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

Abstract

The present invention provides a mask blank (100) that utilizes a light-shielding film (2) composed of a single-layer film formed of a silicon nitride-based material to have high light-shielding performance for ArF exposure light and can reduce the EMF deviation of the pattern of the light-shielding film. The mask blank has a light-shielding film on a translucent substrate (1). The optical density of the light-shielding film for ArF exposure light is greater than 3.0. The refractive index n and attenuation coefficient k of the light-shielding film for ArF exposure light simultaneously satisfy the relationship defined by the following formulas (1), (2) and (3), n≦0.0733×k 2 +0.4069×k+1.0083···Formula (1), n≧0.0637×k 2 -0.1096×k+0.9585···Formula (2), n≧0.7929×k 2 -2.1606×k+2.1448···Formula (3).

Description

[0001] This application is a divisional application of the invention patent application with the application date of February 28, 2018, application number 201880016943.X, and invention name “Mask blank, transfer mask and manufacturing method of semiconductor device”. Technical Field

[0002] The present invention relates to a mask blank, a transfer mask manufactured using the mask blank, and a method for manufacturing a semiconductor device using the transfer mask. Background Art

[0003] Generally speaking, in the manufacturing process of semiconductor devices, photolithography is used to form fine patterns. In addition, in the formation of this fine pattern, a plurality of transfer masks are usually used. When the pattern of the semiconductor device is miniaturized, it is necessary not only to miniaturize the mask pattern formed on the transfer mask, but also to shorten the wavelength of the exposure light source used in the photolithography. As far as the exposure light source used in the manufacture of semiconductor devices is concerned, in recent years, the shorter wavelength of the light source has been continuously developed from KrF excimer laser (wavelength 248nm) to ArF excimer laser (wavelength 193nm).

[0004] One type of transfer mask is a halftone phase-shift mask. Molybdenum silicide (MoSi)-based materials are widely used in the phase-shift films of halftone phase-shift masks. However, as disclosed in Patent Document 1, it has recently been revealed that MoSi-based films have low resistance to ArF excimer laser exposure light (hereinafter referred to as ArF exposure light) (so-called ArF light resistance). In Patent Document 1, a patterned MoSi-based film is subjected to plasma treatment, UV irradiation treatment, or heat treatment to form a passivation film on the surface of the patterned MoSi-based film, thereby improving ArF light resistance.

[0005] On the other hand, Patent Document 2 discloses a phase shift mask including a phase shift film made of SiN, and Patent Document 3 describes that it has been confirmed that a phase shift film made of SiN has high ArF light resistance.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2010-217514

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 7-159981

[0010] Patent Document 3: Japanese Patent Application Laid-Open No. 2014-137388 Summary of the Invention

[0011] Problems to be solved by the invention

[0012] The problem of ArF light resistance in transfer masks is not limited to phase-shift masks, but also occurs in binary masks. In recent years, the miniaturization of the light-shielding pattern of the binary mask has been continuously developed. The light-shielding film of the chromium-based material that has been widely used in the past is patterned by dry etching with an etching gas with low anisotropy (a mixture of chlorine-based gas and oxygen gas), and therefore, it is difficult to meet the requirements of miniaturization. Therefore, in recent years, molybdenum silicide-based materials have begun to be used in the light-shielding film of the mask blank for manufacturing binary masks. However, as mentioned above, the thin film of the transition metal silicide-based material has the problem of low ArF light resistance. In order to solve this problem, as in the case of the phase-shift film, the simplest method is to apply silicon nitride-based materials to the light-shielding film of the binary mask. The light-shielding film of the binary mask requires higher light-shielding performance for ArF exposure light (for example, the optical density (OD) for ArF exposure light is 3.0 or more). Furthermore, compared to phase shift films, the binary mask's light-shielding film tends to have higher surface reflectivity (the reflectivity of the surface opposite the substrate side of the light-shielding film) and backside reflectivity (the reflectivity of the surface on the substrate side of the light-shielding film) for ArF exposure light. Conventional light-shielding films made of chromium-based materials and transition metal silicide-based materials employ a laminated structure of a light-shielding layer and an anti-reflection layer to reduce surface and backside reflectivity for ArF exposure light. Silicon nitride-based materials have lower light-shielding performance for ArF exposure light than chromium-based materials and transition metal silicide-based materials.

[0013] In recent binary masks, thicker light-shielding film patterns can lead to increased deviations (corrections to pattern line width, etc., hereinafter referred to as EMF deviations) due to electromagnetic field (EMF) effects. To reduce EMF deviations in light-shielding film patterns, thinning the film and minimizing the phase shift (the phase difference between exposure light passing through the film and exposure light transmitted through air a distance equal to the film thickness) are effective.

[0014] When forming a light-shielding film using a silicon nitride-based material with low light-shielding performance, the thickness of the light-shielding film must be increased to ensure high light-shielding performance. Therefore, it is difficult to reduce EMF variation in the light-shielding film pattern, which poses a problem.

[0015] EMF variation significantly impacts the CD accuracy of the pattern line width transferred to the resist on the wafer. Therefore, it is necessary to simulate electromagnetic field effects and correct the transfer pattern created in the transfer mask to mitigate the effects of EMF variation. The calculation of this transfer pattern correction becomes increasingly complex as EMF variation increases. Furthermore, the corrected transfer pattern becomes increasingly complex as EMF variation increases, placing a significant burden on transfer mask production.

[0016] Therefore, the present invention was developed to address existing problems. Its purpose is to provide a mask blank having a light-shielding film on a translucent substrate. The light-shielding film, composed of a single layer of a silicon nitride-based material, exhibits high light-shielding performance against ArF exposure light and reduces EMF variation in the light-shielding film pattern. Another object of the present invention is to provide a transfer mask manufactured using the mask blank. Yet another object of the present invention is to provide a method for manufacturing a semiconductor device using such a transfer mask.

[0017] Solutions to Problems

[0018] In order to achieve the above-mentioned objects, the present invention has the following aspects.

[0019] (Form 1)

[0020] A mask blank is provided, comprising a light-shielding film on a light-transmitting substrate, wherein:

[0021] The light shielding film is a single-layer film formed of a material composed of silicon and nitrogen, or a single-layer film formed of a material composed of one or more elements selected from semi-metallic elements and non-metallic elements, silicon and nitrogen.

[0022] The optical density of the light-shielding film with respect to exposure light of the ArF excimer laser is 3.0 or more.

[0023] The attenuation coefficient k of the light-shielding film is less than 2.6,

[0024] The refractive index n of the light-shielding film is greater than or equal to 0.8.

[0025] The refractive index n and attenuation coefficient k of the light-shielding film for the exposure light simultaneously satisfy the relationships defined by the following equations (1), (2), and (3):

[0026] n≦0.0733×k 2 +0.4069×k+1.0083···Formula (1),

[0027] n≧0.0637×k 2 -0.1096×k+0.9585···Formula (2),

[0028] n≧0.7929×k 2 -2.1606×k+2.1448···Formula (3).

[0029] (Form 2)

[0030] The mask blank according to aspect 1 is characterized in that:

[0031] The deviation of the nitrogen content in the thickness direction of the light-shielding film in a region excluding the surface layer on the light-transmitting substrate side and the surface layer on the side opposite to the light-transmitting substrate is within 5 atomic %.

[0032] (Form 3)

[0033] The mask blank according to aspect 1 or 2 is characterized in that a hard mask made of a material containing chromium is provided on the light-shielding film.

[0034] (Form 4)

[0035] A transfer mask comprises a light-shielding film having a transfer pattern on a light-transmitting substrate, wherein:

[0036] The light shielding film is a single-layer film formed of a material composed of silicon and nitrogen, or a single-layer film formed of a material composed of one or more elements selected from semi-metallic elements and non-metallic elements, silicon and nitrogen.

[0037] The optical density of the light-shielding film with respect to exposure light of the ArF excimer laser is 3.0 or more.

[0038] The attenuation coefficient k of the light-shielding film is less than 2.6,

[0039] The refractive index n of the light-shielding film is greater than or equal to 0.8.

[0040] The refractive index n and attenuation coefficient k of the light-shielding film for the exposure light simultaneously satisfy the relationships defined by the following equations (1), (2), and (3):

[0041] n≦0.0733×k 2 +0.4069×k+1.0083···Formula (1),

[0042] n≧0.0637×k 2 -0.1096×k+0.9585···Formula (2),

[0043] n≧0.7929×k 2 -2.1606×k+2.1448···Formula (3).

