Mask blank, method of manufacturing a transfer mask, and method of manufacturing a semiconductor device

Abstract

A mask substrate is provided capable of forming fine spatial patterns on a pattern forming thin film. The mask substrate has a structure in which a pattern forming thin film, a first hard mask film, and a second hard mask film are sequentially deposited on the main surface of a substrate; the pattern forming thin film contains at least one element selected from silicon and transition metals; the first hard mask film contains chromium; the second hard mask film contains tantalum; the tantalum in the second hard mask film contains oxygen-unsaturated tantalum; the thickness of the pattern forming thin film is 20 nm or more; the thickness of the first hard mask film is 15 nm or less; and the thickness of the second hard mask film is 10 nm or less.

Description

Methods for manufacturing mask substrates, transfer masks, and semiconductor devices. This invention relates to a mask substrate, a method for manufacturing a mask for transfer printing, and a method for manufacturing a semiconductor device. Regarding the mask substrate used in the manufacture of transfer masks, a technique for constructing a hard mask film is known for the purpose of miniaturizing the pattern formed on the transfer mask. For example, Patent Document 1 describes a light mask substrate on which a light-shielding film and an etch mask film (hard mask film) are sequentially formed on a light-transmitting substrate; the light-shielding film comprises: a light-shielding layer containing at least a transition metal silicate; and a surface anti-reflection layer formed on the light-shielding layer, with a tantalum compound containing at least one of oxygen and nitrogen as the main component; the etch mask film is composed of a chromium compound containing at least one of oxygen and nitrogen. Furthermore, it is described that, "when patterning the etch mask film composed of a chromium compound, the tantalum compound forming the surface anti-reflection layer has higher resistance to oxygen-containing chlorine gases used for dry etching of the etch mask film compared to transition metal silicates. Therefore, over-etching can be performed in a manner that makes the sidewalls of the etch mask film's processing profile substantially vertical." Patent Document 1: Japanese Patent No. 5606028 However, the chromium compounds constituting the hard mask film (etch mask film) are isotropically etched relative to oxygen-containing chlorine gases. Therefore, in etching with a resist film as a mask, when patterning the hard mask film (etch mask film) composed of chromium compounds, it is unavoidable that the etched sidewalls (processed profile sidewalls) recede, causing the opening width (opening size) of the pattern formed on the hard mask film to increase. This becomes a major obstacle to the miniaturization of patterns formed on the patterning film using etching with a patterned hard mask film as a mask. Furthermore, it also becomes a major obstacle to the high integration of semiconductor devices manufactured using a transfer mask incorporating this patterning film. Therefore, the object of the present invention is to provide a method for manufacturing a mask substrate capable of forming fine patterns on a pattern forming thin film and a transfer mask. Furthermore, the object of the present invention is to provide a method for manufacturing a semiconductor device using a transfer mask manufactured by the method for manufacturing a transfer mask. The means for solving the above-mentioned problems in this invention has the following configuration. (Composition 1) A masking substrate having a structure in which a pattern forming thin film, a first hard masking film, and a second hard masking film are sequentially deposited on the main surface of a substrate; the pattern forming thin film contains at least one element selected from silicon and transition metals; the first hard masking film contains chromium; the second hard masking film contains tantalum; the tantalum in the second hard masking film contains oxygen-unsaturated tantalum; the thickness of the pattern forming thin film is 20 nm or more; the thickness of the first hard masking film is 15 nm or less; and the thickness of the second hard masking film is 10 nm or less. (Composition 2) A masking substrate having a structure in which a pattern forming thin film, a first hard masking film, and a second hard masking film are sequentially deposited on the main surface of a substrate; the pattern forming thin film contains at least one element selected from silicon and transition metals; the first hard masking film contains chromium; the second hard masking film contains tantalum and swells in an oxygen-containing gas atmosphere; the thickness of the pattern forming thin film is 20 nm or more; the thickness of the first hard masking film is 15 nm or less; and the thickness of the second hard masking film is 10 nm or less. (Form 3) The masking substrate as in Form 1 or 2, wherein the ratio of oxygen content to tantalum content of the second hard masking film is 1.5 or less. (Form 4) A masking substrate as in any of 1 to 3, wherein the second hard masking film contains the most tantalum among the metal elements and silicon. (Form 5) A masking substrate as in any of 1 to 4, wherein the thickness of the second hard masking film is 1 nm or more. (Form 6) A masking substrate as constituted by any one of 1 to 5, wherein the first hard masking film contains at least one of chromium, oxygen and nitrogen. (Structure 7) A masking substrate as configured in any of 1 to 6, wherein the thickness of the first hard masking film is greater than the thickness of the second hard masking film. (Configuration 8) A masking substrate as configured in any of 1 to 7, wherein the pattern forming film is a light-absorbing film containing tantalum; and a multilayer reflective film is provided between the substrate and the pattern forming film. (Form 9) A masking substrate as in any of Forms 1 to 8, wherein the thin film for pattern forming is a light-shielding film containing silicon. (Construction 10) A method for manufacturing a transfer mask, comprising a method for manufacturing a transfer mask using a mask substrate as described in any of Constructions 1 to 9, comprising: a step of forming a second hard mask pattern on the second hard mask film by dry etching using a resist film having a pattern formed on the second hard mask film as a mask; a step of forming a first hard mask pattern on the first hard mask film by dry etching using an oxygen-containing gas to cause the etched sidewalls of the second hard mask pattern to swell due to oxidation using the second hard mask pattern as a mask; and a step of forming a thin film pattern on the pattern forming thin film by dry etching using the first hard mask pattern as a mask. (Component 11) A method for manufacturing a semiconductor device, comprising an exposure step, wherein a transfer mask manufactured by the method for manufacturing a transfer mask as described in Component 10 is used to transfer the thin film pattern of the transfer mask to a resist film on a substrate for a semiconductor device by photolithography. According to the present invention, a method for manufacturing a mask substrate capable of forming fine patterns on a pattern forming thin film and a transfer mask can be provided, and a method for manufacturing a semiconductor device of a transfer mask manufactured using the method for manufacturing the transfer mask can be provided. Hereinafter, various embodiments of the present invention will be described with reference to the drawings. Furthermore, in each drawing, the same reference numerals will be used to describe the same constituent elements. First Embodiment First, the structure of the mask substrate 1 according to the first embodiment of the present invention will be described with reference to FIG. 1. Next, a method for manufacturing a transfer mask using the mask substrate 1 and a method for manufacturing a semiconductor device will be described. <Mask Substrate 1> FIG. 1 is a cross-sectional view showing the structure of the mask substrate 1 according to the first embodiment of the present invention. The mask substrate 1 shown in FIG. 1 is used to manufacture a transmissive transfer mask. The mask substrate 1 has a structure in which a pattern forming film 11, a first hard mask film 12, and a second hard mask film 13 are sequentially deposited on the main surface S on one side of a light-transmitting substrate 10, starting from the light-transmitting substrate 10 side. Alternatively, the mask substrate 1 may also be configured such that a resist film 14 is deposited on the second hard mask film 13 as needed. Hereinafter, the main components of the mask substrate 1 will be described in detail. [Transparent Substrate 10] The transparent substrate 10 in the first embodiment is made of a material that has good transmittance to the exposure light used in the photolithography process. When using ArF excimer laser light (wavelength: 193nm) as the exposure light, it is acceptable to use a material that has good transmittance to it. Such materials can be synthetic quartz glass, or aluminum silicate glass, soda-lime glass, or low thermal expansion glass (SiO2). 