Photomask blank, and method for manufacturing photomask

Abstract

SOLUTION: To provide a photomask blank comprising: a transparent substrate; a membrane formed of a material containing chromium; and a membrane which is constituted of a single layer or plural layers, has a thickness 0.5 to 15 nm, contains tantalum, oxygen or oxygen and nitrogen, and is formed of a material not containing silicon, where a single layer and a layer most separated from at least transparent substrate of layers constituting plural layers are formed of a material containing tantalum which has the content of tantalum by 40 to 80 atom%, the content of oxygen by 5 to 50 atom%, and the content of nitrogen by 50 atom% or less, and the thickness of a layer most separated from the transparent substrate is 0.5 nm or more.EFFECT: Provided is a photomask blank equipped with a membrane which has satisfactory adhesiveness of a resist film even without performing HMDS treatment, high CD uniformity within a membrane plane to etching, and a low etching rate for dry etching using chlorine-based gas containing oxygen, as a membrane formed on a membrane formed of a material containing chromium.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] In recent years, with the miniaturization of semiconductor devices, particularly the increasing integration of large-scale integrated circuits, high pattern resolution is required for projection exposure. To address this issue, phase-shift masks have been developed as a photomask technique to improve the resolution of transferred patterns. The principle of phase-shifting is to adjust the phase of transmitted light passing through an opening in a phase-shift film so that it is approximately 180 degrees inverted relative to the phase of transmitted light passing through the area adjacent to the opening. This causes interference between the transmitted light at the boundary between the opening and the area adjacent to the opening, reducing the light intensity. As a result, the resolution and depth of focus of the transferred pattern are improved. Photomasks that use this principle are collectively called phase-shift masks.

[0003] The most common phase shift mask blank used in the manufacture of phase shift masks has a structure in which a phase shift film is laminated on a transparent substrate such as a glass substrate, and a film formed of a chromium-containing material is laminated on the phase shift film. The phase difference and transmittance of the phase shift film are typically about 175 to 185 degrees and about 6 to 30% relative to the exposure light, respectively. Films formed of materials containing molybdenum and silicon are the mainstream phase shift films. Furthermore, the thickness of the film formed of a chromium-containing material is adjusted to a thickness that, combined with the phase shift film, achieves a predetermined optical density. The film formed of a chromium-containing material is generally used as both a light-shielding film and a hard mask for etching the phase shift film.

[0004] The following method can be used to form a pattern of a phase shift film from the phase shift film of such a phase shift mask blank. First, a resist film is formed on a film made of a chromium-containing material of the phase shift mask blank, a pattern is drawn on the resist film using light or an electron beam, and developed to form a resist film pattern. Then, using the resist film pattern as an etching mask, the film made of the chromium-containing material is etched to form a pattern of the film made of the chromium-containing material. Further, using the pattern of the film made of the chromium-containing material as an etching mask, the phase shift film is etched to form a phase shift film pattern, and then the resist film pattern and the pattern of the film made of the chromium-containing material are removed in order.

[0005] Furthermore, a film made of a chromium-containing material may be left as a light-shielding film outside the portion of the phase shift film pattern where the circuit pattern is formed, to form a light-shielding portion (light-shielding film pattern) at the outer periphery of the phase shift mask so that the combined optical density of the phase shift film and the light-shielding film is 3 or higher. This is to prevent the exposure light from being transmitted through the outer periphery of the phase shift mask when the circuit pattern is transferred to the resist film on the wafer using a wafer exposure device, which may result in the exposure light being irradiated onto the resist film adjacent to the position where the circuit pattern is to be exposed. A common method for forming such a light-shielding film pattern is to form a phase shift film pattern, remove the resist film pattern, form a new resist film, write a pattern on the resist film using light or an electron beam, develop the resist film pattern, and use the resist film pattern as an etching mask to etch only the film made of a chromium-containing material in the circuit pattern portion, leaving a light-shielding portion (light-shielding film pattern) at the outer periphery.

[0006] In the manufacture of photomasks, which require highly accurate pattern formation, dry etching using gas plasma is the mainstream etching method. For dry etching of films formed from materials containing chromium, dry etching using chlorine-based gases is used, while for dry etching of films formed from materials containing molybdenum and silicon, dry etching using fluorine-based gases is used. In particular, for dry etching of films formed from materials containing chromium, it is known that chemical reactivity is enhanced and the etching rate is improved by using a chlorine-based gas, which is the etching gas, as a gas in which chlorine gas (Cl2 gas) is mixed with 10 to 25% by volume of oxygen gas (O2 gas).

[0007] As circuit patterns become finer, technologies for forming finer phase shift film patterns are required. In particular, assist patterns, which are line patterns that support the resolution of the main pattern of a phase shift mask, must be smaller than the main pattern so that they are not transferred to the resist film on the wafer when the circuit pattern is transferred to the resist film on the wafer using a wafer exposure tool. For phase shift masks of a generation in which the pitch of the circuit line-and-space pattern on the wafer is finer than 10 nm, the line width of the assist patterns of the line patterns on the phase shift mask is required to be approximately 40 nm. In this case, to stably manufacture phase shift masks with high-precision circuit patterns formed thereon with a margin for variation, the line width must be narrower than approximately 40 nm, and the line width of the assist patterns is required to be approximately 36 nm.

[0008] To manufacture phase-shift masks with fine patterns, chemically amplified resists are generally used. Chemically amplified resists consist of a base resin, an acid generator, a surfactant, and other components. Because they are compatible with many reactions catalyzed by the acid generated by exposure, they offer high sensitivity. Chemically amplified resists enable the formation of film patterns, such as phase-shift film patterns, with linewidths of 0.2 μm or less. However, even with chemically amplified resists, narrowing the pattern width can cause the resist film pattern to collapse due to impacts from the developer during the development process or pure water during rinsing, resulting in the resolution limit being reached.

[0009] The typical thickness of a resist film used in manufacturing a phase shift mask is about 100 to 150 nm. However, such a thickness makes it difficult to form a finer assist pattern on a phase shift mask. The reason for this is that a thick resist film formed on a film made of a material containing chromium has a high aspect ratio for the resist film pattern, which has a narrow line width for forming the assist pattern. Therefore, during the development process for forming the resist film pattern, the resist film pattern collapses due to impact from the developer or pure water during rinsing.

[0010] To reduce the impact of developer shock or pure water shock during rinsing, it is necessary to reduce the aspect ratio of the resist film pattern. However, if the resist film is thinned, and the resist film disappears during dry etching of a film formed from a chromium-containing material, pinhole defects will be formed in the film formed from the chromium-containing material. If a phase shift film is dry-etched using a pattern of a film formed from a chromium-containing material with pinhole defects as an etching mask, plasma will reach the phase shift film through the pinholes during etching, and pinhole defects will also be formed in the phase shift film. In this case, a normal phase shift mask cannot be manufactured.

[0011] To solve this problem, it was considered to form a film made of a silicon-containing material on a film made of a chromium-containing material and use this as a hard mask film. In this case, the film made of the silicon-containing 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 the silicon-containing material can be as thin as about 80 to 110 nm.

[0012] When dry etching a film made of a material containing chromium using a chlorine-based gas containing oxygen, it is necessary to perform overetching of 100 to 300% of the clear time in addition to the clear time required for the film made of the material containing chromium to disappear. This is because dry etching using a chlorine-based gas containing oxygen is an isotropic etching dominated by chemical components, and if dry etching is performed only for the clear time, the pattern of the film made of the material containing chromium will be insufficiently etched at the boundary with the phase shift film, resulting in a footing shape and preventing the desired pattern width from being stably formed.

[0013] Furthermore, dry etching using chlorine-based gases containing oxygen is an isotropic etching process dominated by chemical components, so the plasma of the chlorine-based gas containing oxygen moves both vertically and horizontally relative to the main surface of the substrate, causing side etching of the film pattern formed from a material containing chromium. To make the critical dimension (CD), which is the pattern line width, uniform across the entire mask surface, it is necessary to obtain an equal amount of side etching across the entire mask surface. To achieve this, a long period of overetching is required until the amount of side etching reaches saturation across the entire mask surface and stabilizes.

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

[0015] The reason why overetching can be performed in a short time when dry etching a film made of a silicon-containing material using a fluorine-based gas is that dry etching using a fluorine-based gas is anisotropic etching dominated by physical components, and the pattern of the film made of a silicon-containing material does not have a footing shape at the boundary with the film made of a chromium-containing material. Also, the fluorine-based gas plasma moves perpendicular to the main surface of the substrate, so the CD of the resist film pattern is faithfully reproduced in the pattern of the film made of a silicon-containing material.

[0016] Since dry etching using fluorine-based gas is anisotropic etching dominated by physical components, the amount of resist lost by dry etching is generally greater than that by dry etching using oxygen-containing chlorine-based gas.Therefore, the resist film for forming a pattern on a film made of a silicon-containing material needs to have a certain thickness.On the other hand, a film made of silicon-containing material functions as an etching mask when dry etching a film made of a chromium-containing material using oxygen-containing chlorine-based gas, and has sufficient etching resistance against dry etching using oxygen-containing chlorine-based gas, so the film made of silicon-containing material as a hard mask film can be relatively thin.If the film made of silicon-containing material is thin, the time required for dry etching using fluorine-based gas on the film made of silicon-containing material can be shortened, and as a result, the resist film required for forming a pattern on a film made of silicon-containing material can also be thin.

[0017] For these reasons, by using a film formed of a silicon-containing material as the hard mask film, it is possible to thin the resist film used for etching the hard mask film, i.e., the resist film formed on and in contact with the hard mask film. Furthermore, by thinning the resist film, the aspect ratio of the resist film pattern is reduced, and the impact of impact from the developer or pure water during rinsing in the development process of resist film pattern formation is reduced, allowing for the formation of a good assist pattern. As a result, high resolution can be achieved in pattern transfer using a phase shift mask.

[0018] On the other hand, when a phase shift film made of a material containing molybdenum and silicon is dry-etched using a fluorine-based gas, the transparent substrate in contact with the phase shift film may also be slightly etched by dry etching to adjust the phase difference to about 175 to 185 degrees with respect to the exposure light. In this case, the phase difference of the phase shift film itself made of a material containing molybdenum and silicon is set to, for example, about 175 to 179 degrees, and the transparent substrate is slightly recessed by over-etching, thereby setting the phase difference of the phase shift mask to about 175 to 185 degrees.

[0019] Specifically, the following method is generally used to manufacture a phase shift mask by patterning a phase shift film from a phase shift mask blank having a phase shift film formed of a material containing molybdenum and silicon, a light-shielding film formed of a material containing chromium, and a hard mask film formed of a material containing silicon formed in this order on a transparent substrate.

[0020] First, a resist film is formed on the hard mask film. Next, a pattern is drawn on the resist film using light or an electron beam and developed to form a resist film pattern. Next, using the resist film pattern as an etching mask, a hard mask film formed from a material containing silicon is dry-etched using a fluorine-based gas to form a hard mask film pattern, and then the resist film pattern is removed. Next, using the hard mask film pattern as an etching mask, a light-shielding film formed from a material containing chromium is dry-etched using a chlorine-based gas containing oxygen to form a light-shielding film pattern. Next, using the light-shielding film pattern as an etching mask, a phase shift film formed from a material containing molybdenum and silicon is dry-etched using a fluorine-based gas to form a phase shift film pattern, and at the same time, the hard mask film pattern is removed. Then, the light-shielding film pattern is removed by etching using a chlorine-based gas containing oxygen.

