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

Abstract

To provide a reflective mask blank for manufacturing a reflective mask having a transfer pattern capable of forming a transfer pattern of a diversified fine pattern shape formed on a substrate to be transferred and performing EUV exposure with high throughput.SOLUTION: A reflective mask blank comprising a multilayer reflective film and an absorber film in this order on a substrate, wherein when an evaluation function value of a film having a refractive index of 0.95 and an extinction coefficient of 0.03 is normalized as 1, the absorber film comprises a material having a refractive index and an extinction coefficient such that the normalized evaluation function value of the absorber film is 1.015 or more, and the evaluation function is a product of a normalized image log slope (NILS) and a threshold value of light intensity for exposure of a predetermined resist.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a reflective mask blank, which is an original plate for producing an exposure mask used in the manufacture of a semiconductor device, a reflective mask, and a method for manufacturing a semiconductor device using the reflective mask. [Background technology]

[0002] The types of light sources used in exposure equipment for semiconductor device manufacturing have evolved with gradually shorter wavelengths, from g-line (436 nm), i-line (365 nm), KrF laser (248 nm), and ArF laser (193 nm). To achieve finer pattern transfer, extreme ultraviolet (EUV) lithography using EUV light with wavelengths around 13.5 nm has been developed. Because few materials are transparent to EUV light, reflective masks are used in EUV lithography. Reflective masks have a multilayer reflective film on a low-thermal expansion substrate to reflect exposure light. Reflective masks have a basic mask structure in which a desired transfer pattern is formed on a protective film to protect the multilayer reflective film. Based on the structure of the transfer pattern, representative reflective masks are binary reflective masks and phase-shift reflective masks (halftone phase-shift reflective masks). The transfer pattern of a binary reflective mask consists of a relatively thick absorber pattern that sufficiently absorbs EUV light. The transfer pattern of a phase-shift reflective mask consists of a relatively thin absorber pattern that attenuates EUV light through optical absorption and generates reflected light that is almost phase-inverted (approximately 180° phase inversion) relative to the light reflected from the multilayer reflective film. Similar to transmissive optical phase-shift masks, phase-shift reflective masks (halftone phase-shift reflective masks) achieve high transfer optical image contrast through the phase shift effect, thereby improving resolution. Furthermore, the thin film thickness of the absorber pattern (phase shift pattern) of a phase-shift reflective mask allows for the formation of fine phase-shift patterns with high precision.

[0003] EUV lithography uses a projection optical system consisting of many reflecting mirrors due to light transmittance considerations. By making the EUV light incident on the reflective mask at an angle, these multiple reflecting mirrors are prevented from blocking the projection light (exposure light). Currently, the incident angle is typically set at 6° relative to the perpendicular plane of the reflective mask substrate. As the numerical aperture (NA) of the projection optical system improves, studies are underway to increase the angle to a more oblique incidence of around 8°.

[0004] EUV lithography has an inherent problem called the shadowing effect, because the exposure light is incident at an angle. The shadowing effect is a phenomenon in which a shadow is cast when the exposure light is incident at an angle on an absorber pattern with a three-dimensional structure, changing the dimensions and position of the transferred pattern. The three-dimensional structure of the absorber pattern acts as a wall, casting a shadow on the shaded side, changing the dimensions and / or position of the transferred pattern. For example, differences in the dimensions and position of the transferred pattern occur when the absorber pattern is oriented parallel to the direction of the obliquely incident light and perpendicular to it, reducing transfer accuracy.

[0005] Such reflective masks for EUV lithography and techniques related to mask blanks for fabricating them are disclosed in Patent Documents 1 and 2. Patent Document 1 also describes the provision of a reflective mask that has a small shadowing effect, is capable of phase shift exposure, and has sufficient light-shielding frame performance. Conventionally, by using a phase-shift reflective mask as a reflective mask for EUV lithography, the film thickness of the phase shift pattern is made relatively thinner than in the case of a binary reflective mask, thereby suppressing the deterioration of transfer accuracy due to the shadowing effect.

[0006] Patent Document 3 describes a mask for EUV lithography. Specifically, the mask described in Patent Document 3 includes a substrate, a multilayer coating applied to the substrate, and a mask structure having an absorber material applied to the multilayer coating. Patent Document 3 describes that the mask structure has a maximum thickness of less than 100 nm.

[0007] Patent Document 4 describes a method for producing an extreme ultraviolet (EUV) mask blank. Specifically, Patent Document 4 describes that the method includes providing a substrate, forming a stack of multiple reflective layers on the substrate, forming a capping layer on the stack of multiple reflective layers, and forming an absorbing layer on the capping layer. Patent Document 4 also describes that the absorbing layer includes an alloy of at least two different absorbing materials. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-212220 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-39884 [Patent Document 3] Special Publication No. 2013-532381 [Patent Document 4] Special Publication No. 2019-527382 DISCLOSURE OF THE INVENTION

[0009] In EUV lithography, a transfer pattern formed on a reflective mask is used to transfer a resist transfer pattern onto a resist layer formed on a transfer substrate (semiconductor substrate).The resist transfer pattern is used to form a predetermined fine circuit on a semiconductor device.

[0010] To improve the electrical characteristics, increase integration density, and reduce chip size of semiconductor devices, it is necessary to further refine transfer patterns, i.e., to reduce the dimensions of the transfer patterns and improve the positional accuracy of the transfer patterns. Therefore, EUV lithography is required to have transfer performance capable of transferring transfer patterns with even higher precision than conventional methods. Currently, there is a demand for ultrafine, high-precision transfer pattern formation compatible with the hp16nm (half pitch 16nm) generation. To meet these demands, the transfer patterns formed on reflective masks are also required to be further refined. Furthermore, to reduce the shadowing effect during EUV exposure, the thin films constituting the transfer patterns of reflective masks are required to be further thinned. Specifically, the thickness of the absorber film (phase shift film) of reflective masks is required to be 50 nm or less.

[0011] Furthermore, as the transfer patterns become finer, the shapes of the transfer patterns become more diverse, and therefore, reflective masks are required to have absorber films for forming transfer patterns that can accommodate the diversified pattern shapes.

[0012] Furthermore, in order to manufacture semiconductor devices at low cost, it is required to be able to perform EUV exposure in EUV lithography with high throughput.

[0013] As disclosed in Patent Documents 1 and 2, Ta has traditionally been used as a material for forming the absorber film (phase shift film) of a reflective mask blank. However, because the refractive index (n) of Ta for EUV light (e.g., wavelength 13.5 nm) is approximately 0.943, even when utilizing its phase shift effect, the thickness of an absorber film (phase shift film) formed solely from Ta is limited to 60 nm. To achieve even thinner films, for example, metal materials with a high extinction coefficient (k) (high absorption effect) can be used as the absorber film of a binary type reflective mask blank. For example, Patent Documents 3 and 4 describe platinum (Pt) and iridium (Ir) as metal materials with a high extinction coefficient (k) at a wavelength of 13.5 nm.

[0014] However, while a high extinction coefficient (k) of the absorber film alone can meet the demand for thinner absorber films in reflective masks, it has proven difficult to accommodate the increasing diversity of pattern shapes of the transfer patterns formed on the transfer substrate.Furthermore, it has been difficult to meet the demand for high throughput EUV exposure.

[0015] In view of the above, an object of the present invention is to provide a reflective mask blank for manufacturing a reflective mask having a transfer pattern that is capable of forming transfer patterns of a variety of fine patterns on a transfer substrate and that can perform EUV exposure with high throughput.

[0016] Another object of the present invention is to provide a reflective mask having a transfer pattern that is capable of forming a transfer pattern of a variety of fine patterns on a transfer substrate and that enables EUV exposure to be performed with high throughput. Another object of the present invention is to provide a semiconductor device manufacturing method that is capable of forming a variety of fine patterns on a transfer substrate with high throughput.

[0017] In order to solve the above problems, an embodiment of the present invention has the following configuration.

[0018] (Configuration 1) Configuration 1 of this embodiment is a reflective mask blank having a multilayer reflective film and an absorber film in this order on a substrate, when the value of an evaluation function of a film having a refractive index of 0.95 and an extinction coefficient of 0.03 with respect to EUV light having a wavelength of 13.5 nm is normalized to 1, the absorber film includes a material having a refractive index and an extinction coefficient such that the normalized value of the evaluation function of the absorber film is 1.015 or more, The reflective mask blank is characterized in that the evaluation function is the product of the normalized image logarithmic slope (NILS) and the threshold light intensity for exposure of a predetermined resist.

[0019] (Configuration 2) Configuration 2 of this embodiment is a reflective mask blank according to configuration 1, characterized in that the reflective mask blank is used to produce a reflective mask having a transfer pattern including lines and spaces for the LOGIC hp 16 nm generation and later.

[0020] (Configuration 3) Configuration 3 of this embodiment is the reflective mask blank according to configuration 1 or 2, characterized in that the refractive index of the material of the absorber film with respect to EUV light having a wavelength of 13.5 nm is in the range of 0.86 to 0.95, and the extinction coefficient of the material of the absorber film with respect to EUV light having a wavelength of 13.5 nm is in the range of 0.015 to 0.065.

[0021] (Configuration 4) A fourth aspect of the present embodiment is the reflective mask blank according to any one of the first to third aspects, wherein the material of the absorber film contains at least one selected from iridium (Ir) and ruthenium (Ru).

[0022] (Configuration 5) Configuration 5 of this embodiment is a reflective mask blank according to any one of configurations 1 to 3, characterized in that the material of the absorber film contains iridium (Ir) and at least one selected from boron (B), silicon (Si), ruthenium (Ru), tantalum (Ta), and oxygen (O).

[0023] (Configuration 6) A sixth aspect of the present embodiment is the reflective mask blank according to any one of the first to fifth aspects, wherein the material of the absorber film contains platinum (Pt).

[0024] (Configuration 7) A seventh aspect of the present embodiment is the reflective mask blank according to any one of the first to fifth aspects, wherein the material of the absorber film contains gold (Au).

[0025] (Configuration 8) The eighth embodiment of the present invention has a protective film between the multilayer reflective film and the absorber film, The reflective mask blank according to any one of configurations 1 to 7, wherein the protective film is made of a material containing ruthenium (Ru) or silicon (Si).

[0026] (Configuration 9) A ninth aspect of the present invention is a reflective mask characterized in that the absorber film of the reflective mask blank of any one of the first to eighth aspects has an absorber pattern formed by patterning.

[0027] (Configuration 10) Configuration 10 of the present invention is a method for manufacturing a semiconductor device, comprising the steps of setting the reflective mask according to Configuration 9 in an exposure apparatus having an exposure light source that emits EUV light, and transferring a transfer pattern to a resist layer formed on a transfer substrate.

