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

Abstract

An object of the present invention is to provide a mask blank in which the boundary between a region where a thin film is formed and a region where no thin film is formed can be easily visually recognized, making it easy to adjust the position of a mask substrate provided on a sputtering apparatus for forming a thin film. A mask blank includes a substrate and a thin film, and is characterized in that the substrate has two main surfaces and side surfaces, a chamfered surface is provided between the two main surfaces and the side surfaces, one of the two main surfaces has: an inner region including the center of the main surface and an outer peripheral region outside the inner region, the thin film is provided on the inner region of the main surface, the surface reflectance Rs of the outer peripheral region with respect to light having a wavelength of 400 nm to 700 nm is 10% or less, and when the surface reflectance of a part in a portion where the film thickness of the thin film is in the range of 9 nm to 10 nm with respect to light having a wavelength of 400 nm to 700 nm is set as Rf, the contrast (Rf / Rs) is 3.0 or more.

Description

Technical Field

[0001] 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

[0002] Generally, in the manufacturing process of semiconductor devices, photolithography is used to form fine patterns. In addition, several substrates called transfer masks are usually used in the formation of such fine patterns. When miniaturizing the patterns of semiconductor devices, in addition to miniaturizing the mask patterns formed on the transfer masks, it is also necessary to shorten the wavelength of the exposure light source used in photolithography. As an exposure light source in semiconductor device manufacturing, in recent years, the wavelength has been shortened from a KrF excimer laser (wavelength 248 nm) to an ArF excimer laser (wavelength 193 nm).

[0003] In recent years, as one of such transfer masks, a phase shift mask called a halftone phase shift mask has been developed. This halftone type phase shift mask is composed of a portion that transmits light having an intensity substantially contributing to exposure (light transmitting portion) and a portion that transmits light having an intensity substantially not contributing to exposure (semi-light transmitting portion) to form a mask pattern formed on a transparent substrate. Further, by causing the phase shift of the light passing through the semi-light transmitting portion such that the phase of the light passing through the semi-light transmitting portion is substantially inverted with respect to the phase of the light passing through the light transmitting portion, the light passing through the vicinity of the boundary portion between the light transmitting portion and the semi-light transmitting portion cancels each other out, and the contrast of the boundary portion can be maintained well.

[0004] However, since the wavelength of the laser used for exposure becomes shorter, the energy of the laser becomes larger, and thus the damage to the semi-light transmitting film by exposure becomes larger. To improve the durability of the semi-light transmitting film against the laser, it is effective to densify the film of the semi-light transmitting film. However, on the other hand, if the sheet resistance of the semi-light transmitting film becomes large, when patterning the resist film formed thereon by electron beam lithography, charges accumulate on the semi-light transmitting film and are charged, causing a problem that correct pattern drawing cannot be performed.

[0005] On the other hand, Patent Document 1 discloses the following technique: An exposed portion 5 where no phase shift film 2 is formed is formed at the peripheral portion on the transparent substrate 1, and a light shielding film is formed so as to cover the exposed portion 5 and the phase shift film 2. The light shielding film is made of a conductive material having a conductivity such that it does not charge when the resist film 4 is patterned by electron beam lithography.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Patent Laid-Open No. 2006-184353

[0009] Problems to be Solved by the Invention

[0010] In the above-mentioned mask blank, the light-shielding film is formed in a wide area covering the chamfered surface or the side surface of the substrate. On the other hand, with the miniaturization of patterns, the film thickness of the light-shielding film, which is also used as a hard mask, continues to be further thinned to 40 nm or less. Generally, the thin film including the light-shielding film of the mask blank is formed on the substrate by a sputtering method. When forming a thin film by the sputtering method, the incident angle of the sputtering particles with respect to the chamfered surface or the side surface of the substrate is an acute angle compared to the incident angle of the sputtering particles with respect to the main surface of the substrate. Therefore, compared with the thickness of the thin film formed on the main surface, the thickness of the thin film formed on the chamfered surface or the side surface is significantly thinner. In addition, the adhesion of the thin film formed on the chamfered surface or the side surface is weaker than the adhesion of the thin film formed on the main surface. Due to these circumstances, there is a problem that the light-shielding film formed on the chamfered surface or the side surface of the substrate is likely to peel off, and dust is likely to be generated due to the peeling of the light-shielding film in this part during the operation of the mask blank. To solve this problem, when forming the light-shielding film by sputtering, an attempt has been made to control the outer edge of the film formation region (thin film formation region) of the light-shielding film to be more inward than the ridge line of the chamfered surface of the main surface of the substrate and more outward than the position where the ground wire pin contacts when the electron beam lithography apparatus is set up.

[0011] In the past, when controlling the region of the thin film formed on the main surface of the substrate, sputtering was performed in a state where a mask plate for masking the region where the thin film was not desired to be formed on the substrate was provided. That is, sputtering was performed in a state where only the region where the thin film was desired to be formed on the main surface of the substrate (hereinafter, sometimes referred to as the "design region") was exposed. If sputtering is performed in a state where the mask plate is in contact with the main surface of the substrate, it is possible to prevent the thin film from spreading and forming on the chamfered surface or the side surface of the substrate. However, in this case, due to the contact between the mask plate and the main surface of the substrate, there will be problems such as damage or foreign matter on the substrate due to rubbing or friction. Therefore, the mask plate is arranged in a non-contact state with the main surface of the substrate and sputtering is performed. During this sputtering, most of the sputtering particles are incident on the main surface of the substrate in a direction inclined to a certain extent from the direction perpendicular to the main surface of the substrate. In addition, there are also sputtering particles in a floating state in the sputtering apparatus. Therefore, it is difficult to avoid a certain amount of sputtering particles from spreading and accumulating in the gap between the main surface of the substrate and the mask plate. That is, after sputtering, a state is formed in which the desired thickness is formed in the design region on the main surface of the substrate, but a thin film with a thin thickness is also formed slightly outside the boundary of the design region.