[0021] WO 2004 / 090635 (Patent Document 1) describes a phase shift mask blank having at least a phase shift film, a chromium film, an etching mask film made of an inorganic material resistant to etching of the chromium film, and a resist film on a light-transmitting substrate. The etching mask film is made of a material containing at least one of molybdenum, silicon, tantalum, and tungsten, specifically, Mo alone, MoSi, MoSiO, MoSiN, MoSiON, Si alone, SiO, SiN, SiON, Ta alone, TaB, W, WSi, and TaSi. Furthermore, the method for manufacturing a phase shift mask described in WO 2004 / 090635 (Patent Document 1) involves exposing a desired pattern on a resist film and developing it to form a resist pattern, and then dry-etching the etching mask film using the resist pattern as a mask to form an etching mask pattern.

[0022] Furthermore, Japanese Patent Laid-Open Publication No. 2013-238691 (Patent Document 2) describes a phase shift mask blank in which a phase shift film, a light-shielding film, and a hard mask are sequentially stacked on a substrate transparent to the exposure wavelength, the phase shift film and the light-shielding film being made of a material that is not substantially etched by dry etching capable of etching the hard mask, the phase shift film and the hard mask being made of a material that is not substantially etched by dry etching capable of etching the light-shielding film, and the light-shielding film being made of a material that is not substantially etched by dry etching capable of etching the phase shift film, and the blank describes a metal compound film containing Cr oxide, Cr nitride, or Cr oxynitride as a main component, or a metal or alloy film containing Cr as a main component, and a Ta film or TaN film as a hard mask. In addition, in the method for manufacturing a phase shift mask described in JP 2013-238691 A (Patent Document 2), a resist film is applied onto a hard mask, patterning is performed, and then a development process is performed to form a resist pattern.The hard mask is then patterned using the resist pattern as a mask by non-oxygen-containing chlorine-based dry etching (dry etching using chlorine gas as the etching gas), thereby forming a hard mask pattern. [Prior art documents] [Patent documents]

[0023] [Patent Document 1] International Publication No. 2004 / 090635 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-238691 Summary of the Invention [Problem to be solved by the invention]

[0024] WO 2004 / 090635 (Patent Document 1) describes a silicon-containing material as a material for an etching mask film, but when a resist film is formed on a film made of the silicon-containing material, the film made of the silicon-containing material is prone to forming hydrophilic hydroxyl groups (OH groups) on the surface, and the hydroxyl groups deteriorate adhesion to the resist. If the adhesion of the resist film to the film made of the silicon-containing material deteriorates, the resist film pattern is likely to collapse during the development step in resist film pattern formation due to impact from the developer or pure water during rinsing, significantly deteriorating resolution.

[0025] Therefore, when forming a resist film on a film formed from a silicon-containing material, in order to improve the adhesion of the resist film to the film formed from the silicon-containing material, the surface of the film formed from the silicon-containing material is usually treated with HMDS (hexamethyldisilazane) before applying a resist onto the film formed from the silicon-containing material, thereby substituting hydroxyl groups with hydrophobic groups and improving the adhesion of the resist film to the film formed from the silicon-containing material.

[0026] However, while HMDS treatment improves the adhesion between silicon-containing films and resist films, it does not fully dissolve the resist during the development process. As a result, in space patterns, the resist is not completely removed from the silicon-containing film, leaving resist residue on the silicon-containing film. This residue acts as an etching mask during etching of the silicon-containing film, leaving areas of the silicon-containing film that should be etched unetched. Ultimately, the phase shift film at the location of the resist residue remains unetched, resulting in defects. While defect repair is possible during the manufacturing process of photomasks such as phase shift masks, and wafer transfer simulations can be used to evaluate the impact of repair on CD, defect repair impacts photomask productivity, and if there are many defects, it can significantly reduce productivity.

[0027] Furthermore, International Publication No. 2004 / 090635 (Patent Document 1) describes elemental Ta, TaB, and TaSi as materials for etching mask films, and Japanese Patent Application Laid-Open No. 2013-238691 (Patent Document 2) describes Ta and TaN as materials for hard masks. However, these materials are susceptible to reaction with oxygen, and when they come into contact with air, an oxide layer is formed unevenly or locally on the surface of the etching mask film or hard mask. In this case, when the etching mask film or hard mask is dry-etched, the etching rate becomes uneven across the film surface, and the CD uniformity within the film surface becomes low and unstable.

[0028] Furthermore, etching mask films and hard masks must be formed to a sufficient thickness so that they will not disappear during dry etching using an oxygen-containing chlorine-based gas, which is used to etch films formed from chromium-containing materials. However, because these materials have a relatively high etching rate when dry etching using an oxygen-containing chlorine-based gas, the etching mask films and hard masks must be formed to a correspondingly large thickness. However, if the etching mask film or hard mask is thick, the resist film must be formed to a large thickness. If the resist film is thick, the aspect ratio of the resist film pattern with a narrow line width becomes high, deteriorating the resolution.

[0029] The present invention has been made to solve the above-mentioned problems, and aims to provide a photomask blank including a film formed on a film formed of a material containing chromium, which film has good adhesion to a resist film even without HMDS (hexamethyldisilazane) treatment, has high uniformity of CD (Critical Dimension) within the film surface against etching, and has a low etching rate against dry etching using an oxygen-containing chlorine-based gas, and a method for manufacturing a photomask using such a photomask blank. [Means for solving the problem]

[0030] As a result of extensive research into solving the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by configuring the film formed of the tantalum-containing material to contain nitrogen and to have a predetermined structure, composition, and thickness in a photomask blank comprising a transparent substrate, a film formed of a chromium-containing material on the transparent substrate, and a film formed of a tantalum-containing material on the film formed of the chromium-containing material, as well as in a photomask blank comprising a film formed of a silicon-containing material between the transparent substrate and the film formed of the chromium-containing material.

[0031] The present inventors have also found that such a photomask blank is particularly suitable when a film formed from a material containing chromium is a light-shielding film, when a film formed from a material containing tantalum is a hard mask film, and when a film formed from a material containing silicon is a phase shift film.

[0032] Furthermore, the present inventors have found that, when producing a photomask from such a photomask blank, a film formed from a material containing tantalum can be etched by dry etching using fluorine gas, and that by forming a resist film in contact with the film formed from the material containing tantalum, and etching the film formed from the material containing tantalum by dry etching using fluorine gas, the film formed from the material containing chromium by dry etching using an oxygen-containing chlorine-based gas, and the film formed from the material containing silicon by dry etching using fluorine gas, it is possible to produce a photomask in which a finer assist pattern is favorably formed in the circuit pattern, and have arrived at the present invention.

[0033] Therefore, the present invention provides the following photomask blank and photomask manufacturing method. 1. A photomask blank comprising: a transparent substrate; a film formed on the transparent substrate and made of a material containing chromium; and a film formed on the film formed of the material containing chromium and made of a material containing tantalum, the film formed of the tantalum-containing material is composed of a single layer or multiple layers, the thickness of the film formed from the material containing tantalum is 0.5 nm or more and 15 nm or less, the tantalum-containing material contains tantalum and oxygen or oxygen and nitrogen, and does not contain silicon; the single layer and at least one of the layers constituting the plurality of layers that is the furthest from the transparent substrate are formed from a material containing tantalum with a tantalum content of 40 atomic % or more and 80 atomic % or less, an oxygen content of 5 atomic % or more and 50 atomic % or less, and a nitrogen content of 50 atomic % or less; The layer furthest from the transparent substrate has a thickness of 0.5 nm or more. A photomask blank characterized by: 2. The photomask blank according to 1, wherein when a film formed from the chromium-containing material and a film formed from the tantalum-containing material are dry-etched using an oxygen-containing chlorine-based gas, the ratio of the etching rate of the film formed from the chromium-containing material to the etching rate of the film formed from the tantalum-containing material is 50 or more. 3. The photomask blank according to 1, wherein the thickness of the film formed from the chromium-containing material is 30 nm or more and 80 nm or less. 4. A photomask blank according to any one of 1 to 3, further comprising a film formed of a silicon-containing material between the transparent substrate and the film formed of the chromium-containing material. 5. The film formed of the silicon-containing material is a phase shift film, the film formed of the material containing chromium is a light-shielding film, The film formed from the material containing tantalum is a hard mask film. 5. The photomask blank according to 4. 6. The photomask blank according to 5, wherein the phase shift film has a phase difference of 175 degrees or more and 185 degrees or less with respect to exposure light, a transmittance of 6% or more and 30% or less, and a thickness of 60 nm or more and 85 nm or less. 7. The photomask blank according to 6, wherein the combined optical density of the light-shielding film and the phase shift film to the exposure light is 3 or more. 8. The photomask blank according to 1, further comprising a resist film having a thickness of 40 nm or more and 120 nm or less, in contact with the side of the film formed from the material containing tantalum that faces away from the transparent substrate. 9. A method for producing a photomask having a circuit pattern of a film formed from the chromium-containing material from the photomask blank according to any one of 1 to 3, comprising the steps of: (A) forming a first resist film in contact with a side of the film formed of the tantalum-containing material that is away from the transparent substrate; (B) patterning the first resist film to form a first resist film pattern; (C) patterning the film formed of the material containing tantalum by dry etching using a fluorine-based gas using the first resist film pattern as an etching mask to form a pattern of the film formed of the material containing tantalum; (D) removing the first resist film pattern; (E) patterning the film formed from the material containing chromium by dry etching using a chlorine-based gas containing oxygen, using the pattern of the film formed from the material containing tantalum as an etching mask, to form a pattern of the film formed from the material containing chromium; (F1) removing the pattern of the film formed of the material containing tantalum by dry etching using a fluorine-based gas; A method for manufacturing a photomask, comprising: 10. A method for producing a photomask having a circuit pattern of a film formed from the silicon-containing material from the photomask blank according to 4, comprising the steps of: (A) forming a first resist film in contact with a side of the film formed of the tantalum-containing material that is away from the transparent substrate; (B) patterning the first resist film to form a first resist film pattern; (C) patterning the film formed of the material containing tantalum by dry etching using a fluorine-based gas using the first resist film pattern as an etching mask to form a pattern of the film formed of the material containing tantalum; (D) removing the first resist film pattern; (E) patterning the film formed from the material containing chromium by dry etching using a chlorine-based gas containing oxygen, using the pattern of the film formed from the material containing tantalum as an etching mask, to form a pattern of the film formed from the material containing chromium; (F2) patterning the film formed of the silicon-containing material by dry etching using a fluorine-based gas, using the pattern of the film formed of the chromium-containing material as an etching mask, to form a pattern of the film formed of the silicon-containing material including the circuit pattern, and simultaneously remove the pattern of the film formed of the tantalum-containing material; (G) forming a second resist film on a side of the pattern of the film formed from the chromium-containing material that is away from the transparent substrate, in contact with the pattern of the film formed from the chromium-containing material and the exposed transparent substrate; (H) patterning the second resist film to form a second resist film pattern only on the outer periphery of the transparent substrate, which is an area where the circuit pattern is not formed; (I) removing the pattern of the film formed of the material containing chromium other than the outer periphery portion by dry etching using a chlorine-based gas containing oxygen, using the second resist film pattern as an etching mask, so that the pattern of the film formed of the material containing chromium remains in the outer periphery portion; (J) removing the second resist film pattern; A method for manufacturing a photomask, comprising: 11. The film formed of the silicon-containing material is a phase shift film, the film formed of the material containing chromium is a light-shielding film, The film formed from the material containing tantalum is a hard mask film. 11. The manufacturing method according to claim 10. [Effects of the Invention]

[0034] The film formed from the tantalum-containing material of the photomask blank of the present invention has good resist film adhesion even without HMDS treatment, and can avoid the problem of resist residue that occurs when HMDS treatment is performed.