[0028] According to an embodiment of the present invention, it is possible to provide a reflective mask blank for manufacturing a reflective mask having a transfer pattern that is capable of forming transfer patterns of a variety of fine patterns on a transfer substrate and that can perform EUV exposure with high throughput.

[0029] Furthermore, according to an embodiment of the present invention, it is possible to provide a reflective mask having a transfer pattern that is capable of forming a transfer pattern of diversified fine patterns on a transfer substrate and that allows EUV exposure to be performed with high throughput. Also, according to an embodiment of the present invention, it is possible to provide a semiconductor device manufacturing method that is capable of forming a transfer pattern of diversified fine patterns on a transfer substrate with high throughput. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a schematic cross-sectional view of a main part for explaining the general configuration of a reflective mask blank of the present invention. FIG. [Figure 2A-D] 2A to 2D are process drawings showing, in schematic cross-sectional views of essential parts, steps for producing a reflective mask from a reflective mask blank. [Figure 3] FIG. 10 is a diagram showing the values ​​of the normalized evaluation function obtained by the simulation of Example 1-1, and is a diagram showing the distribution of the values ​​of the normalized evaluation function with respect to the refractive index (n) and extinction coefficient (k) of the absorber film when the reflective mask has a vertical L / S (line and space) pattern of hp 16 nm and uses a RuNb film as the protective film (Cap film). [Figure 4] FIG. 10 is a diagram showing the values ​​of the normalized evaluation function obtained by the simulation of Example 1-2, and is a diagram showing the distribution of the values ​​of the normalized evaluation function with respect to the refractive index (n) and extinction coefficient (k) of the absorber film when the reflective mask has a vertical L / S pattern with hp of 16 nm and uses a RuRh film as the protective film. [Figure 5] FIG. 10 is a diagram showing the values ​​of the normalized evaluation function obtained by the simulation of Example 1-1, and is a diagram showing the distribution of the values ​​of the normalized evaluation function with respect to the refractive index (n) and extinction coefficient (k) of the absorber film when the reflective mask has a horizontal L / S pattern with hp of 16 nm and uses a RuNb film as the protective film. [Figure 6]FIG. 10 is a diagram showing the values ​​of the normalized evaluation function obtained by the simulation of Example 1-2, and is a diagram showing the distribution of the values ​​of the normalized evaluation function with respect to the refractive index (n) and extinction coefficient (k) of the absorber film when the reflective mask has a horizontal L / S pattern with hp of 16 nm and uses a RuRh film as the protective film. [Figure 7] FIG. 10 is a diagram showing the values ​​of the normalized evaluation function obtained by the simulation of Example 1-1, and is a diagram showing the distribution of the values ​​of the normalized evaluation function with respect to the refractive index (n) and extinction coefficient (k) of the absorber film when the reflective mask has a pattern of contact holes with a diameter of 24 nm and uses a RuNb film as the protective film. [Figure 8] FIG. 5 is a diagram combining distributions of normalized evaluation function values ​​of the vertical L / S patterns shown in FIGS. 3 and 4, showing binarized distributions when the values ​​of the normalized evaluation functions shown in FIGS. 3 and 4 are both 1.015 or more (white) and when they are not (black). [Figure 9] FIG. 7 is a diagram combining distributions of normalized evaluation function values ​​of the horizontal L / S patterns shown in FIGS. 5 and 6, showing binarized distributions when the values ​​of the normalized evaluation functions shown in FIGS. 5 and 6 are both 1.015 or more (white) and other cases (black). [Figure 10] FIG. 8 is a diagram showing the distribution of normalized evaluation function values ​​of the contact hole pattern shown in FIG. 7, binarized into cases where the evaluation function value is 1.015 or more (white) and cases where the evaluation function value is less than 1.015 (black). [Figure 11] FIG. 11 is a diagram combining distributions of the binarized normalized evaluation function values ​​shown in FIGS. 8 to 10, showing distributions when all values ​​of the normalized evaluation function shown in FIGS. 8 to 10 are 1.015 or more (white) and distributions in other cases (black). DETAILED DESCRIPTION OF THE INVENTION

[0031] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Note that the following embodiment is one form for realizing 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 their description may be simplified or omitted.

[0032] 1, the reflective mask blank 100 of this embodiment is a reflective mask blank 100 having a multilayer reflective film 2 and an absorber film 4 in this order on a substrate 1. The reflective mask blank 100 of this embodiment can also have a protective film 3 between the multilayer reflective film 2 and the absorber film 4.

[0033] 2D, the reflective mask 200 of this embodiment has a multilayer reflective film 2 and an absorber film pattern 4a in this order on a substrate 1. The reflective mask 200 of this embodiment can also have a protective film 3 between the multilayer reflective film 2 and the absorber film pattern 4a and on the surface of the multilayer reflective film 2.

[0034] In this specification, "L / S (line and space) pattern for the LOGIC hp16 nm generation or later" means an L / S (line and space) pattern with a half pitch (hp) of hp16 nm or less.

[0035] In this specification, the term "Normalized Image Log Slope (NILS)" refers to the following formula 1. In formula 1, W (unit: nm) indicates the pattern size, and I indicates the light intensity. "I=I threshold " indicates that the differential is a predetermined differential value at a location corresponding to the edge of a pattern of pattern size W (i.e., a location where the light intensity is at a threshold value, which will be described later). Note that in this specification, the normalized image logarithmic gradient may be simply referred to as "NILS."

[0036] (Formula 1)

number

[0037] The normalized image logarithmic slope (NILS) represents the magnitude of the slope when the horizontal axis represents position and the vertical axis represents the logarithm of the light intensity of the exposure light. In other words, the higher the NILS, the higher the contrast. In EUV lithography, a predetermined transfer pattern is transferred to a resist layer on a transfer substrate. The resist in the resist layer is exposed to light according to the dose of exposure light (light intensity multiplied by time). Therefore, when the exposed resist is developed, the higher the contrast (NILS), the greater the slope of the shape of the pattern edge of the transferred pattern. If the slope of the shape of the pattern edge is steep, the dependence of the position of the pattern edge on the dose of exposure light is reduced. Therefore, even if the dose fluctuates, the change in the shape of the transferred pattern is small. Therefore, a high normalized image logarithmic slope (NILS) is preferable to obtain fine and highly accurate transferred patterns. Furthermore, it can be said that the higher the normalized image logarithmic slope (NILS), the more diverse and fine patterns can be formed on the transfer substrate.

[0038] The normalized image logarithmic slope (NILS) varies depending on the material and shape of the absorber pattern 4a of the reflective mask 200. This is because, during the exposure process, the light intensity and distribution of the reflected exposure light reflected by the reflective mask 200 and projected onto the transfer substrate are affected by the material and shape of the absorber pattern 4a of the reflective mask 200. More specifically, the normalized image logarithmic slope (NILS) depends on the refractive index (n) and extinction coefficient (k) of the material of the absorber pattern 4a, the film thickness of the absorber pattern 4a, and other factors. Therefore, a reflective mask 200 having an absorber pattern 4a made of a predetermined material can be said to have a predetermined normalized image logarithmic slope (NILS). Furthermore, since the material and film thickness of the absorber pattern 4a in the reflective mask 200 affect the normalized image logarithmic slope (NILS), the normalized image logarithmic slope (NILS) can be understood depending on the material and film thickness of the absorber film 4. Furthermore, when the film thickness is optimized, the normalized image logarithmic slope (NILS) can be considered depending on the material of the absorber film 4. Therefore, in this specification, the normalized image logarithmic slope (NILS) in the exposure process using a predetermined reflective mask 200 may be referred to as the normalized image logarithmic slope (NILS) of the reflective mask 200 (having an absorber pattern 4a of a predetermined material) or the normalized image logarithmic slope (NILS) of the reflective mask blank 100 (having an absorber film 4 of a predetermined material).

[0039] As used herein, the term "threshold" refers to the light intensity at which a resist is exposed to light at a predetermined hp during EUV exposure to form a resist transfer pattern of a line-and-space pattern (sometimes referred to simply as "L / S") with a predetermined half pitch (sometimes referred to simply as "hp"). For example, in a graph (aerial image) with the vertical axis representing light intensity and the horizontal axis representing the hp of the L / S, the "threshold" refers to the light intensity at which a resist is exposed to light at a predetermined hp. Specifically, for example, when a negative photosensitive material is used as the resist, the threshold refers to the light intensity at which the negative photosensitive material becomes completely insoluble when exposed to a predetermined light intensity and then developed. The higher the threshold, the lower the dose of exposure light required during EUV exposure, resulting in a higher throughput of the EUV exposure process. Therefore, a high threshold is preferable to increase the throughput of the EUV exposure process.

[0040] The threshold value varies depending on the photosensitivity of the resist layer on the transfer substrate and the shape of the transfer pattern (specifically, the half pitch (hp) of the L / S). In the exposure process, the shape of the transfer pattern (resist transfer pattern) transferred onto the transfer substrate depends on the light intensity and its distribution of the reflected exposure light that is reflected by the reflective mask 200 and projected onto the transfer substrate. The light intensity and its distribution of the reflected exposure light are affected by the material and shape of the absorber pattern 4a of the reflective mask 200. More specifically, the threshold value varies depending on the refractive index (n) and extinction coefficient (k) of the material of the absorber pattern 4a, the film thickness of the absorber pattern 4a, and the shape of the absorber pattern 4a, such as the hp of the L / S. Therefore, it can be said that the reflective mask 200 has a predetermined threshold value. Furthermore, for the same hp of the L / S, the material and film thickness of the absorber pattern 4a in the reflective mask 200 affect the threshold value, so the threshold value can be considered depending on the material and film thickness of the absorber film 4. Furthermore, when the film thickness is optimized, the threshold can be considered depending on the material of the absorber film 4. Therefore, in this specification, the threshold in the exposure process using a predetermined reflective mask 200 may be referred to as the threshold of the reflective mask 200 (having an absorber pattern 4a of a predetermined material) or the threshold of the reflective mask blank 100 (having an absorber film 4 of a predetermined material).

[0041] In this specification, the "evaluation function" is the product of the normalized image logarithmic slope (NILS) and the threshold light intensity for the exposure of a given resist. The larger the value of the evaluation function of the reflective mask 200 having the absorber pattern 4a of a given material, the more diverse and fine pattern shapes can be formed on the transfer substrate (resist transfer pattern), and the higher the throughput of EUV exposure can be.

[0042] In this specification, the term "normalized evaluation function" refers to the ratio of the evaluation function values ​​obtained by normalizing the evaluation function value of a comparison film to the evaluation function value of a reflective mask 200 using, as the absorber pattern 4a, a pattern (reference film pattern) of a film (referred to as a "reference film" in this specification) having a refractive index (n) of 0.95 for EUV light with a wavelength of 13.5 nm and an extinction coefficient (k) of 0.03, which is set to 1.

