Reflective mask blank, reflective mask, and method for manufacturing semiconductor device

Abstract

To provide a reflective mask blank in which dependence of optical characteristics of a thin film on a film thickness and density is minimized as much as possible.SOLUTION: A reflective mask blank comprises: a substrate; a multilayer reflection film formed on the substrate; and a thin film formed on the multilayer reflection film. A rate of a change in reflectance of the thin film for light with wavelengths from 13.525 nm to 13.550 nm is -12% / nm to 4% / nm, inclusive.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a reflective mask blank and a reflective mask used for the manufacture of semiconductor devices, and a method for manufacturing a semiconductor device using the reflective mask. [Background technology]

[0002] The types of light sources of exposure equipment in the manufacture of semiconductor devices have evolved with gradually shorter wavelengths, from g-line with a wavelength of 436 nm, i-line with a wavelength of 365 nm, KrF laser with a wavelength of 248 nm, and ArF laser with a wavelength of 193 nm. In order to realize finer pattern transfer, EUV lithography using EUV (Extreme Ultra Violet) light, which is an extreme ultraviolet ray with a wavelength of about 13.5 nm, has been proposed. In EUV lithography, a reflective mask is used because the difference in the absorption rate of EUV light between materials is small. As a reflective mask, for example, a multilayer reflective film that reflects exposure light is formed on a substrate, and a thin film (absorber film or phase shift film) that absorbs exposure light is formed in a pattern on the multilayer reflective film has been proposed. Light incident on a reflective mask mounted on an exposure machine (pattern transfer device) is absorbed in areas with a thin film pattern, and is reflected by the multilayer reflective film in areas without a thin film pattern, so that the light image is transferred onto a semiconductor substrate through a reflective optical system. When the thin film is a phase shift film, a portion of the exposure light incident on the phase shift film pattern is reflected with a phase difference from the light reflected by the multilayer reflective film (phase shift), thereby obtaining the desired contrast (resolution).

[0003] Techniques relating to such reflective masks for EUV lithography and mask blanks, which are originals for producing such masks, are disclosed in, for example, Patent Documents 1 and 2.

[0004] Patent Document 1 describes that in order to improve the transfer resolution by applying the principle of a halftone mask to EUV exposure, the material of a halftone film (phase shift film) made of a single layer is selected from a predetermined region in a diagram shown in a plane coordinate system with the refractive index and extinction coefficient as the coordinate axes. As a specific material for the single layer, TaMo (composition ratio 1:1) is described.

[0005] Patent Document 2 describes that in a half-tone EUV mask, in order to provide a degree of freedom in selectivity of reflectance and high cleaning resistance and to reduce the projection effect (shadowing effect), the material of the half-tone film is a compound of Ta and Ru, and its composition range is specified. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2006-228766 A [Patent Document 2] Patent No. 5233321 Summary of the Invention [Problem to be solved by the invention]

[0007] A reflective mask blank and a reflective mask obtained by forming a transfer pattern on a reflective mask blank are manufactured through a number of various processes, such as deposition of a multilayer thin film on a substrate, formation of a resist film, pattern etching, and cleaning. In such mask blank and mask manufacturing lines, high-level quality control is usually performed to minimize variations in manufacturing conditions between lots. However, no matter how thorough the quality control, a slight variation in manufacturing conditions or unexpected damage occurring during the manufacturing process can cause a deviation between the actual values ​​and the design values ​​of the film thickness and density of the thin film (phase shift film), and as a result, errors and variations can occur in optical characteristics such as the amount of phase shift within the mask blank or mask or between individual masks.

[0008] Variations in the optical characteristics of the mask caused by fluctuations in the thickness and density of such thin films (phase shift films) also affect its exposure characteristics, so it is desirable to minimize such errors and variations, especially in EUV lithography, which requires fine detail and high precision.

[0009] Therefore, an object of the present invention is to provide a reflective mask blank and a reflective mask that can ensure high-quality and stable production by minimizing the film thickness dependence and density dependence of optical properties of a thin film, such as the amount of phase shift, as well as a method for manufacturing a semiconductor device using the reflective mask. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention has the following configuration.

[0011] (Configuration 1) Configuration 1 of the present invention is a reflective mask blank having a substrate, a multilayer reflective film formed on the substrate, and a thin film formed on the multilayer reflective film, characterized in that a rate of change in reflectance of the thin film in the range of light wavelengths from 13.525 nm to 13.550 nm is not less than -12% / nm and not more than 4% / nm.

[0012] (Configuration 2) A second aspect of the present invention is the reflective mask blank according to the first aspect, wherein the thin film is made of a material containing at least one element selected from the group consisting of Ru, Cr, Pt, and Ta.

[0013] (Configuration 3) A third aspect of the present invention is the reflective mask blank according to the first aspect, wherein the thin film is a phase shift film that shifts the phase of incident light.

[0014] (Configuration 4) A fourth aspect of the present invention is the reflective mask blank according to the first aspect, wherein the thin film has a reflectance of 2% or more for EUV light.

[0015] (Configuration 5) A fifth aspect of the present invention is the reflective mask blank according to the first aspect, wherein the rate of change in reflectance is −10% / nm or more.

[0016] (Configuration 6) Configuration 6 of the present invention is the reflective mask blank according to configuration 1, characterized in that the amount of change in phase shift when the thickness of the thin film varies by 1% or the amount of change in phase shift when the density of the thin film varies by 1% is 2 degrees or less.

[0017] (Configuration 7) Configuration 7 of the present invention is the reflective mask blank according to configuration 1, characterized in that, when λmax is the wavelength at which the reflectance spectrum of the thin film has maximum reflectance in the wavelength range of 13 nm to 14 nm, and CW is the average value of two wavelengths that are closest to 13.53 nm among the wavelengths at which the reflectance is 1 / 2 of the maximum reflectance, the difference between λmax and CW is 0.05 nm or less.

[0018] (Configuration 8) Configuration 8 of the present invention is a reflective mask having a substrate, a multilayer reflective film formed on the substrate, and a thin film provided on the multilayer reflective film and having a transfer pattern formed thereon, wherein a rate of change in reflectance of the thin film in the range of light wavelengths from 13.525 nm to 13.550 nm is greater than or equal to -12% / nm and less than or equal to 4% / nm.

[0019] (Configuration 9) A ninth aspect of the present invention is the reflective mask according to the eighth aspect, wherein the thin film is made of a material containing at least one selected from the group consisting of Ru, Cr, Pt, and Ta.

[0020] (Configuration 10) A tenth aspect of the present invention is the reflective mask according to the eighth aspect, wherein the thin film is a phase shift film that shifts the phase of incident light.

[0021] (Configuration 11) An eleventh aspect of the present invention is the reflective mask according to the eighth aspect, wherein the thin film has a reflectance of 2% or more for EUV light.

[0022] (Configuration 12) A twelfth aspect of the present invention is the reflective mask according to the eighth aspect, wherein the rate of change in reflectance is −10% / nm or more.

[0023] (Configuration 13) Configuration 13 of the present invention is the reflective mask according to configuration 8, characterized in that the amount of change in phase shift when the thickness of the thin film varies by 1% or the amount of change in phase shift when the density of the thin film varies by 1% is 2 degrees or less.

[0024] (Configuration 14) Configuration 14 of the present invention is the reflective mask according to configuration 8, characterized in that, when λmax is the wavelength at which the reflectance spectrum of the thin film has maximum reflectance in the wavelength range from 13 nm to 14 nm, and CW is the average value of two wavelengths that are closest to 13.53 nm among the wavelengths at which the reflectance is half the maximum reflectance, the difference between λmax and CW is 0.05 nm or less.

[0025] (Configuration 15) Configuration 15 of the present invention is a method for manufacturing a semiconductor device, comprising exposing and transferring a transfer pattern onto a transfer target on a semiconductor substrate using a reflective mask having a transfer pattern manufactured using the reflective mask blank according to any one of configurations 1 to 7.

[0026] (Configuration 16) A sixteenth aspect of the present invention is a method for manufacturing a semiconductor device, comprising exposing and transferring the transfer pattern onto a transfer target on a semiconductor substrate using a reflective mask according to any one of the eighth to fourteenth aspects. Effect of the Invention

[0027] According to the present invention, it is possible to reduce the film thickness dependency or density dependency of optical properties (e.g., phase shift amount) of a thin film, particularly a phase shift film, formed on a reflective mask blank. As a result, even if the film thickness or density of the phase shift film varies slightly from the design value in the manufacturing process of the reflective mask blank and / or the reflective mask, it is possible to stably manufacture a high-quality reflective mask blank and a reflective mask having the desired optical properties (phase shift amount).