[0035] Furthermore, since the film formed from the tantalum-containing material of the photomask blank of the present invention is resistant to oxidation in the atmosphere, an oxide layer is resistant to formation on the surface of the film, and the problem of an oxide layer being formed unevenly or locally on the surface of the film, resulting in an uneven etching rate within the film surface, and a decrease in the uniformity of the CD within the film surface, making it unstable, can be avoided.

[0036] Furthermore, the film formed from the tantalum-containing material of the photomask blank of the present invention has a low etching rate in dry etching using an oxygen-containing chlorine-based gas, and by thinning the film formed from the tantalum-containing material, the resist film formed in contact with the film formed from the tantalum-containing material can be thinned.

[0037] Furthermore, the photomask blank of the present invention has high resolution, and when a photomask is produced using the photomask blank of the present invention, a thin resist film can be formed with good adhesion on top of a film formed from a material containing tantalum, and the aspect ratio can be made low even for resist film patterns with narrow line widths. This makes it possible to avoid the problem of the resist film pattern collapsing due to impact with the developer or impact with pure water during rinsing in the development step of forming the resist film pattern.

[0038] Therefore, the photomask blank of the present invention can satisfactorily form an assist pattern with a narrow line width as an assist pattern for a line pattern formed in a circuit pattern. In particular, in the case of a photomask blank having a film formed of a silicon-containing material between a transparent substrate and a film formed of a chromium-containing material, particularly in the case of a phase shift mask blank in which the film formed of the silicon-containing material is a phase shift film, an assist pattern with a line width of, for example, about 40 nm, or even about 36 nm, can be satisfactorily formed, and a photomask having a circuit pattern with high CD uniformity and few defects can be obtained. [Brief explanation of the drawings]

[0039] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a first embodiment of the photomask blank of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing an example of a second embodiment of the photomask blank of the present invention. [Figure 3] FIG. 2 is a cross-sectional view showing an example of a third embodiment of the photomask blank of the present invention. [Figure 4] FIG. 2 is a cross-sectional view showing an example of a fourth embodiment of the photomask blank of the present invention. [Figure 5] 1 is a cross-sectional view showing an example of a first embodiment of a photomask of the present invention. [Figure 6] FIG. 2 is a cross-sectional view showing an example of a second embodiment of the photomask of the present invention. [Figure 7] 1(A) to 1(F) are cross-sectional views illustrating the steps of producing a photomask of the first embodiment from a photomask blank of the first embodiment or the third embodiment. [Figure 8] 1(A) to 1(J) are cross-sectional views illustrating the steps of producing a photomask of the second embodiment from a photomask blank of the second embodiment or the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0040] The present invention will be described in more detail below.

[0041] [Photomask blank] The photomask blank of the present invention comprises a transparent substrate, a film formed of a chromium-containing material, and a film formed of a tantalum-containing material. The film formed of the chromium-containing material is formed on the transparent substrate directly or via another film. Another film may be formed between the film formed of the chromium-containing material and the film formed of the tantalum-containing material, but the film formed of the tantalum-containing material is preferably formed in contact with the film formed of the chromium-containing material.

[0042] The exposure light to which the photomask blank and photomask of the present invention are subjected is not particularly limited, but is preferably, for example, light having a wavelength of 250 nm or less, particularly light having a wavelength of 200 nm or less, such as an ArF excimer laser (wavelength: 193 nm) or an F2 laser (wavelength: 157 nm).

[0043] The present invention will be described below with reference to the drawings. The same components will be denoted by the same reference numerals and duplicate descriptions will be omitted. The drawings may be enlarged or reduced for convenience, and the dimensional ratios of the components may not necessarily be the same as those in reality.

[0044] 1 is a cross-sectional view showing an example of a first embodiment of the photomask blank of the present invention. This photomask blank 101 has a transparent substrate 1 and a film 3 made of a chromium-containing material formed on the transparent substrate 1 in contact with the transparent substrate 1, and a film 4 made of a tantalum-containing material formed on the film 3 made of the chromium-containing material. The photomask blank of the first embodiment has a film made of a chromium-containing material and a film made of a tantalum-containing material formed in this order from the transparent substrate side on the transparent substrate.

[0045] The photomask blank of the present invention preferably further comprises a film formed of a silicon-containing material between the transparent substrate and the film formed of a chromium-containing material. The photomask blank of the present invention may comprise a transparent substrate, a film formed of a silicon-containing material, a film formed of a chromium-containing material, and a film formed of a tantalum-containing material. The film formed of the silicon-containing material is formed on the transparent substrate directly or via another film. Furthermore, another film may be formed between the film formed of the silicon-containing material and the film formed of the chromium-containing material, but the film formed of the silicon-containing material is preferably formed in contact with the film formed of the chromium-containing material.

[0046] 2 is a cross-sectional view showing an example of a second embodiment of the photomask blank of the present invention. This photomask blank 102 has, on a transparent substrate 1, a film 2 formed of a silicon-containing material and formed in contact with the transparent substrate 1, a film 3 formed of a chromium-containing material and formed in contact with the film 2 formed of the silicon-containing material, and a film 4 formed of a tantalum-containing material and formed in contact with the film 3 formed of the chromium-containing material. The photomask blank of the second embodiment has, formed on a transparent substrate, in this order from the transparent substrate side, a film formed of a silicon-containing material, a film formed of a chromium-containing material, and a film formed of a tantalum-containing material.

[0047] The photomask blank of the present invention may further comprise a resist film in contact with the side of the film formed from a material containing tantalum that is remote from the transparent substrate.

[0048] 3 is a cross-sectional view showing an example of a third embodiment of the photomask blank of the present invention. This photomask blank 103 has, on a transparent substrate 1, a film 3 made of a chromium-containing material formed in contact with the transparent substrate 1, a film 4 made of a tantalum-containing material formed in contact with the film 3 made of the chromium-containing material, and a resist film 5 formed in contact with the film 4 made of the tantalum-containing material. The photomask blank of the third embodiment has, formed on a transparent substrate in this order from the transparent substrate side, a film made of a chromium-containing material, a film made of a tantalum-containing material, and a resist film.

[0049] 4 is a cross-sectional view showing an example of a fourth embodiment of the photomask blank of the present invention. This photomask blank 104 has, on a transparent substrate 1, a film 2 formed of a silicon-containing material and formed in contact with the transparent substrate 1, a film 3 formed of a chromium-containing material and formed in contact with the film 2 formed of the silicon-containing material, a film 4 formed of a tantalum-containing material and formed in contact with the film 3 formed of the chromium-containing material, and a resist film 5 formed in contact with the film 4 formed of the tantalum-containing material. The photomask blank of the fourth embodiment has, formed on a transparent substrate in this order from the transparent substrate side, a film formed of a silicon-containing material, a film formed of a chromium-containing material, a film formed of a tantalum-containing material, and a resist film.

[0050] [Transparent substrate] The transparent substrate is not particularly limited in material or size, but a substrate that is transparent to exposure light and is used in a transmission type photomask blank and a transmission type photomask, specifically a quartz substrate such as a synthetic quartz substrate, is suitable. A suitable transparent substrate is, for example, a substrate called a 6025 substrate, which is 6 inches square and 0.25 inches thick as specified in the SEMI standard. In the SI unit system, a 6025 substrate is usually expressed as a substrate that is 152 mm square and 6.35 mm thick.

[0051] [Films made of silicon-containing materials] A film formed of a material containing silicon (Si) may be composed of a single layer or multiple layers (e.g., 2 to 5 layers), and each layer constituting the single layer or multiple layers may have a single composition or a gradient composition.

[0052] The film formed from a silicon-containing material is preferably formed from a material that is resistant to dry etching using a chlorine-based gas containing oxygen and can be removed by dry etching using a fluorine-based gas.

[0053] In the present invention, typical examples of dry etching using a fluorine-based gas include dry etching using a fluorine-containing gas such as CF4 gas or SF6 gas as an etching gas. Furthermore, typical examples of dry etching using a chlorine-based gas containing oxygen include dry etching using a mixed gas of chlorine gas (Cl2 gas) and oxygen gas (O2 gas). A suitable mixed gas of chlorine gas and oxygen gas is a gas in which 10 to 25% by volume of oxygen gas is mixed with chlorine gas.

[0054] The silicon-containing material is preferably a material containing silicon but not a transition metal, or a material containing silicon and a transition metal other than chromium (Me) but not chromium (Cr). Examples of silicon-containing materials that do not contain a transition metal include elemental silicon (Si) or silicon compounds containing silicon and one or more selected from oxygen (O), nitrogen (N), and carbon (C). Examples of such silicon compounds include silicon (Si), silicon and oxygen (SiO), silicon and nitrogen (SiN), silicon, oxygen, and nitrogen (SiON), silicon and carbon (SiC), silicon, oxygen, and carbon (SiOC), silicon, nitrogen, and carbon (SiNC), and silicon, oxygen, nitrogen, and carbon (SiONC).

[0055] On the other hand, examples of film materials containing a transition metal (Me) other than chromium and silicon but not containing chromium include transition metal (Me) silicon compounds containing a transition metal (Me) and silicon (Si), or transition metal (Me) silicon compounds containing a transition metal (Me), silicon (Si), and one or more selected from oxygen (O), nitrogen (N), and carbon (C). Examples of such transition metal (Me) silicon compounds include a material consisting of a transition metal and silicon (MeSi), a material consisting of a transition metal, silicon, and oxygen (MeSiO), a material consisting of a transition metal, silicon, and nitrogen (MeSiN), a material consisting of a transition metal, silicon, oxygen, and nitrogen (MeSiON), a material consisting of a transition metal, silicon, and carbon (MeSiC), a material consisting of a transition metal, silicon, oxygen, and carbon (MeSiOC), a material consisting of a transition metal, silicon, nitrogen, and carbon (MeSiNC), and a material consisting of a transition metal, silicon, oxygen, nitrogen, and carbon (MeSiONC).

[0056] The transition metal (Me) other than chromium is preferably one or more selected from molybdenum (Mo), tungsten (W), tantalum (Ta), titanium (Ti), zirconium (Zr), and hafnium (Hf), with molybdenum being particularly preferred from the viewpoint of processability by dry etching. Note that the material of the film formed from a silicon-containing material may contain hydrogen (H) or the like.