[0043] Currently, films containing Ta, such as TaBN and TaN films, are often used as the absorber film 4 of the reflective mask 200. The refractive index (n) of TaBN and TaN films is approximately 0.95, and the extinction coefficient (k) is approximately 0.03. Therefore, a film with a refractive index (n) of 0.95 for EUV light with a wavelength of 13.5 nm and an extinction coefficient (k) of 0.03 was selected as the reference film for calculating the value of the normalized evaluation function. The value of the normalized evaluation function is the ratio of the value of the evaluation function of a reflective mask 200 having a reference film pattern (reference film pattern) to the value of the evaluation function of a reflective mask 200 having a comparative absorber pattern 4a. As mentioned above, the value of the evaluation function is essentially a value obtained as the product of the normalized image logarithmic slope (NILS) and a threshold light intensity when a transfer pattern is transferred to a resist layer on a transfer substrate using a specific reflective mask 200. On the other hand, when the transfer patterns have the same pattern shape (i.e., when the transfer patterns of the reflective mask 200 have the same pattern shape), the normalized image logarithmic slope (NILS) and threshold can be considered as the threshold of the material of the absorber film 4 that constitutes the transfer pattern of the reflective mask 200. Therefore, the value of the evaluation function can also be considered with respect to the material of the absorber film 4. For this reason, in this specification, it may be referred to as the value of the evaluation function (or normalized evaluation function) of a predetermined absorber film 4 or the value of the evaluation function of a reference film. Similarly, it may be referred to as the value of the evaluation function (or normalized evaluation function) of the reflective mask 200 (having an absorber pattern 4a of a predetermined material) or the value of the evaluation function (or normalized evaluation function) of the reflective mask blank 100 (having an absorber film 4 of a predetermined material).

[0044] For the reasons described above, in this specification, the evaluation function of the reflective mask 200 using the pattern of the reference film (reference film pattern) as the absorber pattern 4a may be simply referred to as the evaluation function of the reference film.

[0045] The larger the value of the normalized evaluation function of the reflective mask 200 having the absorber pattern 4a of a predetermined material, the more diverse and fine pattern shapes can be formed on the transfer substrate, and the higher the throughput of EUV exposure can be, compared to the reflective mask 200 having the absorber pattern 4a of the reference film.

[0046] The present inventors focused on the relationship between the normalized image logarithmic slope (NILS), threshold value, and film thickness to find the optimal refractive index (n) and extinction coefficient (k) of the absorber film 4 that can accommodate a variety of pattern shapes, and arrived at the present invention. Specifically, in order to select an absorber film 4 that brings the value of the above-mentioned normalized evaluation function into a predetermined range, the inventors discovered that by forming the absorber film 4 using a material having a predetermined refractive index (n) and extinction coefficient (k), it is possible to form transfer patterns of a variety of fine pattern shapes on a transfer substrate, and to manufacture a reflective mask 200 having a transfer pattern that allows EUV exposure to be performed with high throughput, and thus arrived at the present invention.

[0047] Next, the reflective mask blank 100 of the present invention will be described.

[0048] This embodiment is a reflective mask blank 100 having a multilayer reflective film 2 and an absorber film 4 on a substrate 1 in this order.

[0049] The absorber film 4 of the reflective mask blank 100 of this embodiment contains a material having a refractive index and an extinction coefficient such that the value of the normalized evaluation function (normalized evaluation function) of the absorber film 4 is 1.015 or more. Note that the "normalized evaluation function of the absorber film 4" refers to the normalized evaluation function in the exposure process of the reflective mask 200 when the reflective mask blank 100 is manufactured using the absorber film 4 and then the reflective mask 200 is manufactured. When the reflective mask 200 serving as the standard for normalization and the reflective mask 200 to be normalized are used in the exposure process under the same conditions, and the only difference between them is the absorber film 4 (material and film thickness), the absorber film 4 can be identified without causing any misunderstanding even if the expression "normalized evaluation function of the absorber film 4" is used.

[0050] As described above, the evaluation function is the product of the normalized image logarithmic slope (NILS) and the threshold light intensity for the exposure of a given resist. The value of the normalized evaluation function is the value of the evaluation function normalized by the value of the evaluation function of the reference film. The upper limit of the value of the normalized evaluation function can be determined according to the requirement for finer transfer patterns. To enable the selection of a realistic material for the absorber film 4, the upper limit of the value of the normalized evaluation function is preferably 2.0 or less, more preferably 1.7 or less.

[0051] The value of the normalized evaluation function is preferably 1.015 or more when the transfer pattern is a vertical L / S (line and space) pattern, a horizontal L / S pattern, or a contact hole pattern. In this case, it is considered that the exposure performance will be superior to that when a Ta-based absorber film 4, which is currently the mainstream, is used.

[0052] The vertical L / S pattern refers to an L / S pattern in which incident light is incident on the reflective mask 200 so that the normal to a plane including the incident light and reflected light on the reflective mask 200 is perpendicular to the direction of the lines of the L / S pattern. The horizontal L / S pattern refers to an L / S pattern in which incident light is incident on the reflective mask 200 so that the normal to a plane including the incident light and reflected light on the reflective mask 200 is parallel to the direction of the lines of the L / S pattern.

[0053] The reflective mask blank 100 of this embodiment is preferably used to produce a reflective mask 200 having a transfer pattern including LOGIC hp 16 nm lines and spaces. This is because, by using the reflective mask blank 100 of this embodiment, it is possible to form transfer patterns of a variety of fine patterns to be formed on a transfer substrate, and it is also possible to manufacture a reflective mask 200 having a transfer pattern that allows EUV exposure to be performed with high throughput.

[0054] Next, the films that constitute the reflective mask blank 100 of this embodiment will be specifically described.

[0055] <Configuration of Reflective Mask Blank 100 and Its Manufacturing Method> 1 is a schematic cross-sectional view of a main portion for explaining the configuration of a reflective mask blank 100 according to an embodiment of the present invention. As shown in the figure, the reflective mask blank 100 has a substrate 1, a multilayer reflective film 2 formed on a first main surface (front surface) side that reflects EUV light, which is exposure light, a protective film 3 provided to protect the multilayer reflective film 2, and an absorber film 4 that absorbs EUV light, which are laminated in this order. In addition, a back surface conductive film 5 for use in an electrostatic chuck is formed on a second main surface (back surface) side of the substrate 1.

[0056] The reflective mask blank 100 also includes a configuration in which no rear surface conductive film 5 is formed. Furthermore, the reflective mask blank 100 also includes a configuration of a mask blank with a resist film in which a resist film 11 is formed on an etching mask film.

[0057] In this specification, for example, the expression "multilayer reflective film 2 formed on substrate 1" not only means that multilayer reflective film 2 is disposed in contact with the surface of substrate 1, but also means that there is another film between substrate 1 and multilayer reflective film 2. The same applies to other films. In addition, in this specification, for example, "film A is disposed on film B in contact with film B" means that film A and film B are disposed so as to be in direct contact with each other, with no other film interposed between them.

[0058] Each component of the reflective mask blank 100 will be specifically described below.

[0059] <<Board 1>> To prevent distortion of the absorber pattern 4a due to heat during exposure to EUV light, the substrate 1 preferably has a low thermal expansion coefficient within the range of 0±5 ppb / ° C. Materials having a low thermal expansion coefficient within this range include, for example, SiO2-TiO2-based glass and multi-component glass ceramics.

[0060] The first main surface of the substrate 1 on which the transfer pattern (which is constituted by patterning the absorber film 4 described below) is formed is surface-processed to have a high degree of flatness in order to ensure 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 area of ​​the main surface of the substrate 1 on which the transfer pattern is formed. Furthermore, the second main surface opposite the side on which the absorber film 4 is formed is the surface that is electrostatically chucked when set in an exposure tool, and the flatness is preferably 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less, in a 142 mm × 142 mm area.

[0061] The surface smoothness of the substrate 1 is also an extremely important factor. The surface roughness of the first main surface of the substrate 1 on which the transfer pattern (absorber pattern 4a) is formed is preferably 0.1 nm or less in root mean square roughness (RMS). The surface smoothness can be measured using an atomic force microscope.

[0062] Furthermore, the substrate 1 preferably has high rigidity to prevent deformation due to film stress of films (such as the multilayer reflective film 2) formed thereon. In particular, it is preferable that the substrate 1 has a high Young's modulus of 65 GPa or more.

[0063] <<Multilayer reflective film 2>> The multilayer reflective film 2 provides the reflective mask 200 with the function of reflecting EUV light, and is configured as a multilayer film in which layers each containing elements with different refractive indices as main components are periodically stacked.

[0064] Typically, the multilayer reflective film 2 is a multilayer film formed by alternately stacking approximately 40 to 60 thin films (high-refractive index layers) of a light element or its compound, which is a high-refractive index material, and thin films (low-refractive index layers) of a heavy element or its compound, which is a low-refractive index material. The multilayer film may be stacked multiple times, with one cycle consisting of a high-refractive index layer / low-refractive index layer stacked in that order from the substrate 1 side. The multilayer film may also be stacked multiple times, with one cycle consisting of a low-refractive index layer / high-refractive index layer stacked in that order from the substrate 1 side. The topmost layer of the multilayer reflective film 2, i.e., the surface layer of the multilayer reflective film 2 opposite the substrate 1, is preferably a high-refractive index layer. In the above-described multilayer film, when multiple cycles consisting of a high-refractive index layer / low-refractive index layer stacked in that order from the substrate 1 side are stacked, the topmost layer is a low-refractive index layer. In this case, if a low-refractive index layer constitutes the topmost surface of the multilayer reflective film 2, it is easily oxidized, reducing the reflectivity of the reflective mask 200. 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, when a low refractive index layer and a high refractive index layer are stacked in this order from the substrate 1 side, forming a low refractive index layer / high refractive index layer stack structure as one cycle, the uppermost layer is the high refractive index layer and may be left as is.

[0065] In this embodiment, a layer containing silicon (Si) is used as the high-refractive index layer. The Si-containing material may be elemental 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 reflectivity for 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. The low-refractive index layer is preferably a metal selected from molybdenum (Mo), ruthenium (Ru), rhodium (Rh), and platinum (Pt), or an alloy thereof. For example, a Mo / Si periodic stacked film, in which Mo and Si films are alternately stacked for approximately 40 to 60 periods, is preferably used as the multilayer reflective film 2 for EUV light with a wavelength of 13 to 14 nm. Alternatively, the high refractive index layer, which is the uppermost layer of the multilayer reflective film 2, may be made of silicon (Si), and a silicon oxide layer containing silicon and oxygen may be formed between the uppermost layer (Si) and the Ru-based protective film 3. This can improve mask cleaning resistance.