[0028] Furthermore, according to the semiconductor device manufacturing method of the present invention, a high-quality reflective mask having the desired optical characteristics can be used for EUV exposure, thereby making it possible to stably guarantee the quality of semiconductor devices having fine and highly accurate transfer patterns. [Brief description of the drawings]

[0029] [Figure 1] 1 is a schematic cross-sectional view of a main portion for explaining the general configuration of a reflective mask blank. FIG. [Diagram 2] 1A to 1C are process diagrams showing, in schematic cross-sectional views of essential parts, steps for producing a reflective mask from a reflective mask blank. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Note that the following embodiment is one form for embodying the present invention, and does not limit the scope of the present invention. Note that in the drawings, the same or corresponding parts are given the same reference numerals, and the description thereof may be simplified or omitted.

[0031] <Configuration of the Reflective Mask Blank 100 and Its Manufacturing Method> FIG. 1 is a schematic cross-sectional view of a main part for explaining the configuration of a reflective mask blank 100 of this embodiment. As shown in FIG. 1, the reflective mask blank 100 includes a mask blank substrate 1 (hereinafter, simply referred to as "substrate 1"), a multilayer reflective film 2 formed on a first main surface (front surface) side and reflecting EUV light, which is exposure light, a protective film 3 provided to protect the multilayer reflective film 2 and formed of a material having resistance to an etchant used when patterning a thin film (phase shift film 4) described later and a cleaning solution, and a phase shift film (sometimes referred to as an "absorbing film") 4 as a thin film that absorbs EUV light, which are laminated in this order. In addition, a back conductive film 5 for an electrostatic chuck is formed on the second main surface (back surface) side of the substrate 1. In this specification, the thin film may be referred to as a phase shift film, but the thin film may be a so-called binary film. In addition, the EUV light includes light with a wavelength of 13.5 nm, for example, light with a wavelength of 13 nm to 14 nm. In this specification, light includes not only visible light but also electromagnetic waves.

[0032] In this specification, the reflectance (absolute reflectance) of a thin film means the absolute reflectance from the surface of the thin film in a state where the thin film is formed on the multilayer reflective film formed on the substrate, and the same applies to the relative reflectance of the thin film. In addition, in this specification, the reflectance of a multilayer reflective film means the reflectance from the surface of the multilayer reflective film in a state where the multilayer reflective film is formed on the substrate. The reflectance (absolute reflectance and relative reflectance) in this specification means a value when the incident angle of EUV light to the thin film or multilayer reflective film is the same as the incident angle of EUV light used in exposure when transferring a pattern using a reflective mask or a reflective mask manufactured from a reflective mask blank to an irradiation target. The light of the EUV light source when transferring the pattern is irradiated onto the reflective mask 200 via an illumination optical system at an angle of, for example, 6° to 8° with respect to a plane perpendicular to the main surface of the reflective mask 200. The incident angle of EUV light to the thin film or multilayer reflective film is not particularly limited, but can be, for example, 6 degrees.

[0033] In this specification, for example, "having a multilayer reflective film 2 on the main surface of a mask blank substrate 1" means that the multilayer reflective film 2 is disposed in contact with the surface of the mask blank substrate 1, and also includes the case where another film is disposed between the mask blank substrate 1 and the multilayer reflective film 2. The same applies to other films. For example, "having a film B on a film A" means that the film A and the film B are disposed so as to be in direct contact with each other, and also includes the case where another film is disposed between the film A and the film B. In addition, in this specification, for example, "the film A is disposed in contact with the surface of the film B" means that the film A and the film B are disposed so as to be in direct contact with each other, without another film being interposed between the film A and the film B.

[0034] The structure of the reflective mask blank will be explained below for each layer.

[0035] <<Substrate 1>> To prevent distortion of the transfer pattern (phase shift pattern 4a) due to heat during exposure to EUV light, the substrate 1 is preferably one having a low thermal expansion coefficient within the range of 0±5 ppb / ° C. Examples of materials having a low thermal expansion coefficient within this range include SiO2-TiO2 glass and multi-component glass ceramics.

[0036] The first main surface of the substrate 1 on which the transfer pattern (phase shift pattern 4a) is formed is surface-processed to have a high flatness in order to obtain at least pattern transfer accuracy and positional accuracy. In the case of EUV exposure, the flatness is preferably 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less in a 132 mm×132 mm region of the first main surface of the substrate 1. The second main surface opposite to the side on which the transfer pattern is formed is a surface that is electrostatically chucked when set in an exposure device. The flatness is preferably 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less in a 132 mm×132 mm region of the second main surface of the substrate 1. The flatness of the second main surface side of the reflective mask blank 100 is preferably 1 μm or less, more preferably 0.5 μm or less, and particularly preferably 0.3 μm or less in a 142 mm×142 mm region. In this specification, flatness is a value that indicates the warpage (deformation amount) of the surface indicated by TIR (Total Indicated Reading). This value is the absolute value of the difference in height between the highest point on the surface of the substrate 1 above the focal plane, which is determined by the least squares method with the surface of the substrate 1 as the reference plane, and the lowest point on the surface of the substrate 1 below the focal plane.

[0037] In addition, it is preferable that the surface smoothness of the substrate 1 is high. The surface roughness of the first main surface of the substrate 1 on which the phase shift pattern 4a, which is the transfer pattern, is formed is preferably 0.1 nm or less in terms of root mean square roughness (RMS). The surface smoothness can be measured by an atomic force microscope.

[0038] Furthermore, the substrate 1 preferably has high rigidity to prevent deformation due to film stress of the films (such as the multilayer reflective film 2) formed thereon, and in particular, preferably has a high Young's modulus of 65 GPa or more.

[0039] <<Multilayer reflective film 2>> The multilayer reflective film 2 has a function of reflecting EUV light in the reflective mask 200, and is configured as a multilayer film in which layers made mainly of materials with different refractive indices are periodically laminated.

[0040] Generally, a multilayer film in which a thin film (high refractive index layer) of a light element or its compound, which is a high refractive index material, and a thin film (low refractive index layer) of a heavy element or its compound, which is a low refractive index material, are alternately laminated for about 30 to 60 periods, is used as the multilayer reflective film 2. The multilayer film may be laminated for multiple periods, with a high refractive index layer / low refractive index layer laminated in this order from the substrate 1 side as one period, or may be laminated for multiple periods, with a low refractive index layer / high refractive index layer laminated in this order from the substrate 1 side as one period. Note that the top layer of the multilayer reflective film 2, that is, the surface layer of the multilayer reflective film 2 opposite to the substrate 1, is preferably a high refractive index layer. In the above multilayer film, when a high refractive index layer / low refractive index layer laminated in this order from the substrate 1 is laminated for multiple periods, the top layer is a low refractive index layer. In this case, if the low refractive index layer constitutes the top surface of the multilayer reflective film 2, it may be easily oxidized, which may reduce the reflectance of the reflective mask 200. For this reason, it is preferable to further form a high refractive index layer on the uppermost low refractive index layer to form the multilayer reflective film 2. On the other hand, in the above multilayer film, when a laminate structure of low refractive index layer / high refractive index layer in which a low refractive index layer and a high refractive index layer are laminated in this order from the substrate 1 side is one period, the uppermost layer is the high refractive index layer and may be left as it is.

[0041] In this embodiment, a layer containing silicon (Si) is used as the high refractive index layer. The material containing Si may be a simple substance of Si, or a Si compound containing boron (B), carbon (C), nitrogen (N), and oxygen (O) in addition to Si. By using a layer containing Si as the high refractive index layer, a reflective mask 200 for EUV lithography with excellent reflectance of EUV light can be obtained. In this embodiment, a glass substrate is preferably used as the substrate 1. Si also has excellent adhesion to the glass substrate. In addition, a simple metal selected from molybdenum (Mo), ruthenium (Ru), rhodium (Rh), and platinum (Pt), or an alloy thereof is used as the low refractive index layer. For example, as the multilayer reflective film 2 for EUV light with a wavelength of 13 nm to 14 nm, a Mo / Si periodic laminate film in which Mo films and Si films are alternately laminated for about 30 to 60 periods is preferably used. In addition, the high refractive index layer, which is the uppermost layer of the multilayer reflective film 2, may be formed of silicon (Si).