[0012] Particularly, in the case of forming a thin film with high conductivity such as a light-shielding film, it is required that the thin film be formed to the outside of the position where the ground pin of an electron beam lithography apparatus or the like contacts. The position where the ground pin contacts is mostly close to the ridge line of the chamfered surface on the main surface of the substrate. When it is necessary to form such a thin film in a region close to the ridge line of the chamfered surface on the main surface, if the position accuracy during the setting of the mask is low, sputtered particles may adhere to the chamfered surface or the side surface to form a thin film. That is, in order to control the thin film formation region, it is necessary to improve the position accuracy of the mask of the sputtering apparatus.

[0013] As a method for confirming the position accuracy of the mask, actually, the mask is set on the substrate, and a light-shielding film is formed by sputtering, and the region where the light-shielding film is formed is visually recognized by magnifying with an optical camera. As a result, it is sometimes difficult to confirm the boundary between the region where the light-shielding film is formed and the region where the light-shielding film is not formed, which becomes a problem. In addition, such a problem is not limited to the light-shielding film, and it also occurs in masks for other uses having thin films on the substrate. Summary of the Invention

[0014] The present invention is completed to solve the conventional problems, and its object is to easily visually recognize the boundary between the region where a thin film is formed and the region where the thin film is not formed (the region where the substrate is exposed) when a thin film is formed on a substrate. In addition, its object is to provide a mask blank that can easily adjust the position of the mask set on the sputtering apparatus for forming a thin film to prevent the thin film from spreading and forming on the side surface or the chamfered surface of the substrate. Furthermore, its object is to provide a transfer mask manufactured using this mask blank. Moreover, the object of the present invention is to provide a method for manufacturing a semiconductor device using such a transfer mask.

[0015] In order to achieve the above object, the present invention has the following structure.

[0016] (Structure 1)

[0017] A mask blank includes a substrate and a thin film, and is characterized in that

[0018] the substrate has two main surfaces and side surfaces, and a chamfered surface is provided between the two main surfaces and the side surfaces,

[0019] one of the two main surfaces has: an inner region including the center of the main surface, and an outer peripheral region outside the inner region,

[0020] the thin film is provided on the inner region of the main surface,

[0021] the outer peripheral region of the main surface has a surface reflectance Rs of 10% or less for light with a wavelength of 400 nm to 700 nm,

[0022] When the surface reflectance of a part within the range of 9 nm to 10 nm in film thickness of the thin film with respect to light having a wavelength of 400 nm to 700 nm is Rf, the contrast ratio (Rf / Rs) is 3.0 or more.

[0023] (Structure 2)

[0024] The mask blank according to Structure 1, wherein the surface reflectance of the part with respect to light having a wavelength of 400 nm to 700 nm is 20% or more.

[0025] (Structure 3)

[0026] The mask blank according to Structure 1 or 2, wherein when the surface reflectance of the part with respect to light having a wavelength of 400 nm is RfB, the surface reflectance of the part with respect to light having a wavelength of 550 nm is RfG, and the surface reflectance of the part with respect to light having a wavelength of 700 nm is RfR, the standard deviation calculated among the three surface reflectances RfB, RfG, and RfR is 1.0 or less.

[0027] (Structure 4)

[0028] The mask blank according to any one of Structures 1 to 3, wherein the extinction coefficient k of the thin film with respect to light having a wavelength of 400 nm to 700 nm is 1.5 or more.

[0029] (Structure 5)

[0030] The mask blank according to any one of Structures 1 to 4, wherein the average film thickness of the thin film is greater than 10 nm and 60 nm or less.

[0031] (Structure 6)

[0032] The mask blank according to any one of Structures 1 to 5, wherein an intermediate film is provided between the main surface and the thin film in a region inside from the outer edge of the inner region toward the center side of the one main surface.

[0033] (Structure 7)

[0034] The mask blank according to Structure 6, wherein the intermediate film is a semi-transparent film that transmits exposure light of an ArF excimer laser with a transmittance of 1% or more.

[0035] (Structure 8)

[0036] A transfer mask, which is formed by providing a transfer pattern on the thin film of the mask blank according to any one of Structures 1 to 5.

[0037] (Structure 9)

[0038] A transfer mask, characterized in that a transfer pattern is provided on the intermediate film in the mask blank described in Structure 6 or 7, and a pattern including a light-shielding band is provided on the thin film to form it.

[0039] (Structure 10)

[0040] A method for manufacturing a semiconductor device, characterized by comprising a step of exposing and transferring a transfer pattern onto a resist film on a semiconductor substrate using the transfer mask described in Structure 8 or 9.

[0041] Advantages of the Invention

[0042] According to the mask blank of the present invention, when a thin film is formed on a substrate, the boundary between the area where the thin film is formed and the area where the thin film is not formed (the area where the substrate is exposed) can be easily visually recognized. Thus, the position adjustment of the mask plate provided in the sputtering device for forming the thin film can be easily performed to prevent the thin film from spreading to the side surface or chamfer surface of the substrate. Description of the Drawings

[0043] Figure 1 It is a main part sectional view showing the structure of the mask blank of the embodiment of the present invention.

[0044] Figure 2 It is a plan schematic view of the substrate of the embodiment of the present invention.

[0045] Figure 3 It is a sectional schematic view showing the manufacturing process of the phase shift mask of the embodiment of the present invention.

[0046] Figure 4 It is a schematic view of the main part of the mask plate used when forming the thin film of the mask blank of the embodiment of the present invention.