2- TiO 2. Glass, etc.), and other various glass substrates. In particular, quartz substrates are preferably suitable as the masking substrate of the present invention because of their high transparency in ArF excimer laser light or in regions with shorter wavelengths. Furthermore, the exposure process in photolithography mentioned here refers to the exposure process in photolithography using a transmissive transfer mask made from the mask substrate 1. The exposure light mentioned below refers to the exposure light used in this exposure process. As this exposure light, any of ArF excimer laser light (wavelength: 193nm), KrF excimer laser light (wavelength: 248nm), or i-line light (wavelength: 365nm) can be used. However, from the viewpoint of pattern refinement in the exposure process, it is preferable to use ArF excimer laser light as the exposure light. Therefore, an embodiment of using ArF excimer laser light as the exposure light will be described below. [Pattern Forming Thin Film 11] The pattern forming thin film 11 is a light-shielding film for exposure light. This pattern forming thin film 11 may contain at least one element selected from silicon and transition metals. Here, as an example, the pattern forming thin film 11 is formed from a silicon (Si)-containing material. Alternatively, the pattern forming thin film 11 is preferably formed from a nitrogen (N)-containing material in addition to silicon. This pattern forming thin film 11 can be patterned by dry etching using a fluorine-based gas, and can achieve sufficient etching selectivity for the first hard mask film 12 formed from a chromium (Cr)-containing material as described below. Furthermore, the pattern-forming thin film 11 can contain one or more elements selected from metalloid elements, non-metallic elements, and metallic elements, as long as it can be patterned by dry etching using fluorine-based gases. The metalloids, excluding silicon, can be any metalloid, such as boron (B), germanium (Ge), antimony (Sb), and tellurium (Te). The nonmetallic elements, excluding nitrogen (N), can be any nonmetallic element (including halogens and noble gases), such as one or more elements selected from oxygen (O), carbon (C), hydrogen (H), phosphorus (P), sulfur (S), selenium (Se), fluorine (F), helium (He), argon (Ar), krypton (Kr), and xenon (Xe). The metallic elements include molybdenum (Mo), tungsten (W), titanium (Ti), tantalum (Ta), zirconium (Zr), hafnium (Hf), niobium (Nb), vanadium (V), cobalt (Co), chromium (Cr), nickel (Ni), ruthenium (Ru), and tin (Sn). Furthermore, the thickness of the pattern forming film 11 is not particularly limited, but in order to obtain sufficient light shielding for exposure, it can be, for example, 20 nm or more. This ensures the light shielding properties of the pattern forming film 11 during etching and efficiently removes the second hard mask pattern 13P (described later). Additionally, to form fine patterns with high precision, the thickness of the pattern forming film 11 is preferably 70 nm or less, more preferably 60 nm or less, and even more preferably 50 nm or less. [First Hard Mask Film 12] The first hard mask film 12 is preferably made of a material that has sufficient etch resistance in dry etching of the patterning film 11 using a fluorine-based gas. Such a first hard mask film 12 can be made of, for example, a chromium (Cr)-containing material. The first hard mask film 12 made of a chromium (Cr)-containing material can be patterned by dry etching using an oxygen-containing gas. As the chromium-containing material constituting the first hard mask film 12, in addition to chromium metal, materials containing at least one of oxygen, nitrogen, and carbon can be listed. In particular, the first hard mask film 12 is preferably made of at least one of chromium and oxygen and nitrogen, for example, it can be composed of chromium and nitrogen. In this way, by using an oxygen-containing gas as an etchant, the etching rate when etching the first hard mask film 12 can be improved. In addition, the first hard mask film 12 has sufficient etch selectivity between itself and the pattern forming film 11 formed of silicon (Si) material, and can etch away the first hard mask film 12 with almost or no damage to the pattern forming film 11. Furthermore, the first hard mask film 12 has sufficient etching selectivity relative to the second hard mask film 13 formed from the tantalum (Ta)-containing material described below, and can be patterned with the first hard mask film 12 masked by the second hard mask film 13. To form fine patterns, the first hard mask film 12, as described above, may have a film thickness of, for example, less than 15 nm. Furthermore, the film thickness of the first hard mask film 12 is preferably greater than the film thickness of the second hard mask film 13, which will be described below. [Second Hard Mask Film 13] The second hard mask film 13 is preferably made of a material that has sufficient etch resistance and swells in the dry etching process using the first hard mask film 12 containing oxygen gas. Such a second hard mask film 13 can be made of a tantalum (Ta)-containing material. That is, the material of the second hard mask film 13 only needs to be tantalum (Ta)-containing and swell in an oxygen-containing gas atmosphere. The tantalum (Ta)-containing material in the second hard mask film 13 includes oxygen-unsaturated tantalum (Ta). Alternatively, the material constituting the second hard mask film 13 can be said to include incompletely oxidized tantalum (Ta). When fully oxidized, tantalum (Ta) becomes stable tantalum pentoxide (Ta). 2O 5), therefore, it can be said that incompletely oxidized tantalum refers to tantalum in the Ta state. 2O Tantalum in bonding states other than 5-bonds. Therefore, during dry etching using the first hard mask film 12 containing oxygen gas, the tantalum (Ta) contained in the second hard mask film 13 oxidizes, causing the second hard mask film 13 to swell. Thus, the ratio of oxygen content to tantalum (Ta) content in the second hard mask film 13 is preferably 1.5 or less. This ensures that the swelling amount caused by tantalum (Ta) oxidation is sufficient. Furthermore, this swelling amount can be controlled by appropriately adjusting the ratio of oxygen content to tantalum (Ta) content in the second hard mask film 13. More specifically, the ratio of oxygen content to tantalum (Ta) content in the second hard mask film 13 can be adjusted to the desired value by controlling the film formation conditions (the atomic composition ratio of the sputtering target, the type of sputtering gas, the gas flow rate ratio, etc.) during the deposition of the second hard mask film 13. Furthermore, since each film-forming device inherently possesses its own characteristics, the aforementioned film-forming conditions must be adjusted according to the specific film-forming device used. Additionally, the contents of tantalum (Ta) and oxygen (O) can be determined using XPS (X-ray electron spectrometry). In addition to tantalum (Ta), the second hard masking film 13 may also contain at least one of other metallic elements besides tantalum (Ta) and silicon. Even when the second hard masking film 13 contains at least one of other metallic elements besides tantalum (Ta) and silicon, the second hard masking film 13 preferably contains the most tantalum (Ta) among tantalum (Ta), other metallic elements, and silicon. The second hard masking film 13 can also be said to preferably contain the most tantalum besides oxygen. In this way, the swelling amount caused by the oxidation of tantalum (Ta) can be made to a sufficient value. Furthermore, the thickness of the second hard mask film 13 is preferably thinner than the thickness of the first hard mask film 12. Typically, the thickness of the second hard mask film 13 is, for example, 10 nm or less. By setting the thickness of the second hard mask film 13 to be thinner, the thickness of the resist film 14, which serves as the etching mask for the second hard mask film 13, can be reduced, allowing for finer patterns formed on the pattern forming film 11. Furthermore, by making the thickness of the second hard mask film 13 thinner than the thickness of the first hard mask film 12, as described later, when etching the pattern forming film 11 using the first hard mask film 12 as a mask, the second hard mask film 13 can be removed while maintaining the presence of the first hard mask film 12. Additionally, the thickness of the second hard mask film 13 is 1 nm or more. Therefore, during dry etching using the first hard mask film 12 containing oxygen gas, it is possible to achieve a swelling effect where the etched sidewalls of the patterned second hard mask film 13 (second hard mask pattern 13P) are of sufficient size. The etched sidewalls of the second hard mask pattern 13P refer to the sidewalls of the second hard mask pattern in cross-section of the mask substrate 1 with the second hard mask film 13 patterned. In this cross-section, the angle between the sidewalls and the main surface of the substrate is a right angle or approximately a right angle. [Resistant Film 14] The resist film 14 is preferably formed in the mask substrate 1, attached to the surface of the second hard mask film 13. The resist film 14 is, for example, a chemically amplified positive resist, but it is not limited to this as long as it can form a fine pattern. In addition, from the viewpoint of forming a fine pattern due to, for example, photolithography of the resist film 14 and the viewpoint of preventing pattern collapse of the formed resist pattern, the film thickness of the resist film 14 is preferably 80 nm or less. <Manufacturing Method of Transfer Mask> Figures 2A-2C are manufacturing process diagrams (1) of the manufacturing method for a transfer mask using the mask substrate 1 of the first embodiment of the present invention. Figures 3A and 3B are manufacturing process diagrams (2) of the manufacturing method for a transfer mask using the mask substrate 1 of the first embodiment of the present invention. Hereinafter, a method for manufacturing a translucent transfer mask will be described based on these figures. First, prepare a mask substrate 1 with the configuration shown in FIG1. ​​If the mask substrate 1 does not have a resist film 14, the resist film 14 is formed on the upper part of the second hard mask film 13. Alternatively, as shown in FIG1, the mask substrate 1 may also have a resist film 14, in which case the film-forming step of the resist film 14 is not required. [Process (1)] In process (1) shown in FIG. 2A, the resist film 14 of the mask substrate 1 is exposed to draw the pattern