[0042] The reflectance of such a multilayer reflective film 2 is, for example, 65% or more with respect to EUV light having a wavelength of 13 nm to 14 nm, and the upper limit is preferably 73%. The film thickness and period of each constituent layer of the multilayer reflective film 2 may be appropriately selected according to the exposure wavelength, and are selected so as to satisfy the law of Bragg reflection. The multilayer reflective film 2 has a plurality of high refractive index layers and a plurality of low refractive index layers, but the film thicknesses of the high refractive index layers and the low refractive index layers do not have to be the same. The film thickness of the Si layer on the outermost surface of the multilayer reflective film 2 can be adjusted within a range that does not reduce the reflectance. The film thickness of the Si (high refractive index layer) on the outermost surface can be set to 3 nm to 10 nm.

[0043] The multilayer reflective film 2 can be formed by a method known in the art. For example, the multilayer reflective film 2 can be formed by depositing each layer by ion beam sputtering. In the case of a Mo / Si periodic multilayer film, for example, a Si film with a thickness of about 4 nm is first deposited on the substrate 1 by using a Si target by ion beam sputtering, and then a Mo film with a thickness of about 3 nm is deposited by using a Mo target, and this is regarded as one period, and 30 to 60 periods are laminated to form the multilayer reflective film 2 (the outermost layer is a Si layer). In addition, when depositing the multilayer reflective film 2, it is preferable to form the multilayer reflective film 2 by supplying krypton (Kr) ion particles from an ion source and performing ion beam sputtering.

[0044] <<Protective film 3>> In order to protect the multilayer reflective film 2 from dry etching and cleaning in the manufacturing process of the reflective mask 200 described later, a protective film 3 can be formed on the multilayer reflective film 2 or in contact with the surface of the multilayer reflective film 2. The protective film 3 also serves to protect the multilayer reflective film 2 when repairing black defects in the phase shift pattern 4a using an electron beam (EB). Here, FIG. 1 shows the case where the protective film 3 is a single layer, but it can also have a laminated structure of two or more layers. The protective film 3 is made of a material that is resistant to an etchant and a cleaning solution used when patterning the phase shift film 4. By forming the protective film 3 on the multilayer reflective film 2, damage to the surface of the multilayer reflective film 2 can be suppressed when manufacturing the reflective mask 200 (EUV mask) using a substrate with a multilayer reflective film. Therefore, the reflectance characteristic of the multilayer reflective film 2 to EUV light is improved.

[0045] In the following, an example will be described in which the protective film 3 is a single layer. When the protective film 3 includes multiple layers, the properties of the material of the uppermost layer of the protective film 3 (the layer in contact with the phase shift film 4) become important in relation to the phase shift film 4. When the phase shift film 4 includes multiple layers, the properties of the material of the lowermost layer of the phase shift film 4 (the layer in contact with the protective film 3) become important in relation to the protective film 3 (the uppermost layer).

[0046] In the reflective mask blank 100 of this embodiment, a material that is resistant to the etching gas used in the dry etching for patterning the phase shift film 4 formed on the protective film 3 can be selected as the material of the protective film 3.

[0047] The protective film 3 can be made of, for example, a material containing Ru (ruthenium) as a main component (main component: 50 atomic % or more). The material containing Ru as a main component can be a simple Ru metal, a Ru alloy containing Ru and one or more metals selected from Nb, Zr, Y, B, Ti, La, Mo, Co, Cr, Rh, and / or Re, or a material containing nitrogen (N) and oxygen (O) in these materials. The protective film 14 can also have a laminated structure of three or more layers, with the bottom layer and the top layer being layers made of the material containing Ru as a main component, and a metal other than Ru or an alloy being interposed between the bottom layer and the top layer.

[0048] In EUV lithography, EUV exposure can cause contamination such as the deposition of a carbon film on the mask or the growth of an oxide film. Therefore, when a reflective mask is used in the manufacture of semiconductor devices, it is necessary to frequently clean the reflective mask to remove foreign matter and contamination from the mask. For this reason, a reflective mask is required to have a cleaning resistance that is orders of magnitude higher than that of a transmission mask for optical lithography. The reflective mask 200 has a protective film 3, which can increase the cleaning resistance against a cleaning solution.

[0049] The thickness of the protective film 3 is not particularly limited as long as it can perform the function of protecting the multilayer reflective film 2. From the viewpoint of the reflectance of EUV light, the thickness of the protective film 3 is preferably 1.0 nm to 8.0 nm, more preferably 1.5 nm to 6.0 nm.

[0050] Any known film formation method can be used without any particular limitation as a method for forming the protective film 3. Specific examples include a sputtering method and an ion beam sputtering method.

[0051] <<Phase shift film 4>> In this embodiment, a phase shift film 4 that shifts the phase of EUV light is formed as a thin film on the protective film 3. The phase shift film 4 may be a single layer film or a laminated film including multiple layers. The laminated film may include a lower layer and an upper layer formed on the lower layer. The lower layer may be, for example, a buffer layer. The lower layer may further include multiple layers. The same applies to the upper layer. In the portion where the phase shift film 4 (phase shift pattern 4a) is formed, the EUV light is absorbed and reduced, while a part of the light is reflected at a level that does not adversely affect the pattern transfer. On the other hand, in the opening (the portion where the phase shift film 4 is not present), the EUV light is reflected from the multilayer reflective film 2 via the protective film 3. The phase shift film 4 is formed so that the reflected light from the surface of the multilayer reflective film 2 and the reflected light from the surface of the phase shift film 4 have a predetermined phase difference (also referred to as "phase shift amount"). For example, light having a phase difference between each other within a range of 100 to 300° interferes with each other at the pattern edge portion, thereby improving the image contrast of the projected optical image. With the improvement in image contrast, the resolution increases and various latitudes relating to exposure, such as exposure dose latitude and focus latitude, are expanded.

[0052] When the reflective mask blank 100 or the reflective mask 200 is irradiated with EUV light, the lower limit of the phase difference of the reflected light of the phase shift film 4 relative to the reflected light from the multilayer reflective film 2 is 100 degrees or more, preferably 150 degrees or more, more preferably 180 degrees or more, and even more preferably 200 degrees or more. The upper limit of the phase difference of the reflected light of the phase shift film 4 relative to the reflected light from the multilayer reflective film 2 may be 310 degrees or less, preferably 300 degrees or less, more preferably 280 degrees or less, and even more preferably 250 degrees or less.

[0053] In the reflective mask blank 100 of this embodiment, the absolute reflectance from the surface of the phase shift film 4 (phase shift pattern 4a) to EUV light is preferably 2% or more. Here, absolute reflectance means the reflected light intensity relative to the incident light intensity. That is, the absolute reflectance of the phase shift film 4 is calculated by the formula "absolute reflectance=amount of light reflected from the surface of the phase shift film / amount of light incident on the surface of the phase shift film", and when the unit is %, it is further multiplied by 100. In addition, when simply referring to the reflectance of the phase shift film 4 (thin film) in this specification, it means the absolute reflectance unless otherwise specified.

[0054] Here, in the reflective mask blank 100 of this embodiment, at least a multilayer reflective film 2 and a phase shift film 4 are formed in this order on a substrate 1. In this embodiment, in order to solve the problems of the present invention and obtain the desired contrast performance, the relative reflectance from the surface of the phase shift film 4 is preferably 3% or more, and more preferably 4% or more. Moreover, the relative reflectance from the surface of the phase shift film 4 is preferably 30% or less, and more preferably 20% or less.

[0055] Here, the relative reflectance from the surface of the phase shift film 4 refers to the reflectance (%) of light reflected from the surface of the phase shift film 4 relative to the reflectance of light reflected from the multilayer reflective film 2 (including protective film 3) when irradiated with EUV light, assuming that the reflectance of light reflected from this multilayer reflective film 2 (including protective film 3) is 100%. In other words, the relative reflectance (%) of the phase shift film is the value obtained by dividing the absolute reflectance of the phase shift film 4 by the reflectance of the multilayer reflective film 2 (including protective film 3) and multiplying this value by 100.

[0056] The phase shift film 4 formed on the multilayer reflective film 2 of the reflective mask blank 100 according to this embodiment is formed so that in its reflectance spectrum, the rate of change in (absolute) reflectance from 13.525 nm to 13.550 nm for EUV light wavelengths is greater than or equal to -12% / nm and less than or equal to +4% / nm.

