Mask blank, transfer mask, and method for manufacturing semiconductor device

Abstract

The objective of this invention is to provide a mask blank that can improve the etching rate of wet etching of the entire thin film for pattern formation and improve the verticality of the pattern sidewalls when patterning the thin film by wet etching. The solution is a mask blank having a thin film for pattern formation on a substrate. This thin film is formed from a chromium-containing material. Furthermore, the thin film is composed of an upper region on the side opposite to the substrate side and regions other than the upper region. Here, the crystal size of the upper region is larger than the crystal size of the regions other than the upper region.

Description

Technical Field

[0001] The present invention relates to a transfer mask used in the manufacture of semiconductor devices, a mask blank used in the manufacture of the transfer mask, and a method for manufacturing semiconductor devices using the transfer mask. Background Technology

[0002] Generally, in the manufacturing process of semiconductor devices, photolithography is used to form fine patterns. This formation of fine patterns typically uses a substrate called a photomask (transfer mask). This photomask generally has light-shielding fine patterns formed from a thin metal film or the like on a transparent glass substrate. Photolithography is also used in the manufacture of this photomask.

[0003] In the manufacture of photomasks using photolithography, a photomask blank having a light-shielding film on a transparent substrate such as a glass substrate (hereinafter sometimes simply referred to as the substrate) is used. The manufacture of a photomask using this photomask blank involves the following steps: a drawing step of drawing a desired pattern on a resist film formed on the photomask blank; a developing step of developing the resist film after drawing to form a resist pattern; an etching step of etching the light-shielding film using the resist pattern as a mask; and a step of removing any remaining resist pattern. In the etching step, using the resist pattern as a mask, the exposed areas of the light-shielding film without a resist pattern are dissolved by, for example, wet etching, thereby forming the desired photomask pattern on the transparent substrate. This completes the photomask process.

[0004] Patent Document 1 discloses a mask blank containing a chromium-based light-shielding film as a mask blank suitable for wet etching. The light-shielding film is disclosed to have, for example, a stacked structure of a first light-shielding film (CrN) / a second light-shielding film (CrC) / an anti-reflective film (CrON) from the substrate side.

[0005] Furthermore, Patent Document 2 also discloses a photomask substrate with a chromium-based material-based layered structure as a mask blank suitable for wet etching. The disclosed light-shielding film has, for example, a layered structure from the substrate side consisting of a first layer (chromium film) / a second layer (a film composed of a mixture of chromium oxide and chromium nitride), or a layered structure consisting of a first layer (a film composed of a mixture of chromium oxide and chromium nitride) / a second layer (chromium film) / a third layer (a film composed of a mixture of chromium oxide and chromium nitride).

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent No. 3276954

[0009] Patent Document 2: Japanese Patent Publication No. 61-46821 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] When patterning thin films of chromium-based materials using wet etching (hereinafter referred to as "wet etching") with an etching solution containing cerium ammonium nitrate as the main component, there is a tendency for chromium oxide films to have a slower etching rate compared to chromium metal films.

[0012] When manufacturing a mask blank for pattern forming thin films by sputtering a chromium metal film on a substrate, oxidation inevitably occurs from the surface of the film opposite to the substrate side during subsequent manufacturing processes.

[0013] For example, after a thin film is formed on a substrate, water rinsing is typically performed to remove defects, during which oxygen enters from the surface of the film (oxidation occurs in the upper region of the film). When using this mask blank to manufacture a transfer mask, the film is patterned by wet etching using a resist pattern as an etching mask. In the process of forming this resist film on the thin film, after applying a resist solution to the surface of the film, the entire mask blank is baked, thereby curing the applied resist. During this baking process, oxygen enters from the surface of the film (further oxidation occurs in the upper region of the film).

[0014] Generally, it is required that the patterning film of the mask blank has low surface reflectivity to exposure light (the light that irradiates the transfer mask made from the mask blank when placed in an exposure apparatus). While containing nitrogen in the surface layer (upper region) of the film can reduce surface reflectivity to exposure light to some extent, this is insufficient in most cases. Containing oxygen in the upper region of the film can significantly reduce surface reflectivity to exposure light. However, to achieve a sufficient reduction in surface reflectivity, a relatively high amount of oxygen must be present in the upper region of the film. This higher oxygen content in the upper region of the film results in an amorphous structure, becoming a dense structure, which slows down the etching rate for wet etching, thus creating a problem when patterning the film.

[0015] On the other hand, it is desirable that the etching rate of the substrate-side region (lower region) of the patterned thin film is faster for wet etching than that of the inner region (middle region) of the thin film. Generally, wet etching tends to be isotropic. Therefore, when wet etching is performed from the surface opposite to the substrate side of the thin film to the substrate-side surface, the sidewalls of the thin film pattern tend to become conical (the linewidth of the thin film pattern widens towards the substrate side). Therefore, generally, after the wet etching of the thin film continues until the surface of the substrate is exposed, etching for sidewall etching (so-called over-etching) is mainly performed on the lower region of the thin film. However, in isotropic wet etching, simply increasing the undercut cannot improve the perpendicularity of the sidewalls of the thin film pattern. Therefore, it is desirable to increase the etching rate of the lower region of the thin film. Here, improving the perpendicularity of the sidewalls of the thin film pattern means achieving a cross-sectional shape of the thin film pattern that is nearly perpendicular to the film surface.

[0016] The present invention was made to solve the existing problems, and its object is to provide a mask blank that can improve the etching rate of wet etching of the entire thin film for pattern formation, and thereby improve the perpendicularity of the pattern sidewalls when patterning the thin film by wet etching.

[0017] In addition, the present invention aims to provide a transfer mask that improves the verticality of the sidewalls of a thin film pattern.

[0018] Furthermore, an object of the present invention is to provide a method for manufacturing a semiconductor device using the transfer mask.

[0019] Problem Solving Methods

[0020] As described above, in view of the problem that it is difficult to achieve a good cross-sectional shape of the thin film pattern formed by wet etching in the past, the inventors conducted in-depth research and found that, for example, by adjusting the crystal size of the chromium-based material constituting the thin film for pattern formation in the upper region opposite to the substrate side of the thin film for pattern formation and in the region other than the upper region, the etching rate of the thin film for pattern formation as a whole by wet etching can be increased, and the perpendicularity of the pattern sidewalls when forming a pattern on the thin film by wet etching can be improved.

[0021] In other words, in order to solve the above problems, the present invention has the following solution.

[0022] (Option 1)

[0023] A mask blank having a pattern-forming thin film on a substrate, the thin film being formed of a chromium-containing material, the thin film being composed of an upper region on the opposite side of the substrate and a region other than the upper region, the crystal size of the upper region being larger than the crystal size of the region other than the upper region.

[0024] (Option 2)

[0025] According to the mask blank described in Scheme 1, the upper region and the regions other than the upper region of the film are both polycrystalline structures.

[0026] (Option 3)

[0027] According to the mask blank described in Scheme 1 or 2, the interplanar spacing of the upper region and the regions other than the upper region of the thin film obtained by electron diffraction is 0.2 nm or more.

[0028] (Option 4)

[0029] According to any one of Schemes 1 to 3, the mask blank wherein the upper region and the regions other than the upper region of the film have columnar structures.

[0030] (Option 5)

[0031] According to any one of the mask blanks in Schemes 1 to 4, the region of the thin film other than the upper region is composed of a lower region and a middle region from the substrate side, and the crystal size of the thin film increases in the order of the middle region, the lower region, and the upper region.

[0032] (Option 6)

[0033] According to any one of Schemes 1 to 5, the mask blank is a composition gradient film in which the chromium content varies in the thickness direction.

[0034] (Option 7)

[0035] According to any one of Schemes 1 to 6, the mask blank is a light-shielding film having a light density of 3 or more for exposure light.

[0036] (Option 8)

[0037] A transfer mask has a thin film with a transfer pattern on a substrate. The thin film is formed of a chromium-containing material and consists of an upper region on the opposite side of the substrate and a region other than the upper region. The crystal size of the upper region is larger than the crystal size of the regions other than the upper region.

[0038] (Option 9)

[0039] According to the transfer mask described in Scheme 8, the upper region and the regions other than the upper region of the thin film are both polycrystalline structures.

[0040] (Option 10)

[0041] According to the transfer mask described in Scheme 8 or 9, the interplanar spacing of the upper region and the regions other than the upper region of the thin film obtained by electron diffraction is 0.2 nm or more.

[0042] (Option 11)

[0043] According to any one of Schemes 8 to 10, the transfer mask has a columnar structure in the upper region and the region other than the upper region of the film.

[0044] (Option 12)

[0045] According to any one of Schemes 8 to 11, the transfer mask, except for the upper region, is composed of a lower region and a middle region from the substrate side, and the crystal size of the film increases in the order of the middle region, the lower region, and the upper region.