[0044] (Form 5)

[0045] The transfer mask according to form 4 is characterized in that the deviation of the nitrogen content in the thickness direction of the light-shielding film except for the surface layer on the transparent substrate side and the surface layer on the side opposite to the transparent substrate is within 5 atomic %.

[0046] (Form 6)

[0047] A method for manufacturing a semiconductor device, characterized by comprising the step of transferring a transfer pattern by exposing a resist film on a semiconductor substrate using the transfer mask according to aspect 4 or 5.

[0048] Effects of the Invention

[0049] The mask blank of the present invention is characterized in that a light-shielding film is provided on a light-transmitting substrate, wherein the light-shielding film is a single-layer film formed of a silicon nitride-based material, has an optical density of 3.0 or greater with respect to ArF exposure light, and the refractive index n and attenuation coefficient k of the light-shielding film with respect to ArF exposure light simultaneously satisfy the relationships defined in the following equations (1) and (2). Due to this light-shielding film structure, the light-shielding film has an optical density of 3.0 or greater with respect to ArF exposure light, and the refractive index n and attenuation coefficient k of the light-shielding film with respect to ArF exposure light simultaneously satisfy the relationships defined in the following equations (1) to (3). Therefore, the light-shielding film has high light-shielding performance with respect to ArF exposure light, and can reduce EMF deviation of the light-shielding film pattern.

[0050] n≦0.0733×k 2 +0.4069×k+1.0083···Formula (1)

[0051] n≧0.0637×k 2 -0.1096×k+0.9585···Formula (2),

[0052] n≧0.7929×k 2 -2.1606×k+2.1448···Formula (3).

[0053] The transfer mask of the present invention is characterized in that the light-shielding film of the transfer pattern has the same characteristics as the light-shielding film of the mask blank of the present invention described above. By using this transfer mask, the EMF variation of the light-shielding film pattern can be reduced, thereby enabling production without significant burden. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is a graph showing the relationship between the refractive index n and the attenuation coefficient k derived from the simulation results, and the film thickness d, the phase difference φ, and the surface reflectivity Rf.

[0055] Figure 2 This is a graph showing the relationship between the refractive index n and the attenuation coefficient k derived from simulation results, and the surface reflectivity Rf and the back surface reflectivity Rb.

[0056] Figure 3 It is a cross-sectional view showing the structure of a mask blank according to an embodiment of the present invention.

[0057] Figure 4(a) to (f) are cross-sectional views showing the steps of manufacturing the transfer mask according to the embodiment of the present invention. DETAILED DESCRIPTION

[0058] First, the process leading to the completion of the present invention will be described.

[0059] When a light-shielding film is formed using a silicon-based material (e.g., a material composed entirely of silicon) that does not contain oxygen or nitrogen, which is a major factor in reducing light-shielding performance, a light-shielding film having a predetermined optical density (e.g., an optical density (OD) of 3.0 or greater for ArF exposure light) can be formed with a thinner film thickness. However, silicon atoms not bonded to other elements tend to readily bond with oxygen in the air. When manufacturing a mask blank having a light-shielding film composed of silicon on a translucent substrate, there is a problem that oxidation progresses when the mask blank is exposed to the atmosphere after manufacturing, resulting in a significant change in the optical properties (particularly light-shielding performance) from those when the light-shielding film was initially formed.

[0060] On the other hand, in recent years, in the process of manufacturing transfer masks using mask blanks, if black spots are detected as a result of mask inspection of the pattern of the light-shielding film, the black spots are widely corrected by EB defect correction technology. The EB defect correction is to supply a non-excited fluorine-based gas such as XeF2 gas to the vicinity of the black spots, and at the same time irradiate the black spot portion with an electron beam, thereby removing the black spots. The EB defect correction can remove only the black spot portion by fully ensuring that the etching rate of the non-excited fluorine-based gas for the light-shielding film portion excited by the electron beam irradiation (black spot portion) is different from the etching rate of the non-excited fluorine-based gas for the unexcited light-shielding film portion. Silicon-based materials that do not contain oxygen or nitrogen have low resistance to the non-excited fluorine-based gas and are easily etched even in a state not irradiated by an electron beam (non-excited state) (this is called spontaneous etching). Therefore, when performing EB defect correction on a light-shielding film made of a silicon-based material that does not contain oxygen or nitrogen, there is a problem in that spontaneous etching of the pattern sidewalls of the light-shielding film other than black spots is likely to proceed.

[0061] Due to the two problems mentioned above, the material used to form the light-shielding film needs to be a material containing nitrogen or oxygen in silicon. Compared with the material containing nitrogen in silicon, the light-shielding performance of the material containing oxygen in silicon is significantly reduced. Taking this into account, when using a silicon-based material to form a light-shielding film, it is preferred to use a material containing nitrogen in silicon (silicon nitride-based material). The light-shielding film made of silicon nitride-based material has the following characteristics: as the nitrogen content in the film increases, the attenuation coefficient k of the light-shielding film for ArF exposure light (hereinafter referred to as the attenuation coefficient k) decreases, and the refractive index n (hereinafter referred to as the refractive index n) for ArF exposure light increases. As the attenuation coefficient k of the light-shielding film decreases, the optical density of the light-shielding film decreases. Therefore, in order to ensure the specified optical density in the light-shielding film, the film thickness of the light-shielding film needs to be increased. In addition, as the refractive index n of the light-shielding film increases, the phase difference of the light-shielding film will increase. The increase in the refractive index n of the light-shielding film and the decrease in the attenuation coefficient k both lead to an increase in the EMF deviation of the light-shielding film. Therefore, the refractive index n and the attenuation coefficient k of the light-shielding film made of a silicon nitride-based material need to be controlled within a predetermined range.

[0062] The present inventors have diligently studied the relationship between the refractive index n and the attenuation coefficient k of a light-shielding film used in mask blanks for manufacturing binary masks, ensuring both a desired optical density (OD = 3.0 or greater) and sufficiently reduced EMF variation. They determined that the use of a light-shielding film employing the following technical means could ensure the desired optical density for ArF exposure light while also sufficiently reducing EMF variation, leading to the completion of the present invention.

[0063] To achieve the present invention, an optical simulation of a light-shielding film was first conducted. In the optical simulation, the exposure light was ArF excimer laser light, and the light-shielding film was assumed to be a single-layer thin film composed of an optically uniform material. While varying the refractive index n and attenuation coefficient k within the range of 0.8 to 2.6 and the attenuation coefficient k within the range of 1.0 to 2.6, the phase difference φ, surface reflectivity Rf, and back reflectivity Rb at a film thickness d when the optical density (OD) reached 3.0 were determined.

[0064] Then, based on the simulation results, the relationship between the refractive index n and the attenuation coefficient k and the phase difference φ, the relationship between the refractive index n and the attenuation coefficient k and the film thickness d, the relationship between the refractive index n and the attenuation coefficient k and the surface reflectivity Rf, and the relationship between the refractive index n and the attenuation coefficient k and the back reflectivity Rb were sorted out. Then, based on the sorted relationships, the relationship between the refractive index n and the attenuation coefficient k in each case of the phase difference φ of 90 degrees, 80 degrees, 0 degrees, and -20 degrees was obtained ( Figure 1 ), the relationship between the refractive index n and the attenuation coefficient k when the film thickness d is 80nm, 70nm and 60nm ( Figure 1), the relationship between the surface reflectivity Rf and the refractive index n and the attenuation coefficient k when the surface reflectivity Rf is 50%, 45% and 40% ( Figure 1 , Figure 2 ), and the relationship between the back reflectivity Rb and the refractive index n and the attenuation coefficient k in each case of 50%, 45% and 40% ( Figure 2 ). Figure 1 and Figure 2 A graph showing the relationship thus obtained is drawn.

[0065] Figure 1 This is a graph showing the relationship between the refractive index n and the attenuation coefficient k derived from the simulation results, and the film thickness d, the phase difference φ, and the surface reflectivity Rf. Figure 2 This is a graph showing the relationship between the refractive index n and attenuation coefficient k derived from simulation results and the surface reflectivity Rf and back reflectivity Rb. Figure 1 and Figure 2 In addition, the data used to obtain the fitting curves of the following equations (a) to (m) are shown in FIG. Figure 1 and Figure 2 The data in the table is shown in Figure 2. The fitting curves below may vary slightly depending on the calculation method. However, the changes in the refractive index n and attenuation coefficient k caused by the changes in the fitting formula have a minimal impact on the retardation, film thickness, surface reflectivity, and back surface reflectivity of the light-shielding film, and are within the acceptable range.