[0057] The thickness of the film formed from the silicon-containing material is preferably 50 nm or more, more preferably 60 nm or more, and is preferably 90 nm or less, more preferably 85 nm or less.

[0058] As the film formed of a silicon-containing material, a photomask blank such as a transmission type photomask blank and an optical film used in a photomask such as a transmission type photomask, particularly a phase shift film, are suitable. When the film formed of a silicon-containing material is a phase shift film, the photomask blank is a phase shift mask blank, and a phase shift mask having a phase shift film pattern is manufactured from the phase shift mask blank. When the phase shift film is a halftone phase shift film, the phase shift mask blank and the phase shift mask are halftone phase shift mask blank and halftone phase shift mask, respectively.

[0059] When the film formed of a silicon-containing material is a phase shift film, the phase difference of the phase shift film with respect to the exposure light is preferably 175 degrees or more and 185 degrees or less. Furthermore, when the film formed of a silicon-containing material is a phase shift film, the transmittance of the phase shift film with respect to the exposure light is preferably 4% or more, more preferably 6% or more, and also preferably 50% or less, more preferably 30% or less. However, a transmittance of 6% or more and 30% or less is more preferable, since this enhances the resolution and depth of focus of the transfer pattern due to the phase shift effect depending on the exposure conditions. When the film formed of a silicon-containing material is a phase shift film, the thickness of the phase shift film is preferably 50 nm or more, more preferably 60 nm or more, and also preferably 90 nm or less, more preferably 85 nm or less, from the viewpoint of keeping the phase difference and transmittance within a predetermined range.

[0060] [Films formed from chromium-containing materials] A film formed from a material containing chromium (Cr) may be composed of a single layer or multiple layers (e.g., 2 to 5 layers), and each layer constituting the single layer or multiple layers may have a single composition or a gradient composition.

[0061] The film formed from a material containing chromium is preferably formed from 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 containing oxygen.

[0062] The chromium-containing material is preferably a material that does not contain silicon (Si). Furthermore, the chromium-containing material is preferably a material that does not contain tantalum (Ta). Examples of the chromium-containing material include elemental chromium (Cr) and chromium compounds containing chromium and one or more selected from oxygen (O), nitrogen (N), and carbon (C). Examples of such chromium compounds include a material made of chromium (Cr), a material made of chromium and oxygen (CrO), a material made of chromium and nitrogen (CrN), a material made of chromium, oxygen, and nitrogen (CrON), a material made of chromium and carbon (CrC), a material made of chromium, oxygen, and carbon (CrOC), a material made of chromium, nitrogen, and carbon (CrNC), and a material made of chromium, oxygen, nitrogen, and carbon (CrONC). The chromium-containing material is particularly preferably a material made of chromium, oxygen, and nitrogen (CrON) or a material made of chromium, oxygen, nitrogen, and carbon (CrONC).

[0063] The thickness of the film formed from a material containing chromium is preferably 86 nm or less, more preferably 80 nm or less, and even more preferably 70 nm or less, and is preferably 30 nm or more, and more preferably 32 nm or more.

[0064] If the film made of a material containing chromium is too thick, the clear time will be long in dry etching using a chlorine-based gas containing oxygen.As will be described later, when a film made of a material containing tantalum is used as an etching mask to dry-etch a film made of a material containing chromium using a chlorine-based gas containing oxygen, the film made of a material containing tantalum will also be gradually etched by dry etching using a chlorine-based gas containing oxygen.If the film made of a material containing tantalum is lost, pinhole defects will occur in the film made of a material containing chromium.

[0065] Therefore, depending on the thickness of the film formed from the chromium-containing material, the film formed from the tantalum-containing material also needs to be at least a certain thickness, but in order to reduce the thickness of the resist film formed in contact with the film formed from the tantalum-containing material, it is preferable that the film formed from the tantalum-containing material be thin, and it is also preferable that the film formed from the chromium-containing material be thin. From this perspective, the thickness of the film formed from the chromium-containing material is preferably 80 nm or less, more preferably 70 nm or less.

[0066] As a film formed of a material containing chromium, an optical film, particularly a light-shielding film, used in a photomask blank such as a transmission type photomask blank and a photomask such as a transmission type photomask is suitable.

[0067] When the film formed from a silicon-containing material is a phase shift film and the film formed from a chromium-containing material is a light-shielding film, particularly when used as a photomask, and the light-shielding film is left as a light-shielding portion (light-shielding film pattern) on the outer peripheral edge of the transparent substrate, which is an area where the circuit pattern of the phase shift film is not formed, the optical density (OD) of the phase shift film and the light-shielding film combined with respect to the exposure light is set to a predetermined optical density (e.g., greater than 2, particularly 2.5 or more), and it is preferable that the optical density of the phase shift film and the light-shielding film combined with respect to the exposure light is 3 or more.

[0068] For example, when the phase shift film has a transmittance of 6% to 30% (optical density of 0.53 to 1.22) for the exposure light, the optical density of the light-shielding film for the exposure light needs to be 1.78 or more in order to make the combined optical density of the phase shift film and the light-shielding film at least 3. Therefore, the thickness of the light-shielding film is preferably 30 nm or more, more preferably 32 nm or more.

[0069] [Films formed from materials containing tantalum] A film formed from a material containing tantalum (Ta) may be composed of a single layer or multiple layers (e.g., 2 to 5 layers), and each layer constituting the single layer or multiple layers may have a single composition or a gradient composition.

[0070] The film made of the material containing tantalum is preferably made of a material that is resistant to dry etching using a chlorine-based gas containing oxygen and can be removed by dry etching using a fluorine-based gas.If the film made of the material containing tantalum is made of a material that can be removed by dry etching using a fluorine-based gas, when the film made of the material containing silicon is etched by dry etching using a fluorine-based gas to form a pattern of the film made of the material containing silicon, the pattern of the film made of the material containing tantalum can be removed at the same time.

[0071] A film formed from a material containing tantalum is usually a film that comes into contact with a resist film, and when a photomask blank is cleaned before forming a resist film in photomask manufacturing, it is a film that comes into contact with a cleaning solution. Therefore, it is required to have high adhesion to the resist film and high chemical resistance to the cleaning solution. Furthermore, a film formed from a material containing tantalum is usually the film located furthest from the transparent substrate among the films in a photomask blank. Therefore, it is required to have low reflectance with respect to light used for inspections such as defect inspection of the photomask blank.

[0072] In the present invention, the tantalum-containing material of the film formed from a tantalum-containing material is a material containing tantalum and oxygen (O) or oxygen (O) and nitrogen (N) (a material containing tantalum and oxygen, or a material containing tantalum, oxygen, and nitrogen), and is a material that does not contain silicon (Si). Furthermore, in the present invention, the tantalum-containing material of the film formed from a tantalum-containing material is preferably a material that does not contain chromium (Cr). Examples of materials that contain tantalum and oxygen or oxygen and nitrogen but do not contain silicon include tantalum oxide and tantalum oxynitride, specifically, a material composed of tantalum and oxygen (TaO) and a material composed of tantalum, oxygen, and nitrogen (TaON). ​​In the present invention, the tantalum-containing material of the film formed from a tantalum-containing material may further contain boron (B).

[0073] When a film formed of a tantalum-containing material is composed of multiple layers, each of the layers is formed of a tantalum-containing material. When a film formed of a tantalum-containing material is composed of multiple layers, the tantalum-containing material forming one or more of the layers may be a material containing tantalum and oxygen (O) or oxygen (O) and nitrogen (N) and not containing silicon (Si). In this case, the tantalum-containing material forming the other layers may be elemental tantalum (Ta) or a material composed of tantalum and nitrogen (TaN). When a film formed of a tantalum-containing material is composed of multiple layers, it is preferable that all of the tantalum-containing materials forming each layer be a material containing tantalum and oxygen (O) or oxygen (O) and nitrogen (N) and not containing silicon (Si).

[0074] Materials that contain tantalum but do not contain silicon, particularly materials composed of tantalum and oxygen (TaO) and materials composed of tantalum, oxygen, and nitrogen (TaON), are less likely to form hydrophilic hydroxyl groups (OH groups) on their surfaces than materials that contain silicon. Films formed from materials that contain tantalum but do not contain silicon have good adhesion to resist films even without HMDS treatment, and the problem of resist residue that occurs when HMDS treatment is performed on films formed from materials that contain silicon can be avoided.

[0075] Materials containing tantalum and oxygen, particularly materials composed of tantalum and oxygen (TaO) and materials composed of tantalum, oxygen, and nitrogen (TaON), are more chemically stable in the atmosphere, less likely to react with oxygen in the atmosphere, and less likely to form an oxide layer on the surface of the film than materials containing tantalum but not oxygen, such as elemental tantalum (Ta) or materials composed of tantalum and nitrogen (TaN). Therefore, films formed from materials containing tantalum and oxygen have a uniform etching rate within the film surface during etching, and maintain good CD uniformity within the film surface, thereby avoiding the problem of uneven or localized formation of an oxide layer on the surface of the film, which results in an uneven etching rate within the film surface and reduced CD uniformity and instability within the film surface.

[0076] In the tantalum-containing material of the film formed from the tantalum-containing material, particularly in the tantalum-containing material forming the single layer when the film formed from the tantalum-containing material is a single layer, or in the tantalum-containing material forming at least the layer furthest from the transparent substrate when the film formed from the tantalum-containing material is composed of multiple layers, preferably in the tantalum-containing material forming two or more layers that constitute the multiple layers, and more preferably in the tantalum-containing material forming all layers that constitute the multiple layers, it is preferable that the tantalum, oxygen, and nitrogen contents each satisfy the following content ranges.

[0077] <Range of tantalum, oxygen and nitrogen content> Tantalum content: preferably 40 atomic % or more, more preferably 42 atomic % or more, and preferably 80 atomic % or less, more preferably 74 atomic % or less Oxygen content: preferably 5 atomic % or more, more preferably 10 atomic % or more, and preferably 50 atomic % or less, more preferably 45 atomic % or less Nitrogen content (if nitrogen is contained): preferably 50 atomic % or less, more preferably 40 atomic % or less

[0078] When a film made of a material containing tantalum is used as an etching mask to process a film made of a material containing chromium by dry etching using a chlorine-based gas containing oxygen, the film made of the material containing tantalum is also gradually etched by dry etching using a chlorine-based gas containing oxygen.If the film made of the material containing tantalum is lost, pinhole defects will occur in the film made of the material containing chromium.

[0079] Therefore, in dry etching using an oxygen-containing chlorine-based gas, it is preferable that the etching rate of a film formed from a tantalum-containing material is sufficiently lower than the etching rate of a film formed from a chromium-containing material. The ratio of the etching rate of a film formed from a tantalum-containing material when dry etching using an oxygen-containing chlorine-based gas under a certain set of conditions to the etching rate of a film formed from a chromium-containing material when dry etching using an oxygen-containing chlorine-based gas under a certain set of conditions (the same conditions) is preferably 50 or more, more preferably 100 or more. This ratio is not particularly limited, but is usually 3000 or less.