to be formed on the patterning film 11. This exposure drawing can be done using electron beams. Then, as needed, the resist film 14 is subjected to predetermined treatments such as PEB (Post Exposure Bake) treatment, development treatment, and post-baking treatment to pattern the resist film 14. The patterned resist film 14 has a spatial pattern 14a, the opening width [W14] of which is, for example, the minimum spatial width. In addition, the spatial pattern in this first embodiment refers to a pattern formed by partially removing the film, including linear patterns and hole-shaped patterns (hole patterns). In addition, the spatial pattern can also be called a removal part pattern. When the spatial pattern is hole-shaped, the opening width [W14] is the diameter of the hole. The same applies in the following description. [Process (2)] In process (2) shown in FIG. 2B, the patterned resist film 14 is used as a mask to etch the second hard mask film 13. At this time, the second hard mask film 13, which is made of tantalum (Ta) material, is patterned by dry etching using fluorine gas as an etchant, and the pattern formed on the resist film 14 is transferred to the second hard mask film 13. In this way, a second hard mask pattern 13P is formed on the second hard mask film 13. Here, the dry etching of tantalum (Ta)-containing materials using fluorine-based gases as etchants exhibits higher anisotropy. Therefore, a spatial pattern 13a with an opening width [W13] approximately the same as that formed on the resist film 14 is formed on the second hard mask pattern 13P. Additionally, during this process, some resist film 14 may remain on the second hard mask pattern 13P. This remaining resist film 14 can be removed by ashing using oxygen or ozone gas, as described later, or it can be removed during the etching of the first hard mask film 12. [Process (3)] In process (3) shown in FIG2C, the first hard mask film 12 is etched using the second hard mask pattern 13P as a mask. At this time, oxygen-containing gas is also used as an etchant to swell the second hard mask pattern 13P. The first hard mask film 12 is patterned by this dry etching to form the first hard mask pattern 12P. When the first hard mask film 12 is made of a chromium (Cr)-containing material, the gas used as the etchant preferably contains chlorine gas in addition to oxygen. In addition, the resist film 14 remaining on the second hard mask pattern 13P can also be removed by ashing with an oxygen-containing etchant. The dry etching process uses oxygen- and chlorine-containing gases as etchants. Although the etching of the first hard mask film 12, which is made of chromium (Cr)-containing material, is not as good as wet etching, it is performed with slight isotropy. Here, in this dry etching, the second hard mask pattern 13P is exposed to oxygen-containing gas, and the tantalum (Ta) contained in the second hard mask pattern 13P is oxidized. This oxidation extends isotropically from the exposed surface of the second hard mask pattern 13P, and the exposed surface of the second hard mask pattern 13P becomes composed of oxide portions 13b. Due to the swelling caused by this oxidation, the opening width [W13] of the spatial pattern 13a formed on the second hard mask pattern 13P becomes the reduced opening width [W13'] due to the swelling of the second hard mask pattern 13P. Furthermore, as mentioned above, when removing the residual resist film 14 by ashing using oxygen or ozone gas, the tantalum (Ta) contained in the second hard mask pattern 13P also oxidizes during this ashing stage, causing the second hard mask pattern 13P to swell. The second embodiment described later is the same. Therefore, a second hard mask pattern 13P, having an opening width [W13'] smaller than the opening width [W14] of the spatial pattern 14a formed on the resist film 14 in step (1), is used as a mask to perform isotropic dry etching of the first hard mask film 12. In this way, a first hard mask pattern 12P is formed on the first hard mask film 12, which is a spatial pattern 12a with a tiny opening width [W12] corresponding to the amount of swelling of the second hard mask pattern 13P, in which side etching is suppressed. [Process (4)] In process (4) shown in FIG. 3A, the first hard mask pattern 12P is used as a mask to etch the pattern forming film 11. At this time, the pattern forming film 11 made of silicon (Si) material is patterned by dry etching using fluorine gas as etchant, forming a film pattern 11P obtained by transferring the first hard mask pattern 12P onto the pattern forming film 11. In addition, during the etching of the pattern forming film 11, it is preferable that the second hard mask pattern 13P remaining on the first hard mask pattern 12P, including the oxide portion 13b, is also etched away by the fluorine gas etchant. Furthermore, the dry etching of silicon (Si)-containing materials using fluorine-based gases as etchants exhibits higher anisotropy. Therefore, on the thin film pattern 11P composed of silicon (Si)-containing materials, a spatial pattern 11a with a fine opening width [W11] is formed, which is approximately the same as the opening width [W12] of the spatial pattern 12a formed on the first hard mask pattern 12P. [Step (5)] In step (5) shown in FIG3B, the first hard mask pattern 12P on the thin film pattern 11P is etched away. At this time, the first hard mask pattern 12P, which is made of chromium (Cr) material, is etched by dry etching using chlorine gas as an etchant. The chlorine gas may also contain oxygen. Thus, a transmissive transfer mask 100 is obtained, which is a thin film pattern 11P formed by patterning the thin film 11 and is disposed on the light-transmitting substrate 10 as a light-shielding pattern. The thin film pattern 11P formed on the transfer mask 100 has a spatial pattern 11a, which has a fine opening width [W11] of a amount corresponding to the swelling amount of the second hard mask pattern 13P, in which side etching is suppressed. Based on the above description, a transfer mask 100 with a thin film pattern 11P having a finer spatial pattern 11a can be obtained. <Method for Manufacturing Semiconductor Devices> The method for manufacturing semiconductor devices is characterized in that a transmissive transfer mask 100 manufactured by the method for manufacturing transfer masks described above is used to expose and transfer a thin film pattern 11P onto a resist film on a substrate for semiconductor devices. This method for manufacturing semiconductor devices is carried out as follows. First, a substrate for forming a semiconductor element is prepared. This substrate may be, for example, a semiconductor substrate, a substrate having a semiconductor thin film, or a substrate with a finely processed film formed on its upper part. A resist film is formed on the prepared substrate, and the resist film is patterned using a transfer mask 100 for exposure, transferring the thin film pattern 11P formed on the transfer mask 100 onto the resist film. At this time, as described above, any of the following can be used as the exposure light: ArF excimer laser light (wavelength: 193 nm), KrF excimer laser light (wavelength: 248 nm), or i-line light (wavelength: 365 nm). However, from the viewpoint of pattern refinement, it is preferable to use ArF excimer laser light as the exposure light. Following the above, the resist film with the 11P thin film pattern transferred on it is developed to form a resist pattern. This resist pattern is then used as a mask to perform etching or impurity introduction on the surface of the substrate. After processing, the resist pattern is removed. By changing the transfer mask 100 and simultaneously performing the above-mentioned photolithography on the substrate, the necessary processing is carried out to complete the semiconductor device. In the manufacturing of the semiconductor device described above, a highly integrated semiconductor device can be obtained by using a transfer mask 100 with a fine spatial pattern 11a manufactured by the transfer mask manufacturing method described above. 《Second Embodiment》 First, the structure of the mask substrate 2 in the second embodiment will be explained with reference to FIG4. Then, the manufacturing method of the transfer mask using the mask substrate 2 and the manufacturing method of the semiconductor device will be explained. <Mask Substrate 2> Figure 4 is a cross-sectional view showing the structure of the mask substrate 2 according to the second embodiment of the present invention. The mask substrate 2 shown in the figure is a prototype of a reflective transfer mask (hereinafter referred to as a reflective mask) for EUV lithography, which uses extreme ultraviolet (EUV) light as the exposure light. The mask substrate 2 is constructed by sequentially depositing multiple layers of reflective film 21, protective film 22, pattern forming film 11', first hard mask film 12, and second hard mask film 13 on the main surface S of one side of the substrate 20, starting from the substrate 20 side. Alternatively, the mask substrate 2 may also be constructed by depositing a resist film 14 on the second hard mask film 13 as needed. Hereinafter, the main components of the mask substrate 2 will be described in detail. [Substrate 20] To prevent deformation of the transfer pattern caused by heat during exposure (EUV exposure) using a reflective mask formed by processing the mask substrate 2, substrate 20 is preferably made of low-expansion glass. For example, SiO2 can be used as a low-expansion glass. 