[0047] Figure 5 It is a graph showing the film thickness distribution near the boundary between the main surface of Example 1 and the light-shielding film. Detailed Embodiments

[0048] Hereinafter, before describing the embodiments of the present invention, the background of the present invention will be described.

[0049] The inventors of the present invention have conducted in-depth research on the structure of a mask blank that can easily visually recognize the boundary between the area where a thin film is formed and the area where the thin film is not formed (the area where the substrate is exposed) when a thin film is formed on a substrate. Thus, the position adjustment of the mask plate provided in the sputtering device for forming the thin film can be easily performed to prevent the thin film from spreading to the side surface or chamfer surface of the substrate.

[0050] In view of the above, even when forming a thin film by sputtering using a mask, it is difficult to avoid a certain amount of sputtering particles from spreading and accumulating in the gap between the main surface of the substrate and the mask. That is, a state is formed in which the desired thickness is formed in the design region on the main surface of the substrate, but a thin film is also formed slightly outside the boundary of the design region. The formed thin film is formed with a substantially uniform thickness in the region of the main surface not covered by the mask. However, due to the influence of sputtering particles entering the gap between the mask and the main surface of the substrate, the end of the thin film does not have a shape with a vertical side wall. That is, the end of the thin film is located at a position only a certain distance outside the design region of the main surface, and the thin film formed outside the design region has a shape in which the thickness gradually thins from the position of the boundary of the design region toward its end.

[0051] The distance from the boundary of the design region on the main surface to the end of the thin film is difficult to avoid differences even between two sputtering apparatuses with the same design specifications. Even when using the same sputtering apparatus, differences will occur due to sputtering conditions. Therefore, in practice, on a substrate provided with a mask, a thin film is formed under the designed film-forming conditions, the position of the end of the thin film is confirmed, and the position of the mask is adjusted. The inventors considered that the frequency of adjusting the position of the mask was high, and tried to adopt a method of using image data taken by a camera such as a CCD in the identification of the end of the thin film (hereinafter, this method may sometimes be referred to as the "image recognition method"). When using this image recognition method, it is difficult to correctly detect the boundary between the region where the thin film is formed and the region where the thin film is not formed (the region where the main surface is exposed) on the main surface. In this image recognition method, a portion where a certain level or more of contrast is obtained between the light reflected from the region where the thin film is not formed and the light reflected from the region where the thin film is formed is recognized as the presence of the thin film. The position of the outermost end of the region where the thin film is recognized to exist by this image recognition method is slightly inside the position of the outermost end of the region where the thin film actually exists.

[0052] As a result of the inventors' intensive research, it was found that depending on the structure of the thin film, the difference between the position of the outermost end of the region where the thin film is recognized to exist by this image recognition method and the position of the outermost end of the region where the thin film actually exists becomes large, and the accuracy of the position adjustment of the mask decreases. Then, the inventors studied the thickness trend of the thin film from the design region of the thin film formed by sputtering on the main surface of the substrate to the end of the thin film, and then studied the relationship between the thickness of the thin film and the reflectance of visible light (specifically, light with a wavelength of 400 nm to 700 nm. Hereinafter, light in this wavelength band may sometimes be referred to as "light in the visible light region"), and further conducted in-depth research.

[0053] First, according to the trend of the thickness of the thin film, if the presence of the thin film can be recognized at the position where the maximum thickness of the thin film is 10 nm by the above-described image acquisition method, the difference from the outermost position of the region where the thin film actually exists is small, and the position adjustment of the mask blank can be performed with high accuracy. In order to easily recognize the presence of the thin film at this part of the thin film, it is desirable that the surface reflectance of the light in the visible light region of the outer peripheral region of the main surface of the substrate where the thin film is not formed is low. It is sufficient that the surface reflectance is determined to be 10% or less. On this basis, in order to be able to recognize the presence of the thin film at this part of the thin film, it is desirable that the contrast between the surface reflectance of the light in the visible light region of this part of the thin film and the surface reflectance of the light in the visible light region of the part where the main surface of the substrate is exposed is 3.0 or more. Further, in order to easily recognize the presence of the thin film, even if the thickness of the thin film is thinned from 10 nm to 1 nm, it is desirable that the above contrast is maintained at 3.0 or more.

[0054] That is, the mask blank of the present invention is a mask blank including a substrate and a thin film, characterized in that the substrate has two main surfaces and side surfaces, a chamfered surface is provided between the two main surfaces and the side surfaces, one of the two main surfaces has: an inner region including the center of the main surface, and an outer peripheral region outside the inner region, the thin film is provided on the inner region of the main surface, the surface reflectance Rs of the outer peripheral region of the main surface with respect to light having a wavelength of 400 nm to 700 nm is 10% or less, and when the surface reflectance of a part in the range of 9 nm to 10 nm of the film thickness of the thin film with respect to light having a wavelength of 400 nm to 700 nm is set as Rf, the contrast (Rf / Rs) is 3.0 or more.

[0055] Figure 1 It is a cross-sectional view showing the structure of the mask blank 100 according to an embodiment of the present invention. Figure 1 The mask blank 100 of the present invention shown has a structure in which a phase shift film 20, a light-shielding film 30, and a hard mask film 31 are sequentially stacked on a light-transmissive substrate 10.

