

[0107] Figures 4 and 5 show examples of schematic cross-sectional views of the reflective mask blank 100 of this embodiment. The reflective mask blank 100 may further have other thin films, such as a resist film 11, on top of the absorber film 4.

[0108] The reflective mask blank 100 of this embodiment includes a substrate 1 having a first main surface and a second main surface facing the first main surface, a conductive film 42 provided on the second main surface of the substrate 1, a multilayer reflective film 2 provided on the first main surface of the substrate 1, and an absorber film 4 provided on the multilayer reflective film 2. The second main surface (back surface) of the reflective mask blank 100 of this embodiment on which the conductive film 42 is formed is subjected to a predetermined coefficient a, similar to the second main surface of the conductive film-coated substrate 40 described above. ｋｌ The absolute value of is within a predetermined range. Furthermore, the second main surface (back surface) of the reflective mask blank 100 in this embodiment can have the same characteristics as the second main surface of the conductive film-coated substrate 40 described above.

[0109] <<Absorbing film 4>> The reflective mask blank 100 of this embodiment is provided with an absorbing film 4 on the multilayer reflective film 2 of the multilayer reflective film substrate 90 described above, or on a protective film 3 formed so as to be in contact with the surface of the multilayer reflective film 2.

[0110] In the reflective mask blank 100 of this embodiment, the absorber film 4 can absorb EUV light, so the reflective mask 200 (EUV mask) of this embodiment can be manufactured by patterning the absorber film 4 of the reflective mask blank 100. By using the reflective mask blank 100 of this embodiment, a reflective mask 200 can be obtained that can increase the light intensity (light quantity) of the exposure light on the material to be transferred.

[0111] The basic function of the absorber film 4 is to absorb EUV light. The absorber film 4 may be an absorber film 4 intended for absorbing EUV light, or it may be an absorber film 4 having a phase shift function that also takes into account the phase difference of EUV light. An absorber film 4 having a phase shift function absorbs EUV light and also reflects a portion of the EUV light to shift its phase. That is, in a reflective mask 200 patterned with an absorber film 4 having a phase shift function, in the area where the absorber film 4 is formed, it absorbs EUV light to reduce its brightness while reflecting a portion of the light at a level that does not adversely affect pattern transfer. Also, in the area where the absorber film 4 is not formed (field area), EUV light is reflected by the multilayer reflective film 2 (via the protective film 3 if present). Therefore, a desired phase difference is created between the light reflected from the absorber film 4 having a phase shift function and the light reflected from the field area. The absorber film 4, which has a phase shift function, is preferably formed such that the phase difference between the reflected light from the absorber film 4 and the reflected light from the multilayer reflective film 2 is between 170 and 260 degrees. The light with the inverted phase difference interferes with each other at the pattern edge, improving the image contrast of the projected optical image. This improvement in image contrast leads to an increase in resolution, and various exposure-related margins such as exposure margin and focus margin can be increased.

[0112] The absorber film 4 may be a single layer or a multilayer film consisting of multiple layers (for example, a lower absorber film and an upper absorber film). When the absorber film 4 is a single layer, the number of steps in mask blank manufacturing can be reduced, improving production efficiency. When the absorber film 4 is a multilayer film, the optical constants and thickness of the upper absorber film can be appropriately set so that it acts as an anti-reflective film during mask pattern defect inspection using light. This improves the inspection sensitivity during mask pattern defect inspection using light. Furthermore, if a film with oxygen (O) and nitrogen (N), etc., added to the upper absorber film improves oxidation resistance, the stability over time is improved. In this way, by making the absorber film 4 a multilayer film, it becomes possible to add various functions to the absorber film 4. When the absorber film 4 has a phase shift function, the range of adjustment on the optical surface can be increased by making it a multilayer film, making it easier to obtain the desired reflectance.

[0113] The material for the absorber film 4 is not particularly limited, as long as it has the function of absorbing EUV light, can be processed by etching or the like (preferably etchable by dry etching with chlorine (Cl)-based gas and / or fluorine (F)-based gas), and has a high etching selectivity ratio with respect to the protective film 3. As materials having such functions, it is preferable to use at least one metal selected from palladium (Pd), silver (Ag), platinum (Pt), gold (Au), iridium (Ir), tungsten (W), chromium (Cr), cobalt (Co), manganese (Mn), tin (Sn), tantalum (Ta), vanadium (V), nickel (Ni), hafnium (Hf), iron (Fe), copper (Cu), tellurium (Te), zinc (Zn), magnesium (Mg), germanium (Ge), aluminum (Al), rhodium (Rh), ruthenium (Ru), molybdenum (Mo), niobium (Nb), titanium (Ti), zirconium (Zr), yttrium (Y), and silicon (Si), alloys containing two or more metals, or compounds thereof. The compounds may contain oxygen (O), nitrogen (N), carbon (C), and / or boron (B) in addition to the above metals or alloys.

