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

Abstract

A mask blank (100) has a light-blocking film (2) on a light-transmissive substrate (1), characterized in that the light-blocking film is a single-layer film formed of a material containing silicon and nitrogen, has a refractive index of 1.6 or more and 2.1 or less for exposure light of an ArF excimer laser, has an extinction coefficient of 1.6 or more and 2.1 or less, has an extinction coefficient of 0.04 or more for light of a wavelength of 900 nm, and has a thickness of 40 nm or more and 60 nm or less.

Description

[0001] This application is a divisional application of the patent application for which the international application date is 2 August 2017, the application number is 201780050886.2, and the name of the invention is "Mask blank, mask for transfer, and method for manufacturing semiconductor device". TECHNICAL FIELD

[0002] The present invention relates to a mask blank, a mask for transfer manufactured using the mask blank. In addition, the present invention relates to a method for manufacturing a semiconductor device using the mask for transfer. BACKGROUND

[0003] In a manufacturing process of a semiconductor device, a fine pattern is formed using a photolithography method. When the pattern of the semiconductor device is made fine, in addition to the fine of the mask pattern formed in the mask for transfer, the wavelength of the exposure light source used in the photolithography needs to be made short. In recent years, an ArF excimer laser (wavelength 193 nm) is gradually applied to the exposure light source when the semiconductor device is manufactured.

[0004] Among the masks for transfer, there is a binary mask. The binary mask is, for example, a mask for transfer in which a light-shielding film pattern that shields exposure light is formed on a light-transmissive substrate as described in Patent Literature 1, and as the light-shielding film, a chromium (Cr) or molybdenum silicide (MoSi) material is widely used.

[0005] In the case where the light-shielding film is composed of a chromium material, since the radicality of the mixed gas of the chlorine gas and oxygen gas used when the film is dry-etched is high, it is difficult to dry-etch the light-shielding film with sufficient anisotropy, and it is difficult to form a fine light-shielding film pattern with sufficient precision.

[0006] In the case where a molybdenum silicide (MoSi) material is used as the light-shielding film material, the aforementioned dry-etching has a small problem, and it is possible to easily form a fine light-shielding film pattern with high precision. On the other hand, in recent years, it has been found that the MoSi film has low resistance to the exposure light of the ArF excimer laser (ArF exposure light), which is so-called ArF light resistance.

[0007] PRIOR ART DOCUMENTS

[0008] PATENT LITERATURE

[0009] Patent Literature 1: Japanese Patent Application Laid-Open No. 2007-33470 SUMMARY

[0010] PROBLEMS TO BE SOLVED BY THE INVENTION

[0011] It was confirmed that, in the case where a material containing silicon and nitrogen is used for a phase shift film, high ArF light resistance is obtained. Therefore, the possibility of obtaining high ArF light resistance by using a thin film (SiNx film) containing silicon and nitrogen as a light shielding film of a binary mask was investigated. However, it was found that, in the case where a light shielding film is formed by a single layer structure of SiNx film, the following problems exist.

[0012] Generally, in a binary mask, it is required that a light shielding film formed with a transfer pattern has a prescribed optical density (for example, 2.5 or more) or more with respect to ArF excimer laser light (hereinafter, referred to as ArF exposure light) irradiated from an exposure apparatus. Moreover, it is required that the light shielding film has a prescribed reflectance (back surface reflectance, for example, 40% or less) or less with respect to ArF exposure light incident to a surface on the side in contact with a light-transmissive substrate, and simultaneously has a prescribed reflectance (surface reflectance, for example, 40% or less) or less with respect to ArF exposure light incident to a surface on the side opposite to the light-transmissive substrate. From the viewpoint of the optical density required for the light shielding film, it is preferable that the SiNx film contains less nitrogen. However, from the viewpoint of the surface reflectance and the back surface reflectance required for the light shielding film, it is necessary that the SiNx film contains a certain amount of nitrogen.

[0013] Some exposure apparatuses perform an exposure operation after performing alignment mark detection using long wavelength light having a wavelength of 800 nm or more and 900 nm or less. Here, the long wavelength light is referred to as long wavelength detection light LW. When a binary mask in which a light shielding film is constituted by a single layer structure of SiNx film is placed in an exposure apparatus using the long wavelength detection light LW to perform exposure, a problem that exposure cannot be performed due to insufficient detection sensitivity of the alignment mark detection has occurred many times.

[0014] If the nitrogen content of the SiNx film constituting the light shielding film is greatly reduced, the transmittance of the long wavelength light can be reduced, and the problem of insufficient detection sensitivity of the alignment mark can be eliminated. However, in this case, the surface reflectance and the back surface reflectance of the light shielding film with respect to ArF exposure light are both high, and thus a new problem that the transfer performance of the binary mask is greatly reduced can occur.

[0015] An object of the present application is to provide a mask blank having a light shielding film constituted by a single layer structure of SiNx film, in which the light shielding film satisfies the requirements for various optical characteristics with respect to ArF exposure light, and simultaneously solves the problem of insufficient sensitivity when performing mark detection using long wavelength light having a wavelength of 800 nm or more and 900 nm or less. In addition, an object of the present application is to provide a transfer mask manufactured using the mask blank. Furthermore, an object of the present application is to provide a method for manufacturing a semiconductor device using the transfer mask.

[0016] Technical solution for solving the problem

[0017] To solve the above problems, the present application has the following features.

[0018] (1)

[0019] A mask blank having a light-blocking film on a light-transmissive substrate, characterized by

[0020] The light-blocking film is a single layer film formed of a material containing silicon and nitrogen,

[0021] The refractive index n of the light-blocking film with respect to exposure light of an ArF excimer laser is 1.6 or more and 2.1 or less,

[0022] The extinction coefficient k of the light-blocking film with respect to the exposure light is 1.6 or more and 2.1 or less,

[0023] The extinction coefficient k of the light-blocking film with respect to light of a wavelength of 900 nm is 0.04 or more,

[0024] The thickness of the light-blocking film is 40 nm or more and 60 nm or less.

[0025] (2)

[0026] The mask blank according to (1), characterized in that

[0027] The refractive index n of the light-blocking film with respect to light of a wavelength of 900 nm is 3.5 or less.

[0028] (3)

[0029] The mask blank according to (1) or (2), characterized in that

[0030] The extinction coefficient k of the light-blocking film with respect to light of a wavelength of 700 nm is 0.10 or more.

[0031] (4)

[0032] The mask blank according to (1) or (2), characterized in that

[0033] The refractive index n of the light-blocking film with respect to light of a wavelength of 700 nm is 3.8 or less.

[0034] (5)

[0035] The mask blank according to (1) or (2), characterized in that

[0036] The light-blocking film is formed of a material composed of silicon and nitrogen, or a material composed of silicon, nitrogen, and one or more elements selected from semi-metal elements and non-metal elements other than silicon and nitrogen.