[0066] like Figure 1 As shown in , the fitting curve when the phase difference φ is 90 degrees is expressed by the following formula (a), the fitting curve when the phase difference φ is 80 degrees is expressed by the following formula (b), the fitting curve when the phase difference φ is -20 degrees is expressed by the following formula (c), and the fitting curve when the phase difference φ is 0 degrees is expressed by the following formula (d).

[0067] n=0.0733×k 2 +0.4069×k+1.0083···Formula (a)

[0068] n=0.0966×k 2 +0.3660×k+0.9956···Formula (b)

[0069] n=0.0637×k 2 -0.1096×k+0.9585···Formula (c)

[0070] n=0.0636×k 2 -0.0147×k+0.9613···Formula (d)

[0071] like Figure 1As shown in , the fitting curve when the film thickness d is 80 nm is expressed by the following formula (e), the fitting curve when the film thickness d is 70 nm is expressed by the following formula (f), and the fitting curve when the film thickness d is 60 nm is expressed by the following formula (g).

[0072] n=29.316×k 2 -92.292×k+72.671···Formula (e)

[0073] n=23.107×k 2 -82.037×k+73.115···Formula (f)

[0074] n=12.717×k 2 -54.382×k+58.228···Formula (g)

[0075] like Figure 1 and Figure 2 As shown in FIG, the fitting curve when the surface reflectance Rf is 50% is expressed by the following formula (h), the fitting curve when the surface reflectance Rf is 45% is expressed by the following formula (i), and the fitting curve when the surface reflectance Rf is 40% is expressed by the following formula (j). In addition, when calculating the fitting curve of formula (i), the two points of data shown in the figure where the refractive index n ranges from approximately 2.4 to approximately 2.6 are not used. In addition, when calculating the fitting curve of formula (j), the one point of data shown in the figure where the refractive index n ranges from approximately 2.4 to approximately 2.6 is not used.

[0076] n=0.7929×k 2 -2.1606×k+2.1448···Formula (h)

[0077] n=1.7917×k 3 -9.1446×k 2 +16.519×k-9.5626···Formula (i)

[0078] n=15.539×k 4 -103.99×k 3 +260.83×k 2 -289.22×k+120.12···Formula (j)

[0079] like Figure 2 As shown in , the fitting curve when the back reflectivity Rb is 50% is expressed by the following formula (k), the fitting curve when the back reflectivity Rb is 45% is expressed by the following formula (l), and the fitting curve when the back reflectivity Rb is 40% is expressed by the following formula (m).

[0080] n=0.6198×k 2-2.1796×k+2.6451···Formula (k)

[0081] n=0.2357×k 2 -0.2976×k+0.5410···Formula (1)

[0082] n=0.3457×k 2 -0.5539×k+0.8005···Formula (m)

[0083] The following formula (1) represents the conditions required for the phase difference φ of the light-shielding film (OD = 3.0) for ArF exposure light to be 90 degrees or less. The following formula (2) represents the conditions required for the film thickness of the light-shielding film (OD = 3.0) to be 80 nm or less. The following formula (3) represents the conditions required for the surface reflectance of the light-shielding film (OD = 3.0) for ArF exposure light to be 50% or less.

[0084] n≦0.0733×k 2 +0.4069×k+1.0083···Formula (1)

[0085] n≧29.316×k 2 -92.292×k+72.671···Formula (2)

[0086] n≧0.7929×k 2 -2.1606×k+2.1448···Formula (3)

[0087] When the relationship of formula (1) and formula (2) is satisfied at the same time, the film thickness of the light-shielding film with an OD of 3.0 can be set to 80 nm or less, and the phase difference φ of the light-shielding film can be set to 90 degrees or less, thereby reducing the EMF deviation of the light-shielding film pattern and reducing the burden when manufacturing a transfer mask using a mask blank having the light-shielding film. Furthermore, when the relationship of formula (3) is satisfied, the surface reflectivity of the light-shielding film with an OD of 3.0 can be set to 50% or less, thereby easily suppressing the degradation of the projected optical image during transfer exposure. In addition, as Figure 2 As shown, when the surface reflectivity is 50% or less, the back reflectivity is also 50% or less. Therefore, when the relationship of formula (3) is satisfied, the degradation of the projected optical image during transfer exposure caused by the back reflection of the shading film can be easily suppressed.

[0088] The following formula (4) represents the conditions required for the phase difference φ of the light-shielding film (OD = 3.0) for ArF exposure light to be 80 degrees or less. The following formula (5) represents the conditions required for the phase difference φ of the light-shielding film (OD = 3.0) for ArF exposure light to be -20 degrees or more. The following formula (6) represents the conditions required for the phase difference φ of the light-shielding film (OD = 3.0) for ArF exposure light to be 0 degrees or more.

[0089] n≦0.0966×k 2 +0.3660×k+0.9956···Formula (4)

[0090] n≧0.0637×k 2 -0.1096×k+0.9585···Formula (5)

[0091] n≧0.0636×k 2 -0.0147×k+0.9613···Formula (6)

[0092] When the relationship of formula (4) is satisfied, the phase difference φ of the light-shielding film with an OD of 3.0 can be set to 80 degrees or less, thereby further reducing the EMF deviation of the light-shielding film pattern and further reducing the burden when manufacturing a transfer mask using a mask blank having the light-shielding film.

[0093] When the relationship of formula (5) is satisfied, the phase difference φ of the light-shielding film with an OD of 3.0 can be made larger than -20 degrees. When the relationship of formula (6) is satisfied, the phase difference φ of the light-shielding film with an OD of 3.0 can be made larger than 0 degrees.

[0094] The following formula (7) represents the conditions required for making the thickness of the light-shielding film (OD=3.0) 70 nm or less. The following formula (8) represents the conditions required for making the thickness of the light-shielding film (OD=3.0) 60 nm or less.

[0095] n≧23.107×k 2 -82.037×k+73.115···Formula (7)

[0096] n≧12.717×k 2 -54.382×k+58.228···Formula (8)

[0097] When the relationship of formula (7) is satisfied, the thickness of the shading film with an OD of 3.0 can be set to less than 70 nm, thereby further reducing the EMF deviation of the shading film pattern. In addition, when the relationship of formula (8) is satisfied, the thickness of the shading film with an OD of 3.0 can be set to less than 60 nm, thereby further reducing the EMF deviation of the shading film pattern.

[0098] The following formula (9) represents the conditions required to make the surface reflectivity of the light-shielding film for ArF exposure light (OD=3.0) less than 45%, and the following formula (10) represents the conditions required to make the surface reflectivity of the light-shielding film for ArF exposure light (OD=3.0) less than 40%.

[0099] n≧1.7917×k 3 -9.1446×k 2 +16.519×k-9.5626···Formula (9)

[0100] n≧15.539×k 4 -103.99×k 3 +260.83×k 2 -289.22×k+120.12···Formula (10)

[0101] When the relationship of formula (9) is satisfied, the surface reflectivity of the light-shielding film with an OD of 3.0 can be set to 45% or less, so that the degradation of the projected optical image during transfer exposure can be more easily suppressed. In addition, when the relationship of formula (10) is satisfied, the surface reflectivity of the light-shielding film with an OD of 3.0 can be set to 40% or less, so that the degradation of the projected optical image during transfer exposure can be further easily suppressed. In addition, as Figure 2 As shown, when the surface reflectivity is less than 45%, the back reflectivity is also less than 45%. Therefore, when the relationship of formula (9) is satisfied, it is easier to suppress the degradation of the projected optical image during transfer exposure caused by back reflection. In addition, when the surface reflectivity is less than 40%, the back reflectivity is also less than 40%. Therefore, when the relationship of formula (10) is satisfied, it is easier to further suppress the degradation of the projected optical image during transfer exposure caused by back reflection.

[0102] Next, each embodiment of the present invention will be described.

[0103] Figure 3 1 is a cross-sectional view showing the structure of a mask blank 100 according to an embodiment of the present invention.

[0104] Figure 3 The mask blank 100 shown has a structure in which a light-shielding film 2 and a hard mask 3 are sequentially stacked on a light-transmitting substrate 1 .

[0105] [[Light-transmitting substrate]]

[0106] The translucent substrate 1 is composed of a material containing silicon and oxygen, and can be formed using glass materials such as synthetic quartz glass, quartz glass, aluminosilicate glass, soda-lime glass, and low thermal expansion glass (e.g., SiO2-TiO2 glass). Among these materials, synthetic quartz glass has a high transmittance for ArF exposure light and is particularly preferred as a material for the translucent substrate forming the mask blank.