[0114] The absorber film 4 can be formed by magnetron sputtering methods such as DC sputtering and RF sputtering. For example, an absorber film 4 made of a tantalum compound can be deposited by a reactive sputtering method using a target containing tantalum and boron, and argon gas doped with oxygen or nitrogen.

[0115] Furthermore, from the viewpoint of smoothness and flatness, the crystalline state of the absorber film 4 is preferably amorphous or microcrystalline. If the surface of the absorber film 4 is not smooth or flat, the edge roughness of the absorber pattern 4a will increase, and the dimensional accuracy of the pattern may deteriorate. The preferred surface roughness of the absorber film 4 is 0.5 nm or less in root mean square roughness (Rms), more preferably 0.4 nm or less, and even more preferably 0.3 nm or less.

[0116] <<Etching Mask Film 6>> As shown in Figure 5, the reflective mask blank 100 of this embodiment may have an etching mask film 6 on top of the absorber film 4. As the material for the etching mask film 6, it is preferable to use a material that has a high etching selectivity ratio of the absorber film 4 to the etching mask film 6 (etching rate of the absorber film 4 / etching rate of the etching mask film 6). The etching selectivity ratio of the absorber film 4 to the etching mask film 6 is preferably 1.5 or higher, and more preferably 3 or higher.

[0117] In this embodiment, it is preferable that the reflective mask blank 100 has an etching mask film 6 on top of the absorber film 4.

[0118] It is preferable to use chromium or a chromium compound as the material for the etching mask film 6. Examples of chromium compounds include materials containing Cr and at least one element selected from N, O, C, and H. It is more preferable that the etching mask film 6 contains CrN, CrO, CrC, CrON, CrOC, CrCN, or CrOCN, and even more preferable that it is a CrO-based film (CrO film, CrON film, CrOC film, or CrOCN film) containing chromium and oxygen.

[0119] It is preferable to use tantalum or a tantalum compound as the material for the etching mask film 6. Examples of tantalum compounds include materials containing Ta and at least one element selected from N, O, B, and H. It is more preferable that the etching mask film 6 contains TaN, TaO, TaON, TaBN, TaBO, or TaBON.

[0120] It is preferable to use silicon or a silicon compound as the material for the etching mask film 6. Examples of silicon compounds include materials containing Si and at least one element selected from N, O, C, and H, as well as metallic silicon (metallic silicide) and metallic silicon compounds (metallic silicide compounds) that contain metal in silicon and silicon compounds. Examples of metallic silicon compounds include materials containing a metal, Si, and at least one element selected from N, O, C, and H.

[0121] The thickness of the etching mask film 6 is preferably 3 nm or more in order to accurately form a pattern on the absorber film 4. Furthermore, the thickness of the etching mask film 6 is preferably 15 nm or less in order to reduce the thickness of the resist film 11.

[0122] <<Method for manufacturing the reflective mask blank 100>> The method for manufacturing the reflective mask blank 100 is as follows.

[0123] First, the substrate 1 described above is prepared. Next, the conductive film 42 described above is formed on the second main surface of the substrate 1. Next, the multilayer reflective film 2 described above is formed on the first main surface of the substrate 1. Next, the absorber film 4 described above is formed on the multilayer reflective film 2. In this way, the reflective mask blank 100 of this embodiment can be manufactured. Note that the formation of the conductive film 42 does not necessarily have to be done before forming the multilayer reflective film 2. The conductive film 42 described above can be formed on the second main surface of the substrate 1 after the multilayer reflective film 2 is formed or after the absorber film 4 is formed.

[0124] When manufacturing the reflective mask blank 100 of this embodiment, the protective film 3 described above can be formed on the multilayer reflective film 2 before forming the absorber film 4. Alternatively, the etching mask film 6 described above can be formed on the absorber film 4 after it has been formed.

[0125] <Reflective Mask 200> As shown in Figure 6D, the reflective mask 200 of this embodiment includes an absorber pattern 4a obtained by patterning the absorber film 4 of the reflective mask blank 100 described above. That is, the reflective mask 200 of this embodiment has an absorber pattern 4a on the multilayer reflective film substrate 90 described above.

