Reflective photomask, reflective photomask blank, and method for manufacturing a reflective photomask

Abstract

A reflective photomask comprising a substrate, a multilayer reflective film, a protective film, and a pattern of light-absorbing films, wherein the protective film is composed of a multilayer including one A layer containing rhodium (Rh) and having a thickness of 0.5 to 2 nm, one or more B layers containing niobium (Nb) but not rhodium (Rh), with a niobium (Nb) content of 10 atomic percent or more and a thickness of 0.5 to 2 nm, and one or more C layers containing ruthenium (Ru) but not rhodium (Rh) or niobium (Nb) and having a thickness of 0.5 to 2 nm, wherein the A layer is in contact with the pattern of light-absorbing films, and one of the C layers is in contact with the multilayer reflective film. [Effect] This provides a reflective photomask equipped with a protective film that is less likely to generate blister defects in environments where extreme ultraviolet light is irradiated in the presence of hydrogen.

Description

Technical Field

[0001] The present invention relates to a reflective photomask used in the manufacture of semiconductor devices and the like, a reflective photomask blank used as a material for the reflective photomask in the manufacture of the reflective photomask, and a method for manufacturing a reflective photomask from the reflective photomask blank.

Background Art

[0002] With the miniaturization of semiconductor devices, particularly due to the high integration of large-scale integrated circuits, high pattern resolution is required for projection lithography. Therefore, as a technique for improving the resolution of the transferred pattern in a photomask, a phase-shift photomask (phase-shift mask) has been developed. The principle of the phase-shift method is to adjust the phase of the transmitted light passing through the opening of the phase-shift film of the photomask so that it is inverted by approximately 180 degrees with respect to the phase of the transmitted light passing through the portion of the phase-shift film adjacent to the opening. As a result, at the boundary between the opening and the portion adjacent to the opening, the transmitted light interferes and the light intensity decreases. Consequently, the resolution and depth of focus of the transferred pattern are improved. A photomask using this principle is generally called a phase-shift photomask. In this case, the phase-shift photomask is a type of transmissive photomask that transmits exposure light.

[0003] The most common type of phase-shift photomask blank used in the manufacture of phase-shift photomasks is one in which a phase-shift film is laminated on a transparent substrate such as a glass substrate, and a film made of a chromium (Cr)-containing material is laminated on top of the phase-shift film. The phase-shift film typically has a phase difference of 175 to 185 degrees with respect to exposure light and a transmittance of about 6 to 30%, and is mainly made of a silicon (Si)-containing film, particularly a material containing molybdenum (Mo) and silicon (Si). The film made of the chromium (Cr)-containing material is adjusted to a thickness that achieves the desired optical density when combined with the phase-shift film, and is generally used as a light-shielding film and as an etching mask when etching the phase-shift film.

[0004] A common method for manufacturing a phase-shift photomask is to pattern a phase-shift film from a phase-shift photomask blank, which has a phase-shift film made of silicon (Si) material and a light-shielding film made of chromium (Cr) material formed in that order on a transparent substrate. Specifically, the following method is generally used: First, a resist film is formed on the light-shielding film made of chromium (Cr) material on the phase-shift photomask blank. A pattern is drawn on this resist film using light or an electron beam, and then developed to form a resist film pattern (resist pattern). Next, using the resist pattern as an etching mask, the light-shielding film made of chromium (Cr) material is dry-etched using a chlorine-based gas to form a light-shielding film pattern. Furthermore, using the light-shielding film pattern as an etching mask, the phase-shift film made of silicon (Si) material is dry-etched using a fluorine-based gas to form a phase-shift film pattern. After that, the resist pattern is removed, and the light-shielding film pattern is removed by dry etching using a chlorine-based gas.

[0005] In this case, a light-shielding film is left outside the area where the phase-shift film pattern (circuit pattern) is formed, so that the outer edge of the phase-shift photomask becomes a light-shielding area (light-shielding pattern) with a combined optical density of 3 or more from the phase-shift film and the light-shielding film. This is to prevent exposure light from leaking from the outer edge of the phase-shift photomask and irradiating the resist film on adjacent chips on the wafer from the area located outside the circuit pattern when transferring the circuit pattern to the wafer using a wafer exposure apparatus. A common method for forming such a light-shielding pattern is to form a phase-shift film pattern, remove the resist pattern, then form a new resist film, and by pattern drawing and development, a resist pattern is formed in which the resist film remains on the outer edge of the light-shielding film. This resist pattern is then used as an etching mask to etch the light-shielding film formed from a chromium (Cr)-containing material, leaving the light-shielding film on the outer edge of the phase-shift photomask.

[0006] For phase-shift photomask blanks, where high-precision pattern formation is required, dry etching using gas plasma is the mainstream method. Dry etching of films formed from materials containing chromium (Cr) is performed using chlorine-based dry etching (chlorine-based dry etching), while dry etching of films formed from materials containing silicon (Si) or materials containing molybdenum and silicon is performed using fluorine-based dry etching (fluorine-based dry etching). In particular, for dry etching of films formed from materials containing chromium (Cr), it is known that dry etching using chlorine-based gas containing oxygen (O), specifically, by mixing 10 to 25 volume percent of oxygen gas (O2 gas) with chlorine gas (Cl2 gas), increases chemical reactivity and improves the etching rate.

[0007] As circuit patterns become smaller, techniques for forming finer circuit patterns on phase-shift photomasks are required. In particular, the assist patterns of line patterns that support the resolution of the main pattern of the phase-shift photomask need to be formed smaller than the main pattern so that they are not transferred to the wafer when the circuit pattern is transferred to the wafer using a wafer exposure apparatus. In the generation of phase-shift photomasks where the half-pitch of the line-and-space pattern on the wafer is 10 nm, the line width of the assist patterns of the circuit lines on the phase-shift photomask needs to be around 40 nm.

[0008] Chemically amplified resists, capable of forming fine patterns, consist of a base resin, an acid generator, a surfactant, and other components. Because many reactions in which the acid generated by exposure acts as a catalyst are applicable, high sensitivity is possible. Using chemically amplified resists enables the formation of mask patterns, such as fine phase-shift film patterns with line widths of 0.1 μm or less. The resist is applied onto a photomask blank by spin coating using a resist coating machine.

[0009] The typical thickness of resist films used in the manufacture of phase-shift photomasks is around 100-150 nm. However, with such thicknesses, it is difficult to form finer assist patterns on the phase-shift photomask. This is because, in thick resist films formed on a film made of chromium (Cr)-containing material, the aspect ratio of the resist pattern, which has a narrow line width for forming the assist pattern, is high. As a result, during the development process for resist pattern formation, the resist pattern can collapse due to impact from the developer or the pure water used during rinsing.

[0010] To minimize the impact of the developer or the pure water used during rinsing, it is necessary to reduce the aspect ratio of the resist pattern, which requires making the resist film thinner. However, if the resist film is thinned, and it disappears during the dry etching of a film made of chromium (Cr) material, defects such as pinholes will be formed in the chromium (Cr) material film. If a film made of silicon (Si) material is dry-etched using the pattern of a chromium (Cr) material film with pinholes and other defects as an etching mask, the plasma will reach the silicon (Si) material film through the pinholes during etching, and pinhole defects will be formed in the silicon (Si) material film as well. In this case, it is not possible to form a pattern of the silicon (Si) material film (phase-shift film) without defects, and a good photomask (phase-shift photomask) cannot be manufactured.

[0011] Therefore, to solve this problem, it was considered to use a hard mask film by further layering a film made of silicon (Si) material on top of a film made of chromium (Cr) material. In this case, the film made of silicon (Si) material is a thin film with a thickness of 5 to 15 nm, and the thickness of the resist film formed on the film made of silicon (Si) material can be reduced to about 80 to 110 nm.

[0012] When dry etching a film formed from a chromium (Cr)-containing material using a chlorine-based gas containing oxygen (O), it is necessary to perform over-etching by 100-300% of the clear time in addition to the clear time required for the chromium (Cr)-containing film to disappear. This is because dry etching using a chlorine-based gas containing oxygen (O) is an isotropic etching process dominated by chemical components. With dry etching only at the clear time, the pattern of the film formed from the chromium (Cr)-containing material will not be sufficiently etched at the boundary with the film formed from the silicon (Si)-containing material, resulting in a tapered shape and preventing the stable formation of the desired pattern width.

[0013] Furthermore, dry etching using oxygen (O)-containing chlorine-based gas is an isotropic etching process dominated by chemical components. Therefore, the plasma of oxygen (O)-containing chlorine-based gas moves perpendicularly and horizontally to the main surface of the substrate, causing side etching on the pattern of the film formed from chromium (Cr)-containing material. In order to make the pattern line width CD (Critical Dimension) uniform across the entire main surface of the photomask, and to ensure that the amount of side etching is equal across the entire main surface of the photomask, long-term over-etching is necessary until the amount of side etching saturates across the entire main surface of the photomask (until side etching stops progressing and the amount of side etching stabilizes).

[0014] On the other hand, dry etching using fluorine-based gas is used for dry etching of films formed from silicon (Si)-containing materials. When dry etching a film formed from silicon (Si)-containing materials using fluorine-based gas, in addition to the clear time until the silicon (Si)-containing film disappears, over-etching of up to 20% of the clear time (for example, a short over-etching of 1 to 6 seconds) is performed.

[0015] In dry etching of films formed with silicon (Si) materials using fluorine-based gas, over-etching is minimal because dry etching with fluorine-based gas is an anisotropic etching process dominated by physical components. This prevents the pattern of the silicon (Si)-based film from becoming saggy at the boundary with the chromium (Cr)-based film. Furthermore, the plasma of the fluorine-based gas moves perpendicular to the main surface of the substrate, ensuring that the CD of the resist pattern is faithfully reproduced on the silicon (Si)-based film pattern.

[0016] Dry etching using fluorine-based gases is an anisotropic etching process dominated by physical components. Therefore, the amount of resist lost during dry etching is generally greater than that lost during dry etching using chlorine-based gases containing oxygen (O). Consequently, a considerable thickness is required for the resist film used to form patterns on films made from silicon (Si)-containing materials. On the other hand, films made from silicon (Si)-containing materials function as an etching mask when dry etching films made from chromium (Cr)-containing materials using chlorine-based gases containing oxygen (O). Because silicon (Si)-containing films have sufficient etching resistance to dry etching using chlorine-based gases containing oxygen (O), the silicon (Si)-containing film used as a hard mask can be made relatively thin. If the silicon (Si)-containing film is thin, the dry etching time using fluorine-based gases on the silicon (Si)-containing film is shortened, and as a result, the resist film required to form patterns on the silicon (Si)-containing film can also be made thinner.

[0017] Furthermore, the increasingly demanded higher pattern resolution for projection lithography is no longer achievable even with transmission-type phase-shift photomasks. Therefore, in logic 7nm generation and beyond, EUV lithography, which uses extreme ultraviolet (EUV) light as the exposure light, has come into use.

[0018] Extreme ultraviolet (EUV) light is readily absorbed by all materials, making it impossible to use transmission lithography like conventional photolithography using ArF excimer laser light. Therefore, EUV lithography employs a reflective optical system. The wavelength of extreme ultraviolet light used in EUV lithography is 13-14 nm, while the wavelength of conventional ArF excimer laser light is 193 nm. Compared to conventional photolithography using ArF excimer laser light, EUV lithography has a shorter exposure wavelength, making it possible to transfer finer patterns on the photomask.

[0019] The photomasks used in EUV lithography are reflective photomasks in which exposure light is reflected by the photomask. Generally, they have a structure in which a reflective film that reflects extreme ultraviolet light, a protective film to protect the reflective film, and a light-absorbing film that absorbs extreme ultraviolet light are formed in this order on a substrate such as a glass substrate. As the reflective film, a multilayer reflective film is used in which the reflectivity when extreme ultraviolet light is irradiated onto the surface of the reflective film is increased by alternately stacking low refractive index layers and high refractive index layers. Typically, a molybdenum (Mo) layer is used as the low refractive index layer of the multilayer reflective film, and a silicon (Si) layer is used as the high refractive index layer. A ruthenium (Ru) film is usually used as the protective film. On the other hand, the light-absorbing film uses a material with a high absorption coefficient for extreme ultraviolet light, specifically, a material containing chromium (Cr) or tantalum (Ta) as the main component. In early generations of EUV lithography, a binary type reflective photomask was used in which there was no light reflection from the light-absorbing film.

[0020] On a substrate, a reflective film that reflects extreme ultraviolet light, a protective film for protecting the reflective film, and a light absorption film that absorbs extreme ultraviolet light are formed in this order. As a method for manufacturing a reflective photomask by patterning the light absorption film, specifically, the following method is generally used. First, a resist film is formed on the light absorption film, a pattern is drawn on this resist film by light or an electron beam, and it is developed to form a resist pattern. Next, using the resist pattern as an etching mask, the light absorption film is dry-etched to form a pattern of the light absorption film, and then the resist pattern is removed.

