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

Abstract

A reflective photomask is formed from a material comprising a substrate, a multilayer reflective film that reflects exposure light in the extreme ultraviolet region, a protective film with an extinction coefficient of 0.018 to 0.035 and a thickness of 1 to 6 nm, and a pattern of a light-absorbing film with a reflectivity of 1 to 8% to exposure light, a phase shift function with a phase difference of 190 to 240 degrees, absorbs exposure light, and has a thickness of 32 to 38 nm, wherein the light-absorbing film contains 30 to 70 atomic percent of Ru and 30 to 70 atomic percent of Pt, and the total of Ru and Pt is 96 atomic percent or more. [Effects] This provides 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%, is entirely removable by etching with a fluorine-based gas, allows for easy pattern modification, and has minimal shadowing effect.

Description

[Technical Field]

[0001] This 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 a reflective photomask in the manufacture of a reflective photomask, and a method for manufacturing a reflective photomask from a reflective photomask blank. [Background technology]

[0002] With the miniaturization of semiconductor devices, and especially with the high integration of large-scale integrated circuits, high pattern resolution is required for projection lithography. Therefore, phase-shift photomasks (phase-shift masks) have been developed as a method to improve the resolution of transfer patterns in photomasks. The principle of the phase-shift method is to adjust the phase of transmitted light passing through the aperture of the phase-shift film in the photomask so that it is inverted by approximately 180 degrees relative to the phase of transmitted light passing through the adjacent portion of the phase-shift film. This causes interference of transmitted light at the boundary between the aperture and the adjacent portion, reducing light intensity. As a result, the resolution and depth of field of the transfer pattern are improved. Photomasks using this principle are generally called phase-shift photomasks. In this case, the phase-shift photomask is a type of transmission 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] As a method of manufacturing a reflective photomask by patterning a light absorption film from a reflective photomask blank in which a reflective film that reflects light in the extreme ultraviolet region, a protective film for protecting the reflective film, and a light absorption film that absorbs light in the extreme ultraviolet region are formed in this order, specifically, the following method is common. 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

Summary of the Invention

Problems to be Solved by the Invention

[0022] In EUV lithography, after the logic 3nm generation and later, a reflective photomask (reflective phase shift photomask) having a pattern of a light absorption film with a phase shift function is used to form finer patterns on a wafer. By using a reflective phase shift photomask, higher wafer transfer characteristics can be obtained than with 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, and NILS is given 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 giving W, and dI / dx is the gradient of the aerial image.) This can be determined by [the formula used]. When the NILS value is large, the optical image becomes steeper, improving the dimensional controllability of the resist pattern on the wafer. Therefore, a large NILS value is effective in forming finer patterns on the wafer, and a reflective phase-shift photomask, which can achieve a larger NILS value than a binary reflective photomask, is used.

[0023] Furthermore, in EUV lithography using a reflective phase-shift photomask, when the line and space size (pitch) of a line and space pattern on a wafer is 10-20 nm, the optimal focus value differs depending on the line and space size (pitch). When a single device circuit pattern contains line and space patterns with different sizes (pitches), in order to form a good device circuit pattern for all line and space patterns, if the reflectivity of the light-absorbing film with phase-shift function to exposure light is about 5%, the difference in the optimal focus value of line and space patterns with different sizes (pitches) will be reduced, and a device circuit pattern with a good line and space pattern can be formed.

[0024] A light-absorbing film needs to have a certain thickness or more to absorb some of the exposure light and achieve a predetermined reflectivity. However, in a reflective photomask, the exposure light is incident on the reflective photomask at an oblique angle and reflected at an oblique angle. If the light-absorbing film is thick, the shadowing effect, where the exposure light is blocked by the film when it is incident and when it is reflected, becomes greater. Therefore, to minimize the shadowing effect, a thinner light-absorbing film that achieves the predetermined reflectivity is advantageous.

[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] The present invention was made to solve the above problems, and its first objective is 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. The second objective of the present invention is to provide a reflective photomask blank for manufacturing a reflective photomask, in which the resist film used for pattern formation of the light-absorbing film can be made thinner, and the resolution limit in pattern formation of the light-absorbing film is improved. Furthermore, the third 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]

[0037] To solve the above problems, the present inventors conducted extensive research on reflective photomask blanks and light-absorbing films having a phase-shift function for reflective photomasks. As a result, they found that the above problems can be solved by a single-layer or multi-layer light-absorbing film made of a material containing ruthenium (Ru) and platinum (Pt), with a ruthenium (Ru) content of 30 to 70 atomic percent, a platinum (Pt) content of 30 to 70 atomic percent, and a total ruthenium (Ru) and platinum (Pt) content of 96 atomic percent or more, having a thickness of 32 nm to 38 nm, a reflectance to exposure light of 1% to 8%, and a phase difference to exposure light of 190 degrees to 240 degrees. Furthermore, as a result of extensive research on reflective photomask blanks for manufacturing reflective photomasks, they found that the above problems can be solved by a reflective photomask blank equipped with a hard mask film formed in contact with the light-absorbing film, leading to the present invention.