[0080] Materials containing tantalum and oxygen, particularly materials consisting of tantalum and oxygen (TaO) and materials consisting of tantalum, oxygen, and nitrogen (TaON), have higher resistance to dry etching using chlorine-based gases containing oxygen and a lower etching rate in dry etching using chlorine-based gases containing oxygen than materials containing tantalum but not oxygen, such as elemental tantalum (Ta) or materials consisting of tantalum and nitrogen (TaN).As a result, the thickness of films formed from materials containing tantalum and oxygen can be reduced.

[0081] The thickness of the film formed from a material containing tantalum (the thickness of the single layer if it is composed of a single layer, or the total thickness of all layers if it is composed of multiple layers) is preferably 15 nm or less, more preferably 12 nm or less, and is also preferably 0.5 nm or more, more preferably 1 nm or more, even more preferably 4 nm or more, and particularly preferably 6 nm or more.

[0082] Furthermore, when the film formed of a tantalum-containing material is composed of multiple layers, the thickness of the layer farthest from the transparent substrate is preferably 0.5 nm or more, more preferably 1 nm or more, even more preferably 2 nm or more, and particularly preferably 4 nm or more. Furthermore, in the layers constituting the multiple layers, the total thickness of the layers satisfying the above ranges of tantalum, oxygen, and nitrogen contents is preferably 0.5 nm or more, more preferably 1 nm or more, even more preferably 2 nm or more, and particularly preferably 4 nm or more, and is preferably 15 nm or less, more preferably 12 nm or less.

[0083] If a film made of a material containing tantalum is too thick, the clear time in dry etching using a fluorine-based gas will be long. As will be described later, when a film made of a material containing tantalum is dry-etched using a fluorine-based gas using a resist film pattern as an etching mask, the resist film will also be gradually etched by dry etching using the fluorine-based gas. If the resist film disappears, pinhole defects will occur in the film made of a material containing tantalum.

[0084] Therefore, depending on the thickness of the film formed from the tantalum-containing material, the resist film also needs to have a certain thickness or more, but in order to reduce the thickness of the resist film formed on and in contact with the film formed from the tantalum-containing material, it is preferable that the film formed from the tantalum-containing material is thin, and if the film formed from the tantalum-containing material is thick, the resist film cannot be made thin, making it impossible to obtain high resolution. From this perspective, the thickness of the film formed from the tantalum-containing material is preferably 15 nm or less, more preferably 12 nm or less.

[0085] On the other hand, if the thickness of the film formed from the material containing tantalum is too thin, sufficient inspection sensitivity may not be obtained for the light used in inspections such as defect inspection of photomask blanks, and for example, defects of 100 nm or less may not be detected. From this perspective, the thickness of the film formed from the material containing tantalum is preferably 4 nm or more, particularly 6 nm or more.

[0086] As a film formed of a material containing tantalum, a processing aid film, particularly a hard mask film, used in a photomask blank such as a transmission type photomask blank and a photomask such as a transmission type photomask is suitable.

[0087] [Resist film] The resist film may be an electron beam resist that is written with an electron beam or a photoresist that is written with light, with a chemically amplified resist being particularly preferred. The chemically amplified resist may be either positive or negative, and may, for example, contain a base resin such as a hydroxystyrene-based resin or a (meth)acrylic acid-based resin, and an acid generator, with a crosslinker, a quencher, a surfactant, or the like added as needed. When forming a fine pattern, the thickness of the resist film is preferably 120 nm or less, more preferably 100 nm or less, even more preferably 90 nm or less, and particularly preferably 70 nm or less, from the viewpoint of preventing the resist film pattern from collapsing during the development process and the rinsing process after development. The lower limit of the resist film thickness is not particularly limited as long as the resist film can be formed with a uniform thickness, but is usually 40 nm or more.

[0088] [Method of film formation] The formation of the film (each layer constituting the film) made of a material containing silicon, the film (each layer constituting the film) made of a material containing chromium, and the film (each layer constituting the film) made of a material containing tantalum is not particularly limited, but is preferably formed by a sputtering method because it is easy to control and to form a film with predetermined properties. The sputtering method can be DC sputtering, RF sputtering, or the like, and is not particularly limited.

[0089] When forming a film made of a silicon-containing material, particularly when forming a film made of a material containing silicon but not containing a transition metal, a silicon target can be used as the sputtering target. On the other hand, when forming a film made of a silicon-containing material using a material containing a transition metal other than chromium (Me) and silicon, particularly a material containing a transition metal other than chromium (Me) and silicon but not containing chromium, the sputtering target can be appropriately selected from a target of a transition metal other than chromium (Me), a silicon target, and a target containing a transition metal other than chromium (Me) and silicon but not containing chromium. If necessary, co-sputtering can be performed using two or more targets. For the target containing a transition metal other than chromium (Me) and silicon but not containing chromium, two or more targets with different compositions (some or all of the constituent elements are different, or the constituent elements are the same but the contents are different) can be used.

[0090] When forming a film made of a material containing chromium, particularly when forming a film made of a material containing chromium but not containing either or both of silicon and tantalum, a chromium target can be used as the sputtering target.

[0091] When forming a film made of a material containing tantalum, particularly when the film is made of a material containing tantalum but not silicon or silicon and chromium, a tantalum target can be used as the sputtering target. Also, when forming a film made of a material containing tantalum with a material containing tantalum and boron, a (TaB) target made of tantalum and boron can be used as the sputtering target.

[0092] The power input to the sputtering target can be set appropriately depending on the size of the sputtering target, cooling efficiency, ease of control of film formation, etc., and is usually 0.1 to 10 W / cm as the power per area of ​​the sputtering surface of the sputtering target. 2As the sputtering gas, a rare gas such as helium gas (He gas), neon gas (Ne gas), or argon gas (Ar gas) is used, and when a film is formed using only the element of the target, only a rare gas may be used as the sputtering gas.

[0093] When the film is formed from a material containing one or more light elements selected from oxygen (O), nitrogen (N), carbon (C), and hydrogen (H), reactive sputtering is preferred. In reactive sputtering, a rare gas such as helium gas (He gas), neon gas (Ne gas), or argon gas (Ar gas) and a reactive gas are used as sputtering gases.

[0094] Examples of reactive gases that can be used include oxygen gas (O2 gas) when using a material containing oxygen (O); nitrogen gas (N2 gas) when using a material containing nitrogen (N); nitrogen oxide gases such as nitric oxide gas (NO gas), nitrogen dioxide gas (NO2 gas), and nitrous oxide gas (NO gas) when using a material containing oxygen (O) and nitrogen (N); carbon oxide gases such as carbon monoxide gas (CO gas) and carbon dioxide gas (CO2 gas) when using a material containing carbon (C) and oxygen (O); and hydrocarbon gases such as methane gas (CH4 gas) when using a material containing carbon (C) and hydrogen (H).

[0095] In particular, when the film is formed from a material containing oxygen (O) and nitrogen (N), the gas may be appropriately selected from oxygen gas (O gas), nitrogen gas (N gas), and nitric oxide gases such as nitric oxide gas (NO gas), nitrogen dioxide gas (NO gas), and nitrous oxide gas (NO gas), and two or more types of gases may be used as necessary.

[0096] The pressure during film formation may be appropriately set in consideration of film stress, chemical resistance, cleaning resistance, etc., and is preferably 0.01 Pa or more, more preferably 0.03 Pa or more, and preferably 1 Pa or less, more preferably 0.3 Pa or less, to particularly improve chemical resistance. The flow rate of each gas may be appropriately set to obtain the desired composition, and is usually 0.1 to 100 sccm.

[0097] In the manufacturing process of a photomask blank, before forming a resist film, the transparent substrate or the transparent substrate and the film formed on the transparent substrate may be subjected to a heat treatment. The heat treatment method may be infrared heating, resistance heating, or the like, and the treatment conditions are not particularly limited. The heat treatment may be carried out in an oxygen-containing gas atmosphere, such as the air. The concentration of the oxygen-containing gas is not particularly limited, and in the case of oxygen gas (O2 gas), for example, it may be 1 to 100% by volume. The heat treatment temperature is preferably 200°C or higher, more preferably 400°C or higher.

[0098] Furthermore, in the manufacturing process of a photomask blank, before forming a resist film, a film formed on a transparent substrate, particularly a film formed from a material containing chromium, may be subjected to ozone treatment or plasma treatment, and the treatment conditions are not particularly limited. Either treatment can be performed for the purpose of increasing the oxygen concentration in the surface region of the film, and in such cases, the treatment conditions can be appropriately adjusted to achieve a predetermined oxygen concentration. When forming a film by sputtering, the oxygen concentration in the surface region of the film can also be increased by adjusting the ratio of the rare gas in the sputtering gas to an oxygen-containing gas (oxidizing gas) such as oxygen gas (O gas), carbon monoxide gas (CO gas), or carbon dioxide gas (CO gas).

[0099] Furthermore, in the manufacturing process of a photomask blank, a cleaning treatment may be performed before forming a resist film to remove particles present on the surface of the transparent substrate or the film formed on the transparent substrate. Cleaning can be performed using one or both of ultrapure water and functional water, which is ultrapure water containing ozone gas, hydrogen gas, etc. Furthermore, after cleaning with ultrapure water containing a surfactant, further cleaning may be performed using one or both of ultrapure water and functional water. Cleaning can be performed while irradiating with ultrasonic waves as needed, and UV light irradiation can also be combined.

[0100] The method for forming the resist film (applying the resist) is not particularly limited, and known methods such as spin coating can be applied.

[0101] [Photomask] From the photomask blank of the present invention, a photomask having a circuit pattern (photomask pattern) of a film formed from a material containing chromium can be produced. When the circuit pattern (photomask pattern) of a film formed from a material containing chromium is used, the film formed from the material containing chromium is preferably a light-shielding film. In this case, the photomask blank and photomask can be binary mask blanks and binary masks.

[0102] 5 is a cross-sectional view showing an example of the first embodiment of the photomask of the present invention. This photomask 111 has a film pattern (circuit pattern) 3a made of a chromium-containing material formed on a transparent substrate 1 in contact with the transparent substrate 1. The photomask of the first embodiment can be produced from the photomask blank of the first embodiment or the photomask blank of the third embodiment.

[0103] From the photomask blank of the present invention, a photomask having a circuit pattern (photomask pattern) of a film formed from a silicon-containing material can be produced. When having a circuit pattern (photomask pattern) of a film formed from a silicon-containing material, the film formed from the silicon-containing material is preferably a phase shift film such as a halftone phase shift film, and the film formed from the chromium-containing material is preferably a light-shielding film. In this case, the photomask blank and photomask can be a phase shift mask blank such as a halftone phase shift mask blank, and a phase shift mask such as a halftone phase shift mask.

[0104] In particular, from the photomask blank of the present invention, a photomask can be produced in which a pattern (light-shielding portion (light-shielding pattern)) of a film formed of a chromium-containing material is formed in contact with a film formed of a silicon-containing material on a transparent substrate in a portion located on the outer periphery of the transparent substrate, which is a portion where a circuit pattern of the film formed of the silicon-containing material is not formed (i.e., a portion outside the area (effective area) where the circuit pattern is formed).