Prior Art Documents

Patent Documents

[0021]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0022] In EUV lithography, after the logic 3nm generation and later, in order to form finer patterns on the wafer, a reflective photomask (reflective phase shift photomask) having a pattern of a light absorption film with a phase shift function is used. By using a reflective phase shift photomask, higher wafer transfer characteristics can be obtained than those of a binary type reflective photomask. The wafer transfer characteristics can be represented by NILS (Normalized Image Log Slope), which corresponds to the contrast of the light intensity transferred to the wafer. NILS is expressed by the following formula NILS = (dI / dx) / (W × Ith) (In the formula, W is the desired pattern dimension, Ith is the threshold value of the light intensity that gives W, and dI / dx is the gradient of the aerial image.) It can be obtained by [NILS]. When the value of NILS is large, the optical image becomes steep, and the dimensional controllability of the resist pattern on the wafer is improved. Therefore, in order to form a finer pattern on the wafer, it is effective to have a large value of NILS, and a reflective phase shift photomask that can increase the value of NILS compared to a binary reflective photomask is used.

[0023] In EUV lithography using a reflective phase shift photomask, when the line and space sizes (pitches) of the line and space pattern on the wafer are 10 to 20 nm, the optimal focus value varies depending on the line and space sizes (pitches). When a line and space pattern with lines and spaces of different sizes (pitches) is mixed in one device circuit pattern, in order to form a good device circuit pattern in any line and space pattern, if the reflectivity of the light absorption film having a phase shift function with respect to the exposure light is about 5%, the difference in the optimal focus values of the line and space patterns with lines and spaces of different sizes (pitches) becomes smaller, and a device circuit pattern with a good line and space pattern can be formed.

[0024] Also, the light absorption film needs to have a thickness of a certain level or more that partially absorbs the exposure light to achieve a predetermined reflectivity. However, in a reflective photomask, the exposure light is incident obliquely on the reflective photomask and reflected obliquely. When the light absorption film is thick, the shadowing effect of the exposure light being blocked by the light absorption film becomes significant when the exposure light is incident and reflected. Therefore, in order to reduce the influence of the shadowing effect, it is advantageous to have a thinner light absorption film that can obtain a predetermined reflectivity.

[0025] In reflective photomasks required for EUV lithography, the assist pattern of line-and-space patterns, which helps to improve the resolution of the main pattern, becomes even smaller as the main pattern is miniaturized. The line width of the assist pattern needs to be reduced to about 30 nm, and especially to about 25 nm. Therefore, compared to conventional transmission-type phase-shift photomask blanks, reflective photomask blanks require even thinner resist films. In order to form the assist pattern of line-and-space patterns to about 30 nm, and especially to about 25 nm, in a reflective photomask, the thickness of the resist film needs to be 80 nm or less.

[0026] In EUV lithography, optical systems with an aperture number (NA) of 0.33 to 0.55 are used to form finer patterns on wafers. In this case, for reflective photomasks, the assist pattern that supports the resolution of the main line-and-space pattern becomes even smaller as the main pattern is miniaturized, and the line width of the assist pattern needs to be reduced to about 25 nm, and especially to about 20 nm. Therefore, it is necessary to further thin the resist film used in the reflective photomask blank for manufacturing reflective photomasks used in exposure machines with an aperture number of 0.55.

[0027] Furthermore, even if the assist pattern of the line-and-space pattern is fine, the fine line pattern disappears during the process of manufacturing the reflective photomask from the reflective photomask blank, making it impossible to obtain the desired pattern. Therefore, improving the resolution limit is also required.

[0028] For example, Japanese Patent Publication No. 2022-24617 (Patent Document 1) describes a reflective mask blank for EUV lithography in which a multilayer reflective film that reflects EUV light and a phase-shifting film that shifts the phase of EUV light are formed in this order on a substrate. The description states that the phase-shifting film has a layer containing ruthenium (Ru) and at least one selected from the group consisting of oxygen (O) and nitrogen (N), and that the full width at half maximum (FWHM) of the peak with the highest intensity among the diffraction peaks originating from the phase-shifting film observed in 2θ:20°~50° by out-of-plane XRD is 1.0° or more.

[0029] Japanese Patent Publication No. 2022-24617 (Patent Document 1) describes a layer containing ruthenium (Ru) and at least one selected from the group consisting of oxygen (O) and nitrogen (N), wherein the layer contains Ru and element (X) in a total of 40-99 at%, O in a range of 1-60 at%, Ru and element (X) in a total of 30-98 at%, O in a range of 1-69 at%, N in a range of 1-69 at%, or Ru and element (X) in a total of 30-90 at%, N in a range of 10-70 at%, with Ru:X being 20:1-1:5 (at%). Furthermore, elements (X) are described as chromium (Cr), tantalum (Ta), titanium (Ti), rhenium (Re), tungsten (W), bismuth (Bi), manganese (Mn), platinum (Pt), copper (Cu), iridium (Ir), and vanadium (V).

[0030] Japanese Patent Publication No. 2022-24617 (Patent Document 1) describes a phase shift film having a phase difference of 150 to 250 degrees and a relative reflectance of 2 to 37%. Furthermore, as a phase shift film with a reflectance of approximately 5% to exposure light, it describes a RuReON film with a phase difference of 216 degrees and a relative reflectance of 6.1% (Ru:Re:O:N=16:71:12:11(at%), Example 11), and a RuCrO film with a phase difference of 216 degrees, a relative reflectance of 7.3%, and a thickness of 40 nm (Ru:Cr:O=20:30:50(at%), Example 15).

[0031] However, the thickness of none of the phase-shift films has been sufficiently reduced. Furthermore, when correcting the pattern of a light-absorbing film formed on a reflective photomask, films containing ruthenium (Ru) can usually be etched by dry etching, which involves activating a fluorine-based gas with an electron beam. However, films containing large amounts of chromium (Cr) or rhenium (Re) cannot be effectively etched by dry etching, which involves activating a fluorine-based gas with an electron beam.

[0032] Japanese Patent Publication No. 2023-86742 (Patent Document 2) describes a reflective mask blank for EUV lithography in which a multilayer reflective film that reflects EUV light and a phase-shifting film that shifts the phase of EUV light are formed in this order on a substrate. It also describes that the surface roughness (rms) of the phase-shifting film is 0.50 nm or less, that the phase-shifting film has a layer 1 containing ruthenium (Ru) and nitrogen (N) and a film stress absolute value of 1000 MPa or less, a layer 2 containing element (X), that layer 2 may contain Ru and at least one of O and N, and that the Ru:X ratio is 20:1 to 1:5 (at%). Furthermore, the elements (X) listed are chromium (Cr), tantalum (Ta), titanium (Ti), rhenium (Re), tungsten (W), bismuth (Bi), manganese (Mn), platinum (Pt), copper (Cu), iridium (Ir), and vanadium (V).

[0033] Japanese Patent Publication No. 2023-86742 (Patent Document 2) describes that the phase difference of the phase-shift film is 150 to 250 degrees and the relative reflectance is 2 to 37%, but it does not specifically describe a phase-shift film with a reflectance of about 5% to exposure light. Furthermore, it does not describe layer 1 as a layer containing Ru, nor does it specifically describe layer 2 which contains ruthenium (Ru) along with element (X). In particular, if the phase-shift film includes layer 2, the phase-shift film will have a two-layer structure consisting of layer 1 which does not contain element (X) and layer 2 which contains element (X).

[0034] In this case, when correcting the pattern of the light-absorbing film formed on a reflective photomask, depending on the type of metallic element (X), dry etching using a fluorine-based gas activated by an electron beam may not effectively etch layer 2. This necessitates using multiple types of etching, employing different etching gases for layer 1 and layer 2, significantly reducing the success rate of correcting the light-absorbing film pattern compared to using a single type of etching.

[0035] On the other hand, even if layer 2 can be etched by dry etching, which involves activating a fluorine-based gas with an electron beam, the etching characteristics differ between layer 1, which does not contain element (X), and layer 2, which does contain element (X), particularly layer 2 containing a considerable amount of element (X). Therefore, controlling the etching process when modifying the pattern of the light-absorbing film is difficult, and modifying the pattern of the light-absorbing film is not easy.

[0036] Furthermore, in wafer exposure systems using extreme ultraviolet (UV) light, the UV light emitted from the light source is irradiated onto a reflective photomask via multiple mirrors and finally reaches the wafer. If the mirrors that reflect the UV light or the reflective photomask become contaminated with foreign matter, the amount of UV light reflected decreases, making it impossible to form the desired pattern on the wafer. In particular, the deposition of carbon-based foreign matter is a problem, and as a countermeasure, hydrogen gas is introduced into the wafer exposure system.

[0037] However, when hydrogen gas is irradiated with light in the extreme ultraviolet region, a hydrogen plasma containing hydrogen ions and hydrogen radicals is generated, and the reflective photomask is exposed to this hydrogen plasma. When the generated hydrogen plasma collides with the light-absorbing film or protective film, it penetrates the pattern of the light-absorbing film of the reflective photomask, reaches the interior of the protective film, or penetrates the protective film and becomes hydrogen gas at the interface between the protective film and the multilayer reflective film or inside the protective film. If the hydrogen gas accumulates as bubbles inside the protective film or at the interface between the protective film and the multilayer reflective film, the protective film expands or lifts in the areas swollen with hydrogen gas, and along with this, the pattern of the light-absorbing film lifts and deforms, resulting in defects. This defect is generally called a blister defect, and when a blister defect occurs in a reflective photomask, the reflectivity fluctuates locally, and furthermore, the patterns of the protective film and light-absorbing film are destroyed, making it impossible to form the desired pattern on the wafer.

[0038] In reflective photomasks required for EUV lithography, the line-and-space assist pattern, which helps improve the resolution of the main pattern, may need to be further reduced to about 20 nm in line width as the main pattern becomes smaller. Therefore, in reflective photomask blanks used with exposure machines with an aperture ratio of 0.55, further thinning of the resist film is necessary, as is the need to reduce the deterioration of resolution due to the disappearance of minute line patterns during the dry etching process.

[0039] Therefore, in order to improve the resolution of the light-absorbing film, a hard mask film is provided in contact with the light-absorbing film of the reflective photomass blank. The hard mask film is a thin film with a thickness of about 10 nm, and the thickness of the resist film formed in contact with the hard mask film can be made even thinner than 80 nm. In this case, even if the resist pattern has a narrow line width for forming the assist pattern, the aspect ratio is low, and the deformation of the resist pattern due to impact from the developer or pure water during rinsing in the resist pattern formation development process is suppressed, improving the resolution.

[0040] On the other hand, when using a hard mask film, the protective film is exposed to the dry etching plasma when the hard mask film is finally removed during the process of manufacturing a reflective photomask from a reflective photomask blank. Furthermore, in the patterning of light-absorbing films, the protective film is also exposed to the dry etching plasma in the final stage of patterning (over-etching). Therefore, the protective film needs to be formed from a material that is more resistant than the hard mask film or light-absorbing film in each dry etching process.

[0041] International Publication No. 2023 / 127799 (Patent Document 3) describes a protective film comprising an upper layer made of a rhodium-based material mainly composed of Rh, which includes Rh, or Rh and at least one element selected from the group consisting of N, O, C, B, Ru, Nb, Mo, Ta, Ir, Pd, Zr, and Ti, and a lower layer containing at least one element selected from the group consisting of Ru, Nb, Mo, Zr, Y, C, and B. However, ruthenium (Ru) and rhodium (Rh), which have been conventionally used as materials for protective films, are easily penetrated by hydrogen plasma containing hydrogen ions and hydrogen radicals, and there is a need for a protective film that is less likely to generate blister defects.

[0042] The present invention has been made to solve the above problems, and its first objective is to provide a reflective photomask having a protective film that is less likely to generate blister defects in an environment where extreme ultraviolet light is irradiated in the presence of hydrogen, and a reflective photomask blank from which such a reflective photomask can be manufactured. The second objective of the present invention is to provide a method for manufacturing a reflective photomask from a reflective photomask blank. [Means for solving the problem]

[0043] In order to solve the above problems, the inventors conducted extensive research on reflective photomask blanks and protective films for reflective photomasks, and found that the above problems can be solved by a protective film composed of multiple layers, each having a predetermined thickness, comprising one A layer containing rhodium (Rh), one or more B layers containing niobium (Nb) in a predetermined amount or more and not containing rhodium (Rh), and one or more C layers containing ruthenium (Ru) and not containing rhodium (Rh) or niobium (Nb), in a predetermined arrangement. Furthermore, in order to solve the above problems, the inventors conducted extensive research on reflective photomask blanks for manufacturing reflective photomasks, and found that the above problems can be solved by a reflective photomask blank equipped with a hard mask film formed in contact with a light-absorbing film.

[0044] Furthermore, the inventors have conducted extensive research on reflective photomask blanks and reflective photomask light-absorbing films, and have found that by constructing the light-absorbing film as a single or multilayer made of a material containing ruthenium (Ru) and platinum (Pt), it is possible to create a thinner light-absorbing film with high wafer transfer characteristics (high NILS value), small difference in optimal focus values ​​for line-and-space patterns of different sizes (pitches), a reflectivity of about 5%, the ability to be completely removed by etching with a fluorine-based gas, easy pattern modification, and minimal shadowing effect. This led to the present invention.