[0066] The reflectance of such a multilayer reflective film 2 alone is typically 65% ​​or higher, with an upper limit of typically 73%. The thickness and period of each constituent layer of the multilayer reflective film 2 can be appropriately selected depending on the exposure wavelength, and are selected so as to satisfy the law of Bragg reflection. The multilayer reflective film 2 contains multiple high-refractive index layers and multiple low-refractive index layers. The high-refractive index layers and the low-refractive index layers do not need to have the same thickness. The thickness of the Si layer on the top surface of the multilayer reflective film 2 can be adjusted within a range that does not reduce the reflectance. The thickness of the Si (high-refractive index layer) on the top surface can be set to 3 nm to 10 nm.

[0067] Methods for forming the reflective multilayer film 2 are well known in the art. For example, the reflective multilayer film 2 can be formed by depositing each layer by ion beam sputtering. In the case of the Mo / Si periodic multilayer film described above, a Si film having a thickness of approximately 4 nm is first deposited on the substrate 1 using a Si target by ion beam sputtering. Then, a Mo film having a thickness of approximately 3 nm is deposited using a Mo target. Each Si film and Mo film constitutes one period, and 40 to 60 periods are stacked to form the reflective multilayer film 2 (the outermost layer is a Si layer). Furthermore, during the deposition of the reflective multilayer film 2, it is preferable to supply krypton (Kr) ion particles from an ion source and perform ion beam sputtering to form the reflective multilayer film 2. It is preferable that the reflective multilayer film 2 have approximately 40 periods, considering the improvement in reflectivity due to the increased number of stacking periods and the reduction in throughput due to the increased number of processes. However, the number of stacking periods of the reflective multilayer film 2 is not limited to 40 periods and may be, for example, 60 periods. In the case of 60 cycles, the number of processes increases compared to 40 cycles, but the reflectivity to EUV light can be increased.

[0068] <<Protective film 3>> The reflective mask blank 100 of this embodiment preferably has a protective film 3 between the multilayer reflective film 2 and the absorber film 4. Forming the protective film 3 on the multilayer reflective film 2 makes it possible to suppress damage to the surface of the multilayer reflective film 2 when manufacturing a reflective mask 200 (EUV mask) using the reflective mask blank 100. Therefore, forming the protective film 3 improves the reflectance characteristics for EUV light.

[0069] The protective film 3 is formed on the multilayer reflective film 2 to protect the multilayer reflective film 2 from dry etching and cleaning in the manufacturing process of the reflective mask 200, which will be described later. It also serves to protect the multilayer reflective film 2 when repairing opaque defects in the absorber pattern 4a using an electron beam (EB). The protective film 3 is formed of a material that is resistant to etchants, cleaning solutions, and the like. While FIG. 1 shows the protective film 3 as a single layer, it may also have a laminated structure of three or more layers. For example, the protective film 3 may have a bottom layer and a top layer made of the Ru-containing material, with a metal or alloy other than Ru interposed between the bottom layer and the top layer. For example, the protective film 3 may be made of a material containing ruthenium as a main component. That is, the material of the protective film 3 may be Ru metal alone, or may be a Ru alloy 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 may also contain nitrogen. Such a protective film 3 is particularly effective when the absorber film 4 is patterned by dry etching using a chlorine-based gas (Cl-based gas). The protective film 3 is preferably formed from a material that provides an etching selectivity ratio of the absorber film 4 to the protective film 3 (etching rate of the absorber film 4 / etching rate of the protective film 3) of 1.5 or more, preferably 3 or more, in dry etching using a chlorine-based gas.

[0070] When the material of the protective film 3 is a Ru alloy, the Ru content of the Ru alloy 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 particular, when the Ru content of the Ru alloy is 95 atomic % or more and less than 100 atomic %, sufficient reflectance for EUV light can be ensured while suppressing diffusion of the constituent element (silicon) of the multilayer reflective film 2 into the protective film 3. Furthermore, this protective film 3 can have mask cleaning resistance, an etching stopper function when the absorber film 4 (specifically, the buffer layer 42) is etched, and the protective film 3 function of preventing deterioration of the multilayer reflective film 2 over time.

[0071] The material of the protective film 3 may be a material containing silicon (Si). The material containing silicon (Si) may be, for example, silicon (Si), silicon oxide (SiO, SiO2, Si3O2, etc. x O y (x and y are integers of 1 or more)), silicon nitride (SiN and Si3N4, etc. x N y (x and y are integers of 1 or more)), and silicon oxynitride (Si such as SiON) x O y N z (x, y, and z are integers of 1 or more). Such a protective film 3 is particularly effective when the absorber film 4 is patterned by dry etching with a chlorine-based gas (Cl-based gas) containing oxygen gas. The protective film 3 is preferably formed from a material that gives an etching selectivity ratio of the absorber film 4 to the protective film 3 (etching rate of the absorber film 4 / etching rate of the protective film 3) of 1.5 or more, preferably 3 or more, in dry etching using a chlorine-based gas containing oxygen gas.

[0072] In the reflective mask blank 100 of this embodiment, the protective film 3 is preferably made of a material containing ruthenium (Ru) or silicon (Si). When the protective film 3 is made of a material containing ruthenium (Ru) (for example, simple Ru or a Ru alloy), damage to the surface of the multilayer reflective film 2 can be effectively suppressed. Furthermore, when the protective film 3 is made of a material containing silicon (Si), the degree of freedom in selecting the material of the absorber film 4 can be increased.

[0073] In EUV lithography, few materials are transparent to the exposure light, making it technically difficult to develop an EUV pellicle to prevent foreign particles from adhering to the mask pattern surface. For this reason, pellicle-less operation has become mainstream. Furthermore, EUV lithography can cause exposure contamination, such as the deposition of carbon films and the growth of oxide films on the mask during EUV exposure. Therefore, when using the EUV reflective mask 200 in semiconductor device manufacturing, it must be frequently cleaned to remove foreign particles and contamination from the mask. Therefore, the EUV reflective mask 200 requires significantly higher mask cleaning resistance than transmissive masks used in optical lithography. The use of a Ti-containing Ru-based protective film 3 provides particularly high cleaning resistance to cleaning solutions such as sulfuric acid, sulfuric acid hydrogen peroxide (SPM), ammonia, ammonia hydrogen peroxide (APM), OH radical cleaning water, and ozone water with a concentration of 10 ppm or less, thereby satisfying the mask cleaning resistance requirements.

[0074] The thickness of the protective film 3 made of ruthenium (Ru) or an alloy thereof, silicon (Si), or the like is not particularly limited as long as it can function as the protective film 3. From the viewpoint of reflectance to EUV light, the thickness of the protective film 3 is preferably 1.0 nm to 8.0 nm, and more preferably 1.5 nm to 6.0 nm.

[0075] The protective film 3 can be formed by any known film formation method without any particular restrictions, and specific examples include sputtering and ion beam sputtering.

[0076] <<Absorber membrane 4>> The reflective mask blank 100 of this embodiment has a multilayer reflective film 2 and an absorber film 4, in this order, on a substrate 1. More specifically, in the reflective mask blank 100 of this embodiment, the absorber film 4 that absorbs EUV light is formed on the multilayer reflective film 2 or the protective film 3. The absorber film 4 has the function of absorbing EUV light.

[0077] The absorber film 4 of the reflective mask blank 100 of this embodiment contains a predetermined material having a refractive index and extinction coefficient such that, when the value of the evaluation function of a film having a refractive index of 0.95 and an extinction coefficient of 0.03 is normalized to 1, the value of the normalized evaluation function (normalized evaluation function) of the absorber film 4 is 1.015 or more, preferably 1.03 or more, and more preferably 1.05 or more. The absorber film 4 of the reflective mask blank 100 of this embodiment can be made only of a predetermined material having the predetermined evaluation function value. By including the predetermined material in the absorber film 4 of the reflective mask blank 100 of this embodiment, it is possible to form transfer patterns of a variety of fine patterns on a transfer substrate, compared to conventional absorber films 4 made from materials such as TaBN films and TaN films, and it can be said that a reflective mask blank 100 can be obtained that is used to manufacture a reflective mask 200 having a transfer pattern that allows EUV exposure to be performed with a high throughput.

[0078] As described above, the evaluation function is the product of the normalized image logarithmic slope (NILS) and the threshold light intensity for the exposure of a given resist. The upper limit of the value of the normalized evaluation function can be determined depending on the requirement for finer transfer patterns. To enable the selection of a realistic material for the absorber film 4, the upper limit of the value of the normalized evaluation function is preferably 2.0 or less, and more preferably 1.7 or less.

[0079] In the reflective mask blank 100 of this embodiment, it is preferable that the refractive index of the material of the absorber film 4 is in the range of 0.86 to 0.95, and the extinction coefficient of the material of the absorber film 4 is in the range of 0.015 to 0.065. When the refractive index and extinction coefficient of the material of the absorber film 4 are in the predetermined ranges, it is relatively easy to obtain a material having a refractive index and extinction coefficient such that the value of the normalized evaluation function of the absorber film 4 is 1.015 or more.

[0080] Examples of simple materials belonging to the region where the value of the normalized evaluation function is 1.015 or more include Ag, Co, Pt, Au, Fe, Pd, Ir, W, Cr, Rh, Ru, etc. Also included are alloys containing one or more elements selected from Ag, Co, Pt, Au, Fe, Pd, Ir, W, Cr, Rh, and Ru, and materials containing a simple element or alloy of Ag, Co, Pt, Au, Fe, Pd, Ir, W, Cr, Rh, or Ru and one or more elements selected from oxygen (O), nitrogen (N), carbon (C), boron (B), and hydrogen (H), so that the value of the normalized evaluation function is 1.015 or more. Therefore, if the absorber film 4 is formed using these materials, it is possible to form transfer patterns of a variety of fine patterns on the transfer substrate, compared to absorber films 4 made from conventional materials such as TaBN films and TaN films, and it is possible to obtain a reflective mask blank 100 for manufacturing a reflective mask 200 having a transfer pattern that allows EUV exposure to be performed with high throughput.

[0081] Specific examples of materials having a normalized evaluation function value of 1.015 or more include Ir, Pt, and IrTa alloys (for example, atomic ratio Ir:Ta=4:1).

[0082] In the reflective mask blank 100 of this embodiment, the material of the absorber film 4 preferably contains at least one selected from iridium (Ir) and ruthenium (Ru).

[0083] The refractive index of iridium (Ir) is 0.905 and the extinction coefficient is 0.044. The refractive index of ruthenium (Ru) is 0.886 and the extinction coefficient is 0.017. Therefore, by including at least one selected from iridium (Ir) and ruthenium (Ru) in the material of the absorber film 4, it is relatively easy to obtain a material having a refractive index and an extinction coefficient such that the value of the normalized evaluation function of the absorber film 4 is 1.015 or more.