[0105] 6 is a cross-sectional view showing an example of a second embodiment of the photomask of the present invention. This photomask 112 has, on a transparent substrate 1, a pattern 2a of a film formed of a silicon-containing material that is formed in contact with the transparent substrate 1, and a pattern 3b of a film formed of a chromium-containing material that is formed in contact with the pattern 2a of the film formed of the silicon-containing material in a portion located at the outer periphery of the transparent substrate 1, which is an area where the circuit pattern 2a of the film formed of the silicon-containing material is not formed. The photomask of the second embodiment can be produced from the photomask blank of the second embodiment or the photomask blank of the fourth embodiment.

[0106] [Photomask manufacturing method] The photomask of the first aspect of the present invention can be manufactured, for example, by the method shown below. Figure 7 is a cross-sectional view illustrating the process of manufacturing the photomask of the first aspect from the photomask blank of the first or third aspect.

[0107] In this case, when the photomask blank of the first embodiment is used, first, as shown in Fig. 7(A), a first resist film 5 is formed in contact with the side of the film 4 made of a material containing tantalum of the photomask blank 101 that is away from the transparent substrate 1 (step (A)). When the photomask blank of the third embodiment is used, step (A) can be replaced with a step of preparing a photomask blank 103 (step (A0)).

[0108] The resist film formed in step (A) can be the same as the resist film in the photomask blank of embodiment 3 or 4. The thickness of the resist film formed in step (A) is preferably 120 nm or less, more preferably 100 nm or less, even more preferably 90 nm or less, particularly preferably 70 nm or less, and is usually 40 nm or more.

[0109] Next, as shown in FIG. 7(B), the first resist film 5 is patterned to form a first resist film pattern 5a (step (B)).

[0110] Next, as shown in FIG. 7(C), the film 4 formed from the material containing tantalum is patterned by dry etching using a fluorine-based gas using the first resist film pattern 5a as an etching mask to form a pattern 4a of the film formed from the material containing tantalum (step (C)).

[0111] Next, as shown in Figure 7(D), the first resist film pattern 5a is removed (step (D)). Step (D) may be performed after step (E).

[0112] Next, as shown in FIG. 7(E), the film 3 formed from the material containing chromium is patterned by dry etching using a chlorine-based gas containing oxygen, using the pattern 4a of the film formed from the material containing tantalum as an etching mask, to form a pattern 3a of the film formed from the material containing chromium (step (E)).

[0113] Next, as shown in FIG. 7(F), the pattern 4a of the film formed of a material containing tantalum is removed by dry etching using a fluorine-based gas (step (F1)), thereby obtaining the photomask 111 of the first embodiment.

[0114] The photomask of the second aspect of the present invention can be manufactured, for example, by the method shown below. Figure 8 is a cross-sectional view illustrating the process of manufacturing a photomask of the second aspect from a photomask blank of the second or fourth aspect.

[0115] In this case, when the photomask blank of the second embodiment is used, first, as shown in Fig. 8(A), a first resist film 5 is formed in contact with the side of the film 4 made of a material containing tantalum of the photomask blank 102 that is away from the transparent substrate 1 (step (A)). When the photomask blank of the fourth embodiment is used, step (A) can be replaced with a step of preparing a photomask blank 104 (step (A0)).

[0116] The resist film formed in step (A) can be the same as the resist film in the photomask blank of embodiment 3 or 4. The thickness of the resist film formed in step (A) is preferably 120 nm or less, more preferably 100 nm or less, even more preferably 90 nm or less, particularly preferably 70 nm or less, and is usually 40 nm or more.

[0117] Next, as shown in FIG. 8(B), the first resist film 5 is patterned to form a first resist film pattern 5a (step (B)).

[0118] Next, as shown in FIG. 8(C), the film 4 formed from the material containing tantalum is patterned by dry etching using a fluorine-based gas using the first resist film pattern 5a as an etching mask to form a pattern 4a of the film formed from the material containing tantalum (step (C)).

[0119] Next, as shown in Figure 8(D), the first resist film pattern 5a is removed (step (D)). Step (D) may be performed after step (E).

[0120] Next, as shown in FIG. 8(E), the film 3 formed from the material containing chromium is patterned by dry etching using a chlorine-based gas containing oxygen, using the pattern 4a of the film formed from the material containing tantalum as an etching mask, to form a pattern 3a of the film formed from the material containing chromium (step (E)).

[0121] Next, as shown in FIG. 8(F), using the pattern 3a of the film formed of the material containing chromium as an etching mask, the film 2 formed of the material containing silicon is patterned by dry etching using a fluorine-based gas to form a pattern 2a of the film formed of the material containing silicon including a circuit pattern, and at the same time, the pattern 4a of the film formed of the material containing tantalum is removed (step (F2)).

[0122] By carrying out steps (A) to (F2) and then removing the film pattern 3a formed of the chromium-containing material by dry etching using an oxygen-containing chlorine-based gas, a photomask having a film pattern (circuit pattern) formed on and in contact with the transparent substrate and formed of the silicon-containing material can be obtained. On the other hand, by further carrying out the following steps (G) to (J), a photomask having a film pattern formed of the chromium-containing material in the portion located on the outer periphery of the transparent substrate can be obtained.

[0123] After step (F2), first, as shown in FIG. 8(G), a second resist film 6 is formed on the side of the film pattern 3a formed from a material containing chromium that is away from the transparent substrate, in contact with the film pattern 3a formed from a material containing chromium and the exposed transparent substrate 1 (step (G)).

[0124] The resist film formed in step (G) may be the same as the resist film in the photomask blank of the third or fourth embodiment, or may be a laser writing resist film, etc. The thickness of the resist film formed in step (G) is preferably 200 nm or more, more preferably 300 nm or more, and is preferably 1000 nm or less, more preferably 800 nm or less.

[0125] Next, as shown in Figure 8(H), the second resist film 6 is patterned to form a second resist film pattern 6a only on the outer peripheral edge of the transparent substrate, which is the area where no circuit pattern is formed (area other than the effective area 7) ((H) process).

[0126] Next, as shown in Figure 8(I), the film pattern 3a formed from the chromium-containing material is removed from the area other than the outer periphery (effective area 7) by dry etching using a chlorine-based gas containing oxygen, using the second resist film pattern 6a as an etching mask, so that the film pattern (light-shielding portion) 3b formed from the chromium-containing material remains on the outer periphery of the transparent substrate (step (I)).

[0127] Next, as shown in Figure 8(J), by removing the second resist film pattern 6a (step (J)), a film pattern (light-shielding portion) 3b formed from a material containing chromium is formed at the outer peripheral edge, and a second embodiment of the photomask 112 can be obtained in which a film pattern formed from a material containing chromium is not formed in the effective area 7.

[0128] The photomask of the present invention is particularly effective in photolithography for forming a pattern on a substrate to be processed, the half pitch of which is preferably 50 nm or less, more preferably 30 nm or less, even more preferably 20 nm or less, and particularly preferably 10 nm or less, and is particularly effective in exposure to transfer a pattern onto a photoresist film formed on the substrate to be processed using exposure light having a wavelength of 250 nm or less, particularly 200 nm or less, such as an ArF excimer laser (wavelength: 193 nm) or an F2 laser (wavelength: 157 nm).

[0129] The photomask of the present invention can be used to expose a photomask pattern onto a photoresist film formed on a substrate to be processed, which is the target of exposure of the photomask pattern. In a pattern exposure method using the photomask of the present invention, a photomask manufactured from a photomask blank is used to irradiate exposure light, thereby transferring the photomask pattern onto a photoresist film formed on the substrate to be processed. The exposure light may be irradiated under dry conditions or immersion exposure, and the present invention is particularly suitable for use when exposing a photomask pattern by immersion exposure using a wafer of 300 mm or more as the substrate to be processed. [Example]

[0130] EXAMPLES The present invention will be specifically explained below by showing examples and comparative examples, but the present invention is not limited to the following examples.

[0131] [Examples 1 to 10, Comparative Examples 1 to 6] A photomask blank (halftone phase shift mask blank) was produced by sequentially stacking a phase shift film (halftone phase shift film) made of a silicon-containing material, a light-shielding film made of a chromium-containing material, and a hard mask film made of a tantalum-containing material on a transparent quartz substrate measuring 152 mm square and approximately 6 mm thick.

[0132] First, a molybdenum target and a silicon target were used as targets on a transparent substrate, and sputtering was performed in an atmosphere of argon gas and nitrogen gas as sputtering gases while adjusting the power applied to the targets. This resulted in the formation of a single-layer phase shift film (thickness: 70 nm) made of MoSiN (Mo content: 3 atomic %, Si content: 52 atomic %, N content: 45 atomic %), which has a phase difference of 177 degrees and a transmittance of 6% (optical density: 1.22) for light with a wavelength of 193 nm.

[0133] Next, on the phase shift film, sputtering was performed using a chromium target as the target and argon gas, oxygen gas, and carbon dioxide gas as the sputtering gas, adjusting the power applied to the target and the flow rate of the sputtering gas to form a single-layer light-shielding film (thickness: 40 nm) made of CrOC (Cr content: 60 atomic %, O content: 20 atomic %, C content: 20 atomic %) with a transmittance of 1.4% (optical density: 1.85) for light with a wavelength of 193 nm, as a film formed from a material containing chromium.

[0134] Next, in Examples 1 to 10 and Comparative Examples 3 to 6, sputtering was performed on the light-shielding film using a tantalum target as the target and argon gas and oxygen gas, or argon gas, oxygen gas, and nitrogen gas as the sputtering gas, while adjusting the power applied to the target and the flow rate of the sputtering gas, to form a film made of a material containing tantalum, which was a hard mask film having a single layer structure in Examples 1 to 7 and Comparative Examples 3 to 6, and a two-layer structure consisting of a first layer and a second layer in Examples 8 to 10, thereby obtaining a photomask blank.

[0135] On the other hand, in Comparative Examples 1 and 2, sputtering was performed on the light-shielding film using a silicon target as the target and argon gas and oxygen gas as the sputtering gas, while adjusting the power applied to the target and the flow rate of the sputtering gas, to form a single-layer hard mask film made of silicon oxide (SiO), and a photomask blank was obtained.

[0136] The composition and thickness of each layer of the hard mask film, as well as the thickness of the hard mask film, are shown in Table 1. In Table 1, the second layer is the layer furthest from the transparent substrate. In the examples and comparative examples, the composition of the film (layer) was measured using an X-ray photoelectron spectrometer. The thickness of the film (layer) was measured using an X-ray diffractometer.

[0137] [Table 1]

[0138] [Evaluation 1: Clear time of dry etching of light-shielding film using chlorine-based gas containing oxygen] Using an evaluation sample in which only a light-shielding film (a film made of a material containing chromium) was formed on a transparent substrate in the same manner as in Example 1, the time until the light-shielding film disappeared (clear time) was evaluated by dry etching using a chlorine-based gas containing oxygen. The light-shielding film was etched under the following conditions (condition 1), and the clear time was defined as the time until the end point was detected (time to endpoint). As a result, the clear time was 140 seconds, and the etching rate was 0.286 nm / second.