[0045] Accordingly, the present invention provides the following reflective photomasks, reflective photomask blanks, and methods for manufacturing reflective photomasks. 1. Circuit board and, A multilayer reflective film formed on the substrate that reflects exposure light, which is light in the extreme ultraviolet region, A protective film is formed on the multilayer reflective film in contact with the multilayer reflective film to protect the multilayer reflective film, A pattern of a light-absorbing film formed on the protective film in contact with the protective film and absorbing the exposure light and Equipped with, The protective film is composed of a multilayer including one A layer, one or more B layers, and one or more C layers. The A layer of the protective film contains rhodium (Rh) and has a thickness of 0.5 nm or more and 2 nm or less. The B layer of the protective film contains niobium (Nb) but does not contain rhodium (Rh), the niobium (Nb) content is 10 atomic percent or more, and the thickness is 0.5 nm or more and 2 nm or less. The C layer of the protective film contains ruthenium (Ru), does not contain rhodium (Rh) or niobium (Nb), and has a thickness of 0.5 nm or more and 2 nm or less. The A layer of the protective film is in contact with the pattern of the light-absorbing film. One of the C layers of the protective film is in contact with the multilayer reflective film. A reflective photomask characterized by the following features. 2. The reflective photomask according to claim 1, characterized in that the protective film is composed of a multilayer consisting of the A layer, the B layer and the C layer. 3. The reflective photomask according to claim 2, characterized in that the protective film is composed of a multilayer consisting of three layers, the A layer, the B layer, and the C layer, from the side away from the substrate, or a multilayer consisting of five layers, the A layer, the B layer, the C layer, the B layer, and the C layer, from the side away from the substrate. 4. The light-absorbing film is composed of a single layer or a multilayer, and each layer of the single layer or multilayer contains ruthenium (Ru) and platinum (Pt), with a ruthenium (Ru) content of 30 atomic% to 70 atomic%, a platinum (Pt) content of 30 atomic% to 70 atomic%, and a total content of ruthenium (Ru) and platinum (Pt) of 96 atomic% or more. The thickness of the aforementioned light absorption film is 32 nm or more and 38 nm or less. The reflectance of the light-absorbing film to the exposure light is 1% or more and 8% or less, and the phase difference with respect to the exposure light is 190 degrees or more and 240 degrees or less. A reflective photomask according to claim 1, characterized in that it is a reflective photomask. 5. Circuit board and, A multilayer reflective film formed on the substrate that reflects exposure light, which is light in the extreme ultraviolet region, A protective film is formed on the multilayer reflective film in contact with the multilayer reflective film to protect the multilayer reflective film, A light-absorbing film is formed on the protective film in contact with the protective film and absorbs the exposure light, A hard mask film formed on the light-absorbing film in contact with the light-absorbing film, Equipped with, The protective film is composed of a multilayer including one A layer, one or more B layers, and one or more C layers. The A layer of the protective film contains rhodium (Rh) and has a thickness of 0.5 nm or more and 2 nm or less. The B layer of the protective film contains niobium (Nb) but does not contain rhodium (Rh), the niobium (Nb) content is 10 atomic percent or more, and the thickness is 0.5 nm or more and 2 nm or less. The C layer of the protective film contains ruthenium (Ru), does not contain rhodium (Rh) or niobium (Nb), and has a thickness of 0.5 nm or more and 2 nm or less. The A layer of the protective film is in contact with the light-absorbing film. One of the C layers of the protective film is in contact with the multilayer reflective film. A reflective photomask blank characterized by the following features. 6. The reflective photomask blank according to claim 5, characterized in that the protective film is composed of a multilayer consisting of the A layer, the B layer, and the C layer. 7. The reflective photomask blank according to 6, characterized in that the protective film is composed of a multilayer consisting of three layers, the A layer, the B layer, and the C layer, from the side away from the substrate, or a multilayer consisting of five layers, the A layer, the B layer, the C layer, the B layer, and the C layer, from the side away from the substrate. 8. The light-absorbing film is composed of a single layer or a multilayer, and each layer of the single layer or multilayer contains ruthenium (Ru) and platinum (Pt), with a ruthenium (Ru) content of 30 atomic% to 70 atomic%, a platinum (Pt) content of 30 atomic% to 70 atomic%, and a total content of ruthenium (Ru) and platinum (Pt) of 96 atomic% or more. The thickness of the aforementioned light absorption film is 32 nm or more and 38 nm or less. The reflectance of the light-absorbing film to the exposure light is 1% or more and 8% or less, and the phase difference with respect to the exposure light is 190 degrees or more and 240 degrees or less. A reflective photomask blank according to claim 5, characterized in that it is a reflective photomask blank. 9. The reflective photomask blank according to 5, characterized in that the hard mask film includes a first layer that is in contact with the light absorption film and functions as an etching mask when the light absorption film is patterned by dry etching, and the first layer of the hard mask film is made of a material that is resistant to dry etching using a fluorine-based gas and can be removed by dry etching using a chlorine-based gas. 10. The reflective photomask blank according to 9, wherein the hard mask film includes a second layer that is in contact with the first layer of the hard mask film and functions as an etching mask when the first layer of the hard mask film is patterned by dry etching, and the second layer of the hard mask film is made of a material that is resistant to dry etching using a chlorine-based gas and can be removed by dry etching using a fluorine-based gas. A method for manufacturing a reflective photomask as described in 1 from a reflective photomask blank as described in 11.9, [A1] A step of forming a resist film in contact with the side of the first layer of the hard mask film that is separated from the substrate, [B] A step of patterning the resist film to form a resist pattern, [C1] Using the resist pattern as an etching mask, the first layer of the hard mask film is patterned by dry etching using a chlorine-based gas to form a pattern on the first layer of the hard mask film. [D] A step of removing the resist pattern, [F1] A step of forming a pattern in the light-absorbing film by dry etching using a fluorine-based gas, with the pattern of the first layer of the hard mask film as an etching mask. [G1] A step of removing the pattern of the first layer of the hard mask film by dry etching using a chlorine-based gas. A method for manufacturing a reflective photomask, characterized by including the following: A method for manufacturing a reflective photomask as described in 1 from a reflective photomask blank as described in 12.10, [A2] A step of forming a resist film in contact with the side of the second layer of the hard mask film that is separated from the substrate, [B] A step of patterning the resist film to form a resist pattern, [C2] Using the resist pattern as an etching mask, the second layer of the hard mask film is patterned by dry etching using a fluorine-based gas to form a pattern for the second layer of the hard mask film. [D] A step of removing the resist pattern, [E2] A step of forming the pattern of the first layer of the hard mask film by dry etching using a chlorine-based gas, using the pattern of the second layer of the hard mask film as an etching mask, [F2] Using the pattern of the first layer of the hard mask film as an etching mask, the light-absorbing film is patterned by dry etching using a fluorine-based gas to form the pattern of the light-absorbing film, and the pattern of the second layer of the hard mask film is removed. [G2] A step of removing the pattern of the first layer of the hard mask film by dry etching using a chlorine-based gas. A method for manufacturing a reflective photomask, characterized by including the following: [Effects of the Invention]

[0046] According to the present invention, it is possible to provide a reflective photomask equipped with a protective film that is less likely to generate blister defects in environments where extreme ultraviolet light is irradiated in the presence of hydrogen. Furthermore, according to the present invention, it is possible to thin the resist film used for pattern formation of light-absorbing films, and a reflective photomask blank with an improved resolution limit in pattern formation of light-absorbing films can be provided.

[0047] In particular, if the light-absorbing film is formed from a material containing ruthenium (Ru) and platinum (Pt), it is possible to provide a reflective photomask with a thinner light-absorbing film that has high wafer transfer characteristics (high NILS value), a small difference in optimal focus values ​​for line-and-space patterns of different sizes (pitches), a reflectivity of about 5%, can be completely removed by etching with a fluorine-based gas, allows for easy pattern modification, and has a small shadowing effect. [Brief explanation of the drawing]

[0048] [Figure 1] This is a cross-sectional view showing an example of a first embodiment of the reflective photomask blank of the present invention. [Figure 2] This is a cross-sectional view showing an example of a second embodiment of the reflective photomask blank of the present invention. [Figure 3] This is a cross-sectional view showing an example of a third embodiment of the reflective photomask blank of the present invention. [Figure 4] This is a cross-sectional view showing an example of a fourth embodiment of the reflective photomask blank of the present invention. [Figure 5] This is a cross-sectional view showing an example of a reflective photomask of the present invention. [Figure 6] This is a cross-sectional view illustrating an example of a process for manufacturing a reflective photomask from a reflective photomask blank according to the first or third aspect of the present invention. [Figure 7] This is a cross-sectional view illustrating an example of a process for manufacturing a reflective photomask from a reflective photomask blank according to a second or fourth aspect of the present invention. [Modes for carrying out the invention]

[0049] The present invention will be described in more detail below. The reflective photomask of the present invention comprises a substrate, a multilayer reflective film formed on the substrate, a protective film formed on the multilayer reflective film, and a pattern of a light-absorbing film formed on the protective film. The reflective photomask of the present invention also comprises a substrate, a multilayer reflective film formed on the substrate, a protective film formed on the multilayer reflective film, a light-absorbing film formed on the protective film, and a hard mask film formed on the light-absorbing film. The protective film is composed of a multilayer including layer A, layer B, and layer C. The hard mask film preferably includes a first layer that functions as an etching mask when forming a pattern of the light-absorbing film by dry etching. The hard mask film more preferably further includes a second layer that functions as an etching mask when forming a pattern of the first layer of the hard mask film by dry etching.

[0050] When a reflective photomask is held on the mask stage of an exposure apparatus, it is usually fixed by an electrostatic chuck. Therefore, the reflective photomask blank and reflective photomask of the present invention may have a conductive film (back surface film) on the back surface of the substrate (the surface opposite to the surface on which the multilayer reflective film is formed) for fixing the reflective photomask by an electrostatic chuck. Furthermore, the reflective photomask blank of the present invention may further have a resist film formed directly or via another film on the hard mask film.

[0051] From the reflective photomask blank of the present invention, for example, a reflective photomask can be obtained comprising a substrate, a multilayer reflective film formed on the substrate, a protective film formed on the multilayer reflective film, and a pattern (circuit pattern or photomask pattern) of a light-absorbing film formed on the protective film.

[0052] The structure of the reflective photomask blank and reflective photomask of the present invention will be described below with reference to the drawings. In the description of the drawings, identical components may be given the same reference numerals and their description may be omitted. Also, for convenience, the drawings may be shown in an enlarged form, and the dimensional ratios of each component may not necessarily be the same as in reality.

[0053] Figure 1 is a cross-sectional view showing an example of a first embodiment of the reflective photomask blank of the present invention. This reflective photomask blank 100 includes a substrate 1, a multilayer reflective film 2 formed on the substrate 1 in contact with the substrate 1, a protective film 3 formed on the multilayer reflective film 2 in contact with the multilayer reflective film 2, a light-absorbing film 4 formed on the protective film 3 in contact with the protective film 3, and a hard mask film 5 formed on the light-absorbing film 4 in contact with the light-absorbing film 4. In this case, the protective film 3 is composed of three layers: an A layer 31 in contact with the light-absorbing film 4, a C layer 33 in contact with the multilayer reflective film 2, and a B layer 32 in contact with the A layer 31 and the C layer 33. The hard mask film 5 is composed of only the first layer 51.

[0054] Figure 2 is a cross-sectional view showing an example of a second embodiment of the reflective photomask blank of the present invention. This reflective photomask blank 200 includes a substrate 1, a multilayer reflective film 2 formed on the substrate 1 in contact with the substrate 1, a protective film 3 formed on the multilayer reflective film 2 in contact with the multilayer reflective film 2, a light-absorbing film 4 formed on the protective film 3 in contact with the protective film 3, and a hard mask film 5 formed on the light-absorbing film 4 in contact with the light-absorbing film 4. In this case, the protective film 3 is composed of three layers: an A layer 31 in contact with the light-absorbing film 4, a C layer 33 in contact with the multilayer reflective film 2, and a B layer 32 in contact with the A layer 31 and the C layer 33. The hard mask film 5 is composed of two layers: a first layer 51 formed in contact with the light-absorbing film 4, and a second layer formed in contact with the first layer 51.

[0055] Figure 3 is a cross-sectional view showing an example of a third embodiment of the reflective photomask blank of the present invention. In this reflective photomask blank 101, a resist film 6 is formed in contact with the first layer 51 of the hard mask film 5 of the reflective photomask blank 100 of the first embodiment.

[0056] Figure 4 is a cross-sectional view showing an example of a fourth embodiment of the reflective photomask blank of the present invention. In this reflective photomask blank 201, a resist film 6 is formed in contact with the second layer 52 of the hard mask film 5 of the reflective photomask blank 200 of the second embodiment.

[0057] Figure 5 is a cross-sectional view showing an example of a reflective photomask of the present invention. This reflective photomask 300 includes a substrate 1, a multilayer reflective film 2 formed on the substrate 1 in contact with the substrate 1, a protective film 3 formed on the multilayer reflective film 2 in contact with the multilayer reflective film 2, and a light-absorbing film pattern 4a formed on the protective film 3 in contact with the protective film 3. In this case, the protective film 3 is composed of three layers: an A layer 31 in contact with the light-absorbing film pattern 4a, a C layer 33 in contact with the multilayer reflective film 2, and a B layer 32 in contact with the A layer 31 and the C layer 33.