[0046] (Option 13)

[0047] According to any one of Schemes 8 to 12, the transfer mask is a composition gradient film in which the content of chromium varies in the thickness direction.

[0048] (Option 14)

[0049] According to any one of Schemes 8 to 13, the transfer mask is a light-shielding film having a light density of 3 or more for exposure light.

[0050] (Option 15)

[0051] A method for manufacturing a semiconductor device, comprising: using a transfer mask as described in any one of claims 8 to 14 to expose and transfer a transfer pattern onto a resist film on a semiconductor substrate.

[0052] The effects of the invention

[0053] According to the present invention, a mask blank can be provided that can improve the etching rate of wet etching of the entire thin film for pattern formation, and thereby improve the perpendicularity of the pattern sidewalls when patterning the thin film by wet etching.

[0054] In addition, according to the present invention, a transfer mask that improves the verticality of the sidewalls of the thin film pattern can be provided.

[0055] Furthermore, according to the present invention, a method for manufacturing a semiconductor device in which a good transfer pattern can be formed using the above-described transfer mask can be provided. Attached Figure Description

[0056] Figure 1 This is a cross-sectional view showing one embodiment of the mask blank of the present invention.

[0057] Figure 2 This is a cross-sectional view showing one embodiment of the transfer mask of the present invention.

[0058] Figure 3 This is a cross-sectional view showing the manufacturing process of a transfer mask using the mask blank of the present invention.

[0059] Figure 4 An electron beam diffraction image of the upper region of the light-shielding film in the mask blank of Embodiment 1 of the present invention is shown.

[0060] Figure 5 An electron beam diffraction image of the central region of the light-shielding film in the mask blank of Embodiment 1 of the present invention is shown.

[0061] Figure 6 An electron beam diffraction image of the lower region of the light-shielding film in the mask blank of Embodiment 1 of the present invention is shown.

[0062] Figure 7 A cross-sectional TEM image of the light-shielding film in the mask blank of Embodiment 1 of the present invention is shown.

[0063] Figure 8 An electron beam diffraction image of the upper region of the light-shielding film in the mask blank of Embodiment 2 of the present invention is shown.

[0064] Figure 9 An electron beam diffraction image of the central region of the light-shielding film in the mask blank of Embodiment 2 of the present invention is shown.

[0065] Figure 10 The image shows an electron beam diffraction image of the lower region of the light-shielding film in the mask blank of Embodiment 2 of the present invention.

[0066] Figure 11 A cross-sectional TEM image of the light-shielding film in the mask blank of Embodiment 2 of the present invention is shown.

[0067] Figure 12 An electron beam diffraction image of the upper region of the light-shielding film in the mask blank of Embodiment 3 of the present invention is shown.

[0068] Figure 13 An electron beam diffraction image of the central region of the light-shielding film in the mask blank of Embodiment 3 of the present invention is shown.

[0069] Figure 14 The image shows an electron beam diffraction image of the lower region of the light-shielding film in the mask blank of Embodiment 3 of the present invention.

[0070] Figure 15 A cross-sectional TEM image of the light-shielding film in the mask blank of Embodiment 3 of the present invention is shown.

[0071] Figure 16 This is a diagram showing the electron beam diffraction image of the upper region of the light-shielding film in the mask blank of the comparative example.

[0072] Figure 17 An electron beam diffraction image of the central region of the light-shielding film in the mask blank of the comparative example is shown.

[0073] Figure 18 An electron beam diffraction image of the lower region of the light-shielding film in the mask blank of the comparative example is shown.

[0074] Figure 19 A cross-sectional TEM image of the light-shielding film in the mask blank of the comparative example is shown.

[0075] Symbol Explanation

[0076] 1 substrate

[0077] 2 Thin film for pattern forming

[0078] 3. Anti-corrosion film

[0079] 2a Thin film patterns (transfer patterns, light-blocking film patterns)

[0080] 3a Anti-corrosion pattern

[0081] 10 Mask blank

[0082] 20 Transfer Masks Detailed Implementation

[0083] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0084] [Mask blank]

[0085] First, the mask blank of the present invention will be described.

[0086] Figure 1 This is a cross-sectional view showing one embodiment of the mask blank of the present invention.

[0087] Figure 1 The mask blank 10 shown is a mask blank in which a thin film 2 for pattern formation is provided on a substrate 1.

[0088] In the mask blank 10 of this embodiment, the thin film 2 is formed of a chromium-containing material. In addition, the thin film 2 is characterized in that it is composed of two regions: an upper region on the side opposite to the substrate 1 and a region other than the upper region, and the crystal size of the upper region is larger than the crystal size of the region other than the upper region.

[0089] Here, a light-transmitting substrate is suitable as the aforementioned substrate 1. A glass substrate is generally considered as such a substrate. Glass substrates have excellent flatness and smoothness; therefore, when transferring patterns onto a substrate using a transfer mask, no pattern skewing occurs, allowing for high-precision pattern transfer. Besides synthetic quartz glass, other glass materials such as quartz glass, aluminosilicate glass, soda lime glass, and low-thermal-expansion glass (SiO2-TiO2 glass, etc.) can also be used as the light-transmitting substrate. Among these, synthetic quartz glass has high transmittance for, for example, ArF excimer lasers (wavelength 193 nm) used as exposure light, and is particularly preferred as the material for the substrate 1 used to form the mask blank 10.

[0090] The thin film 2 used for pattern formation is formed from a chromium-containing material, such as a light-shielding film. Examples of materials for the thin film 2 include elemental chromium or chromium compounds containing elements such as oxygen, nitrogen, and carbon. Preferably, the material constituting the thin film 2 does not contain elements such as silicon, which significantly reduce the wet etching rate. For the material constituting the thin film 2, the total content of chromium and non-metallic elements is preferably 95 atomic% or more, more preferably 98 atomic% or more, and even more preferably 99 atomic% or more. Furthermore, for the material constituting the thin film 2, the total content of chromium, oxygen, nitrogen, and carbon is preferably 95 atomic% or more, more preferably 98 atomic% or more, and even more preferably 99 atomic% or more. In this embodiment, the thickness of the thin film 2 is not particularly limited, and a range of 80 nm to 150 nm is suitable.

[0091] As described above, in this embodiment, the thin film 2 is composed of two regions: an upper region on the side opposite to the substrate 1 and a region other than the upper region.

[0092] The pattern-forming film 2 in the mask blank 10 is required to have low surface reflectivity to exposure light (the light that irradiates the transfer mask manufactured from the mask blank 10 when it is placed in an exposure apparatus). Therefore, in this embodiment, it is desirable for the upper region to have anti-reflective properties. By containing, for example, nitrogen in the upper region of the film 2, the surface reflectivity to exposure light can be reduced to a certain extent. Furthermore, if oxygen is contained in the upper region of the film 2, the surface reflectivity to exposure light can be significantly reduced. Therefore, the upper region of the film 2 is preferably made of materials such as CrO, CrON, CrOC, or CrOCN. In this case, the oxygen and nitrogen content can be appropriately adjusted considering the surface reflectivity of the film 2 to exposure light.

[0093] In this embodiment, the thickness of the upper region of the above-mentioned film 2 is not particularly limited, and a range of 10nm to 50nm is suitable.

[0094] Furthermore, from the viewpoint of improving the overall light-shielding performance of the film 2 against exposure light, it is preferable that the oxygen content in the regions of the film 2 other than the upper region is less than that in the upper region of the film 2, and even more preferably, it is substantially oxygen-free. Additionally, it is preferable that the chromium content in the regions of the film 2 other than the upper region is more than that in the upper region of the film 2. The regions of the film 2 other than the upper region are preferably made of materials such as Cr, CrN, CrC, CrCN, etc.

[0095] The mask blank 10 of this embodiment is characterized in that the crystal size of the upper region of the thin film 2 is larger than the crystal size of the regions other than the upper region.

[0096] When patterning a chromium-based thin film 2 using wet etching, a larger crystal size allows the wet etching solution to penetrate the film more easily, increasing the wet etching rate. The upper region of the thin film 2 is prone to oxidation, and oxygen is necessary to provide anti-reflective properties. It is known that the presence of oxygen in chromium reduces the wet etching rate. In this invention, by making the crystal size of the upper region larger than that of other regions, the wet etching rate of the upper region can be increased. That is, by making the crystal size of the upper region of the thin film 2 larger than that of other regions, the wet etching rate of the upper region for pattern formation can be faster than that of other regions. While it is desirable for the cross-sectional shape of the thin film pattern formed by wet etching to be as perpendicular as possible to the film surface, the above configuration improves the overall etching rate of the thin film 2 and enhances the perpendicularity of the pattern sidewalls when patterning the thin film 2 using wet etching.

[0097] In this embodiment, it is preferable that the upper region and the regions other than the upper region of the thin film 2 are both polycrystalline structures. By setting each region of the thin film 2 as a polycrystalline structure in which various crystals of chromium metal or chromium compounds are mixed, the crystal size is less likely to become too large. In addition, the edge roughness of the pattern sidewalls when patterning the thin film 2 can be reduced.