[0139] <Dry etching conditions using chlorine-based gas containing oxygen (Condition 1)> Equipment: ICP (Inductively Coupled Plasma) method Etching gas: Cl2 gas + O2 gas Gas pressure: 3.0 mTorr (0.40 Pa) ICP power: 350W

[0140] [Evaluation 2: Amount of reduction in hard mask film during dry etching of light-shielding film using chlorine-based gas containing oxygen] Using photomask blanks manufactured in the same manner as in Examples 1 to 10 and Comparative Examples 1 to 6, dry etching using an oxygen-containing chlorine-based gas was performed on the hard mask film (a film formed from a material containing tantalum or a film formed from silicon oxide (SiO)) of the photomask blank under the above-mentioned Condition 1, with the etching time being the clear time of dry etching using an oxygen-containing chlorine-based gas of the light-shielding film (a film formed from a material containing chromium) obtained in Evaluation 1 plus 300% overetching (560 seconds), and the reduction in the hard mask film (thickness) was evaluated. The results are shown in Table 2.

[0141] As shown in Table 2, when the photomask blank of Comparative Example 5 was exposed to dry etching using an oxygen-containing chlorine-based gas for an etching time (560 seconds) in which 300% overetching was added to the clear time of dry etching of the light-shielding film using an oxygen-containing chlorine-based gas, all of the film formed from the tantalum-containing material disappeared.

[0142] The etching rate was calculated from the amount of reduction in the hard mask film, and the ratio of the etching rate of the light-shielding film obtained in Evaluation 1 to the etching rate of the hard mask film was calculated. The results are shown in Table 2.

[0143] As shown in Table 2, the ratio of the etching rate of the light-shielding film to the etching rate of the film formed from a material containing tantalum was low in the photomask blanks of Comparative Examples 4 and 5. This is thought to be because the films formed from a material containing tantalum in the photomask blanks of Comparative Examples 4 and 5 do not contain oxygen, and therefore have a high etching rate in dry etching using a chlorine-based gas containing oxygen, and in particular, the photomask blank of Comparative Example 5 has an even higher etching rate in dry etching using a chlorine-based gas containing oxygen due to its higher nitrogen content.

[0144] [Evaluation 3: Clear time of hard mask film dry etching using fluorine-based gas] Photomask blanks manufactured in the same manner as in Examples 1 to 10 and Comparative Examples 1 to 6 were used to evaluate the time (clear time) until a hard mask film (a film formed of a material containing tantalum or a film formed of silicon oxide (SiO)) disappeared by dry etching using a fluorine-based gas. The hard mask film was etched under the following conditions (condition 2), and the clear time was defined as the time until the end point was detected (time to endpoint). The results are shown in Table 2.

[0145] <Dry etching conditions using fluorine-based gas (condition 2)> Equipment: ICP (Inductively Coupled Plasma) method Etching gas: SF6 gas + He gas Gas pressure: 4.0 mTorr (0.53 Pa) ICP power: 400W

[0146] As shown in Table 2, the clear time of the film formed from the material containing tantalum was long in the photomask blank of Comparative Example 3. This is because the film formed from the material containing tantalum in the photomask blank of Comparative Example 3 was thick. The clear time of the film formed from the material containing tantalum in the photomask blank of Comparative Example 6 was also long. This is thought to be because the oxygen content of the film formed from the material containing tantalum in the photomask blank of Comparative Example 6 was high.

[0147] [Evaluation 4: Amount of resist film reduction during dry etching of hard mask film using fluorine-based gas] Using photomask blanks manufactured in the same manner as in Examples 1 to 10 and Comparative Examples 1 to 6, the amount of reduction (thickness) of the resist film was evaluated when a hard mask film (a film formed of a material containing tantalum or a film formed of silicon oxide (SiO)) was dry etched using a fluorine-based gas.

[0148] First, a positive chemically amplified electron beam resist was spin-coated on the hard mask film to form a resist film with a thickness of 100 nm. In forming the resist film, only for the photomask blank of Comparative Example 1, the surface of the film formed of silicon oxide (SiO) was subjected to HMDS treatment before the resist film was formed.

[0149] Next, an electron beam lithography system was used to irradiate the substrate with a dose of 100 μC / cm 2 A total of 20 isolated line patterns with a long side of 100,000 nm and a short side of 60 nm were written using a thermal processing device. Next, a thermal treatment (PEB: Post Exposure Bake) was performed at 115°C for 14 minutes. Next, a development process was performed using a puddle developer for 42 seconds to form a resist film pattern.

[0150] Next, using the resist film pattern as an etching mask, dry etching using a fluorine-based gas was performed on the hard mask film of the photomask blank under the above-mentioned Condition 2, with the etching time shown in Table 2 being the clear time of the dry etching using a fluorine-based gas for the hard mask film obtained in Evaluation 3, plus 50% overetching, to form a hard mask film pattern. The thickness of the resist film remaining in the hard mask film pattern was then measured, and the amount of resist film loss was evaluated. The thickness of the resist film was measured using an atomic force microscope (AFM), and the measurement range was a square area of ​​200 nm × 200 nm. The results, along with the etching time, are shown in Table 2.

[0151] Furthermore, from the amount of resist film reduction obtained, we calculated the etching time by adding 50% overetching to the clear time of dry etching the hard mask film using fluorine-based gas, and the thickness of the resist film required to leave a 20 nm thick resist film after dry etching using fluorine-based gas. This thickness is the minimum resist film thickness required for dry etching using fluorine-based gas. If the resist is too thin, the fluorine-based plasma will reach the hard mask film and cause pinhole defects, so here we set the thickness of the resist film pattern remaining after etching to 20 nm. The results are shown in Table 2.

[0152] As shown in Table 2, in the photomask blanks of Comparative Examples 3 and 6, the films formed from materials containing tantalum had long clear times, so the minimum required thickness of the resist film was thick.

[0153] [Table 2]

[0154] [Photomask manufacturing] Photomasks (halftone phase shift masks) were produced using photomask blanks (halftone phase shift mask blanks) produced in the same manner as in Examples 1 to 10 and Comparative Examples 1 to 6.

[0155] First, a positive chemically amplified electron beam resist was spin-coated onto a hard mask film (a film formed of a material containing tantalum or a film formed of silicon oxide (SiO)) to form a first resist film. In forming the resist film, as in Evaluation 4, only for the photomask blank of Comparative Example 1, the surface of the film formed of silicon oxide (SiO) was subjected to HMDS treatment before forming the resist film (step (A)).

[0156] In the manufacture of photomasks used in the evaluation of the CD uniformity of the photomasks (Evaluation 5), which will be described later, resist films with a thickness of 100 nm were formed in all of Examples 1 to 10 and Comparative Examples 1 to 6. Furthermore, in the manufacture of photomasks used in the evaluation of the resolution limit of the photomasks (Evaluation 6) and the evaluation of photomask defects (Evaluation 7), which will be described later, resist films with the thicknesses shown in Table 3 were formed. In Examples 1 to 10 and Comparative Examples 3, 5, and 6, where the required thickness of the resist film shown in Table 2 was 40 nm or more, resist films were formed with the required thickness shown in Table 2. On the other hand, if the resist film thickness was less than 40 nm, it may not be possible to form the resist film with a uniform thickness. Therefore, in Comparative Examples 1, 2, and 4, where the required thickness of the resist film shown in Table 2 was less than 40 nm, resist films were formed with a thickness of 40 nm.

[0157] Next, the first resist film was patterned to form a first resist film pattern (step (B)). Here, different resist film patterns were formed in the manufacture of each of the photomasks used in evaluations 5 to 7.

[0158] In the manufacturing of the photomask used in Evaluation 5, first, an electron beam lithography system was used to irradiate the photomask with a dose of 100 μC / cm 2 In a 12 cm x 12 cm square region along the four sides of the main surface of the substrate, centered at the intersection of the diagonals of the main surface, isolated space patterns with long sides of 100,000 nm and short sides of 200 nm were drawn at 1 cm intervals starting from one vertex of the square region, with 13 rows along one side of the square region and 13 rows perpendicular to that direction, for a total of 169 patterns. Next, a heat treatment (PEB) was performed at 115°C for 14 minutes using a heat treatment device. Next, a development process was performed using a puddle development for 60 seconds to form a resist film pattern.

[0159] In the manufacturing of the photomask used in Evaluation 6, first, an electron beam lithography system was used to irradiate the photomask with a dose of 100 μC / cm 2As a test pattern equivalent to the assist pattern of the line pattern, a total of 200,000 isolated patterns with different short side dimensions, each with a long side of 80 nm and a short side varying in 1 nm increments from 20 nm to 80 nm, were written. Next, a heat treatment (PEB) was performed at 115°C for 14 minutes using a heat treatment device. Next, a development process was performed using a puddle developer for 60 seconds to form a resist film pattern.

[0160] In the manufacturing of the photomask used in Evaluation 7, first, an electron beam lithography system was used to irradiate the photomask with a dose of 100 μC / cm 2 A line and space pattern (space and line widths of 200 nm each) with long sides of 6 cm and short sides of 200 nm was written over the entire 6 cm × 6 cm square area along the four sides of the main surface of the substrate, centered at the intersection of the diagonals of the main surface. Next, a heat treatment (PEB) was performed at 115°C for 14 minutes using a heat treatment device. Next, a development process was performed using a puddle developer for 60 seconds to form a resist film pattern.

[0161] Next, using the resist film pattern as an etching mask, dry etching using a fluorine-based gas was performed on the hard mask film of the photomask blank under the above-mentioned Condition 2, with the etching time being the etching time shown in Table 2, which was obtained by adding 50% overetching to the clear time of dry etching using a fluorine-based gas for the hard mask film obtained in Evaluation 3, to form a hard mask film pattern (Step (C)).

[0162] Next, the resist film pattern was washed with sulfuric acid / hydrogen peroxide (a mixed solution of sulfuric acid and hydrogen peroxide (sulfuric acid:hydrogen peroxide=3:1 (volume ratio)), the same applies to the sulfuric acid / hydrogen peroxide below) and removed (step (D)).

[0163] Next, using the pattern of the hard mask film as an etching mask, dry etching using a chlorine-based gas containing oxygen was carried out under the above-mentioned condition 1, with the etching time being the clear time of dry etching using a chlorine-based gas containing oxygen of the light-shielding film (film formed from a material containing chromium) obtained in Evaluation 1, plus 300% overetching, to form a pattern of the light-shielding film (step (E)).

[0164] Next, using the light-shielding film pattern as an etching mask, dry etching using a fluorine-based gas was performed under the above-mentioned condition 2, with the etching time being the clear time (72 seconds) of the dry etching using a fluorine-based gas of the phase shift film (film formed from a material containing silicon) plus approximately 3% overetching, resulting in an etching time (74 seconds).The phase shift film was patterned to form a phase shift film pattern including a circuit pattern, and at the same time, the hard mask film pattern was removed (step (F2)).

[0165] A laser writing resist was spin-coated on the side of the light-shielding film pattern away from the transparent substrate, in contact with the light-shielding film pattern and the exposed transparent substrate, to form a second resist film (thickness: 360 nm) (step (G)).