[0058] There are no particular restrictions on the type or size of the substrate, and the substrates for the reflective photomask blank and reflective photomask may be transparent or opaque at the exposure wavelength. For example, glass substrates such as quartz substrates can be used. Alternatively, a substrate called a 6025 substrate, which is 6 inches square and 0.25 inches thick as defined in the SEMI standard, is preferred. When using the SI unit system, a 6025 substrate is usually described as a substrate with dimensions of 152 mm square and 6.35 mm thickness.

[0059] A multilayer reflective film is a film that reflects exposure light, which is light in the extreme ultraviolet region. Preferably, the multilayer reflective film is formed in contact with the substrate. This extreme ultraviolet region light is called EUV light, and the wavelength of EUV light is 13-14 nm, typically around 13.5 nm.

[0060] The material used to form the multilayer reflective film is preferably resistant to dry etching using chlorine-based gases (chlorine-based dry etching), and in particular, to dry etching using a mixed gas of chlorine gas (Cl2 gas) and oxygen gas (O2 gas) (dry etching using a chlorine-based gas containing oxygen (O)).

[0061] Specific examples of materials used to form multilayer reflective films include silicon (Si) and molybdenum (Mo). Generally, multilayer films (Si / Mo multilayer films) are used in which silicon (Si) layers and molybdenum (Mo) layers are alternately stacked in approximately 20 to 60 layers.

[0062] The thickness of the multilayer reflective film is preferably 200 nm or more, more preferably 220 nm or more, and also preferably 340 nm or less, more preferably 280 nm or less. The thickness of the silicon (Si) layer is preferably 2 nm or more, more preferably 3 nm or more, and also preferably 6 nm or less, more preferably 5 nm or less. The thickness of the molybdenum (Mo) layer is preferably 1 nm or more, more preferably 2 nm or more, and also preferably 5 nm or less, more preferably 4 nm or less.

[0063] The protective film is a film for protecting the multilayer reflective film. The protective film is preferably formed in contact with the multilayer reflective film. The protective film is provided to protect the multilayer reflective film during processes such as cleaning of a reflective photomask, cleaning of the reflective photomask, and modification of the pattern of the light-absorbing film. Furthermore, it is preferable that the protective film has the function of protecting the multilayer reflective film when patterning the light-absorbing film by etching, and preventing oxidation of the multilayer reflective film.

[0064] From the viewpoint of suppressing blister defects, it is effective for the protective film to have a structure and composition that allows a portion of the hydrogen plasma containing hydrogen ions and hydrogen radicals to be released outside the protective film before it reaches the multilayer reflective film, and that prevents hydrogen gas from accumulating as bubbles even if a portion of the hydrogen plasma reaches the multilayer reflective film. For this purpose, it is preferable that the protective film be composed of a multilayer including one A layer, one or more B layers, and one or more C layers. The A layer of the protective film is a layer in contact with the light-absorbing film or the pattern of the light-absorbing film. One of the C layers of the protective film is a layer in contact with the multilayer reflective film. The B layer of the protective film is provided between the A layer and the C layer in contact with the multilayer reflective film. It is preferable that the A layer is in contact with the B layer. The B layer can be in contact with any of the A, B, and C layers. It is preferable that the B layer is in contact with the A and C layers, or sandwiched between two C layers. The C layer can be in contact with any of the B and C layers. It is preferable that the C layer is in contact with the B layer or sandwiched between two B layers. In particular, it is preferable that the C layer in contact with the multilayer reflective film is in contact with the B layer.

[0065] The materials forming the protective film (each layer constituting the protective film), at least the material forming layer A of the protective film, preferably the materials forming layers A and B of the protective film, are preferably resistant to dry etching using chlorine-based gas (chlorine-based dry etching), and in particular to dry etching using a mixed gas of chlorine gas (Cl2 gas) and oxygen gas (O2 gas) as the chlorine-based gas (dry etching using a chlorine-based gas containing oxygen (O)). Furthermore, the materials forming the protective film (each layer constituting the protective film), at least the material forming layer A of the protective film, preferably the materials forming layers A and B of the protective film, are preferably resistant to cleaning solutions containing sulfuric acid or cleaning solutions containing alkali.

[0066] The materials forming the protective film (each layer constituting the protective film), at least the material forming layer A of the protective film, preferably the materials forming layers A and B of the protective film, are preferably materials that are less susceptible to etching than a light-absorbing film when etched by dry etching, which is performed by activating a fluorine-based gas with an electron beam.

[0067] Since the protective film layer A is exposed during the manufacturing and use of the reflective photomask, it is necessary that it be made of a material that has resistance to dry etching and cleaning solutions. Preferably, layer A is made of a material that allows substantially all of the hydrogen plasma that enters layer A to penetrate and reach layer B.

[0068] Specifically, materials that form layer A include, for example, materials containing rhodium (Rh). The material forming layer A may be pure rhodium (Rh) or a rhodium (Rh) compound containing rhodium (Rh) and another metal, such as ruthenium (Ru). The material forming layer A may be a rhodium (Rh) compound containing oxygen (O), nitrogen (N), carbon (C), etc., but it is preferable to be pure rhodium (Rh) or a rhodium (Rh) compound consisting of rhodium (Rh) and another metal, such as ruthenium (Ru). Examples of rhodium (Rh) compounds for the material forming layer A include rhodium-ruthenium (RhRu) and rhodium-niobruthenium (RhNbRu). The rhodium (Rh) content of layer A is preferably 40 atomic% or more, more preferably 50 atomic% or more. When layer A is a rhodium (Rh) compound, the rhodium (Rh) content is less than 100 atomic percent, preferably 95 atomic percent or less, and more preferably 90 atomic percent or less.

[0069] It is preferable that the protective film's B layer is made of a material that allows some of the hydrogen plasma that penetrates the A layer and enters the B layer to penetrate to the substrate-side layer (another B layer or C layer), while the remainder is returned to the layer moving away from the substrate (A layer, another B layer, or C layer) without penetrating. If the B layer completely blocks the hydrogen plasma, hydrogen gas will accumulate as bubbles at the interface between the B layer and the layer moving away from the substrate (A layer, another B layer, or C layer), causing blister defects. Therefore, it is preferable that the B layer is made of a material that does not completely block the hydrogen plasma. If only a portion of the hydrogen plasma does not penetrate the B layer, hydrogen gas will not accumulate to the point of forming bubbles, and the hydrogen plasma that did not penetrate the B layer will return to the layer moving away from the substrate, and the returned hydrogen plasma will be released outside the protective film through the layer moving away from the substrate. In this way, it can be said that the B layer has the function of adjusting the amount of hydrogen plasma that reaches the substrate-side layer.

[0070] Specific examples of materials that form layer B include materials containing niobium (Nb). The material forming layer B may be pure niobium (Nb) or a niobium (Nb) compound containing niobium (Nb) and another metal, such as ruthenium (Ru), but it is preferable that it does not contain rhodium (Rh). The material forming layer B may also be a niobium (Nb) compound containing oxygen (O), nitrogen (N), carbon (C), etc. Examples of niobium (Nb) compounds for the material forming layer B include niobruthenium (NbRu) and niobium oxide (NbO). The niobium (Nb) content of layer B is preferably 10 atomic% or more, more preferably 15 atomic% or more. Furthermore, if layer B is a niobium (Nb) compound, the niobium (Nb) content is less than 100 atomic%, preferably 95 atomic% or less, more preferably 90 atomic% or less.

[0071] It is preferable that the protective C layer is made of a material that allows substantially all of the hydrogen plasma that penetrates through layers A and B into the C layer to reach the substrate-side layer or film (layer B, other C layers, or multilayer reflective film). If the C layer completely blocks the hydrogen plasma, hydrogen gas will accumulate as bubbles at the interface between the C layer and the layer separating from the substrate (layer B or other C layers), causing blister defects. Therefore, it is preferable that the C layer is made of a material that does not completely block the hydrogen plasma. The hydrogen plasma that penetrates through layers A and B into the C layer is reduced compared to the hydrogen plasma that initially entered layer A due to the presence of layer B. The hydrogen plasma that penetrates the C layer reaches the substrate layer or film. If the C layer is in contact with a multilayer reflective film, some of it reacts with the surface layer of the multilayer reflective film, but the remainder does not accumulate enough hydrogen gas to form bubbles. If the C layer is in contact with the B layer or a multilayer reflective film, the hydrogen plasma that penetrates the C layer returns to the layer away from the substrate, and the returned hydrogen plasma is released outside the protective film through the layer away from the substrate. The C layer of the protective film can be said to be a layer that complements the function of suppressing blister defects in the A and B layers.

[0072] Specific examples of materials that form the C layer of the protective film include materials containing ruthenium (Ru). The material forming the C layer of the protective film may be pure ruthenium (Ru) or a ruthenium (Ru) compound containing ruthenium (Ru) and other metals, but it is preferable that it does not contain rhodium (Rh) and also niobium (Nb). The material forming the C layer of the protective film may contain oxygen (O), nitrogen (N), carbon (C), etc., but it is preferable that it is pure ruthenium (Ru) or a ruthenium (Ru) compound consisting of ruthenium (Ru) and other metals (preferably excluding rhodium (Rh) and niobium (Nb)). The ruthenium (Ru) content of the C layer of the protective film is preferably 90 atomic% or more, more preferably 95 atomic% or more. When the C layer of the protective film is a ruthenium (Ru) compound, the ruthenium (Ru) content is less than 100 atomic percent, preferably 98 atomic percent or less, and more preferably 97 atomic percent or less.

[0073] The protective C layer is not typically exposed during the manufacturing or use of reflective photomasks, so it does not need to have resistance to dry etching or cleaning solutions.

[0074] The protective film may be a multilayer containing a total of three or more layers of A, B, and C layers. For example, it may be a multilayer containing a total of 3 to 10 layers of A, B, and C layers. It is more preferable that the protective film is a multilayer consisting of A, B, and C layers. Examples of protective films include a multilayer consisting of three layers (A, B, and C layers) from the side away from the substrate, and a multilayer consisting of five layers (A, B, C, B, and C layers) from the side away from the substrate. The B layer may consist of two or more B layers with different compositions adjacent to each other, and the C layer may consist of two or more C layers with different compositions adjacent to each other. Specific examples of such films include a multilayer consisting of four layers (A, B, B, and C layers) from the side away from the substrate, a multilayer consisting of four layers (A, B, C, and C layers) from the side away from the substrate, and a multilayer consisting of five layers (A, B, B, C, and C layers) from the side away from the substrate. Furthermore, the protective film may be a film having a gradient composition.

[0075] The thinner the protective film (overall thickness), the higher the reflectivity of the exposure light from the multilayer reflective film of the reflective photomask. This allows more exposure light to be irradiated onto the wafer during exposure using a reflective photomask, improving productivity. On the other hand, if the protective film is too thin, it may be lost during the manufacturing or use of the reflective photomask due to dry etching or cleaning solutions, or its function of protecting the multilayer reflective film as a protective film may be lost. Therefore, the thickness of the protective film is preferably 1.5 nm or more, more preferably 2 nm or more, and preferably 6 nm or less, more preferably 4 nm or less.

[0076] Furthermore, for the same reasons as the thickness of the protective film (total thickness), the thickness of each layer constituting the protective film is preferably 0.5 nm or more, more preferably 0.8 nm or more, and also preferably 2 nm or less, more preferably 1.5 nm or less. Moreover, the total thickness of layers A, B, and C in the protective film (including all of each layer if layers B and C include multiple layers) is preferably 40% or more, more preferably 60% or more, even more preferably 75% or more, and particularly preferably 100% of the thickness of the protective film (total thickness).

[0077] By making the protective film have such a structure and composition, a portion of the hydrogen plasma is released outside the protective film before it reaches the multilayer reflective film, and even if a portion of the hydrogen plasma does reach the multilayer reflective film, the hydrogen gas does not accumulate as bubbles, thereby suppressing blister defects.

[0078] The combined reflectivity of the multilayer reflective film and protective film to exposure light is preferably 63.5% or higher, and more preferably 64% or higher, because a higher reflectivity allows more exposure light to be used for photolithography.

[0079] A light-absorbing film is a film that absorbs exposure light, which is light in the extreme ultraviolet region. Light-absorbing films are usually formed in contact with a protective film. A light-absorbing film may consist of a single layer or multiple layers (e.g., 2 to 5 layers). Furthermore, a light-absorbing film may have a gradient composition.

[0080] The material used to form the light-absorbing film is preferably a material that can be etched by dry etching using a fluorine-based gas (for example, sulfur hexafluoride gas (SF6), carbon tetrafluoride gas (CF4), etc.), specifically by dry etching using a mixed gas of sulfur hexafluoride gas (SF6) and helium gas (He). Furthermore, the material used to form the light-absorbing film is preferably a material that is resistant to dry etching using a chlorine-based gas (chlorine-based dry etching), and in particular, to dry etching using a mixed gas of chlorine gas (Cl2 gas) and oxygen gas (O2 gas) as the chlorine-based gas (dry etching using a chlorine-based gas containing oxygen (O)).

[0081] The light-absorbing film preferably contains ruthenium (Ru) and one or more metals selected from platinum (Pt), niobium (Nb), iridium (Ir), chromium (Cr), tantalum (Ta), and molybdenum (Mo). The light-absorbing film may also contain one or more elements selected from oxygen (O), nitrogen (N), carbon (C), and boron (B).

