Manufacturing methods for mask blanks, transfer masks, and semiconductor devices

Abstract

This invention provides a mask blank, a transfer mask, and a method for manufacturing a semiconductor device. The mask blank (100) has a light-shielding film (2) on a light-transmitting substrate (1). The light-shielding film is characterized by having a structure in which a lower layer and an upper layer are stacked sequentially from the light-transmitting substrate side. The lower layer is formed of a material containing silicon and nitrogen, and the upper layer is formed of a material containing silicon and oxygen. The optical density for ArF exposure light is 2.5 or more, the surface reflectance is 30% or less, the back reflectance is 40% or less, the transmittance for light with a wavelength of 900 nm is 50% or less, the extinction coefficient of the lower layer for light with a wavelength of 900 nm is 0.04 or more, and the thickness is 60 nm or less.

Description

[0001] This application is a divisional application of the invention patent application filed on August 2, 2017, with application number 201780050886.2 and entitled "Mask blank, transfer mask and method for manufacturing semiconductor device". Technical Field

[0002] This invention relates to a mask blank and a transfer mask manufactured using the mask blank. Furthermore, this invention relates to a method for manufacturing a semiconductor device using the aforementioned transfer mask. Background Technology

[0003] In the manufacturing process of semiconductor devices, photolithography is used to form fine patterns. When miniaturizing the patterns in semiconductor devices, in addition to miniaturizing the mask pattern formed on the transfer mask, it is also necessary to shorten the wavelength of the exposure light source used in photolithography. In recent years, ArF excimer lasers (wavelength 193nm) have been increasingly used as exposure light sources in the manufacture of semiconductor devices.

[0004] Among transfer masks, there is a binary mask. For example, the binary mask described in Patent Document 1 is a transfer mask in which a light-shielding film pattern for blocking exposure light is formed on a light-transmitting substrate. Chromium (Cr) or molybdenum silicide (MoSi) based materials are widely used as the light-shielding film.

[0005] When the light-shielding film is made of chromium-based materials, it is difficult to dry-etch the light-shielding film with sufficient anisotropy and form a fine light-shielding film pattern with sufficient precision because the mixed gas of chlorine and oxygen used in the dry etching of the film has high radical properties.

[0006] When using molybdenum silicide (MoSi) based materials as the light-shielding film material, the aforementioned dry etching method has fewer problems and can easily form fine light-shielding film patterns with high precision. However, on the other hand, it has been found in recent years that MoSi based films have low resistance to ArF excimer laser exposure light (ArF exposure light) (so-called ArF lightfastness).

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2007-33470 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] It has been confirmed that high ArF light resistance is achieved when silicon and nitrogen-containing materials are used in phase-shifting films. Therefore, the possibility of obtaining high ArF light resistance by using a thin film (SiNx film) containing silicon and nitrogen as a binary mask for light-shielding film was investigated. However, studies have shown that the following problems exist when forming a light-shielding film using a monolayer SiNx film.

[0012] Generally, in binary masks, the light-shielding film with the transfer pattern is required to have a specified optical density (e.g., 2.5 or higher) for the exposure light (hereinafter referred to as ArF exposure light) emitted from the exposure apparatus by an ArF excimer laser. Furthermore, the light-shielding film is required to have a specified reflectance (backside reflectance, e.g., 40% or less) for the ArF exposure light incident on the surface adjacent to the transparent substrate, and a specified reflectance (surface reflectance, e.g., 40% or less) for the ArF exposure light incident on the opposite side of the transparent substrate. From the perspective of the required optical density of the light-shielding film, the less nitrogen contained in the SiNx film, the better. However, from the perspective of the required surface and backside reflectance of the light-shielding film, the SiNx film needs to contain a certain amount of nitrogen.

[0013] Some exposure apparatuses use long-wavelength light (800nm-900nm) to detect alignment marks before performing the exposure operation. This long-wavelength light is referred to here as long-wavelength detection light (LW). When a binary mask consisting of a single-layer SiNx film is placed in an exposure apparatus using long-wavelength detection light (LW) for exposure, the problem of insufficient detection sensitivity of the alignment marks has repeatedly occurred, preventing the exposure operation from proceeding.

[0014] If the nitrogen content of the SiNx film constituting the light-shielding film is significantly reduced, the transmittance of long-wavelength light can be decreased, eliminating the problem of insufficient detection sensitivity of alignment marks. However, this light-shielding film has higher surface and back reflectivity for ArF exposure light, thus introducing a new problem of significantly reduced transfer performance as a binary mask.

[0015] The objective of this invention is to provide a mask blank having a light-shielding film that not only meets the requirements for various optical properties of ArF exposure light, but also solves the problem of insufficient sensitivity when using long-wavelength light with wavelengths between 800 nm and 900 nm for marking and detection. This invention provides a mask blank having a light-shielding film composed of a single-layer SiNx film. Furthermore, the objective of this invention is to provide a transfer mask manufactured using this mask blank. Moreover, the objective of this invention is to provide a method for manufacturing a semiconductor device using this transfer mask.

[0016] Technical solutions for solving the problem

[0017] To address the aforementioned issues, the present invention has the following features.

[0018] (Technical Solution 1)

[0019] A mask blank having a light-shielding film on a light-transmitting substrate, characterized in that,

[0020] The light-shielding film has a structure in which the lower and upper layers are stacked sequentially from the light-transmitting substrate side.

[0021] The lower layer is formed of a material containing silicon and nitrogen.

[0022] The upper layer is formed of a material containing silicon and oxygen.

[0023] The light-shielding film has an optical density of 2.5 or higher for ArF exposure light.

[0024] The light-shielding film has a surface reflectance of less than 30% to ArF exposure light.

[0025] The light-shielding film has a back reflectance of less than 40% for ArF exposure light.

[0026] The light-shielding film has a transmittance of less than 50% for light with a wavelength of 900nm.

[0027] The lower layer of the light-shielding film has an extinction coefficient k of 0.04 or higher for light with a wavelength of 900nm.

[0028] The thickness of the light-shielding film is less than 60 nm.

[0029] (Technical Solution 2)

[0030] The mask blank as described in technical solution 1 is characterized in that,

[0031] The lower layer of the light-shielding film is formed using a material composed of silicon and nitrogen, or using a material composed of silicon, nitrogen, and one or more elements selected from semi-metallic elements and non-metallic elements other than silicon and nitrogen.

[0032] (Technical Solution 3)

[0033] The mask blank as described in technical solution 1 or 2 is characterized in that,

[0034] The upper layer of the light-shielding film is formed using a material composed of silicon and oxygen, or using a material composed of silicon, oxygen, and one or more elements selected from semi-metallic elements and non-metallic elements other than silicon and oxygen.

[0035] (Technical Solution 4)

[0036] The mask blank as described in technical solution 1 or 2 is characterized in that,

[0037] The lower layer of the light-shielding film has an extinction coefficient k of 0.10 or higher for light with a wavelength of 700nm.

[0038] (Technical Solution 5)

[0039] The mask blank as described in technical solution 1 or 2 is characterized in that,

[0040] The lower layer of the light-shielding film has a refractive index n of less than 3.5 for light with a wavelength of 900nm.

[0041] (Technical Solution 6)

[0042] The mask blank as described in technical solution 1 or 2 is characterized in that,

[0043] The lower layer of the light-shielding film has a refractive index n of less than 3.8 for light with a wavelength of 700nm.