[0126] In other words, the reflective mask 200 of this embodiment includes a substrate 1 having a first main surface and a second main surface facing the first main surface, a conductive film 42 provided on the second main surface of the substrate 1, a multilayer reflective film 2 provided on the first main surface of the substrate 1, and an absorber film 4 (absorber pattern 4a) provided on the multilayer reflective film 2 and on which a transfer pattern is formed. The second main surface (back surface) of the reflective mask 200 of this embodiment on which the conductive film 42 is formed has a predetermined coefficient a, similar to the second main surface of the conductive film-coated substrate 40 described above. ｋｌ The absolute value of is within a predetermined range. Furthermore, the second main surface (back surface) of the reflective mask 200 of this embodiment can have the same characteristics as the second main surface of the conductive film-coated substrate 40 described above.

[0127] The reflective mask 200 of this embodiment may have a protective film 3 on top of the multilayer reflective film 2. The protective film 3 is placed between the multilayer reflective film 2 and the absorber pattern 4a.

[0128] Figures 6A to 6D are schematic diagrams showing an example of a method for manufacturing the reflective mask 200. The reflective mask 200 of this embodiment can be manufactured using the reflective mask blank 100 of this embodiment described above. An example of a method for manufacturing the reflective mask 200 will be described below.

[0129] First, a reflective mask blank 100 is prepared, comprising a substrate 1, a multilayer reflective film 2 formed on the first main surface of the substrate 1, a protective film 3 formed on the multilayer reflective film 2, an absorber film 4 formed on the protective film 3, and a conductive film 42 formed on the second main surface of the substrate 1. Next, a resist film 11 is formed on the absorber film 4 to obtain a reflective mask blank 100 with a resist film 11 (Figure 6A). A pattern is drawn on the resist film 11 using an electron beam lithography apparatus, and then a resist pattern 11a is formed by a development and rinsing process (Figure 6B).

[0130] The absorber film 4 is dry-etched using the resist pattern 11a as a mask. As a result, the parts of the absorber film 4 not covered by the resist pattern 11a are etched, and the absorber pattern 4a is formed (Figure 6C).

[0131] For example, a fluorine-based gas and / or a chlorine-based gas can be used as the etching gas for the absorber film 4. ４ CHF ３ , C ２ F ６ , C ３ F ６ , C ４ F ６ , C ４ F ８ ,CH ２ F ２ ,CH ３ F, C ３ F ８ SF ６ , and F ２ The following can be used. As for chlorine-based gases, Cl ２ SiCl ４ , CHCl ３ , CCl ４ , and BCl ３ The following can be used. Also, fluorine-based gas and / or chlorine-based gas, O ２ A mixed gas containing these in predetermined proportions can be used. These etching gases may, if necessary, further contain an inert gas such as He and / or Ar.

[0132] After the absorbent pattern 4a is formed, the resist pattern 11a is removed with a resist stripping solution. After removing the resist pattern 11a, the reflective mask 200 of this embodiment can be obtained by going through a wet cleaning process using an acidic or alkaline aqueous solution (Figure 6D).

[0133] Furthermore, when using a reflective mask blank 100 in which an etching mask film 6 is formed on an absorber film 4, an additional step is added: first, a pattern (etching mask pattern) is formed on the etching mask film 6 using the resist pattern 11a as a mask, and then a pattern is formed on the absorber film 4 using the etching mask pattern as a mask.

[0134] The reflective mask 200 obtained in this manner has a structure in which a multilayer reflective film 2, a protective film 3, and an absorber pattern 4a are laminated on the first main surface of the substrate 1. In addition, a conductive film 42 is placed on the second main surface of the substrate 1 of the reflective mask 200.

[0135] The areas (openings) where the multilayer reflective film 2 (including the protective film 3) is exposed have the function of reflecting EUV light. The areas where the multilayer reflective film 2 (including the protective film 3) is covered by the absorber pattern 4a have the function of absorbing EUV light. The reflective mask 200 of this embodiment can satisfy the desired overlay accuracy during EUV lithography. Therefore, by using the reflective mask 200 of this embodiment, finer patterns can be transferred to the material to be transferred.

[0136] <Method for Manufacturing Semiconductor Device> The method for manufacturing a semiconductor device according to this embodiment includes a step of forming a transfer pattern on a transfer object by performing a lithography process using an exposure apparatus (EUV exposure apparatus 50) with the reflective mask 200 described above.