[0082] It is more preferable that the light-absorbing film contains ruthenium (Ru) and platinum (Pt). If the light-absorbing film is composed of multiple layers, it is preferable that each layer constituting the multilayer contains both ruthenium (Ru) and platinum (Pt). Specifically, examples of materials for forming the light-absorbing film (single layers and each layer constituting the multilayer) include ruthenium-platinum (RuPt). Furthermore, since the light-absorbing film is exposed to the atmosphere in storage environments and wafer exposure environments after being made from a reflective photomask blank into a reflective photomask, it is advantageous in terms of resistance to oxygen contained in the atmosphere to contain niobium (Nb) along with ruthenium (Ru) and platinum (Pt). Specifically, examples of materials containing niobium (Nb) include ruthenium-platinum-niobium (RuPtNb). The light-absorbing film (each layer constituting the single-layer and multi-layer) may contain one or more elements selected from oxygen (O), nitrogen (N), carbon (C), and boron (B), but is preferably composed of ruthenium (Ru) and platinum (Pt), or ruthenium (Ru), platinum (Pt), and niobium (Nb).

[0083] The ruthenium (Ru) content in the material forming the light-absorbing film (each layer constituting the single-layer and multi-layer) is preferably 30 atomic% or more, more preferably 40 atomic% or more, and also preferably 70 atomic% or less, more preferably 60 atomic% or less. The platinum (Pt) content in the material forming the light-absorbing film (each layer constituting the single-layer and multi-layer) is preferably 30 atomic% or more, more preferably 40 atomic% or more, and also preferably 70 atomic% or less, more preferably 60 atomic% or less. Furthermore, the total content of ruthenium (Ru) and platinum (Pt) is preferably 96 atomic% or more, more preferably 97 atomic% or more, and may be 100 atomic%. If the light-absorbing film contains niobium (Nb), the niobium (Nb) content in the light-absorbing film is preferably 4 atomic% or less, more preferably 3 atomic% or less. In this case, the lower limit of the niobium (Nb) content is greater than 0 atomic%, and is not particularly limited, but is preferably 1 atomic% or more.

[0084] In the present invention, the light-absorbing film may be a film that does not have a phase-shift function (a film that does not substantially reflect exposure light), or it may be a film that has a phase-shift function, i.e., a phase-shift film, but it is preferable that it is a film that has a phase-shift function. A light-absorbing film that has a phase-shift function is a film that absorbs a portion of the exposure light, and reflects the remainder with its phase changed (shifted) relative to the phase of the exposure light reflected from the multilayer reflective film, thereby obtaining a phase-shift function due to the phase difference between the light reflected from the multilayer reflective film and the light reflected from the light-absorbing film.

[0085] The reflective photomask blank and reflective photomask of the present invention can be referred to as a binary type reflective photomask blank and a binary type reflective photomask, respectively, when the light-absorbing film is a light-absorbing film that does not have a phase-shift function. On the other hand, when the light-absorbing film is a light-absorbing film that has a phase-shift function, they can be referred to as a reflective photomask blank with a phase-shift function (reflective phase-shift photomask blank) and a reflective photomask with a phase-shift function (reflective phase-shift photomask), respectively. By having a light-absorbing film with a phase-shift function, wafer transfer characteristics (NILS) can be improved.

[0086] When a light-absorbing film with phase-shifting functionality (phase-shift film) has high reflectivity to exposure light in the extreme ultraviolet region, the optimal focus value tends to vary greatly depending on the size (pitch) of the line-and-space pattern on the wafer. If the optimal focus value varies greatly depending on the size (pitch) of the line-and-space pattern on the wafer, it becomes impossible to provide line-and-space patterns of different sizes (pitches) on a single device circuit pattern, severely limiting the design of the photomask.

[0087] When line-and-space patterns of different sizes (pitches) are mixed in a single device circuit pattern, from the viewpoint of obtaining a good device circuit pattern for all line-and-space patterns, the reflectivity of the light-absorbing film (phase-shift film) having a phase-shift function to exposure light, which is in the extreme ultraviolet region, is preferably 1% or more, more preferably 2% or more, and also preferably 8% or less, preferably 7% or less, and even more preferably 6% or less. If the light-absorbing film has such reflectivity, the difference in the optimal focus value of line-and-space patterns of different sizes (pitches) becomes small, which is advantageous when line-and-space patterns of different sizes (pitches) are provided in a single device circuit pattern.

[0088] This reflectance is the relative reflectance to the portion where no light-absorbing film is formed. Specifically, it is the ratio of the reflectance of light reflected from the light-absorbing film formed on the substrate via the multilayer reflective film and protective film to the reflectance of light reflected from the multilayer reflective film and protective film formed on the substrate.

[0089] A light-absorbing film having a phase-shift function (phase-shift film) has a phase difference with respect to exposure light, which is in the extreme ultraviolet region, preferably 190 degrees or more, more preferably 200 degrees or more, and also preferably 240 degrees or less, more preferably 230 degrees or less. This phase difference is the relative phase difference with respect to the portion where the light-absorbing film is not formed, and specifically, it is the difference between the phase of light reflected from the multilayer reflective film and protective film formed on the substrate and the phase of light reflected from the light-absorbing film formed on the substrate via the multilayer reflective film and protective film.

[0090] The thickness of the light-absorbing film is preferably 32 nm or more, more preferably 34 nm or more, and more preferably 38 nm or less, more preferably 37 nm or less, and even more preferably 36 nm or less, from the viewpoint of minimizing the influence of the shadowing effect, and especially when the light-absorbing film is a light-absorbing film having a phase-shift function, from the viewpoint of ensuring both the light-absorbing function and the phase-shift function.

[0091] If the pattern of the light-absorbing film does not conform to the desired shape, correction is performed. For correction of reflective photomasks, electron beam correction, which offers good processing accuracy for photomask patterns, is primarily used. For electron beam correction of light-absorbing films formed from materials containing ruthenium (Ru) and platinum (Pt), fluorine-based gases such as xenon fluoride gas (XeF2) are used. Dry etching, which involves activating the fluorine-based gas with an electron beam and etching, allows for the processing of minute areas and correction of the light-absorbing film pattern. It is preferable that the light-absorbing film be formed from a material that can be corrected solely by dry etching, which involves activating the fluorine-based gas with an electron beam and etching. Furthermore, it is preferable that the structure be such that it can be corrected solely by dry etching, which involves activating the fluorine-based gas with an electron beam and etching. Examples of such materials include single-layer light-absorbing films and multilayer films (e.g., 2 to 5 layers) composed of layers with equivalent or similar etching characteristics.

[0092] Furthermore, in the manufacturing process of reflective photomasks, multiple cleaning steps may be performed to remove foreign matter from the photomask. Therefore, the thickness of the protective film immediately after forming the light-absorbing film pattern from the reflective photomask is preferably 1.1 nm or more, more preferably 1.2 nm or more, even more preferably 2 nm or more, and particularly preferably 2.2 nm or more.

[0093] A hard mask film is a film that functions as an etching mask in the etching of a light-absorbing film. The hard mask film is usually formed in contact with the light-absorbing film. The hard mask film may consist of a single layer or multiple layers (e.g., two, three, four, or five layers). Furthermore, the hard mask film may have a gradient composition.

[0094] The hard mask film preferably includes a first layer that is in contact with the light-absorbing film and functions as an etching mask when the light-absorbing film is patterned by dry etching. The first layer of the hard mask film is preferably made of a material that is resistant to dry etching using a fluorine-based gas (for example, sulfur hexafluoride gas (SF6), carbon tetrafluoride gas (CF4), etc.), specifically dry etching using a mixed gas of sulfur hexafluoride gas (SF6) and helium gas (He). Furthermore, the first layer of the hard mask film is preferably made of a material that can be removed by dry etching using a chlorine-based gas (chlorine-based dry etching), in particular dry etching using a mixed gas of chlorine gas (Cl2 gas) and oxygen gas (O2 gas) as the chlorine-based gas (dry etching using a chlorine-based gas containing oxygen (O)).

[0095] The material forming the first layer of the hard mask film is preferably a material containing either or both chromium (Cr) and ruthenium (Ru). The material forming the first layer of the hard mask film is preferably free from both silicon (Si) and tantalum (Ta). The material forming the first layer of the hard mask film may also contain one or more elements selected from oxygen (O), nitrogen (N), carbon (C), and boron (B). Specific examples of materials for the first layer of the hard mask film include chromium oxide (CrO), chromium nitride (CrN), chromium oxynitride (CrON), chromium carbide (CrC), chromium oxynitride (CrONC), ruthenium oxide (RuO), ruthenium nitride (RuN), and ruthenium oxynitride (RuON).

[0096] If the first layer of the hard mask film is too thin, it may lose its function as an etching mask in etching the light absorption film, and the sensitivity of defect inspection of the first layer of the hard mask film may decrease. Therefore, the thickness of the first layer of the hard mask film is preferably 2 nm or more, more preferably 4 nm or more. Also, when the first layer of the hard mask film is removed by dry etching, the protective film is usually exposed to dry etching at the same time. However, if the first layer of the hard mask film is too thick, a large amount of the protective film will be lost. Therefore, the thickness of the first layer of the hard mask film is preferably 14 nm or less, more preferably 10 nm or less.

[0097] Preferably, the hard mask film further includes a second layer that is in contact with the first layer of the hard mask film and functions as an etching mask when patterning the first layer of the hard mask film by dry etching. Preferably, the second layer of the hard mask film is made of a material that is resistant to dry etching using a chlorine-based gas (chlorine-based dry etching), and in particular to dry etching using a mixed gas of chlorine gas (Cl2 gas) and oxygen gas (O2 gas) as the chlorine-based gas (dry etching using a chlorine-based gas containing oxygen (O)). Furthermore, preferably, the second layer of the hard mask film is made of a material that can be removed by dry etching using a fluorine-based gas (for example, sulfur hexafluoride gas (SF6), carbon tetrafluoride gas (CF4), etc.), specifically, by dry etching using a mixed gas of sulfur hexafluoride gas (SF6) and helium gas (He).

[0098] The material forming the second layer of the hard mask film is preferably a material containing either or both silicon (Si) and tantalum (Ta). It is also preferable that the material forming the second layer of the hard mask film does not contain either chromium (Cr) or ruthenium (Ru). The material forming the second layer of the hard mask film may contain one or more elements selected from oxygen (O), nitrogen (N), carbon (C), and boron (B). Specific examples of materials for the second layer of the hard mask film include silicon nitride (SiN), silicon oxynitride (SiON), tantalum oxide (TaO), tantalum nitride (TaN), and tantalum oxynitride (TaON).

[0099] If the second layer of the hard mask film is too thin, it may lose its function as an etching mask in etching the first layer of the hard mask film, and the sensitivity of defect inspection of the second layer of the hard mask film may decrease. Therefore, the thickness of the second layer of the hard mask film is preferably 2 nm or more, more preferably 4 nm or more. In addition, a resist film is usually used to etch the second layer of the hard mask film, and the thinner the resist film, the more advantageous it is for miniaturizing the pattern to be formed. The thickness of the second layer of the hard mask film is preferably 14 nm or less, more preferably 10 nm or less, in order to make the resist film used in etching the second layer of the hard mask film thinner.

[0100] The conductive film is preferably formed in contact with the substrate. The conductive film preferably has a sheet resistance of 100 Ω / □ or less, and there are no particular restrictions on the material. Examples of materials for the conductive film include materials containing tantalum (Ta) or chromium (Cr). Furthermore, materials containing tantalum (Ta) or chromium (Cr) may also contain one or more elements selected from oxygen (O), nitrogen (N), carbon (C), and boron (B). The thickness of the conductive film is not particularly limited, as long as it functions for electrostatic chucks, but it is usually around 20 to 300 nm.

[0101] In the present invention, the resist film may be an electron beam resist drawn with an electron beam or a photoresist drawn with light, but a chemically amplified resist is preferred. The chemically amplified resist may be positive or negative, and examples include a base resin such as a hydroxystyrene resin or a (meth)acrylic acid resin, and an acid generator, with the addition of a crosslinking agent, quencher, surfactant, etc. as needed.

[0102] The thickness of the resist film is preferably 100 nm or less, more preferably 80 nm or less. However, from the viewpoint of making the resist pattern for forming a fine assist pattern during the development process for forming the resist pattern less susceptible to damage from the developer or the pure water during the rinsing process, it is even more preferably 60 nm or less. The lower limit of the resist film thickness is any thickness that functions as an etching mask in etching, that is, a thickness that leaves a resist pattern over the entire surface of the film to be etched after etching, and that can be formed with a stable thickness. Preferably, it is 30 nm or more, more preferably 40 nm or more.

[0103] The formation of the multilayer reflective film, protective film, light-absorbing film, hard mask film, and conductive film of the present invention is not particularly limited, but formation by sputtering is preferred because it offers good controllability and makes it easy to form films with predetermined properties. The sputtering method can be DC sputtering, RF sputtering, etc., and is not particularly limited.

[0104] When forming a multilayer reflective film consisting of a molybdenum (Mo) layer and a silicon (Si) layer, a molybdenum (Mo) target and a silicon (Si) target can be used as the sputtering target.