[0044] (Technical Solution 7)

[0045] The mask blank as described in technical solution 1 or 2 is characterized in that,

[0046] The lower layer of the light-shielding film has a refractive index n of 1.6 or higher and 2.1 or lower for ArF exposure light.

[0047] (Technical Solution 8)

[0048] The mask blank as described in technical solution 1 or 2 is characterized in that,

[0049] The lower layer of the light-shielding film has an extinction coefficient k of 1.6 or higher and 2.1 or lower for ArF exposure light.

[0050] (Technical Solution 9)

[0051] The mask blank as described in technical solution 1 or 2 is characterized in that,

[0052] The light-shielding film has a rigid mask film made of a chromium-containing material.

[0053] (Technical Solution 10)

[0054] A transfer mask having a light-shielding film with a transfer pattern on a light-transmitting substrate, characterized in that...

[0055] The light-shielding film has a structure in which the lower and upper layers are stacked sequentially from the light-transmitting substrate side.

[0056] The lower layer is formed of a material containing silicon and nitrogen.

[0057] The upper layer is formed of a material containing silicon and oxygen.

[0058] The light-shielding film has an optical density of 2.5 or higher for ArF exposure light.

[0059] The light-shielding film has a surface reflectance of less than 30% to ArF exposure light.

[0060] The light-shielding film has a back reflectance of less than 40% for ArF exposure light.

[0061] The light-shielding film has a transmittance of less than 50% for light with a wavelength of 900nm.

[0062] The lower layer of the light-shielding film has an extinction coefficient k of 0.04 or higher for light with a wavelength of 900nm.

[0063] The thickness of the light-shielding film is less than 60 nm.

[0064] (Technical Solution 11)

[0065] The transfer mask as described in technical solution 10 is characterized in that,

[0066] The lower layer of the light-shielding film is formed using a material composed of silicon and nitrogen, or using a material composed of silicon, nitrogen, and one or more elements selected from semi-metallic elements and non-metallic elements other than silicon and nitrogen.

[0067] (Technical Solution 12)

[0068] The transfer mask as described in technical solution 10 or 11 is characterized in that,

[0069] The upper layer of the light-shielding film is formed using a material composed of silicon and oxygen, or using a material composed of silicon, oxygen, and one or more elements selected from semi-metallic elements and non-metallic elements other than silicon and oxygen.

[0070] (Technical Solution 13)

[0071] The transfer mask as described in technical solution 10 or 11 is characterized in that,

[0072] The lower layer of the light-shielding film has an extinction coefficient k of 0.10 or higher for light with a wavelength of 700nm.

[0073] (Technical Solution 14)

[0074] The transfer mask as described in technical solution 10 or 11 is characterized in that,

[0075] The lower layer of the light-shielding film has a refractive index n of less than 3.5 for light with a wavelength of 900nm.

[0076] (Technical Solution 15)

[0077] The transfer mask as described in technical solution 10 or 11 is characterized in that,

[0078] The lower layer of the light-shielding film has a refractive index n of less than 3.8 for light with a wavelength of 700nm.

[0079] (Technical Solution 16)

[0080] The transfer mask as described in technical solution 10 or 11 is characterized in that,

[0081] The lower layer of the light-shielding film has a refractive index n of 1.6 or higher and 2.1 or lower for ArF exposure light.

[0082] (Technical Solution 17)

[0083] The transfer mask as described in technical solution 10 or 11 is characterized in that,

[0084] The lower layer of the light-shielding film has an extinction coefficient k of 1.6 or higher and 2.1 or lower for ArF exposure light.

[0085] (Technical Solution 18)

[0086] A method for manufacturing a semiconductor device, characterized in that,

[0087] The process includes using a transfer mask as described in any one of technical solutions 10 to 17 to expose and transfer a transfer pattern onto a resist film on a semiconductor substrate.

[0088] Invention Effects

[0089] The mask blank of the present invention has a light-shielding film formed from a material containing silicon and nitrogen, with a transmittance of less than 50% for light with a wavelength of 900 nm and an extinction coefficient k of 0.04 or higher. In addition to its high ArF lightfastness, the silicon and nitrogen-containing material also exhibits the characteristic that for light with wavelengths between 800 nm and 900 nm, the longer the wavelength, the higher the transmittance and the smaller the extinction coefficient k. Due to these optical properties, when the transmittance of light with a wavelength of 900 nm is less than 50% and the extinction coefficient is 0.04 or higher, sufficient extinction of the long-wavelength detection light (LW) can be achieved. Therefore, the long-wavelength detection light (LW) can be used to detect alignment marks formed on the transfer mask manufactured using this mask blank with sufficient contrast, solving the problem of insufficient sensitivity in detecting alignment marks preventing exposure.

[0090] Furthermore, the light-shielding film of the mask blank of the present invention has an optical density of 2.5 or more for ArF excimer laser exposure light, a surface reflectivity of 40% or less, and a back reflectivity of 40% or less. Therefore, it has sufficient exposure transfer characteristics for pattern exposure light.

[0091] Furthermore, the thickness of the light-shielding film is less than 60 nm, thus enabling the deviations caused by the electromagnetic field effect of the mask pattern (EMF deviation) and the shadowing effect caused by the three-dimensional structure of the mask pattern to be contained within an acceptable range. In addition, because it is a thin film, it is easy to form fine light-shielding film patterns.

[0092] Moreover, because the light-blocking film is a single layer, there are fewer steps involved in its manufacture, making quality control, including defect management, easier.

[0093] Furthermore, regarding the transfer mask of the present invention, the light-shielding film with the transfer pattern has the same characteristics as the light-shielding film of the mask blank described above. With this transfer mask, in addition to solving the problem of high ArF lightfastness of the light-shielding film with the transfer pattern, the problem of being unable to perform exposure due to insufficient sensitivity of the alignment mark detection can also be solved. Attached Figure Description

[0094] Figure 1 This is a cross-sectional view showing the mask blank structure according to an embodiment of the present invention.

[0095] Figure 2 This is a characteristic graph showing the wavelength dependence of the transmittance of the light-shielding film according to an embodiment of the present invention.

[0096] Figure 3 This is a characteristic diagram showing the wavelength dependence of the optical coefficient of the light-shielding film according to an embodiment of the present invention.

[0097] Figure 4 This is a cross-sectional view showing the manufacturing process of a transfer mask according to an embodiment of the present invention. Detailed Implementation

[0098] First, the process of completing this invention will be explained. The inventors conducted an in-depth study on the reasons for the insufficient detection sensitivity of alignment marks using long-wavelength detection light (LW). As a result, the insufficient detection sensitivity of the alignment marks was found to be caused by insufficient optical contrast, which was attributed to the fact that the light-shielding film could not adequately extinct the long-wavelength detection light (LW).

[0099] Therefore, research was conducted on a light-shielding film capable of adequately extinct long-wavelength detection light (LW). The research aimed to ensure its application even when the wavelength of the long-wavelength detection light (LW) varies depending on the exposure device.

[0100] Materials containing silicon and nitrogen exhibiting high ArF lightfastness show higher transmittance for light wavelengths between 800 nm and 900 nm. In other words, they possess a dispersive characteristic where the longer the wavelength, the smaller the extinction coefficient k. Therefore, by specifying the transmittance of a light-shielding film at a wavelength of 900 nm, the film achieves sufficient extinction for long-wavelength detection light (LW). In light of the above, it is believed that by forming a light-shielding film from a silicon and nitrogen-containing material and specifying its transmittance at a wavelength of 900 nm, high ArF lightfastness can be ensured, while simultaneously resolving the problem of poor alignment mark detection.