[0137] EUV lithography using the reflective mask 200 of this embodiment can form a transfer pattern on a semiconductor substrate 60 (the object to be transferred). This transfer pattern has the shape of the pattern of the reflective mask 200 transferred onto it. By forming a transfer pattern on the semiconductor substrate 60 with the reflective mask 200, a semiconductor device can be manufactured.

[0138] According to this embodiment, a semiconductor device can be manufactured using a reflective mask 200 that can satisfy the desired overlay accuracy during EUV lithography. Therefore, by using the reflective mask 200 of this embodiment, semiconductor devices can be made higher density and more precise.

[0139] Using Figure 7, we will explain a method for transferring a pattern onto a resist-coated semiconductor substrate 60 using EUV light.

[0140] Figure 7 shows a schematic configuration of an EUV exposure apparatus 50, which is a device for transferring a transfer pattern to a resist film formed on a semiconductor substrate 60. The EUV exposure apparatus 50 consists of an EUV light generation unit 51, an irradiation optical system 56, a reticle stage 58, a projection optical system 57, and a wafer stage 59, all precisely arranged along the optical path axis of the EUV light. The container of the EUV exposure apparatus 50 is filled with hydrogen gas.

[0141] The EUV light generation unit 51 includes a laser light source 52, a tin droplet generation unit 53, a capture unit 54, and a collector 55. When a high-power carbon dioxide laser from the laser light source 52 is irradiated onto tin droplets emitted from the tin droplet generation unit 53, the tin in droplet state is converted into plasma, generating EUV light. The generated EUV light is focused by the collector 55 and incident on a reflective mask 200 set on the reticle stage 58 via the irradiation optical system 56. The EUV light generation unit 51 generates, for example, EUV light with a wavelength of 13.53 nm.

[0142] The EUV light reflected by the reflective mask 200 is reduced to approximately 1 / 4 of its original size by the projection optical system 57 and projected onto the semiconductor substrate 60 (transfer substrate). This transfers a given circuit pattern onto the resist film on the semiconductor substrate 60. By developing the exposed resist film, a resist pattern can be formed on the semiconductor substrate 60. By etching the semiconductor substrate 60 using the resist pattern as a mask, an integrated circuit pattern can be formed on the semiconductor substrate 60. A semiconductor device is manufactured through these processes and other necessary steps.

[0143] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0144] The following describes examples and comparative examples relating to the conductive film-coated substrate 40, reflective mask blank 100, and reflective mask 200 of this embodiment.

[0145] <Substrate 1> Here, thirteen mask blank substrates were manufactured by carrying out the mask blank manufacturing method of the present invention. First, SiO ２ -TiO ２ Thirteen glass substrates (152.4 mm x 152.4 mm, 6.35 mm thick) were cut from a glass ingot. The edges of these glass substrates were chamfered and ground, and then rough polishing and precision polishing were performed using a polishing solution containing cerium oxide abrasive particles. After that, these thirteen glass substrates were set on a carrier of a double-sided polishing machine and ultra-precision polishing was performed under the following conditions: Polishing pad: soft polisher (suede type) Polishing solution: colloidal silica abrasive particles (average particle size 100 nm) and water Processing pressure: 50-100 g / cm² ２ Processing time: 60 minutes

[0146] After ultra-precision polishing was completed, each glass substrate was immersed in a dilute hydrofluoric acid solution to remove colloidal silica abrasive particles. Subsequently, the main surface and edges of each glass substrate were scrubbed, followed by spin cleaning with pure water and spin drying.

[0147] Next, considering the shape of the substrate 1 after the deposition of the multilayer reflective film 2, protective film 3, absorber film 4, and conductive film 42, the processing conditions (required removal amount, etc.) for local processing to be performed on the first main surface (front) and second main surface (back) of the glass substrate were calculated. Based on the calculated processing conditions, local processing was performed on the front and back main surfaces of each glass substrate using a local processing device. The local processing device used at this time was a device that used the magneto-viscoelastic finishing (MRF) method. The magneto-viscoelastic fluid used at this time contained iron components, and the polishing slurry was an alkaline aqueous solution + abrasive (approximately 2% by weight), with cerium oxide used as the abrasive. After local processing, each glass substrate was immersed in a washing tank containing an approximately 10% hydrochloric acid aqueous solution (at a temperature of approximately 25°C) for about 10 minutes, followed by rinsing with pure water and drying with isopropyl alcohol (IPA).