[0037] (6)

[0038] The mask blank according to claim 1 or 2, wherein

[0039] The light-shielding film has a composition gradient portion in a surface layer thereof, the composition gradient portion increasing an oxygen content toward a surface on an opposite side of the light-transmitting substrate side, and the light-shielding film other than the surface layer is formed of a material composed of silicon and nitrogen or a material composed of silicon, nitrogen, and one or more elements selected from among semi-metal elements and non-metal elements other than silicon and nitrogen.

[0040] (claim 7)

[0041] The mask blank according to claim 1 or 2, wherein

[0042] The light-shielding film has a nitrogen content of 50 atomic% or less.

[0043] (claim 8)

[0044] The mask blank according to claim 1 or 2, wherein

[0045] The light-shielding film has a silicon content of 50 atomic% or more.

[0046] (claim 9)

[0047] The mask blank according to claim 1 or 2, wherein

[0048] A hard mask film composed of a material containing chromium is provided on the light-shielding film.

[0049] (claim 10)

[0050] A mask for transfer, comprising a light-shielding film having a transfer pattern on a light-transmitting substrate, wherein

[0051] The light-shielding film is a single layer film formed of a material containing silicon and nitrogen,

[0052] The light-shielding film has a refractive index n of 1.6 or more and 2.1 or less with respect to an exposure light of an ArF excimer laser,

[0053] The light-shielding film has an extinction coefficient k of 1.6 or more and 2.1 or less with respect to the exposure light,

[0054] The light-shielding film has an extinction coefficient k of 0.04 or more with respect to a light of 900 nm wavelength,

[0055] The light-shielding film has a thickness of 40 nm or more and 60 nm or less.

[0056] (claim 11)

[0057] The transfer mask according to claim 10, wherein

[0058] The optical shielding film has a refractive index n of 3.5 or less for light of a wavelength of 900 nm.

[0059] (claim 12)

[0060] The transfer mask according to claim 10 or 11, wherein

[0061] The optical shielding film has an extinction coefficient k of 0.10 or more for light of a wavelength of 700 nm.

[0062] (claim 13)

[0063] The transfer mask according to claim 10 or 11, wherein

[0064] The optical shielding film has a refractive index n of 3.8 or less for light of a wavelength of 700 nm.

[0065] (claim 14)

[0066] The transfer mask according to claim 10 or 11, wherein

[0067] The optical shielding film is formed of a material composed of silicon and nitrogen, or a material composed of silicon, nitrogen, and one or more elements selected from among semi-metal elements and non-metal elements other than silicon and nitrogen.

[0068] (claim 15)

[0069] The transfer mask according to claim 10 or 11, wherein

[0070] The optical shielding film has a composition gradient portion that increases the oxygen content toward the surface on the opposite side of the transparent substrate side, and the optical shielding film other than the surface layer is formed of a material composed of silicon and nitrogen, or a material composed of silicon, nitrogen, and one or more elements selected from among semi-metal elements and non-metal elements other than silicon and nitrogen.

[0071] (claim 16)

[0072] The transfer mask according to claim 10 or 11, wherein

[0073] The optical shielding film has a nitrogen content of 50 atomic % or less.

[0074] (claim 17)

[0075] The transfer mask according to claim 10 or 11, wherein

[0076] The light shielding film has a silicon content of 50 atomic % or more.

[0077] (TECHNICAL SOLUTION 18)

[0078] A method of manufacturing a semiconductor device, characterized by

[0079] A process of exposing and transferring a transfer pattern to a resist film on a semiconductor substrate using the transfer mask of any one of technical solutions 10 to 17.

[0080] EFFECT OF THE INVENTION

[0081] The light shielding film of the mask blank of the present application is formed of a material containing silicon and nitrogen, has a transmittance of 50% or less for light of a wavelength of 900 nm, and has an extinction coefficient k of 0.04 or more. The material containing silicon and nitrogen has a characteristic that the longer the wavelength, the higher the transmittance and the smaller the extinction coefficient k for light of a wavelength of 800 nm or more and 900 nm or less in addition to high ArF light resistance. By this optical characteristic, when the transmittance for light of a wavelength of 900 nm is 50% or less and the extinction coefficient is 0.04 or more, the long-wavelength detection light LW can be sufficiently extinguished. Therefore, the long-wavelength detection light LW can be used to detect the alignment mark formed in the transfer mask manufactured using the mask blank with sufficient contrast, and the problem of insufficient exposure due to insufficient sensitivity of the alignment mark detection can be solved.

[0082] In addition, the light shielding film of the mask blank of the present application has an optical density of 2.5 or more for exposure light of an ArF excimer laser, a surface reflectance of 40% or less, and a back surface reflectance of 40% or less, and thus has sufficient exposure transfer characteristics optically for pattern exposure light.

[0083] Further, the light shielding film has a film thickness of 60 nm or less, and thus the deviation (EMF deviation) caused by the electromagnetic field effect of the mask pattern and the shadow effect caused by the three-dimensional structure of the mask pattern can be converged within an allowable range. In addition, since it is a thin film, a fine light shielding film pattern can be easily formed.

[0084] Moreover, since the light shielding film is a single layer, the number of processes at the time of manufacturing the light shielding film is small, and the manufacturing quality management including defects becomes easy.

[0085] In addition, the transfer mask of the present application has the same characteristics as the light shielding film of the above-described mask blank of the present application. By this transfer mask, in addition to the problem of high ArF light resistance of the light shielding film having a transfer pattern, the problem of insufficient exposure due to insufficient sensitivity of the alignment mark detection can be solved. BRIEF DESCRIPTION OF DRAWINGS

[0086] Figure 1is a cross-sectional view showing a mask blank structure of an embodiment of the present application.

[0087] Figure 2 is a characteristic diagram showing wavelength dependence of transmittance of a light shielding film of an embodiment of the present application.

[0088] Figure 3 is a characteristic diagram showing wavelength dependence of optical coefficient of a light shielding film of an embodiment of the present application.

[0089] Figure 4 is a cross-sectional view showing a manufacturing process of a transfer mask of an embodiment of the present application. DETAILED DESCRIPTION

[0090] First, the course of completion of the present application is explained. The present inventors and others have conducted intensive research on the cause of insufficient detection sensitivity of an alignment mark using long wavelength detection light LW. As a result, it was found that insufficient alignment mark detection sensitivity is caused by insufficient optical contrast, and the cause thereof is that the light shielding film does not sufficiently extinguish long wavelength detection light LW.

[0091] Therefore, research was conducted on a light shielding film capable of sufficiently extinguishing long wavelength detection light LW. Here, research was conducted with the aim of being able to be applied even if the wavelength of long wavelength detection light LW differs depending on the exposure apparatus.

[0092] A material containing silicon and nitrogen having high ArF light resistance has a higher transmittance for light of a longer wavelength of 800 nm or more and 900 nm or less. In other words, it has a light splitting characteristic of a longer wavelength and a smaller extinction coefficient k. Therefore, by specifying the transmittance of a light shielding film at a wavelength of 900 nm, the light shielding film is made to have sufficient extinction properties for long wavelength detection light LW. In view of the above, it is considered that by forming a light shielding film from a material containing silicon and nitrogen, and specifying the transmittance of the light shielding film at a wavelength of 900 nm, it is possible to ensure high ArF light resistance, while also solving the problem of poor alignment mark detection.