[0098] Furthermore, in this embodiment, it is preferable that the interplanar spacing of the upper region and the regions other than the upper region of the thin film 2 obtained by electron diffraction is 0.2 nm or more. A smaller interplanar spacing results in a denser crystalline structure, but the wet etching rate is excessively reduced, making it difficult to improve the overall etching rate of the thin film 2.

[0099] Furthermore, in this embodiment, it is preferable that the upper region and all other regions of the thin film 2 have columnar structures. When each region of the thin film 2 has a columnar structure, the wet etching solution can more easily penetrate the thin film 2, further increasing the wet etching rate.

[0100] For example, when the thin film 2 is formed by sputtering, the crystal size of each region of the thin film 2 can be adjusted by controlling the pressure of the sputtering gas introduced into the chamber, the temperature of the chamber, the film formation rate, the voltage applied to the target, the current value, etc.

[0101] The method for forming the aforementioned thin film 2 is not particularly limited, but sputtering is a preferred method. Sputtering can form a film with uniform in-plane distribution and constant thickness. When forming the aforementioned thin film 2 on the substrate 1 by sputtering, a chromium (Cr) target is used as the sputtering target, and the sputtering gas introduced into the chamber is a gas containing oxygen and nitrogen or carbon dioxide and nitric oxide mixed with an inert gas such as argon or helium. If a sputtering gas containing oxygen or carbon dioxide is used, a thin film containing oxygen in chromium can be formed; if a sputtering gas containing nitrogen is used, a thin film containing nitrogen in chromium can be formed. Furthermore, if a sputtering gas containing nitric oxide is used, a thin film containing both nitrogen and oxygen in chromium can be formed. Additionally, if a sputtering gas containing methane is used, a thin film containing carbon in chromium can be formed.

[0102] Furthermore, in this embodiment, the aforementioned thin film 2 is preferably a composition gradient film in which the chromium content varies in the thickness direction. Therefore, when a pattern is formed on the thin film 2 by wet etching, height differences are less likely to occur in the sidewall shape of the pattern. To produce such a composition gradient film 2, it is suitable, for example, to appropriately change the type (composition) of the sputtering gas used in the aforementioned sputtering film formation process.

[0103] Furthermore, in this embodiment, the aforementioned thin film 2 can be made into a light-shielding film, for example, having an optical density of 3 or higher for exposure light and formed from the aforementioned chromium-based material. It should be noted that the exposure light irradiating the transfer mask manufactured from the mask blank of this embodiment can include, for example, light containing gamma rays (wavelength approximately 436 nm), light containing i-rays (wavelength approximately 365 nm), KrF excimer laser (wavelength approximately 248 nm), and ArF excimer laser (wavelength approximately 193 nm).

[0104] On the other hand, the thin film 2 of this embodiment can be used as a light-shielding film in a mask blank in which a semi-transparent film and a light-shielding film are sequentially stacked on a substrate 1. In this case, it is preferable that the optical density for the exposure light is 3 or more through the stacked structure of the semi-transparent film and the light-shielding film. In this case, the semi-transparent film is preferably a phase-shifting film having the following functions: the function of allowing the exposure light to pass through with a given transmittance (e.g., a transmittance of 1% or more and 30% or less), and the function of generating a given phase difference (e.g., a phase difference of 150 degrees or more and 210 degrees or less) between the exposure light that passes through the film and the exposure light that passes through the air only at the same distance as the thickness of the film.

[0105] Next, other implementation methods will be described.

[0106] This other embodiment further comprises, from the substrate 1 side, a lower region and a middle region, in the area of ​​the thin film 2 described in the above embodiment, excluding the upper region. In other words, in this other embodiment, the thin film 2 formed from a chromium-containing material is composed of three regions from the substrate 1 side: a lower region, a middle region, and an upper region. In this case, it is preferable that the crystal size of the thin film 2 increases in the order of the middle region, lower region, and upper region.

[0107] As described above, when patterning a chromium-based thin film 2 using wet etching, a larger crystal size allows the wet etching solution to penetrate the film more easily, increasing the wet etching rate. The upper region of the thin film 2 is prone to oxidation, and oxygen must be present to provide anti-reflective properties. It is known that the presence of oxygen in chromium reduces the wet etching rate. In other embodiments, by maximizing the crystal size in the upper region within the entire thin film 2, the wet etching rate in the upper region can be increased. Furthermore, conventionally, wet etching tends to result in low verticality of the sidewall shape of the pattern formed on the thin film 2; therefore, it is desirable to increase the wet etching rate in the region on the substrate 1 side of the thin film 2 (the aforementioned lower region). In other embodiments, by making the crystal size in the lower region of the thin film 2 larger than the crystal size in the interior of the thin film 2 excluding the upper and lower regions (the aforementioned middle region), the wet etching rate in the lower region can be increased. In this way, by increasing the crystal size of the thin film 2 in the order of the middle region, the lower region, and the upper region, the verticality of the pattern sidewalls when forming a pattern by wet etching can be improved.

[0108] As described above, by fabricating the mask blank according to other embodiments, the etching rate of wet etching for each region within the thin film 2 used for pattern formation can be increased in the order of the middle region, the lower region, and the upper region. As a result, the overall etching rate of the thin film 2 of the mask blank 10 is improved, and the perpendicularity of the pattern sidewalls formed by wet etching on the thin film 2 can be improved.

[0109] The upper region of the aforementioned film 2 uses the same chromium-based material as in the above-described embodiment.

[0110] From the viewpoint of improving the overall light-shielding performance of the film 2, it is preferable that the oxygen content in the central region of the film 2 is less than that in the upper and lower regions, and more preferably, it is substantially oxygen-free. Furthermore, it is preferable that the chromium content in the central region of the film 2 is more than that in the upper and lower regions. The central region of the film 2 is preferably made of materials such as Cr, CrN, CrC, or CrCN.

[0111] From the viewpoint of improving the overall light-shielding performance of film 2 against exposure light, it is preferable that the oxygen content in the lower region of film 2 is lower than that in the upper region of film 2. Furthermore, from the viewpoint of reducing the reflectivity of the back side (the side in contact with the substrate) of film 2, it is preferable that the nitrogen content in the lower region of film 2 is higher than that in the upper and middle regions of film 2. The lower region of film 2 is preferably made of materials such as CrN, CrCN, or CrON.

[0112] In other embodiments, the thickness of the upper region of the above-mentioned film 2 is not particularly limited, and a range of 10 nm to 50 nm is suitable.

[0113] There is no particular limitation on the thickness of the central region of the aforementioned film 2. From the viewpoint of improving the overall light-shielding performance of film 2 against exposure light, a range of 25nm to 70nm is suitable.

[0114] There is no particular limitation on the thickness of the lower region of the aforementioned thin film 2. From the viewpoint of reducing the reflectivity of the back side of the thin film 2, a range of 5 nm to 30 nm is suitable.

[0115] Regarding other embodiments, for the same reasons as the embodiments described above, it is preferable that the lower region, middle region, and upper region of the thin film 2 are all polycrystalline structures.

[0116] Regarding other embodiments, for the same reasons as the embodiments described above, it is preferable that the interplanar spacing of the lower region, middle region, and upper region of the thin film 2 obtained by electron diffraction is 0.2 nm or more.

[0117] Regarding other embodiments, for the same reasons as the embodiments described above, it is preferable that the lower region, middle region, and upper region of the film 2 all have columnar structures.

[0118] Regarding other embodiments, for the same reasons as the embodiments described above, it is preferable that the thin film 2 is a composition gradient film in which the chromium content varies in the thickness direction.

[0119] Regarding other embodiments, the aforementioned film 2 may also be made into a light-shielding film, for example, having an optical density of 3 or higher for exposure light and formed of a chromium-based material. Other matters related to the mask blank in this other embodiment are the same as those in the mask blank of the embodiments described above.

[0120] As described in the above embodiments, the mask blank according to the present invention can improve the etching rate of wet etching of the entire thin film for pattern formation, and further improve the perpendicularity of the pattern sidewalls when patterning the thin film by wet etching.

[0121] In the above embodiments, a mask blank having a pattern-forming thin film 2 on a substrate 1 has been described, but the present invention is not limited to such embodiments. For example, a mask blank having a semi-transparent light film having the function of allowing exposure light to pass through with a given transmittance (e.g., 1% or more and 40% or less) between the light-transmitting substrate 1 and the pattern-forming thin film (light-shielding film) 2 is also included in the mask blank of the present invention. This semi-transparent light film may be a phase-shifting film having the function of generating a given phase difference (e.g., a phase difference of 150 degrees or more and 210 degrees or less) between the exposure light that has passed through the interior of the semi-transparent light film and the exposure light that has passed through the air at a distance equal to the thickness of the semi-transparent light film. In these configurations, it is preferable that the optical density for the exposure light is 3 or more through the stacked structure of the semi-transparent light film (or phase-shifting film) and the light-shielding film.