[0107] [[Light-shielding film]]

[0108] The light-shielding film 2 is a single-layer film formed from a silicon nitride-based material. The silicon nitride-based material of the present invention is composed of silicon and nitrogen, or of one or more elements selected from semimetallic elements and nonmetallic elements, silicon, and nitrogen. Furthermore, by forming a single-layer film, the number of manufacturing steps is reduced, production efficiency is improved, and manufacturing quality control, including defects, is facilitated. Furthermore, since the light-shielding film 2 is formed from a silicon nitride-based material, it exhibits high ArF light resistance.

[0109] The light shielding film 2 may contain any semimetallic element in addition to silicon. Among the semimetallic elements, it is preferred to contain one or more elements selected from boron, germanium, antimony, and tellurium because this can improve the conductivity of silicon used as a sputtering target.

[0110] In addition, in addition to nitrogen, the light-shielding film 2 may also contain any non-metallic elements. The non-metallic elements of the present invention refer to non-metallic elements in a narrow sense (nitrogen, carbon, oxygen, phosphorus, sulfur, selenium, hydrogen), halogen elements (fluorine, chlorine, bromine, iodine, etc.) and rare gas elements. Among the non-metallic elements, it is preferred to contain one or more elements selected from carbon, fluorine and hydrogen. Except for the surface layer on the side of the transparent substrate 1 described later and the surface layer on the side opposite to the transparent substrate 1, the light-shielding film 2 preferably suppresses the oxygen content to below 5 atomic %, more preferably suppresses it to below 3 atomic %, and further preferably does not contain obvious oxygen (below the detection lower limit when performing composition analysis by X-ray photoelectron spectroscopy, etc.). When oxygen is contained in the silicon nitride-based material, the attenuation coefficient k decreases, and it is difficult to obtain sufficient light-shielding performance. In addition, the transparent substrate 1 is generally formed using a material with silicon oxide as the main component, such as synthetic quartz glass. When the light-shielding film 2 is disposed in contact with the surface of the transparent substrate 1, if the light-shielding film 2 contains oxygen, the difference in composition between the oxygen-containing silicon nitride-based material film and the transparent substrate becomes smaller. This makes it difficult to achieve etching selectivity between the light-shielding film 2 in contact with the transparent substrate 1 and the transparent substrate 1 during dry etching with a fluorine-based gas during patterning of the light-shielding film 2. Furthermore, if the light-shielding film 2 contains a high oxygen content, the repair rate during EB defect repair will be significantly slowed.

[0111] When the light-shielding film 2 is formed by reactive sputtering, rare gas is an element that can increase the film forming speed and improve production efficiency due to its presence in the film forming chamber. The rare gas is plasmatized and collides with the target material, whereby the target constituent elements fly out of the target material, capture the reactive gas on the way and form the light-shielding film 2 on the translucent substrate 1. During the period from when the target constituent elements fly out of the target material and adhere to the translucent substrate 1, a very small amount of rare gas in the film forming chamber is introduced. As gases preferably used as rare gases required for the reactive sputtering, argon, krypton and xenon can be mentioned. In addition, in order to relax the stress of the light-shielding film 2, helium and neon with small atomic weight can also be actively introduced into the light-shielding film 2.

[0112] The light-shielding film 2 is preferably formed from a material composed of silicon and nitrogen. As described above, a very small amount of rare gas is introduced when the light-shielding film 2 is formed by reactive sputtering. However, rare gases are difficult to detect even when performing compositional analysis on thin films, such as Rutherford Back-Scattering Spectrometry (RBS) or X-ray Photoelectron Spectroscopy (XPS). Therefore, the material composed of silicon and nitrogen described above can be considered to also include a material containing a rare gas.

[0113] In the light-shielding film 2, preferably, the deviation of the nitrogen content in the thickness direction of the region other than the surface layer on the side of the transparent substrate 1 and the surface layer on the side opposite to the transparent substrate 1 (hereinafter referred to as the volume region) is within 5 atomic %, more preferably within 3 atomic %. If the deviation is within 5 atomic %, it can be considered that the composition is uniform. On the other hand, when the light-shielding film 2 is subjected to the above-mentioned RBS or XPS composition analysis, since the analysis result of the surface layer on the side of the transparent substrate 1 is affected by the transparent substrate 1, it is difficult to have the same composition as the volume region. In addition, the surface layer on the side opposite to the transparent substrate 1 will undergo natural oxidation, so it is difficult to have the same composition as the volume region. In addition, if oxygen is actively added to the surface layer on the side opposite to the transparent substrate 1, it is possible to suppress changes in the characteristics of the light-shielding film 2, such as changes in the surface reflectivity to the ArF exposure light caused by mask cleaning or storage in the atmosphere. As a method for actively causing the surface layer on the side opposite to the light-transmitting substrate 1 to contain oxygen, the following methods can be cited: after forming the light-shielding film 2 by sputtering, additional post-treatment such as heat treatment in an oxygen-containing gas such as the atmosphere, light irradiation treatment using a flash lamp or the like in an oxygen-containing gas such as the atmosphere, or treatment in which ozone or oxygen plasma is brought into contact with the surface of the light-shielding film. Furthermore, the surface layer of the light-shielding film 2 on the side opposite to the light-transmitting substrate 1 refers to the region from the interface between the light-shielding film 2 and the light-transmitting substrate 1 to a depth of 5 nm on the surface layer side facing the opposite side. Furthermore, the surface layer of the light-shielding film 2 on the side opposite to the light-transmitting substrate 1 refers to the region from the surface of the light-shielding film 2 on the side opposite to the light-transmitting substrate 1 to a depth of 5 nm on the side facing the light-transmitting substrate 1.

[0114] The nitrogen content of the light-shielding film 2 is preferably 50 atomic % or less, more preferably 45 atomic % or less. If the nitrogen content exceeds 50 atomic %, the attenuation coefficient k for ArF exposure light decreases, making it difficult to achieve sufficient light-shielding performance. Furthermore, the nitrogen content of the light-shielding film 2 is preferably 25 atomic % or more, more preferably 30 atomic % or more. If the nitrogen content is less than 25 atomic %, the cleaning resistance is likely to be insufficient, oxidation is likely to occur, and the film's stability over time is likely to be impaired. Furthermore, spontaneous etching is likely to occur when performing EB defect correction on the light-shielding film 2.

[0115] The silicon content of the light-shielding film 2 is preferably 50 atomic % or greater, more preferably 55 atomic % or greater. If the silicon content is less than 50 atomic %, the attenuation coefficient k for ArF exposure light decreases, making it difficult to achieve sufficient light-shielding performance. Furthermore, the silicon content of the light-shielding film 2 is preferably 75 atomic % or less, more preferably 70 atomic % or less. If the silicon content exceeds 75 atomic %, the cleaning resistance is likely to be insufficient, oxidation is likely to occur, and the film's stability over time is likely to be impaired.

[0116] The thickness of the light-shielding film 2 is 80 nm or less, preferably 70 nm or less, and more preferably 60 nm or less. A thickness of 80 nm or less facilitates the formation of a fine light-shielding film pattern, reduces EMF variation in the light-shielding film pattern, and reduces the burden of manufacturing a transfer mask using a mask blank having the light-shielding film. Furthermore, the thickness of the light-shielding film 2 is preferably 40 nm or greater, more preferably 45 nm or greater. A thickness of less than 40 nm makes it difficult to achieve sufficient light-shielding performance against ArF exposure light.

[0117] The optical density of the light-shielding film 2 for ArF exposure light is preferably 3.0 or greater. When the optical density is 3.0 or greater, sufficient light-shielding performance is achieved. Therefore, when a transfer mask manufactured using this mask blank is used for exposure, sufficient contrast in the projected optical image (transferred image) is easily achieved. Furthermore, the optical density of the light-shielding film 2 for ArF exposure light is preferably 4.0 or less, and more preferably 3.5 or less. When the optical density exceeds 4.0, the thickness of the light-shielding film 2 becomes too thick, making it difficult to form a fine light-shielding film pattern.

[0118] The surface reflectivity of the light-shielding film 2 with respect to ArF exposure light (the reflectivity of the surface opposite to the light-transmitting substrate 1) is preferably 50% or less, more preferably 45% or less, and even more preferably 40% or less. If the surface reflectivity exceeds 50%, the ArF exposure light is excessively reflected, and the projected optical image during transfer exposure is likely to degrade. Furthermore, the surface reflectivity of the light-shielding film 2 with respect to ArF exposure light is preferably 20% or greater. If the surface reflectivity is less than 20%, the pattern inspection sensitivity during mask pattern inspection using light with a wavelength of 193 nm or near that is reduced.