[0093] In addition, the optical density of the light shielding film for ArF exposure light, the respective reflectances of the surface and back surface for exposure light, and the film thickness are specified, whereby it is possible to perform transfer of a fine pattern.

[0094] As a result of further discussion of the light shielding film, it was found that a film satisfying the above specifications can be obtained by a single layer film which is easy to manage in terms of the number of processes, defect quality management, and manufacturing process management, and thus the present application was completed.

[0095] [Mask blank]

[0096] Next, each embodiment of the present application is explained. Figure 1 is a cross-sectional view showing the structure of a mask blank 100 of an embodiment of the present application.Figure 1 The mask blank 100 shown has a structure in which the light-shielding film 2 and the hard mask film 3 are sequentially laminated on the light-transmissive substrate 1.

[0097] [Light-transmissive substrate]

[0098] The light-transmissive substrate 1 can be formed of not only synthetic quartz glass but also quartz glass, aluminosilicate glass, soda-lime glass, low thermal expansion glass (SiO2-TiO2glass, etc.), and the like. Among these, synthetic quartz glass is particularly preferable as a material for forming a light-transmissive substrate of a mask blank because of its high transmittance for ArF exposure light (wavelength 193 nm).

[0099] [Light-shielding film]

[0100] The light-shielding film 2 is a single layer film formed of a material containing silicon and nitrogen, and is preferably a single layer film formed of a material composed of silicon and nitrogen or a material composed of one or more elements selected from semi-metal elements and non-metal elements, silicon, and nitrogen.

[0101] The light-shielding film 2 does not contain a transition metal that can cause a decrease in light resistance to ArF exposure light. In addition, it cannot be denied that a metal element other than a transition metal can cause a decrease in light resistance to ArF exposure light, and therefore, it is preferable that the light-shielding film 2 does not contain a metal element other than a transition metal.

[0102] The light-shielding film 2 can contain any semi-metal element other than silicon. Among these semi-metal elements, it is preferable to contain one or more elements selected from boron, germanium, antimony, and tellurium because it can be expected to improve the electrical conductivity of silicon used as a sputtering target.

[0103] The light-shielding film 2 can contain any non-metal element other than nitrogen. Here, the non-metal element of the present application refers to a non-metal element including a narrow sense non-metal element (nitrogen, carbon, oxygen, phosphorus, sulfur, selenium), a halogen element, and a rare gas. Among these non-metal elements, it is preferable to contain one or more elements selected from carbon, fluorine, and hydrogen. The light-shielding film 2 preferably has an oxygen content of 5 atomic% or less, more preferably 3 atomic% or less, and further preferably does not actively contain oxygen (lower than a detection limit value when performing composition analysis such as XPS (X-ray Photoelectron Spectroscopy)) except for a region of a surface layer described later. The reason for this is that when a silicon nitride-based material film contains oxygen, the value of the extinction coefficient k becomes small, and it is difficult to obtain sufficient light-shielding properties.

[0104] The light-transmissive substrate 1 preferably uses a material in which SiO2is a main component such as synthetic quartz glass. When oxygen is contained in the light-blocking film 2, the difference between the composition of the light-blocking film 2 and the composition of the light-transmissive substrate 1 becomes small, and in dry etching by a fluorine-based gas when a pattern is formed in the light-blocking film 2, there is a problem that etching selectivity with the light-transmissive substrate 1 is difficult to obtain.

[0105] The light-blocking film 2 can contain a rare gas. The rare gas is present in a film formation chamber when a thin film is formed by reactive sputtering, and enables the film formation speed to be increased, improving the production efficiency. Since the rare gas is plasma- ized, it collides with a target material, and as a result, target material constituent particles fly from the target material, and on the way, capture a reactive gas and are deposited on the light-transmissive substrate 1 to form a thin film. During the period from when the target material constituent particles fly from the target material to when they are attached to the light-transmissive substrate 1, the rare gas in the film formation chamber is introduced in a small amount. As the preferred rare gas required for this reactive sputtering, argon, krypton, and xenon can be given. In addition, in order to relieve the stress of the thin film, helium and neon, which have small atomic weights, can be intentionally introduced into the thin film.

[0106] The nitrogen content of the light-blocking film 2 is preferably 50 atomic% or less, and more preferably 45 atomic% or less. The reason for this is that when the nitrogen content exceeds 50 atomic%, the extinction coefficient for ArF exposure light and long-wavelength detection light LW becomes small, and it is difficult to perform sufficient light-blocking or extinction. In addition, the nitrogen content of the light-blocking film 2 is preferably 25 atomic% or more, and more preferably 30 atomic% or more. The reason for this is that when the nitrogen content is less than 25 atomic%, the resistance to washing tends to be insufficient, and in addition, oxidation tends to occur, and the stability of the film over time tends to be impaired.

[0107] In addition, the silicon content of the light-blocking film 2 is preferably 50 atomic% or more, and more preferably 55 atomic% or more. The reason for this is that when the silicon content is less than 50 atomic%, the extinction coefficient for ArF exposure light and long-wavelength detection light LW becomes small, and it is difficult to perform sufficient light-blocking or extinction. In addition, the silicon content of the light-blocking film 2 is preferably 75 atomic% or less, and more preferably 65 atomic% or less. The reason for this is that when the silicon content exceeds 75 atomic%, the resistance to washing tends to be insufficient, and in addition, oxidation tends to occur, and the stability of the film over time tends to be impaired.

[0108] It is preferable that the light-blocking film 2 be formed of a material composed of silicon and nitrogen. In addition, the rare gas is an element that is difficult to detect in composition analysis such as RBS (Rutherford Back-Scattering Spectrometry) or XPS performed on a thin film. However, as described above, when the light-blocking film 2 is formed by reactive sputtering, the rare gas is introduced in a small amount. Therefore, it can be considered that the above-mentioned material composed of silicon and nitrogen includes a material containing a rare gas.

[0109] 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 shadow effect caused by the three-dimensional structure of the mask pattern can be converged within an allowable range. In addition, since 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.

[0110] 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 secure the optical density described below with respect to ArF exposure light, and it is also difficult to obtain sufficient extinction with respect to long wavelength detection light LW.

[0111] The optical density (OD value) of the light shielding film 2 with respect to ArF exposure light is required to be 2.5 or more, and is preferably 2.8 or more. When the optical density is less than 2.5, the light shielding property with respect to ArF exposure light is insufficient, and when exposure is performed using a transfer mask using this mask blank, there is a problem in that the contrast of the projection optical image (transfer image) is likely to be insufficient. On the other hand, in order to thin the light shielding film 2, the optical density of the light shielding film 2 is preferably 4.0 or less.

[0112] The surface reflectance (reflectance of the surface on the opposite side of the light-transmissive substrate 1 side) of the light shielding film 2 with respect to ArF exposure light is required to be 40% or less, and is preferably 38% or less. When the surface reflectance with respect to ArF exposure light exceeds 40%, there is a problem in that the reflection of the exposure light is too large and the projection optical image at the time of transfer exposure is deteriorated.