[0122] On the other hand, the mask blank of the present invention is not limited to the use of manufacturing transfer masks used in the manufacture of semiconductor devices. For example, the mask blank of the present invention can also be used for manufacturing transfer masks used in the manufacture of display devices such as FPDs (Flat Panel Displays) represented by LCDs (Liquid Crystal Displays) and OLEDs (Organic Light Emitting Diodes).

[0123] [Transfer Mask]

[0124] Next, the transfer mask of the present invention will be described.

[0125] Figure 2 This is a cross-sectional view showing one embodiment of the transfer mask of the present invention.

[0126] Figure 2 The transfer mask 20 of one embodiment of the present invention shown has a thin film 2 having a transfer pattern (thin film pattern, hereinafter sometimes simply referred to as pattern) 2a on a substrate 1. In this transfer mask 20, the thin film 2 is formed of a chromium-containing material. Furthermore, the thin film 2 is characterized by being composed of an upper region on the side opposite to the substrate 1 and regions other than the upper region, with the crystal size of the upper region being larger than the crystal size of the regions other than the upper region. In this case, the structure of the substrate 1 and the thin film 2 is the same as that of the mask blank 10 described above.

[0127] Such a transfer mask 20 of the present invention can be manufactured using, for example, the mask blank 10 of the present invention described above. Details relating to the manufacturing method of the transfer mask will be described later.

[0128] As mentioned above, such as Figure 1The mask blank 10 of one embodiment of the present invention shown has a thin film 2 for pattern formation on a substrate 1. This thin film 2 is formed of a chromium-containing material. Furthermore, the thin film 2 is composed of an upper region on the side opposite to the substrate 1 and regions other than the upper region, and the crystal size of the upper region is larger than the crystal size of the regions other than the upper region. By configuring the mask blank 10 in this way, the etching rate of the wet etching of the entire thin film 2 for pattern formation can be increased, thereby improving the perpendicularity of the pattern sidewalls when forming a pattern on the thin film 2 by wet etching. As a result, the transfer mask 20 made from this mask blank 10 becomes a transfer mask with improved perpendicularity of the pattern sidewalls and forms a transfer pattern with good cross-sectional shape with good precision. Similarly, in this transfer mask 20, the thin film 2 having the transfer pattern 2a is also formed of a chromium-containing material. In addition, the thin film 2 is composed of an upper region on the opposite side of the substrate 1 and a region other than the upper region, and is configured such that the crystal size of the upper region is larger than the crystal size of the region other than the upper region.

[0129] As described above, in the mask blank 10, it is preferable that the upper region and the regions other than the upper region of the thin film 2 are both polycrystalline. Furthermore, in the transfer mask 20 made from the mask blank 10, it is also preferable that the upper region and the regions other than the upper region of the thin film 2 are both polycrystalline. This reduces the edge roughness of the sidewalls of the formed transfer pattern.

[0130] In addition, similar to the case of the mask blank 10 described above, in the transfer mask 20, it is also preferable that the interplanar spacing of the upper region and the region other than the upper region of the thin film 2 obtained by electron diffraction is 0.2 nm or more.

[0131] Furthermore, similar to the case of the mask blank 10 described above, in the transfer mask 20, it is also preferable that the upper region and the regions other than the upper region of the thin film 2 both have columnar structures. As a result, the etching rate of wet etching of the thin film 2 in the mask blank 10 is improved, and the verticality of the sidewalls of the transfer pattern formed in the transfer mask 20 is improved.

[0132] Furthermore, similar to the case of the mask blank 10 described above, in the transfer mask 20, the thin film 2 is preferably a composition gradient film in which the chromium content varies in the thickness direction. This ensures that the sidewall shape of the formed transfer pattern does not exhibit a height difference.

[0133] Furthermore, similar to the case of the mask blank 10 described above, in the transfer mask 20, it is also preferable to make the aforementioned thin film 2 into a light-shielding film, for example, having an optical density of 3 or more for exposure light, and formed of a chromium-based material. In this case, the light-shielding film is the same as that in the case of the mask blank 10 described above.

[0134] Next, other embodiments of the above-described transfer mask 20 will be described.

[0135] This other embodiment further comprises, from the substrate side, a lower region and a middle region, the region of the aforementioned thin film 2 excluding the upper region. In other words, in the transfer mask 20 of this other embodiment, the thin film 2, formed from a chromium-containing material, is formed from the substrate 1 side by three regions: a lower region, a middle region, and an upper region. In this case, the crystal size of the thin film 2 is configured to increase in the order of the middle region, the lower region, and the upper region.

[0136] The transfer mask 20 of such other embodiments can be manufactured using, for example, the mask blank 10 of other embodiments described above.

[0137] As described above, in the mask blanks of other embodiments, by increasing the crystal size of the thin film 2 in the order of the middle region, lower region, and upper region, the etching rate of wet etching for each region within the thin film 2 can be increased in the order of the middle region, lower region, and upper region. As a result, the overall etching rate of the thin film 2 of the mask blank 10 is increased, and the perpendicularity of the pattern sidewalls when forming a pattern on the thin film 2 by wet etching can be improved. Consequently, the transfer mask 20 manufactured from the mask blank 10 of other embodiments becomes a transfer mask that forms a transfer pattern with good precision, improved perpendicularity of the pattern sidewalls, and a good cross-sectional shape.

[0138] It is suitable to manufacture the transfer mask of the present invention using the mask blank of the present invention described above.

[0139] Next, for those who used Figure 1 The manufacturing method of the transfer mask 20 of the mask blank 10 of the present invention will be described.

[0140] The manufacturing method of the transfer mask 20 using the mask blank 10 includes, for example, a step of drawing a desired pattern on a resist film formed on the mask blank 10; a step of developing the resist film after pattern drawing to form a resist pattern; a step of using the resist pattern as a mask to form a pattern on a thin film 2 for pattern forming on the mask blank 10 by wet etching; and a step of peeling off the remaining resist pattern.

[0141] Figure 3 This is a cross-sectional view showing the manufacturing process of a transfer mask using the mask blank of the present invention.

[0142] Figure 3 (a) shows in Figure 1The mask blank 10 has a pattern forming thin film 2 on which a resist film 3 has been formed. It should be noted that either a positive resist or a negative resist can be used as the resist material, but in the fabrication of transfer masks used in semiconductor device manufacturing, a positive resist material is usually suitable.

[0143] Next, Figure 3 (b) shows the process of performing a desired patterning on the resist film 3 formed on the mask blank 10. The patterning is performed using a laser patterning device, an electron beam patterning device, or the like.

[0144] Next, Figure 3 (c) shows the process of developing the resist film 3 after the desired pattern is drawn to form the resist pattern 3a.

[0145] Next, Figure 3 (d) illustrates an etching process in which the resist pattern 3a described above is used as a mask and a pattern is formed on the thin film 2 for pattern formation of the mask blank 10 by wet etching. Through this etching process, the desired transfer pattern (thin film pattern) 2a is formed on the thin film 2.

[0146] The etching solution used in wet etching is generally an aqueous solution obtained by adding perchloric acid to cerium ammonium nitrate. The concentration of the etching solution, temperature, processing time, and other conditions for wet etching are appropriately set according to the etching characteristics of the thin film 2.

[0147] Figure 3 (e) shows the transfer mask 20 obtained by peeling off the remaining resist pattern 3a.

[0148] In this way, a transfer mask 20 having a thin film 2 with a transfer pattern 2a on a substrate 1 is completed. Through the present invention, a transfer mask 20 is completed that forms a transfer pattern with good precision, improved verticality of the pattern sidewalls, and good cross-sectional shape.

[0149] In the above embodiments, a transfer mask having a thin film 2 having a transfer pattern (thin film pattern) 2a on a substrate 1 and its manufacturing method have been described, but the present invention is not limited to such embodiments. Similar to the case of the mask blank described above, for example, a transfer mask having a semi-transparent light pattern (pattern of a semi-transparent film) between the light-transmitting substrate 1 and the thin film pattern (light-shielding pattern) 2a, which allows exposure light to pass through at a given transmittance (e.g., 1% or more and 40% or less), is also included in the transfer mask of the present invention. This semi-transparent light pattern may further have the function of generating a given phase difference (e.g., a phase difference of 150 degrees or more and 210 degrees or less) between the exposure light that passes through the interior of the pattern and the exposure light that passes through the air at a distance equal to the thickness of the pattern (semi-transparent film). In these configurations, it is preferable that the optical density for the exposure light is 3 or more through the stacked structure of the semi-transparent light pattern (or phase-shifting pattern) and the light-shielding pattern.