[0101] In addition, the optical density of the light-shielding film to ArF exposure light, the reflectivity of the surface and back of the exposure light, and the film thickness are specified, so that fine patterns can be transferred.

[0102] Further discussion of the light-shielding film revealed that a single-layer film with fewer processing steps and easier defect and quality management and manufacturing process control can be used to produce a film that meets the above requirements, thus completing the present invention.

[0103] [Mask blank]

[0104] Next, various embodiments of the present invention will be described. Figure 1 This is a cross-sectional view showing the structure of the mask blank 100 according to an embodiment of the present invention. Figure 1 The mask blank 100 shown has a structure in which a light-shielding film 2 and a rigid mask film 3 are stacked sequentially on a light-transmitting substrate 1.

[0105] [Transparent substrate]

[0106] In addition to synthetic quartz glass, the light-transmitting substrate 1 can also be formed of quartz glass, aluminosilicate glass, soda-lime glass, low thermal expansion glass (SiO2-TiO2 glass, etc.). Among them, synthetic quartz glass has high transmittance to ArF exposure light (wavelength 193nm), making it a particularly preferred material for forming the light-transmitting substrate of the mask blank.

[0107] [Light-shielding film]

[0108] The light-shielding film 2 is a single-layer film formed of a material containing silicon and nitrogen. Preferably, it is a single-layer film formed of a material composed of silicon and nitrogen, or a material composed of silicon and nitrogen selected from one or more elements selected from semi-metallic elements and non-metallic elements.

[0109] The light-shielding film 2 does not contain any transition metals that could reduce its lightfastness to ArF exposure light. However, the possibility that metal elements other than transition metals might reduce lightfastness to ArF exposure light cannot be ruled out; therefore, the light-shielding film 2 preferably does not contain any metal elements other than transition metals.

[0110] In addition to silicon, the light-shielding film 2 may also contain any half-metal element. Among the half-metal elements, if one or more elements selected from boron, germanium, antimony and tellurium are included, it is expected to improve the conductivity of silicon used as a sputtering target, and therefore is preferred.

[0111] Besides nitrogen, the light-shielding film 2 may also contain any non-metallic elements. Here, the non-metallic elements of the present invention refer to non-metallic elements in the narrow sense (nitrogen, carbon, oxygen, phosphorus, sulfur, selenium), halogen elements, and rare gases. Among these non-metallic elements, it is preferable to contain one or more elements selected from carbon, fluorine, and hydrogen. Except for the surface region described later, the oxygen content of the light-shielding film 2 is preferably suppressed to 5 atomic percent or less, more preferably 3 atomic percent or less, and even more preferably not actively containing oxygen (below the detection limit value when performing compositional analysis such as XPS (X-ray Photoelectron Spectroscopy)). This is because when oxygen is present in the silicon nitride-based material film, the extinction coefficient k becomes smaller, making it difficult to obtain sufficient light-shielding properties.

[0112] The light-transmitting substrate 1 is preferably made of a material with SiO2 as the main component, such as synthetic quartz glass. When the light-shielding film 2 contains oxygen, the difference between the composition of the light-shielding film 2 and the composition of the light-transmitting substrate 1 becomes smaller. In the dry etching process performed by fluorine-based gas when the pattern is formed on the light-shielding film 2, it is difficult to obtain the same etching selectivity as the light-transmitting substrate 1.

[0113] The light-shielding film 2 may contain a rare gas. The presence of the rare gas within the film-forming chamber during reactive sputtering increases the film-forming speed and improves production efficiency. Due to the plasmaification of this rare gas, it collides with the target material, causing target constituent particles to eject from the target. During this process, the particles capture the reactive gas and deposit on the light-transmitting substrate 1 to form a thin film. During the time the target constituent particles eject from the target and adhere to the light-transmitting substrate 1, a trace amount of rare gas is introduced into the film-forming chamber. Preferred rare gases for reactive sputtering include argon, krypton, and xenon. Furthermore, to alleviate stress on the thin film, small atomic weights such as helium and neon can be actively introduced into the film.

[0114] The nitrogen content of the light-shielding film 2 is preferably 50 atomic% or less, more preferably 45 atomic% or less. This is because when the nitrogen content exceeds 50 atomic%, the extinction coefficient for ArF exposure light and long-wavelength detection light (LW) decreases, making it difficult to achieve sufficient light shading or extinction. Furthermore, the nitrogen content of the light-shielding film 2 is preferably 25 atomic% or more, more preferably 30 atomic% or more. This is because when the nitrogen content is below 25 atomic%, washability is easily insufficient, and oxidation is more likely to occur, easily impairing the film's long-term stability.

[0115] Furthermore, the silicon content of the light-shielding film 2 is preferably 50 atomic% or more, more preferably 55 atomic% or more. This is because when the silicon content is below 50 atomic%, the extinction coefficient for ArF exposure light and long-wavelength detection light (LW) becomes smaller, making it difficult to achieve sufficient light shading or extinction. Additionally, the silicon content of the light-shielding film 2 is preferably 75 atomic% or less, more preferably 65 atomic% or less. This is because when the silicon content exceeds 75 atomic%, washability is easily insufficient, and oxidation is prone to occur, easily compromising the film's long-term stability.

[0116] Preferably, the light-shielding film 2 is formed from a material composed of silicon and nitrogen. Furthermore, rare gases are elements that are difficult to detect even by compositional analysis of the thin film, such as RBS (Rutherford Back-Scattering Spectrometry) or XPS. However, as mentioned above, rare gases are introduced in trace amounts during the formation of the light-shielding film 2 by reactive sputtering. Therefore, it can be considered that the aforementioned material composed of silicon and nitrogen includes materials containing rare gases.

[0117] The thickness of the light-shielding film 2 is required to be 60 nm or less. By setting the thickness of the light-shielding film 2 to 60 nm or less, the deviation caused by the electromagnetic field effect of the mask pattern (EMF deviation) and the shadowing effect caused by the three-dimensional structure of the mask pattern can be contained within an acceptable range. In addition, because it is a thin film, it is easy to form a fine light-shielding film pattern. The thickness of the light-shielding film 2 is more preferably 58 nm or less.

[0118] On the other hand, the thickness of the light-shielding film 2 is preferably 40 nm or more, and more preferably 45 nm or more. When the thickness of the light-shielding film 2 is less than 40 nm, it is difficult to ensure the optical density described below for ArF exposure light, and it is also difficult to obtain sufficient extinction for long-wavelength detection light LW.

[0119] The light-shielding film 2 is required to have an optical density (OD value) of 2.5 or higher for ArF exposure light, preferably 2.8 or higher. When the optical density is lower than 2.5, the light-shielding ability for ArF exposure light is insufficient, and when exposure is performed using a transfer mask using this mask blank, the contrast of the projected optical image (transfer image) is easily insufficient. On the other hand, in order to achieve thin film formation of the light-shielding film 2, it is preferable that the optical density of the light-shielding film 2 is 4.0 or lower.

[0120] The surface reflectance of the light-shielding film 2 to ArF exposure light (the reflectance of the surface on the opposite side of the light-transmitting substrate 1) is required to be 40% or less, preferably 38% or less. When the surface reflectance to ArF exposure light exceeds 40%, excessive reflection of the exposure light will occur, resulting in deterioration of the projected optical image during transfer exposure.