[0113] In addition, the surface reflectance of the light shielding film 2 with respect to ArF exposure light is preferably 20% or more. The reason for this is that when the surface reflectance with respect to ArF exposure light is less than 20%, the pattern inspection sensitivity is reduced when performing mask pattern inspection using light having a wavelength of 193 nm or thereabout.

[0114] The back surface reflectance (reflectance of the surface on the light-transmissive substrate 1 side) of the light shielding film 2 with respect to ArF exposure light is required to be 40% or less, and is preferably 35% or less. When the back surface reflectance with respect to ArF exposure light exceeds 40%, there is a problem in that the reflection of the exposure light is too large and the projection optical image at the time of transfer exposure is deteriorated.

[0115] Since the optical density, the surface reflectance, and the back surface reflectance of the light shielding film 2 with respect to ArF exposure light are set to the above-described ranges, the refractive index n of the light shielding film 2 with respect to ArF exposure light is preferably 1.6 or more and 2.1 or less, and more preferably 1.7 or more and 2.0 or less. In addition, the extinction coefficient k with respect to ArF exposure light is preferably 1.6 or more and 2.1 or less, and more preferably 1.7 or more and 2.0 or less.

[0116] The light shielding film 2 is required to have a transmittance of 50% or less, preferably 48% or less, for light having a wavelength of 900 nm. The light shielding film 2 is required to have an extinction coefficient k of 0.04 or more, preferably 0.045 or more, for light having a wavelength of 900 nm. In addition, the light shielding film 2 preferably has an extinction coefficient k of 0.1 or less for light having a wavelength of 900 nm. The light shielding film 2 preferably has a refractive index n of 2.5 or more, more preferably 2.7 or more, for light having a wavelength of 900 nm. In addition, the light shielding film 2 preferably has a refractive index n of 3.5 or less for light having a wavelength of 900 nm.

[0117] As described above, the light shielding film 2 composed of a material containing silicon and nitrogen has a characteristic that the longer the wavelength, the higher the transmittance and the smaller the refractive index n and the extinction coefficient k for light having a wavelength of 800 nm or more and 900 nm or less. By using this light splitting characteristic, when the transmittance for light having a wavelength of 900 nm is 50% or less and the extinction coefficient k is 0.04 or more, the long-wavelength detection light LW in the range of 800 nm or more and 900 nm or less can be sufficiently extinguished by the light shielding film 2, and thus the long-wavelength detection light LW can be used to detect the alignment mark formed in the transfer mask manufactured using the mask blank with sufficient contrast. Therefore, it is possible to solve the problem that exposure cannot be performed due to insufficient alignment mark detection sensitivity.

[0118] On the other hand, the light shielding film 2 preferably has a transmittance of 45% or less, more preferably 40% or less, for light having a wavelength of 700 nm. The light shielding film 2 preferably has an extinction coefficient k of 0.10 or more, more preferably 0.15 or more, for light having a wavelength of 700 nm. In addition, the light shielding film 2 preferably has an extinction coefficient k of 0.5 or less for light having a wavelength of 700 nm. In addition, the light shielding film 2 preferably has a refractive index n of 2.8 or more, more preferably 3.0 or more, for light having a wavelength of 700 nm. In addition, the light shielding film 2 preferably has a refractive index n of 3.8 or less for light having a wavelength of 700 nm.

[0119] By the exposure device, it is possible to read the identification mark such as a bar code formed in the transfer mask using detection light having a wavelength shorter than 800 nm (for example, a wavelength in the range of 600 nm to 700 nm). The transfer mask manufactured using the mask blank having the light shielding film 2 having the above-described optical characteristics for light having a wavelength of 700 nm can reliably read the identification code using the above-described detection light having a wavelength shorter than 800 nm.

[0120] The refractive index n and the extinction coefficient k of the thin film are not determined only by the composition of the thin film. The film density and the crystalline state of the thin film and the like are also factors that affect the refractive index n and the extinction coefficient k. Therefore, the conditions when forming the light shielding film 2 by reactive sputtering are adjusted so that the light shielding film 2 has the desired refractive index n and extinction coefficient k, so that the optical density (OD value) with respect to the ArF exposure light, the back surface reflectance, the surface reflectance, and the extinction coefficient k with respect to light of a wavelength of 900 nm converge to predetermined values. The manner in which the light shielding film 2 is provided in the range of the above-described refractive index n and extinction coefficient k is not limited to adjusting the proportion of the mixed gas of the rare gas and the reactive gas when forming the film by reactive sputtering. Many aspects are related to the pressure in the film formation chamber when forming the film by reactive sputtering, the power applied to the target material, the positional relationship between the target material and the light-transmissive substrate, and the like. In addition, these film formation conditions are conditions inherent to the film formation apparatus, and can be appropriately adjusted so that the light shielding film 2 formed has the desired refractive index n and extinction coefficient k.

[0121] The light shielding film 2 can be a single layer film composed of a film in which the composition is uniform in the layer thickness direction except for the surface layer in which natural oxidation occurs or a film in which the film composition is inclined. By being provided as a single layer film, the number of manufacturing steps is reduced, the production efficiency is improved, and at the same time, the manufacturing quality management including defects becomes easy.

[0122] A film that does not actively contain oxygen and contains silicon and nitrogen has high light resistance with respect to ArF exposure light, but has a tendency to have low drug resistance compared to a film that actively contains oxygen and contains silicon and nitrogen. In addition, the surface layer on the opposite side of the light-transmissive substrate 1 side of the light shielding film 2, in the case where a mask blank 100 using a light shielding film 2 that does not actively contain oxygen is used, since mask cleaning or storage in the atmosphere is to be performed on a transfer mask 200 made of the mask blank 100, it is difficult to avoid oxidation of the surface layer of the light shielding film 2. If the surface layer of the light shielding film 2 is oxidized, the surface reflectance of the light shielding film 2 with respect to ArF exposure light changes, and a problem occurs in which the exposure transfer characteristics of the transfer mask 200 change.

[0123] Therefore, it is preferable that the surface layer on the opposite side of the light-transmissive substrate 1 side of the light shielding film 2 actively contain oxygen, but on the other hand, if the light shielding film 2 as a whole contains oxygen, as described above, a problem occurs in which the light shielding property with respect to ArF exposure light or the extinction property with respect to long wavelength detection light LW decreases.

[0124] Therefore, preferably, the light shielding film 2 has a composition gradient in its surface layer, which increases the oxygen content toward the surface on the opposite side of the light-transmissive substrate 1, and the portion other than the surface layer of the light shielding film 2 (the bulk portion of the light shielding film 2) is formed using a material composed of silicon and nitrogen. Here, the material composed of silicon and nitrogen constituting the bulk portion of the light shielding film 2 is a material composed of silicon and nitrogen, or a material composed of one or more elements selected from semi-metal elements and non-metal elements, silicon, and nitrogen. Further, the refractive index n and the extinction coefficient k of the light shielding film 2 in this case with respect to ArF exposure light are values of the entire light shielding film 2 including the surface layer, and the extinction coefficient k of the light shielding film 2 with respect to light of a wavelength of 900 nm is also a value of the entire light shielding film 2 including the surface layer.