[0166] Next, the second resist film was patterned to form a second resist film pattern (step (H)). First, the second resist film was patterned using a laser drawing device, and a pattern was drawn so that the second resist film did not remain in the area where the circuit pattern was formed (effective area), and the second resist film pattern remained only on the outer periphery of the transparent substrate, which was the area where the circuit pattern was not formed. Next, a heat treatment (PEB) was performed at 110°C for 20 minutes using a heat treatment device. Next, a development process was performed using a spray developer for 200 seconds, and a resist film pattern was formed.

[0167] Next, using the second resist film pattern as an etching mask, dry etching using an oxygen-containing chlorine-based gas was carried out under the above-mentioned Condition 1, with an etching time obtained by adding 300% overetching to the clear time of dry etching using an oxygen-containing chlorine-based gas of the light-shielding film obtained in Evaluation 1, so that the light-shielding film pattern remained at the outer peripheral edge portion, and the light-shielding film pattern other than at the outer peripheral edge portion was removed (Step (I)).

[0168] Next, the resist film pattern was washed with sulfuric acid and hydrogen peroxide and removed (step (J)), to obtain a photomask.

[0169] [Evaluation 5: Photomask CD uniformity] The CD uniformity (uniformity of the line width of the pattern) within the film surface of the phase shift film (film formed from a material containing silicon) of the obtained photomask (halftone phase shift mask) was evaluated.

[0170] Using a critical dimension-scanning electron microscope (CD-SEM), the line widths of 169 isolated space patterns in the phase shift film (a film made of a silicon-containing material) of the resulting photomask were measured, and the 3σ (three times the standard deviation) of the 169 line widths was calculated. The results are shown in Table 3.

[0171] As shown in Table 3, the photomasks of Comparative Examples 4 and 5 had large 3σ values ​​and poor CD uniformity within the phase shift film surface. This is thought to be because the tantalum-containing material used in the photomask blanks of Comparative Examples 4 and 5 was a tantalum nitride (TaN) film, which does not contain oxygen and reacts with oxygen in the atmosphere to form TaO nonuniformly or locally on the surface layer away from the transparent substrate. This resulted in a nonuniform etching rate within the film surface during dry etching using a fluorine-based gas, which reduced the CD uniformity within the film surface and, as a result, reduced the CD uniformity within the film surface of the phase shift film.

[0172] [Evaluation 6: Photomask resolution limit] The resolution limit of the phase shift film (film made of a silicon-containing material) of the obtained photomask (halftone phase shift mask) was evaluated.

[0173] Using a photomask visual inspection system, all 200,000 isolated patterns on the phase shift film (a film made of a material containing silicon) of the obtained photomask were evaluated for pattern loss, pattern collapse, and pattern shape defects.An isolated pattern in which the photomask visual inspection system detected either pattern loss, pattern collapse, or pattern shape defects was considered to be defective, and the dimension of the smallest short side in which there were no isolated patterns with detected defects was considered to be the resolution limit.The results are shown in Table 3.

[0174] As shown in Table 3, the photomask of Comparative Example 2 has a wide resolution limit (wide width of the assist pattern that can be formed) and low resolution. This is because the hard mask film of Comparative Example 2 is not a film formed from a material containing tantalum but a film formed from silicon oxide (SiO), and is not subjected to HMDS treatment, resulting in poor adhesion between the hard mask film and the resist film.

[0175] Furthermore, as shown in Table 3, the photomask of Comparative Example 3 had a wide resolution limit (wider assist pattern width that could be formed) and low resolution, although not as wide as Comparative Example 2. This is thought to be because the film formed from the tantalum-containing material of Comparative Example 3 was thick, and the resist film also needed to be thick, so that in the development step of forming the resist film pattern, the resist film pattern with a high aspect ratio collapsed due to impact from the developer or pure water during rinsing.

[0176] Furthermore, as shown in Table 3, the photomask of Comparative Example 6 also had a wide resolution limit (wide assist pattern that could be formed) and low resolution, although not as wide as Comparative Example 2. This is thought to be because the oxygen content of the film formed from the tantalum-containing material of Comparative Example 6 was high, resulting in a low etching rate in dry etching using a fluorine-based gas (long clear time) and a need for a thick resist film. As a result, in the development step of forming the resist film pattern, the resist film pattern, which had a high aspect ratio, collapsed due to impact from the developer or pure water during rinsing.

[0177] [Rating 7: Photomask defects] The resulting photomask (halftone phase shift mask) was evaluated for defects in the pattern of the phase shift film (film made of a silicon-containing material).

[0178] The appearance quality of the obtained photomask was evaluated by counting the number of protrusion defects, chipping defects, and pinhole defects in the pattern of the phase shift film (a film made of a material containing silicon), as well as the number of pin-dot defects on the transparent substrate and the phase shift film, using a photomask appearance inspection device. The results are shown in Table 3.

[0179] As shown in Table 3, the photomask of Comparative Example 1 had a large number of defects. This is because the hard mask film of Comparative Example 1 was a film formed of silicon oxide (SiO) and was subjected to HMDS treatment, so that resist residues on the film formed of silicon oxide (SiO) functioned as an etching mask when the film formed of silicon oxide (SiO) was etched, and portions of the film formed of silicon oxide (SiO) that should have been etched remained unetched. Ultimately, the phase shift film at the positions of the resist residues remained unetched, resulting in defects, particularly pin dot defects, on the transparent substrate or the phase shift film.

[0180] Furthermore, as shown in Table 3, the photomask of Comparative Example 5 had a large number of defects. This is because the film (thickness 15 nm) formed from the material containing tantalum in Comparative Example 5 was completely lost (amount of reduction of 15 nm in Evaluation 2) by dry etching using a chlorine-based gas containing oxygen, as shown in Table 2, and the light-shielding film (film formed from the material containing chromium) was etched in the exposed areas, resulting in defects, particularly chipping defects or pinhole defects in the pattern.

[0181] [Table 3] [Explanation of symbols]

[0182] 1 Transparent substrate 2. Films made of silicon-containing materials 2a Pattern of a film composed of a silicon-containing material 3. Films formed from materials containing chromium 3a Pattern of a film formed from a material containing chromium 3b: Pattern of film made of material containing chromium (light-shielding part) 4. Films formed from materials containing tantalum 4a Pattern of a film formed from a material containing tantalum 5 First resist film 5a First resist film pattern 6 Second resist film 6a Second resist film pattern 7 Effective Area 101, 102, 103, 104 Photomask blanks 111, 112 Photomask

Claims

1. A photomask blank comprising: a transparent substrate; a film formed on the transparent substrate and made of a material containing chromium; and a film formed on the film formed of the material containing chromium and made of a material containing tantalum, the film formed of the tantalum-containing material is composed of a single layer or multiple layers, the thickness of the film formed of the tantalum-containing material is 0.5 nm or more and 15 nm or less; the tantalum-containing material contains tantalum and oxygen or oxygen and nitrogen, and does not contain silicon; the single layer and at least one of the layers constituting the plurality of layers that is the furthest from the transparent substrate are formed from a material containing tantalum having a tantalum content of 40 atomic % or more and 80 atomic % or less, an oxygen content of 5 atomic % or more and 50 atomic % or less, and a nitrogen content of 50 atomic % or less; The layer farthest from the transparent substrate has a thickness of 0.5 nm or more. A photomask blank characterized by:

2. 2. The photomask blank according to claim 1, wherein, when a film formed from the chromium-containing material and a film formed from the tantalum-containing material are dry-etched using a chlorine-based gas containing oxygen, the ratio of the etching rate of the film formed from the chromium-containing material to the etching rate of the film formed from the tantalum-containing material is 50 or more.

3. 2. The photomask blank according to claim 1, wherein the thickness of the film formed from the chromium-containing material is 30 nm or more and 80 nm or less.

4. 4. The photomask blank according to claim 1, further comprising a film formed of a silicon-containing material between the transparent substrate and the film formed of the chromium-containing material.

5. the film formed of the silicon-containing material is a phase shift film, the film formed of the chromium-containing material is a light-shielding film, The film formed of the material containing tantalum is a hard mask film. The photomask blank according to claim 4 .

6. 6. The photomask blank according to claim 5, wherein the phase shift film has a phase difference of 175 degrees or more and 185 degrees or less, a transmittance of 6% or more and 30% or less, and a thickness of 60 nm or more and 85 nm or less with respect to exposure light.

7. 7. The photomask blank according to claim 6, wherein the combined optical density of the light-shielding film and the phase shift film to the exposure light is 3 or more.

8. 2. The photomask blank according to claim 1, further comprising a resist film having a thickness of 40 nm or more and 120 nm or less, in contact with the side of the film formed of the material containing tantalum that is away from the transparent substrate.

9. A method for producing a photomask having a circuit pattern of a film formed of a material containing chromium from the photomask blank according to any one of claims 1 to 3, comprising the steps of: (A) forming a first resist film in contact with a side of the film formed of the tantalum-containing material that is away from the transparent substrate; (B) patterning the first resist film to form a first resist film pattern; (C) patterning the film formed of the material containing tantalum by dry etching using a fluorine-based gas using the first resist film pattern as an etching mask to form a pattern of the film formed of the material containing tantalum; (D) removing the first resist film pattern; (E) patterning the film formed of the chromium-containing material by dry etching using a chlorine-based gas containing oxygen, using the pattern of the film formed of the tantalum-containing material as an etching mask, to form a pattern of the film formed of the chromium-containing material; (F1) removing the pattern of the film formed of the material containing tantalum by dry etching using a fluorine-based gas; A method for manufacturing a photomask, comprising:

10. A method for producing a photomask having a circuit pattern of a film formed of the silicon-containing material from the photomask blank according to claim 4, comprising the steps of: (A) forming a first resist film in contact with a side of the film formed of the tantalum-containing material that is away from the transparent substrate; (B) patterning the first resist film to form a first resist film pattern; (C) patterning the film formed of the material containing tantalum by dry etching using a fluorine-based gas using the first resist film pattern as an etching mask to form a pattern of the film formed of the material containing tantalum; (D) removing the first resist film pattern; (E) patterning the film formed of the chromium-containing material by dry etching using a chlorine-based gas containing oxygen, using the pattern of the film formed of the tantalum-containing material as an etching mask, to form a pattern of the film formed of the chromium-containing material; (F2) patterning the film formed from the material containing silicon by dry etching using a fluorine-based gas, using the pattern of the film formed from the material containing chromium as an etching mask, to form a pattern of the film formed from the material containing silicon, including the circuit pattern, and simultaneously remove the pattern of the film formed from the material containing tantalum; (G) forming a second resist film on a side of the pattern of the film formed from the chromium-containing material that is away from the transparent substrate, in contact with the pattern of the film formed from the chromium-containing material and the exposed transparent substrate; (H) patterning the second resist film to form a second resist film pattern only on the outer periphery of the transparent substrate, which is an area where the circuit pattern is not formed; (I) removing the pattern of the film formed of the material containing chromium other than the outer periphery portion by dry etching using a chlorine-based gas containing oxygen, using the second resist film pattern as an etching mask, so that the pattern of the film formed of the material containing chromium other than the outer periphery portion remains; (J) removing the second resist film pattern; A method for manufacturing a photomask, comprising:

11. the film formed of the silicon-containing material is a phase shift film, the film formed of the chromium-containing material is a light-shielding film, The film formed of the material containing tantalum is a hard mask film. The method according to claim 10 .

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