[0119] The back reflectivity of the light-shielding film 2 (the reflectivity of the surface facing the light-transmitting substrate 1) with respect to ArF exposure light is preferably 50% or less, more preferably 45% or less, and even more preferably 40% or less. If the back reflectivity exceeds 50%, the exposure light is excessively reflected, and the projected optical image during transfer exposure is likely to deteriorate.

[0120] The phase difference of the light-shielding film 2 with respect to the ArF exposure light is 90 degrees or less, preferably 80 degrees or less. A phase difference of 90 degrees or less reduces EMF variation in the pattern of the light-shielding film 2, and also reduces the burden when manufacturing a transfer mask using a mask blank having this light-shielding film. Furthermore, the phase difference of the light-shielding film 2 with respect to the ArF exposure light is preferably -20 degrees or greater, and more preferably 0 degrees or greater.

[0121] The refractive index n and attenuation coefficient k of the light-shielding film 2 with respect to ArF exposure light satisfy the relationship defined by the following equations (1) and (2). When the relationship in equation (1) is satisfied, the phase difference of the light-shielding film 2 with respect to the ArF exposure light can be reduced to 90 degrees or less, and when the relationship in equation (2) is satisfied, the thickness of the light-shielding film can be reduced to 80 nm or less. Therefore, when the relationship in equations (1) and (2) is satisfied, the EMF variation of the pattern of the light-shielding film 2 is reduced, and the burden of manufacturing a transfer mask using a mask blank having this light-shielding film is also reduced. Furthermore, the refractive index n and attenuation coefficient k with respect to ArF exposure light preferably satisfy the relationship defined by the following equation (3). When the relationship in equation (3) is satisfied, the surface reflectance of the light-shielding film 2 can be reduced to 50% or less, and as described above, the back surface reflectance of the light-shielding film 2 can also be reduced to 50% or less. Therefore, when the relationship in equation (3) is satisfied, degradation of the projected optical image during transfer exposure can be easily suppressed.

[0122] n≦0.0733×k 2 +0.4069×k+1.0083···Formula (1)

[0123] n≧29.316×k 2 -92.292×k+72.671···Formula (2)

[0124] n≧0.7929×k 2 -2.1606×k+2.1448···Formula (3)

[0125] The refractive index n and attenuation coefficient k of the light-shielding film 2 with respect to the ArF exposure light preferably satisfy the relationship of the following formula (4). When the relationship of formula (4) is satisfied, the phase difference of the light-shielding film 2 with respect to the ArF exposure light can be made less than 80 degrees, further reducing the EMF deviation of the pattern of the light-shielding film 2 and further reducing the burden when manufacturing a transfer mask using a mask blank having the light-shielding film. In addition, the refractive index n and attenuation coefficient k with respect to the ArF exposure light preferably satisfy the relationship of the following formula (5), and more preferably satisfy the relationship of the following formula (6). When the relationship of formula (5) is satisfied, the phase difference of the light-shielding film 2 with respect to the ArF exposure light can be made greater than -20 degrees, and when the relationship of formula (6) is satisfied, the phase difference of the light-shielding film 2 with respect to the ArF exposure light can be made greater than 0 degrees.

[0126] n≦0.0966×k 2 +0.3660×k+0.9956···Formula (4)

[0127] n≧0.0637×k 2 -0.1096×k+0.9585···Formula (5)

[0128] n≧0.0636×k 2 -0.0147×k+0.9613···Formula (6)

[0129] The refractive index n and attenuation coefficient k of the light-shielding film 2 with respect to ArF exposure light preferably satisfy the relationship of the following equation (7), and more preferably satisfy the relationship of the following equation (8). When the relationship of equation (7) is satisfied, the thickness of the light-shielding film can be reduced to 70 nm or less, further reducing the EMF variation of the pattern of the light-shielding film 2, and further reducing the burden when manufacturing a transfer mask using a mask blank having such a light-shielding film. Furthermore, when the relationship of equation (8) is satisfied, the thickness of the light-shielding film can be reduced to 60 nm or less, further reducing the EMF variation of the pattern of the light-shielding film 2, and further reducing the burden when manufacturing a transfer mask using a mask blank having such a light-shielding film.

[0130] n≧23.107×k 2 -82.037×k+73.115···Formula (7)

[0131] n≧12.717×k 2 -54.382×k+58.228···Formula (8)

[0132] The refractive index n and attenuation coefficient k of the light-shielding film 2 with respect to ArF exposure light preferably satisfy the relationship of the following equation (9), and more preferably satisfy the relationship of the following equation (10). When the relationship of equation (9) is satisfied, the surface reflectivity of the light-shielding film 2 can be reduced to 45% or less. Furthermore, as described above, the back surface reflectivity of the light-shielding film 2 can also be reduced to 45% or less, making it easier to suppress degradation of the projected optical image during transfer exposure. Furthermore, when the relationship of equation (10) is satisfied, the surface reflectivity of the light-shielding film 2 can be reduced to 40% or less. Furthermore, as described above, the back surface reflectivity of the light-shielding film 2 can also be reduced to 40% or less, making it easier to suppress degradation of the projected optical image during transfer exposure.

[0133] n≧1.7917×k 3 -9.1446×k 2 +16.519×k-9.5626···Formula (9)

[0134] n≧15.539×k 4 -103.99×k 3 +260.83×k 2 -289.22×k+120.12···Formula (10)

[0135] The refractive index n of the light-shielding film 2 for ArF exposure light is preferably 0.8 or greater, more preferably 0.9 or greater, and even more preferably 1.0 or greater. To reduce the refractive index n to less than 0.8, the nitrogen content of the light-shielding film 2 must be significantly reduced. Therefore, if the refractive index is less than 0.8, spontaneous etching is more likely to occur during EB defect repair.

[0136] The attenuation coefficient k of the light-shielding film 2 for ArF exposure light is preferably 2.6 or less, more preferably 2.5 or less, and even more preferably 2.4 or less. To achieve an attenuation coefficient k exceeding 2.6, the nitrogen content of the light-shielding film 2 must be significantly reduced. Therefore, if the attenuation coefficient k exceeds 2.6, spontaneous etching is more likely to occur during EB defect repair.

[0137] Furthermore, the surface layer of the light-shielding film 2 opposite the translucent substrate 1 undergoes oxidation. Consequently, the composition of this surface layer of the light-shielding film 2 differs from that of the remaining regions of the light-shielding film 2, leading to different optical properties. However, in this specification, the light-shielding film 2 is considered a single layer with uniform optical properties throughout the film thickness. Therefore, the refractive index n and attenuation coefficient k of the light-shielding film 2 refer to the refractive index n and attenuation coefficient k of the entire film, including the surface layer.

[0138] The refractive index n and attenuation coefficient k of a thin film are not determined solely by the composition of the thin film. The film density and crystallization state of the thin film are also factors that control the refractive index n and attenuation coefficient k. Therefore, the various conditions when forming the light-shielding film 2 by reactive sputtering are adjusted to form the film so that the light-shielding film 2 has the desired refractive index n and attenuation coefficient k, so that the optical concentration, surface reflectivity, back reflectivity and phase difference for ArF exposure light converge to the specified values. In order to set the light-shielding film 2 to the above-mentioned range of refractive index n and attenuation coefficient k, when forming the film by reactive sputtering, it is not limited to adjusting only the ratio of the mixed gas of the rare gas and the reactive gas. It also involves many aspects such as the pressure in the film-forming chamber during film-forming by reactive sputtering, the power applied to the target material, the distance between the target material and the translucent substrate, and other positional relationships. In addition, these film-forming conditions are inherent in the film-forming device, and these conditions are appropriately adjusted so that the formed light-shielding film 2 has the desired refractive index n and attenuation coefficient k.

[0139] The light-shielding film 2 is formed by sputtering. Any sputtering method, such as DC sputtering, RF sputtering, and ion beam sputtering, can be used. When using a target material with low conductivity (such as a silicon target material or a silicon compound target material containing no or a small amount of semi-metallic elements), RF sputtering or ion beam sputtering is preferably used. However, considering the film formation rate, RF sputtering is more preferred.

[0140] The light shielding film 2 is formed by reactive sputtering in a sputtering gas containing nitrogen gas and rare gas using a silicon target or a target made of a material containing one or more elements selected from semimetallic elements and nonmetallic elements in silicon.

[0141] The nitrogen-based gas used as the sputtering gas when forming the light-shielding film 2 can be any gas as long as it contains nitrogen. As described above, it is preferable to keep the oxygen content of the light-shielding film 2 (except for its surface layer) low. Therefore, it is preferable to use a nitrogen-based gas that does not contain oxygen, and nitrogen (N2 gas) is more preferable. The type of noble gas used as the sputtering gas when forming the light-shielding film 2 is not limited, but argon, krypton, or xenon are preferably used. Furthermore, to alleviate stress in the light-shielding film 2, helium or neon, which have low atomic weights, can be actively introduced into the light-shielding film 2.