[0125] The light shielding film 2 is formed by sputtering, but any sputtering such as DC sputtering, RF sputtering, and ion beam sputtering can be used. In the case where a low-conductivity target (a silicon target, a silicon compound target not containing semi-metal elements or containing a small amount of semi-metal elements, or the like) is used, it is preferable to use RF sputtering or ion beam sputtering, and more preferably RF sputtering in view of the film formation rate.

[0126] As a method of manufacturing the mask blank 100, it is preferable to use a silicon target or a target composed of a material containing one or more elements selected from semi-metal elements and non-metal elements in silicon, and to form the light shielding film 2 on the light-transmissive substrate 1 by reactive sputtering in a sputtering gas containing a nitrogen-based gas and a rare gas.

[0127] The nitrogen-based gas used in the light shielding film formation process can use any gas containing nitrogen. As described above, the light shielding film 2 preferably has a low oxygen content except for its surface layer, and therefore, it is preferable to use a nitrogen-based gas not containing oxygen, and more preferably to use nitrogen gas (N2 gas). Further, the rare gas used in the light shielding film 2 formation process can use any rare gas. As a preferable rare gas, argon, krypton, and xenon can be given. Further, in order to relieve stress of the thin film, helium and neon having small atomic weights can be actively introduced into the thin film.

[0128] As a method of forming the light shielding film 2 having a composition gradient in which the oxygen content increases toward the surface on the opposite side of the light-transmissive substrate 1, in addition to a method of gradually adding oxygen gas as an ambient gas at the final stage of forming the light shielding film 2 by sputtering, a method of performing a post-process such as a heat treatment in a gas containing oxygen, a light irradiation treatment such as a stroboscope in a gas containing oxygen, a treatment of bringing ozone and / or oxygen plasma into contact with the surface of the light shielding film after forming the light shielding film 2 by sputtering can be given.

[0129] On the other hand, in the case where it is preferable to set the surface reflectance of the light shielding film against ArF exposure light to be low (for example, 30% or less), if it is achieved by the light shielding film of the single-layer structure described above, a large nitrogen content is required. In this case, the optical density per unit film thickness of the light shielding film decreases, and in order to ensure the prescribed light shielding performance, it is necessary to increase the film thickness of the light shielding film. In the case where such a low surface reflectance is required, it is preferable to provide the light shielding film in a stacked structure of a lower layer and an upper layer from the light-transmissive substrate side, the lower layer employs the material of the light shielding film of the single-layer structure of the embodiment described above, and the upper layer is formed of a material containing silicon and oxygen.

[0130] That is, the mask blank of the other aspect is characterized in that a light shielding film is provided on a light-transmissive substrate, the light shielding film has a structure in which a lower layer and an upper layer are sequentially stacked from the light-transmissive 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 optical density of the light shielding film against ArF exposure light is 2.5 or more, the surface reflectance of the light shielding film against ArF exposure light is 30% or less, the back surface reflectance of the light shielding film against ArF exposure light is 40% or less, the transmittance of the light shielding film against light of a wavelength of 900 nm is 50% or less, the extinction coefficient k of the lower layer of the light shielding film against light of a wavelength of 900 nm is 0.04 or more, and the thickness of the light shielding film is 60 nm or less.

[0131] In addition, in the mask blank of the other aspect, the lower layer of the light shielding film is preferably formed of a material composed of silicon and nitrogen, or a material composed of one or more elements selected from among semi-metal elements and non-metal elements, silicon, and nitrogen. Furthermore, in the mask blank of the other aspect, the upper layer of the light shielding film is preferably formed of a material composed of silicon and oxygen, or a material composed of one or more elements selected from among semi-metal elements and non-metal elements, silicon, and oxygen. The specific structure of the lower layer of the light shielding film is the same as in the case of the light shielding film of the single-layer structure of the embodiment described above.

[0132] The extinction coefficient k of the upper layer against light having a wavelength of 800 nm or more and 900 nm or less is substantially zero, and the upper layer hardly contributes to the shielding of light having such a wavelength. Therefore, it is preferable to ensure the light shielding performance against light having a wavelength of 800 nm or more and 900 nm or less only by the lower layer of the light shielding film. In addition, the upper layer is required to have a function of reducing the surface reflectance, and thus the light shielding performance against ArF exposure light is low. Therefore, it is preferable to ensure the prescribed optical density against ArF exposure light only by the lower layer of the light shielding film.

[0133] The other aspect of the transfer mask is characterized in that the light-shielding film having a transfer pattern is provided on the light-transmissive substrate, the light-shielding film has a structure in which a lower layer and an upper layer are sequentially stacked from the light-transmissive 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 optical density of the light-shielding film with respect to ArF exposure light is 2.5 or more, the surface reflectance of the light-shielding film with respect to ArF exposure light is 30% or less, the back reflectance of the light-shielding film with respect to ArF exposure light is 40% or less, the transmittance of the light-shielding film with respect to light of a wavelength of 900 nm is 50% or less, the extinction coefficient k of the lower layer of the light-shielding film with respect to light of a wavelength of 900 nm is 0.04 or more, and the thickness of the light-shielding film is 60 nm or less. Further, the other matters of the mask blank and the transfer mask of this aspect (matters related to the light-transmissive substrate, the hard mask film, and the like) are the same as those of the mask blank and the transfer mask of the above-described embodiment.

[0134] [Hard mask film]

[0135] In the mask blank 100 provided with the light-shielding film 2 described above, it is more preferable to further stack a hard mask film 3 formed of a material having etching selectivity with respect to an etching gas used at the time of etching the light-shielding film 2 on the light-shielding film 2. The light-shielding film 2 needs to ensure a prescribed optical density, and thus the thinning of the thickness thereof is limited. The hard mask film 3 only needs to have a film thickness capable of functioning as an etching mask during a period until dry etching of the light-shielding film 2 formed directly below the hard mask film 3 ends, and is basically not limited by optical characteristics. Thus, the thickness of the hard mask film 3 can be greatly thinned compared to the thickness of the light-shielding film 2. Also, the resist film of the organic system only needs to have a film thickness capable of functioning as an etching mask during a period until dry etching of the hard mask film 3 ends, and thus the thickness of the resist film can be greatly thinned compared to the past, and problems such as resist pattern collapse can be suppressed.

[0136] The hard mask film 3 is preferably formed of a material containing chromium (Cr). The material containing chromium has particularly high dry etching resistance with respect to dry etching using a fluorine-based gas such as SF6.

[0137] In a case where the material containing chromium is used for the light-shielding film 2, the film thickness of the light-shielding film 2 is thick, and thus a problem of lateral etching occurs at the time of dry etching of the light-shielding film 2, but in a case where the material containing chromium is used as the hard mask film 3, since the film thickness of the hard mask film 3 is thin, a problem caused by lateral etching is difficult to occur.