[0148] Furthermore, the first and second main surfaces of each glass substrate were polished on both sides using a double-sided polishing apparatus under polishing conditions that maintained or improved the surface shape of the first main surface of substrate 1. This finish polishing was performed under the following polishing conditions: Processing fluid: Alkaline aqueous solution (NaOH) + polishing agent (concentration: approximately 2% by weight) Polishing agent: Colloidal silica, average particle size: approximately 70 nm Polishing platen rotation speed: approximately 1 to 50 rpm Processing pressure: approximately 0.1 to 10 kPa Polishing time: approximately 1 to 10 minutes

[0149] Subsequently, each glass substrate was washed with an alkaline aqueous solution (NaOH). In this manner, substrate 1 of the examples and comparative examples was manufactured.

[0150] <Reflective mask blank 100> Next, a multilayer reflective film 2 was formed on the first main surface of the substrate 1.

[0151] The multilayer reflective film 2 formed on the first main surface of the substrate 1 was a periodic multilayer reflective film composed of molybdenum (Mo) and silicon (Si) to be suitable for EUV light with a wavelength of 13.5 nm. The multilayer reflective film 2 was formed by alternately stacking Mo layers and Si layers on the substrate 1 using an ion beam sputtering method in a krypton (Kr) gas atmosphere with a Mo target and a Si target. First, a Si film was deposited to a thickness of 4.2 nm, followed by a Mo film to a thickness of 2.8 nm. This constituted one period, and 40 periods were stacked in the same manner. Finally, a Si film was deposited to a thickness of 4.0 nm to form the multilayer reflective film 2.

[0152] Next, using a RuNb target (Ru: 80 atomic%, Nb: 20 atomic%), a protective film 3 made of RuNb was formed on the multilayer reflective film 2 by DC magnetron sputtering in an Ar gas atmosphere. The thickness of the protective film 3 was 2.5 nm.

[0153] Next, an absorber film 4 was formed on the protective film 3. Specifically, the absorber film 4, consisting of a laminated film of TaBN (thickness 56 nm) and TaBO (thickness 14 nm), was formed by DC magnetron sputtering. The TaBN film was formed using a TaB target with Ar gas and N ２ The film was formed by reactive sputtering in a gas mixture atmosphere. The TaBO film was formed using a TaB target with Ar gas and O ２ It was formed by reactive sputtering in a gas mixture atmosphere.

[0154] Next, a conductive film 42 of TaB film was formed on the second main surface of substrate 1. The TaB film was formed using a TaB target with Ar gas and N ２ The film was deposited to a thickness of 70 nm by reactive sputtering in a gas mixture atmosphere.

[0155] As described above, the reflective mask blanks 100 of the examples and comparative examples were manufactured. The reflective mask blank 100 has a conductive film 42 on the second main surface of the substrate 1, and is therefore a conductive film-coated substrate 40.

[0156] In each reflective mask blank 100, the surface shape of the conductive film 42 after deposition was measured using a surface shape measuring device (UltraFlat200M, manufactured by Corning Tropel). The fourth-order term P was obtained when the surface shape of the first inner region 46, a rectangle with sides of 104 mm relative to the center of the substrate 1, was fitted with the Legendre polynomial (1). ４ (x) P ０ Coefficient a of (y) ４０ and P ０ (x) P ４ Coefficient a of (y) ０４ Each was calculated. The results are shown in Table 1. In Table 1, "+" represents a ４０ P ４ (x) P ０ (y) and a ０４ P ０ (x) P ４ (y) is convex toward the opposite side of substrate 1 in the vicinity of x=0 and y=0, respectively, and "-" is a ４０ P ４ (x) P ０ (y) and a ０４ P ０ (x) P ４ This shows that (y) is convex towards the substrate 1 side in the vicinity of x=0 and y=0, respectively.

[0157] Furthermore, the PV value (flatness) was calculated for each of the second inner regions 48 of a rectangle with sides of 142 mm, with the center of substrate 1 as the reference point. Table 1 shows the PV values.

[0158] Table 1 also shows the results of calculating the in-plane distortion (IPD) of each reflective mask blank 100 using the above-described formula (2). Coefficient a of Examples 1-1 to 1-11 ４０ The absolute value was 2 nm or less, and the IPD in the x-direction could be made 0.17 nm or less. In contrast, the coefficient a of Comparative Examples 1-1 and 1-2 ４０ The absolute value of was greater than 2 nm, and the IPD in the x-direction was greater than 0.17 nm. Note that the coefficient a of Examples 1-1 to 1-11 and Comparative Examples 1-1 and 1-2 ０４ From the results, the coefficient a ０４ It can be understood that the absolute value of does not affect the IPD in the x direction. Furthermore, from the results of the examples and comparative examples, the coefficient a４０ Even if the values ​​are similar, the PV values ​​differ, and the coefficient a ４０ It can be understood that there is no correlation between this and the PV value.