[0038] 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 formed on the multilayer reflective film for protecting the multilayer reflective film, A pattern of a light-absorbing film formed on the protective film in contact with the protective film, which absorbs the exposure light and has a phase-shift function, and Equipped with, The extinction coefficient of the protective film is 0.018 or more and 0.035 or less, and the thickness of the protective film is 1 nm or more and 6 nm or less. 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 characterized by the following features. 2. The reflective photomask according to claim 1, characterized in that the light-absorbing film further contains niobium (Nb), and the niobium (Nb) content is 4 atomic percent or less. 3. The reflective photomask according to claim 1, characterized in that the material forming the light-absorbing film is resistant to dry etching using a chlorine-based gas and can be removed by dry etching using a fluorine-based gas. 4. The reflective photomask according to claim 1, characterized in that when the protective film and the light-absorbing film are etched under the same conditions by dry etching, in which a fluorine-based gas is activated with an electron beam, the ratio of the etching rate of the light-absorbing film to the etching rate of the protective film is 50 or more. 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 formed on the multilayer reflective film for protecting the multilayer reflective film, A light-absorbing film is formed on the protective film in contact with the protective film, which absorbs the exposure light and has a phase-shift function. A hard mask film formed on the light-absorbing film in contact with the light-absorbing film, Equipped with, The extinction coefficient of the protective film is 0.018 or more and 0.035 or less, and the thickness of the protective film is 1 nm or more and 6 nm or less. 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 characterized by the following features. 6. The reflective photomask blank according to claim 5, characterized in that the light-absorbing film further contains niobium (Nb), and the niobium (Nb) content is 4 atomic percent or less. 7. The reflective photomask blank according to claim 5, characterized in that the material forming the light-absorbing film is resistant to dry etching using a chlorine-based gas and can be removed by dry etching using a fluorine-based gas. 8. The reflective photomask blank according to claim 5, characterized in that when the protective film and the light-absorbing film are etched under the same conditions by dry etching, in which a fluorine-based gas is activated with an electron beam, the ratio of the etching rate of the light-absorbing film to the etching rate of the protective film is 50 or more. 9. The reflective photomask blank according to 5, characterized in that when the protective film and the light-absorbing film are etched under the same conditions by dry etching using plasma etching with a fluorine-based gas, the ratio of the etching rate of the light-absorbing film to the etching rate of the protective film is 4 or more. 10. 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. 11. The reflective photomask blank according to 10, characterized in that the first layer of the hard mask film contains either or both chromium (Cr) and ruthenium (Ru), does not contain silicon (Si) and tantalum (Ta), and has a thickness of 2 nm or more and 14 nm or less. 12. The reflective photomask blank according to 10, characterized in that 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. 13. The reflective photomask blank according to 12, characterized in that the second layer of the hard mask film contains either or both silicon (Si) and tantalum (Ta), does not contain chromium (Cr) and ruthenium (Ru), and has a thickness of 2 nm or more and 14 nm or less. A method for manufacturing a reflective photomask as described in 1 from a reflective photomask blank as described in 14.10 or 11, [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 15.12 or 13, [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]

[0039] According to the present invention, 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. Furthermore, according to the present invention, it is possible to thin the resist film used for pattern formation of the light-absorbing film, and to provide a reflective photomask blank with an improved resolution limit in pattern formation of the light-absorbing film. [Brief explanation of the drawing]

[0040] [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]

[0041] 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 blank of the present invention 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 hard mask film preferably includes a first layer that functions as an etching mask when the light-absorbing film is patterned by dry etching. The hard mask film more preferably further includes a second layer that functions as an etching mask when the first layer of the hard mask film is patterned by dry etching.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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 hard mask film 5 consists only of a first layer 51.

[0046] 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 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 52 formed in contact with the first layer 51.

[0047] 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.

[0048] 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.

[0049] 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 pattern 4a of a light-absorbing film formed on the protective film 3 in contact with the protective film 3.

[0050] 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.

[0051] 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.

[0052] 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)).

[0053] 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.

[0054] 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.

[0055] 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 light absorption film pattern. Furthermore, it is preferable that the protective film has the function of protecting the multilayer reflective film when patterning the light absorption film by etching, and preventing oxidation of the multilayer reflective film.

[0056] The material forming the protective 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)). Furthermore, the material forming the protective film is preferably resistant to cleaning solutions containing sulfuric acid or alkali.

[0057] The material forming the protective film is preferably a material that is less susceptible to etching than the light-absorbing film when etched by dry etching, which is performed by activating a fluorine-based gas with an electron beam. Furthermore, the material forming the protective film is preferably a material that is less susceptible to etching than the light-absorbing film when etched by dry etching, which is performed by plasma etching, which is performed by activating a fluorine-based gas.

[0058] Specific examples of materials that form a protective film include materials containing ruthenium (Ru). The material that forms the protective film may be pure ruthenium (Ru), or a ruthenium (Ru) compound containing ruthenium (Ru) and one or more elements selected from molybdenum (Mo), niobium (Nb), zirconium (Zr), yttrium (Y), boron (B), rhodium (Rh), titanium (Ti), and lanthanum (La). However, it is preferable that the ruthenium (Ru) compound does not contain platinum (Pt). Furthermore, the material forming the protective film may contain oxygen (O), nitrogen (N), carbon (C), etc., but it is preferable that it be elemental ruthenium (Ru), or a ruthenium (Ru) compound consisting of ruthenium (Ru) and one or more elements selected from molybdenum (Mo), niobium (Nb), zirconium (Zr), yttrium (Y), boron (B), rhodium (Rh), titanium (Ti), and lanthanum (La).

[0059] The protective film may be a single layer or a multilayer film (for example, a film composed of 2 to 4 layers). The protective film may also have a gradient composition. A thinner protective film results in higher reflectivity of exposure light from the multilayer reflective film of the reflective photomask, allowing more exposure light to reach the wafer during exposure using the reflective photomask, thus 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 protective function against the multilayer reflective film may be lost. Therefore, the thickness of the protective film is preferably 1 nm or more, more preferably 1.2 nm or more, and preferably 6 nm or less, more preferably 4 nm or less.

[0060] The combined reflectivity of the multilayer reflective film and protective film to exposure light is preferably 63.5% or higher, and more preferably 65% ​​or higher, because a higher reflectivity allows more exposure light to be used for photolithography.

[0061] If the protective film blocks both the exposure light incident on the multilayer reflective film and the reflected light from the multilayer reflective film, the reflectivity of the multilayer reflective film decreases, reducing the amount of reflected light that can be effectively used for wafer exposure. Therefore, the extinction coefficient of the protective film is preferably 0.035 or less, more preferably 0.03 or less. On the other hand, if the extinction coefficient is too low, the protective film loses its function of protecting the multilayer reflective film. Therefore, the extinction coefficient of the protective film is preferably 0.018 or more, more preferably 0.02 or more.