[0150] On the other hand, the transfer mask of the present invention is not limited to its use as a transfer mask in the manufacture of semiconductor devices. For example, the transfer mask of the present invention can also be applied to the manufacture of transfer masks used in the manufacture of display devices such as FPDs (Flat Panel Displays) represented by LCDs (Liquid Crystal Displays) and OLEDs (Organic Light Emitting Diodes).

[0151] [Semiconductor device manufacturing methods]

[0152] In addition, the present invention also provides a method for manufacturing a semiconductor device.

[0153] The semiconductor device manufacturing method of the present invention is characterized by comprising a step of exposing and transferring a transfer pattern onto a resist film on a semiconductor substrate using the transfer mask 20 described above.

[0154] The transfer mask 20 of the present invention forms a transfer pattern with improved verticality of the pattern sidewalls. As a result, for example, when the transfer mask 20 is set on the mask stage of an exposure apparatus that uses i-ray light as the exposure light, and the transfer pattern is exposed and transferred to the resist film on the semiconductor substrate, the pattern can be transferred to the resist film on the semiconductor substrate with a precision that fully meets the design specifications.

[0155] According to the present invention, a semiconductor device with a highly precise transfer pattern can be manufactured using the transfer mask of the present invention.

[0156] As detailed above, according to the present invention, a mask blank can be provided that can improve the etching rate of wet etching of the entire thin film for pattern formation, and thereby improve the perpendicularity of the pattern sidewalls when patterning the thin film by wet etching.

[0157] In addition, according to the present invention, a transfer mask that improves the verticality of the sidewalls of the thin film pattern can be provided.

[0158] Furthermore, according to the present invention, a method for manufacturing a semiconductor device capable of forming a good transfer pattern using the transfer mask of the present invention can be provided.

[0159] Example

[0160] The embodiments of the present invention will be described in more detail below through examples.

[0161] (Example 1)

[0162] The mask blank 10 of Example 1 is a mask blank having a structure of a thin film (light-shielding film) 2 for pattern formation on a light-transmitting substrate 1. The mask blank 10 is manufactured as described below.

[0163] Prepare three transparent substrates 1 (approximately 152 mm × 152 mm × 6.35 mm thick) made of synthetic quartz glass. Grind the main surface and end face of the transparent substrate 1 to a given surface roughness (e.g., the main surface roughness is less than 0.2 nm in terms of root mean square roughness Rq).

[0164] Next, a light-shielding film 2, consisting of a lower region, a middle region, and an upper region, was formed on the three light-transmitting substrates 1 using the following method.

[0165] First, a tandem sputtering apparatus with multiple chromium (Cr) targets positioned along the transport direction of the transparent substrate 1 is prepared in the sputtering chamber. Inside this sputtering chamber, the transparent substrate 1 is transported while a mixture of argon (Ar) and nitrogen (N2) gas (flow rate ratio Ar:N2 = 22:4, pressure = 3.0 × 10⁻⁶) is applied. -4 In an atmosphere of Pa, a voltage is applied to a Cr target under constant current control of 0.8A to perform reactive sputtering (DC sputtering), thereby forming the lower region of the light-shielding film 2 on the aforementioned light-transmitting substrate 1.

[0166] Next, within the sputtering chamber, while transporting the film to the light-transmitting substrate 1 in the lower region, a mixture of argon (Ar), methane (CH4), and helium (He) gas (flow rate ratio Ar:CH4:He = 10:1:20, pressure = 3.0 × 10⁻⁶) is applied. -4In an atmosphere of Pa, a voltage is applied to a Cr target under constant current control of 3.6A to perform reactive sputtering (DC sputtering), thereby forming a middle region by grounding with the lower region of the light-shielding film 2.

[0167] Next, within the sputtering chamber, a light-transmitting substrate 1, formed to the central region, is transported while a mixture of argon (Ar) and nitric oxide (NO) gas (flow rate ratio Ar:NO = 100:7, pressure = 3.0 × 10⁻⁶) is applied. -4 In an atmosphere of Pa, a voltage is applied to a Cr target under constant current control of 0A to perform reactive sputtering (DC sputtering), thereby grounding the target to the middle region of the light-shielding film 2 to form an upper region. Using the above method, a mask blank 10 of Embodiment 1 was fabricated, which has a light-shielding film 2 consisting of a lower region, a middle region, and an upper region on the light-transmitting substrate 1.

[0168] It should be noted that the optical density of the light-shielding film 2 in this embodiment 1 is, for example, 3.0 or higher under light at the wavelength (365nm) of i-rays.

[0169] Next, the light-shielding film of the mask blank 10 of the first embodiment 1 was analyzed using X-ray photoelectron spectroscopy (XPS). The results showed that the film thickness of the light-shielding film 2 was 100 nm, and the film thickness and composition of each region were as follows: lower region (film thickness approximately 9 nm, composition Cr:C:O:N = 76 atomic%: 2 atomic%: 2 atomic%: 20 atomic%), middle region (film thickness approximately 54 nm, composition Cr:C:O:N = 85 atomic%: 4 atomic%: 1 atomic%: 10 atomic%), and upper region (film thickness approximately 37 nm, composition Cr:O:N = 55 atomic%: 28 atomic%: 17 atomic%).

[0170] Next, cross-sectional TEM (Transmission Electron Microscope) images of the light-shielding film 2 of the mask blank 10 of the second embodiment 1 were observed, and the crystallinity was observed using electron diffraction. Figure 4 This is an electron beam diffraction image of the upper region of the light-shielding film 2 in the mask blank 10 of Example 1. Figure 5 This is an electron beam diffraction image of the central region of the light-shielding film 2 in the mask blank 10 of Example 1. Additionally, Figure 6 This is an electron beam diffraction image of the lower region of the light-shielding film 2 in the mask blank 10 of Example 1.

[0171] in addition, Figure 7 This is a cross-sectional TEM image of the light-shielding film 2 in the mask blank 10 of Example 1.

[0172] exist Figure 4 In the electron beam diffraction image of the upper region of the light-shielding film 2 shown, the crystallinity is good and the diffraction pattern is clear. The grains in the upper region are large, thus clearly displaying the diffraction pattern. The grains in the upper region are the largest among the three regions.

[0173] exist Figure 5 In the electron beam diffraction pattern of the central region of the light-shielding film 2 shown, the crystallinity is low, and the diffraction pattern is not very clear. The central region has the smallest grain size among the three regions.

[0174] It can be known that in Figure 6 In the electron beam diffraction image of the lower region of the light-shielding film 2 shown, and... Figure 5 Compared to the central region, lattice points were observed, and the grains were slightly larger.

[0175] Based on the above, it can be confirmed that the crystal size of the light-shielding film in the mask blank 10 of this embodiment 1 increases in the order of the middle region, the lower region, and the upper region. Therefore, the etching rate of wet etching for each region within the light-shielding film 2 can increase in the order of the middle region, the lower region, and the upper region. Consequently, the overall etching rate of the light-shielding film 2 in the mask blank 10 of this embodiment 1 is improved, and the perpendicularity of the pattern sidewalls when forming patterns on the light-shielding film 2 by wet etching can be improved.

[0176] Furthermore, based on the results of the electron beam diffraction images described above, it can be confirmed that the lower, middle, and upper regions of the light-shielding film 2 in this embodiment 1 are all polycrystalline structures. Additionally, based on the results of the electron beam diffraction images and cross-sectional TEM images described above, it can be confirmed that the lower, middle, and upper regions of the light-shielding film 2 in this embodiment 1 all have columnar structures.

[0177] The interplanar spacing d = 0.220 nm in the lower region, d = 0.219 nm in the middle region, and d = 0.216 nm in the upper region of the light-shielding film 2 in this embodiment 1, obtained by electron diffraction, are all greater than 0.2 nm.

[0178] Next, using the remaining third mask blank 10 from Example 1, according to the above... Figure 3 The manufacturing process shown produces a transfer mask 20.

[0179] First, a positive resist for laser tracing (TMHR-iP3500 manufactured by Tokyo Ohka Kogyo) is applied to the upper surface of the aforementioned mask blank 10 by spin coating, followed by a baking process to form a resist film 3 with a thickness of 300 nm (see reference). Figure 3 (a)).

[0180] Next, using a laser patterning machine, a given device pattern (corresponding to the transfer pattern to be formed on the light-shielding film 2) is drawn on the resist film 3. Then, the resist film is developed to form the resist pattern 3a (see reference). Figure 3 (b) and (c)).

[0181] Next, using the aforementioned resist pattern 3a as a mask, wet etching of the light-shielding film 2 is performed, forming a light-shielding film pattern (transfer pattern) 2a on the light-shielding film 2 (see reference). Figure 3 (d)). An aqueous solution obtained by adding perchloric acid to cerium ammonium nitrate was used as the etching solution for wet etching. It should be noted that the etching rate of each region of the light-shielding film 2 was measured during wet etching. The results showed that the etching rate was 1.7 nm / sec in the lower region, 1.5 nm / sec in the middle region, and 2.3 nm / sec in the upper region. That is, it can be seen that the wet etching rate of the light-shielding film 2 in Example 1 increases in the order of the middle region, lower region, and upper region.