[0057] The "change rate of reflectance" means the ratio of the change in absolute reflectance (R2-R1) obtained from the reflectance at λ1:13.525 nm, which is a wavelength near the central wavelength 13.53 nm of EUV light, and the reflectance at λ2:13.550 nm (formula (1)). In other words, the change rate of reflectance is the difference obtained by subtracting the reflectance R1 at λ1:13.525 nm from the reflectance R2 at λ2:13.550 nm, divided by the difference (0.025 nm) obtained by subtracting λ1:13.525 nm from λ2:13.550 nm.

number

[0058] The inventors analyzed the reflectance spectrum and optical characteristics of the phase shift film 4 under various conditions. As a result, as described above, it was found that if the rate of change in reflectance of the phase shift film 4 is -12% / nm or more and +4% / nm or less at least in the wavelength range from 13.525 nm to 13.550 nm, the film thickness dependency and density dependency of the phase shift amount in the phase shift film 4 can be sufficiently suppressed to a desired value or less. In addition, 13.525 nm and 13.550 nm are very close values. Therefore, in the reflectance spectrum of the phase shift film 4, the slope of the tangent at the wavelength of 13.53 nm may be 12% / nm or more and +4% / nm or less. The above wavelength of 13.53 nm corresponds to the central wavelength λc of the EUV exposure light used to form a transfer pattern of a semiconductor device.

[0059] Here, in order to ensure high-quality manufacture of the reflective mask blank 100 and the reflective mask 200 described later, it is desirable that the thickness dependency of the phase shift film 4 is such that the amount of change in the phase shift when the thickness of the phase shift film 4 varies by 1% is 2 degrees or less. Also, it is desirable that the density dependency of the phase shift film 4 is such that the amount of change in the phase shift when the density of the material of the phase shift film 4 varies by 1% is 2 degrees or less.

[0060] The change in the phase shift amount (phase shift amount distribution) when the thickness or density of the phase shift film 4 varies by 1% can be obtained by simulation from data such as the refractive index n, extinction coefficient k, thickness and density of the thin film.

[0061] In particular, in order to reduce the density dependency of the optical properties of the phase shift film 4, it is more preferable that the difference between the wavelength λmax at which the reflectance is maximum and the wavelength CW at which the half-width of the maximum reflectance is the median, within the wavelength range of 13 nm to 14 nm in the reflectance spectrum of the phase shift film 4 for EUV light, is 0.05 nm or less. More specifically, among the wavelengths at which the absolute reflectance is 1 / 2 of the maximum reflectance Rmax within the wavelength range of 13 nm to 14 nm, the difference between the two wavelengths λ closest to the wavelength λmax at which the maximum reflectance is maximum is 0.05 nm or less. - 1 / 2 , λ + 1 / 2 When the average value of is CW (median half-width wavelength), the difference (distance) between the wavelength λmax and CW is preferably 0.05 nm or less. The reflectance spectrum refers to a spectrum in which the absolute reflectance from the surface of the thin film (phase shift film) 4 is plotted on the vertical axis and the wavelength of the irradiated light (electromagnetic wave) is plotted on the horizontal axis.

[0062] The material of the phase shift film 4, which is a thin film formed on the multilayer reflective film 2, is not particularly limited as long as it has the function of absorbing EUV light and shifting the phase, can be processed by etching or the like (preferably, dry etching is possible with a chlorine (Cl)-based gas and / or a fluorine (F)-based gas), and the rate of change in reflectance or the slope of its tangent satisfies the above-mentioned requirements. Examples of materials for the phase shift film 4 include materials containing at least one element selected from the group consisting of ruthenium (Ru), tantalum (Ta), chromium (Cr), rhodium (Rh), molybdenum (Mo), niobium (Nb), titanium (Ti), zirconium (Zr), yttrium (Y), silicon (Si), palladium (Pd), silver (Ag), platinum (Pt), gold (Au), iridium (Ir), tungsten (W), cobalt (Co), manganese (Mn), tin (Sn), vanadium (V), nickel (Ni), iron (Fe), hafnium (Hf), copper (Cu), tellurium (Te), zinc (Zn), magnesium (Mg), germanium (Ge), and aluminum (Al). Furthermore, the material of the phase shift film 4 may be a material that further contains, in addition to these elements, at least one element selected from oxygen (O), nitrogen (N), carbon (C) and boron (B).

[0063] The phase shift film 4 is more preferably made of a material containing at least one element selected from Ru, Cr, Pt, and Ta. Examples include Ru-based materials, RuCr-based materials, RuPt-based materials, RuTa-based materials, TaNb-based materials, IrTa-based materials, Cr-based materials, Pt-based materials, PtTa-based materials, PtCr-based materials, PtTi-based materials, PtNb-based materials, and PtMo-based materials. In addition to these materials, the phase shift film 4 may be made of a material further containing at least one element selected from O, N, C, and B.

[0064] The phase shift film 4 can be formed by a known film formation method such as magnetron sputtering such as DC sputtering and RF sputtering, or ion beam sputtering. The sputtering target can contain at least one element selected from the group consisting of Ru, Ta, Cr, Rh, Mo, Nb, Ti, Zr, Y, Si, Pd, Ag, Pt, Au, Ir, W, Co, Mn, Sn, V, Ni, Fe, Hf, Cu, Te, Zn, Mg, Ge, and Al.

[0065] <<Backside conductive film 5>> A back surface conductive film 5 for electrostatic chuck may be formed on the second main surface (back surface) side (opposite the surface on which the multilayer reflective film 2 is formed) of the substrate 1. The electrical characteristics (sheet resistance) of the back surface conductive film 5 for electrostatic chuck is preferably 100 Ω / □ (Ω / Square) or less. The back surface conductive film 5 can be formed, for example, by magnetron sputtering or ion beam sputtering using a target of a metal or alloy such as chromium or tantalum.

[0066] The material of the back surface conductive film 5 is preferably a material containing chromium (Cr) or tantalum (Ta). For example, the material of the back surface conductive film 5 is preferably a Cr compound containing at least one selected from boron, nitrogen, oxygen, and carbon in Cr. Examples of the Cr compound include CrN, CrON, CrCN, CrCON, CrBN, CrBON, CrBCN, and CrBOCN. The material of the back surface conductive film 5 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 the Ta compound include TaB, TaN, TaO, TaON, TaCON, TaBN, TaBO, TaBON, TaBCON, TaHf, TaHO, TaHN, TaHON, TaHON, TaHCON, TaSi, TaSiO, TaSiN, TaSiONCON, TaSi, TaSiO, TaSiN, TaSiON, and TaSiCON.

[0067] The thickness of the back surface conductive film 5 is not particularly limited as long as it satisfies the function for electrostatic chuck, but is usually 10 nm to 200 nm. The back surface conductive film 5 also functions to adjust the stress on the second main surface side of the mask blank 100, and is adjusted to obtain a flat reflective mask blank 100 by balancing with the stress from various films formed on the first main surface side.

[0068] In the reflective mask blank 100 of this embodiment, an etching mask film (not shown) can be further formed on the phase shift film 4 as necessary. The etching mask film is preferably formed of a material having etching selectivity with respect to the phase shift film 4. Examples of materials for the etching mask film include materials containing one or more elements selected from Cr, Ta, and Si, and materials further containing one or more elements selected from O, N, C, and B in addition to these materials. The etching mask film may be a single layer film or a laminated film containing multiple layers.

[0069] The etching mask film can be formed by a known method such as DC sputtering, RF sputtering, or ion beam sputtering. The thickness of the etching mask film is preferably 5 nm or more from the viewpoint of ensuring the function as a hard mask. Considering the thickness of the phase shift film 15, the thickness of the etching mask film is preferably 5 nm or more and 20 nm or less, and more preferably 5 nm or more and 15 nm or less.

[0070] When the thin film is a phase shift film and the reflective mask 200 has a patterned region where a transfer pattern is formed and a non-patterned region surrounding the patterned region, the non-patterned region can be covered with a film having low reflectance (binary film) so that the transfer target (such as a resist film) on the semiconductor substrate corresponding to the non-patterned region is not unnecessarily exposed to light. This binary film may be provided separately between the etching mask film and the thin film. In addition, when the reflectance of the etching mask film to EUV light is sufficiently low, the etching mask film may be used as the binary film.