[0056] The light-transmissive substrate 10 can be formed of quartz glass, aluminosilicate glass, soda-lime glass, low-thermal-expansion glass (such as SiO2-TiO2 glass), etc., in addition to synthetic quartz glass. Among them, synthetic quartz glass has a high transmittance for ArF exposure light and also has sufficient rigidity that is difficult to cause deformation, so it is particularly preferably used as the material of the light-transmissive substrate for forming the mask blank. The substrate 10 housed in a chamber (not shown) has: two main surfaces 11 (11a, 11b), side surfaces 12, and a chamfered surface 13 formed by chamfering the boundary portion between the main surface 11 and the side surfaces 12. When viewed from the main surface 11 side, the boundary between the main surface 11 and the chamfered surface 13 is preferably less than 0.5 mm from the side surface 12 of the substrate, and more preferably 0.4 mm or less.

[0057] As shown in Figure 2 FIG. 1, one of the two main surfaces 11, i.e., the main surface 11a, has an inner region 14 including the center 17 of the main surface 11a and an outer peripheral region 15 outside the inner region 14. A light-shielding film 30 in the form of a thin film is provided on the inner region 14. The light-shielding film 30 is substantially not formed on the peripheral region 15, that is, the main surface 11a is substantially exposed. The state where the light-shielding film 30 is substantially not formed or the state where the main surface 11a is substantially exposed also includes a state where sputtering particles constituting the light-shielding film 30 slightly adhere and accumulate to a thickness less than 1 nm. If it is such a degree of accumulation state, it is difficult to be a main cause of defects, and there is no substantial difference from the surface reflectance Rs in the state where the main surface 11a is completely exposed. In addition,[ Figure 2 the boundary line between the inner region 14 and the peripheral region 15 and the center 17 shown in FIG. 2 are imaginary lines added for explanation and do not have to be actual lines added in the actual substrate. This is noted for the sake of caution.

[0058] The boundary line between the inner region 14 and the peripheral region 15 is preferably located inside by 0.05 mm or more from the boundary between the chamfered surface 13 of the substrate 10 and the main surface 11a.

[0059] In addition, the surface reflectance Rs of the peripheral region 15 in the substrate 10 for light with a wavelength of 400 nm to 700 nm is preferably 10% or less, more preferably 8% or less, and still more preferably 7% or less. Both the surface reflectance Rs and the surface reflectance Rf described later can be measured based on image data captured by a camera such as a CCD. By setting the surface reflectance Rs of the peripheral region 15 within the above range, it is easy to adjust the contrast between the surface reflectance Rf of the thin film in the range of 9 nm to 10 nm in film thickness for light with a wavelength of 400 nm to 700 nm to 3.0 or more.

[0060] In the present embodiment, as shown in Figure 1 FIG. 3, in the region on the inner side from the boundary between the inner region 14 and the peripheral region 15 toward the center 17 side of the main surface 11a, a phase shift film 20 as an intermediate film is provided between the main surface 11a and the light-shielding film 30 in the form of a thin film.

[0061] The phase shift film 20 is made of a material containing silicon.

[0062] The phase shift film 20 is preferably a semi-transmissive film having a function of transmitting the exposure light of an ArF excimer laser with a transmittance of 1% or more (transmittance), and a function of generating a phase difference of 150 degrees or more and 210 degrees or less between the exposure light transmitted through the phase shift film 20 and the exposure light in the air that has passed through the same distance as the thickness of the phase shift film 20. In addition, the transmittance of the phase shift film 20 is preferably 1% or more, more preferably 2% or more. The transmittance of the phase shift film 20 is preferably 30% or less, more preferably 20% or less.

[0063] The thickness of the phase shift film 20 is preferably 80 nm or less, more preferably 70 nm or less. The thickness of the phase shift film 20 is preferably 50 nm or more. This is because in order to form the phase shift film 20 from an amorphous material and make the phase difference of the phase shift film 20 150 degrees or more, 50 nm or more is required.

[0064] In the phase shift film 20, in order to satisfy the various conditions related to the optical properties and the film thickness, the refractive index n of the phase shift film with respect to the exposure light (ArF exposure light) is preferably 1.9 or more, more preferably 2.0 or more. In addition, the refractive index n of the phase shift film 20 is preferably 3.1 or less, more preferably 2.7 or less. The extinction coefficient k of the phase shift film 20 with respect to the ArF exposure light is preferably 0.26 or more, more preferably 0.29 or more. In addition, the extinction coefficient k of the phase shift film 20 is preferably 0.62 or less, more preferably 0.54 or less.

[0065] In addition, the refractive index n and the extinction coefficient k of the thin film including the phase shift film 20 are not only determined by the composition of the thin film. The film density and the crystal state of the thin film are also factors that influence the refractive index n and the extinction coefficient k. Therefore, adjust the various conditions when forming the thin film by reactive sputtering so that the thin film is formed into a desired refractive index n and extinction coefficient k. In order to make the phase shift film 20 within the above refractive index n and extinction coefficient k ranges, when forming by reactive sputtering, it is effective to adjust the ratio of the mixed gas of an inert gas and a reactive gas (oxygen, nitrogen, etc.), but it is not limited thereto. There are various positional relationships such as the pressure in the film formation chamber, the electric power applied to the sputtering target, and the distance between the target and the light-transmissive substrate 10 when forming by reactive sputtering. In addition, these film formation conditions are inherent conditions of the film formation apparatus and can be appropriately adjusted so that the formed phase shift film 20 becomes a desired refractive index n and extinction coefficient k.