[0142] [[Hard Mask]]

[0143] In a mask blank 100 having a light-shielding film 2, a hard mask 3 formed from a material having etching selectivity for the etching gas used to etch the light-shielding film 2 is preferably further laminated on the light-shielding film 2. Due to the need to maintain a specified optical density, there is a limit to how thin the thickness of the light-shielding film 2 can be. The hard mask 3 is sufficient as long as it has a thickness sufficient to function as an etching mask until the dry etching process, which forms a pattern on the light-shielding film 2 immediately below the hard mask 3, is completed, and is essentially unrestricted by optical properties. Therefore, the thickness of the hard mask 3 can be significantly thinner than that of the light-shielding film 2. Furthermore, the organic material resist film is sufficient as long as it has a thickness sufficient to function as an etching mask until the dry etching process, which forms a pattern on the hard mask 3, is completed. Therefore, the thickness of the resist film can be significantly thinner than before. This can thus prevent problems such as the resist pattern from tipping over.

[0144] The hard mask 3 is preferably formed of a material containing chromium (Cr). Materials containing chromium have particularly high resistance to dry etching using fluorine-based gases such as SF6. Thin films made of chromium-containing materials are typically patterned by dry etching using a mixture of chlorine-based gases and oxygen. However, the anisotropy of this dry etching is not very high, so when dry etching is used to pattern thin films made of chromium-containing materials, etching toward the sidewalls of the pattern (side etching) is likely to occur.

[0145] When a material containing chromium is used for the light-shielding film, the thickness of the light-shielding film 2 is relatively thick. Therefore, although the problem of side etching will occur during the dry etching of the light-shielding film 2, when a material containing chromium is used as the hard mask 3, the thickness of the hard mask 3 is relatively thin. Therefore, the problem caused by side etching is less likely to occur.

[0146] Examples of materials containing chromium include, in addition to chromium metal, materials containing chromium and one or more elements selected from oxygen, nitrogen, carbon, boron, and fluorine, such as CrN, CrC, CrON, CrCO, and CrCON. Adding these elements to chromium metal facilitates forming an amorphous film, which is preferable because it can suppress the surface roughness of the film and the line edge roughness during dry etching of the light-shielding film 2.

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

[0148] Chromium-based materials are etched by a mixture of chlorine-based gases and oxygen, but the etching rate of chromium metal with this etching gas is not very high. By adding one or more elements selected from oxygen, nitrogen, carbon, boron, and fluorine to the chromium, the etching rate of the chlorine-based gas and oxygen mixture can be increased.

[0149] Furthermore, hard mask 3 composed of CrCO is particularly preferred because it does not contain nitrogen, which increases side etching during dry etching using a mixture of chlorine-based gas and oxygen, contains carbon, which suppresses side etching, and contains oxygen, which increases the etching rate. Furthermore, the chromium-containing material forming hard mask 3 may contain one or more elements selected from indium, molybdenum, and tin. The inclusion of one or more elements selected from indium, molybdenum, and tin further increases the etching rate of the mixture of chlorine-based gas and oxygen.

[0150] As materials other than chromium-containing materials for forming the hard mask 3, materials containing metals such as tantalum, in addition to metals such as tantalum (Ta) and tungsten (W), can also be used. For example, materials containing tantalum in this case include, in addition to tantalum metal, materials containing tantalum and one or more elements selected from nitrogen, boron, and carbon. Specific examples include Ta, TaN, TaO, TaON, TaBN, TaBO, TaBON, TaCN, TaCO, TaCON, TaBCN, and TaBOCN.

[0151] In mask blank 100, a resist film made of an organic material is preferably formed with a thickness of 100 nm or less, in contact with the surface of hard mask 3. For fine patterns corresponding to the 32nm generation of DRAM, a 40nm line width SRAF (Sub-Resolution Assist Feature) may be provided in the transferred pattern to be formed on hard mask 3. However, in this case, the cross-sectional aspect ratio of the resist pattern can be reduced to 1:2.5, thereby preventing the resist pattern from falling or peeling during development and cleaning of the resist film. Furthermore, the resist film is more preferably 80 nm or less in thickness.

[0152] Alternatively, the mask blank 100 may be formed without the hard mask 3 and instead directly in contact with the light-shielding film 2. This simplifies the structure and eliminates the need for dry etching of the hard mask 3 when manufacturing the transfer mask, thus reducing the number of manufacturing steps. Furthermore, in this case, it is preferable to form the resist film after surface treatment of the light-shielding film 2 with HMDS (hexamethyldisilazane) or the like.

[0153] As described below, the mask blank of the present invention is suitable for binary masks, but is not limited to binary masks and can also be used as a mask blank for Levenson phase shift masks or CPL (Chromeless Phase Lithography) masks.

[0154] [Transfer mask]

[0155] Figure 4 Schematic cross-sectional view showing a process of manufacturing a transfer mask (binary mask) 200 using the mask blank 100 according to the embodiment of the present invention.

[0156] Figure 4 The manufacturing method of the transfer mask 200 shown uses the above-mentioned mask blank 100, and is characterized in that it includes: a process of forming a transfer pattern on the hard mask 3 by dry etching; a process of forming a transfer pattern on the shading film 2 by dry etching using the hard mask 3 (hard mask pattern 3a) having the transfer pattern as a mask; and a process of removing the hard mask pattern 3a.

[0157] The following, according to Figure 4 The manufacturing process shown in FIG. 1 illustrates an example of a method for manufacturing the transfer mask 200. In this example, the light shielding film 2 is made of a material containing silicon and nitrogen, and the hard mask 3 is made of a material containing chromium.

[0158] First, prepare the mask blank 100 (see Figure 4 (a)), a resist film is formed by spin coating in contact with the hard mask 3. Next, the transfer pattern to be formed on the light shielding film 2 is exposed to the resist film, and further subjected to a predetermined treatment such as a development treatment to form a resist pattern 4a (see Figure 4 (b)).

[0159] Next, using the resist pattern 4a as a mask, dry etching is performed using a chlorine-based gas such as a mixed gas of chlorine and oxygen to form a pattern (hard mask pattern 3a) on the hard mask 3 (see FIG. Figure 4(c)). The chlorine-based gas is not particularly limited as long as it contains Cl, and examples thereof include Cl2, SiCl2, CHCl3, CH2Cl2, and BCl3. When a mixed gas of chlorine and oxygen is used, for example, the gas flow ratio may be set to Cl2:O2 = 4:1.

[0160] Next, the resist pattern 4a is removed by ashing or resist stripping solution (see Figure 4 (d)).

[0161] Next, dry etching is performed using a fluorine-based gas using the hard mask pattern 3a as a mask to form a pattern (light-shielding film pattern 2a) on the light-shielding film 2 (see FIG. Figure 4 (e)) As a fluorine-containing gas, any gas containing fluorine can be used, but SF6 is preferred. Examples of other fluorine-containing gases include CHF3, CF4, C2F6, and C4F8. However, fluorine-containing gases containing carbon have a higher etching rate for the transparent substrate 1, which is a glass material. SF6 is preferred because it minimizes damage to the transparent substrate 1. Furthermore, He or the like may be added to SF6.

[0162] Then, the hard mask pattern 3a is removed using a chromium etching solution, and a transfer mask 200 is obtained after a predetermined treatment such as cleaning (see FIG. Figure 4 (f) Here, the hard mask pattern 3a can be removed by dry etching using a mixed gas of chlorine and oxygen. Here, as the chromium etching solution, a mixture containing ammonium cerium nitrate and perchloric acid can be mentioned.

[0163] pass Figure 4 The transfer mask 200 manufactured by the manufacturing method shown is a binary mask having a light-shielding film 2 (light-shielding film pattern 2a) having a transfer pattern on a light-transmitting substrate 1. The light-shielding film 2 is a single-layer film formed of a material containing silicon and nitrogen. It is characterized by having an optical density of 3.0 or greater for ArF exposure light, and having a refractive index n and an attenuation coefficient k for ArF exposure light that simultaneously satisfy the relationships defined in the following equations (1) and (2).

[0164] n≦0.0733×k 2 +0.4069×k+1.0083···Formula (1)

[0165] n≧29.316×k 2 -92.292×k+72.671···Formula (2)

[0166] Matters related to the light-transmitting substrate 1 and the light-shielding film 2 in the transfer mask 200 have the same technical features as those related to the light-transmitting substrate 1 and the light-shielding film 2 in the mask blank 100 .