[0071] According to the reflective mask blank 100 of the present embodiment, the film thickness dependency and density dependency of the phase shift amount in the phase shift film 4 can be reduced more than in the past. As a result, even if slight variations occur in the film thickness and density of the phase shift film 4 in the manufacturing process of the reflective mask blank 100, a high-quality reflective mask blank 100 having desired optical characteristics can be stably manufactured.

[0072] <Reflection mask 200 and its manufacturing method> The reflective mask 200 according to the present embodiment has a phase shift pattern 4a formed by patterning the phase shift film 4 of the above-mentioned reflective mask blank 100. The phase shift pattern 4a can be formed by patterning the phase shift film 4 of the reflective mask blank 100 with a predetermined dry etching gas (e.g., a dry etching gas containing a chlorine-based gas and an oxygen gas, or a dry etching gas containing fluorine).

[0073] 2 is a schematic diagram showing an example of a method for manufacturing a reflective mask 200. First, a reflective mask blank 100 is prepared, which has a substrate 1, a multilayer reflective film 2 formed on the substrate 1, a protective film 3 formed on the multilayer reflective film 2, and a phase shift film 4 formed on the protective film 3. Then, a resist film 11 is formed on the phase shift film 4 of the reflective mask blank 100 (FIG. 2(a)). The thickness of the resist film 11 is, for example, 100 nm.

[0074] Next, a pattern is drawn on this resist film 11 by exposure using an electron beam lithography device, and further undergoes a developing and rinsing process to form a resist pattern 11a (FIG. 2(b)). Then, using the resist pattern 11a as a mask, the phase shift film 4 is dry etched. As a result, the portion of the phase shift film 4 that is not covered by the resist pattern 11a is removed, and a phase shift pattern 4a is formed (FIG. 2(c)).

[0075] The etching gas for the phase shift film 4 is appropriately selected depending on the material of the phase shift film 4. For example, the etching gas for the phase shift film 4 may be, but is not limited to, a chlorine-based gas containing oxygen, an oxygen gas / fluorine-based gas, or a chlorine-based gas not containing oxygen gas depending on the material of the phase shift film 4 and its composition ratio.

[0076] In order to pattern the phase shift film 4, an etching mask film may be provided on the phase shift film 4 as necessary, and the phase shift film 4 may be dry-etched using the etching mask film pattern as a mask to form the phase shift pattern 4a.

[0077] Finally, the resist pattern 11a is removed by ashing or a resist stripper, and wet cleaning is performed using an acidic or alkaline aqueous solution.

[0078] Through the above steps, a reflective mask 200 having a desired transfer pattern is manufactured.

[0079] According to the reflective mask 200 of the present embodiment, the film thickness dependency and density dependency of the phase shift amount in the phase shift pattern 4a can be reduced more than in the past. As a result, even if slight variations occur in the film thickness or density of the phase shift film 4 in the manufacturing process of the reflective mask blank 100 or the reflective mask 200, it is possible to stably manufacture a high-quality reflective mask 200 having desired optical characteristics.

[0080] <Method of manufacturing semiconductor devices> Next, a description will be given of a method for manufacturing a semiconductor device using the above-mentioned reflective mask 200. According to this embodiment, the reflective mask 200 is set in an exposure tool having an exposure light source of EUV light, and a transfer pattern is transferred to a transfer target (resist film) formed on a transfer (semiconductor) substrate, thereby manufacturing a semiconductor device.

[0081] According to the semiconductor device manufacturing method of this embodiment, a high-quality reflective mask 200 having the desired optical characteristics can be used for exposure transfer, so that the quality of semiconductor devices having fine and highly accurate transfer patterns can be stably guaranteed. EXAMPLES

[0082] Specific examples and comparative examples of the reflective mask blank according to the present invention will be described below with reference to Table 1.

[0083] [Table 1]

[0084] In Table 1, the rate of change in reflectance of the phase shift film represents the rate of change in absolute reflectance of the thin film (phase shift film) 4 from wavelength 13.525 nm to 13.550 nm. The rate of change in reflectance of these phase shift films was calculated from the absolute reflectances measured at wavelengths of 13.525 nm and 13.550 nm, as described above. The reflective mask blanks of Examples 1 to 10 had a rate of change in reflectance from wavelengths of 13.525 nm to 13.550 nm of -12 / nm or more and +4% / nm or less. On the other hand, none of Comparative Examples 1 to 4 satisfied this requirement. The rate of change in reflectance of the above-mentioned phase shift film (thin film) may be determined from the reflectance spectrum of the thin film when EUV light having a central wavelength of about 13.5 nm is incident thereon. In this case, the reflective mask blanks of Examples 1 to 10 had a rate of change in reflectance from a wavelength of 13.525 nm to 13.550 nm of -12 / nm or more and +4% / nm or less, while none of Comparative Examples 1 to 4 satisfied this requirement.

[0085] In Table 1, phase shift distribution A is the change in phase shift amount [degrees] when the thickness of the thin film 4 (phase shift film) changes by 1%, i.e., it is an index showing the film thickness dependency of the phase shift amount. Phase shift distribution B is the change in phase shift amount [degrees] when the density of the thin film (phase shift film) 4 changes by 1%, i.e., it is an index showing the density dependency of the phase shift amount. Note that, when the thin film (phase shift film) 4 includes a lower layer and an upper layer, the change in phase shift amount [degrees] indicates the value when the thickness or density of the upper layer changes by 1%. The phase shift amount distributions A and B can be obtained by simulation from the refractive index n, extinction coefficient k, film thickness, density, and the like of the thin film.

[0086] Referring to Table 1, in the reflective mask blanks of Examples 1 to 10, at least one of the phase shift amount distributions A and B was 2 degrees or less. On the other hand, in the reflective mask blanks of Comparative Examples 1 to 4, both the phase shift amount distributions A and B were higher than 2 degrees.

[0087] Hereinafter, a detailed description will be given of each of the Examples and Comparative Examples shown in Table 1. In the following, the phase shift film 4 will be simply referred to as the thin film 4.

[0088] Example 1 A multilayer reflective film 2 was formed on the main surface of a SiO2-TiO2-based glass substrate 1, and a protective film 3 made of a RuNb film was formed on the surface of the multilayer reflective film 2. Next, a lower layer made of TaBN and an upper layer made of CrN were formed on the lower layer on the protective film 3 to form a thin film 4 as a phase shift film 4. The conditions for forming the thin film 4 in Example 1 are shown below. Lower layer (TaBN film): TaB alloy target, Ar and N2 mixed gas atmosphere, film thickness 4 nm Upper layer (CrN film): Cr target, Ar and N2 mixed gas atmosphere, film thickness 37.1 nm

[0089] The composition (atomic ratio) of the lower layer was Ta:B:N=60:15:25, and the composition (atomic ratio) of the upper layer was Cr:N=75:25.

[0090] The refractive index n and extinction coefficient k at a wavelength of 13.5 nm of the TaBN film and CrN film of Example 1 formed as described above were as follows, respectively. Lower layer (TaBN film): n=0.9511, k=0.0325 Upper layer (CrN film): n=0.9279, k=0.0384

[0091] The absolute reflectance of the thin film 4 at an EUV light wavelength of 13.5 nm was 2.9%. The density of the lower layer was 14.99 g / cm 3 and the density of the upper layer is 7.08 g / cm 3 The phase shift amount of the thin film 4 formed under these conditions was 142 degrees at a wavelength of 13.5 nm.

[0092] The change rate of reflectance of the thin film 4 in Example 1 from 13.525 nm to 13.550 nm was −9.8% / nm. The phase shift amount distribution A of the thin film 4 was 0.02 degrees, and the phase shift amount distribution B was 1.24 degrees, both of which were less than the predetermined 2 degrees.

[0093] Example 2 A multilayer reflective film 2 was formed on a main surface of a SiO2-TiO2-based glass substrate 1, and a thin film 4 made of TaNb was formed on the surface of the multilayer reflective film 2. The conditions for forming the thin film 4 in Example 2 are shown below. TaNb film: TaNb alloy target, Ar gas atmosphere, film thickness 39.8 nm

[0094] The composition (atomic ratio) of this thin film 4 was Ta:Nb=70:30.

[0095] The refractive index n and extinction coefficient k at a wavelength of 13.5 nm of the TaNb film of Example 2 formed as described above were as follows. TaNb film: n=0.9522, k=0.0244

[0096] The absolute reflectance of the thin film 4 made of the TaNb film at an EUV light wavelength of 13.5 nm was 9.1%. The density of the thin film 4 was 13.54 g / cm 3The phase shift amount of the thin film 4 formed under these conditions was 103 degrees at a wavelength of 13.5 nm.