2-TiO 2-series glass, multi-component glass ceramics, etc. In addition, the transfer pattern is a pattern formed by processing the pattern forming film 11' described later. [Multilayer Reflective Film 21] The multilayer reflective film 21 is a film disposed on the main surface S of the substrate 20 between the substrate 20 and the pattern forming film 11', which reflects EUV light used for exposure with high reflectivity. This multilayer reflective film 21 enables the reflective transfer mask formed using the mask substrate 2 to reflect EUV light, and is a multilayer film formed by periodically stacking layers of elements with different refractive indices as the main components. Typically, a multilayer reflective film 21 is formed by alternately depositing thin films (high refractive index layers) of light elements or their compounds as high refractive index materials and thin films (low refractive index layers) of heavy elements or their compounds as low refractive index materials for about 40 to 60 periods. For example, as a multilayer reflective film 21 for EUV light with wavelengths of 13 nm to 14 nm, a Mo / Si periodic laminated film is preferably used, in which Mo films and Si films are alternately deposited for about 40 to 60 periods. Alternatively, the uppermost high refractive index layer of the multilayer reflective film 21 can also be formed of silicon (Si). [Protective Film 22] Protective film 22 is a film provided to protect the multilayer reflective film 21 from etching and cleaning during the processing of the mask substrate 2 to manufacture a reflective mask for EUV lithography. The protective film 22 is provided on the multilayer reflective film 21 in contact with the multilayer reflective film 21 or in between other films, and can be a single-layer structure or a laminated structure. The protective film 22 is preferably made of ruthenium (Ru). The material of the protective film 22 can be a Ru metal monomer, or a Ru alloy containing at least one metal selected from titanium (Ti), niobium (Nb), molybdenum (Mo), zirconium (Zr), yttrium (Y), rhodium (Rh), boron (B), lanthanum (La), cobalt (Co), and rhenium (Re). The presence of nitrogen is also acceptable. Alternatively, the protective film 22 can also be made of silicon-based materials such as silicon (Si), materials containing silicon (Si) and oxygen (O), materials containing silicon (Si) and nitrogen (N), or materials containing silicon (Si), oxygen (O), and nitrogen (N). [Pattern Forming Thin Film 11'] The pattern forming thin film 11' is a light-absorbing film for exposure. Such a pattern forming thin film 11' can be made of a tantalum (Ta)-containing material. Furthermore, the pattern forming thin film 11' can be a single-layer structure or a laminated structure as illustrated. In the case of a laminated structure, an example is a laminated structure with a first thin film 11-1 and a second thin film 11-2 sequentially formed from the substrate 20 side. The material of the pattern forming thin film 11' is not particularly limited, but the materials of the first thin film 11-1 and the second thin film 11-2 can be, for example, the materials described below. The first thin film 11-1 is composed of an etchable material that has good light absorption for exposure and a high selectivity relative to the protective film 22. Such a first thin film 11-1 is, for example, composed of a material containing at least tantalum (Ta) and nitrogen (N). Furthermore, in a reflective transfer mask substrate, from the viewpoint of smoothness and flatness, the crystalline state of the light-absorbing film preferably has an amorphous or microcrystalline structure. By adding boron (B), silicon (Si), and / or germanium (Ge) to tantalum (Ta), an amorphous structure can be easily obtained, improving smoothness. Moreover, if nitrogen (N) and / or oxygen (O) are added to tantalum (Ta), the stability over time can be improved due to increased resistance to oxidation. Based on the above, the first thin film 11-1 can be, for example, TaN, TaON, TaBN, TaBON, TaCN, TaCON, TaBCN, or TaBOCN. The second thin film 11-2 is preferably made of an etchable material that has good light absorption for exposure and high selectivity for the first hard mask film 12. Such a second thin film 11-2 can be made of a material containing at least tantalum (Ta) and oxygen (O), and for example, TaBO can be used considering smoothness and flatness. This allows for patterning of the first hard mask film 12, formed from a chromium (Cr)-containing material as described below, with sufficient etch selectivity. Furthermore, the first thin film 11-1 can be dry-etched using a fluorine-based gas or a substantially oxygen-free chlorine-based gas. The second thin film 11-2 can be dry-etched using a fluorine-based gas or a substantially oxygen-free chlorine-based gas, but preferably a fluorine-based gas with a higher etching rate is used for etching. Furthermore, the pattern forming film 11' has a thickness of, for example, 20 nm or more, to achieve sufficient absorption of exposure light (EUV light). Additionally, to reduce shading effects, the thickness of the pattern forming film 11' is preferably 70 nm or less, more preferably 60 nm or less, and even more preferably 50 nm or less. [First Hard Mask Film 12] The first hard mask film 12 is the same as the first hard mask film 12 of the mask substrate 1 illustrated in FIG. 1 in the first embodiment. That is, the first hard mask film 12 is preferably made of a material that has sufficient etch resistance in dry etching of the pattern forming film 11' using fluorine-based gases. Such a first hard mask film 12 can be made of a material containing chromium (Cr), for example, it can be made of chromium containing at least one of oxygen, nitrogen and carbon. In addition, more detailed descriptions of the first hard mask film 12 are omitted as they are repeated in the description of the first embodiment. [Second Hard Mask Film 13] The second hard mask film 13 is the same as the second hard mask film 13 of the mask substrate 1 illustrated in FIG. 1 in the first embodiment. That is, the second hard mask film 13 is made of a material that has sufficient etch resistance and swells during dry etching using the first hard mask film 12 containing oxygen gas. Preferably, the second hard mask film 13 is made of a material containing tantalum (Ta). Furthermore, more detailed descriptions of the second hard mask film 13 that are repeated in the description of the first embodiment are omitted. [Resistant film 14] The resistant film 14 is the same as the resistant film 14 of the masking substrate 1 described in FIG1 in the first embodiment. The detailed configuration here is omitted as it is repeated in the description of the first embodiment. <Manufacturing Method of Transfer Mask> Figures 5A to 5C are manufacturing process diagrams (1) of a method for manufacturing a transfer mask using the mask substrate 2 of the second embodiment of the present invention. Figures 6A and 6B are manufacturing process diagrams (2) of a method for manufacturing a transfer mask using the mask substrate 2 of the second embodiment of the present invention. The steps of the manufacturing method shown in these figures are basically the same as those of the manufacturing method described in the first embodiment using Figures 2A to 2C and Figures 3A and 3B. Hereinafter, a method for manufacturing a reflective transfer mask will be described based on these figures. First, prepare a masking substrate 2 with the configuration shown in Figure 4. If the masking substrate 2 does not have a resist film 14, the resist film 14 is formed on top of the second hard masking film 13. Alternatively, as shown in Figure 4, the masking substrate 2 may also have a resist film 14, in which case the film-forming step of the resist film 14 is not required. [Process (1) to (3)] Next, the processes (1) to (3) shown in FIG5A to FIG5C are performed in the same order as the processes (1) to (3) shown in FIG2A to FIG2C in the first embodiment, so their detailed description is omitted here. Furthermore, particularly in process (3), the second hard mask pattern 13P is used as a mask, and the first hard mask film 12 containing chromium (Cr) is patterned by isotropic dry etching using an oxygen-containing gas. In this dry etching, it is preferable to use a gas containing chlorine in addition to oxygen. In this dry etching, the second hard mask pattern 13P is exposed to oxygen-containing gas, and the tantalum (Ta) contained in the second hard mask pattern 13P is oxidized. The oxidation extends isotropically from the exposed surface of the second hard mask pattern 13P, which is composed of oxide portions 13b. Due to the swelling caused by such oxidation, the opening width [W13] of the space pattern 13a formed on the second hard mask pattern 13P becomes the reduced opening width [W13'] due to the swelling of the second hard mask pattern 13P. Therefore, a second hard mask pattern 13P, having an opening width [W13'] smaller than the opening width [W14] of the spatial pattern 14a formed on the resist film 14 in step (1) of FIG. 5A, is used as a mask to perform isotropic dry etching of the first hard mask film 12. Thereby, a first hard mask pattern 12P is formed on the first hard mask film 12, which is a spatial pattern 12a with a fine opening width [W12] whose side etching is suppressed by an amount corresponding to the swelling amount of the second hard mask pattern 13P. [Step (4)] In step (4) shown in FIG6A, the second film 11-2 in the pattern forming film 11' is etched using the first hard mask pattern 12P as a mask. At this time, the second film 11-2, which is composed of a material containing at least tantalum (Ta) and oxygen (O), is patterned by dry etching using a fluorine-based gas as an etchant, and the pattern formed on the first hard mask pattern 12P is transferred to the second film 11-2. In addition, it is preferable that during the etching of the second film 11-2, the second hard mask pattern 13P remaining on the first hard mask pattern 12P, including the oxide portion 13b, is also etched away by the fluorine-based gas etchant. Furthermore, the anisotropy of dry etching of tantalum (Ta)-containing materials using fluorine-based gases as etchants is relatively high. Therefore, on the second thin film 11-2 composed of at least tantalum (Ta) and oxygen (O), a spatial pattern 11a' with a fine opening width [W11'] is formed, which is