[0167] The optical density of the light-shielding film pattern 2a of the transfer mask 200 is 3.0 or greater. The refractive index n and attenuation coefficient k of the light-shielding film pattern 2a for ArF exposure light satisfy the relationships defined in equations (1) and (2). Therefore, the light-shielding film pattern 2a exhibits high light-shielding performance against ArF exposure light. Furthermore, the EMF variation of the light-shielding film pattern 2a can be reduced, allowing the transfer mask 200 to be manufactured without imposing a significant burden.

[0168] While the transfer mask 200 is described herein as a binary mask, the transfer mask of the present invention is not limited to binary masks and can also be applied to Levenson-type phase-shift masks and CPL masks. Specifically, in the case of a Levenson-type phase-shift mask, the light-shielding film of the present invention can be used as the light-shielding film. Furthermore, in the case of a CPL mask, the light-shielding film of the present invention can be used primarily in the area including the peripheral light-shielding band.

[0169] Furthermore, the method for manufacturing a semiconductor device of the present invention is characterized in that a transfer pattern is exposed to a resist film on a semiconductor substrate using the transfer mask 200 described above or using the transfer mask 200 manufactured using the mask blank 100 described above.

[0170] The transfer mask 200 and mask blank 100 of the present invention exhibit the aforementioned effects. Therefore, when the transfer mask 200 is placed on a mask stage of an exposure apparatus using ArF excimer laser light and a transfer pattern is transferred by exposure to a resist film on a semiconductor device, the transfer pattern can be transferred to the resist film on the semiconductor device with high CD accuracy. Consequently, when a circuit pattern is formed by dry etching an underlying film using the resist film pattern as a mask, a high-precision circuit pattern can be formed without wiring shorts or disconnections due to insufficient accuracy.

[0171] Example

[0172] Hereinafter, embodiments of the present invention will be described in more detail with reference to examples.

[0173] (Example 1)

[0174] [Mask Blank Manufacturing]

[0175] A translucent substrate 1 made of synthetic quartz glass having a main surface size of approximately 152 mm x 152 mm and a thickness of approximately 6.25 mm was prepared. The end faces and main surface of the translucent substrate 1 were polished to a predetermined surface roughness, and then subjected to predetermined cleaning and drying processes.

[0176] Next, a translucent substrate 1 is set in a single-chip RF sputtering device, a silicon (Si) target is used, a mixed gas of krypton (Kr), helium (He) and nitrogen (N2) is used as the sputtering gas, the power of the RF power supply is set to a specified value, and a light-shielding film 2 composed of silicon and nitrogen is formed on the translucent substrate 1 with a thickness of 58.8 nm by reactive sputtering (RF sputtering).

[0177] Next, for the purpose of adjusting the stress of the film, the light-transmitting substrate 1 on which the light-shielding film 2 was formed was subjected to a heat treatment in the atmosphere at a heating temperature of 500° C. for a treatment time of 1 hour.

[0178] The optical density (OD) of the heat-treated light-shielding film 2 was measured at a wavelength of 193 nm using a spectrophotometer (Cary 4000, manufactured by Agilent Technologies, Inc.) to be 3.00. This result shows that the mask blank of Example 1 has high light-shielding performance.

[0179] The phase difference of the light-shielding film 2 after the heat treatment was measured at a wavelength of 193 nm using a phase shift measuring device (MPM-193 manufactured by Lasertec Corporation) and found to be 75.2 degrees.

[0180] The surface reflectance and back reflectance of the light-shielding film 2 after heat treatment were measured at a wavelength of 193 nm using a spectrophotometer (Hitachi, U-4100). The results were 37.1% and 30.0%, respectively. These results demonstrate that the transfer mask manufactured using the mask blank of Example 1 can suppress degradation of the projected optical image during transfer exposure.

[0181] The refractive index n and attenuation coefficient k of the heat-treated light-shielding film 2 were measured at a wavelength of 193 nm using a spectroscopic ellipsometer (M-2000D manufactured by JA Woollam Co., Ltd.). The refractive index n and attenuation coefficient k at a wavelength of 193 nm were 1.83 and 1.79, respectively. These values ​​of the refractive index n and attenuation coefficient k indicate that the refractive index n and attenuation coefficient k of the light-shielding film 2 satisfy the conditions of equations (4), (6), (8), and (10) described above, and match the respective values ​​of the film thickness, optical density, phase difference, surface reflectivity, and back reflectivity described above. Furthermore, since the refractive index n and attenuation coefficient k of the light-shielding film 2 satisfy the conditions of equations (4), (8), and (10), they also satisfy the conditions of equations (1), (2), and (3).

[0182] Next, an optical simulation was performed to calculate the EMF deviation of the light-shielding film 2 of Example 1. In this optical simulation, the refractive index n, attenuation coefficient k, and film thickness d of the light-shielding film 2 obtained in the above-mentioned measurement were used as input values. In addition, a line-space pattern with a DRAM half pitch (hp) of 40nm was used as the design pattern for the optical simulation. Dipole illumination was set as the illumination condition for the exposure light suitable for the optical simulation. The EMF deviation was calculated by taking the difference between the deviation (correction amount) calculated in the optical simulation using TMA and the deviation (correction amount) calculated in the simulation taking into account the EMF effect. As a result, the EMF deviation was 0.5nm. From this result, it can be said that the EMF deviation of the mask blank of Example 1 is sufficiently reduced. In addition, it can be considered that the burden of correction calculation of the design pattern when manufacturing a transfer mask using the mask blank of Example 1 is reduced, and the complexity of the pattern actually formed on the light-shielding film 2 can also be suppressed.

[0183] Next, the translucent substrate 1, with the heat-treated light-shielding film 2 formed thereon, was placed in a single-wafer DC sputtering apparatus. Reactive sputtering (DC sputtering) was performed using a chromium (Cr) target in a mixed gas atmosphere of argon (Ar) and nitrogen (N2), forming a hard mask 3 composed of a 5nm-thick CrN film. The film composition ratio of this film, as measured by XPS, was 75 atomic% Cr and 25 atomic% N. Subsequently, a heat treatment was performed at a lower temperature (280°C) than that performed during the heat treatment of the light-shielding film 2 to adjust the stress of the hard mask 3.

[0184] Through the above-described procedures, the mask blank 100 having a structure in which the light-shielding film 2 and the hard mask 3 are stacked on the light-transmitting substrate 1 is manufactured.

[0185] [Manufacturing of transfer mask]

[0186] Next, using the mask blank 100 of Example 1, the transfer mask (binary mask) 200 of Example 1 was manufactured by the following procedure.

[0187] First, prepare the mask blank 100 of Example 1 (see Figure 4 (a)), a resist film made of a chemically amplified resist for electron beam drawing is formed with a thickness of 80 nm so as to be in contact with the surface of the hard mask 3. Next, a transfer pattern to be formed on the light shielding film 2 is drawn on the resist film by electron beam drawing, and a predetermined development process and a cleaning process are performed to form a resist pattern 4a (see Figure 4 (b)).

[0188] Next, using the resist pattern 4a as a mask, dry etching is performed using a mixed gas of chlorine and oxygen (gas flow ratio Cl2:O2=4:1) to form a pattern (hard mask pattern 3a) on the hard mask 3 (see Figure 4 (c)).

[0189] Next, the resist pattern 4a is removed (see Figure 4 (d)). Next, using the hard mask pattern 3a as a mask, dry etching is performed using a fluorine-based gas (a mixture of SF6 and He) to form a pattern (light-shielding film pattern 2a) on the light-shielding film 2 (see Figure 4 (e)).

[0190] Then, the hard mask pattern 3a is removed using a chromium etching solution containing ammonium cerium nitrate and perchloric acid, and a transfer mask 200 is obtained after a predetermined treatment such as cleaning (see FIG. Figure 4 (f)).

[0191] The transfer mask 200 of Example 1 was placed on a mask stage of an exposure apparatus, and the resist film on the semiconductor device was exposed and transferred. As a result, the transfer pattern could be transferred to the resist film on the semiconductor device with high CD accuracy.

[0192] (Example 2)

[0193] [Mask Blank Manufacturing]

[0194] The mask blank of Example 2 was manufactured by the same procedure as the mask blank 100 of Example 1, except that the light-shielding film was as described below.

[0195] The method for forming the light-shielding film of Example 2 is as follows.