[0097] The change rate of reflectance of the thin film 4 in Example 2 from 13.525 nm to 13.550 nm was −0.6% / nm. The phase shift amount distribution A of the thin film 4 was 0.24 degrees, and the phase shift amount distribution B was 1.09 degrees, both of which were within the prescribed 2 degrees.

[0098] Example 3 A multilayer reflective film 2 was formed on the main surface of a SiO2-TiO2-based glass substrate 1, and a thin film 4 made of IrTa was formed on the surface of the multilayer reflective film 2. The conditions for forming the thin film 4 in Example 3 are shown below. IrTa film: IrTa alloy target, Ar gas atmosphere, film thickness 25.7 nm

[0099] The composition (atomic ratio) of this thin film 4 was Ir:Ta=81:19.

[0100] The refractive index n and extinction coefficient k at a wavelength of 13.5 nm of the IrTa film of Example 3 formed as described above were as follows. IrTa film: n=0.9149, k=0.0430

[0101] The absolute reflectance of the thin film 4 made of the IrTa film at the EUV light wavelength of 13.5 nm was 6.0%. The density of the thin film 4 was 21.57 g / cm 3 The phase shift amount of the thin film 4 formed under these conditions was 125 degrees at a wavelength of 13.5 nm.

[0102] The change rate of reflectance of the thin film 4 in Example 3 from 13.525 nm to 13.550 nm was 3.5% / nm. The phase shift amount distribution A of the thin film 4 was 0.18 degrees, and the phase shift amount distribution B was 1.43 degrees, both of which were within the prescribed 2 degrees.

[0103] Example 4 A multilayer reflective film 2 was formed on the main surface of a SiO2-TiO2-based glass substrate 1, and a protective film 3 made of a RuRhCrN film was formed on the surface of the multilayer reflective film 2. Next, a lower layer made of TaON was formed on the protective film 3, and an upper layer made of RuCrON was formed on the lower layer, thereby forming a thin film 4. The conditions for forming the thin film 4 in Example 4 are shown below. Lower layer (TaON film): Ta target, Ar, O2 and N2 mixed gas atmosphere, film thickness 3 nm Upper layer (RuCrON film): RuCr alloy target, mixed gas atmosphere of Ar, O2 and N2, film thickness 38.9 nm

[0104] The composition (atomic ratio) of the TaON film was Ta:O:N=33.5:28.3:38.2, and the composition (atomic ratio) of the RuCrON film was Ru:Cr:O:N=61:16:8:15.

[0105] The refractive index n and extinction coefficient k at a wavelength of 13.5 nm of the TaON film and RuCrON film of Example 4 formed as described above were as follows, respectively. Lower layer (TaON film): n=0.9550,k=0.0255 Upper layer (RuCrON film): n=0.9091, k=0.0196

[0106] The absolute reflectance of the thin film 4 consisting of the TaON film and the RuCrON film at the EUV light wavelength of 13.5 nm was 10.8%. The density of the lower layer was 9.28 g / cm 3 and the density of the upper layer is 9.44 g / cm 3 The phase shift amount of the thin film 4 formed under these conditions was 195 degrees at a wavelength of 13.5 nm.

[0107] The change rate of reflectance of the thin film 4 in Example 4 from wavelengths of 13.525 nm to 13.550 nm was −10.1% / nm. The phase shift distribution A of the thin film 4 at this time was 0.07 degrees, which was less than the prescribed 2 degrees.

[0108] Example 5 A multilayer reflective film 2 was formed on the main surface of a SiO2-TiO2-based glass substrate 1, and a protective film 3 made of a RuRhCrN film was formed on the surface of the multilayer reflective film 2. Next, a lower layer made of CrN was formed on the protective film 3, and an upper layer made of PtRu was formed on the lower layer, thereby forming a thin film 4. The conditions for forming the thin film 4 in Example 5 are shown below. Lower layer (CrN film): Cr target, Ar and N2 mixed gas atmosphere, film thickness 4 nm Upper layer (PtRu film): PtRu alloy target, Ar gas atmosphere, film thickness 30.2 nm

[0109] The composition (atomic ratio) of the CrN film was Cr:N=75:25, and the composition (atomic ratio) of the PtRu film was Pt:Ru=49:51.

[0110] The refractive index n and extinction coefficient k at a wavelength of 13.5 nm of the CrN film and PtRu film of Example 5 formed as described above were as follows, respectively. Lower layer (CrN film): n=0.9279,k=0.0384 Upper layer (PtRu film): n=0.8908, k=0.0385

[0111] The absolute reflectance of the thin film 4 consisting of the CrN film and the PtRu film at the EUV light wavelength of 13.5 nm was 3.6%. The density of the lower layer was 7.08 g / cm 3 and the density of the upper layer is 16.74 g / cm 3 The phase shift amount of the thin film 4 formed under these conditions was 199 degrees at a wavelength of 13.5 nm.

[0112] The change rate of reflectance of the thin film 4 in Example 5 from wavelengths of 13.525 nm to 13.550 nm was 0.6% / nm. The phase shift distribution A of the thin film 4 at this time was 0.95 degrees, which was less than the prescribed 2 degrees.

[0113] Example 6 A multilayer reflective film 2 was formed on the main surface of a SiO2-TiO2-based glass substrate 1, and a protective film 3 made of a RuNb film was formed on the surface of the multilayer reflective film 2. Next, a lower layer made of TaBO was formed on the protective film 3, and an upper layer made of RuCrN was formed on the lower layer, thereby forming a thin film 4. The conditions for forming the thin film 4 in Example 6 are shown below. Lower layer (TaBO film): TaB alloy target, Ar and O2 mixed gas atmosphere, film thickness 6 nm Upper layer (RuCrN film): RuCr alloy target, Ar and N2 mixed gas atmosphere, film thickness 44.5 nm

[0114] The composition (atomic ratio) of the TaBO film was Ta:B:O=35:5:60, and the composition (atomic ratio) of the RuCrN film was Ru:Cr:N=68:17:16.

[0115] The refractive index n and extinction coefficient k at a wavelength of 13.5 nm of the TaBO film and RuCrN film of Example 6 formed as described above were as follows, respectively. Lower layer (TaBO film): n=0.9573,k=0.0261 Upper layer (RuCrN film): n=0.8803, k=0.0246

[0116] The absolute reflectance of the thin film 4 consisting of the TaBO film and the RuCrN film at an EUV light wavelength of 13.5 nm was 4.2%. The density of the lower layer was 9.00 g / cm 3 and the density of the upper layer is 12.65 g / cm 3 The phase shift amount of the thin film 4 formed under these conditions was 298 degrees at a wavelength of 13.5 nm.

[0117] The change rate of reflectance of the thin film 4 in Example 6 from wavelengths of 13.525 nm to 13.550 nm was −11.1% / nm. The phase shift distribution A of the thin film 4 at this time was 0.76 degrees, which was less than the prescribed 2 degrees.

[0118] Example 7 A multilayer reflective film 2 was formed on the main surface of a SiO2-TiO2-based glass substrate 1, and a protective film 3 made of a RuRhCrN film was formed on the surface of the multilayer reflective film 2. Next, a lower layer made of TaON was formed on the protective film 3, and an upper layer made of RuCrON was formed on the lower layer, thereby forming a thin film 4. The conditions for forming the thin film 4 in Example 7 are shown below. Lower layer (TaON film): Ta target, Ar, O2 and N2 mixed gas atmosphere, film thickness 3 nm Upper layer (RuCrON film): RuCr alloy target, mixed gas atmosphere of Ar, O2 and N2, film thickness 35.2 nm

[0119] The compositions (atomic ratios) of the TaON film and the RuCrON film were Ta:O:N=33.5:28.3:38.2 and Ru:Cr:O:N=61:16:8:15, respectively.

[0120] The refractive index n and extinction coefficient k at a wavelength of 13.5 nm of the TaON film and RuCrON film of Example 7 formed as described above were as follows, respectively. Lower layer (TaON film): n=0.9550,k=0.0255 Upper layer (RuCrON film): n=0.9182, k=0.0177

[0121] The absolute reflectance of the thin film 4 consisting of the TaON film and the RuCrON film at the EUV light wavelength of 13.5 nm was 18.0%. The density of the lower layer was 9.28 g / cm 3 and the density of the upper layer is 8.50 g / cm 3 The phase shift amount of the thin film 4 formed under these conditions was 164 degrees at a wavelength of 13.5 nm.