approximately the same as the opening width [W12] of the spatial pattern 12a formed on the first hard mask pattern 12P. [Step (5)] In step (5) shown in FIG. 6B, the first hard mask pattern 12P is further used as a mask to etch the first thin film 11-1 in the pattern forming thin film 11'. At this time, the first thin film 11-1, which is made of a material containing at least tantalum (Ta) and nitrogen (N), is patterned by dry etching using chlorine gas as an etchant, and the pattern formed on the first hard mask pattern 12P is transferred to the first thin film 11-1. In addition, during the etching of the first thin film 11-1, it is preferable that the first hard mask pattern 12P remaining on the second thin film 11-2 is etched away by the chlorine gas etchant. Furthermore, dry etching of tantalum (Ta)-containing materials using chlorine-based gases as etchants exhibits higher anisotropy. Therefore, on the first thin film 11-1 composed of at least tantalum (Ta) and nitrogen (N), a spatial pattern 11a' with a fine opening width [W11'] is formed, having a similar degree to the opening width [W12] of the spatial pattern 12a formed on the first hard mask pattern 12P. In addition, in dry etching using chlorine-based gases as etchants, the protective film 22 containing ruthenium (Ru) acts as an etching barrier, thus protecting the multilayer reflective film 21. Thus, a reflective transfer mask 200 is obtained, on which a thin film pattern 11P' as a light-absorbing pattern is provided on the substrate 20 through multiple layers of reflective film 21 and protective film 22. The thin film pattern 11P' formed on the transfer mask 200 has a spatial pattern 11a', which has a fine opening width [W11'] of a amount corresponding to the swelling amount of the second hard mask pattern 13P, and the side etching is suppressed. In this way, a reflective transfer mask 200 with a thin film pattern 11P' having a finer spatial pattern 11a' can be obtained. <Method for Manufacturing Semiconductor Devices> The method for manufacturing semiconductor devices is characterized in that a reflective transfer mask 200 manufactured by the method for manufacturing transfer masks described above is used to expose and transfer a thin film pattern 11P' onto a resist film on a substrate for semiconductor devices. This method for manufacturing semiconductor devices is carried out as follows. First, a substrate for forming a semiconductor element is prepared. This substrate may be, for example, a semiconductor substrate, a substrate with a semiconductor thin film, or a substrate with a finely processed film formed on its upper part. A resist film is formed on the prepared substrate, and the resist film is exposed using a transfer mask 200 to transfer the thin film pattern 11P' formed on the transfer mask 200 onto the resist film. At this time, EUV light is used as the exposure light, and the exposure light (EUV light) reflected by the transfer mask 200 is irradiated onto the resist film. Following the above, the resist film with the thin film pattern 11P' transferred on it is developed to form a resist pattern. This resist pattern is then used as a mask to perform etching or impurity introduction on the surface of the substrate. After processing, the resist pattern is removed. By changing the transfer mask 200 and simultaneously performing the above-mentioned photolithography on the substrate, the necessary processing is carried out to complete the semiconductor device. In the manufacturing of the semiconductor device described above, a highly integrated semiconductor device can be obtained by using a transfer mask 200 with a fine spatial pattern 11a' manufactured by the transfer mask manufacturing method described above. Next, Examples 1-3 to which the present invention is applicable, and Comparative Examples 1 and 2 thereof, will be described. The results shown in these examples and comparative examples are obtained by simulation based on prior knowledge of the etching rates of each film of the mask substrate relative to each etching gas and the swelling rate of the tantalum-containing film (second hard mask film) in an oxygen atmosphere. FIG7 is a diagram illustrating the examples and comparative examples. FIG7 shows the structure of the mask substrate in the examples and comparative examples, and the opening width of the spatial patterns formed on each film of the mask substrate. Hereinafter, the comparative examples and examples will be described with reference to FIG7 and FIG1 to FIG6A, FIG6B and other illustrations. <Comparative Example 1> [Fabrication of Mask Substrate] The mask substrate used in the manufacture of a translucent transfer mask was fabricated in the following manner. First, silicon nitride (SiNx) is sputtered to form a patterning thin film 11 with a thickness of 62 nm on a transparent substrate 10 made of synthetic quartz glass with a thickness of approximately 6.35 mm. Chromium nitride (CrNx) is sputtered to form a first hard mask film 12 with a thickness of 5 nm on the patterning thin film 11. A chemically amplified positive resist is formed on the first hard mask film 12 without forming a second hard mask film 13, and a resist film 14 with a thickness of 60 nm is formed as the mask substrate of Comparative Example 1. [Fabrication of the Transfer Mask (Refer to Figures 7A and 8A to 8D)] A transmissive transfer mask was fabricated using the mask substrate of Comparative Example 1. Figures 8A to 8D are manufacturing process diagrams showing the manufacturing method of the transfer mask of Comparative Example 1. Hereinafter, the fabrication steps of the transfer mask using the mask substrate of Comparative Example 1 will be described with reference to Figures 8A to 8D. First, as shown in process (1) of Figure 8A, a spatial pattern 14a with an opening width [W14] = 34 nm is formed on the resist film 14 by photolithography. This opening width [W14] is the minimum spatial width caused by photolithography currently used to manufacture a transmissive transfer mask. Next, as shown in step (2) of Figure 8B, the patterned resist film 14 is used as a mask to etch the first hard mask film 12. At this time, oxygen-containing chlorine gas (Cl...) is used... 2+O 2) Dry etching, using chromium nitride (CrNx) as the etchant, patterns the first hard mask film 12 to form a first hard mask pattern 12P having a spatial pattern 12a. In this etching, the first hard mask film 12 is etched isotropically. Therefore, the opening width [W12] of the spatial pattern 12a formed on the first hard mask pattern 12P is larger than the opening width [W14] of the resist film 14, with an opening width [W12] = 38 nm. Furthermore, the resist film 14 remaining on the first hard mask pattern 12P is removed by ashing with an oxygen-containing etchant. Next, as shown in step (3) of Figure 8C, the first hard mask pattern 12P is used as a mask to etch the pattern forming film 11. At this time, by using fluorine-based gas (SF6) Dry etching using 6+He as the etchant is used to pattern a silicon nitride (SiNx) patterning film 11 to form a thin film pattern 11P with a spatial pattern 11a. In this etching, the silicon nitride (SiNx) patterning film 11 is well anisotropically etched. Therefore, the opening width [W11] of the spatial pattern 11a formed on the thin film pattern 11P will be the same size as the opening width [W12] of the first hard mask film 12, and the opening width [W11] = 40 nm. Then, as shown in step (4) of Figure 8D, oxygen-containing chlorine gas (Cl) is used. 2+O 2) Dry etching, using silicon nitride (SiNx) as an etchant, removes the first hard mask pattern 12P remaining on the thin film pattern 11P. In this way, a transfer mask for Comparative Example 1, which uses the thin film pattern 11P made of silicon nitride (SiNx) as a light-shielding pattern, is obtained on the light-transmitting substrate 10. <Comparative Example 2> [Fabrication of Mask Substrate (Refer to Figures 1 and 7)] As the mask substrate 1 of Comparative Example 2, a mask substrate used in the manufacture of a transmissive transfer mask was produced. Here, in the manufacturing steps of the mask substrate of Comparative Example 1, after the first hard mask film 12 is formed and before the film resist film 14 is formed, a tantalum (Ta) target is used, and argon (Ar) and oxygen (O) are used. 2) Reactive sputtering was performed in a mixed gas atmosphere to sputter tantalum oxide (TaOx) as the second hard mask film 13 with a film thickness of 3 nm. This produced a mask substrate 1 of Comparative Example 2 with the structure illustrated in FIG1. ​​The oxygen (O) content to tantalum (Ta) content ratio (O / Ta) of the second hard mask film 13 is 2.5. That is, the tantalum (Ta) in the second hard mask film 13 is in an oxygen-saturated state. In other words, the second hard mask film 13 is essentially composed of tantalum pentoxide (TaOx). 