[0159] <Reflective Mask 200> Next, the reflective mask 200 of the example was manufactured using the reflective mask blank 100 of the example. The manufacturing of the reflective mask 200 will be explained with reference to Figures 6A to 6D.

[0160] First, as shown in Figure 6A, a resist film 11 was formed on the absorber film 4 of the reflective mask blank 100. Then, a desired pattern such as a circuit pattern was drawn (exposed) on this resist film 11, and a predetermined resist pattern 11a was formed by further development and rinsing (Figure 6B). Next, using the resist pattern 11a as a mask, the absorber film 4 (TaBN film) was subjected to Cl ２ An absorber pattern 4a was formed by dry etching using gas (Figure 6C). Subsequently, the resist pattern 11a was removed (Figure 6D).

[0161] Finally, wet washing with pure water (DIW) was performed to manufacture the reflective mask 200 of the example.

[0162] In each reflective mask 200, the surface shape of the conductive film 42 was measured using a surface shape measuring device (UltraFlat200M manufactured by Corning Tropel), and the fourth-order term P was obtained when the surface shape of the first inner region 46, a rectangle with sides of 104 mm with respect to the center of the substrate 1, was fitted with the Legendre polynomial (1). ４ (x) P ０ Coefficient a of (y) ４０ and P ０ (x) P ４ Coefficient a of (y) ０４ When we calculated each of these values, we confirmed that they were approximately the same as the values ​​shown in Table 1.

[0163]

[0164] In Examples 2-1 to 2-8 and Comparative Examples 2-1 and 2-2, in each of the eight reflective mask blanks 100 selected from Examples 1-1 to 1-11 and Comparative Examples 1-1 and 1-2, the sixth-order term P was obtained when the surface shape of the first inner region 46, a rectangle with sides of 104 mm relative to the center of the substrate 1, was fitted with the Legendre polynomial (1). ４ (x) P ２ Coefficient a of (y) ４２ The PV value and IPD in the x-direction were calculated, respectively. The results are shown in Table 2.

[0165] In Examples 3-1 to 3-7 and Comparative Examples 3-1 and 3-2, in each of the seven reflective mask blanks 100 selected from Examples 1-1 to 1-11 and Comparative Examples 1-1 and 1-2, the sixth-order term P was obtained when the surface shape of the first inner region 46, a rectangle with sides of 104 mm relative to the center of the substrate 1, was fitted with the Legendre polynomial (1). ２ (x) P ４ Coefficient a of (y) ２４ The PV value and IPD in the x-direction were calculated, respectively. The results are shown in Table 3.

[0166] In Examples 4-1 to 4-7 and Comparative Examples 4-1 and 4-2, in each of the seven reflective mask blanks 100 selected from Examples 1-1 to 1-11 and Comparative Examples 1-1 and 1-2, the eighth-order term P was obtained when the surface shape of the first inner region 46, a rectangle with sides of 104 mm relative to the center of the substrate 1, was fitted with the Legendre polynomial (1). ６ (x) P ２ Coefficient a of (y) ６２ The PV value and IPD in the x-direction were calculated, respectively. The results are shown in Table 4.

[0167] In Examples 5-1 to 5-6 and Comparative Examples 5-1 and 5-2, in each of the six reflective mask blanks 100 selected from Examples 1-1 to 1-11 and Comparative Examples 1-1 and 1-2, the eighth-order term P was obtained when the surface shape of the first inner region 46, a rectangle with sides of 104 mm relative to the center of the substrate 1, was fitted with the Legendre polynomial (1). ４ (x) P ４ Coefficient a of (y) ４４The PV value and IPD in the x-direction were calculated, respectively. The results are shown in Table 5.

[0168] Coefficient a of the examples in Tables 2 to 5 ４２ coefficient a ２４ coefficient a ６２ and coefficient a ４４ The absolute values ​​of each were 2 nm or less, and the IPD in the x-direction could be made 0.17 nm or less. In contrast, the coefficient a of the comparative examples in Tables 2 to 5 ４２ coefficient a ２４ coefficient a ６２ and coefficient a ４４ The absolute values ​​of each were greater than 2 nm, and the IPD in the x-direction was greater than 0.17 nm. Furthermore, from the results of the examples and comparative examples, the coefficient a ４２ coefficient a ２４ coefficient a ６２ or coefficient a ４４ Even if the values ​​are similar, the PV values ​​differ, and the coefficient a ４２ coefficient a ２４ coefficient a ６２ or coefficient a ４４ It can be understood that there is no correlation between this and the PV value.