[0084] The material of the absorber film 4 of the reflective mask blank 100 of this embodiment preferably contains iridium (Ir) and at least one selected from boron (B), silicon (Si), ruthenium (Ru), tantalum (Ta), and oxygen (O). An absorber film 4 made of simple Ir has the problem of high surface roughness and relatively difficult etching. Another problem with Ir thin films is that the refractive index (n) and extinction coefficient (k) vary depending on the film formation conditions. Therefore, it is preferable to use an Ir alloy or Ir compound containing the above-mentioned elements as the material of the absorber film 4.

[0085] In the reflective mask blank 100 of this embodiment, the material of the absorber film 4 preferably contains platinum (Pt) or gold (Au).

[0086] The refractive index of platinum (Pt) is 0.891 and the extinction coefficient is 0.060. The refractive index of gold (Au) is 0.899 and the extinction coefficient is 0.052. Therefore, by including platinum (Pt) or gold (Au) in the material of the absorber film 4, it is relatively easy to obtain a material having a refractive index and extinction coefficient such that the value of the normalized evaluation function of the absorber film 4 is 1.015 or higher. Furthermore, since platinum (Pt) or gold (Au) is a stable metal and its refractive index and extinction coefficient are unlikely to change after film formation, it is preferable that the material of the absorber film 4 include platinum (Pt) or gold (Au).

[0087] The absorber film 4 can be composed of two layers: a buffer layer disposed in contact with the surface of the multilayer reflective film 2 or the protective film 3, and an absorber layer formed on the surface of the buffer layer. In this case, the material of the absorber film 4 described above can be used as the material of the absorber layer. The buffer layer can be disposed when the etching selectivity between the material of the absorber layer (absorber film 4) and the material of the multilayer reflective film 2 or the protective film 3 is not high. The buffer layer facilitates the formation of the absorber pattern 4a, thereby enabling the absorber pattern 4a to be thinned. The material of the absorber film 4 described above can also be used as the material of the buffer layer. In this case, the material of the buffer layer is preferably a material having an etching selectivity of 1.5 or more relative to the material of the absorber layer. Using the material of the absorber film 4 described above as the buffer layer can broaden the range of materials to be used for the absorber layer and the protective film 3 without reducing the effects of the present invention. For example, the material of the buffer layer may contain chromium (Cr) and one or more elements selected from oxygen (O), nitrogen (N), carbon (C), boron (B), and hydrogen (H).

[0088] Furthermore, materials other than the material of the absorber film 4 described above can be used as the material of the buffer layer, provided that the effects of the present invention are not reduced. For example, the material of the buffer layer may be a material containing tantalum (Ta) or silicon (Si) and one or more elements selected from oxygen (O), nitrogen (N), carbon (C), boron (B), and hydrogen (H). In such cases, the thickness of the buffer layer is preferably 1 / 3 or less of the thickness of the entire absorber film (absorber layer and buffer layer). The thickness of the buffer layer is preferably 20 nm or less, more preferably 15 nm or less, and even more preferably 10 nm or less. The thickness of the buffer layer is preferably 2 nm or more.

[0089] In the case of the absorber film 4 intended to absorb EUV light, the film thickness is set so that the reflectance of EUV light for the absorber film 4 is 2% or less, preferably 1% or less. In order to suppress the shadowing effect, the film thickness of the absorber film 4 is required to be less than 60 nm, preferably 50 nm or less.

[0090] An oxide layer may also be formed on the surface of the absorber film 4 (the absorber layer when the absorber film 4 is composed of two layers, a buffer layer and an absorber layer). Forming an oxide layer on the surface of the absorber film 4 (absorber layer) can improve the cleaning resistance of the absorber pattern 4a of the resulting reflective mask 200. The thickness of the oxide layer is preferably 1.0 nm or more, more preferably 1.5 nm or more. The thickness of the oxide layer is preferably 5 nm or less, more preferably 3 nm or less. If the thickness of the oxide layer is less than 1.0 nm, it is too thin and no effect can be expected. If the thickness of the oxide layer exceeds 5 nm, it will have a significant effect on the surface reflectance for mask inspection light, making it difficult to control to obtain the desired surface reflectance.

[0091] The oxide layer can be formed by subjecting the mask blank after the absorber film 4 (absorber layer) has been formed to hot water treatment, ozone water treatment, heat treatment in an oxygen-containing gas, ultraviolet irradiation treatment in an oxygen-containing gas, O2 plasma treatment, etc. Furthermore, if the surface of the absorber film 4 (absorber layer) is exposed to the atmosphere after the absorber film 4 (absorber layer) has been formed, an oxide layer may be formed on the surface due to natural oxidation. In particular, in some cases, an oxide layer with a thickness of 1 to 2 nm is formed.

[0092] <<Etching mask film>> The reflective mask blank 100 of this embodiment may include an etching mask film. The thickness of the etching mask film is 0.5 nm or more and 14 nm or less.

[0093] By having an appropriate etching mask film, it is possible to obtain a reflective mask blank 100 that can further reduce the shadowing effect of the reflective mask 200 and can form a fine, highly accurate absorber pattern 4a.

[0094] As shown in FIG. 1, the etching mask film is formed on the absorber film 4. The material of the etching mask film is one that has a high etching selectivity of the absorber film 4 to the etching mask film. Here, the "etching selectivity of B to A" refers to the ratio of the etching rates of A, which is a layer that should not be etched (a layer that serves as a mask), and B, which is a layer that should be etched. Specifically, it is determined by the formula "etching selectivity of B to A = etching rate of B / etching rate of A." Furthermore, "high selectivity" refers to a selectivity value, as defined above, that is higher than that of a comparative object. The etching selectivity of the absorber layer 44 to the etching mask film is preferably 1.5 or more, and more preferably 3 or more.

[0095] In the reflective mask blank 100 of this embodiment, the material of the etching mask film is preferably a material containing tantalum (Ta) and one or more elements selected from oxygen (O), nitrogen (N), carbon (C), boron (B), and hydrogen (H).More preferably, the material of the etching mask film is a material containing tantalum (Ta) and one or more elements selected from oxygen (O), nitrogen (N), boron (B), and hydrogen (H).

[0096] The etching mask film of this embodiment may be made of a silicon-containing material. The silicon-containing material may be silicon, a silicon compound, a metal silicon containing silicon and a metal, or a metal silicon compound containing a silicon compound and a metal. The silicon compound preferably contains silicon and at least one element selected from oxygen (O), nitrogen (N), carbon (C), and hydrogen (H). The silicon compound of the etching mask film is more preferably silicon and at least one element selected from oxygen (O) and nitrogen (N).

[0097] Specific examples of silicon-containing materials include SiO, SiN, SiON, SiC, SiCO, SiCN, SiCON, MoSi, MoSiO, MoSiN, and MoSiON. It is preferable to use SiO, SiN, or SiON as the silicon-containing material. The material may contain a semimetal or metal other than silicon as long as the effects of the present invention are achieved. Furthermore, molybdenum silicide may be used as the metal silicon compound.

[0098] An etching mask film made of a material containing silicon can be etched with a fluorine-based gas.

[0099] The thickness of the etching mask film is 0.5 nm or more, preferably 1 nm or more, more preferably 2 nm or more, and even more preferably 3 nm or more, from the viewpoint of functioning as an etching mask for accurately forming a transfer pattern in the absorber film 4. Furthermore, from the viewpoint of reducing the thickness of the resist film 11, the thickness of the etching mask film is 14 nm or less, preferably 12 nm or less, and more preferably 10 nm or less.

[0100] When the absorber film 4 is composed of two layers, a buffer layer and an absorber layer, the etching mask film and the buffer layer may be made of the same material. The etching mask film and the buffer layer may also be made of materials containing the same metal but with different composition ratios. When the etching mask film and the buffer layer contain tantalum, the tantalum content of the etching mask film may be greater than the tantalum content of the buffer layer, and the thickness of the etching mask film may be greater than the thickness of the buffer layer. When the etching mask film and the buffer layer contain hydrogen, the hydrogen content of the etching mask film may be greater than the hydrogen content of the buffer layer.

[0101] <<Resist film 11>> The reflective mask blank 100 of this embodiment can have a resist film 11 on the etching mask film. The reflective mask blank 100 of this embodiment also includes a form having a resist film 11. In the reflective mask blank 100 of this embodiment, the resist film 11 can also be made thinner by selecting an appropriate material and / or an appropriate thickness of the absorber film 4 and an etching gas.

[0102] For example, a chemically amplified resist (CAR) can be used as the material of the resist film 11. The resist film 11 is patterned and the absorber film 4 (the buffer layer 42 and the absorption layer 44) is etched, thereby manufacturing a reflective mask 200 having a predetermined transfer pattern.

[0103] <<Backside conductive film 5>> A back surface conductive film 5 for an electrostatic chuck is generally formed on the second main surface (back surface) of the substrate 1 (opposite the surface on which the multilayer reflective film 2 is formed). The electrical characteristics (sheet resistance) required of the back surface conductive film 5 for an electrostatic chuck are usually 100 Ω / □ (Ω / Square) or less. The back surface conductive film 5 can be formed by, for example, magnetron sputtering or ion beam sputtering using a target of a metal such as chromium or tantalum, or an alloy thereof.

[0104] The chromium (Cr)-containing material of the back surface conductive film 5 is preferably a Cr compound containing Cr and at least one element selected from boron, nitrogen, oxygen, and carbon. Examples of Cr compounds include CrN, CrON, CrCN, CrCON, CrBN, CrBON, CrBCN, and CrBOCN.

[0105] The tantalum (Ta)-containing material of the back surface conductive film 5 is preferably Ta, 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.

[0106] For materials containing tantalum (Ta) or chromium (Cr), it is preferable that the amount of nitrogen (N) present in the surface layer is small. Specifically, the nitrogen content in the surface layer of the back surface conductive film 5 made of a material containing tantalum (Ta) or chromium (Cr) is preferably less than 5 atomic %, and more preferably the surface layer is substantially free of nitrogen. This is because the lower the nitrogen content in the surface layer of the back surface conductive film 5 made of a material containing tantalum (Ta) or chromium (Cr), the higher the wear resistance.

[0107] The back surface conductive film 5 is preferably made of a material containing tantalum and boron. When the back surface conductive film 5 is made of a material containing tantalum and boron, a conductive film 23 having wear resistance and chemical resistance can be obtained. When the back surface conductive film 5 contains tantalum (Ta) and boron (B), the B content is preferably 5 to 30 atomic %. The ratio of Ta to B (Ta:B) in the sputtering target used to deposit the back surface conductive film 5 is preferably 95:5 to 70:30.

[0108] The film thickness of the back surface conductive film 5 is not particularly limited as long as it satisfies the function required for electrostatic chucking. The film thickness of the back surface conductive film 5 is usually 10 nm to 200 nm. The back surface conductive film 5 also serves to adjust the stress on the second main surface side of the reflective mask blank 100. In other words, the back surface conductive film 5 is adjusted to achieve a balance with the stress from the various films formed on the first main surface side, thereby obtaining a flat reflective mask blank 100.