[0122] The change rate of reflectance of the thin film 4 in Example 7 from wavelengths of 13.525 nm to 13.550 nm was 2.7% / nm. The phase shift distribution B of the thin film 4 at this time was 1.44 degrees, which was less than the prescribed 2 degrees.

[0123] Example 8 A multilayer reflective film 2 was formed on the main surface of a SiO2-TiO2-based glass substrate 1, and a protective film 3 made of a RuRhCrN film was formed on the surface of the multilayer reflective film 2. Next, a lower layer made of TaBN and TaBO laminated in this order was formed on the protective film 3, and an upper layer made of RuN was formed on the lower layer to form a thin film 4. The conditions for forming the thin film 4 in Example 8 are shown below. Lower layer (TaBN film): TaB alloy target, Ar and N2 mixed gas atmosphere, film thickness 13.2 nm Lower layer (TaBO film): TaB alloy target, Ar and O2 mixed gas atmosphere, film thickness 4.9 nm Upper layer (RuN film): Ru target, Ar and N2 mixed gas atmosphere, film thickness 26.5 nm

[0124] The compositions (atomic ratios) of the TaBN film, the TaBO film, and the RuN film were Ta:B:N=60:15:25, Ta:B:O=35:5:60, and Ru:N=94:6, respectively.

[0125] The refractive index n and extinction coefficient k at a wavelength of 13.5 nm of the TaBN film, TaBO film, and RuN film of Example 8 formed as described above were respectively as follows. Lower layer (TaBN film): n=0.9511, k=0.0325 Lower layer (TaBO film): n=0.9573, k=0.0261 Upper layer (RuN film): n=0.8891, k=0.0170

[0126] The absolute reflectance of the thin film 4 consisting of the TaBN film, the TaBO film and the RuN film at an EUV light wavelength of 13.5 nm was 11.9%. The density of the TaBN film was 14.99 g / cm 3 , the density of the TaBO film is 9.00 g / cm 3 , the density of the upper layer is 12.00g / cm 3 The phase shift amount of the thin film 4 formed under these conditions was 204 degrees at a wavelength of 13.5 nm.

[0127] The change rate of reflectance of the thin film 4 in Example 8 from wavelengths of 13.525 nm to 13.550 nm was −11.5% / nm. The phase shift distribution B of the thin film 4 at this time was 1.36 degrees, which was less than the prescribed 2 degrees.

[0128] Example 9 A multilayer reflective film 2 was formed on the main surface of a SiO2-TiO2-based glass substrate 1, and a protective film 3 made of a RuNb film was formed on the surface of the multilayer reflective film 2. Next, a lower layer made of TaBO and an upper layer made by laminating RuCrN and RuCrO in this order on the lower layer were formed on the protective film 3, thereby forming a thin film 4. The conditions for forming the thin film 4 in Example 9 are shown below. Lower layer (TaBO film): TaB alloy target, Ar and O2 mixed gas atmosphere, film thickness 10.5 nm Upper layer (RuCrN film): RuCr alloy target, Ar and N2 mixed gas atmosphere, film thickness 29.2 nm Upper layer (RuCrO film): RuCr alloy target, Ar and O2 mixed gas atmosphere, film thickness 4 nm

[0129] The composition (atomic ratio) of the TaBO film was Ta:B:O = 35:5:60. The composition (atomic ratio) of the RuCrN film was Ru:Cr:N = 68:17:16. The composition (atomic ratio) of the RuCrO film was Ru:Cr:O = 27:27:46.

[0130] The refractive index n and extinction coefficient k at a wavelength of 13.5 nm of the TaBO film, RuCrN film, and RuCrO film of Example 9 formed as described above were as follows, respectively. Lower layer (TaBO film): n=0.9573, k=0.0261 Upper layer (RuCrN film): n=0.9003, k=0.0205 Upper layer (RuCrO film): n=0.9213, k=0.0268

[0131] The absolute reflectance of the thin film 4 consisting of the TaBO film and the RuCrN / RuCrO film at an EUV light wavelength of 13.5 nm was 12.5%. The density of the TaBO film was 9.00 g / cm 3, the density of the RuCrN film is 10.54 g / cm 3 and the density of the RuCrO film is 7.41 g / cm 3 The phase shift amount of the thin film 4 formed under these conditions was 194 degrees at a wavelength of 13.5 nm.

[0132] The change rate of reflectance of the thin film 4 in Example 9 from wavelengths of 13.525 nm to 13.550 nm was −10.0% / nm. The phase shift distribution B of the thin film 4 at this time was 1.47 degrees, which was less than the prescribed 2 degrees.

[0133] Example 10 A multilayer reflective film 2 was formed on the main surface of a SiO2-TiO2-based glass substrate 1, and a protective film 3 made of a RuNb film was formed on the surface of the multilayer reflective film 2. Next, a lower layer made of TaBO was formed on the protective film 3, and an upper layer made of RuCrN was formed on the lower layer, thereby forming a thin film 4. The conditions for forming the thin film 4 in Example 10 are shown below. Lower layer (TaBO film): TaB alloy target, Ar and O2 mixed gas atmosphere, film thickness 6 nm Upper layer (RuCrN film): RuCr alloy target, Ar and N2 mixed gas atmosphere, film thickness 38.8 nm

[0134] The compositions (atomic ratios) of the TaBO film and the RuCrN film were Ta:B:O=35:5:60 and Ru:Cr:N=68:17:16, respectively.

[0135] The refractive index n and extinction coefficient k at a wavelength of 13.5 nm of the TaBO film and RuCrN film of Example 10 formed as described above were as follows, respectively. Lower layer (TaBO film): n=0.9573, k=0.0261 Upper layer (RuCrN film): n=0.9003, k=0.0205

[0136] The absolute reflectance of the thin film 4 consisting of the TaBO film and the RuCrN film at an EUV light wavelength of 13.5 nm was 12.2%. The density of the TaBO film was 9.00 g / cm 3and the density of the RuCrN film is 10.54 g / cm 3 The phase shift amount of the thin film 4 formed under these conditions was 224 degrees at a wavelength of 13.5 nm.

[0137] The change rate of reflectance of the thin film 4 in Example 10 from 13.525 nm to 13.550 nm was −5.0% / nm. The phase shift distribution B of the thin film 4 at this time was 1.90 degrees, which was less than the prescribed 2 degrees.

[0138] A reflective mask was manufactured from the reflective mask blanks obtained in Examples 1 to 10, and a transfer image was obtained by simulating the transfer of the resist film (transfer target) on a semiconductor device by exposure to EUV light using this reflective mask. In Examples 1 to 10, the transfer pattern in this transfer image had high CD in-plane uniformity, and was fine and highly accurate. From this result, it was found that when a transfer pattern is transferred to a resist film on a semiconductor device using a reflective mask obtained from the reflective mask blanks of Examples 1 to 10, the circuit pattern finally formed on the semiconductor device can be formed with high accuracy.

[0139] Comparative Example 1 In Comparative Example 1, a multilayer reflective film was formed on the main surface of the same SiO2-TiO2-based glass substrate as in the Example, and a protective film made of a RuNb film was formed on the multilayer reflective film. A lower layer made of TaBO, and an upper layer made of a RuCrN film and a RuCrO film were formed on the lower layer in this order to form a thin film. The conditions for forming the thin film 4 in Comparative Example 1 are shown below. Lower layer (TaBO film): TaB alloy target, Ar and O2 mixed gas atmosphere, film thickness 10.5 nm Upper layer (RuCrN film): RuCr alloy target, Ar and N2 mixed gas atmosphere, film thickness 43.5 nm Upper layer (RuCrO film): RuCr alloy target, Ar and O2 mixed gas atmosphere, film thickness 4 nm

[0140] The composition (atomic ratio) of the TaBO film was Ta:B:O = 35:5:60. The composition (atomic ratio) of the RuCrN film was Ru:Cr:N = 68:17:16. The composition (atomic ratio) of the RuCrO film was Ru:Cr:O = 27:27:46. The density of the TaBO film was 9.00 g / cm 3 , the density of the RuCrN film is 12.65 g / cm 3 and the density of the RuCrO film is 7.41 g / cm 3 It was.