[0062] 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.

[0063] 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)).

[0064] The light-absorbing film contains ruthenium (Ru) and platinum (Pt). If the light-absorbing film is composed of multiple layers, each layer constituting the multilayer contains both ruthenium (Ru) and platinum (Pt). Specifically, examples of materials used to form the light-absorbing film (single-layer and multilayer layers) 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 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).

[0065] 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.

[0066] In the present invention, the light-absorbing film is a film having a phase-shift function, that is, a phase-shift film. The light-absorbing film having a phase-shift function 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.

[0067] The reflective photomask blank and reflective photomask of the present invention can be described 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] The thickness of the light-absorbing film is preferably 32 nm or more, more preferably 34 nm or more, and also preferably 38 nm or less, more preferably 37 nm or less, and even more preferably 36 nm or less, from the viewpoint of ensuring light absorption function and phase shift function, and minimizing the influence of shadowing effect.

[0073] 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.

[0074] When etching the pattern of a light-absorbing film, after the pattern of the light-absorbing film is etched, the etching may reach the protective film and etch the protective film as well. If the protective film is completely removed, it will no longer be able to perform its function in a reflective mask. When electron beam correction is applied to the pattern of a light-absorbing film formed from a material containing ruthenium (Ru) and platinum (Pt), and the protective film and the light-absorbing film are etched under the same conditions by dry etching using a fluorine-based gas activated by an electron beam, the ratio of the etching rate of the light-absorbing film to the etching rate of the protective film (selectivity ratio) is preferably 50 or more, more preferably 70 or more, and even more preferably 100 or more.

[0075] Furthermore, when etching the pattern of the light-absorbing film, after the pattern of the light-absorbing film is etched, the etching may reach the protective film and etch the protective film as well. If the protective film is completely removed, it will no longer be able to perform its function in a reflective mask. In particular, if the etching rate of the light-absorbing film is too low compared to the etching rate of the protective film, the protective film may be removed due to over-etching of the light-absorbing film. For this reason, when the protective film and the light-absorbing film are etched under the same conditions using dry etching with plasma-induced fluorine-based gas, the ratio of the etching rate of the light-absorbing film to the etching rate of the protective film (selectivity ratio) is preferably 4 or higher, more preferably 5 or higher, and even more preferably 8 or higher.

[0076] 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 nm or more, more preferably 1.2 nm or more.

[0077] 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.

[0078] 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)).

[0079] 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).

[0080] 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.

[0081] 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).

[0082] 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).

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] When forming a protective film with a material containing ruthenium (Ru), a ruthenium (Ru) target can be used as the sputtering target, and if necessary, targets containing other elements that make up the protective film can be used.

[0090] When forming a light-absorbing film made from a material containing ruthenium (Ru) and platinum (Pt), a ruthenium (Ru) target and a platinum (Pt) target can be used as sputtering targets. When forming a light-absorbing film made from a material containing niobium (Nb) along with ruthenium (Ru) and platinum (Pt), a niobium (Nb) target can also be used as a sputtering target.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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).

[0101] 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.

[0102] The method for forming the resist film (coating the resist) is not particularly limited, and known techniques such as spin coating can be applied.

[0103] 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.

[0104] 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).

[0105] The following are specific methods for manufacturing a reflective photomask from the reflective photomask blank of the present invention.

[0106] 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.

[0107] 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 the 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.

[0108] 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.

[0109] Next, the [B] resist film 6 is patterned to form a resist pattern 6a (Figure 6(B)).

[0110] 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)).

[0111] Next, remove the resist pattern 6a (Figure 6(D)). Step [D] can be performed after step [C1] or step [F1].

[0112] 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)).

[0113] 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.

[0114] The dry etching using a fluorine-based gas in the [F1] step and the subsequent dry etching using a chlorine-based gas in the [G1] step are preferably carried out so that a protective film remains after the pattern of the first layer is removed (after etching of the pattern of the first layer is completed), specifically, preferably with a thickness of 1 nm or more, more preferably 1.2 nm or more.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] Next, the [B] resist film 6 is patterned to form a resist pattern 6a (Figure 7(B)).

[0119] 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)).

[0120] Next, remove the resist pattern 6a (Figure 7(D)). Step [D] can be performed after step [C2] or step [E2].

[0121] 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)).

[0122] 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)).

[0123] 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.

[0124] 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 so 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), specifically, preferably with a thickness of 1 nm or more, more preferably 1.2 nm or more.

[0125] 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]

[0126] The present invention will be specifically described below with reference to examples, comparative examples, and reference examples, but the present invention is not limited to the following examples.

[0127] [Example 1A] A reflective photomask blank was manufactured by sequentially laminating a multilayer reflective film, a protective film, a light-absorbing film, and a hard mask film (first and second layers) on a quartz substrate measuring 152 mm square and approximately 6 mm thick.

[0128] 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).

[0129] Next, using ruthenium (Ru), niobium (Nb), and rhodium (Rh) targets, and argon (Ar) gas as the sputtering gas, sputtering was performed using the ruthenium (Ru), niobium (Nb), and rhodium (Rh) targets by adjusting the power applied to the targets and the flow rate of the sputtering gas. A protective film made of ruthenium-niobium-rhodium (RuNbRh) was then formed on the multilayer reflective film.

[0130] Table 1 shows the composition, extinction coefficient k, and thickness of the protective film, as well as the combined reflectance R(M+P) of the multilayer reflective film and protective film for light at a wavelength of 13.5 nm. The extinction coefficient was measured using a refractive index-extinction coefficient meter (the same applies to the extinction coefficient measurements below). The thickness was measured using an X-ray diffractometer (the same applies to the thickness measurements below (excluding the thickness of the resist pattern (resist film))). The reflectance was measured using a reflectometer for light at an incident angle of 6 degrees (the same applies to the reflectance measurements below).