[0169]

[0170]

[0171]

[0172]

[0173] Furthermore, the absolute values ​​of the coefficients for terms of order 10 or higher and the IPD were calculated, but no strong correlation was found between them.

[0174] Next, another 10 reflective mask blanks 100 were manufactured using the same manufacturing method as the 13 reflective mask blanks 100 described above.

[0175] In each reflective mask blank 100, the surface shape of the conductive film 42 after deposition was measured using a surface shape measuring device (UltraFlat200M, manufactured by Corning Tropel). The sixth-order term P was obtained when the surface shape of the first inner region 46, a rectangle with sides of 104 mm relative to the center of the substrate 1, was fitted with the Legendre polynomial (1). ４ (x) P ２ Coefficient a of (y) ４２ and the fifth term P ０ (x) P ５ Coefficient a of (y) ０５ These values ​​were calculated accordingly. Similarly, the PV value, IPD in the x-direction, and IPD in the y-direction were also calculated. The results are shown in Table 6.

[0176] As shown in Table 6, in Examples 6-1 to 6-5, the coefficient a ４２ and coefficient a ０５ The absolute values ​​of each were 2 nm or less, and the IPD in both the x and y directions could be made 0.17 nm or less. In addition, in Examples 6-6 to 6-8, the coefficient a ４２ The absolute values ​​of each were 2 nm or less, and the IPD in the x direction was 0.17 nm or less, but the coefficient a ０５ The absolute values ​​of each were greater than 2 nm, and the IPD in the y direction was greater than 0.17 nm. In Comparative Example 6-1, the coefficient a ４２ The absolute value of was greater than 2 nm, and the IPD in the x-direction was greater than 0.17 nm, but the coefficient a ０５ The absolute value of was 2 nm or less, and the IPD in the y direction was 0.17 nm or less. In Comparative Example 6-2, the coefficient a ４２ and coefficient a ０５ The absolute values ​​of each were greater than 2 nm, and the IPD in both the x and y directions was greater than 0.17 nm. As a result, the coefficient a of the fifth-order term in the y direction ０５ We confirmed that by setting the absolute value of to 2 nm or less, the IPD in the y-direction can also be reduced.

[0177]

[0178] 1 Substrate 2 Multilayer reflective film 3 Protective film 4 Absorber film 4a Absorber pattern 6 Etching mask film 11 Resist film 11a Resist pattern 40 Conductive film substrate 42 Conductive film 46 First inner region 48 Second inner region 50 EUV exposure apparatus 51 EUV light generation unit 52 Laser light source 53 Tin droplet generation unit 54 Capture unit 55 Collector 56 Irradiation optical system 57 Projection optical system 58 Reticle stage 59 Wafer stage 60 Semiconductor substrate 90 Multilayer reflective film substrate 100 Reflective mask blank 200 Reflective mask