[0105] When forming a protective film (each layer constituting the protective film) with a material containing rhodium (Rh), a rhodium (Rh) target can be used as the sputtering target. When forming a protective film (each layer constituting the protective film) with a material containing niobium (Nb), a niobium (Nb) target can be used as the sputtering target. When forming a protective film (each layer constituting the protective film) with a material containing ruthenium (Ru), a ruthenium (Ru) target can be used as the sputtering target. In addition, if necessary, targets containing other elements that make up the protective film (each layer constituting the protective film) can be used.

[0106] When forming a light-absorbing film made from a material containing ruthenium (Ru), a ruthenium (Ru) target can be used as the sputtering target. When forming a light-absorbing film made from a material containing platinum (Pt), a platinum (Pt) target can be used as the sputtering target. When forming a light-absorbing film made from a material containing niobium (Nb), a niobium (Nb) target can be used as the sputtering target. If necessary, targets containing other elements that make up the light-absorbing film can be used.

[0107] When forming a layer made of a chromium (Cr)-containing material as the first layer of a hard mask film, a chromium (Cr) target can be used as the sputtering target. Similarly, when forming a layer made of a ruthenium (Ru)-containing material as the first layer of a hard mask film, a ruthenium (Ru) target can be used as the sputtering target.

[0108] On the other hand, when forming a second layer of the hard mask film made of a material containing silicon (Si), a silicon (Si) target can be used as the sputtering target. Also, when forming a second layer of the hard mask film made of a material containing tantalum (Ta), a tantalum (Ta) target can be used as the sputtering target.

[0109] When forming a conductive film with a material containing tantalum (Ta) or chromium (Cr), a tantalum (Ta) target or a chromium (Cr) target can be used as the sputtering target.

[0110] If the film and the layers constituting the film contain boron (B), then a target (such as a metal boride target) can be used in which boron (B) is added to the metal constituting the target as described above.

[0111] The power supplied to the sputtering target should be set appropriately depending on the size of the sputtering target, cooling efficiency, and ease of controlling film formation. Typically, the power per unit area of ​​the sputtering surface of the sputtering target is 50 to 3000 W / cm². 2 This is sufficient. Furthermore, noble gases such as helium (He), neon (Ne), and argon (Ar) are used as sputtering gases, and if the film and the layers constituting the film are to be formed using only the target element, then only noble gases should be used as sputtering gases.

[0112] When forming a film and its constituent layers with materials containing oxygen (O), nitrogen (N), or carbon (C), reactive sputtering is preferred. For reactive sputtering, noble gases such as helium (He), neon (Ne), and argon (Ar) are used as sputtering gases.

[0113] When forming a membrane and its constituent layers with materials containing oxygen (O), oxygen gas (O2 gas) may be used as the reactive gas. When forming a membrane and its constituent layers with materials containing nitrogen (N), nitrogen gas (N2 gas) may be used as the reactive gas. When forming a membrane and its constituent layers with materials containing both oxygen (O) and nitrogen (N), the reactive gas may be appropriately selected from oxygen gas (O2 gas), nitrogen gas (N2 gas), and nitrogen oxide gases such as nitric oxide (NO gas), nitrogen dioxide gas (NO2 gas), and nitrous oxide gas (N2O gas). When forming a membrane and its constituent layers with materials containing carbon, the reactive gas may be a carbon-containing gas such as methane gas (CH4), carbon monoxide gas (CO gas), or carbon dioxide gas (CO2 gas). When forming a film and its constituent layers from a material containing nitrogen (N), oxygen (O), and carbon (C), the reactive gases used can be, for example, oxygen gas (O2 gas), nitrogen gas (N2 gas), and carbon dioxide gas (CO2) used simultaneously.

[0114] The pressure during the formation of the membrane and its constituent layers should be set appropriately considering membrane stress, chemical resistance, and wash resistance, preferably 0.01 Pa or higher, more preferably 0.03 Pa or higher, and more preferably 1 Pa or lower, more preferably 0.3 Pa or lower, which particularly improves chemical resistance. The flow rates of each gas should be set appropriately to achieve the desired composition, and are usually between 0.1 and 100 sccm.

[0115] In the manufacturing process of a reflective photomask blank, the substrate or the substrate and the film formed on the substrate may be heat-treated before forming the resist film. The heat treatment method can include infrared heating, resistance heating, etc., and there are no particular restrictions on the treatment conditions. The heat treatment can be carried out, for example, in a gas atmosphere containing oxygen (O). There are no particular restrictions on the concentration of the oxygen (O) gas; for example, in the case of oxygen gas (O2 gas), it can be 1 to 100 volume percent. The heat treatment temperature is preferably 200°C or higher, more preferably 400°C or higher.

[0116] Furthermore, in the manufacturing process of reflective photomask blanks, the film formed on the substrate may be subjected to ozone treatment or plasma treatment before the resist film is formed, and there are no particular restrictions on the treatment conditions. Any of these treatments can be performed with the aim of increasing the oxygen (O) concentration on the surface of the film, and in that case, the treatment conditions should be adjusted as appropriate to achieve a predetermined oxygen (O) concentration. When forming the film by sputtering, it is also possible to increase the oxygen (O) concentration on the surface of the film by adjusting the ratio of the noble gas in the sputtering gas to oxygen-containing gases (oxidizing gases) such as oxygen gas (O2 gas), carbon monoxide gas (CO gas), and carbon dioxide gas (CO2 gas).

[0117] Furthermore, in the manufacturing process of reflective photomask blanks, a cleaning treatment may be performed to remove defects present on the surface of the substrate or the film formed on the substrate before forming the resist film. The cleaning can be performed using either or both ultrapure water and functional water, which is ultrapure water containing ozone gas (O3 gas), hydrogen gas (H2 gas), etc. Alternatively, after cleaning with ultrapure water containing a surfactant, further cleaning may be performed using either or both ultrapure water and functional water. The cleaning can be performed while irradiating with ultrasound as needed, and UV light irradiation may also be combined with the cleaning.

[0118] The method for forming the resist film (coating the resist) is not particularly limited, and known techniques such as spin coating can be applied.

[0119] A reflective photomask can be manufactured from the reflective photomask blank of the present invention, comprising a substrate, a multilayer reflective film, a protective film, and a pattern of light-absorbing films.

[0120] In the manufacturing of reflective photomasks, if a resist film is not formed on the reflective photomask blank, a resist film is formed in contact with the film furthest from the substrate on the reflective photomask blank, for example, the hard mask film, on the side furthest from the substrate. Subsequently, the resist pattern obtained by patterning the resist film is used as an etching mask, and the film in contact with the resist film is patterned by appropriately selecting the etching method to be applied according to the etching characteristics of the film. Furthermore, the film on the substrate side is patterned sequentially by appropriately selecting the etching method to be applied according to the etching characteristics of the film, thereby manufacturing a reflective photomask. In the manufacturing of reflective photomasks, the resist pattern can be removed with sulfuric acid peroxide (SPM).

[0121] The following are specific methods for manufacturing a reflective photomask from the reflective photomask blank of the present invention.

[0122] When manufacturing a reflective photomask from a reflective photomask blank (a reflective photomask blank of the first embodiment) having a first layer of hard mask film, [A1] A step of forming a resist film in contact with the side of the first layer of the hard mask film that is separated from the substrate, [B] A step of patterning the resist film to form a resist pattern, [C1] Using a resist pattern as an etching mask, the first layer of the hard mask film is patterned by dry etching using a chlorine-based gas to form the pattern of the first layer of the hard mask film. [D] A step to remove the resist pattern, [F1] A process to form a pattern on a light-absorbing film by dry etching using a fluorine-based gas, with the pattern of the first layer of the hard mask film used as an etching mask. [G1] A step to remove the pattern of the first layer of the hard mask film by dry etching using a chlorine-based gas. A reflective photomask can be manufactured by a method including (first aspect of the manufacturing method). If a reflective photomask blank comprising a resist film (third aspect of the reflective photomask blank) is used, step [A1] can be omitted.

[0123] Figure 6 is a cross-sectional view illustrating an example of a process for manufacturing a reflective photomask from a reflective photomask blank according to a first or third embodiment of the present invention. In the manufacturing method according to the first embodiment, for example, a reflective photomask can be manufactured by sequentially carrying out the following steps. In Figure 6, the protective film 3 is composed of multiple layers including layers A, B and C, as shown in Figures 1 to 5 (not shown).

[0124] First, [A1] if necessary, a resist film is formed in contact with the side of the hard mask film that is separated from the substrate of the first layer (Figure 6(A)). When using the reflective photomask blank 100 of the first embodiment, the resist film 6 is formed, and when using the reflective photomask blank 101 of the third embodiment which includes the resist film 6, it can be used as is.

[0125] Next, the [B] resist film 6 is patterned to form a resist pattern 6a (Figure 6(B)).

[0126] Next, using the [C1] resist pattern 6a as an etching mask, the first layer 51 of the hard mask film is patterned by dry etching using a chlorine-based gas to form the pattern 51a of the first layer of the hard mask film (Figure 6(C)).

[0127] Next, remove the resist pattern 6a (Figure 6(D)). Step [D] can be performed after step [C1] or step [F1].

[0128] Next, using the pattern 51a of the first layer of the [F1] hard mask film as an etching mask, the light-absorbing film 4 is patterned by dry etching using a fluorine-based gas to form the pattern 4a of the light-absorbing film (Figure 6(E)).

[0129] Next, the pattern 51a of the first layer of the [G1] hard mask film is removed by dry etching using a chlorine-based gas (Figure 6(F)) to obtain a reflective photomask 300.

[0130] In the dry etching process using a fluorine-based gas in step [F1], and the subsequent dry etching process using a chlorine-based gas in step [G1], it is preferable to carry out the process such that a protective film remains after the pattern of the first layer has been removed (after etching of the pattern of the first layer has been completed). In particular, it is preferable to carry out the process such that layer A of the protective film remains after the pattern of the first layer has been removed.

[0131] When manufacturing a reflective photomask from a reflective photomask blank (a reflective photomask blank of the second embodiment) comprising a first and second layer of hard mask film, [A2] A step of forming a resist film in contact with the side of the second layer of the hard mask film that is separated from the substrate, [B] A step of patterning the resist film to form a resist pattern, [C2] Using the resist pattern as an etching mask, the second layer of the hard mask film is patterned by dry etching using a fluorine-based gas to form the pattern of the second layer of the hard mask film. [D] A step to remove the resist pattern, [E2] A step of forming the pattern of the first layer of the hard mask film by dry etching using a chlorine-based gas, with the pattern of the second layer of the hard mask film used as an etching mask. [F2] Using the pattern of the first layer of the hard mask film as an etching mask, the light-absorbing film is patterned by fluorine-based dry etching to form a pattern on the light-absorbing film, while simultaneously removing the pattern of the second layer of the hard mask film. [G2] A step to remove the pattern of the first layer of the hard mask film by dry etching using a chlorine-based gas. A reflective photomask can be manufactured by a method including (second aspect of the manufacturing method). If a reflective photomask blank comprising a resist film (reflective photomask blank of the fourth aspect) is used, step [A2] can be omitted.

[0132] Figure 7 is a cross-sectional view illustrating an example of a process for manufacturing a reflective photomask from a reflective photomask blank according to a second or fourth embodiment of the present invention. In the manufacturing method according to the second embodiment, for example, a reflective photomask can be manufactured by sequentially carrying out the following steps. In Figure 7, the protective film 3 is composed of multiple layers including layers A, B and C, as shown in Figures 1 to 5 (not shown).

[0133] First, [A2] if necessary, a resist film is formed in contact with the side of the hard mask film that is separated from the substrate of the second layer (Figure 7(A)). When using the reflective photomask blank 200 of the second embodiment, the resist film 6 is formed, and when using the reflective photomask blank 201 of the fourth embodiment which includes the resist film 6, it can be used as is.

[0134] Next, the [B] resist film 6 is patterned to form a resist pattern 6a (Figure 7(B)).

[0135] Next, using the [C2] resist pattern 6a as an etching mask, the second layer 52 of the hard mask film is patterned by dry etching using a fluorine-based gas to form the pattern 52a of the second layer of the hard mask film (Figure 7(C)).

[0136] Next, remove the resist pattern 6a (Figure 7(D)). Step [D] can be performed after step [C2] or step [E2].

[0137] Next, using the pattern 52a of the second layer of the hard mask film [E2] as an etching mask, the first layer 51 of the hard mask film is patterned by dry etching using a chlorine-based gas to form the pattern 51a of the first layer of the hard mask film (Figure 7(E)).

[0138] Next, using the pattern 51a of the first layer of the [F2] hard mask film as an etching mask, the light-absorbing film 4 is patterned by dry etching using a fluorine-based gas to form the pattern 4a of the light-absorbing film and remove the pattern 52a of the second layer of the hard mask film (Figure 7(F)).

[0139] Next, the pattern 51a of the first layer of the [G2] hard mask film is removed by dry etching using a chlorine-based gas (Figure 7(G)) to obtain a reflective photomask 300.

[0140] In the [F2] step, dry etching using a fluorine-based gas, and the subsequent [G2] step, dry etching using a chlorine-based gas, it is preferable to carry out the process such that a protective film remains after the pattern of the first layer has been removed (after etching of the pattern of the first layer is completed). In particular, it is preferable to carry out the process such that layer A of the protective film remains after the pattern of the first layer has been removed.