[0131] 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.

[0132] Table 1 shows the composition, thickness, reflectance (relative reflectance R(A) to the multilayer reflective film and protective film) and phase difference (relative phase difference to the multilayer reflective film and protective film) of the light-absorbing 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 analysis of the composition below). The phase difference was calculated from the measured values ​​of the refractive index and extinction coefficient using a refractive index / extinction coefficient analyzer (the same method was used for the calculation of the phase difference below).

[0133] 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.

[0134] Next, a silicon (Si) target was used as the target, and argon (Ar) gas and nitrogen (N2) gas were used as the sputtering gases. By adjusting the power applied to the target and the flow rate of the sputtering gas, sputtering was performed to form a second hard mask film made of silicon nitride (SiN) 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.

[0135] [Examples 2A-10A, Comparative Examples 1A-9A, Reference Example 1A] 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 sputtering gas flow rate, and the sputtering time kept the same or changed. The light-absorbing film was formed in the same manner as in Example 1A, with the applied power to the target, the sputtering gas flow rate, and the sputtering time changed. Furthermore, a reflective photomask blank was obtained by forming only the first layer of the hard mask film (Examples 9A, 10A) or both the first and second layers (Examples 1A-8A, Comparative Examples 1A-9A) in the same manner as in Example 1A, with the applied power to the target, the sputtering gas flow rate, and the sputtering time kept the same or changed, or by not forming either the first or second layer of the hard mask film (Reference Example 1A).

[0136] In Example 4A, a silicon (Si) 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 silicon oxynitride (SiON). Except for the second layer of the hard mask film, the procedure was the same as in Example 1A.

[0137] In Example 5A, 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.

[0138] In Example 6A, a chromium (Cr) 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 chromium oxynitride (CrON). Except for the first layer of the hard mask film, the procedure was the same as in Example 1A.

[0139] In Example 7A, 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.

[0140] In Example 8A, a ruthenium (Ru) target, a platinum (Pt) target, and a niobium (Nb) target were used as the light-absorbing film, 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 to form a film made of ruthenium-platinum-niobium (RuPtNb). Except for the light-absorbing film, the procedure was the same as in Example 1A.

[0141] In Example 9A, the second layer of the hard mask film was not formed.

[0142] In Example 10A, a chromium (Cr) 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. The power applied to the target and the flow rate of the sputtering gases were adjusted to perform sputtering, forming a layer of chromium oxynitride (CrON), and the second layer of the hard mask film was not formed. Except for the first layer of the hard mask film, the procedure was the same as in Example 1A.

[0143] In Comparative Example 1A, a tantalum (Ta) target was used as the light-absorbing film, and argon (Ar) gas and nitrogen (N2) gas were used as the sputtering gases. By adjusting the power applied to the target and the flow rate of the sputtering gas, sputtering was performed to form a film made of tantalum nitride (TaN). Except for the light-absorbing film, the procedure was the same as in Example 1A.

[0144] In Comparative Examples 2A and 3A, a ruthenium (Ru) target and chromium (Cr) were used as the light-absorbing film, and argon gas (Ar gas) was used as the sputtering gas. The power applied to the target and the flow rate of the sputtering gas were adjusted to perform sputtering and form a film made of ruthenium-chromium (RuCr). Except for the light-absorbing film, the procedure was the same as in Example 1A.

[0145] In Comparative Example 4A, a ruthenium (Ru) target and chromium (Cr) were used as the target for the light-absorbing film, and argon (Ar) gas and nitrogen (N2) gas were used as the sputtering gases. By adjusting the power applied to the target and the flow rate of the sputtering gas, sputtering was performed to form a film made of ruthenium chromium nitride (RuCrN). Except for the light-absorbing film, the procedure was the same as in Example 1A.

[0146] In Comparative Example 9A, a ruthenium (Ru) target and a niobium (Nb) target were used as the protective film and 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 to form a film made of ruthenium niobium (RuNb). Except for the protective film, the procedure was the same as in Example 1A.

[0147] In Reference Example 1A, neither the first nor the second layer of the hard mask film was formed.

[0148] Table 1 shows the composition, extinction coefficient k, and thickness of the protective film, as well as the combined reflectance R(M+P) of the multilayer reflective film and protective film for light at a wavelength of 13.5 nm. Table 1 also shows the composition, thickness, reflectance (relative reflectance R(A) to the multilayer reflective film and protective film), and phase difference (relative phase difference to the multilayer reflective film and protective film) for light at a wavelength of 13.5 nm. Furthermore, Table 2 shows the composition and thickness of the first and second layers of the hard mask film.

[0149] [Clear time of dry etching of the second layer of a hard mask film using fluorine-based gas] Using the reflective photomask blanks obtained in Examples 1A to 8A and Comparative Examples 1A to 9A, the time until the second layer of the hard mask film disappeared (clear time T(H2)) was measured by dry etching with a fluorine-based gas. Clear time was defined as the time until the endpoint was detected when dry etching was performed on the second layer of the hard mask film under the following conditions (Condition 1). The results are shown in Table 2.

[0150] <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

[0151] [Clear time of dry etching of the first layer of a hard mask film using chlorine-based gas] For the reflective photomask blanks of Examples 1A to 8A and Comparative Examples 1A to 9A, the clear time of dry etching of the second layer of the hard mask film using a fluorine-based gas was measured. Furthermore, using the reflective photomask blanks obtained in Examples 9A and 10A, the time until the first layer of the hard mask film disappeared (clear time T(H1)) was measured by dry etching using a chlorine-based gas containing oxygen (O). Clear time was defined as the time until endpoint detection (time to endpoint) when dry etching was performed on the first layer of the hard mask film under the following conditions (Condition 2). The results are shown in Table 2 (also shown in Table 3).