[0182] Finally, the remaining resist pattern 3a is removed, thereby creating the transfer mask 20 of Embodiment 1 (see reference 1) having a light-shielding film pattern 2a that serves as a transfer pattern on the light-transmitting substrate 1. Figure 3 (e)).

[0183] As described above, in the mask blank of this embodiment 1, by increasing the crystal size of the light-shielding film 2 in the order of the middle region, lower region, and upper region, the etching rate of wet etching of each region within the light-shielding film 2 can be increased in the order of the middle region, lower region, and upper region. This improves the perpendicularity of the pattern sidewalls when forming a pattern on the light-shielding film 2 by wet etching. As a result, the transfer mask 20 manufactured from the mask blank of this embodiment 1 forms a transfer pattern with improved perpendicularity of the pattern sidewalls and a good cross-sectional shape.

[0184] Furthermore, the transfer mask 20 of Embodiment 1 is placed on the mask stage of an exposure apparatus that uses i-rays as exposure light, and exposure light is irradiated from the transparent substrate 1 side of the transfer mask 20 to expose and transfer the pattern onto the resist film of the semiconductor device. Then, a given process is performed on the exposed and transferred resist film to form a resist pattern, which is observed using a CD-SEM (Critical Dimension Scanning Electron Microscope). As a result, it can be confirmed that the resist pattern was formed with high CD (Critical Dimension) precision. Based on the above, it can be said that the transfer mask 20 manufactured from the mask blank 10 of Embodiment 1 can also expose and transfer the resist film on the semiconductor device with high precision.

[0185] (Example 2)

[0186] The mask blank 10 of Example 2 is manufactured as described below.

[0187] Similar to Example 1, three light-transmitting substrates 1 (approximately 152 mm × 152 mm × approximately 6.35 mm thick) made of synthetic quartz glass were prepared. The main surface and end face of the light-transmitting substrate were ground to a given surface roughness (e.g., the main surface roughness was less than 0.2 nm in terms of root mean square roughness Rq).

[0188] Next, using the following method, a light-shielding film 2 consisting of a lower region, a middle region, and an upper region was formed on the three light-transmitting substrates 1 described above.

[0189] First, a tandem sputtering apparatus with multiple chromium (Cr) targets arranged in the transport direction of the transparent substrate 1 was prepared in the sputtering chamber. Inside this sputtering chamber, while transporting the transparent substrate 1, a mixture of argon (Ar) and nitrogen (N2) gas (flow rate ratio Ar:N2 = 9:4, pressure = 3.0 × 10⁻⁶) was applied. -4 In an atmosphere of Pa, a voltage is applied to a Cr target under constant current control of 1.6A to perform reactive sputtering (DC sputtering), thereby forming the lower region of the light-shielding film 2 on the light-transmitting substrate 1.

[0190] Next, within the sputtering chamber, while transporting the film to the light-transmitting substrate 1 in the lower region, a mixture of argon (Ar) and methane (CH4) gas (flow rate ratio Ar:CH4 = 30:1, pressure = 3.0 × 10⁻⁶) is applied. -4 In an atmosphere of Pa, a voltage is applied to the Cr target under constant current control of 2.5A to perform reactive sputtering (DC sputtering), thereby grounding the middle region with the lower region of the light-shielding film 2.

[0191] Next, within the sputtering chamber, a light-transmitting substrate 1, formed to the central region, is transported while a mixture of argon (Ar) and nitric oxide (NO) gas (flow rate ratio Ar:NO = 100:4, pressure = 3.0 × 10⁻⁶) is applied. -4 In an atmosphere of 0 Pa, a voltage is applied to a Cr target under constant current control, and reactive sputtering (DC sputtering) is performed, thereby grounding the upper region to the middle region of the light-shielding film 2. Using the above method, a mask blank 10 of Embodiment 2, which has a light-shielding film 2 consisting of a lower region, a middle region, and an upper region on the light-transmitting substrate 1, is produced.

[0192] It should be noted that the optical density of the light-shielding film 2 in this embodiment 2 is 3.0 or higher under light of a wavelength (365nm) such as i-rays.

[0193] Next, the light-shielding film 2 of the mask blank 10 of the first embodiment 2 was analyzed using X-ray photoelectron spectroscopy (XPS). The results showed that the film thickness of the light-shielding film 2 was 71 nm, and the film thickness and composition of each region were as follows: lower region (film thickness approximately 21 nm, composition Cr:C:N = 72 atomic%: 2 atomic%: 26 atomic%), middle region (film thickness approximately 32 nm, composition Cr:C:O:N = 82 atomic%: 6 atomic%: 1 atomic%: 11 atomic%), and upper region (film thickness approximately 18 nm, composition Cr:O:N = 55 atomic%: 25 atomic%: 20 atomic%).

[0194] Next, cross-sectional TEM images of the light-shielding film 2 of the mask blank 10 of the second embodiment 2 were observed, and the crystallinity was observed using electron diffraction. Figure 8 An electron beam diffraction image of the upper region of the light-shielding film 2 in the mask blank 10 of Example 2 is shown. Figure 9 The image shows an electron beam diffraction pattern of the central region of the light-shielding film 2 in the mask blank 10 of Example 2. Additionally, Figure 10 The image shows an electron beam diffraction pattern of the lower region of the light-shielding film 2 in the mask blank 10 of Example 2.

[0195] in addition, Figure 11 A cross-sectional TEM image of the light-shielding film in the mask blank of Example 2 is shown.

[0196] exist Figure 8 In the electron beam diffraction image of the upper region of the light-shielding film 2 shown, the crystallinity is good, and the diffraction pattern is clear. The grains are large, thus clearly displaying the diffraction pattern. The upper region has the largest grains among the three regions.

[0197] exist Figure 9 In the electron beam diffraction pattern of the central region of the light-shielding film 2 shown, the crystallinity is low, and the diffraction pattern is not very clear. The central region has the smallest grain size among the three regions.

[0198] It can be known that in Figure 10 In the electron beam diffraction image of the lower region of the light-shielding film 2 shown, and... Figure 9 Compared to the central region, lattice points are clearly observed, and the grains are larger compared to the central region.

[0199] Based on the above, it can be confirmed that the crystal size of the light-shielding film 2 in the mask blank 10 of this embodiment 2 increases in the order of the middle region, the lower region, and the upper region. Therefore, the etching rate of wet etching for each region within the light-shielding film 2 can increase in the order of the middle region, the lower region, and the upper region. Consequently, the overall etching rate of the light-shielding film 2 in the mask blank of this embodiment 2 is improved, and the perpendicularity of the pattern sidewalls when forming patterns on the light-shielding film 2 by wet etching can be improved.

[0200] Furthermore, based on the results of the electron beam diffraction images, it can be confirmed that the lower, middle, and upper regions of the light-shielding film 2 in this embodiment 2 are all polycrystalline structures. Additionally, based on the results of the electron beam diffraction images and cross-sectional TEM images, it can be confirmed that the lower, middle, and upper regions of the light-shielding film 2 in this embodiment 2 all have columnar structures.

[0201] Furthermore, the interplanar spacing d = 0.212 nm in the lower region, d = 0.220 nm in the middle region, and d = 0.248 nm in the upper region of the light-shielding film 2 of this embodiment 2 obtained by electron diffraction are all greater than 0.2 nm.

[0202] Next, using the third mask blank 10 of this embodiment 2, the same procedure as in embodiment 1 described above is followed. Figure 3 The manufacturing process shown produced a transfer mask 20 having a light-shielding film pattern 2a, which serves as the transfer pattern, on a light-transmitting substrate 1. It should be noted that during wet etching of the light-shielding film 2, the etching rate of each region of the light-shielding film 2 was measured. The results showed that the etching rate was 1.3 nm / sec in the lower region, 1.2 nm / sec in the middle region, and 1.8 nm / sec in the upper region. That is, it can be seen that the wet etching rate of the light-shielding film in this embodiment 2 increases in the order of the middle region, lower region, and upper region.

[0203] For the mask blank 10 of this embodiment 2, by increasing the crystal size of the light-shielding film 2 in the order of the middle region, the lower region, and the upper region, the etching rate of wet etching of each region within the light-shielding film 2 can be increased in the order of the middle region, the lower region, and the upper region. Therefore, the transfer mask 20 manufactured from the mask blank 10 of this embodiment 2 forms a transfer pattern with improved verticality of the pattern sidewalls and a good cross-sectional shape.