[0121] Furthermore, the preferred light-shielding film 2 has a surface reflectance of 20% or more to ArF exposure light. This is because when the surface reflectance to ArF exposure light is less than 20%, the pattern inspection sensitivity decreases when using light with a wavelength of 193 nm or a wavelength near that.

[0122] The back reflectance (reflectance of the surface on the side of the light-transmitting substrate 1) of the light-shielding film 2 to ArF exposure light is required to be 40% or less, preferably 35% or less. When the back reflectance to ArF exposure light exceeds 40%, excessive reflection of the exposure light will occur, resulting in deterioration of the projected optical image during transfer exposure.

[0123] Since the optical density, surface reflectance, and back reflectance of the light-shielding film 2 for ArF exposure light are set within the range of the above values, it is preferable that the refractive index n of the light-shielding film 2 for ArF exposure light is 1.6 or more and 2.1 or less, more preferably 1.7 or more and 2.0 or less. Furthermore, the extinction coefficient k for ArF exposure light is preferably 1.6 or more and 2.1 or less, more preferably 1.7 or more and 2.0 or less.

[0124] The light-shielding film 2 is required to have a transmittance of 50% or less for light with a wavelength of 900 nm, preferably 48% or less. The extinction coefficient k of the light-shielding film 2 for light with a wavelength of 900 nm is required to be 0.04 or more, preferably 0.045 or more. Furthermore, the extinction coefficient k of the light-shielding film 2 for light with a wavelength of 900 nm is preferably 0.1 or less. The refractive index n of the light-shielding film 2 for light with a wavelength of 900 nm is preferably 2.5 or more, more preferably 2.7 or more. Furthermore, the refractive index n of the light-shielding film 2 for light with a wavelength of 900 nm is preferably 3.5 or less.

[0125] As mentioned above, the light-shielding film 2, made of a material containing silicon and nitrogen, exhibits the characteristic that for light with wavelengths between 800 nm and 900 nm, the longer the wavelength, the higher the transmittance, and the lower the refractive index n and extinction coefficient k. Utilizing this spectral characteristic, when the transmittance for 900 nm wavelength light is 50% or less and the extinction coefficient k is 0.04 or more, the light-shielding film 2 can sufficiently extinct the long-wavelength detection light LW in the wavelength range of 800 nm to 900 nm. Therefore, the long-wavelength detection light LW can be used to detect alignment marks formed on the transfer mask manufactured using this mask blank with sufficient contrast. Thus, the problem of insufficient sensitivity in detecting alignment marks, preventing exposure, can be solved.

[0126] On the other hand, the transmittance of the light-shielding film 2 for light with a wavelength of 700 nm is preferably 45% or less, more preferably 40% or less. The extinction coefficient k of the light-shielding film 2 for light with a wavelength of 700 nm is preferably 0.10 or more, more preferably 0.15 or more. Furthermore, the extinction coefficient k of the light-shielding film 2 for light with a wavelength of 700 nm is preferably 0.5 or less. Furthermore, the refractive index n of the light-shielding film 2 for light with a wavelength of 700 nm is preferably 2.8 or more, more preferably 3.0 or more. Furthermore, the refractive index n of the light-shielding film 2 for light with a wavelength of 700 nm is preferably 3.8 or less.

[0127] Using an exposure apparatus, identification marks such as barcodes formed on a transfer mask can be read using detection light with a wavelength shorter than 800 nm (e.g., wavelengths in the range of 600 nm to 700 nm). A transfer mask manufactured using a mask blank having the aforementioned optical properties of a light-shielding film 2 with a wavelength of 700 nm can reliably read identification codes using the aforementioned detection light with a wavelength shorter than 800 nm.

[0128] The refractive index n and extinction coefficient k of a thin film are not solely determined by its composition. The film density and crystallinity state are also factors influencing the refractive index n and extinction coefficient k. Therefore, the conditions for forming the light-shielding film 2 via reactive sputtering are adjusted to achieve the desired refractive index n and extinction coefficient k, thereby converging the optical density (OD value), back reflectance, surface reflectance, and extinction coefficient k for ArF exposure light to predetermined values. Setting the light-shielding film 2 within the aforementioned range of refractive index n and extinction coefficient k is not limited to adjusting the ratio of the rare gas and reactive gas mixture during reactive sputtering. It is related to many factors, such as the pressure within the film-forming chamber during reactive sputtering, the power applied to the target, and the positional relationship between the target and the transparent substrate. Furthermore, these film-forming conditions are inherent to the film-forming apparatus and can be appropriately adjusted to ensure that the formed light-shielding film 2 has the desired refractive index n and extinction coefficient k.

[0129] The light-shielding film 2 can be a single-layer film composed of a film with a uniform composition in the thickness direction, except for the surface layer that undergoes natural oxidation, or a film with an inclined composition. By making it a single-layer film, the number of manufacturing steps is reduced, production efficiency is improved, and manufacturing quality management, including defective products, becomes easier.

[0130] Films containing silicon and nitrogen but not actively containing oxygen exhibit high lightfastness to ArF exposure light, but tend to have lower chemical resistance compared to films containing silicon and nitrogen but actively containing oxygen. Furthermore, when using a mask blank 100 containing a light-shielding film 2 that is the surface layer opposite to the light-transmitting substrate 1 of the light-shielding film 2, oxidation of the surface layer of the light-shielding film 2 is unavoidable due to the need for mask cleaning or atmospheric storage of the transfer mask 200 made from the mask blank 100. If the surface layer of the light-shielding film 2 oxidizes, the surface reflectivity of the light-shielding film 2 to ArF exposure light changes, leading to alterations in the exposure transfer characteristics of the transfer mask 200.

[0131] Therefore, it is preferable that the surface layer on the opposite side of the light-transmitting substrate 1 of the light-shielding film 2 actively contains oxygen. However, on the other hand, if the light-shielding film 2 contains oxygen as a whole, as mentioned above, there will be a problem of reduced light-shielding performance for ArF exposure light or reduced extinction performance for long-wavelength detection light LW.

[0132] Therefore, preferably, the light-shielding film 2 has a sloping portion on its surface, the surface of which, facing the light-transmitting substrate 1, increases the oxygen content. The portion of the light-shielding film 2 other than its surface (the volume portion of the light-shielding film 2) is formed using a material composed of silicon and nitrogen. Here, the silicon and nitrogen material constituting the volume portion of the light-shielding film 2 is either a material composed of silicon and nitrogen, or a material composed of silicon and nitrogen composed of one or more elements selected from half-metallic and non-metallic elements. Furthermore, in this case, the refractive index n and extinction coefficient k of the light-shielding film 2 for ArF exposure light are both values ​​of the entire light-shielding film 2 including the surface layer, and its extinction coefficient k for light with a wavelength of 900 nm is also a value of the entire light-shielding film 2 including the surface layer.

[0133] The light-shielding film 2 is formed by sputtering, but any sputtering method such as DC sputtering, RF sputtering, and ion beam sputtering can also be used. When using a target material with low conductivity (silicon target material, silicon compound target material without half-metal elements or with low half-metal element content, etc.), RF sputtering or ion beam sputtering is preferred, and RF sputtering is more preferred considering the film formation rate.

[0134] As a method for manufacturing mask blank 100, it is preferable to use a silicon target or a target made of silicon containing one or more elements selected from semi-metallic elements and non-metallic elements, and form a light-shielding film 2 on a light-transmitting substrate 1 by reactive sputtering in a sputtering gas containing nitrogen-based gas and rare gas.