[0152] <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

[0153] [Table 1]

[0154] [Table 2]

[0155] [Clear time of dry etching of light-absorbing films using fluorine-based gases] For the reflective photomask blanks of Examples 1A to 10A and Comparative Examples 1A to 9A, the clear time of dry etching of the first layer of the hard mask film using a chlorine-based gas was measured. Furthermore, using the reflective photomask blank obtained in Reference Example 1A, the time until the light-absorbing film disappeared (clear time T(A)) was measured by dry etching using a fluorine-based gas. Clear time was defined as the time until the endpoint was detected (time to endpoint) when dry etching was performed on the light-absorbing film under the above-mentioned dry etching conditions using a fluorine-based gas (Condition 1). From the thickness of the light-absorbing film and the clear time, the etching rate E(A) of the light-absorbing film by dry etching using a fluorine-based gas was determined. F The result was calculated. The results are shown in Table 3.

[0156] [Clear time of dry etching of protective film using fluorine-based gas] For the reflective photomask blanks obtained in Examples 1A to 10A, Comparative Examples 1A to 9A, and Reference Example 1A, the clear time of dry etching of the light-absorbing film using a fluorine-based gas was measured, and then the time until the protective film disappeared (clear time) was measured by dry etching using a fluorine-based gas. Clear time was defined as the time until the endpoint was detected when dry etching was performed on the protective film under the above-mentioned dry etching conditions using a fluorine-based gas (Condition 1). From the thickness of the protective film and the clear time, the etching rate E(P) of the protective film by dry etching using a fluorine-based gas was calculated. F The etching rate E(P) of the protective film by dry etching using a fluorine-based gas was calculated. The results are shown in Table 3. In addition, the selectivity ratio was calculated as the etching rate E(P) of the protective film by dry etching using a fluorine-based gas. F Etching rate E(A) of the light-absorbing film relative to ) F The ratio of (E(A F ) / E(P F The result was calculated. The results are shown in Table 3.

[0157] [Clear time of dry etching of protective film using chlorine-based gas] For the reflective photomask blanks obtained in Examples 1A to 10A, Comparative Examples 1A to 9A, and Reference Example 1A, after measuring the clear time of dry etching using a fluorine-based gas for the light absorption film, the time (clear time) until the protective film disappeared was measured by dry etching using a chlorine-based gas containing oxygen (O). The clear time was defined as the time until endpoint detection (time to endpoint) under the dry etching conditions (Condition 2) using the above chlorine-based gas for the protective film. From the thickness of the protective film and the clear time, the etching rate E(P C ) of the protective film by dry etching using a chlorine-based gas was calculated. The results are shown in Table 3.

[0158] [Amount of protective film disappearance during production of reflective photomask] The protective film is exposed to dry etching (including over-etching) using a chlorine-based gas when removing the pattern of the first layer of the hard mask film. The reflective photomask blank having the first layer of the hard mask film is exposed to dry etching using a fluorine-based gas for over-etching when patterning the light absorption film.

[0159] For the reflective photomask blanks obtained in Examples 1A to 10A, Comparative Examples 1A to 9A, and Reference Example 1A, the clear time T(A) of dry etching using a fluorine-based gas for the light absorption film, the etching rate E(P F ) of dry etching using a fluorine-based gas for the protective film, the clear time T(H1) of dry etching using a chlorine-based gas for the first layer of the hard mask film, and the etching rate E(P C ) of dry etching using a chlorine-based gas for the protective film were used to calculate the amount (thickness) of the protective film that disappeared when producing a reflective photomask from the reflective photomask blank using the following formula T(A)×15%×E(P F )+T(H1)×(100% + 100%)×E(P C ) The calculations were performed as follows. Note that the overetching of the light-absorbing film using fluorine-based gas dry etching was assumed to be 15%, and the overetching of the first layer of the hard mask film using chlorine-based gas dry etching was assumed to be 100%. In this case, the time the protective film is exposed to dry etching using fluorine-based gas is the overetching time only, while the time the protective film is exposed to dry etching using chlorine-based gas is the sum of the clear time and the overetching time.

[0160] Furthermore, the remaining amount (thickness) of the protective film after manufacturing a reflective photomask from a reflective photomask blank was calculated from the thickness of the formed protective film and the amount of protective film lost (thickness). The results are shown in Table 3.

[0161] [Table 3]

[0162] [Examples 1B-8B, Comparative Examples 1B-9B] To evaluate NILS and the optimal focus value range, reflective photomasks were manufactured from the reflective photomask blanks of Examples 1A-8A and Comparative Examples 1A-9A. 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.

[0163] Next, using an electron beam lithography apparatus, a dose of 100 μC / cm² was used. 2Next, a line and space pattern (long side dimension 1000 nm, 100,000 lines) was drawn. The widths of the line and space patterns were set to 13 different widths for the line pattern (changed in 2 nm intervals within the range of 88 to 112 nm) and 41 different widths for the space pattern (changed in 2 nm intervals within the range of 88 to 168 nm). By changing the combination of line and space pattern widths in various ways, line and space patterns were formed. Next, heat treatment (PEB: Post Exposure Bake) was performed at 110°C for 14 minutes using a heat treatment device. Then, development was performed for 40 seconds using paddle development to form a resist pattern.

[0164] 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. The etching time was set to the clear time T(H2) of the etching of the second layer of the hard mask film plus 15% over-etching, and the dry etching was performed under the conditions for dry etching with a fluorine-based gas (Condition 1) described above, to form the pattern of the second layer of the hard mask film.

[0165] 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).

[0166] Next, using the pattern of the second layer of the obtained hard mask film 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 clear time T(H1) of the etching of the first layer of the hard mask film plus 300% over-etching, and the dry etching was performed 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.