[0204] Furthermore, the transfer mask 20 of Embodiment 2 is placed on the mask stage of an exposure apparatus that uses i-rays as exposure light, and exposure light is irradiated from the transparent substrate 1 side of the transfer mask 20 to expose and transfer the pattern onto the resist film of the semiconductor device. Then, a given process is performed on the exposed and transferred resist film to form a resist pattern, which is observed by CD-SEM. As a result, it can be confirmed that the resist pattern is formed with high CD accuracy. Based on the above, it can be said that the transfer mask 20 manufactured from the mask blank 10 of Embodiment 2 can also expose and transfer the resist film on the semiconductor device with high accuracy.

[0205] (Example 3)

[0206] The mask blank of the embodiment is manufactured as described below.

[0207] Similar to Example 1, three light-transmitting substrates 1 (approximately 152 mm × 152 mm × approximately 6.35 mm thick) made of synthetic quartz glass were prepared. The main surface and end face of the light-transmitting substrate 1 were ground to a given surface roughness (e.g., the main surface roughness was less than 0.2 nm in terms of Rq).

[0208] Next, a light-shielding film 2, consisting of a lower region, a middle region, and an upper region, was formed on the three light-transmitting substrates 1 using the following method.

[0209] First, a tandem sputtering apparatus with multiple chromium (Cr) targets positioned along the transport direction of the transparent substrate 1 was prepared within the sputtering chamber. Within this sputtering chamber, the transparent substrate 1 was transported while a mixture of argon (Ar) and nitrogen (N2) gas (flow rate Ar:N2 = 4:1, pressure = 4.0 × 10⁻⁶) was applied. -4 In an atmosphere of Pa, a voltage is applied to a Cr target under constant voltage control with a power value of 0.5W to perform reactive sputtering (DC sputtering), thereby forming the lower region of the light-shielding film 2 on the aforementioned light-transmitting substrate 1.

[0210] Next, within the sputtering chamber, while transporting the film-forming material to the lower region of the transparent substrate 1, a mixture of argon (Ar) and methane (CH4) gas (flow rate ratio Ar:CH4 = 17:1, pressure = 4.0 × 10⁻⁶) is applied. -4 In an atmosphere of 5 Pa, a voltage is applied to the Cr target under constant current control of 5 A to perform reactive sputtering (DC sputtering), thereby grounding the middle region with the lower region of the light-shielding film 2.

[0211] Next, within the sputtering chamber, a light-transmitting substrate 1, formed to the central region, is transported while a mixture of argon (Ar) and nitric oxide (NO) gas (flow rate ratio Ar:NO = 11:2, pressure = 4.0 × 10⁻⁶) is applied.-4 In an atmosphere of Pa, a voltage is applied to a Cr target under constant current control to perform reactive sputtering (DC sputtering), thereby grounding the upper region to the middle region of the light-shielding film 2. Using the above method, a mask blank 10 of Example 3 was fabricated, which has a light-shielding film 2 consisting of a lower region, a middle region, and an upper region on the above-mentioned light-transmitting substrate.

[0212] It should be noted that the optical density of the light-shielding film 2 in this embodiment 3 is, for example, 3.0 or higher under light at the wavelength (365nm) of i-rays.

[0213] Next, the light-shielding film of the mask blank 10 of the first embodiment 3 was analyzed using X-ray photoelectron spectroscopy (XPS). The results showed that the film thickness of the light-shielding film 2 was 100 nm, and the film thickness and composition of each region were as follows: lower region (film thickness approximately 12 nm, composition Cr:C:N = 78 atomic%:10 atomic%:12 atomic%), middle region (film thickness approximately 58 nm, composition Cr:C:O:N = 65 atomic%:10 atomic%:5 atomic%:20 atomic%), and upper region (film thickness approximately 30 nm, composition Cr:C:O:N = 50 atomic%:5 atomic%:20 atomic%:25 atomic%).

[0214] Next, cross-sectional TEM images of the light-shielding film of the second mask blank 10 of this embodiment 3 were observed, and the crystallinity was observed using electron diffraction. Figure 12 An electron beam diffraction image of the upper region of the light-shielding film 2 in the mask blank 10 of Example 3 is shown. Figure 13 The image shows an electron beam diffraction pattern of the central region of the light-shielding film 2 in the mask blank 10 of Example 3. Additionally, Figure 14 The image shows an electron beam diffraction pattern of the lower region of the light-shielding film 2 in the mask blank 10 of Example 3.

[0215] in addition, Figure 15 The image shows a cross-sectional TEM (transmission electron microscope) image of the light-shielding film 2 in the mask blank 10 of Example 3.

[0216] exist Figure 12 In the electron beam diffraction image of the upper region of the light-shielding film 2 shown, the crystallinity is good, and the diffraction pattern is clear. The grains are large, thus clearly displaying the diffraction pattern. The upper region has the largest grains among the three regions.

[0217] It can be known that in Figure 13 In the electron beam diffraction image of the central region of the light-shielding film 2 shown, and... Figure 14 Compared to the lower region, lattice points are clearly observed, and the grains are larger compared to the lower region.

[0218] exist Figure 14In the electron beam diffraction pattern of the lower region of the light-shielding film 2 shown, the crystallinity is low, and the diffraction pattern is not very clear. It is considered possible that the lower region has the smallest grain size among the three regions, but this is not consistent with... Figure 13 The differences in the central region are small.

[0219] Based on the above, it can be confirmed that, regarding the crystal size of the light-shielding film 2 in the mask blank 10 of this embodiment 3, the crystal size of the upper region is larger than that of the middle and lower regions. Therefore, in terms of the wet etching rate of each region within the light-shielding film 2, the upper region can be faster than the middle and lower regions. Consequently, the overall etching rate of the light-shielding film 2 in the mask blank of this embodiment 3 is improved, and the perpendicularity of the pattern sidewalls when forming patterns on the light-shielding film 2 by wet etching can be improved.

[0220] Furthermore, based on the results of the electron beam diffraction images described above, it can be confirmed that the lower, middle, and upper regions of the light-shielding film 2 in this embodiment 3 are all polycrystalline structures. Additionally, based on the results of the electron beam diffraction images and cross-sectional TEM images described above, it can be confirmed that the lower, middle, and upper regions of the light-shielding film 2 in this embodiment 3 all have columnar structures.

[0221] Furthermore, the interplanar spacing d = 0.233 nm in the lower region, 0.223 nm in the middle region, and 0.208 nm in the upper region of the light-shielding film 2 in this embodiment 3, obtained by electron diffraction, are all greater than 0.2 nm.

[0222] Next, using the third mask blank 10 of this embodiment 3, the same procedure as in embodiment 1 described above is followed. Figure 3 The manufacturing process shown produces a transfer mask 20 having a light-shielding film pattern 2a, which serves as the transfer pattern, on a light-transmitting substrate 1. It should be noted that during wet etching of the light-shielding film 2, the etching rate of each region of the light-shielding film 2 was measured. The results showed that the etching rate was 1.4 nm / sec in the lower region, 1.7 nm / sec in the middle region, and 2.3 nm / sec in the upper region. That is, it can be seen that the wet etching rate of the light-shielding film in this embodiment 3 increases in the order of the lower region, middle region, and upper region.

[0223] For the mask blank 10 of this embodiment 3, the crystal size of the light-shielding film 2 is set such that the crystal size of the upper region is larger than that of the middle and lower regions. As a result, the etching rate of the upper region can be faster than that of the middle and lower regions in terms of wet etching of each region within the light-shielding film. Therefore, the transfer mask 20 manufactured from the mask blank 10 of this embodiment 3 forms a transfer pattern with improved verticality of the pattern sidewalls and a good cross-sectional shape.

[0224] Furthermore, the transfer mask 20 of Embodiment 3 is placed on the mask stage of an exposure apparatus that uses i-rays as exposure light, and exposure light is irradiated from the transparent substrate 1 side of the transfer mask 20 to expose and transfer the pattern onto the resist film of the semiconductor device. Then, a given process is performed on the exposed and transferred resist film to form a resist pattern, which is observed by CD-SEM. As a result, it can be confirmed that the resist pattern is formed with high CD accuracy. Based on the above, it can be said that the transfer mask 20 manufactured from the mask blank 10 of Embodiment 3 can also expose and transfer the resist film on the semiconductor device with high accuracy.

[0225] (Comparative Example 1)

[0226] The mask blank of Comparative Example 1 was fabricated as described below.

[0227] Similar to Example 1, three light-transmitting substrates (approximately 152 mm × 152 mm × approximately 6.35 mm thick) made of synthetic quartz glass were prepared. The main surface and end face of the light-transmitting substrate were ground to a given surface roughness (e.g., the main surface roughness was less than 0.2 nm in terms of Rq).

[0228] Next, a light-shielding film consisting of a lower region, a middle region, and an upper region was formed on the three light-transmitting substrates described above using the following method.