[0138] As the material containing chromium, in addition to chromium metal, a material containing one or more elements selected from the group consisting of oxygen, nitrogen, carbon, boron, and fluorine in chromium, such as CrN, CrC, CrON, CrCO, CrCON, and the like, can be given. If these elements are added to chromium metal, the film easily becomes an amorphous film, and the surface roughness of the film and the line edge roughness when dry etching the light shielding film 2 can be suppressed, and thus is preferable.

[0139] In addition, from the viewpoint of dry etching of the hard mask film 3, as the material forming the hard mask film 3, a material containing one or more elements selected from the group consisting of oxygen, nitrogen, carbon, boron, and fluorine in chromium is preferably used.

[0140] Although the chromium-based material is etched by a mixed gas of chlorine-based gas and oxygen, the rate at which chromium metal is etched by the etching gas is not high. By containing one or more elements selected from the group consisting of oxygen, nitrogen, carbon, boron, and fluorine in chromium, the etching rate with respect to the etching gas of the mixed gas of chlorine-based gas and oxygen can be increased. In addition, the chromium-containing material forming the hard mask film 3 can also contain one or more elements of indium, molybdenum, and tin. By containing one or more elements of indium, molybdenum, and tin, the etching rate with respect to the mixed gas of chlorine-based gas and oxygen can be further increased.

[0141] As the material forming the hard mask film 3 other than the chromium-containing material, in addition to a metal such as tantalum (Ta) or tungsten (W), a material containing a metal such as tantalum can also be used. For example, as the tantalum-containing material in this case, in addition to tantalum metal, a material containing one or more elements selected from the group consisting of nitrogen, boron, and carbon in tantalum, and the like, can be given. As specific examples thereof, Ta, TaN, TaO, TaON, TaBN, TaBO, TaBON, TaCN, TaCO, TaCON, TaBCN, TaBOCN, and the like, can be given.

[0142] It is preferable that, in the mask blank 100, a resist film of an organic material is formed in contact with the surface of the hard mask film 3 at a film thickness of 100 nm or less. In the case of a fine pattern corresponding to the DRAM hp32 nm generation, a SRAF (Sub-Resolution Assist Feature) having a line width of 40 nm is sometimes provided on the transfer pattern that should be formed on the hard mask film 3. However, in this case, the aspect ratio of the cross section of the resist pattern can also be as low as 1:2.5, and thus, at the time of development of the resist film, it is possible to suppress damage or peeling of the resist pattern at the time of washing, and the like. Furthermore, the film thickness of the resist film is more preferably 80 nm or less.

[0143] Instead of providing the hard mask film 3 on the mask blank 100, an anti-etching film can be formed directly on the light-blocking film 2. In this case, the structure is simple, and dry etching of the hard mask film 3 is not required when manufacturing the mask for transfer, so the number of manufacturing steps can be reduced. In this case, it is preferable to perform surface treatment such as HMDS (hexamethyldisilazane) treatment on the light-blocking film 2 before forming the anti-etching film.

[0144] In addition, as described below, the mask blank of the present application is a mask blank suitable for a binary mask, but is not limited to a binary mask, and can be used as a mask blank for an alternating (Levenson) phase shift mask or a mask blank for a CPL (Chromeless Phase Lithography) mask.

[0145] [Mask for transfer]

[0146] Figure 4 A cross-sectional schematic view showing the process of manufacturing a mask for transfer (binary mask) 200 from the mask blank 100 according to the embodiment of the present application.

[0147] The mask for transfer 200 according to the embodiment of the present application is a binary mask provided with a light-blocking film 2 (light-blocking film pattern 2a) having a transfer pattern on a light-transmissive substrate 1, characterized in that the light-blocking film is a single layer film formed of a material containing silicon and nitrogen, the optical density with respect to exposure light of an ArF excimer laser is 2.5 or more, the surface reflectance is 40% or less, the back surface reflectance is 40% or less, the transmittance with respect to light of 900 nm wavelength is 50% or less, the extinction coefficient is 0.04 or more, and the thickness is 60 nm or less.

[0148] Matters related to the light-transmissive substrate 1 and the light-blocking film 2 of the mask for transfer 200 are the same as those of the mask blank 100, and the mask for transfer 200 has the same technical features as the mask blank 100.

[0149] In addition, the manufacturing method of the mask for transfer 200 of the present application uses the above-described mask blank 100, and is characterized by comprising: a process of forming a pattern including a transfer pattern and an alignment mark on the hard mask film 3 by dry etching; a process of forming a pattern including a transfer pattern and an alignment mark on the light-blocking film 2 by dry etching with the hard mask film 3 (hard mask pattern 3a) having these patterns as a mask; and a process of removing the hard mask pattern 3a.

[0150] This mask for transfer 200 can perform detection of the alignment mark with sufficient contrast even in the case of using an exposure device that performs alignment using long wavelength detection light LW, and thus can be executed on the premise that the mask alignment operation is not erroneous.

[0151] 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.

[0152] 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.

[0153] 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.

[0154] 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.

[0155] 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.

[0156] Next, the resist pattern 4a (refer to) is removed by ashing or resist stripping solution. Figure 4 (d)).

[0157] 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 the fluorine-based gas, a gas containing F can be used, but SF6 is preferred. As a gas other than SF6, CHF3, CF4, C2F6, C4F8, etc. can be mentioned, but the fluorine-based gas containing C has a high etching rate for the light-transmissive substrate 1 as a glass material. SF6 has a small damage to the light-transmissive substrate 1, and thus is preferred. Further, He, etc. can be added to SF6.

[0158] After that, the hard mask pattern 3a is removed using a chromium etching solution, and the transfer mask 200 is obtained by a prescribed treatment such as washing (refer to FIG. 2C). Figure 4 (f)). Further, the removal process of the hard mask pattern 3a can be performed by dry etching using a mixed gas of chlorine and oxygen. Here, as the chromium etching solution, a mixture containing cerium ammonium nitrate and perchloric acid can be mentioned.

[0159] Further, the case where the transfer mask 200 is a binary mask is described here, but the transfer mask of the present application is not limited to the binary mask, and can be used for an alternating phase shift mask and a CPL mask. That is, in the case of the alternating phase shift mask, the light shielding film can use the light shielding film of the present application. In addition, in the case of the CPL mask, the light shielding film of the present application can be used mainly in the region of the light shielding belt including the outer periphery. Also, as in the case of the binary mask, in the case of the alternating phase shift mask and the CPL mask, the alignment mark detection can be performed with sufficient contrast by the long wavelength detection light LW.

[0160] Further, the manufacturing method of the semiconductor device of the present application is characterized in that the resist film is exposed and transferred to the semiconductor substrate using the transfer mask 200 described above or the transfer mask 200 manufactured by the mask blank 100 described above.

[0161] The transfer mask 200 or the mask blank 100 of the present application has the effect described above, and thus, when the resist film formed on the semiconductor wafer is exposed using the transfer mask of the present application, the alignment mark detection can be performed with sufficient sensitivity. Therefore, the exposure operation can not be stopped due to insufficient sensitivity of the alignment mark detection, and the semiconductor device can be manufactured in a manner having high ArF light resistance.