[0135] The nitrogen-based gas used in the light-shielding film formation process can be any gas containing nitrogen. As mentioned above, the oxygen content of the light-shielding film 2, except for its surface layer, is preferably suppressed to a low level. Therefore, it is preferable to use an oxygen-free nitrogen-based gas, and more preferably nitrogen (N2 gas). Furthermore, any rare gas can be used in the light-shielding film 2 formation process. Preferred rare gases include argon, krypton, and xenon. Additionally, to alleviate stress on the film, helium or neon, which have small atomic weights, can be actively introduced into the film.

[0136] As a method for forming a light-shielding film 2 with an increased surface oxygen content on the side opposite to the light-transmitting substrate 1, in addition to a method of gradually adding oxygen as an atmospheric gas in the final stage of sputtering to form the light-shielding film 2, other methods include post-processing methods such as heat treatment in an oxygen-containing gas in the atmosphere, light irradiation treatment such as a strobe lamp in an oxygen-containing gas in the atmosphere, and treatment of contacting the surface of the light-shielding film with ozone and / or oxygen plasma after sputtering to form the light-shielding film 2.

[0137] On the other hand, if it is preferred to set the surface reflectance of the light-shielding film to ArF exposure light low (e.g., below 30%), a high nitrogen content is required if this is achieved using the above-described single-layer light-shielding film. In this case, the optical density per unit thickness of the light-shielding film decreases, and the film thickness needs to be increased to ensure the specified light-shielding performance. When such a low surface reflectance is required, it is preferable to have the light-shielding film as a stacked structure of a lower and upper layer from the light-transmitting substrate side, with the lower layer using the material of the single-layer light-shielding film described in the above embodiment, and the upper layer formed of a material containing silicon and oxygen.

[0138] That is, the mask blank of this other form is characterized in that it has a light-shielding film on a light-transmitting substrate, the light-shielding film has a structure in which a lower layer and an upper layer are stacked sequentially from the light-transmitting substrate side, the lower layer is formed of a material containing silicon and nitrogen, the upper layer is formed of a material containing silicon and oxygen, the light-shielding film has an optical density of 2.5 or more for ArF exposure light, the surface reflectivity of the light-shielding film for ArF exposure light is 30% or less, the back reflectivity of the light-shielding film for ArF exposure light is 40% or less, the transmittance of the light-shielding film for light with a wavelength of 900 nm is 50% or less, the extinction coefficient k of the lower layer of the light-shielding film for light with a wavelength of 900 nm is 0.04 or more, and the thickness of the light-shielding film is 60 nm or less.

[0139] In another embodiment of the mask blank, the lower layer of the light-shielding film is preferably formed of a material composed of silicon and nitrogen, or a material composed of silicon and nitrogen composed of one or more elements selected from half-metallic and non-metallic elements. Furthermore, in this other embodiment of the mask blank, the upper layer of the light-shielding film is preferably formed of a material composed of silicon and oxygen, or a material composed of silicon and oxygen composed of one or more elements selected from half-metallic and non-metallic elements. The specific structure of the lower layer of this light-shielding film is the same as that of the single-layer structure light-shielding film in the above embodiment.

[0140] The extinction coefficient k of the upper layer for light with wavelengths between 800 nm and 900 nm is approximately zero, meaning the upper layer contributes almost nothing to blocking these wavelengths. Therefore, it is preferable to ensure light-shielding performance for wavelengths between 800 nm and 900 nm solely through the lower layer of the light-shielding film. Furthermore, this upper layer needs to reduce surface reflectivity, resulting in low light-shielding performance for ArF exposure light. Therefore, it is preferable to ensure the specified optical density for ArF exposure light solely through the lower layer of the light-shielding film.

[0141] This other form of transfer mask is characterized by having a light-shielding film with a transfer pattern on a light-transmitting substrate. The light-shielding film has a structure in which lower and upper layers are stacked sequentially from the light-transmitting substrate side. The lower layer is formed of a material containing silicon and nitrogen, and the upper layer is formed of a material containing silicon and oxygen. The light-shielding film has an optical density of 2.5 or more for ArF exposure light, a surface reflectance of 30% or less for ArF exposure light, a back reflectance of 40% or less for ArF exposure light, a transmittance of 50% or less for light with a wavelength of 900 nm, an extinction coefficient k of 0.04 or more for light with a wavelength of 900 nm for the lower layer of the light-shielding film, and a thickness of 60 nm or less. Furthermore, other aspects of the mask blank and transfer mask of this other form (such as aspects related to the light-transmitting substrate and rigid mask film) are the same as those of the mask blank and transfer mask of the above embodiment.

[0142] [Rigid mask]

[0143] In the mask blank 100 having the aforementioned light-shielding film 2, more preferably, a hard mask film 3 formed of a material having etching selectivity for the etching gas used when etching the light-shielding film 2 is further laminated on the light-shielding film 2. The light-shielding film 2 needs to ensure a specified optical density; therefore, its thickness reduction is limited. The hard mask film 3 only needs to have a thickness sufficient to function as an etching mask during the period until the dry etching of the light-shielding film 2, on which the pattern is formed, is completed; it is not substantially limited by optical properties. Therefore, the thickness of the hard mask film 3 can be significantly reduced compared to the thickness of the light-shielding film 2. Furthermore, the organic-based resist film only needs to have a thickness sufficient to function as an etching mask during the period until the dry etching of the hard mask film 3, on which the pattern is formed, is completed; therefore, compared to the past, the thickness of the resist film can be significantly reduced, and problems such as resist pattern tilting can be suppressed.

[0144] The hard mask film 3 is preferably formed of a chromium (Cr)-containing material. Chromium-containing materials have particularly high dry etching resistance to dry etching using fluorine-based gases such as SF6.

[0145] When a chromium-containing material is used for the light-shielding film 2, the film thickness of the light-shielding film 2 is relatively thick. Therefore, lateral etching problems will occur during the dry etching of the light-shielding film 2. However, when a chromium-containing material is used as the hard mask film 3, the film thickness of the hard mask film 3 is relatively thin, so it is difficult for problems caused by lateral etching to occur.

[0146] In addition to chromium metal, materials containing chromium that also contain one or more elements selected from oxygen, nitrogen, carbon, boron, and fluorine, such as CrN, CrC, CrON, CrCO, and CrCON, are preferred. Adding these elements to chromium metal makes the film more likely to become an amorphous structure, which can suppress the surface roughness of the film and the edge roughness of the lines during dry etching of the light-shielding film 2.

[0147] Furthermore, from the viewpoint of dry etching of the hard mask film 3, it is preferable to use a material containing one or more elements selected from oxygen, nitrogen, carbon, boron and fluorine as the material for forming the hard mask film 3.

[0148] While chromium-based materials can be etched by a mixture of chlorine-based and oxygen gases, the etching rate of chromium metal by this etching gas is not high. By including one or more elements selected from oxygen, nitrogen, carbon, boron, and fluorine in the chromium, the etching rate against the mixture of chlorine-based and oxygen gases can be increased. Alternatively, the chromium-containing material forming the hard mask film 3 can be made to contain one or more elements selected from indium, molybdenum, and tin. Including one or more of these elements further increases the etching rate against the mixture of chlorine-based and oxygen gases.