[0167] 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. The etching time was set to the clear time T(A) of the etching of the light-absorbing film plus 15% over-etching, and the dry etching was performed under the conditions for dry etching with a fluorine-based gas (Condition 1) described above, forming the pattern of the light-absorbing film and removing the pattern of the second layer of the hard mask film.

[0168] 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 clear time T(H1) of the etching of the first layer of the hard mask film plus 100% over-etching, under the above conditions (Condition 2). This removed the pattern of the first layer of the hard mask film and obtained a reflective photomask.

[0169] [Examples 9B, 10B] To evaluate NILS and the optimal focus value range, reflective photomasks were fabricated from the reflective photomask blanks of Examples 9A and 10A. 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.

[0170] 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.

[0171] 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 clear time T(H1) of the first layer of the hard mask film 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.

[0172] Next, the remaining resist pattern was removed by washing with sulfuric acid peroxide.

[0173] 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. The etching time was defined as the clear time T(A) of the light-absorbing film etching plus 15% over-etching, and the dry etching was carried out under the conditions for dry etching with a fluorine-based gas (Condition 1) described above to form the pattern of the light-absorbing film.

[0174] 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 clear time T(H1) of the etching of the first layer of the hard mask film plus 100% over-etching, under the dry etching conditions using the chlorine-based gas described above (Condition 2). This removed the pattern of the first layer of the hard mask film, obtaining a reflective photomask.

[0175] [Reference example 1B] To evaluate NILS and the optimal focus value range, a reflective photomask was fabricated from the reflective photomask blank of Reference Example 1A. First, a 1200 nm thick resist film was formed by spin-coating a positive-type chemically amplified electron beam resist onto the light absorption film of the reflective photomask blank. In this case, the film was formed thickly so that the resist pattern would not completely disappear while the light absorption film pattern was being formed.

[0176] Next, a line-and-space pattern was formed in the same manner as in Example 1B, except that the development time was set to 220 seconds. A heat treatment and development process were then performed to form a resist pattern. In this case, since the resist film was thicker, the development time was set to be longer.

[0177] Next, using the obtained resist pattern as an etching mask, dry etching with a fluorine-based gas was performed on the light-absorbing film. The etching time was defined as the clear time T(A) of the light-absorbing film etching plus 15% over-etching, and the dry etching was carried out under the conditions for dry etching with a fluorine-based gas (Condition 1) described above to form a pattern on the light-absorbing film.

[0178] Next, the remaining resist pattern was removed by washing with sulfuric acid peroxide to obtain a reflective photomask.

[0179] [NILS's evaluation] The NILS of the line-and-space pattern of the light-absorbing film was evaluated for the obtained reflective photomask under the following conditions (Condition 3) using a wafer transfer simulator capable of measuring the gradient of the spatial image. The wafer transfer simulator capable of measuring the gradient of the spatial image has an illumination system and projection system almost equivalent to that of a wafer exposure apparatus, and it is possible to measure the gradient of the spatial image of a specific pattern by illuminating a minute area of ​​the reflective photomask with exposure light.

[0180] <Wafer Transfer Simulator Settings (Condition 3)> NA (Natural Aperture of Wafer Lithography Machine): 0.33 Lighting conditions: Dipole Simga-in:0.7 Sigma-out:0.9 Center angle: 0 degrees Blade angle: 30 degrees Wafer defocus: 0.03 μm

[0181] The NILS of all line and space patterns obtained by varying the dimensions of the line and space patterns of the reflective photomask was evaluated, and the maximum value of NILS was evaluated. NILS is calculated using the following formula: NILS = (dI / dx) / (W×Ith) (In the formula, W is the desired pattern dimension, Ith is the threshold light intensity that gives W, and dI / dx is the gradient of the spatial image.) This was determined by [method]. Note that in Reference Example 1B (the reflective photomask blank of Reference Example 1A), where the resist film was thick, it was not possible to resolve the line pattern and space pattern of the set width, so evaluation was not performed. Table 4 shows the difference between the NILS (maximum value) and the NILS (maximum value) of Comparative Example 1, which corresponds to a binary type reflective photomask.

[0182] [Evaluation of the optimal focus value range] The focus values ​​of all line and space patterns obtained from the reflective photomask were evaluated by changing the dimensions of the line and space patterns, and the range of widths (difference between the maximum and minimum values) of the line and space patterns that yielded the optimal focus value was evaluated. In Reference Example 1B (the reflective photomask blank of Reference Example 1A), where the resist film was thick, it was not possible to resolve the line and space patterns of the set width, so evaluation was not performed. Table 4 shows the range of the optimal focus value and the difference from the range of the optimal focus value for Comparative Example 4, where the reflectivity of the light-absorbing film was about 5%.

[0183] [Table 4]

[0184] [Evaluation of the amount of resist film loss] A positive-type chemically amplified electron beam resist was spin-coated onto the reflective photomask blanks obtained in Examples 1A to 10A, Comparative Examples 1A to 9A, and Reference Example 1A to form a resist film of a predetermined thickness. Next, an electron beam lithography apparatus was used to measure the resist at a dose of 100 μC / cm². 2 Next, 20 isolated line patterns with a long side of 100,000 nm and a short side of 60 nm were drawn. Then, a heat treatment (PEB: Post Exposure Bake) was performed at 115°C for 14 minutes using a heat treatment device. Next, development was performed using paddle development for a predetermined time to form a resist pattern. Then, using the resist pattern as an etching mask, etching was performed on the film or layer in contact with the resist pattern to form a pattern of the film or layer in contact with the resist pattern. After that, the thickness of the resist pattern remaining on the pattern of the film or layer in contact with the resist pattern was measured, and the thickness that was lost was calculated. The results are shown in Table 5. The thickness of the resist pattern (resist film) was measured using an atomic force microscope (AFM), and the measurement range was a 200 nm × 200 nm square area.