[0162] Example

[0163] Hereinafter, the embodiments of the present application will be further specifically described by examples.

[0164] (Example 1)

[0165] [Manufacture of Mask Blank]

[0166] A light-transmissive substrate 1 composed of synthetic quartz glass having a size of about 152 mm x about 152 mm and a thickness of about 6.25 mm was prepared. After the end surface and the main surface of the light-transmissive substrate 1 were polished to a prescribed surface roughness, prescribed cleaning treatment and drying treatment were performed.

[0167] Next, the light-transmissive substrate 1 was set in a single-wafer RF sputtering device, and a silicon (Si) target was used to form a light-blocking film 2 composed of silicon and nitrogen on the light-transmissive substrate 1 by reactive sputtering (RF sputtering) at a thickness of 57 nm using a mixed gas of krypton (Kr), helium (He), and nitrogen (N2) (flow rate ratio Kr:He:N2 = 10:100:1, pressure = 0.1 Pa) as a sputtering gas with the power of the RF power source set to 1.5 kW. Here, the composition of the light-blocking film 2 was determined by X-ray photoelectron spectroscopy (XPS). The same applies to the determination method of the film composition of other films below.

[0168] Next, the light-transmissive substrate 1 on which the light-blocking film 2 was formed was subjected to heat treatment in the atmosphere at a heating temperature of 500°C for 1 hour for the purpose of adjusting the stress of the film. The results of determining the spectral transmittance of the light-blocking film 2 after the heat treatment using a spectrophotometer (manufactured by Agilent Technologies, Cary 4000) are shown in FIG. 6. Figure 2 The transmittance of long-wavelength light of 800 nm or more and 900 nm or less monotonously increased as the wavelength increased, and the transmittance at a wavelength of 800 nm, 850 nm, 890 nm, and 900 nm was 42.8%, 44.9%, 46.7%, and 47.0%, respectively. In addition, the optical density (OD value) for an ArF excimer laser light (wavelength 193 nm) was 2.96.

[0169] In addition, the refractive index n and the extinction coefficient k of the light-blocking film 2 were determined using a spectroscopic ellipsometer (M-2000D manufactured by J. A. Woollam). The results of determining the spectral properties (i.e., the refractive index n and the extinction coefficient k for each wavelength) are shown in FIG. 7. Figure 3 The refractive index n at a wavelength of 193 nm was 1.830, and the extinction coefficient k was 1.785, the refractive index n at a wavelength of 800 nm was 3.172, and the extinction coefficient k was 0.093, the refractive index n at a wavelength of 850 nm was 3.137, and the extinction coefficient k was 0.066, the refractive index n at a wavelength of 890 nm was 3.112, and the extinction coefficient k was 0.050, and the refractive index n at a wavelength of 900 nm was 3.106, and the extinction coefficient k was 0.047.

[0170] The surface reflectance and the back reflectance of the light shielding film 2 at a wavelength of 193 nm were measured using a spectrophotometer (Hitachi High-Technologies Corporation, U-4100), and the values were 37.1%, 30.0%, respectively.

[0171] Next, the light-transmissive substrate 1 on which the light shielding film 2 after heat treatment was formed was set in a single- wafer DC sputtering device, and a Cr target was used to perform reactive sputtering (DC sputtering) in an atmosphere of a mixed gas of argon (Ar) and nitrogen (N2) to form a hard mask film 3 composed of a CrN film having a film thickness of 5 nm. The film composition ratio of this film was Cr: 75 at%, N: 25 at% as measured by XPS. Further, heat treatment (280°C) was performed at a temperature lower than the heat treatment by the light shielding film 2 to perform stress adjustment of the hard mask film 3.

[0172] Through the above steps, the mask blank 100 having a structure in which the light shielding film 2 and the hard mask film 3 are stacked was manufactured on the light-transmissive substrate 1.

[0173] [Manufacture of transfer mask]

[0174] Next, the mask blank 100 of Example 1 was used to manufacture the transfer mask (binary mask) 200 of Example 1 through the following steps.

[0175] First, the mask blank 100 of Example 1 (refer to Figure 4 (a)) was prepared, and a resist film composed of a chemical amplification resist for electron beam drawing was formed to a film thickness of 80 nm in contact with the surface of the hard mask film 3. Next, a pattern to be formed on the light shielding film 2 was drawn on the resist film with an electron beam, and a prescribed development treatment and a cleaning treatment were performed to form a resist pattern 4a (refer to Figure 4 (b)). Further, in the pattern after electron beam drawing, alignment marks and the like were included in addition to the transfer pattern.

[0176] Next, dry etching using a mixed gas of chlorine and oxygen (gas flow ratio Cl2:O2 = 4:1) was performed with the resist pattern 4a as a mask to form a pattern (hard mask pattern 3a) on the hard mask film 3 (refer to Figure 4 (c)).

[0177] Next, the resist pattern 4a was removed (refer to Figure 4 (d)). Next, dry etching using a fluorine-based gas (a mixed gas of SF6 and He) was performed with the hard mask pattern 3a as a mask to form a pattern (light shielding film pattern 2a) on the light shielding film 2 (refer to Figure 4 (e)).

[0178] After that, the hard mask pattern 3a is removed using a chromium etching solution containing cerium ammonium nitrate and perchloric acid, and the transfer mask 200 is obtained by prescribed treatments such as washing (refer to Figure 4 (f)).

[0179] The transfer mask 200 of Example 1 thus produced was placed in an exposure apparatus using long wavelength detection light LW to perform detection of the alignment mark, and as a result, the mark detection was able to be performed with sufficient contrast. Furthermore, the mask alignment operation was able to be performed without error at one time.

[0180] Next, the transfer mask 200 was subjected to an irradiation treatment with a cumulative dose of 40 kJ / cm 2 The CD of the light shielding film pattern 2a before and after the irradiation treatment changed by 1.2 nm or less, which is within the range of CD change that can be used as the light shielding film pattern 2a. Thus, it was found that the light shielding film pattern 2a had sufficient ArF light resistance in terms of practical use.

[0181] The transfer mask 200 of Example 1 was placed on the mask stage of the exposure apparatus, and as a result of exposure transfer onto a resist film on a semiconductor device, a circuit pattern was able to be formed with high precision without causing mask misalignment.

[0182] (Comparative Example 1)

[0183] [Manufacture of Mask Blank]

[0184] The mask blank of Comparative Example 1 can be manufactured by the same steps as the mask blank 100 of Example 1, except that the light shielding film is treated as follows.

[0185] The method of forming the light shielding film of Comparative Example 1 is as follows.

[0186] A light-transmissive substrate 1 was placed in a single-wafer RF sputtering apparatus, and a silicon (Si) target was used to form a light shielding film composed of silicon and nitrogen (Si:N = 48 atomic%:52 atomic%) on the light-transmissive substrate 1 at a thickness of 100 nm by reactive sputtering (RF sputtering) using a mixed gas of krypton (Kr), helium (He), and nitrogen (N2) as the sputtering gas.