[0066] The mask blank 100 has a light-shielding film 30 as a thin film on the phase shift film 20. Generally, in a binary transfer mask, the outer peripheral region of the region where the transfer pattern is formed (transfer pattern formation region) is required to ensure an optical density (OD) of a specified value or more so that when the resist film on the semiconductor wafer is exposed and transferred using an exposure apparatus, the resist film is not affected by the exposure light passing through the outer peripheral region. This also applies to the case of a phase shift mask. Generally, in the outer peripheral region of a transfer mask including a phase shift mask, the OD is preferably 3.0 or more, and at least greater than 2.0. The phase shift film 20 has a function of transmitting the exposure light at a specified transmittance, and it is difficult to ensure the optical density of the specified value only with the phase shift film 20. Therefore, at the stage of manufacturing the mask blank 100, in order to ensure the lacking optical density, it is necessary to stack the light-shielding film 30 on the phase shift film 20. By forming the structure of the mask blank 100 like this, in the process of manufacturing the phase shift mask 200 (refer to Figure 3 ), if the light-shielding film 30 in the region where the phase shift effect is used (basically the transfer pattern formation region) is removed, a phase shift mask 200 that ensures the optical density of the specified value in the outer peripheral region can be manufactured.

[0067] In addition, the light-shielding film 30 needs to function as an etching mask when dry etching is performed using a fluorine-based gas for forming a transfer pattern (phase shift pattern) on the phase shift film 20. Therefore, in the dry etching using a fluorine-based gas, the light-shielding film 30 needs to use a material having sufficient etching selectivity with respect to the phase shift film 20. For the light-shielding film 30, it is required to be able to form a fine pattern that should be formed on the phase shift film 20 with high precision. The average film thickness of the light-shielding film 30 is preferably 60 nm or less, more preferably 50 nm or less, and further preferably 40 nm or less. If the film thickness of the light-shielding film 30 is too thick, the fine pattern that should be formed cannot be formed with high precision. On the other hand, the light-shielding film 30 is required to satisfy the optical density required as described above. Therefore, the average film thickness of the light-shielding film 30 is required to be greater than 10 nm, preferably 15 nm or more, except for the end region that is the boundary between the inner region 14 and the outer peripheral region 15. Here, the average film thickness is not particularly limited, and can be calculated by dividing the region where the light-shielding film 30 is formed into regions of about 55 μm × about 55 μm and taking the average of the film thicknesses measured in each region.

[0068] In the present embodiment, the light-shielding film 30 as a thin film is configured such that when the surface reflectance of a portion within the range of 9 nm to 10 nm in the film thickness of the light-shielding film 30 with respect to light having a wavelength of 400 nm to 700 nm is set as Rf, the contrast ratio (Rf / Rs) is 3.0 or more. Thus, it is easy to identify the boundary between the region where the light-shielding film 30 as a thin film is formed and the region where the light-shielding film 30 is not formed. Further, from the viewpoint of visual recognition, the surface reflectance Rf of the above-mentioned one portion with respect to light having a wavelength of 400 nm to 700 nm is preferably 20% or more.

[0069] As described above, the portion of the light-shielding film 30 (thin film) for which the above-mentioned surface reflectance Rf is determined is not strictly the outermost end of the light-shielding film 30. However, the difference between the position of this portion of the light-shielding film 30 and the outermost end position is small, and based on this, the position adjustment of the mask can be sufficiently performed.

[0070] From the viewpoint of ensuring conductivity, the sheet resistance value of the light-shielding film 30 is preferably 1 kΩ / Square or less, and more preferably 0.5 kΩ / Square or less.

[0071] When the surface reflectance of a portion within the range of 9 nm to 10 nm in the film thickness of the light-shielding film 30 with respect to light having a wavelength of 400 nm is set as RfB, the surface reflectance of the above-mentioned one portion with respect to light having a wavelength of 550 nm is set as RfG, and the surface reflectance of the above-mentioned one portion with respect to light having a wavelength of 700 nm is set as RfR, the standard deviation calculated among the three surface reflectances RfB, RfG, and RfR is preferably 1.0 or less. It can be relatively easily obtained from the RGB values of the image data captured by a camera such as a CCD. For the one with a small deviation in the reflectance of light of the above three wavelengths, the presence of the light-shielding film 30 is more easily visually recognized.

[0072] From the viewpoint of visual recognition, the extinction coefficient k of the light-shielding film 30 with respect to light having a wavelength of 400 nm to 700 nm is preferably 1.5 or more, and more preferably 2.0 or more. Further, the extinction coefficient k of the light-shielding film 30 with respect to the above-mentioned light is preferably 4.0 or less, and more preferably 3.5 or less.

[0073] The light-shielding film 30 can be applied to either a single-layer structure or a stacked structure of two or more layers. Further, each layer of the single-layer light-shielding film and the stacked light-shielding film of two or more layers may be a structure having substantially the same composition in the thickness direction of the film or layer, or may be a structure having a compositional gradient in the thickness direction of the layer.

[0074] As long as the light-shielding film 30 satisfies the above contrast conditions, it can be formed of any material. The light-shielding film 30 is preferably formed of a chromium-containing material. As the chromium-containing material for forming the light-shielding film 30, in addition to chromium metal, materials containing one or more elements selected from oxygen (O), nitrogen (N), carbon (C), boron (B), and fluorine (F) in chromium (Cr) can be cited. Generally, chromium-based materials can be etched by a mixed gas of chlorine-based gas and oxygen, but the etching rate of chromium metal for this etching gas is not very high. Considering increasing the etching rate of the mixed gas of chlorine-based gas and oxygen for the etching gas, as the material for forming the light-shielding film 30, a material in which chromium contains one or more elements selected from oxygen, nitrogen, carbon, boron, and fluorine is preferred. In addition, one or more elements of molybdenum, indium, and tin can be contained in the chromium-containing material for forming the light-shielding film 30. By containing one or more elements of molybdenum, indium, and tin, the etching rate for the mixed gas of chlorine-based gas and oxygen can be made faster.