2O 5) constitutes. [Preparation of Transfer Mask] The method for manufacturing a transmissive transfer mask using the mask substrate 1 of Comparative Example 2 will be described. The process of manufacturing the transfer mask in Comparative Example 2 is the same as that shown in Figures 2A to 2C, 3A, and 3B, except that the second hard mask film 13 does not swell. Therefore, it will be described with reference to Figures 2A to 2C, 3A, and 3B. First, a spatial pattern 14a with an opening width [W14] = 34 nm is formed on the resist film 14 by photolithography. This opening width [W14] is the minimum spatial width caused by photolithography currently used to manufacture transmissive transfer masks. Next, the patterned resist film 14 is used as a mask to etch the second hard mask film 13. At this time, fluorine-based gases (SF6) are used... Dry etching using 6+He as the etchant is used to pattern the second hard mask film 13 made of tantalum oxide (TaOx) to form a second hard mask pattern 13P having a spatial pattern 13a. In this etching, the second hard mask film 13 made of tantalum oxide (TaOx) is well anisotropically etched. Therefore, the opening width [W13] of the spatial pattern 13a formed in the second hard mask pattern 13P will be the same size as the opening width [W14] of the resist film 14, and the opening width [W13] = 34 nm. Next, the first hard mask film 12 is etched using the second hard mask pattern 13P as a mask. At this time, oxychlorine gas (Cl) is used... 2+O 2) Dry etching as an etchant, patterning the first hard mask film 12 composed of chromium nitride (CrNx) to form a first hard mask pattern 12P having a spatial pattern 12a. In this etching, even if the second hard mask pattern 13P is exposed to oxychlorine gas (Cl... 2+O In step 2), the tantalum (Ta) contained in the second hard mask pattern 13P will not be oxidized, and the second hard mask pattern 13P will not swell. Therefore, after the first hard mask film 12 is etched, the opening width [W13] of the spatial pattern 13a of the second hard mask pattern 13P will remain at 34 nm. Furthermore, in this etching process, the first hard mask film 12, composed of chromium nitride (CrNx), is etched isotropically. Therefore, the opening width [W12] of the spatial pattern 12a formed on the first hard mask pattern 12P is larger than the opening width [W13] of the spatial pattern 13a, with an opening width [W12] = 38 nm. Additionally, the resist film 14 remaining on the second hard mask pattern 13P is removed by ashing with an oxygen-containing etchant. Next, the first hard mask pattern 12P is used as a mask to etch the pattern-forming thin film 11. At this time, fluorine-based gases (SF6) are used... Dry etching using 6+He as the etchant is used to pattern the silicon nitride (SiNx) patterning film 11 to form a thin film pattern 11P with a spatial pattern 11a. In this etching, the silicon nitride (SiNx) patterning film 11 is well anisotropically etched. Therefore, the opening width [W11] of the spatial pattern 11a formed on the thin film pattern 11P is the same size as the opening width [W12] of the spatial pattern 12a in the first hard mask pattern 12P, and the opening width [W11] = 40 nm. Then, by using oxychlorine gas (Cl...) 2+O 2) Dry etching, as an etchant, is used to remove the first hard mask pattern 12P remaining on the thin film pattern 11P. In this way, a transfer mask 100 of Comparative Example 2, which has a thin film pattern 11P made of silicon nitride (SiNx) provided on a light-transmitting substrate 10 as a light-shielding pattern, is obtained. <Example 1> [Fabrication of Mask Substrate (Refer to Figures 1 and 7)] The mask substrate 1 of Example 1 is a mask substrate used in the manufacture of a transmissive transfer mask. Here, in the manufacturing steps of the mask substrate of Comparative Example 1, after the first hard mask film 12 is formed and before the film resist film 14 is formed, a tantalum (Ta) target is used, and argon (Ar) and oxygen (O) are used. 2) Reactive sputtering is performed in a mixed gas atmosphere to sputter tantalum oxide (TaOx) as the second hard mask film 13 with a film thickness of 3 nm. This produces a mask substrate 1 of Example 1 having the configuration illustrated in FIG1. ​​The oxygen (O) content to tantalum (Ta) content ratio (O / Ta) of the second hard mask film 13 is 1.3, and the tantalum (Ta) in the second hard mask film 13 is oxygen-unsaturated. [Preparation of the transfer mask (refer to Figures 2A to 2C and Figures 3A and 3B)] The method for manufacturing a transmissive transfer mask using the mask substrate 1 of Example 1 will be described with reference to Figures 2A to 2C and Figures 3A and 3B. First, as shown in process (1) of Figure 2A, a spatial pattern 14a with an opening width [W14] = 34 nm is formed on the resist film 14 by photolithography. This opening width [W14] is the minimum spatial width caused by photolithography currently used to manufacture a transmissive transfer mask. Next, as shown in step (2) of Figure 2B, the patterned resist film 14 is used as a mask to etch the second hard mask film 13. At this time, fluorine-based gas (SF6) is used... Dry etching using 6+He as the etchant is used to pattern the second hard mask film 13 composed of tantalum oxide (TaOx) to form a second hard mask pattern 13P having a spatial pattern 13a. In this etching, the second hard mask film 13 composed of tantalum oxide (TaOx) is well anisotropically etched. Therefore, the opening width [W13] of the spatial pattern 13a formed in the second hard mask pattern 13P will be the same size as the opening width [W14] of the resist film 14, and the opening width [W13] = 34 nm. Next, as shown in step (3) of Figure 2C, the first hard mask film 12 is etched using the second hard mask pattern 13P as a mask. At this time, oxychlorine gas (Cl) is used... 2+O 2) Dry etching as an etchant, patterning the first hard mask film 12 composed of chromium nitride (CrNx) to form a first hard mask pattern 12P having a spatial pattern 12a. In this etching, the second hard mask pattern 13P is exposed to oxygen-containing chlorine gas (Cl). 2+O In step 2), the second hard mask pattern 13P swells due to the oxidation of tantalum (Ta) contained in it. That is, the second hard mask film 13 in Example 1 contains oxygen-unsaturated tantalum. Then, through the oxidation of tantalum, the opening width [W13] of the spatial pattern 13a of the second hard mask pattern 13P becomes the reduced opening width [W13'] = 30nm due to the swelling of the second hard mask pattern 13P. Furthermore, in this etching process, the first hard mask film 12, composed of chromium nitride (CrNx), is etched isotropically. Therefore, the opening width [W12] of the spatial pattern 12a formed on the first hard mask pattern 12P is larger than the opening width [W13'] of the reduced spatial pattern 13a, with an opening width [W12] = 34 nm. Additionally, the resist film 14 remaining on the second hard mask pattern 13P is removed by ashing with an oxygen-containing etchant. Next, as shown in step (4) of Figure 3A, the first hard mask pattern 12P is used as a mask to etch the pattern forming film 11. At this time, by using fluorine-based gas (SF6) Dry etching using 6+He as the etchant is used to pattern a silicon nitride (SiNx) patterning film 11 to form a thin film pattern 11P with a spatial pattern 11a. In this etching, the silicon nitride (SiNx) patterning film 11 is effectively etched anisotropically. Therefore, the opening width [W11] of the spatial pattern 11a formed on the thin film pattern 11P is of the same size as the opening width [W12] of the spatial pattern 12a in the first hard mask pattern 12P, with an opening width [W11] = 36 nm. Then, as shown in step (5) of Figure 3B, by using oxygen-containing chlorine gas (Cl... 2+O 2) Dry etching, as an etchant, removes the first hard mask pattern 12P remaining on the thin film pattern 11P. Thereby, a transfer mask 100 of Example 1 is obtained, in which a thin film pattern 11P composed of silicon nitride (SiNx) is provided as a light-shielding pattern on a light-transmitting substrate 10. <Example 2> [Fabrication of Mask Substrate (Refer to Figures 1 and 7)] As the mask substrate 1 of Example 2, a mask substrate used in the manufacture of a transmissive transfer mask was produced. Here, in the manufacturing steps of the mask substrate of Comparative Example 1, after the first hard mask film 12 is formed and before the film resist film 14 is formed, a tantalum (Ta) target is used, and argon (Ar) and nitrogen (N) are used. 2) Reactive sputtering is performed in a mixed gas atmosphere to sputter tantalum nitride (TaNx) as the second hard mask film 13 with a film thickness of 3 nm. This produces a mask substrate 1 of Example 2 with the configuration illustrated in FIG1. ​​The oxygen (O) content to tantalum (Ta) content ratio O / Ta of the second hard mask film 13 is 0, and the tantalum (Ta) in the second hard mask film 13 is unsaturated with oxygen. [Fabrication of the Transfer Mask (Refer to Figures 2A to 2C and Figures 3A and 3B)] A transmissive transfer mask is fabricated using the mask substrate 1 of Example 2. Here, the same steps as in the fabrication of the transfer mask of Example 1 are performed to obtain the transfer mask 100 of Example 1, which has a thin film pattern 11P formed by patterning a silicon nitride (SiNx) patterning thin film 11 on a light-transmitting substrate 10. The opening width of the spatial pattern formed in each process is shown in Figure 7. In addition, in this Example 2, the second hard mask pattern 13P is also used as a mask. When etching the first hard mask film 12, the second hard mask pattern 13P swells due to the oxidation of tantalum (Ta) contained in the second hard mask pattern 13P. That is, the second hard mask film 13 contains oxygen-unsaturated tantalum. <Example 3> [Fabrication of Mask Substrate (Refer to Figures 4 and 7)] The mask substrate of Example 3 is a mask substrate 2 used in the manufacture of a reflective transfer mask, which is fabricated in the following manner. First, a multilayer reflective film 21 and a protective film 22 made of ruthenium-niobium alloy (RuNb) are formed on a substrate 20 made of low-expansion glass with a thickness of approximately 6.35 mm. The multilayer reflective film 21 and the protective film 22 are used as a base film. The total thickness of the base film is 289 nm. On the substrate film, tantalum nitride (TaNx) is sputtered to form a first thin film 11-1 as a patterning thin film 11', and then tantalum oxide (TaOx) is sputtered to form a second thin film 11-2. The total thickness of the first thin film 11-1 and the second thin film 11-2 is 62 nm. On the patterning film 11', a first hard mask film 12 is sputtered to form chromium carbonitride (CrOCN) with a thickness of 6 nm. Furthermore, a tantalum (Ta) target is used, and argon (Ar) and nitrogen (N) are sputtered... 