[0185] In Examples 1A to 8A and Comparative Examples 1A to 9A, the amount of resist film reduction (thickness) was evaluated when the pattern of the second layer of the hard mask film was formed on the reflective photomask blanks obtained by dry etching with a fluorine-based gas. The resist film thickness was 80 nm, the resist pattern development time was 40 seconds, and the etching time was defined as the clear time T(H2) of etching the second layer of the hard mask film plus 15% over-etching. Dry etching was performed on the second layer of the hard mask film under the dry etching conditions (Condition 1) described above using a fluorine-based gas.

[0186] In Examples 9A and 10A, the amount of resist film reduction (thickness) was evaluated when the first layer pattern of the hard mask film was formed on the reflective photomask blanks obtained by dry etching using a chlorine-based gas. The resist film thickness was 80 nm, the resist pattern development time was 40 seconds, and the etching time was defined as the clear time T(H1) of the first layer etching of the hard mask film plus 300% over-etching. Dry etching was performed on the first layer of the hard mask film under the dry etching conditions (Condition 2) described above using a chlorine-based gas.

[0187] The reflective photomask blank obtained in Reference Example 1A was used to evaluate the amount of resist film reduction (thickness) when a light-absorbing film pattern was formed by dry etching using a fluorine-based gas. The resist film thickness was 1500 nm, the resist pattern development time was 220 seconds, and the etching time was defined as the clear time T(A) of the light-absorbing film etching plus 15% over-etching. Dry etching was performed on the light-absorbing film under the above-mentioned dry etching conditions using a fluorine-based gas (Condition 1).

[0188] [Determining the minimum thickness of the resist film] If the thickness of the resist pattern remaining after etching is too thin, the plasma in dry etching can reach the film or layer in contact with the resist pattern, forming pinhole defects. Therefore, the thickness of the resist pattern remaining after dry etching was set to 15 nm, and the minimum thickness of the resist film required for the resist pattern to remain at a thickness of 15 nm was calculated from the amount of resist loss obtained. The results are shown in Table 5.

[0189] If the minimum thickness of the resist film is 40 nm or more, the calculated thickness is used as the thickness of the resist film for resolution limit evaluation, as described later. If the minimum thickness of the resist film is less than 40 nm, 40 nm, which is the lower limit of the thickness at which a resist film can be formed stably with the resist material used, is used as the thickness of the resist film for resolution limit evaluation, as described later. The thicknesses of the resist films for resolution limit evaluation are shown in Table 5.

[0190] [Examples 1C-8C, Comparative Examples 1C-9C] To evaluate the resolution limit of fine patterns corresponding to the assist patterns of isolated line patterns, reflective photomasks were manufactured from the reflective photomask blanks of Examples 1A to 8A and Comparative Examples 1A to 9A. First, a positive-type chemically amplified electron beam resist was spin-coated onto the second layer of the hard mask film of the reflective photomask blank to form a resist film of the thickness required for resolution limit evaluation, as shown in Table 5.

[0191] Next, using an electron beam lithography apparatus, a dose of 100 μC / cm² was used. 2 As test patterns equivalent to assist patterns for line patterns, a total of 200,000 isolated patterns with different short side dimensions were drawn, each with a long side dimension of 80 nm and a short side dimension varying from 10 nm to 50 nm in 1 nm increments. Next, heat treatment (PEB: Post Exposure Bake) was performed at 110°C for 14 minutes using a heat treatment device. Then, development was performed for 40 seconds using paddle development to form a resist pattern.

[0192] 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. The etching time was set to the clear time T(H2) of the etching of the second layer of the hard mask film plus 15% over-etching, and the dry etching was performed under the conditions for dry etching with a fluorine-based gas (Condition 1) described above, to form the pattern of the second layer of the hard mask film.

[0193] Next, the remaining resist pattern was removed by washing with sulfuric acid peroxide.

[0194] Next, using the pattern of the second layer of the obtained hard mask film 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 clear time T(H1) of the etching of the first layer of the hard mask film plus 300% over-etching, and the dry etching was performed 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.

[0195] 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. The etching time was set to the clear time T(A) of the etching of the light-absorbing film plus 15% over-etching, and the dry etching was performed under the conditions for dry etching with a fluorine-based gas (Condition 1) described above, forming the pattern of the light-absorbing film and removing the pattern of the second layer of the hard mask film.

[0196] Next, for the pattern of the first layer of the hard mask film, the etching time was defined as the clear time T(H1) of etching the first layer of the hard mask film plus 100% over-etching. Dry etching using a chlorine-based gas was performed under the conditions for dry etching using a chlorine-based gas (condition 2) described above to remove the pattern of the first layer of the hard mask film and obtain a reflective photomask.

[0197] [Examples 9C, 10C] To evaluate the resolution limit of fine patterns corresponding to the assist patterns of isolated line patterns, reflective photomasks were fabricated from the reflective photomask blanks of Examples 9A and 10A. First, a positive-type chemically amplified electron beam resist was spin-coated onto the first layer of the hard mask film of the reflective photomask blank to form a resist film of the thickness required for resolution limit evaluation, as shown in Table 5.

[0198] Next, in the same manner as in Example 1C, isolated patterns were formed, and then heat treatment and development treatment were performed to form a resist pattern.

[0199] 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 clear time T(H1) of the first layer of the hard mask film 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.

[0200] Next, the remaining resist pattern was removed by washing with sulfuric acid peroxide.

[0201] 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. The etching time was defined as the clear time T(A) of the light-absorbing film etching plus 15% over-etching, and the dry etching was carried out under the conditions for dry etching with a fluorine-based gas (Condition 1) described above to form the pattern of the light-absorbing film.

[0202] 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 clear time T(H1) of the etching of the first layer of the hard mask film plus 100% over-etching, under the dry etching conditions using the chlorine-based gas described above (Condition 2). This removed the pattern of the first layer of the hard mask film, obtaining a reflective photomask.