[0149] As the material for forming the hard mask film 3, besides materials containing chromium, materials containing metals such as tantalum (Ta) or tungsten (W) can also be used. For example, as the tantalum-containing material in this case, in addition to tantalum metal, materials containing one or more elements selected from nitrogen, boron, and carbon can be mentioned. Specific examples include Ta, TaN, TaO, TaON, TaBN, TaBO, TaBON, TaCN, TaCO, TaCON, TaBCN, and TaBOCN.

[0150] Preferably, in the mask blank 100, an organic-based resist film is formed in contact with the surface of the hard mask film 3 with a film thickness of 100 nm or less. In the case of fine patterns corresponding to the DRAM hp32nm generation, SRAF (Sub-Resolution Assist Feature) with a linewidth of 40 nm is sometimes provided on the transfer pattern to be formed on the hard mask film 3. However, in this case, the aspect ratio of the resist pattern can be as low as 1:2.5, so that damage or detachment of the resist pattern during development of the resist film can be suppressed, such as during washing. Furthermore, the film thickness of the resist film is more preferably 80 nm or less.

[0151] Alternatively, instead of setting the hard mask film 3 on the mask blank 100, the resist film can be formed directly in contact with the light-shielding film 2. In this case, the structure is simple, and dry etching of the hard mask film 3 is not required when manufacturing the transfer mask, thus reducing the number of manufacturing steps. Furthermore, in this case, it is preferable to first perform surface treatment such as HMDS (hexamethyldisilazane) on the light-shielding film 2 before forming the resist film.

[0152] Furthermore, as described below, the mask blank of the present invention is a mask blank suitable for use in binary masks, but is not limited to use in binary masks. It can also be used as a mask blank for alternating phase-shifting masks or for CPL (Chromeless Phase Lithography) masks.

[0153] [Transfer Mask]

[0154] Figure 4 This is a cross-sectional schematic diagram showing the process of manufacturing a transfer mask (binary mask) 200 from a mask blank 100 according to an embodiment of the present invention.

[0155] The transfer mask 200 of the present invention is a binary mask having a light-shielding film 2 (light-shielding film pattern 2a) with a transfer pattern on a light-transmitting substrate 1. The light-shielding film is characterized in that it is a single-layer film formed of a material containing silicon and nitrogen, having an optical density of 2.5 or more for ArF excimer laser exposure light, a surface reflectivity of 40% or less, a back reflectivity of 40% or less, a transmittance of 50% or less for light with a wavelength of 900 nm, an extinction coefficient of 0.04 or more, and a thickness of 60 nm or less.

[0156] The matters related to the light-transmitting substrate 1 and the light-shielding film 2 of the transfer mask 200 are the same as those of the mask blank 100, and the transfer mask 200 has the same technical features as the mask blank 100.

[0157] Furthermore, the manufacturing method of the transfer mask 200 of the present invention uses the above-mentioned mask blank 100, and is characterized by comprising: a step of forming a pattern including a transfer pattern and alignment marks on a hard mask film 3 by dry etching; a step of forming a pattern including a transfer pattern and alignment marks on a light-shielding film 2 by dry etching using a hard mask film 3 (hard mask pattern 3a) having these patterns as a mask; and a step of removing the hard mask pattern 3a.

[0158] This transfer mask 200 can detect alignment marks with sufficient contrast even when using an exposure device that uses long-wavelength detection light (LW) for alignment, thus enabling the mask alignment operation to be performed without errors.

[0159] Moreover, the ArF of the transfer mask 200 has high lightfastness, and even after accumulating exposure light from ArF excimer laser, it can suppress the change (coarseness) of the CD (critical dimension) of the light-shielding film pattern 2a to a small range.

[0160] Therefore, when a transfer mask 200 is placed on the mask stage of an exposure apparatus that uses a long-wavelength detection light LW for alignment and an ArF excimer laser as the exposure light, the mask alignment action can be performed simultaneously when the light-shielding film pattern 2a is exposed and transferred to the resist film, so as to fully meet the design specifications for transferring the pattern to the resist film on the semiconductor device.

[0161] Below, according to Figure 4 The manufacturing process shown illustrates an example of a method for manufacturing a transfer mask 200. Furthermore, in this example, a material containing silicon and nitrogen is used for the light-shielding film 2, and a material containing chromium is used for the rigid mask film 3.

[0162] First, prepare a mask blank of 100 (refer to...). Figure 4(a) A resist film is formed by spin coating with the rigid mask film 3. Next, the pattern to be formed on the mask film 2 is drawn by exposure, followed by development and other prescribed processes to form the resist pattern 4a (see reference). Figure 4 (b)). In addition, the pattern drawn by the electron beam includes alignment marks, etc., in addition to the transfer pattern.

[0163] Next, using the resist pattern 4a as a mask, dry etching with a chlorine-based gas, such as a mixture of chlorine and oxygen, is performed to form a pattern (hard mask pattern 3a) on the hard mask film 3 (see reference). Figure 4 (c)). As a chlorine-based gas, it is sufficient to contain Cl, such as Cl2, SiCl2, CHCl3, CH2Cl2, BCl3, etc. When using a mixture of chlorine and oxygen, for example, the gas flow ratio can be Cl2:O2 = 4:1.

[0164] Next, the resist pattern 4a (refer to) is removed by ashing or resist stripping solution. Figure 4 (d)).

[0165] Next, using the hard mask pattern 3a as a mask, dry etching with fluorine-based gases is performed to form a pattern (shielding film pattern 2a) on the light-shielding film 2 (see reference). Figure 4 (e)). As a fluorine-based gas, any gas containing F can be used, but SF6 is preferred. Examples of gases other than SF6 include CHF3, CF4, C2F6, and C4F8, but fluorine-based gases containing C have a higher etching rate for the transparent substrate 1, which is a glass material. SF6 causes less damage to the transparent substrate 1 and is therefore preferred. In addition, He or the like can also be added to SF6.

[0166] Subsequently, the hard mask pattern 3a is removed using a chromium etching solution, and after cleaning and other prescribed treatments, a transfer mask 200 is obtained (see reference). Figure 4 (f)). Furthermore, the removal process of the hard mask pattern 3a can also be performed using dry etching with a mixture of chlorine and oxygen gases. Here, a mixture containing cerium ammonium nitrate and perchloric acid can be cited as an example of a chromium etching solution.

[0167] Furthermore, while the case of a binary mask for transfer 200 has been described here, the transfer mask of the present invention is not limited to binary masks, but can also be used for alternating phase-shift masks and CPL masks. That is, in the case of an alternating phase-shift mask, the light-shielding film of the present invention can be used. In addition, in the case of a CPL mask, the light-shielding film of the present invention can be used mainly in the area including the light-shielding band on the outer periphery. Moreover, similar to the case of a binary mask, in the cases of alternating phase-shift masks and CPL masks, alignment mark detection can also be performed with sufficient contrast using long-wavelength detection light LW.

[0168] Furthermore, the method for manufacturing a semiconductor device according to the present invention is characterized in that a pattern is exposed and transferred onto a resist film on a semiconductor substrate using the above-described transfer mask 200 or a transfer mask 200 manufactured from the above-described mask blank 100.

[0169] The transfer mask 200 or mask blank 100 of the present invention has the above-described effects. Therefore, when exposing a resist film formed on a semiconductor wafer using the transfer mask of the present invention, alignment mark detection can be performed with sufficient sensitivity. Thus, exposure operation can be stopped without causing insufficient sensitivity in alignment mark detection, and semiconductor devices can be manufactured in a manner with high ArF lightfastness.

[0170] Example

[0171] The embodiments of the present invention will be further described in detail below through examples.