[0109] <Reflective mask 200 and its manufacturing method> This embodiment is a reflective mask 200 having an absorber pattern 4a formed by patterning the absorber film 4 of the above-mentioned reflective mask blank 100. By using the reflective mask 200 of this embodiment, it is possible to form transfer patterns of diversified fine patterns on a transfer substrate, and also to perform EUV exposure with high throughput.

[0110] The absorber pattern 4a of the reflective mask 200 absorbs the EUV light and the openings of the absorber pattern 4a can reflect the EUV light. Therefore, by irradiating the reflective mask 200 with EUV light using a predetermined optical system, a predetermined fine transfer pattern can be transferred onto the transfer target.

[0111] A reflective mask 200 is manufactured using the reflective mask blank 100 of this embodiment. Only an outline will be given here, and a detailed description will be given later in examples with reference to the drawings.

[0112] A reflective mask blank 100 is prepared. A resist film 11 is formed on the absorber film 4 on the first main surface of the reflective mask blank 100 (this is not necessary if the reflective mask blank 100 is already provided with a resist film 11). A desired pattern is drawn (exposed) on this resist film 11, and then developed and rinsed to form a predetermined resist pattern 11a.

[0113] In the case of the reflective mask blank 100, the absorber pattern 4a is formed by etching the absorber film 4 using this resist pattern 11a as a mask. The resist pattern 11a is stripped by oxygen ashing or wet treatment using hot sulfuric acid, etc. Finally, wet cleaning is performed using an acidic or alkaline aqueous solution.

[0114] Through the above steps, the reflective mask 200 of this embodiment can be obtained.

[0115] <Method of manufacturing a semiconductor device> The method for manufacturing a semiconductor device according to this embodiment includes the steps of setting the reflective mask 200 according to this embodiment in an exposure apparatus having an exposure light source that emits EUV light, and transferring a transfer pattern to a resist layer formed on a transfer substrate. The method for manufacturing a semiconductor device according to this embodiment makes it possible to form a variety of fine pattern shapes on a transfer substrate with high throughput.

[0116] According to the semiconductor device manufacturing method of this embodiment, it is possible to form transfer patterns of various fine patterns on a transfer substrate by using the reflective mask 200 of this embodiment. Furthermore, by using the reflective mask 200 of this embodiment, EUV exposure can be performed with high throughput.

[0117] By performing EUV exposure using the reflective mask 200 of this embodiment, a desired pattern can be formed on a semiconductor substrate with high dimensional accuracy and high throughput. In addition to this lithography process, various processes such as etching of the film to be processed, formation of insulating and conductive films, introduction of dopants, and annealing can be performed to manufacture a semiconductor device with a desired electronic circuit formed thereon.

[0118] More specifically, the EUV exposure tool comprises a laser plasma light source that generates EUV light, an illumination optical system, a mask stage system, a reduction projection optical system, a wafer stage system, and vacuum equipment. The light source is equipped with a debris trap function, a cut filter that cuts out long-wavelength light other than the exposure light, and equipment for vacuum differential pumping. The illumination optical system and reduction projection optical system are composed of reflective mirrors. The EUV exposure reflective mask 200 is electrostatically attracted by a conductive film formed on its second main surface and placed on the mask stage.

[0119] Light from an EUV light source is irradiated onto the reflective mask 200 via an illumination optical system at an angle of 6° to 8° relative to the vertical plane of the reflective mask 200. The light reflected from the reflective mask 200 is reflected (specularly reflected) in the opposite direction to the incident light and at the same angle as the incident light. The reflected light is then guided to a reflective projection optical system, typically with a reduction ratio of 1 / 4, and used to expose a resist layer on a wafer (semiconductor substrate) placed on a wafer stage. During this process, at least the area through which the EUV light passes is evacuated. Scanning exposure, in which the mask stage and wafer stage are synchronously scanned at a speed corresponding to the reduction ratio of the reduction projection optical system, and exposure is performed through a slit, is the mainstream method for this exposure. The exposed resist on the resist layer is then developed to form a resist transfer pattern on the semiconductor substrate. This resist transfer pattern can then be used as a mask to perform etching or other processes, thereby forming, for example, a predetermined wiring pattern on the semiconductor substrate. A semiconductor device is manufactured through these exposure processes, a film processing process, an insulating film or conductive film formation process, a dopant introduction process, an annealing process, and other necessary processes. [Example]

[0120] Hereinafter, embodiments will be described with reference to the drawings. Note that the same reference numerals will be used to designate similar components throughout the embodiments, and descriptions thereof will be simplified or omitted.

[0121] [Example 1] As Example 1, the effects of this embodiment were confirmed by the following simulation. Note that the refractive index (n) and extinction coefficient (k) shown below are values ​​for light with a wavelength of 13.5 nm. The same applies to other examples.

[0122] The simulation of Example 1 used the structure of a reflective mask 200 shown in Fig. 2D. That is, the reflective mask 200 has a multilayer reflective film 2, a protective film 3, and an absorber pattern 4a, in this order, on one main surface of a substrate 1. The reflective mask 200 has a back surface conductive film 5 on the other main surface of the substrate 1. However, in the simulation of Example 1, the exposure light is reflected by the multilayer reflective film 2, so the presence or absence of the back surface conductive film 5 does not affect the results of the simulation.

[0123] In the simulation of Example 1, a SiO2-TiO2-based glass substrate, which is a low-thermal expansion glass substrate having a size of 6025 (approximately 152 mm × 152 mm × 6.35 mm) and in which both the first and second main surfaces (rear surfaces) have been polished, was used as substrate 1. It was assumed that the two main surfaces of substrate 1 were equivalent to those polished through a rough polishing process, a precision polishing process, a local polishing process, and a touch polishing process to obtain flat and smooth main surfaces.

[0124] The back surface conductive film 5 was a thin film made of CrN with a thickness of 20 nm. Specifically, it was assumed to be a thin film equivalent to a back surface conductive film 5 made of CrN formed on the second main surface (back surface) of the substrate 1 by magnetron sputtering (reactive sputtering) under the following conditions: Conditions for forming the back surface conductive film 5: Cr target, mixed gas atmosphere of Ar and N2 (Ar: 90%, N: 10%), film thickness 20 nm.

[0125] The multilayer reflective film 2 was a periodic multilayer reflective film 2 made of Mo and Si to be suitable for EUV light with a wavelength of 13.5 nm. Specifically, it was assumed to be a multilayer film equivalent to the multilayer reflective film 2 formed on the main surface (first main surface) of the substrate 1 opposite the side on which the back surface conductive film 5 was formed, by ion beam sputtering using a Mo target and a Si target in an Ar gas atmosphere to alternately stack Mo layers and Si layers on the substrate 1. This multilayer film was formed by first depositing a Si film to a thickness of 4.2 nm, followed by depositing a Mo film to a thickness of 2.8 nm. This constitutes one period, and the multilayer reflective film 2 formed by depositing 40 periods in the same manner and finally depositing a Si film to a thickness of 4.0 nm was assumed to be the multilayer reflective film 2 of Example 1.

[0126] The simulation was performed assuming that the protective film 3 was made of the following two types of thin films. Example 1-1: RuNb film (n = 0.9016, k = 0.0131, film thickness 3.5 nm) Example 1-2: RuRh film (n=0.8898, k=0.0155, film thickness 3.5 nm)

[0127] Simulations were performed for cases where the absorber pattern 4a had the following three types of patterns. (1) Vertical L / S pattern (vertical L / S, hp=16nm), (2) Horizontal L / S pattern (hp=16nm), (3) Contact hole pattern (Contact Hole, diameter 24 nm)

[0128] In the exposure process, light from an EUV light source is irradiated onto the reflective mask 200 via an illumination optical system at an angle of 6° to 8° with respect to the vertical plane of the reflective mask 200. The light reflected from the reflective mask 200 in response to this incident light is reflected (specularly reflected) in the opposite direction to the incident direction and at the same angle as the incident angle. Therefore, even if the L / S pattern is the same, if the orientation of the L / S pattern with respect to the plane containing the incident light and reflected light is different, the transferred pattern transferred to the transfer substrate will also be different. When the normal to the plane containing the incident light and reflected light with respect to the reflective mask 200 is perpendicular to the direction of the lines of the L / S pattern, it is a vertical L / S pattern, and when it is parallel to the direction, it is a horizontal L / S pattern.

[0129] The contact hole pattern is circular. Therefore, when the absorber pattern 4a of the reflective mask 200 is a contact hole pattern, the transfer pattern transferred onto the transfer substrate does not depend on the direction of the incident light.

[0130] The thickness of the absorber pattern 4a was optimized so as to obtain the highest evaluation function value for each of the three types of patterns.

[0131] The reflective masks 200 used for normalizing the values ​​of the evaluation function of the reflective masks 200 of Examples 1-1 and 1-2 were thin-film reflective masks 200 whose absorber film 4 was optically equivalent to a TaBN film and a TaN film. That is, the absorber film 4 of the reflective mask 200 for normalization was a film whose refractive index for EUV light with a wavelength of 13.5 nm was 0.95 and whose extinction coefficient was 0.03. The value of the evaluation function of the reflective mask 200 for normalization was set to 1, and the values ​​of the evaluation function of the reflective masks 200 of Examples 1-1 and 1-2 were normalized. The same applies to Examples other than Examples 1-1 and 1-2.

[0132] (Example 1-1) FIG. 3 shows the values ​​of the normalized evaluation function obtained by simulation for the reflective mask 200 of Example 1-1 (where the protective film 3 is a RuNb film) when the absorber pattern 4a is a vertical L / S (line and space) pattern with hp of 16 nm. FIG. 3 is a diagram showing the distribution of the values ​​of the normalized evaluation function when predetermined incident light is irradiated onto absorber patterns 4a with different refractive indices (n) and extinction coefficients (k) in the reflective mask 200 of Example 1-1. In the simulation shown in FIG. 3, numerous simulations were performed assuming absorber films 4 with numerous combinations of refractive indices (n) and extinction coefficients (k) within the range shown in FIG. 3. In FIG. 3, the values ​​of the normalized evaluation function are shown in grayscale.

[0133] FIG. 5 shows the values ​​of the normalized evaluation function obtained by simulation for the reflective mask 200 of Example 1-1 (where the protective film 3 is a RuNb film) when the absorber pattern 4a is a horizontal L / S (line and space) pattern with hp of 16 nm. FIG. 5 is a diagram showing the distribution of the values ​​of the normalized evaluation function when predetermined incident light is irradiated onto absorber patterns 4a with different refractive indices (n) and extinction coefficients (k) in the reflective mask 200 of Example 1-1. In the simulation shown in FIG. 5, numerous simulations were performed assuming absorber films 4 with numerous combinations of refractive indices (n) and extinction coefficients (k) within the range shown in FIG. 5. In FIG. 5, the values ​​of the normalized evaluation function are shown in grayscale.