[0187] Next, the light-transmissive substrate 1 on which the light-blocking film was formed was subjected to heat treatment in the atmosphere at a heating temperature of 500°C for 1 hour in order to adjust the stress of the film. The results of measuring the spectral transmittance of the light-blocking film after the heat treatment using a spectrophotometer (Cary 4000, Agilent Technologies) were that the transmittance at wavelengths of 800 nm, 850 nm, 890 nm, and 900 nm was 74.2%, 74.2%, 73.9%, and 73.9%, respectively. In addition, the optical density (OD value) for ArF excimer laser light (wavelength: 193 nm) was 2.9.

[0188] In addition, the refractive index n and the extinction coefficient k of the light-blocking film were measured using a spectroscopic ellipsometer (M-2000D, J. A. Woollam). The refractive index n at a wavelength of 193 nm was 2.4, and the extinction coefficient k was 1.0. The refractive index n at a wavelength of 800 nm was 2.3, and the extinction coefficient k was 0. The refractive index n at a wavelength of 850 nm was 2.3, and the extinction coefficient k was 0. The refractive index n at a wavelength of 890 nm was 2.3, and the extinction coefficient k was 0. The refractive index n at a wavelength of 900 nm was 2.3, and the extinction coefficient k was 0.

[0189] The surface reflectance and the back surface reflectance of the light-blocking film at a wavelength of 193 nm were measured using a spectrophotometer (U-4100, Hitachi High-Tech). The values were 21% and 15%, respectively.

[0190] [Manufacture of a mask for transfer]

[0191] Next, the mask blank of Comparative Example 1 was used to manufacture a mask for transfer (binary mask) of Comparative Example 1 by the same steps as in Example 1.

[0192] The mask for transfer of Comparative Example 1 manufactured was placed in an exposure device using long-wavelength detection light LW to detect an alignment mark, and the result was that the mark detection could not be performed with sufficient contrast. Furthermore, mask alignment errors occurred repeatedly.

[0193] Next, the mask for transfer of Comparative Example 1 was subjected to an irradiation treatment with a cumulative irradiation dose of 40 kJ / cm2using ArF excimer laser light. 2 The CD variation of the light-blocking film pattern before and after the irradiation treatment was 1.2 nm or less, which was a CD variation that was within a range that could be used as a light-blocking film pattern, and the light-blocking film pattern had sufficient ArF light resistance in practical terms.

[0194] The mask for transfer 200 of Comparative Example 1 was placed on a mask stage of an exposure device to perform exposure transfer on a resist film on a semiconductor device, and mask alignment failures occurred repeatedly, and exposure for manufacturing a semiconductor device could not be performed reliably.

[0195] Symbol Explanation

[0196] 1 light-transmitting substrate

[0197] 2 light-blocking film

[0198] 2a light-blocking film pattern

[0199] 3 hard mask film

[0200] 3a hard mask pattern

[0201] 4a resist pattern

[0202] 100 mask blank

[0203] 200 transfer mask (binary mask)

Claims

1. A mask blank comprising a light-shielding film on a light-transmissive substrate, characterized in that: the light-shielding film is a single layer film formed of a material containing silicon and nitrogen, the refractive index n of the light-shielding film with respect to exposure light of an ArF excimer laser is 1.6 or more and 2.1 or less, the extinction coefficient k of the light-shielding film with respect to the exposure light is 1.6 or more and 2.1 or less, the extinction coefficient k of the light-shielding film with respect to light of a wavelength of 900 nm is 0.04 or more, and the thickness of the light-shielding film is 40 nm or more and 60 nm or less.

2. The mask blank according to claim 1, characterized in that: the refractive index n of the light-shielding film with respect to light of a wavelength of 900 nm is 3.5 or less.

3. The mask blank according to claim 1 or 2, characterized in that: the extinction coefficient k of the light-shielding film with respect to light of a wavelength of 700 nm is 0.10 or more.

4. The mask blank according to claim 1 or 2, characterized in that: the refractive index n of the light-shielding film with respect to light of a wavelength of 700 nm is 3.8 or less.

5. The mask blank according to claim 1 or 2, characterized in that: the light-shielding film is formed of a material composed of silicon and nitrogen, or formed of a material composed of one or more elements selected from semi-metal elements and non-metal elements other than silicon and nitrogen.

6. The mask blank according to claim 1 or 2, characterized in that: the light-shielding film has a composition gradient portion in a surface layer thereof, the composition gradient portion increases the oxygen content toward a surface on the opposite side of the light-transmissive substrate, and the light-shielding film other than the surface layer is formed of a material composed of silicon and nitrogen, or formed of a material composed of one or more elements selected from semi-metal elements and non-metal elements other than silicon and nitrogen.

7. The mask blank according to claim 1 or 2, characterized in that: the nitrogen content of the light-shielding film is 50 atomic% or less.

8. The mask blank according to claim 1 or 2, characterized in that: the silicon content of the light-shielding film is 50 atomic% or more.

9. The mask blank according to claim 1 or 2, characterized in that: a hard mask film composed of a material containing chromium is provided on the light-shielding film.

10. A transfer mask comprising a light-shielding film having a transfer pattern on a light-transmissive substrate, characterized in that: the light-shielding film is a single layer film formed of a material containing silicon and nitrogen, the refractive index n of the light-shielding film with respect to exposure light of an ArF excimer laser is 1.6 or more and 2.1 or less, the extinction coefficient k of the light-shielding film with respect to the exposure light is 1.6 or more and 2.1 or less, the extinction coefficient k of the light-shielding film with respect to light of a wavelength of 900 nm is 0.04 or more, and the thickness of the light-shielding film is 40 nm or more and 60 nm or less.

11. The transfer mask according to claim 10, characterized in that: the refractive index n of the light-shielding film with respect to light of a wavelength of 900 nm is 3.5 or less.

12. The transfer mask according to claim 10 or 11, characterized in that: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The light shielding film has an extinction coefficient k of 0.10 or more for light of a wavelength of 700 nm.

13. The transfer mask according to claim 10 or 11, wherein The light shielding film has a refractive index n of 3.8 or less for light of a wavelength of 700 nm.

14. The transfer mask according to claim 10 or 11, wherein The light shielding film is formed of a material composed of silicon and nitrogen, or a material composed of one or more elements selected from semi-metal elements and non-metal elements other than silicon and nitrogen.

15. The transfer mask according to claim 10 or 11, wherein The light shielding film has a composition gradient portion in which the oxygen content is increased toward the surface on the opposite side of the transparent substrate side, and the light shielding film other than the surface layer is formed of a material composed of silicon and nitrogen, or a material composed of one or more elements selected from semi-metal elements and non-metal elements other than silicon and nitrogen.

16. The transfer mask according to claim 10 or 11, wherein The light shielding film has a nitrogen content of 50 atomic % or less.

17. The transfer mask according to claim 10 or 11, wherein The light shielding film has a silicon content of 50 atomic % or more.

18. A method for manufacturing a semiconductor device, comprising: a step of transferring a resist film on which a transfer pattern is exposed to light to a semiconductor substrate using the transfer mask according to any one of claims 10 to 17. ​

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