[0196] A translucent substrate 1 is set in a monolithic DC sputtering device, a silicon (Si) target is used, a mixed gas of krypton (Kr), helium (He) and nitrogen (N2) is used as the sputtering gas, the power of the DC power supply is set to a specified value, and a light-shielding film 2 composed of silicon and nitrogen is formed on the translucent substrate 1 with a thickness of 45.7 nm by reactive sputtering (DC sputtering).

[0197] Next, for the purpose of adjusting the stress of the film, the light-transmitting substrate 1 on which the light-shielding film 2 was formed was subjected to a heat treatment in the atmosphere at a heating temperature of 500° C. for a treatment time of 1 hour.

[0198] The optical density (OD) of the heat-treated light-shielding film 2 was measured as in Example 1 and found to be 3.06. This result demonstrates that the mask blank of Example 2 exhibits high light-shielding performance. Furthermore, the retardation of the heat-treated light-shielding film 2 was measured as in Example 1, but this value could not be determined. Therefore, an optical simulation was performed to calculate the retardation based on the refractive index n and attenuation coefficient k of the heat-treated light-shielding film 2, resulting in a value of -11.7 degrees. Furthermore, the surface reflectivity and back reflectivity of the heat-treated light-shielding film 2 were measured as in Example 1 and found to be 54.3% and 52.1%, respectively. Furthermore, the refractive index n and attenuation coefficient k of the heat-treated light-shielding film 2 were measured as in Example 1 and found to be 1.16 and 2.40, respectively. From the values ​​of the refractive index n and the attenuation coefficient k, it can be seen that the refractive index n and the attenuation coefficient k of the light-shielding film 2 after the heat treatment satisfy the conditions of equations (4), (5), and (8), and match the values ​​of the film thickness, optical density, phase difference, surface reflectivity, and back reflectivity described above. Furthermore, since the refractive index n and the attenuation coefficient k of the light-shielding film 2 satisfy the conditions of equations (4) and (8), they also satisfy the conditions of equations (1) and (2).

[0199] As in Example 1, the EMF deviation of the light-shielding film 2 was found to be 3.6 nm. This result indicates that the mask blank of Example 2 can sufficiently reduce EMF deviation. Furthermore, it is believed that the burden of correcting the design pattern when manufacturing a transfer mask using the mask blank of Example 2 is reduced, and the complexity of the pattern actually formed on the light-shielding film 2 can be suppressed.

[0200] [Manufacturing of transfer mask]

[0201] Next, using the mask blank of Example 2, a transfer mask (binary mask) of Example 2 was manufactured by the same procedure as in Example 1. The transfer mask 200 of Example 2 was placed on a mask stage of an exposure apparatus, and the resist film on the semiconductor device was exposed and transferred. As a result, the transfer pattern could be transferred to the resist film on the semiconductor device with high CD accuracy.

[0202] (Comparative Example 1)

[0203] [Mask Blank Manufacturing]

[0204] The mask blank of Comparative Example 1 was produced by the same procedure as that of the mask blank 100 of Example 1, except that the light-shielding film was as described below.

[0205] The method for forming the light-shielding film of Comparative Example 1 is as follows.

[0206] A translucent substrate 1 is set in a monolithic RF sputtering device, a silicon (Si) target is used, a mixed gas of krypton (Kr), helium (He) and nitrogen (N2) is used as the sputtering gas, the power of the RF power supply is set to a specified value, and a light-shielding film composed of silicon and nitrogen is formed on the translucent substrate 1 with a thickness of 69.5 nm by reactive sputtering (RF sputtering).

[0207] Next, for the purpose of adjusting the stress of the film, the light-transmitting substrate 1 on which the light-shielding film was formed was subjected to a heat treatment in the atmosphere at a heating temperature of 500° C. for a treatment time of 1 hour.

[0208] The optical density (OD) of the heat-treated light-shielding film was measured as in Example 1 and found to be 3.01. This result indicates that the mask blank of Comparative Example 1 possesses sufficient light-shielding performance. Furthermore, the phase difference of the heat-treated light-shielding film was measured as in Example 1, but this value could not be determined. Therefore, a simulation was performed to determine the phase difference based on the refractive index n and attenuation coefficient k of the heat-treated light-shielding film, and the value was 129.9 degrees. Furthermore, the surface reflectivity and back reflectivity of the heat-treated light-shielding film were measured as in Example 1 and found to be 29.4% and 19.6%, respectively. Furthermore, the refractive index n and attenuation coefficient k of the heat-treated light-shielding film 2 were measured as in Example 1 and found to be 2.10 and 1.51, respectively. From the values ​​of the refractive index n and the attenuation coefficient k, it can be seen that the refractive index n and the attenuation coefficient k of the light-shielding film after the heat treatment satisfy the conditions of equations (7) and (10), but do not satisfy the conditions of equation (1), and match the values ​​of the film thickness, optical density, phase difference, surface reflectivity, and back surface reflectivity described above. Furthermore, since the refractive index n and the attenuation coefficient k of the light-shielding film satisfy equations (7) and (10), they also satisfy equations (2) and (3) described above, but do not satisfy equation (1).

[0209] As in Example 1, the EMF deviation of the light-shielding film was calculated to be 8.2 nm. This result indicates that the mask blank of Comparative Example 1 does not sufficiently reduce EMF deviation. Furthermore, it is believed that the design pattern correction calculation burden when manufacturing a transfer mask using the mask blank of Comparative Example 1 is excessive, and the pattern actually formed on the light-shielding film 2 is also complex.

[0210] [Manufacturing of transfer mask]

[0211] Next, using the mask blank of Comparative Example 1, a transfer mask (binary mask) of Comparative Example 1 was manufactured by the same procedure as in Example 1. The transfer mask of Comparative Example 1 was placed on a mask stage of an exposure apparatus, and exposure transfer was performed on a resist film on a semiconductor device. As a result, the CD unevenness of the transferred pattern of the resist film formed on the semiconductor device was large.

[0212] Explanation of symbols

[0213] 1Transparent substrate

[0214] 2 shading film

[0215] 2a Light-shielding film pattern

[0216] 3Hard mask

[0217] 3a Hard mask pattern

[0218] 4a Resist pattern

[0219] 100 mask blanks

[0220] 200 transfer mask (binary mask)

Claims

1. A mask blank comprising a light-shielding film on a light-transmitting substrate, characterized in that: The light shielding film is a single-layer film formed of a material composed of silicon and nitrogen, or a single-layer film formed of a material composed of one or more elements selected from semi-metallic elements and non-metallic elements, silicon and nitrogen. The optical density of the light-shielding film with respect to exposure light of the ArF excimer laser is 3.0 or more. The attenuation coefficient k of the light-shielding film is less than 2.6, The refractive index n of the light-shielding film is greater than 0.8, The refractive index n and attenuation coefficient k of the light-shielding film for the exposure light simultaneously satisfy the relationships defined by the following equations (1), (2), and (3): n≦0.0733×k 2 +0.4069×k+1.0083···Formula (1), n≧0.0637×k 2 -0.1096×k+0.9585···Formula (2), n≧0.7929×k 2 -2.1606×k+2.1448···Formula (3).

2. The mask blank according to claim 1, wherein The deviation of the nitrogen content in the thickness direction of the light-shielding film in a region excluding the surface layer on the light-transmitting substrate side and the surface layer on the side opposite to the light-transmitting substrate is within 5 atomic %.

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

4. A transfer mask comprising a light-shielding film having a transfer pattern on a light-transmitting substrate, characterized in that: The light shielding film is a single-layer film formed of a material composed of silicon and nitrogen, or a single-layer film formed of a material composed of one or more elements selected from semi-metallic elements and non-metallic elements, silicon and nitrogen. The optical density of the light-shielding film with respect to exposure light of the ArF excimer laser is 3.0 or more. The attenuation coefficient k of the light-shielding film is less than 2.6, The refractive index n of the light-shielding film is greater than 0.8, The refractive index n and attenuation coefficient k of the light-shielding film for the exposure light simultaneously satisfy the relationships defined by the following equations (1), (2), and (3): n≦0.0733×k 2 +0.4069×k+1.0083···Formula (1), n≧0.0637×k 2 -0.1096×k+0.9585···Formula (2), n≧0.7929×k 2 -2.1606×k+2.1448···Formula (3).

5. The transfer mask according to claim 4, wherein The deviation of the nitrogen content in the thickness direction of the light-shielding film in a region excluding the surface layer on the light-transmitting substrate side and the surface layer on the side opposite to the light-transmitting substrate is within 5 atomic %.

6. A method for manufacturing a semiconductor device, characterized in that: The method comprises the step of transferring a transfer pattern by exposing the resist film on the semiconductor substrate using the transfer mask according to claim 4 or 5 .

Images