[0134] FIG. 7 shows the values ​​of the normalized evaluation function obtained by simulation for the reflective mask 200 of Example 1-1 (where the protective film 3 is a RuNb film) when the absorber pattern 4a is a contact hole pattern (diameter 24 nm). FIG. 7 is a diagram showing the distribution of the values ​​of the normalized evaluation function when predetermined incident light is irradiated onto absorber patterns 4a with different refractive indices (n) and extinction coefficients (k) in the reflective mask 200 of Example 1-1. In the simulation shown in FIG. 7, a large number of simulations were performed assuming absorber films 4 with many combinations of refractive indices (n) and extinction coefficients (k) within the range shown in FIG. 7. In FIG. 7, the values ​​of the normalized evaluation function are shown in grayscale.

[0135] (Example 1-2) Fig. 4 shows the values ​​of the normalized evaluation function obtained by simulation for the reflective mask 200 of Example 1-2 (where the protective film 3 is a RuRh film) when the absorber pattern 4a is a vertical L / S (line and space) pattern with hp of 16 nm. Similar to the case of Example 1-1 shown in Fig. 3, Fig. 4 shows the distribution of the values ​​of the normalized evaluation function when predetermined incident light is irradiated onto absorber patterns 4a with different refractive indices (n) and extinction coefficients (k) in the reflective mask 200 of Example 1-2.

[0136] Fig. 6 shows the values ​​of the normalized evaluation function obtained by simulation for the reflective mask 200 of Example 1-2 (where the protective film 3 is a RuRh film) when the absorber pattern 4a is a horizontal L / S (line and space) pattern with hp of 16 nm. Similar to the case of Example 1-1 shown in Fig. 5, Fig. 6 shows the distribution of the values ​​of the normalized evaluation function when predetermined incident light is irradiated onto absorber patterns 4a with different refractive indices (n) and extinction coefficients (k) in the reflective mask 200 of Example 1-2.

[0137] (Combination of Example 1-1 and Example 1-2) 8 and 9 show diagrams combining the distributions of the normalized evaluation function values ​​of Examples 1-1 and 1-2 obtained as described above. Specifically, Fig. 8 is a diagram combining the distributions of the normalized evaluation function values ​​of the vertical L / S patterns shown in Fig. 3 (Example 1-1) and Fig. 4 (Example 1-2), showing a binarized distribution when the values ​​of the normalized evaluation function shown in Fig. 3 and Fig. 4 are both 1.015 or more (white) and other cases (black). Fig. 9 is a diagram combining the distributions of the normalized evaluation function values ​​of the horizontal L / S patterns shown in Fig. 5 (Example 1-1) and Fig. 6 (Example 1-2), showing a binarized distribution when the values ​​of the normalized evaluation function shown in Fig. 5 and Fig. 6 are both 1.015 or more (white) and other cases (black). FIG. 10 shows the distribution of the values ​​of the normalized evaluation function of the contact hole pattern shown in FIG. 7 (Example 1-1), binarized for cases where the value of the normalized evaluation function of the contact hole pattern of Example 1-1 is 1.015 or more (white) and other cases (black).

[0138] Fig. 11 is a diagram combining the distributions of the binarized normalized evaluation function values ​​shown in Figs. 8 to 10. Fig. 11 shows the distributions when all the values ​​of the normalized evaluation functions shown in Figs. 8 to 10 are 1.015 or more (white) and when they are not (black).

[0139] From the simulation results of Examples 1-1 and 1-2 above, it can be seen that in the distribution of the refractive index (n) and extinction coefficient (k) of the absorber pattern 4a (absorber film 4), the region where the values ​​of the normalized evaluation function are all 1.015 or more is the region shown in white in FIG. 11. Simple materials belonging to the region where the values ​​of the normalized evaluation function are all 1.015 or more are Ag, Co, Pt, Au, Fe, Pd, Ir, W, Cr, Rh, Ru, etc. Therefore, if the absorber film 4 is formed using these materials, it is possible to form transfer patterns of diversified fine patterns on a transfer substrate, compared to absorber films 4 made from conventional materials such as TaBN films and TaN films, and it can be said that a reflective mask blank 100 for manufacturing a reflective mask 200 having a transfer pattern that can be subjected to EUV exposure with high throughput can be obtained.

[0140] Furthermore, even if the material is an alloy or compound material other than the above-mentioned simple materials, by appropriately adjusting the composition, it can be said that it is possible to form an absorber pattern 4a (absorber film 4) having a refractive index (n) and extinction coefficient (k) in the region shown in white in Fig. 11 (the region where all values ​​of the normalized evaluation function are 1.015 or more). Note that examples of such alloy or compound materials include alloy or compound materials of iridium (Ir) with boron (B), silicon (Si), ruthenium (Ru), tantalum (Ta), and oxygen (O).

[0141] It can be said that the higher the value of the normalized evaluation function, the more excellent a transfer pattern can be formed and the higher the throughput of EUV exposure can be, compared with absorber films 4 made of conventional materials such as TaBN films and TaN films. Therefore, the value of the normalized evaluation function is preferably 1.015 or more, more preferably 1.03 or more, and even more preferably 1.05 or more.

[0142] [Example 2] In Example 2, a material for the absorber film 4 was selected so that the value of the normalized evaluation function would be 1.015 or more, and a reflective mask blank 100 and a reflective mask 200 were manufactured.

[0143] As shown in Fig. 1, the reflective mask blank 100 of Example 2 has a back surface conductive film 5, a substrate 1, a multilayer reflective film 2, a protective film 3, and an absorber film 4. Then, as shown in Fig. 2A, a resist film 11 is formed on the absorber film 4. Figs. 2A to 2D are schematic cross-sectional views of essential parts showing the steps of producing a reflective mask 200 from the reflective mask blank 100.

[0144] In the following description, the elemental composition of the deposited thin film was measured by Rutherford backscattering spectroscopy.

[0145] First, a reflective mask blank 100 of Example 2 will be described.

[0146] A SiO2-TiO2-based glass substrate, which is a low-thermal expansion glass substrate having a 6025 size (approximately 152 mm × 152 mm × 6.35 mm) with both the first and second main surfaces polished, was prepared as substrate 1. To obtain a flat and smooth main surface, polishing was carried out through a rough polishing process, a precision polishing process, a local polishing process, and a touch polishing process.

[0147] A back surface conductive film 5 made of a CrN film was formed on the second main surface (back surface) of the SiO2-TiO2-based glass substrate 1 by magnetron sputtering (reactive sputtering) under the following conditions. Conditions for forming the back surface conductive film 5: Cr target, mixed gas atmosphere of Ar and N2 (Ar: 90%, N: 10%), film thickness 20 nm.

[0148] Next, a multilayer reflective film 2 was formed on the main surface (first main surface) of the substrate 1 opposite the side on which the back conductive film 5 was formed. The multilayer reflective film 2 formed on the substrate 1 was a periodic multilayer reflective film 2 made of Mo and Si to be suitable for EUV light with a wavelength of 13.5 nm. The multilayer reflective film 2 was formed by alternately laminating Mo layers and Si layers on the substrate 1 by ion beam sputtering in an Ar gas atmosphere using a Mo target and a Si target. First, a Si film was formed to a thickness of 4.2 nm, followed by a Mo film to a thickness of 2.8 nm. This constitutes one cycle, and 40 cycles were similarly laminated, and finally, a Si film was formed to a thickness of 4.0 nm to form the multilayer reflective film 2.

[0149] Subsequently, a protective film 3 made of RuNb film was formed to a thickness of 3.5 nm by ion beam sputtering using a RuNb target in an Ar gas atmosphere.

[0150] Next, an absorber film 4 was formed on the protective film 3, which was composed of a buffer layer made of CrON and an absorber layer made of IrTaO.

[0151] Specifically, a buffer layer made of CrON film was first formed by DC magnetron sputtering. The CrON film was deposited to a thickness of 6 nm by reactive sputtering using a Cr target in a mixed gas atmosphere of Ar gas, O2 gas, and N2 gas. The refractive index (n) of the CrON film (buffer layer) at a wavelength of 13.5 nm was 0.930 and the extinction coefficient (k) was 0.039.

[0152] Next, an absorber layer made of an IrTaO film was formed by DC magnetron sputtering. The IrTaO film was deposited to a thickness of 40 nm by reactive sputtering using an IrTa alloy target in a mixed gas atmosphere of Xe and O2 gases.

[0153] The elemental ratio of the IrTaO film was 49.5 atomic % Ir, 3.4 atomic % Ta, and 47.1 atomic % O. The refractive index (n) of the IrTaO film at a wavelength of 13.5 nm was 0.927, and the extinction coefficient (k) was 0.033.

[0154] In this manner, the reflective mask blank 100 of Example 2 was produced.

[0155] Next, a reflective mask 200 of Example 2 was manufactured using the reflective mask blank 100 of Example 2.

[0156] A resist film 11 was formed to a thickness of 80 nm on the absorber film 4 (absorber layer) of the reflective mask blank 100 (FIG. 2A). A chemically amplified resist (CAR) was used to form the resist film 11. A desired pattern was written (exposed) on this resist film 11, and then developed and rinsed to form a predetermined resist pattern 11a (FIG. 2B). Next, using the resist pattern 11a as a mask, the IrTaO film (absorber layer) was dry-etched using a mixed gas of CF4 gas and O2 gas (CF4 + O2 gas), and subsequently the CrON film (buffer layer) was dry-etched using a mixed gas of Cl2 gas and O2 gas (Cl2 + O2 gas), thereby forming an absorber pattern 4a (FIG. 2C).

[0157] Thereafter, the resist pattern 11a was stripped by oxygen ashing (FIG. 2D). Finally, wet cleaning was performed using pure water (DIW), thereby producing the reflective mask 200 of Example 2.

[0158] If necessary, a mask defect inspection can be performed after wet cleaning, and mask defects can be repaired as appropriate.

[0159] The reflective mask 200 of Example 2 was set on an EUV scanner, and a wafer having a processing film and a resist layer formed on a semiconductor substrate was subjected to EUV exposure. Then, the exposed resist of the resist layer was developed to form a resist transfer pattern on the semiconductor substrate having the processing film formed thereon.

[0160] Separately, when a predetermined chemically amplified resist (CAR) was exposed to a predetermined exposure light, the normalized image logarithmic slope (NILS) and the threshold light intensity for the exposure of the predetermined resist were measured using the reflective mask 200 of Example 2, and the value of the evaluation function was obtained as the product of these values. When the value of this evaluation function was normalized by the value of the evaluation function when the reflective mask 200 of Reference Example 1 described later was used, the value of the normalized evaluation function of Example 2 was 1.03.

[0161] It was confirmed that by forming a resist transfer pattern on the transfer substrate 1 using the reflective mask 200 of Example 2, it is possible to form transfer patterns with a variety of fine pattern shapes on the transfer substrate, and that EUV exposure can be performed with high throughput.