[0172] (Example 1)

[0173] [Mask blank manufacturing]

[0174] A light-transmitting substrate 1 made of synthetic quartz glass is prepared, with a main surface size of approximately 152 mm × approximately 152 mm and a thickness of approximately 6.25 mm. After the end face and main surface of the light-transmitting substrate 1 are ground to a specified surface roughness, a specified cleaning and drying process is performed.

[0175] Next, a transparent substrate 1 was placed in a single-blade (leaf-type) RF sputtering apparatus. A silicon (Si) target was used, and a mixture of krypton (Kr), helium (He), and nitrogen (N2) gas (flow ratio Kr:He:N2 = 10:100:1, pressure = 0.1 Pa) was used as the sputtering gas. The RF power supply was set to 1.5 kW. A light-shielding film 2 composed of silicon and nitrogen (Si:N = 50 atomic%:50 atomic%) was formed on the transparent substrate 1 with a thickness of 57 nm by reactive sputtering (RF sputtering). Here, the composition of the light-shielding film 2 was determined by X-ray photoelectron spectroscopy (XPS). The methods for determining the composition of other films are the same below.

[0176] Next, with the aim of adjusting the stress of the film, the light-transmitting substrate 1 on which the light-shielding film 2 is formed was heat-treated in the atmosphere at a heating temperature of 500°C for 1 hour. The results of measuring the spectral transmittance of the heat-treated light-shielding film 2 using a spectrophotometer (Agilent Technologies, Cary 4000) are shown below. Figure 2The transmittance for long-wavelength light (800 nm to 900 nm) increases monotonically with increasing wavelength, with transmittances of 42.8%, 44.9%, 46.7%, and 47.0% for wavelengths of 800 nm, 850 nm, 890 nm, and 900 nm, respectively. Furthermore, the optical density (OD value) for ArF excimer laser light (wavelength 193 nm) is 2.96.

[0177] Furthermore, the refractive index n and extinction coefficient k of the light-shielding film 2 were measured using a spectroscopic ellipsometry (JAWoollam M-2000D). The results of its spectroscopic characteristics (i.e., the refractive index n and extinction coefficient k for each wavelength) are shown below. Figure 3 The refractive index n is 1.830 and the extinction coefficient k is 1.785 at a wavelength of 193 nm; the refractive index n is 3.172 and the extinction coefficient k is 0.093 at a wavelength of 800 nm; the refractive index n is 3.137 and the extinction coefficient k is 0.066 at a wavelength of 850 nm; the refractive index n is 3.112 and the extinction coefficient k is 0.050 at a wavelength of 890 nm; and the refractive index n is 3.106 and the extinction coefficient k is 0.047 at a wavelength of 900 nm.

[0178] The surface reflectance and back reflectance of the light-shielding film 2 at a wavelength of 193 nm were measured using a spectrophotometer (Hitachi High Technology Co., Ltd., U-4100), and the values ​​were 37.1% and 30.0%, respectively.

[0179] Next, a transparent substrate 1 with a heat-treated light-shielding film 2 formed on it is placed in a single-wafer DC sputtering apparatus. Using a chromium (Cr) target, reactive sputtering (DC sputtering) is performed in a mixed atmosphere of argon (Ar) and nitrogen (N2) to form a hard mask film 3 consisting of a CrN film with a thickness of 5 nm. The film composition ratio of this film, as measured by XPS, is Cr: 75 atomic%, N: 25 atomic%. Furthermore, stress adjustment of the hard mask film 3 is performed by heat treatment (280°C) at a temperature lower than that of the heat treatment performed on the light-shielding film 2.

[0180] Through the above steps, a mask blank 100 with a structure of stacked light-shielding film 2 and rigid mask film 3 is manufactured on the light-transmitting substrate 1.

[0181] [Manufacturing of transfer masks]

[0182] Next, using the mask blank 100 of Example 1, the transfer mask (binary mask) 200 of Example 1 is manufactured by following the steps below.

[0183] First, prepare the mask blank 100 of Example 1 (refer to...) Figure 4(a) A resist film composed of a chemically enhanced resist for electron beam mapping is formed with a thickness of 80 nm, grounded to the surface of the hard mask film 3. Next, the resist film is electron-beam mapped with the pattern to be formed on the light-shielding film 2, followed by a prescribed development and cleaning process to form the resist pattern 4a (see reference). Figure 4 (b)). In addition, the pattern drawn by the electron beam includes alignment marks, etc., in addition to the transfer pattern.

[0184] Next, using the resist pattern 4a as a mask, dry etching was performed using a mixture of chlorine and oxygen gas (gas flow ratio Cl2:O2 = 4:1) to form a pattern (hard mask pattern 3a) on the hard mask film 3 (see reference). Figure 4 (c)).

[0185] Next, remove the resist pattern 4a (refer to...) Figure 4 (d) Next, using the hard mask pattern 3a as a mask, dry etching with a fluorine-based gas (a mixture of SF6 and He) is performed to form a pattern (shielding film pattern 2a) on the light-shielding film 2 (see reference). Figure 4 (e)).

[0186] Subsequently, the hard mask pattern 3a is removed using a chromium etching solution containing cerium ammonium nitrate and perchloric acid. After cleaning and other prescribed treatments, a transfer mask 200 is obtained (see reference). Figure 4 (f)).

[0187] The transfer mask 200 of Example 1 was placed in an exposure apparatus using long-wavelength detection light (LW) to detect alignment marks, and the result was that mark detection was achieved with sufficient contrast. Moreover, the mask alignment operation could be performed accurately in one go.

[0188] Next, the transfer mask 200 was subjected to a cumulative irradiation dose of 40 kJ / cm². 2 The light-shielding film pattern 2a was subjected to intermittent irradiation with ArF excimer laser light. The change in CD (cathode) before and after the irradiation treatment was less than 1.2 nm, which is within the range of CD changes suitable for use as a light-shielding film pattern 2a. Therefore, it can be concluded that the light-shielding film pattern 2a has sufficient ArF lightfastness for practical applications.

[0189] By placing the transfer mask 200 of Example 1 on the mask stage of the exposure apparatus and performing exposure transfer on the resist film on the semiconductor device, a circuit pattern can be formed with high precision without causing mask misalignment.

[0190] (Comparative Example 1)

[0191] [Mask blank manufacturing]

[0192] Except for the following treatment of the light-shielding film, the mask blank of Comparative Example 1 can be manufactured by the same steps as the mask blank 100 of Example 1.

[0193] The method for forming the light-shielding film of Comparative Example 1 is as follows.

[0194] A transparent substrate 1 is set in a monolithic RF sputtering apparatus. A silicon (Si) target is used, and a mixture of krypton (Kr), helium (He) and nitrogen (N2) is used as the sputtering gas. A light-shielding film composed of silicon and nitrogen (Si:N = 48 atomic%: 52 atomic%) is formed on the transparent substrate 1 with a thickness of 100 nm by reactive sputtering (RF sputtering).

[0195] Next, with the aim of adjusting the stress of the film, the light-transmitting substrate 1 on which the light-shielding film is formed was heat-treated in the atmosphere at a heating temperature of 500°C for 1 hour. The spectral transmittance of the heat-treated light-shielding film was measured using a spectrophotometer (Agilent Technologies, Cary 4000). The transmittances at wavelengths of 800 nm, 850 nm, 890 nm, and 900 nm were 74.2%, 74.2%, 73.9%, and 73.9%, respectively. Furthermore, the optical density (OD value) for ArF excimer laser light (wavelength 193 nm) was 2.9.