[0075] The light-shielding film 30 can be formed on the phase-shifting film 20 by reactive sputtering using a chromium-containing target. As the sputtering method, it can be a sputtering method using a direct current (DC) power supply (DC sputtering), or a sputtering method using a high-frequency (RF) power supply (RF sputtering). In addition, it can be a magnetron sputtering method or a conventional method. From the viewpoint of simple mechanism, DC sputtering is preferred. In addition, from the viewpoint of increasing the film formation rate and improving productivity, it is preferred to use the magnetron sputtering method. In addition, the film formation apparatus can be an in-line type or a single-wafer type.

[0076] As the sputtering gas used when forming the light-shielding film 30, a mixed gas containing a gas containing carbon but not oxygen (CH4, C2H4, C2H6, etc.), a gas containing oxygen but not carbon (O2, O3, etc.), and an inert gas (Ar, Kr, Xe, He, Ne, etc.) can be cited; a mixed gas containing a gas containing carbon and oxygen (CO2, CO, etc.) and an inert gas; or any one of a mixed gas containing at least one of a gas containing carbon but not oxygen (CH4, C2H4, C2H6, etc.) and a gas containing oxygen but not carbon in an inert gas and a gas containing carbon and oxygen. In particular, when using a mixed gas of CO2 and an inert gas as the sputtering gas, it is safe. Since the reactivity of CO2 gas is lower than that of oxygen, the gas can spread evenly over a large area in the chamber, and the film quality of the formed light-shielding film 30 becomes uniform. From this point of view, it is preferred. As the introduction method, they can be introduced into the chamber separately, or several gases can be concentrated or all the gases can be mixed and introduced.

[0077] The material of the target is not only pure chromium, as long as chromium is the main component, a target in which chromium is added with chromium containing either oxygen or carbon or chromium combining oxygen and carbon can be used.

[0078] In addition, the mask blank of the present invention is not limited to Figure 1 the structure shown. It may also be configured such that another film (etch stop film) is interposed between the phase shift film 20 and the light-shielding film 30. In this case, it is preferably configured such that the etch stop film is formed of the above-described chromium-containing material, and the light-shielding film 30 is formed of a silicon-containing material or a tantalum-containing material.

[0079] In addition, the mask blank of the present invention is not limited to the mask blank for a phase shift mask described above, and can also be applied to a mask blank for a binary mask. In this case, the mask blank has a structure in which the phase shift film 20 is not provided between the main surface 11a of the light-transmissive substrate 10 and the light-shielding film 30. In addition, the above-described specified optical density is ensured only by the light-shielding film 30. By forming a transfer pattern on the light-shielding film 30 of such a mask blank, a binary mask (transfer mask) can be formed.

[0080] In addition, the mask blank of the present invention may also be a reflective mask blank for EUV lithography (Extreme Ultraviolet Lithography). In this case, it is preferable that the absorber film is formed of the thin film of the present embodiment.

[0081] In the silicon-containing material for forming the light-shielding film 30, a transition metal may be contained, or a metal element other than a transition metal may be contained. The pattern formed on the light-shielding film 30 is basically a light-shielding band pattern in the outer peripheral region because the cumulative exposure dose of ArF exposure light is less than that in the transfer pattern region, and fine patterns are rarely arranged in this outer peripheral region, and even if the ArF light resistance is low, substantial problems are unlikely to occur. In addition, if a transition metal is contained in the light-shielding film 30, the light-shielding performance is significantly improved compared to the case where no transition metal is contained, and the thickness of the light-shielding film 30 can be made thinner. Examples of the transition metal contained in the light-shielding film 30 include any one of molybdenum (Mo), tantalum (Ta), tungsten (W), titanium (Ti), chromium (Cr), hafnium (Hf), nickel (Ni), vanadium (V), zirconium (Zr), ruthenium (Ru), rhodium (Rh), niobium (Nb), palladium (Pd), etc., or an alloy of these metals.

[0082] In the mask blank 100, it may also be configured such that a hard mask film 31 formed of a material having an etching selectivity with respect to the etching gas used for etching the light-shielding film 30 is further laminated on the light-shielding film 30. As Figure 1As shown, since the hard mask film 31 is formed in a region closer to the inside than the light-shielding film 30, there is no obstacle in ensuring the conductivity between the light-shielding film 30 and the resist film. The hard mask film 31 only needs to have a film thickness capable of functioning as an etching mask during the period until the dry etching for forming a pattern on the light-shielding film 30 directly below it is completed, and is basically not limited by the optical density. Therefore, the thickness of the hard mask film 31 can be significantly reduced compared to the thickness of the light-shielding film 30. Moreover, the resist film made of an organic material only needs to have a film thickness capable of functioning as an etching mask during the period until the dry etching for forming a pattern on this hard mask film is completed, so the thickness can be significantly reduced compared to the past. The thinning of the resist film is effective in improving the resist resolution and preventing pattern collapse, and is extremely important in meeting the requirements for miniaturization.

[0083] When the light-shielding film 30 is formed of a chromium-containing material, the hard mask film 31 is preferably formed of the above-mentioned silicon-containing material. In addition, in this case, the hard mask film 31 has a tendency of low adhesion to the resist film made of an organic material. Therefore, it is preferable to perform an HMDS (Hexamethyldisilazane) treatment on the surface of the hard mask film 31 to improve the surface adhesion. In addition, in this case, the hard mask film is more preferably formed of SiO2, SiN, SiON, etc.

[0084] In addition, as the material of the hard mask film 31 when the light-shielding film 30 is formed of a chromium-containing material, in addition to the above, a tantalum-containing material can also be applied. As the tantalum-containing material in this case, in addition to tantalum metal, materials containing one or more elements selected from nitrogen, oxygen, boron, carbon, and silicon in tantalum can also be listed. For example, Ta, TaN, TaO, TaON, TaBN, TaBO, TaBON, TaCN, TaCO, TaCON, TaBCN, TaBOCN, TaSi, TaSiN, TaSiO, TaSiON, TaSiBN, TaSiBO, TaSiBON, TaSiC, TaSiCN, TaSiCO, TaSiCON, etc. can be listed. In addition, when the light-shielding film 30 is formed of a silicon-containing material, the hard mask film 31 is preferably formed of the above-mentioned chromium-containing material.