[0141] Even if the resist film used to manufacture the reflective mask is thin, for example, if the thickness of the resist film is about 60 nm, an assist pattern with a line width of about 25 nm, particularly about 20 nm, can be formed well from the reflective mask blank of the present invention. [Examples]

[0142] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0143] [Example 1A] A reflective photomask blank was manufactured by sequentially laminating a multilayer reflective film, protective films (layers C, B, and A), a light-absorbing film, and hard mask films (layers 1 and 2) on a quartz substrate measuring 152 mm square and approximately 6 mm thick.

[0144] First, using a molybdenum (Mo) target and a silicon (Si) target, and argon gas (Ar) as the sputtering gas, the applied power to the target and the flow rate of the sputtering gas were adjusted, and sputtering with the molybdenum (Mo) target and sputtering with the silicon (Si) target were performed alternately to form a multilayer reflective film (280 nm thick) on a quartz substrate, in which molybdenum (Mo) layers and silicon (Si) layers were alternately stacked (reflectivity of 65% for light with a wavelength of 13.5 nm). The stacking of the molybdenum (Mo) layer and the silicon (Si) layer was performed for 40 cycles (40 layers each of molybdenum (Mo) and silicon (Si) layers).

[0145] Next, a ruthenium (Ru) target was used as the target, and argon gas (Ar gas) was used as the sputtering gas. By adjusting the power applied to the target and the flow rate of the sputtering gas, sputtering was performed using the ruthenium (Ru) target to form a layer made of ruthenium (Ru) as the protective C layer on top of the multilayer reflective film.

[0146] Next, using a niobium (Nb) target and a ruthenium (Ru) target as targets, and argon gas (Ar gas) as the sputtering gas, sputtering was performed using the niobium (Nb) and ruthenium (Ru) targets by adjusting the power applied to the targets and the flow rate of the sputtering gas, thereby forming a layer made of niobium (NbRu) as the B layer of the protective film on top of the C layer of the protective film.

[0147] Next, a rhodium (Rh) target was used as the target, and argon gas (Ar gas) was used as the sputtering gas. By adjusting the power applied to the target and the flow rate of the sputtering gas, sputtering was performed using the rhodium (Rh) target to form a layer made of rhodium (Rh) as the protective film A layer on top of the protective film B layer. This resulted in a protective film consisting of three layers, A, B, and C, from the side away from the substrate.

[0148] Table 1 shows the composition and thickness of each layer (layers A, B, and C) of the protective film, the overall thickness of the protective film, and the combined reflectance of the multilayer reflective film and protective film for light at a wavelength of 13.5 nm. The composition was analyzed using an X-ray photoelectron spectroscopy analyzer (the same method was used for the composition analysis below). The thickness was measured using an X-ray diffractometer (the same method was used for the thickness measurement below). The reflectance was measured using a reflectometer for light at an incident angle of 6 degrees (the same method was used for the reflectance measurement below).

[0149] Next, using a ruthenium (Ru) target and a platinum (Pt) target as targets, and argon gas (Ar gas) as the sputtering gas, sputtering was performed by adjusting the power applied to the targets and the flow rate of the sputtering gas to form a light-absorbing film made of ruthenium-platinum (RuPt) on the protective film.

[0150] The light-absorbing film had a composition of 52 atomic percent ruthenium (Ru) and 48 atomic percent platinum (Pt), with a thickness of 36 nm. Its reflectance for light at a wavelength of 13.5 nm (relative reflectance to the multilayer reflective and protective films was 4.9%) and its phase difference for light at a wavelength of 13.5 nm (relative phase difference to the multilayer reflective and protective films) was 211 degrees. The phase difference was calculated by measuring the refractive index and extinction coefficient using a refractive index / extinction coefficient meter (the same method was used for the following phase difference calculations).

[0151] Next, a chromium (Cr) target was used as the target, and argon (Ar) gas, oxygen (O2) gas, nitrogen (N2) gas, and carbon dioxide (CO2) gas were used as sputtering gases. By adjusting the power applied to the target and the flow rate of the sputtering gases, sputtering was performed to form the first layer of a hard mask film made of chromium nitrile carbide (CrONC) on the light-absorbing film.

[0152] Next, a silicon (Si) target was used as the target, and argon (Ar) gas, oxygen (O2) gas, and nitrogen (N2) gas were used as sputtering gases. By adjusting the power applied to the target and the flow rate of the sputtering gases, sputtering was performed to form a second hard mask film made of silicon oxynitride (SiON) on top of the first hard mask film, thereby obtaining a reflective photomask blank. The composition and thickness of the first and second hard mask films are shown in Table 2.

[0153] [Examples 2A-15A, Comparative Examples 1A-8A] The multilayer reflective film was formed in the same manner as in Example 1A. The protective film was formed in the same manner as in Example 1A, with the applied power to the target, the flow rate of the sputtering gas, and the sputtering time kept the same or modified. The light-absorbing film was formed in the same manner as in Example 1A. Furthermore, reflective photomask blanks were obtained by forming only the first layer of the hard mask film (Example 15A) or both the first and second layers (Examples 2A to 14A, Comparative Examples 1A to 8A) in the same manner as in Example 1A, with the applied power to the target, the flow rate of the sputtering gas, and the sputtering time kept the same or modified.

[0154] In Example 2A, a niobium (Nb) target and a ruthenium (Ru) target were used as the B layer of the protective film, and argon gas (Ar gas) and oxygen gas (O2 gas) were used as the sputtering gas. By adjusting the power applied to the target and the flow rate of the sputtering gas, sputtering was performed using the niobium (Nb) target and the ruthenium (Ru) target to form a layer made of niobium oxide (NbRuO). Except for the B layer of the protective film, the procedure was the same as in Example 1A.

[0155] In Example 3A, a niobium (Nb) target was used as the B layer of the protective film, and argon gas (Ar gas) and oxygen gas (O2 gas) were used as sputtering gases. By adjusting the power applied to the target and the flow rate of the sputtering gas, sputtering was performed using the niobium (Nb) target to form a layer made of niobium oxide (NbO). Except for the B layer of the protective film, the procedure was the same as in Example 1A.

[0156] In Example 4A, a layer made of niobium oxide (NbO) was formed as the B layer of the protective film in the same manner as in Example 3A. Furthermore, for the A layer of the protective film, a rhodium (Rh) target and a ruthenium (Ru) target were used as targets, and argon gas (Ar gas) was used as the sputtering gas. By adjusting the power applied to the targets and the flow rate of the sputtering gas, sputtering was performed using the rhodium (Rh) and ruthenium (Ru) targets to form a layer made of rhodium-ruthenium (RhRu). Except for the B and A layers of the protective film, the procedure was the same as in Example 1A.

[0157] In Example 5A, a rhodium (Rh) target, a niobium (Nb) target, and a ruthenium (Ru) target were used as the A layer of the protective film, and argon gas (Ar gas) was used as the sputtering gas. By adjusting the power applied to the targets and the flow rate of the sputtering gas, sputtering was performed using the rhodium (Rh) target, niobium (Nb) target, and ruthenium (Ru) target to form a layer made of rhodium niobium (RhNbRu). Except for the A layer of the protective film, the procedure was the same as in Example 1A.

[0158] In Example 7A, a rhodium (Rh) target and a ruthenium (Ru) target were used as the A layer of the protective film, and argon gas (Ar gas) was used as the sputtering gas. By adjusting the power applied to the targets and the flow rate of the sputtering gas, sputtering was performed using the rhodium (Rh) target and the ruthenium (Ru) target to form a layer made of rhodium-ruthenium (RhRu). Except for the A layer of the protective film, the procedure was the same as in Example 1A.

[0159] In Example 8A, a protective film consisting of five layers was formed. First, a layer made of ruthenium (Ru) was formed as layer C on the multilayer reflective film in the same manner as in Example 1A. Next, a layer made of niobrthenium (NbRu) was formed as layer B on layer C in the same manner as in Example 1A. Next, a layer made of ruthenium (Ru) was formed as layer C on layer B in the same manner as in Example 1A. Next, a layer made of niobrthenium (NbRu) was formed as layer B on layer C in the same manner as in Example 1A. Next, a layer made of rhodium (Rh) was formed as layer A on layer B in the same manner as in Example 1A, resulting in a protective film consisting of five layers: layer A, layer B, layer C, layer B, and layer C, from the side away from the substrate. Except for the protective film, the procedure was the same as in Example 1A.

[0160] In Example 9A, a protective film consisting of five layers was formed. First, a layer made of ruthenium (Ru) was formed as layer C on the multilayer reflective film in the same manner as in Example 1A. Next, a layer made of niobruthenium (NbRu) was formed as layer B on layer C in the same manner as in Example 1A. Next, a layer made of ruthenium (Ru) was formed as layer C on layer B in the same manner as in Example 1A. Next, a layer made of niobruthenium (NbRu) was formed as layer B on layer C in the same manner as in Example 1A. Next, a layer made of rhodium ruthenium (RhRu) was formed as layer A on layer B in the same manner as in Example 7A, resulting in a protective film consisting of five layers: layer A, layer B, layer C, layer B, and layer C, from the side away from the substrate. Except for the protective film, the procedure was the same as in Example 1A.

[0161] In Example 10A, a protective film consisting of five layers was formed. First, a layer made of ruthenium (Ru) was formed as layer C on the multilayer reflective film in the same manner as in Example 1A. Next, a layer made of niobruthenium (NbRu) was formed as layer B on layer C in the same manner as in Example 1A. Next, a layer made of ruthenium (Ru) was formed as layer C on layer B in the same manner as in Example 1A. Next, a layer made of niobium oxide (NbO) was formed as layer B on layer C in the same manner as in Example 3A. Next, a layer made of rhodium ruthenium (RhRu) was formed as layer A on layer B in the same manner as in Example 7A, resulting in a protective film consisting of five layers: layer A, layer B, layer C, layer B, and layer C, from the side away from the substrate. Except for the protective film, the procedure was the same as in Example 1A.

[0162] In Example 11A, a protective film consisting of five layers was formed. First, a layer made of ruthenium (Ru) was formed as the C layer on the multilayer reflective film in the same manner as in Example 1A. Next, a layer made of niobium oxide (NbO) was formed as the B layer on top of the C layer in the same manner as in Example 3A. Next, a layer made of ruthenium (Ru) was formed as the C layer on top of the B layer in the same manner as in Example 1A. Next, a layer made of niobium oxide (NbO) was formed as the B layer on top of the C layer in the same manner as in Example 3A. Next, a layer made of rhodium ruthenium (RhRu) was formed as the A layer on top of the B layer in the same manner as in Example 7A, resulting in a protective film consisting of five layers: A layer, B layer, C layer, B layer, and C layer, from the side away from the substrate. Except for the protective film, the procedure was the same as in Example 1A.

[0163] In Example 12A, a ruthenium (Ru) target was used as the first layer of the hard mask film, and argon (Ar) gas, oxygen (O2) gas, and nitrogen (N2) gas were used as sputtering gases. By adjusting the power applied to the target and the flow rate of the sputtering gases, sputtering was performed to form a layer made of ruthenium oxynitride (RuON). Except for the first layer of the hard mask film, the procedure was the same as in Example 1A.

[0164] In Example 13A, a tantalum (Ta) target was used as the second layer of the hard mask film, and argon (Ar) gas, oxygen (O2) gas, and nitrogen (N2) gas were used as sputtering gases. By adjusting the power applied to the target and the flow rate of the sputtering gases, sputtering was performed to form a layer made of tantalum oxynitride (TaON). ​​Except for the second layer of the hard mask film, the procedure was the same as in Example 1A.

[0165] In Example 14A, the first layer of the hard mask film was formed from ruthenium oxynitride (RuON) in the same manner as in Example 12A. The second layer of the hard mask film was formed from tantalum oxynitride (TaON) in the same manner as in Example 13A. Except for the first and second layers of the hard mask film, the procedure was the same as in Example 1A.

[0166] In Example 15A, the second layer of the hard mask film was not formed. Except for the second layer of the hard mask film, the procedure was the same as in Example 1A.

[0167] In Comparative Example 1A, the protective film B layer was not formed. Except for the protective film B layer, the procedure was the same as in Example 1A.

[0168] In Comparative Example 2A, the protective B layer was not formed. Except for the protective B layer, the procedure was the same as in Example 4A.

[0169] In Comparative Example 3A, the protective film's B layer was not formed. Except for the protective film's B layer, the procedure was the same as in Example 5A.

[0170] In Comparative Example 4A, the protective film's C layer was not formed. Except for the protective film's C layer, the procedure was the same as in Example 1A.

[0171] In Comparative Example 5A, layers B and C of the protective film were not formed. Except for layers B and C of the protective film, the procedure was the same as in Example 1A.

[0172] In Comparative Example 6A, layers B and C of the protective film were not formed. Except for layers B and C of the protective film, the procedure was the same as in Example 4A.

[0173] In Comparative Example 7A, layers B and C of the protective film were not formed. Except for layers B and C of the protective film, the procedure was the same as in Example 5A.

[0174] In Comparative Example 8A, the order in which layers B and C of the protective film were formed was reversed. Except for layers B and C of the protective film, the procedure was the same as in Example 1A.