[0229] First, a rotating stage for holding the transparent substrate 1 and a single-piece sputtering apparatus with a chromium (Cr) target were prepared in the sputtering chamber. The transparent substrate was placed on the rotating stage in the sputtering chamber, and a mixed gas of argon (Ar), nitrogen (N2), carbon dioxide (CO2), and helium (He) was used (flow rate ratio Ar:N2:CO2:He = 4:3:6:8, pressure = 1.0 × 10⁻⁶). -4 In an atmosphere of Pa, the DC power applied to the Cr target is set to 2.0 kW (constant current control), and reactive sputtering (DC sputtering) is performed, thereby forming the lower region of the light-shielding film on the aforementioned light-transmitting substrate.

[0230] Next, the DC power applied to the Cr target was stopped, and the mixture of argon (Ar), nitric oxide (NO), and helium (He) gas in the sputtering chamber (flow rate ratio Ar:NO:He = 1:1:2, pressure = 1.0 × 10⁻⁶) was released. -4 After the atmosphere of the Pa) was changed to the sputtering gas, DC power (power: 2.0kW, constant current control) was applied to the Cr target to perform reactive sputtering (DC sputtering), thereby grounding the middle region with the lower region mentioned above.

[0231] Next, the DC power applied to the Cr target was stopped, and the sputtering chamber was changed to a mixture of argon (Ar), nitrogen (N2), carbon dioxide (CO2), and helium (He) (flow rate ratio Ar:N2:CO2:He = 4:3:8:8, pressure = 1.0 × 10⁻⁶). -4 After applying an atmosphere of Pa, DC power (power: 2.0 kW, constant current control) was applied to the Cr target to perform reactive sputtering (DC sputtering), thereby grounding the upper region with the aforementioned middle region. Using the above method, a mask blank of Comparative Example 1 was fabricated, which has a light-shielding film consisting of a lower region, a middle region, and an upper region on the aforementioned light-transmitting substrate.

[0232] It should be noted that the optical density of the light-shielding film of Comparative Example 1 is, for example, 3.0 or higher at the wavelength (365 nm) of i-rays.

[0233] Next, the light-shielding film of the mask blank of Comparative Example 1 was analyzed using X-ray photoelectron spectroscopy (XPS). The results showed that the film thickness was 86 nm, and the film thickness and composition of each region were as follows: lower region (film thickness approximately 41 nm, composition Cr:C:O:N = 56 atomic%: 11 atomic%: 22 atomic%: 11 atomic%), middle region (film thickness approximately 31 nm, composition Cr:O:N = 85 atomic%: 7 atomic%: 8 atomic%), and upper region (film thickness approximately 14 nm, composition Cr:C:O:N = 47 atomic%: 9 atomic%: 34 atomic%: 10 atomic%).

[0234] Next, cross-sectional TEM images of the light-shielding film of the second mask blank of Comparative Example 1 were observed, and the crystallinity was observed using electron diffraction. Figure 16 An electron beam diffraction image of the upper region of the light-shielding film in the mask blank of Comparative Example 1 is shown. Figure 17 An electron beam diffraction image of the central region of the light-shielding film in the mask blank of Comparative Example 1 is shown. Additionally, Figure 18 An electron beam diffraction image of the lower region of the light-shielding film in the mask blank of Comparative Example 1 is shown.

[0235] in addition, Figure 19 A cross-sectional TEM image of the light-shielding film in the mask blank of Comparative Example 1 is shown.

[0236] It can be known that in Figure 16 In the electron beam diffraction image of the upper region of the light-shielding film shown, no diffraction pattern from the crystalline structure was observed; the upper region is an amorphous structure.

[0237] exist Figure 17 In the electron beam diffraction image of the central region of the light-shielding film shown, the crystallinity is low, and the diffraction image is not very clear.

[0238] It can be known that in Figure 18 In the electron beam diffraction image of the lower region of the light-shielding film shown, and... Figure 17 Compared to the central region, lattice points are clearly visible, and the grains are slightly larger.

[0239] Furthermore, based on the results of the electron beam diffraction images described above, it can be confirmed that the upper region of the light-shielding film of Comparative Example 1 has an amorphous structure, while the lower and middle regions have polycrystalline structures. Additionally, based on the results of the electron beam diffraction images and cross-sectional TEM images described above, it can be confirmed that no columnar structure exists in any region of the light-shielding film of Comparative Example 1.

[0240] Furthermore, the interplanar spacing of the light-shielding film of Comparative Example 1 obtained by electron diffraction is d = 0.217 nm in the lower region and d = 0.218 nm in the middle region.

[0241] Next, using the third mask blank from Comparative Example 1, the process was carried out in the same manner as in Example 1 described above. Figure 3 The manufacturing process shown produces a transfer mask having a light-shielding film pattern, which becomes the transfer pattern, on a light-transmitting substrate. It should be noted that during wet etching of the light-shielding film, the etching rate of each region of the film was measured. The results showed that the lower region had an etching rate of 1.0 nm / sec, the middle region 0.6 nm / sec, and the upper region 0.9 nm / sec. That is, it can be seen that the wet etching rate of the light-shielding film of Comparative Example 1 increases in the order of the middle region, upper region, and lower region. However, it is evident that compared to the light-shielding films 2 of Examples 1-3 described above, the wet etching rate is significantly slower in all regions.

[0242] For the mask blank of Comparative Example 1, the upper region of the light-shielding film is particularly amorphous, therefore, the etching rate for wet etching is significantly slower compared to the upper region of the light-shielding film 2 in Examples 1-3. Therefore, for the aforementioned transfer mask manufactured from the mask blank of Comparative Example 1, the verticality of the pattern sidewalls cannot be improved, making it difficult to form a transfer pattern with a good cross-sectional shape.

[0243] Furthermore, the transfer mask of Comparative Example 1 was placed on the mask stage of an exposure apparatus that uses i-rays as the exposure light, and the exposure light was irradiated from the transparent substrate side of the transfer mask to expose and transfer the pattern onto the resist film of the semiconductor device. Then, a given process was performed on the exposed resist film to form a resist pattern, which was observed using CD-SEM. The results showed that the CD accuracy of the resist pattern was low. Based on this result, it can be concluded that when the transfer mask manufactured from the mask blank of Comparative Example 1 is placed on the mask stage of an exposure apparatus and the resist film on the semiconductor device is exposed and transferred, it is ultimately difficult to form a circuit pattern on the semiconductor device with high accuracy.

Claims

1. A mask blank comprising a substrate and a pattern forming film on the substrate, the film is formed of a material containing chromium, the film is composed of an upper region on the side opposite to the substrate side and a region other than the upper region, the crystal size of the upper region is larger than that of the region other than the upper region, the etching rate of the upper region is faster than that of the region other than the upper region in the case where an etching solution using ammonium cerous nitrate as a main component is used.

2. The mask blank according to claim 1, wherein the upper region and the region other than the upper region of the film are both polycrystal structures.

3. The mask blank according to claim 1 or 2, wherein each interplanar spacing of the upper region and the region other than the upper region of the film obtained by electron diffraction method is 0.2 nm or more.

4. The mask blank according to claim 1 or 2, wherein the upper region and the region other than the upper region of the film are both columnar structures.

5. The mask blank according to claim 1 or 2, wherein, the region other than the upper region of the film is composed of a lower region and a middle region from the substrate side, the crystal size of the film becomes larger in the order of the middle region, the lower region, and the upper region.

6. The mask blank according to claim 1 or 2, wherein the film is a composition gradient film in which the content of the chromium changes in the thickness direction.

7. The mask blank according to claim 1 or 2, wherein the film is a light shielding film having an optical density of 3 or more for exposure light.

8. A transfer mask comprising a substrate and a film having a transfer pattern on the substrate, the film is formed of a material containing chromium, the film is composed of an upper region on the side opposite to the substrate side and a region other than the upper region, the crystal size of the upper region is larger than that of the region other than the upper region, the etching rate of the upper region is faster than that of the region other than the upper region in the case where an etching solution using ammonium cerous nitrate as a main component is used.

9. The transfer mask according to claim 8, wherein the upper region and the region other than the upper region of the film are both polycrystal structures.

10. The transfer mask according to claim 8 or 9, wherein each interplanar spacing of the upper region and the region other than the upper region of the film obtained by electron diffraction method is 0.2 nm or more.

11. The transfer mask according to claim 8 or 9, wherein the upper region and the region other than the upper region of the film are both columnar structures.

12. The transfer mask according to claim 8 or 9, wherein the region other than the upper region of the film is composed of a lower region and a middle region from the substrate side, the crystal size of the film becomes larger in the order of the middle region, the lower region, and the upper region.

13. The transfer mask according to claim 8 or 9, wherein the film is a composition gradient film in which the content of the chromium changes in the thickness direction.

14. The transfer mask according to claim 8 or 9, wherein The film is a light shielding film having an optical density of 3 or more for exposure light.

15. A method of manufacturing a semiconductor device, the method comprising: a step of exposing and transferring a transfer pattern to a resist film on a semiconductor substrate using the transfer mask according to any one of claims 8 to 14.

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