[0162] This resist transfer pattern was transferred to the film to be processed by etching, and by going through various processes such as forming insulating and conductive films, introducing dopants, and annealing, a semiconductor device with the desired characteristics could be manufactured.

[0163] [Example 3] In Example 3, a reflective mask blank 100 and a reflective mask 200 were manufactured in the same manner as in Example 1, except that a RuRh film with a thickness of 3.5 nm was used as the protective film 3 and a Pt film was used as the absorbing layer in the absorber film 4. Therefore, the absorber film 4 in Example 3 was composed of a buffer layer (thickness 6 nm) made of CrON and an absorbing layer (thickness 40 nm) of a Pt film.

[0164] The refractive index (n) of the Pt film at a wavelength of 13.5 nm was 0.889, and the extinction coefficient (k) was 0.059.

[0165] The reflective mask 200 of Example 3 was set on an EUV scanner, and a wafer having a processing film and a resist layer formed on a semiconductor substrate was subjected to EUV exposure. Then, the exposed resist of the resist layer was developed to form a resist transfer pattern on the semiconductor substrate having the processing film formed thereon.

[0166] Separately, when a predetermined chemically amplified resist (CAR) was exposed to a predetermined exposure light, the normalized image logarithmic slope (NILS) and the threshold light intensity for the exposure of the predetermined resist were measured using the reflective mask 200 of Example 3, and the value of the evaluation function was obtained as the product of these values. When this evaluation function value was normalized by the value of the evaluation function when the reflective mask 200 of Reference Example 1 described later was used, the value of the normalized evaluation function of Example 3 was 1.02.

[0167] It was confirmed that by forming a resist transfer pattern on a transfer substrate using the reflective mask 200 of Example 3, it is possible to form transfer patterns with a variety of fine pattern shapes on the transfer substrate, and that EUV exposure can be performed with high throughput.

[0168] [Example 4] In Example 4, a reflective mask blank 100 was produced in the same manner as in Example 1, except that the absorber film 4 was made of a buffer layer made of TaBO and an absorption layer made of RuCrN.

[0169] In manufacturing the reflective mask blank 100 of Example 4, similarly to Example 1, a back surface conductive film 5 made of a CrN film was formed on the second main surface (back surface) of the substrate 1, and a multilayer reflective film 2 made of Mo and Si and a protective film 3 made of a RuNb film were formed on the main surface (first main surface) of the substrate 1.

[0170] Next, on the protective film 3, an absorber film 4 was formed, which was composed of a buffer layer made of TaBO and an absorber layer made of RuCrN.

[0171] Specifically, a buffer layer consisting of a TaBO film was first formed by DC magnetron sputtering. The TaBO film was deposited to a thickness of 6 nm by reactive sputtering using a TaB target in a mixed gas atmosphere of Ar gas and O2 gas. The elemental ratio of the TaBO film was 39 atomic % Ta, 5 atomic % B, and 56 atomic % O. The refractive index (n) of the TaBO film (buffer layer) at a wavelength of 13.5 nm was 0.955, and the extinction coefficient (k) was 0.022.

[0172] Next, an absorption layer consisting of a RuCrN film was formed by DC magnetron sputtering. The RuCrN film was deposited to a thickness of 42 nm by reactive sputtering using a RuCr alloy target in a mixed gas atmosphere of Kr gas and N2 gas. The elemental ratio of the RuCrN film was 83 atomic % Ru, 10 atomic % Cr, and 7 atomic % O. The refractive index (n) of the RuCrN film at a wavelength of 13.5 nm was 0.900, and the extinction coefficient (k) was 0.021.

[0173] In this manner, the reflective mask blank 100 of Example 4 was produced.

[0174] Next, using the reflective mask blank 100 of Example 4, a reflective mask 200 of Example 4 was manufactured in the same manner as in Example 1, except that the etching gas for the RuCrN film was a mixed gas of Cl gas and O gas, and the etching gas for the TaBO film was a mixed gas of CF gas and He gas.

[0175] The reflective mask 200 of Example 4 was set on an EUV scanner, and a wafer having a processing film and a resist layer formed on a semiconductor substrate was subjected to EUV exposure. Then, the exposed resist of the resist layer was developed to form a resist transfer pattern on the semiconductor substrate having the processing film formed thereon.

[0176] Separately, when a predetermined chemically amplified resist (CAR) was exposed to a predetermined exposure light, the normalized image logarithmic slope (NILS) and the threshold light intensity for the predetermined resist exposure were measured using the reflective mask 200 of Example 4, and the value of the evaluation function was obtained as the product of these values. When the value of this evaluation function was normalized by the value of the evaluation function when the reflective mask 200 of Reference Example 1 described later was used, the value of the normalized evaluation function of Example 4 was 1.02.

[0177] It was confirmed that by forming a resist transfer pattern on a transfer substrate using the reflective mask 200 of Example 4, it is possible to form transfer patterns with a variety of fine pattern shapes on the transfer substrate, and that EUV exposure can be performed with high throughput.

[0178] [Reference example 1] In Reference Example 1, a reflective mask blank 100 and a reflective mask 200 were manufactured in the same manner as in Example 1, except that a Ru film with a thickness of 3.5 nm was used as the protective film 3 and a single-layer TaBN film was used as the absorber film 4. The reflective mask 200 of Reference Example 1 is a reflective mask 200 that serves as a reference for normalizing the value of the evaluation function.

[0179] In manufacturing the reflective mask blank 100 of Reference Example 1, similarly to Example 1, a back surface conductive film 5 made of a CrN film was formed on the second main surface (back surface) of the substrate 1, and a multilayer reflective film 2 made of Mo and Si was formed on the main surface (first main surface) of the substrate 1.

[0180] Subsequently, a protective film 3 made of a Ru film was formed to a thickness of 3.5 nm by ion beam sputtering using a Ru target in an Ar gas atmosphere.

[0181] Next, an absorber film 4 was formed on the protective film 3. Specifically, the absorber film 4 made of a TaBN film was formed by DC magnetron sputtering. The TaBN film was deposited to a thickness of 55 nm by reactive sputtering using a TaB mixed sintered target in a mixed gas atmosphere of Ar gas and N2 gas.

[0182] The elemental ratios of the absorber film 4 (TaBN film) of Reference Example 1 were 75 atomic % Ta, 12 atomic % B, and 13 atomic % N. The refractive index (n) of the absorber film 4 (TaBN film) at a wavelength of 13.5 nm was 0.95, and the extinction coefficient was 0.030. Therefore, it can be said that the reflective mask blank 100 of Reference Example 1 has an absorber film 4 suitable for manufacturing a reflective mask 200 that serves as a reference for normalizing the value of the evaluation function.

[0183] In this manner, the reflective mask blank 100 of Reference Example 1 was produced.

[0184] Next, similarly to Example 2, a reflective mask 200 of Reference Example 1 was manufactured using the reflective mask blank 100 of Reference Example 1. However, when dry etching the absorber film 4 (TaBN film), the absorber pattern 4a was formed by dry etching the TaBN film using a mixed gas of CF4 gas and He gas (CF4+He gas) (FIG. 2C).

[0185] The reflective mask 200 of Reference Example 1 was set on an EUV scanner, and a wafer having a processing film and a resist layer formed on a semiconductor substrate was subjected to EUV exposure. The exposed resist of the resist layer was then developed to form a resist transfer pattern on the semiconductor substrate having the processing film formed thereon.

[0186] Separately, when a predetermined chemically amplified resist (CAR) was exposed to a predetermined exposure light, the normalized image logarithmic slope (NILS) and the threshold light intensity for the exposure of the predetermined resist were measured using the reflective mask 200 of Reference Example 1, and the value of the evaluation function was obtained as the product of these values. Using this evaluation function value as a reference, the values ​​of the evaluation functions when the reflective masks 200 of Examples 2 and 3 were used were normalized. That is, the value of the normalized evaluation function of Reference Example 1 was 1.

[0187] Since Reference Example 1 is a reflective mask 200 having a reference evaluation function value, the value of the normalized evaluation function is 1. Therefore, when a resist transfer pattern is formed on a transfer substrate using the reflective mask 200 of Reference Example 1, it is clear that the pattern shape of the transfer pattern formed on the transfer substrate is less diverse and finer than with the reflective masks 200 of Examples 2 and 3, and the throughput of EUV exposure is relatively low. [Explanation of symbols]

[0188] 1 board 2 Multilayer reflective film 3 Protective film 4. Absorber membrane 4a Absorber pattern 5 Backside conductive film 11 Resist film 11a Resist pattern 100 Reflective Mask Blanks 200 Reflective Mask

Claims

1. A reflective mask blank having a multilayer reflective film and an absorber film in this order on a substrate, when the value of an evaluation function of a film having a refractive index of 0.95 and an extinction coefficient of 0.03 with respect to EUV light having a wavelength of 13.5 nm is normalized to 1, the absorber film contains a material having a refractive index and an extinction coefficient such that the normalized value of the evaluation function of the absorber film is 1.015 or more, A reflective mask blank, wherein the evaluation function is a product of a normalized image logarithmic slope (NILS) and a threshold light intensity for exposure of a predetermined resist.

2. 2. The reflective mask blank according to claim 1, which is used to produce a reflective mask having a transfer pattern including lines and spaces for the LOGIC hp16 nm generation or later.

3. 3. The reflective mask blank according to claim 1, wherein the refractive index of the material of the absorber film with respect to EUV light having a wavelength of 13.5 nm is in the range of 0.86 to 0.95, and the extinction coefficient of the material of the absorber film with respect to EUV light having a wavelength of 13.5 nm is in the range of 0.015 to 0.

065.

4. 4. The reflective mask blank according to claim 1, wherein the material of the absorber film contains at least one selected from iridium (Ir) and ruthenium (Ru).

5. 4. The reflective mask blank according to claim 1, wherein the material of the absorber film contains iridium (Ir) and at least one selected from boron (B), silicon (Si), ruthenium (Ru), tantalum (Ta), and oxygen (O).

6. 6. The reflective mask blank according to claim 1, wherein the material of the absorber film contains platinum (Pt).

7. 6. The reflective mask blank according to claim 1, wherein the material of the absorber film contains gold (Au).

8. a protective film between the multilayer reflective film and the absorber film; 8. The reflective mask blank according to claim 1, wherein the protective film is made of a material containing ruthenium (Ru) or silicon (Si).

9. 9. A reflective mask, comprising: the absorber film of the reflective mask blank according to claim 1; and an absorber pattern formed by patterning the absorber film.

10. 10. A method for manufacturing a semiconductor device, comprising the steps of: setting the reflective mask according to claim 9 in an exposure apparatus having an exposure light source that emits EUV light; and transferring a transfer pattern onto a resist layer formed on a transfer substrate.

Images