[0085] In the mask blank 100, a resist film made of an organic material may be formed in contact with the surface of the light-shielding film 30 (the surface of the hard mask film 31 in the case where the hard mask film 31 is formed). In the case of a fine pattern corresponding to the DRAM hp 32 nm generation, an SRAF (Sub-Resolution Assist Feature) with a line width of 40 nm may sometimes be provided on the light-shielding pattern to be formed on the light-shielding film 30. However, even in such a case, by providing the hard mask film 31 as described above, the film thickness of the resist film can be suppressed, and thus, the aspect ratio of the cross section of the resist pattern formed of the resist film can be reduced to 1:2.5. Therefore, it is possible to suppress the collapse or detachment of the resist pattern during resist film development, rinsing, etc. In addition, the film thickness of the resist film is more preferably 80 nm or less. The resist film is preferably a resist for electron beam lithography exposure, and more preferably, the resist is a chemically amplified type.

[0086] The mask blank 100 having the above structure is manufactured in the following order. First, the light-transmissive substrate 10 is prepared. The side surface 12 and the main surface 11 of the light-transmissive substrate 10 are polished to a prescribed surface roughness (for example, the root mean square roughness Rq is 0.2 nm or less in the inner region of a quadrilateral with a side length of 1 μm), and then, a prescribed cleaning treatment and drying treatment are performed.

[0087] Next, the phase shift film 20 is formed on the light-transmissive substrate 10 by sputtering. After forming the phase shift film 20, an annealing treatment is performed at a prescribed heating temperature. Next, the above-described light-shielding film 30 is formed on the phase shift film 20 by sputtering.

[0088] Figure 4 This shows the main part of the mask plate used when forming the light-shielding film 30. As shown in this figure, both ends of the substrate 10 are positioned and held by the substrate holding portion 51. Moreover, a mask plate 52 covering the peripheral portion thereof is provided above the substrate 10. The mask plate 52 is provided in a state where it is held in a non-contact state with the substrate 10 and can be adjusted in position so as to approach or leave the center 17 of the main surface 11a of the substrate 10. By adjusting the position of the mask plate 52, it is possible to suppress the attachment of the light-shielding film material supplied from the sputtering target 50 to the peripheral portion of the substrate 10.

[0089] Then, the above-mentioned hard mask film 31 is formed on the light-shielding film 30 by sputtering. In the formation of each layer using the sputtering method, a sputtering target and a sputtering gas containing the materials constituting each layer in a prescribed composition ratio are used, and further, as needed, a mixed gas of the above-mentioned inert gas and reactive gas is used as the sputtering gas for formation. After that, when the mask blank 100 has a resist film, the surface of the hard mask film 31 is subjected to HMDS (Hexamethyldisilazane) treatment as needed. Then, a resist film is formed on the surface of the hard mask film 31 that has undergone HMDS treatment by a coating method such as spin coating, and the mask blank 100 is completed.

[0090] The phase shift mask 200 for transfer use according to this embodiment is characterized in that a transfer pattern (phase shift pattern) 20a is formed on the phase shift film 20 of the mask blank 100, and a light-shielding pattern 30b including light-shielding bands is formed on the light-shielding film 30. When a structure having a hard mask film is provided on the mask blank 100, the hard mask film 31 is removed during the production process of the phase shift mask 200.

[0091] The manufacturing method of the phase shift mask 200 of the present invention uses the above-mentioned mask blank 100, and is characterized by including: a step of forming a transfer pattern on the light-shielding film 30 by dry etching; a step of forming a transfer pattern on the phase shift film 20 by dry etching using the light-shielding film 30 having the transfer pattern as a mask; a step of forming a light-shielding pattern 30b on the light-shielding film 30 by dry etching using a resist film (resist pattern 40b) having a light-shielding band pattern as a mask. Hereinafter, according to Figure 3 the manufacturing process shown, the manufacturing method of the phase shift mask 200 of the present invention will be described.

[0092] First, a resist film is formed on the hard mask film 31 of the mask blank 100 by spin coating. Next, the first pattern (phase shift pattern) to be formed on the phase shift film 20 is drawn by electron beam exposure on this resist film. In addition, at this time, a ground wire pin (not shown) contacts the light-shielding film 30 on which the resist film is formed, and grounding is ensured between the resist film and the light-shielding film 30 (refer to Figure 2 the ground wire pin grounding portion 16 in). Thereby, charging during exposure drawing can be suppressed. Then, the resist film is subjected to prescribed treatments such as PEB treatment, development treatment, and post-baking treatment, and a first resist pattern 40a corresponding to the phase shift pattern is formed on the resist film (refer to Figure 3 (a)).

[0093] Next, using the resist pattern 40a as a mask, dry etching of the hard mask film 31 is performed using a fluorine-based gas, and a hard mask pattern 31a as the first pattern is formed on the hard mask film 31 (refer to Figure 3(b)). Then, the resist pattern 40a is removed. Additionally, here, dry etching of the light-shielding film 30 can also be performed while leaving the resist pattern 40a without removing it. In this case, the resist pattern 40a disappears during the dry etching of the light-shielding film 30.