2) Reactive sputtering is performed in a mixed gas atmosphere to sputter a second hard mask film 13 composed of tantalum nitride (TaNx) with a thickness of 3 nm on the first hard mask film 12. A chemically amplified positive resist, serving as a resist film 14, is then formed on the second hard mask film 13 with a thickness of 40 nm, resulting in the mask substrate 2 of Example 3. Furthermore, the oxygen (O) content to tantalum (Ta) content ratio O / Ta of the second hard mask film 13 is 0, and the tantalum (Ta) in the second hard mask film 13 is unsaturated with oxygen. [Preparation of the transfer mask (refer to Figures 5A to 5C and Figures 6A and 6B)] The method for manufacturing a reflective transfer mask using the mask substrate 2 of Example 3 will be described with reference to Figures 5A to 5C and Figures 6A and 6B. First, as shown in process (1) of Figure 5A, a spatial pattern 14a with an opening width [W14] = 26 nm is formed on the resist film 14 by photolithography. This opening width [W14] is the minimum spatial width currently achieved by photolithography used to manufacture reflective transfer masks. Next, as shown in step (2) of Figure 5B, the patterned resist film 14 is used as a mask to etch the second hard mask film 13. At this time, fluorine-based gas (SF6) is used... Dry etching using 6+He as the etchant is used to pattern the second hard mask film 13 composed of tantalum nitride (TaNx) to form a second hard mask pattern 13P having a spatial pattern 13a. In this etching, the second hard mask film 13 composed of tantalum nitride (TaNx) is well anisotropically etched. Therefore, the opening width [W13] of the spatial pattern 13a formed in the second hard mask pattern 13P will be the same size as the opening width [W14] of the spatial pattern 14a formed in the resist film 14, and the opening width [W13] = 26 nm. Next, as shown in step (3) of Figure 5C, the first hard mask film 12 is etched using the second hard mask pattern 13P as a mask. At this time, oxychlorine gas (Cl) is used... 2+O 2) Dry etching as an etchant, patterning the first hard mask film 12 composed of chromium carbonitride (CrOCN) to form a first hard mask pattern 12P having a spatial pattern 12a. In this etching, the second hard mask pattern 13P is exposed to oxychlorine gas (Cl). 2+O 2) In this process, the second hard mask pattern 13P swells due to the oxidation of tantalum (Ta) contained in it. That is, the second hard mask film 13 in Example 3 contains oxygen-unsaturated tantalum. Then, through the oxidation of the tantalum, the opening width [W13] of the spatial pattern 13a of the second hard mask pattern 13P becomes the reduced opening width [W13'] = 20nm due to the swelling of the second hard mask pattern 13P. Furthermore, in this etching process, the first hard mask film 12, composed of chromium carbonitride (CrOCN), is etched isotropically. Therefore, the opening width [W12] of the spatial pattern 12a formed on the first hard mask pattern 12P is larger than the opening width [W13'] of the reduced spatial pattern 13a, with an opening width [W12] = 24 nm. Additionally, the resist film 14 remaining on the second hard mask pattern 13P is removed by ashing with an oxygen-containing etchant. Next, as shown in step (4) of Figure 6A, the second thin film 11-2 of the pattern forming thin film 11' is etched using the first hard mask pattern 12P as a mask. At this time, fluorine-based gas (SF6) is used... Dry etching using 6+He as the etchant is used to pattern the second thin film 11-2, which is a pattern forming thin film 11' made of tantalum oxide (TaOx). In this etching, the second thin film 11-2 made of tantalum oxide (TaOx) is well etched anisotropically. Furthermore, during the etching of the second thin film 11-2, the second hard mask pattern 13P, including the oxide portion 13b, is also removed. Next, as shown in step (5) of Figure 6B, the first hard mask pattern 12P is used as a mask to etch the first thin film 11-1 of the pattern forming thin film 11'. At this time, chlorine gas (Cl) is used... 2) Dry etching, using tantalum nitride (TaNx) as the etchant, is used to pattern the first thin film 11-1 of the pattern-forming thin film 11'. In this etching, the first thin film 11-1 of tantalum nitride (TaNx) is well anisotropically etched. In this way, a thin film pattern 11P' is formed by patterning the first thin film 11-1 and the second thin film 11-2, which are used for patterning thin films 11'. The opening width [W11'] of the spatial pattern 11a' formed on the thin film pattern 11P' is the same size as the opening width [W12] of the first hard mask film 12, and the opening width [W11'] = 26 nm. In addition, the first hard mask pattern 12P is removed by this etching. Based on the above description, the reflective transfer mask 200 of Embodiment 3 was obtained. The reflective transfer mask 200 of Embodiment 3 includes a thin film pattern 11P' formed by patterning a pattern forming thin film 11' composed of a laminated structure of tantalum nitride (TaNx) and tantalum oxide (TaOx) on a substrate 20 as a light-absorbing pattern. <Evaluation Results of Examples and Comparative Examples> As shown in FIG7, in the fabrication of the transfer mask using the mask substrate of Examples 1 to 3, the opening widths [W11] and [W11'] of each spatial pattern 11a and 11a' formed on the pattern forming films 11 and 11' are similar to the opening width [W14] of the spatial pattern 14a formed on the resist film 14. Specifically, the increase rate of the width dimension of the spatial pattern 14a formed on the resist film 14 is 6% in Example 1 and 0% in Examples 2 and 3, which is suppressed to a low value. In addition, the above-mentioned increase rate of the width dimension refers to the value obtained by subtracting the opening width [W14] from the above-mentioned opening width [W11] or the above-mentioned opening width [W11'] and dividing it by [W14] (([W11]-[W14]) / [W14] or ([W11']-[W14]) / [W14]). In contrast, in the fabrication of the transfer mask using the mask substrate of Comparative Example 1, the opening width [W11] of the spatial pattern 11a formed on the pattern forming film 11 is 6 nm larger than the opening width [W14] of the spatial pattern 14a formed on the resist film 14. That is, the increase rate of the width dimension in Comparative Example 1 is 18%, which is a relatively large value. Similarly, in Comparative Example 2, the opening width [W11] of the spatial pattern 11a formed on the pattern forming film 11 is 6 nm larger than the opening width [W14] of the spatial pattern 14a formed on the resist film 14, and the aforementioned increase rate of the width dimension is 18%. This confirms that the masking substrate to which the present invention is applied can form fine spatial patterns on a patterning film. Furthermore, by comparing Example 1 and Example 2, it was confirmed that the less tantalum (Ta) oxidation contained in the second hard mask film 13, the greater the swelling of the second hard mask pattern 13P, and the smaller the opening width [W13'] after swelling. In addition, it was confirmed that the swelling of the second hard mask pattern 13P can be controlled by the amount of tantalum (Ta) oxidation contained in the second hard mask film 13. Furthermore, by using a mask substrate to which the present invention is applied, a transfer mask with fine patterns can be manufactured, and a high degree of integration of semiconductor devices made using such a transfer mask can be achieved. 1,2: Masking substrate; 10: Transparent substrate; 11,11': Pattern forming film; 11P,11P': Film pattern; 12: First hard mask film; 12P: First hard mask pattern; 13: Second hard mask film; 13P: Second hard mask pattern; 20: Substrate; 100,200: Mask for transfer. Figure 1 is a cross-sectional view showing the structure of the mask substrate according to the first embodiment of the present invention. Figure 2A is a manufacturing process diagram (1) of the manufacturing method of the transfer mask using the mask substrate of the first embodiment of the present invention. Figure 2B is a manufacturing process diagram (1) of the manufacturing method of the transfer mask following Figure 2A. Figure 2C is a manufacturing process diagram (1) of the manufacturing method of the transfer mask following Figure 2B. Figure 3A is a manufacturing process diagram (2) of the manufacturing method of the transfer mask using the mask substrate of the first embodiment of the present invention. Figure 3B is a manufacturing process diagram (2) of the manufacturing method of the transfer mask following Figure 3A. Figure 4 is a cross-sectional view showing the structure of the mask substrate according to the second embodiment of the present invention. Figure 5A is a manufacturing process diagram (1) of the manufacturing method of the transfer mask using the mask substrate of the second embodiment of the present invention. Figure 5B is a manufacturing process diagram (1) of the manufacturing method of the transfer mask following Figure 5A. Figure 5C is a manufacturing process diagram (1) of the method for manufacturing a transfer mask following Figure 5B. Figure 6A is a manufacturing process diagram (2) of the method for manufacturing a transfer mask using a mask substrate according to the second embodiment of the present invention. Figure 6B is a manufacturing process diagram (2) of the method for manufacturing a transfer mask following Figure 6A. Figure 7 is a diagram illustrating embodiments and comparative examples of the present invention. Figure 8A is a manufacturing process diagram of the method for manufacturing a transfer mask according to a comparative example. Figure 8B is a manufacturing process diagram of the method for manufacturing a transfer mask according to a comparative example following Figure 8A. Figure 8C is a manufacturing process diagram of the method for manufacturing a transfer mask according to a comparative example following Figure 8B. Figure 8D is a manufacturing process diagram of the method for manufacturing a transfer mask according to a comparative example following Figure 8C. 1: Masking base 10: Transparent substrate 11: Thin film for pattern forming 12: First hard masking film 13: Second hard mask film 14: Resistor film S: Main surface