[0141] The change rate of reflectance of the thin film 4 of Comparative Example 1 from 13.525 nm to 13.550 nm was -13.2% / nm. The phase shift distribution A of the thin film 4 was 2.88 degrees (>2 degrees), indicating high film thickness dependency. The phase shift distribution B of the thin film 4 was 2.83 degrees (>2 degrees), indicating high density dependency.

[0142] Comparative Example 2 In Comparative Example 2, a multilayer reflective film was formed on the main surface of the same SiO2-TiO2-based glass substrate as in the Example, and a protective film made of a RuNb film was formed on the multilayer reflective film. A lower layer made of TaBN and an upper layer made of CrN were formed on the lower layer to form a thin film on the protective film 3. The conditions for forming the thin film 4 according to Comparative Example 2 are shown below. Lower layer (TaBN film): TaB alloy target, Ar and N2 mixed gas atmosphere, film thickness 4 nm Upper layer (CrN film): Cr target, Ar and N2 mixed gas atmosphere, film thickness 43.1 nm

[0143] The composition (atomic ratio) of the TaBN film was Ta:B:N = 60:15:25. The composition (atomic ratio) of the CrN film was Cr:N = 75:25. The density of the TaBN film was 14.99 g / cm 3 and the density of the CrN film is 8.50 g / cm 3 It was.

[0144] The change rate of reflectance of the thin film 4 of Comparative Example 2 from 13.525 nm to 13.550 nm was 4.7% / nm. The phase shift amount distribution A of the thin film 4 was 4.47 degrees (>2 degrees), indicating high film thickness dependency. The phase shift amount distribution B of the thin film 4 was 3.63 degrees (>2 degrees), indicating high density dependency.

[0145] Comparative Example 3 In Comparative Example 3, a multilayer reflective film was formed on the main surface of the same SiO2-TiO2-based glass substrate as in the Example, and a protective film made of a RuRhCrN film was formed on the multilayer reflective film. A lower layer made of a TaBN film and a TaBO film formed on the TaBN film, and an upper layer made of a RuN film on the lower layer were formed to form a thin film 4. The conditions for forming the thin film 4 according to Comparative Example 3 are as follows. Lower layer (TaBN film): TaB alloy target, Ar and N2 mixed gas atmosphere, film thickness 4 nm Lower layer (TaBO film): TaB alloy target, Ar and O2 mixed gas atmosphere, film thickness 5.2 nm Upper layer (RuN film): Ru target, Ar and N2 mixed gas atmosphere, film thickness 39 nm

[0146] The composition (atomic ratio) of the TaBN film was Ta:B:N=60:15:25. The composition (atomic ratio) of the TaBO film was Ta:B:O=35:5:60. The composition (atomic ratio) of the RuN film was Ru:N=98:2. The density of the TaBN film was 14.99 g / cm 3 The density of the TaBO film is 9.00 g / cm 3 and the density of the RuN film is 13.05 g / cm 3 It was.

[0147] The change rate of reflectance of the thin film 4 of Comparative Example 3 from 13.525 nm to 13.550 nm was 10.4% / nm. The phase shift amount distribution A of the thin film 4 was 3.01 degrees (>2 degrees), indicating high film thickness dependency. The phase shift amount distribution B of the thin film 4 was 2.51 degrees (>2 degrees), indicating high density dependency.

[0148] Comparative Example 4 Comparative Example 4 has a film configuration made of the same materials and composition as Comparative Example 3, but differs from Comparative Example 3 in the thickness of each layer constituting the lower layer and the density of the upper layer. The conditions for forming the thin film in Comparative Example 4 are shown below. Lower layer (TaBN film): TaB alloy target, Ar and N2 mixed gas atmosphere, film thickness 12.7 nm Lower layer (TaBO film): TaB alloy target, Ar and O2 mixed gas atmosphere, film thickness 3.1 nm Upper layer (RuN film): Ru target, Ar and N2 mixed gas atmosphere, film thickness 39 nm

[0149] The composition (atomic ratio) of the RuN film is Ru:N=98:2. The density of the TaBN film is 14.99 g / cm 3 The density of the TaBO film is 9.00 g / cm 3 and the density of the RuN film is 11.86 g / cm 3 It was.

[0150] The change rate of reflectance of the thin film 4 of Comparative Example 4 from wavelength 13.525 nm to 13.550 nm was 10.6% / nm. The phase shift amount distribution A of the thin film 4 was 3.15 degrees (>2 degrees), indicating high film thickness dependency. The phase shift amount distribution B of the thin film 4 was 2.27 degrees (>2 degrees), indicating high density dependency.

[0151] Reflective masks were manufactured from the reflective mask blanks obtained in Comparative Examples 1 to 4, and the transferred images obtained by exposing and transferring the resist film (transfer target) on a semiconductor device with EUV light using the reflective masks were obtained by simulation. In Comparative Examples 1 to 4, the CD in-plane uniformity of the transferred pattern in the transferred image was lower than that in Examples 1 to 10, and the CD in-plane uniformity was insufficient. [Explanation of symbols]

[0152] 1 Board 2 Multilayer reflective film 3 Protective film 4 Phase shift film (thin film) 5 Backside conductive film 100 Reflective mask blank 200 Reflective mask

Claims

1. A substrate; a multilayer reflective film formed on the substrate; a thin film formed on the multilayer reflective film; A reflective mask blank having A reflective mask blank, characterized in that the rate of change in reflectance of the thin film in the light wavelength range of 13.525 nm to 13.550 nm is -12% / nm or more and 4% / nm or less.

2. 2. The reflective mask blank according to claim 1, wherein the thin film is made of a material containing at least one selected from the group consisting of Ru, Cr, Pt and Ta.

3. 2. The reflective mask blank according to claim 1, wherein the thin film is a phase shift film that shifts the phase of incident light.

4. 2. The reflective mask blank according to claim 1, wherein the thin film has a reflectance of 2% or more for EUV light.

5. 2. The reflective mask blank according to claim 1, wherein the rate of change in reflectance is −10% / nm or more.

6. 2. The reflective mask blank according to claim 1, wherein the amount of change in phase shift when the thickness of the thin film varies by 1% or the amount of change in phase shift when the density of the thin film varies by 1% is 2 degrees or less.

7. 2. The reflective mask blank according to claim 1, wherein a wavelength at which the reflectance spectrum of the thin film has a maximum reflectance in the wavelength range of 13 nm to 14 nm is defined as λmax, and an average value of two wavelengths which are closest to 13.53 nm among the wavelengths at which the reflectance is 1 / 2 of the maximum reflectance is defined as CW, and a difference between λmax and CW is 0.05 nm or less.

8. A substrate; a multilayer reflective film formed on the substrate; a thin film provided on the multilayer reflective film and having a transfer pattern formed thereon; A reflective mask having A reflective mask, characterized in that the rate of change in reflectance of the thin film in the range of light wavelengths from 13.525 nm to 13.550 nm is -12% / nm or more and 4% / nm or less.

9. 9. The reflective mask according to claim 8, wherein the thin film is made of a material containing at least one element selected from the group consisting of Ru, Cr, Pt and Ta.

10. 9. The reflective mask according to claim 8, wherein the thin film is a phase shift film that shifts the phase of incident light.

11. 9. The reflective mask according to claim 8, wherein the thin film has a reflectance of 2% or more for EUV light.

12. 9. The reflective mask according to claim 8, wherein the rate of change in reflectance is −10% / nm or more.

13. 9. The reflective mask according to claim 8, wherein the amount of change in phase shift when the thickness of the thin film varies by 1% or the amount of change in phase shift when the density of the thin film varies by 1% is 2 degrees or less.

14. 9. The reflective mask according to claim 8, wherein λmax is a wavelength at which the reflectance spectrum of the thin film has a maximum reflectance in the wavelength range of 13 nm to 14 nm, and CW is an average value of two wavelengths that are closest to 13.53 nm among the wavelengths at which the reflectance is 1 / 2 of the maximum reflectance, and the difference between λmax and CW is 0.05 nm or less.

15. 8. A method for manufacturing a semiconductor device, comprising: exposing and transferring a transfer pattern onto a transfer target on a semiconductor substrate using a reflective mask having a transfer pattern manufactured using the reflective mask blank according to claim 1.

16. 15. A method for manufacturing a semiconductor device, comprising: exposing and transferring the transfer pattern onto a transfer target on a semiconductor substrate using a reflective mask according to claim 8.

Images