Claims

A conductive film-coated substrate having a substrate having a first main surface and a second main surface facing the first main surface, and a conductive film provided on the second main surface, When the surface shape of the first inner region of a rectangle with sides of 104 mm, with respect to the center of the second main surface, is expressed by Legendre polynomial (1), the coefficient a of at least one term selected from among the terms satisfying 4 ≤ k + l ≤ 10, k + l is even, and k is an even number of 2 or more is ｋｌ A conductive film-coated substrate characterized by having an absolute value of 2 nm or less. x: Position in a predetermined direction within the first inner region y: Position within the first inner region in a direction perpendicular to the x direction. k and l: Each is a non-negative integer. N １ =10 N ２ =N １ -k The term P of degree 4 is such that k + l is 4 and k is 4. ４ (x) P ０ Coefficient a of (y) ４０ A conductive film-coated substrate according to claim 1, characterized in that the absolute value of is 2 nm or less. 　 Furthermore, for the fourth-order term P where k + l = 4 and k = 0 ０ P(x)P ４ (y), the absolute value of the coefficient a ０４ is 2nm or less. The substrate with a conductive film according to claim 1, characterized by this. 　 Furthermore, the 5th-degree term P is defined as such that k + l is 5 and k is 0. ０ (x) P ５ Coefficient a of (y) ０５ A conductive film-coated substrate according to any one of claims 1 to 3, characterized in that the absolute value of is 2 nm or less. 　 The flatness is 50 nm or less. The conductive film substrate according to any one of claims 1 to 3, characterized in that the flatness is the difference between the highest and lowest heights when the zeroth, primary, and secondary components are removed in a second inner region of a rectangle with sides of 142 mm, with respect to the center of the second primary surface, on the surface of the conductive film. 　 A conductive film substrate according to any one of claims 1 to 3, characterized in that the conductive film contains at least one element selected from tantalum (Ta) and chromium (Cr). 　 A substrate having a first main surface and a second main surface facing the first main surface, A conductive film provided on the second main surface of the substrate, A multilayer reflective film provided on the first main surface of the substrate, A reflective mask blank having an absorbent film provided on the multilayer reflective film, When the surface shape of the first inner region of a rectangle with sides of 104 mm, with respect to the center of the second main surface, is expressed by Legendre polynomial (1), the coefficient a of at least one term selected from among the terms satisfying 4 ≤ k + l ≤ 10, k + l is even, and k is an even number of 2 or more is ｋｌ A reflective mask blank characterized in that the absolute value of is 2 nm or less. x: Position in a predetermined direction within the first inner region y: Position within the first inner region in a direction perpendicular to the x direction. k and l: Each is a non-negative integer. N １ =10 N ２ =N １ -k The term P of degree 4 is such that k + l is 4 and k is 4. ４ (x) P ０ Coefficient a of (y) ４０ The reflective mask blank according to claim 7, characterized in that the absolute value of is 2 nm or less. 　 Furthermore, the quartic term P is defined as such that k + l is 4 and k is 0. ０ (x) P ４ Coefficient a of (y) ０４ The reflective mask blank according to claim 7, characterized in that the absolute value of is 2 nm or less. 　 Furthermore, the 5th-degree term P is defined as such that k + l is 5 and k is 0. ０ (x) P ５ Coefficient a of (y) ０５ A reflective mask blank according to any one of claims 7 to 9, characterized in that the absolute value of is 2 nm or less. 　 The flatness is 50 nm or less. The reflective mask blank according to any one of claims 7 to 9, characterized in that the flatness is the difference between the highest and lowest heights when the zeroth, primary, and secondary components are removed in a second inner region of a rectangle with sides of 142 mm, with respect to the center of the second primary surface, on the surface of the conductive film. 　 The reflective mask blank according to any one of claims 7 to 9, characterized in that the conductive film contains at least one element selected from tantalum (Ta) and chromium (Cr). 　 A substrate having a first main surface and a second main surface facing the first main surface, A conductive film provided on the second main surface of the substrate, A multilayer reflective film provided on the first main surface of the substrate, A reflective mask having an absorbent film on which a transfer pattern is formed, provided on the multilayer reflective film, When the surface shape of the first inner region of a rectangle with sides of 104 mm, with respect to the center of the second main surface, is expressed by Legendre polynomial (1), the coefficient a of at least one term selected from among the terms satisfying 4 ≤ k + l ≤ 10, k + l is even, and k is an even number of 2 or more is ｋｌ A reflective mask characterized by having an absolute value of 2 nm or less. x: Position in a predetermined direction within the first inner region y: Position within the first inner region in a direction perpendicular to the x direction. k and l: Each is a non-negative integer. N １ =10 N ２ =N １ -k The term P of degree 4 is such that k + l is 4 and k is 4. ４ (x) P ０ Coefficient a of (y) ４０ The reflective mask according to claim 13, characterized in that the absolute value of is 2 nm or less. 　 Furthermore, the quartic term P is defined as such that k + l is 4 and k is 0. ０ (x) P ４ Coefficient a of (y) ０４ The reflective mask according to claim 13, characterized in that the absolute value of is 2 nm or less. 　 Furthermore, the 5th-degree term P is defined as such that k + l is 5 and k is 0. ０ (x) P ５ Coefficient a of (y) ０５ A reflective mask according to any one of claims 13 to 15, characterized in that the absolute value of is 2 nm or less. 　 The flatness is 50 nm or less. The reflective mask according to any one of claims 13 to 15, characterized in that the flatness is the difference between the highest and lowest heights when the zeroth, primary, and secondary components are removed in a second inner region of a rectangle with sides of 142 mm, with respect to the center of the second primary surface, on the surface of the conductive film. 　 The reflective mask according to any one of claims 13 to 15, characterized in that the conductive film contains at least one element selected from tantalum (Ta) and chromium (Cr). 　 A method for manufacturing a semiconductor device, characterized by comprising the step of performing a lithography process using an exposure apparatus with a reflective mask according to any one of claims 13 to 15 to form a transfer pattern on a transfer object.

Images