Claims

1. A masking substrate having a structure in which a pattern forming thin film, a first hard masking film, and a second hard masking film are sequentially deposited on the main surface of a substrate; the pattern forming thin film contains at least one element selected from silicon and transition metals; the first hard masking film contains chromium; the second hard masking film contains tantalum; the tantalum in the second hard masking film contains oxygen-unsaturated tantalum; the thickness of the pattern forming thin film is 20 nm or more; the thickness of the first hard masking film is 15 nm or less; and the thickness of the second hard masking film is 10 nm or less.

2. A masking substrate having a structure in which a pattern forming thin film, a first hard masking film, and a second hard masking film are sequentially deposited on the main surface of a substrate; the pattern forming thin film contains at least one element selected from silicon and transition metals; the first hard masking film contains chromium; the second hard masking film contains tantalum and swells in an oxygen-containing gas atmosphere; the thickness of the pattern forming thin film is 20 nm or more; the thickness of the first hard masking film is 15 nm or less; and the thickness of the second hard masking film is 10 nm or less.

3. The masking substrate of claim 1 or 2, wherein the ratio of oxygen content to tantalum content of the second hard masking film is 1.5 or less.

4. The masking substrate of claim 1 or 2, wherein the second hard masking film contains the most tantalum among the metal elements and silicon.

5. The masking substrate of claim 1 or 2, wherein the thickness of the second hard masking film is 1 nm or more.

6. The masking substrate of claim 1 or 2, wherein the first hard masking film contains at least one of chromium, oxygen and nitrogen.

7. The masking substrate of claim 1 or 2, wherein the thickness of the first hard masking film is greater than the thickness of the second hard masking film.

8. The masking substrate of claim 1 or 2, wherein the pattern forming film is a light-absorbing film containing tantalum; and the substrate and the pattern forming film are provided with a multilayer reflective film.

9. The masking substrate of claim 1 or 2, wherein the thin film for pattern formation is a light-shielding film containing silicon.

10. A method for manufacturing a transfer mask, comprising: using a mask substrate as described in any one of claims 1 to 9, a step of forming a second hard mask pattern on the second hard mask film by dry etching, using a resist film having a pattern formed on the second hard mask film as a mask; using the second hard mask pattern as a mask, forming a first hard mask pattern on the first hard mask film by dry etching with an oxygen-containing gas to cause the etched sidewalls of the second hard mask pattern to swell due to oxidation; and using the first hard mask pattern as a mask, forming a thin film pattern on the pattern forming thin film by dry etching.

11. A method for manufacturing a semiconductor device, comprising an exposure step, wherein a transfer mask manufactured by a method for manufacturing a transfer mask as described in claim 10 is used to transfer the thin film pattern of the transfer mask onto a resist film on a substrate for a semiconductor device by photolithography.

Images