[0175] Table 1 shows the composition and thickness of each layer (layers A, B, and C) of the protective film, the overall thickness of the protective film, and the combined reflectance of the multilayer reflective film and protective film for light at a wavelength of 13.5 nm. Table 2 shows the composition and thickness of the first and second layers of the hard mask film.

[0176] [Table 1]

[0177] [Table 2]

[0178] [Examples 1B-14B, Comparative Examples 1B-8B] Reflective photomasks were manufactured from the reflective photomask blanks of Examples 1A to 14A and Comparative Examples 1A to 8A. First, a 60 nm thick resist film was formed by spin-coating a positive-type chemically amplified electron beam resist onto the second layer of the hard mask film of the reflective photomask blank.

[0179] Next, using an electron beam lithography apparatus, a dose of 100 μC / cm² was used. 2 Next, a line and space pattern (100,000 lines with a long side dimension of 1000 nm and a short side dimension of 100 nm (line pattern width:space pattern width = 1:1)) was drawn. Then, a heat treatment (PEB: Post Exposure Bake) was performed at 110°C for 14 minutes using a heat treatment device. Next, a development process was performed using paddle development for 40 seconds to form a resist pattern.

[0180] Next, using the obtained resist pattern as an etching mask, dry etching with a fluorine-based gas was performed on the second layer of the hard mask film, with the etching time being the etching clear time plus 15% over-etching, under the following conditions (Condition 1) to form the pattern of the second layer of the hard mask film.

[0181] <Conditions for dry etching using fluorine-based gas (Condition 1)> Equipment: ICP (Inductively Coupled Plasma) system Gas: SF6 gas + He gas Gas pressure: 4.0 mTorr (0.53 Pa) ICP power: 400W

[0182] Next, the remaining resist pattern was removed by washing with sulfuric acid peroxide (a mixture of sulfuric acid and hydrogen peroxide (sulfuric acid:hydrogen peroxide = 3:1 (volume ratio)), the same applies hereafter).

[0183] Next, using the pattern of the second layer of the obtained hard mask film as an etching mask, dry etching using a chlorine-based gas was performed on the first layer of the hard mask film. The etching time was defined as the etching clear time plus 300% over-etching, and the etching was carried out under the following conditions (Condition 2) to form the pattern of the first layer of the hard mask film.

[0184] <Conditions for dry etching using chlorine-based gas (Condition 2)> Equipment: ICP (Inductively Coupled Plasma) system Gas: Cl2 gas + O2 gas Gas pressure: 3.0 mTorr (0.40 Pa) ICP power: 350W

[0185] Next, using the pattern of the first layer of the obtained hard mask film as an etching mask, dry etching with a fluorine-based gas was performed on the light-absorbing film under the conditions of dry etching with a fluorine-based gas (Condition 1), with the etching time being the etching clear time plus 15% over-etching. This formed the pattern of the light-absorbing film and removed the pattern of the second layer of the hard mask film.

[0186] Next, dry etching using a chlorine-based gas was performed on the pattern of the first layer of the hard mask film, with the etching time defined as the etching clear time plus 100% over-etching, under the above conditions (Condition 2). This removed the pattern of the first layer of the hard mask film, obtaining a reflective photomask.

[0187] [Example 15B] A reflective photomask was manufactured from the reflective photomask blank of Example 15A. First, a 60 nm thick resist film was formed by spin-coating a positive chemically amplified electron beam resist onto the first layer of the hard mask film of the reflective photomask blank.

[0188] Next, a line-and-space pattern was formed in the same manner as in Example 1B, followed by heat treatment and development to form a resist pattern.

[0189] Next, using the obtained resist pattern as an etching mask, dry etching with a chlorine-based gas was performed on the first layer of the hard mask film. The etching time was defined as the etching clear time plus 300% over-etching, and the dry etching was carried out under the conditions for dry etching with a chlorine-based gas (condition 2) described above, to form the pattern of the first layer of the hard mask film.

[0190] Next, the remaining resist pattern was removed by washing with sulfuric acid peroxide.

[0191] Next, using the pattern of the first layer of the obtained hard mask film as an etching mask, dry etching with a fluorine-based gas was performed on the light-absorbing film, with the etching time being the etching clear time plus 15% over-etching, under the dry etching conditions (Condition 1) described above, to form the pattern of the light-absorbing film.

[0192] Next, dry etching using a chlorine-based gas was performed on the pattern of the first layer of the hard mask film, with the etching time defined as the etching clear time plus 100% over-etching, under the conditions for dry etching using a chlorine-based gas (condition 2) described above. This removed the pattern of the first layer of the hard mask film and obtained a reflective photomask.

[0193] [Amount of protective film lost during the manufacturing of reflective photomasks] The protective film is subjected to overetching during dry etching using a fluorine-based gas when patterning the light-absorbing film, and to dry etching (including overetching) using a chlorine-based gas when removing the pattern of the first layer of the hard mask film. The total thickness (residual amount) of the protective film of the resulting reflective photomask was measured. The results are shown in Table 3.

[0194] [Evaluation of the resistance of reflective photomasks to blister defects] Using a hydrogen plasma generator, a reflective photomask obtained under the following conditions (Condition 3) was irradiated with hydrogen plasma containing hydrogen ions for a predetermined time. Afterward, the presence or absence of blister defects was evaluated using a photomask visual inspection device. The results are shown in Table 3. Irradiation times were evaluated in four stages: 1 hour, 2 hours, 4 hours, and 8 hours. The evaluation was terminated when defects were detected.

[0195] <Irradiation conditions for hydrogen plasma (Condition 3)> Equipment: Plasma CVD (plasma-enhanced Chemical Vaper Deposition) equipment Chamber pressure (when hydrogen gas (H2 gas) is introduced): 1 Torr (133 Pa) Hydrogen ion flow rate: 2 × 10 20 H·ions / m 2 s Plasma source power: 100W

[0196] [Table 3]

[0197] It should be noted that the present invention is not limited to the embodiments described above. The embodiments described above are merely examples, and any configuration that is identical or substantially identical to the technical concept of the present invention and that produces the same or similar effects is included within the technical scope of the present invention. [Explanation of symbols]

[0198] 1 circuit board 2 Multilayer reflective film 3 Protective film 31. Layer A of the protective film 32. Protective film layer B 33. Protective film C layer 4. Light-absorbing film 4a Pattern of light-absorbing film 5. Hard mask film 51. First layer of hard mask film 51a Pattern of the first layer of the hard mask film 52. Second layer of hard mask film 52a Pattern of the second layer of the hard mask film 6. Resist film 6a Resist Pattern 100, 101, 200, 201 Reflective Photomask Blanks 300 Reflective Photomasks

Claims

1. circuit board and A multilayer reflective film formed on the substrate that reflects exposure light, which is light in the extreme ultraviolet region, A protective film is formed on the multilayer reflective film in contact with the multilayer reflective film to protect the multilayer reflective film, A pattern of a light-absorbing film formed on the protective film in contact with the protective film and absorbing the exposure light and Equipped with, The protective film is composed of a multilayer including one A layer, one or more B layers, and one or more C layers. The A layer of the protective film contains rhodium (Rh) and has a thickness of 0.5 nm or more and 2 nm or less. The B layer of the protective film contains niobium (Nb) but does not contain rhodium (Rh), the niobium (Nb) content is 10 atomic percent or more, and the thickness is 0.5 nm or more and 2 nm or less. The C layer of the protective film contains ruthenium (Ru), does not contain rhodium (Rh) or niobium (Nb), and has a thickness of 0.5 nm or more and 2 nm or less. The A layer of the protective film is in contact with the pattern of the light-absorbing film. One of the C layers of the protective film is in contact with the multilayer reflective film. A reflective photomask characterized by the following features.

2. The reflective photomask according to claim 1, characterized in that the protective film is composed of a multilayer consisting of the A layer, the B layer, and the C layer.

3. The reflective photomask according to claim 2, characterized in that the protective film is composed of a multilayer structure consisting of three layers, the A layer, the B layer, and the C layer, from the side away from the substrate, or a multilayer structure consisting of five layers, the A layer, the B layer, the C layer, the B layer, and the C layer, from the side away from the substrate.

4. The light-absorbing film is composed of a single layer or a multilayer, and each layer of the single layer or multilayer contains ruthenium (Ru) and platinum (Pt), with a ruthenium (Ru) content of 30 atomic% to 70 atomic%, a platinum (Pt) content of 30 atomic% to 70 atomic%, and a total content of ruthenium (Ru) and platinum (Pt) of 96 atomic% or more. The thickness of the light-absorbing film is 32 nm or more and 38 nm or less. The reflectance of the light-absorbing film to the exposure light is 1% or more and 8% or less, and the phase difference with respect to the exposure light is 190 degrees or more and 240 degrees or less. The reflective photomask according to feature 1.

5. circuit board and A multilayer reflective film formed on the substrate that reflects exposure light, which is light in the extreme ultraviolet region, A protective film is formed on the multilayer reflective film in contact with the multilayer reflective film to protect the multilayer reflective film, A light-absorbing film is formed on the protective film in contact with the protective film and absorbs the exposure light, A hard mask film formed on the light-absorbing film in contact with the light-absorbing film, Equipped with, The protective film is composed of a multilayer including one A layer, one or more B layers, and one or more C layers. The A layer of the protective film contains rhodium (Rh) and has a thickness of 0.5 nm or more and 2 nm or less. The B layer of the protective film contains niobium (Nb) but does not contain rhodium (Rh), the niobium (Nb) content is 10 atomic percent or more, and the thickness is 0.5 nm or more and 2 nm or less. The C layer of the protective film contains ruthenium (Ru), does not contain rhodium (Rh) or niobium (Nb), and has a thickness of 0.5 nm or more and 2 nm or less. The A layer of the protective film is in contact with the light-absorbing film. One of the C layers of the protective film is in contact with the multilayer reflective film. A reflective photomask blank characterized by the following features.

6. The reflective photomask blank according to claim 5, characterized in that the protective film is composed of a multilayer consisting of the A layer, the B layer and the C layer.

7. The reflective photomask blank according to claim 6, characterized in that the protective film is composed of a multilayer consisting of three layers, the A layer, the B layer, and the C layer, from the side away from the substrate, or a multilayer consisting of five layers, the A layer, the B layer, the C layer, the B layer, and the C layer, from the side away from the substrate.

8. The light-absorbing film is composed of a single layer or a multilayer, and each layer of the single layer or multilayer contains ruthenium (Ru) and platinum (Pt), with a ruthenium (Ru) content of 30 atomic% to 70 atomic%, a platinum (Pt) content of 30 atomic% to 70 atomic%, and a total content of ruthenium (Ru) and platinum (Pt) of 96 atomic% or more. The thickness of the light-absorbing film is 32 nm or more and 38 nm or less. The reflectance of the light-absorbing film to the exposure light is 1% or more and 8% or less, and the phase difference with respect to the exposure light is 190 degrees or more and 240 degrees or less. The reflective photomask blank according to feature 5.

9. The reflective photomask blank according to claim 5, wherein the hard mask film includes a first layer that is in contact with the light absorption film and functions as an etching mask when the light absorption film is patterned by dry etching, and the first layer of the hard mask film is made of a material that is resistant to dry etching using a fluorine-based gas and can be removed by dry etching using a chlorine-based gas.

10. The reflective photomask blank according to claim 9, wherein the hard mask film includes a second layer that is in contact with the first layer of the hard mask film and functions as an etching mask when the first layer of the hard mask film is patterned by dry etching, and the second layer of the hard mask film is made of a material that is resistant to dry etching using a chlorine-based gas and can be removed by dry etching using a fluorine-based gas.

11. A method for manufacturing a reflective photomask according to claim 1 from a reflective photomask blank according to claim 9, [A1] A step of forming a resist film in contact with the side of the first layer of the hard mask film that is separated from the substrate, [B] A step of patterning the resist film to form a resist pattern, [C1] Using the resist pattern as an etching mask, the first layer of the hard mask film is patterned by dry etching using a chlorine-based gas to form a pattern on the first layer of the hard mask film. [D] A step of removing the resist pattern, [F1] A step of forming a pattern in the light-absorbing film by dry etching using a fluorine-based gas, with the pattern of the first layer of the hard mask film as an etching mask. [G1] A step of removing the pattern of the first layer of the hard mask film by dry etching using a chlorine-based gas. A method for manufacturing a reflective photomask, characterized by including the following:

12. A method for manufacturing a reflective photomask according to claim 1 from a reflective photomask blank according to claim 10, [A2] A step of forming a resist film in contact with the side of the second layer of the hard mask film that is separated from the substrate, [B] A step of patterning the resist film to form a resist pattern, [C2] Using the resist pattern as an etching mask, the second layer of the hard mask film is patterned by dry etching using a fluorine-based gas to form a pattern on the second layer of the hard mask film. [D] A step of removing the resist pattern, [E2] A step of forming the pattern of the first layer of the hard mask film by dry etching using a chlorine-based gas, using the pattern of the second layer of the hard mask film as an etching mask, [F2] Using the pattern of the first layer of the hard mask film as an etching mask, the light-absorbing film is patterned by dry etching using a fluorine-based gas to form the pattern of the light-absorbing film, and the pattern of the second layer of the hard mask film is removed. [G2] A step of removing the pattern of the first layer of the hard mask film by dry etching using a chlorine-based gas. A method for manufacturing a reflective photomask, characterized by including the following:

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