[0203] [Reference example 1C] To evaluate the resolution limit of fine patterns corresponding to the assist patterns of isolated line patterns, a reflective photomask was fabricated from the reflective photomask blank of Reference Example 1A. First, a positive-type chemically amplified electron beam resist was spin-coated onto the light-absorbing film of the reflective photomask blank to form a resist film of the thickness required for resolution limit evaluation, as shown in Table 5.

[0204] Next, an isolated pattern was formed in the same manner as in Example 1C, except that the development time was set to 220 seconds. A heat treatment and development treatment were then performed to form a resist pattern. In this case, since the resist film was thick, the development time was set to be longer.

[0205] Next, using the obtained resist pattern as an etching mask, dry etching with a fluorine-based gas was performed on the light-absorbing film. The etching time was defined as the clear time T(A) of the light-absorbing film etching plus 15% over-etching, and the dry etching was carried out under the conditions for dry etching with a fluorine-based gas (Condition 1) described above to form a pattern on the light-absorbing film.

[0206] Next, the remaining resist pattern was removed by washing with sulfuric acid peroxide to obtain a reflective photomask.

[0207] [Evaluation of the resolution limit] The resolution limit of the test patterns of the obtained photomasks was evaluated using a mask appearance inspection device. For all isolated patterns, pattern disappearance, pattern collapse, and pattern shape defects were evaluated. Isolated patterns in which the mask appearance inspection device detected any of these were considered defective, and the resolution limit was defined as the smallest short side dimension in which no defective isolated patterns were detected. Note that in Reference Example 1C (a reflective photomask blank from Reference Example 1A) with a thick resist film, it was not possible to resolve isolated patterns of the set width, so evaluation was not performed. The results are shown in Table 5.

[0208] [Table 5]

[0209] Using the reflective photomasks obtained in Examples 1C to 10C, Comparative Examples 1C to 9C, and Reference Example 1C, dry etching was performed on the light-absorbing film and the protective film under the following conditions (Condition 4), using a fluorine-based gas activated by an electron beam to etch the film, which is used to modify the pattern of the light-absorbing film on the reflective photomask. The etching amount (thickness) and etching time were measured, and the etching rate was calculated from these values. The selectivity ratio was then calculated as the ratio of the etching rate of the light-absorbing film to the etching rate of the protective film. The results are shown in Table 6.

[0210] <Conditions for dry etching using fluorine-based gas activated by electron beam (Condition 4)> Equipment: Electron beam correction system (Carl Zeiss MeRiT Next) Gas: XeF2 gas

[0211] [Table 6]

[0212] 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]

[0213] 1 circuit board 2 Multilayer reflective film 3 Protective film 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 formed on the multilayer reflective film for protecting the multilayer reflective film, A pattern of a light-absorbing film formed on the protective film in contact with the protective film, which absorbs the exposure light and has a phase-shift function, and Equipped with, The extinction coefficient of the protective film is 0.018 or more and 0.035 or less, and the thickness of the protective film is 1 nm or more and 6 nm or less. 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. A reflective photomask characterized by the following features.

2. The reflective photomask according to claim 1, characterized in that the light-absorbing film further contains niobium (Nb), and the niobium (Nb) content is 4 atomic percent or less.

3. The reflective photomask according to claim 1, characterized in that the material forming the light-absorbing film is resistant to dry etching using a chlorine-based gas and can be removed by dry etching using a fluorine-based gas.

4. The reflective photomask according to claim 1, characterized in that when the protective film and the light-absorbing film are etched under the same conditions by dry etching, in which a fluorine-based gas is activated with an electron beam, the ratio of the etching rate of the light-absorbing film to the etching rate of the protective film is 50 or more.

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 formed on the multilayer reflective film for protecting the multilayer reflective film, A light-absorbing film is formed on the protective film in contact with the protective film, which absorbs the exposure light and has a phase-shift function. A hard mask film formed on the light-absorbing film in contact with the light-absorbing film, Equipped with, The extinction coefficient of the protective film is 0.018 or more and 0.035 or less, and the thickness of the protective film is 1 nm or more and 6 nm or less. 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. A reflective photomask blank characterized by the following features.

6. The reflective photomask blank according to claim 5, characterized in that the light-absorbing film further contains niobium (Nb), and the niobium (Nb) content is 4 atomic percent or less.

7. The reflective photomask blank according to claim 5, characterized in that the material forming the light-absorbing film is resistant to dry etching using a chlorine-based gas and can be removed by dry etching using a fluorine-based gas.

8. The reflective photomask blank according to claim 5, characterized in that when the protective film and the light-absorbing film are etched under the same conditions by dry etching, in which a fluorine-based gas is activated with an electron beam, the ratio of the etching rate of the light-absorbing film to the etching rate of the protective film is 50 or more.

9. The reflective photomask blank according to claim 5, characterized in that when the protective film and the light-absorbing film are etched under the same conditions by dry etching using plasma-enhanced fluorine-based gas, the ratio of the etching rate of the light-absorbing film to the etching rate of the protective film is 4 or more.

10. 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.

11. The reflective photomask blank according to claim 10, characterized in that the first layer of the hard mask film contains either or both chromium (Cr) and ruthenium (Ru), does not contain silicon (Si) and tantalum (Ta), and has a thickness of 2 nm or more and 14 nm or less.

12. The reflective photomask blank according to claim 10, 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.

13. The reflective photomask blank according to claim 12, characterized in that the second layer of the hard mask film contains one or both of silicon (Si) and tantalum (Ta), does not contain chromium (Cr) and ruthenium (Ru), and has a thickness of 2 nm or more and 14 nm or less.

14. A method for manufacturing a reflective photomask according to claim 1 from a reflective photomask blank according to claim 10 or 11, [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:

15. A method for manufacturing a reflective photomask according to claim 1 from a reflective photomask blank according to claim 12 or 13, [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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