[0196] In addition, the refractive index n and extinction coefficient k of the light-shielding film were measured using a spectroscopic ellipsometry (JAWoollam M-2000D). The refractive index n was 2.4 and the extinction coefficient k was 1.0 at a wavelength of 193 nm; the refractive index n was 2.3 and the extinction coefficient k was 0 at a wavelength of 800 nm; the refractive index n was 2.3 and the extinction coefficient k was 0 at a wavelength of 850 nm; the refractive index n was 2.3 and the extinction coefficient k was 0 at a wavelength of 890 nm; and the refractive index n was 2.3 and the extinction coefficient k was 0 at a wavelength of 900 nm.

[0197] The surface reflectance and back reflectance of the light-shielding film at a wavelength of 193 nm were measured using a spectrophotometer (Hitachi High Technology Co., Ltd., U-4100), and the values ​​were 21% and 15%, respectively.

[0198] [Manufacturing of transfer masks]

[0199] Next, using the mask blank of Comparative Example 1, a transfer mask (binary mask) of Comparative Example 1 was manufactured by following the same steps as in Example 1.

[0200] When the transfer mask of Comparative Example 1 was placed in an exposure apparatus using long-wavelength detection light (LW) for mark detection, the mark detection could not be performed with sufficient contrast. Moreover, mask alignment errors occurred repeatedly.

[0201] Next, the transfer mask of Comparative Example 1 was subjected to a cumulative irradiation dose of 40 kJ / cm². 2 The light-shielding film was treated with intermittent irradiation using ArF excimer laser light. The change in CD of the light-shielding film pattern before and after the irradiation treatment was less than 1.2 nm, which is within the range of CD changes that can be used as light-shielding film patterns. The light-shielding film pattern has sufficient ArF light resistance in practical applications.

[0202] The transfer mask 200 of Comparative Example 1 was placed on the mask stage of the exposure apparatus and exposed and transferred on the resist film on the semiconductor device. The mask misalignment occurred repeatedly, and the exposure for manufacturing semiconductor devices could not be reliably performed.

[0203] Symbol Explanation

[0204] 1. Transparent substrate

[0205] 2 shading film

[0206] 2a Light-blocking film pattern

[0207] 3. Rigid mask

[0208] 3a Hard Mask Pattern

[0209] 4a resist pattern

[0210] 100 mask blank

[0211] 200 transfer mask (binary mask)

Claims

1. A mask blank having a light-shielding film on a light-transmitting substrate, characterized in that, The light-shielding film has a structure in which the lower and upper layers are stacked sequentially from the light-transmitting substrate side. The lower layer is formed of a material containing silicon and nitrogen. The upper layer is formed of a material containing silicon and oxygen. The light-shielding film has an optical density of 2.5 or higher for ArF exposure light. The light-shielding film has a surface reflectance of less than 30% to ArF exposure light. The light-shielding film has a back reflectance of less than 40% for ArF exposure light. The light-shielding film has a transmittance of less than 50% for light with a wavelength of 900nm. The lower layer of the light-shielding film has an extinction coefficient k of 0.04 or higher for light with a wavelength of 900nm. The thickness of the light-shielding film is less than 60 nm.

2. The mask blank as described in claim 1, characterized in that, The lower layer of the light-shielding film is formed using a material composed of silicon and nitrogen, or using a material composed of one or more elements selected from semi-metallic elements and non-metallic elements, together with silicon and nitrogen, wherein the semi-metallic elements and the non-metallic elements are elements other than silicon and nitrogen.

3. The mask blank as described in claim 1 or 2, characterized in that, The upper layer of the light-shielding film is formed using a material composed of silicon and oxygen, or using a material composed of one or more elements selected from semi-metallic elements and non-metallic elements, together with silicon and oxygen, wherein the semi-metallic elements and the non-metallic elements are elements other than silicon and oxygen.

4. The mask blank as described in claim 1 or 2, characterized in that, The lower layer of the light-shielding film has an extinction coefficient k of 0.10 or higher for light with a wavelength of 700nm.

5. The mask blank as described in claim 1 or 2, characterized in that, The lower layer of the light-shielding film has a refractive index n of less than 3.5 for light with a wavelength of 900nm.

6. The mask blank as described in claim 1 or 2, characterized in that, The lower layer of the light-shielding film has a refractive index n of less than 3.8 for light with a wavelength of 700nm.

7. The mask blank as described in claim 1 or 2, characterized in that, The lower layer of the light-shielding film has a refractive index n of 1.6 or higher and 2.1 or lower for ArF exposure light.

8. The mask blank as described in claim 1 or 2, characterized in that, The lower layer of the light-shielding film has an extinction coefficient k of 1.6 or higher and 2.1 or lower for ArF exposure light.

9. The mask blank as described in claim 1 or 2, characterized in that, The light-shielding film has a rigid mask film made of a chromium-containing material.

10. A transfer mask having a light-shielding film with a transfer pattern on a light-transmitting substrate, characterized in that, The light-shielding film has a structure in which the lower and upper layers are stacked sequentially from the light-transmitting substrate side. The lower layer is formed of a material containing silicon and nitrogen. The upper layer is formed of a material containing silicon and oxygen. The light-shielding film has an optical density of 2.5 or higher for ArF exposure light. The light-shielding film has a surface reflectance of less than 30% to ArF exposure light. The light-shielding film has a back reflectance of less than 40% for ArF exposure light. The light-shielding film has a transmittance of less than 50% for light with a wavelength of 900nm. The lower layer of the light-shielding film has an extinction coefficient k of 0.04 or higher for light with a wavelength of 900nm. The thickness of the light-shielding film is less than 60 nm.

11. The transfer mask as described in claim 10, characterized in that, The lower layer of the light-shielding film is formed using a material composed of silicon and nitrogen, or using a material composed of one or more elements selected from semi-metallic elements and non-metallic elements, together with silicon and nitrogen, wherein the semi-metallic elements and the non-metallic elements are elements other than silicon and nitrogen.

12. The transfer mask as described in claim 10 or 11, characterized in that, The upper layer of the light-shielding film is formed using a material composed of silicon and oxygen, or using a material composed of one or more elements selected from semi-metallic elements and non-metallic elements, together with silicon and oxygen, wherein the semi-metallic elements and the non-metallic elements are elements other than silicon and oxygen.

13. The transfer mask as described in claim 10 or 11, characterized in that, The lower layer of the light-shielding film has an extinction coefficient k of 0.10 or higher for light with a wavelength of 700nm.

14. The transfer mask as described in claim 10 or 11, characterized in that, The lower layer of the light-shielding film has a refractive index n of less than 3.5 for light with a wavelength of 900nm.

15. The transfer mask as described in claim 10 or 11, characterized in that, The lower layer of the light-shielding film has a refractive index n of less than 3.8 for light with a wavelength of 700nm.

16. The transfer mask as described in claim 10 or 11, characterized in that, The lower layer of the light-shielding film has a refractive index n of 1.6 or higher and 2.1 or lower for ArF exposure light.

17. The transfer mask as described in claim 10 or 11, characterized in that, The lower layer of the light-shielding film has an extinction coefficient k of 1.6 or higher and 2.1 or lower for ArF exposure light.

18. A method for manufacturing a semiconductor device, characterized in that, The process includes the step of exposing and transferring a transfer pattern onto a resist film on a semiconductor substrate using a transfer mask as described in any one of claims 10 to 17.

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