[0094] Next, using the hard mask pattern 31a as a mask, dry etching using an oxygen-containing chlorine-based gas is performed to form a light-shielding pattern 30a as a first pattern on the light-shielding film 30 (see Figure 3 (c)). The mixing ratio of the chlorine-based gas and oxygen in the dry etching of the light-shielding film 30, in terms of the gas flow ratio in the etching apparatus, is preferably chlorine-based gas:oxygen = 10 or more:1, more preferably 15 or more:1, and further preferably 20 or more:1. By using an etching gas with a high mixing ratio of the chlorine-based gas, the anisotropy of the dry etching can be improved. Additionally, in the dry etching of the light-shielding film 30, the mixing ratio of the chlorine-based gas and oxygen, in terms of the gas flow ratio in the etching chamber, is preferably chlorine-based gas:oxygen = 40 or less:1.

[0095] Next, using the light-shielding pattern 30a as a mask, dry etching using a fluorine-based gas is performed to form a phase shift pattern 20a as a first pattern on the phase shift film 20, and the hard mask pattern 31a is removed (see Figure 3 (d)). Next, a resist film is formed on the light-shielding pattern 30a by spin coating. For this resist film, a light-shielding pattern as a second pattern to be formed on the light-shielding film 30 is drawn by electron beam lithography. Then, a predetermined process such as a development process is performed to form a resist film having a resist pattern 40b as a second pattern corresponding to the light-shielding pattern (see Figure 3 (e)).

[0096] Next, using the resist pattern 40b as a mask, dry etching using a mixed gas of a chlorine-based gas and oxygen is performed to form a light-shielding pattern 30b as a second pattern on the light-shielding film 30 (see Figure 3 (f)). Further, the resist pattern 40b is removed, and after a predetermined process such as cleaning, a phase shift mask 200 is obtained (see Figure 3 (g)).

[0097] In addition, as the chlorine-based gas used in the dry etching in the above manufacturing process, it is only necessary to contain Cl, and there is no particular limitation. For example, as the chlorine-based gas, Cl2, SiCl2, CHCl3, CH2Cl2, CCl4, BCl3, etc. can be cited. In addition, as the fluorine-based gas used in the dry etching in the above manufacturing process, it is only necessary to contain F, and there is no particular limitation. For example, as the fluorine-based gas, CHF3, CF4, C2F6, C4F8, SF6, etc. can be cited. In particular, the fluorine-based gas without C has a relatively low etching rate for the glass substrate, so the damage to the glass substrate can be further reduced.

[0098] The phase shift mask 200 of the present invention is manufactured using the above mask blank 100. Therefore, grounding against the resist can be ensured, and the generation of dust can be suppressed, so that good pattern transfer can be performed.

[0099] The manufacturing method of the semiconductor device of the present invention is characterized in that it has a step of exposing and transferring a transfer pattern onto a resist film on a semiconductor substrate using the above phase shift mask 200 or a phase shift mask 200 manufactured using the above mask blank 100. Therefore, even if the phase shift mask 200 is set on the exposure apparatus and ArF exposure light is irradiated from the light-transmitting substrate 1 side of the phase shift mask 200 to perform exposure transfer to the transfer object (such as a resist film on a semiconductor wafer), the desired pattern can be transferred to the transfer object with high precision.

[0100] Examples

[0101] Hereinafter, the embodiments of the present invention will be described more specifically by way of examples.

[0102] (Example 1)

[0103] (Manufacture of mask blank)

[0104] Refer to Figure 1, a light-transmissive substrate 1 made of synthetic quartz glass with a main surface dimension of approximately 152 mm × approximately 152 mm and a thickness of approximately 6.35 mm is prepared. The main surface of the light-transmissive substrate 10 is polished to a specified surface roughness (Rq of 0.2 nm or less), and then, a specified cleaning treatment and drying treatment are performed. The light-transmissive substrate 10 has two main surfaces 11 and four side surfaces 12, and a chamfered surface 13 is provided between the main surface 11 and the side surface 12. When observed from the main surface 11 side, the boundary (ridge line) between the chamfered surface 13 and the main surface 11 is located at a position on the center 17 side only 0.4 mm away from the side surface 12 of the substrate. At multiple parts of the main surface 11a of the light-transmissive substrate 10, the surface reflectance Rs of light with wavelengths from 400 nm to 700 nm was measured, and the result was 7% or less in any region (wavelength 400 nm: 6.99%, wavelength 550 nm: 6.75%, wavelength 700 nm: 6.62%).

[0105] Next, the light-transmissive substrate 10 is set in a single-piece DC sputtering apparatus, and a mixed sintered target of molybdenum (Mo) and silicon (Si) (Mo:Si = 11 atomic%:89 atomic%) is used, and a reactive sputtering (DC sputtering) using a mixed gas of argon (Ar), nitrogen (N2), and helium (He) as the sputtering gas is performed to form a phase shift film 20 composed of molybdenum, silicon, and nitrogen on the light-transmissive substrate 10 with a thickness of 69 nm. When forming the phase shift film 20 by sputtering, the Figure 4 shown mask was used. The mask used has a square opening with a side length of 146 mm based on the center of the substrate.

[0106] Next, the light-transmissive substrate 10 on which the phase shift film 20 is formed is subjected to a heat treatment for reducing the film stress of the phase shift film 20 and for forming an oxide layer on the surface layer. Specifically, using a heating furnace (electric furnace), the heating temperature is set to 450 °C and the heating time is set to 1 hour in the atmosphere for the heat treatment. Using a phase shift amount measuring device (MPM193, manufactured by Lasertec Corporation), the transmittance and phase difference of the phase shift film 20 after the heat treatment for light with a wavelength of 193 nm were measured, and the result was that the transmittance was 6.0% and the phase difference was 177.0 degrees (deg).

[0107] Next, a light-transmissive substrate 10 having a phase shift film 20 formed thereon is placed in a single-chamber DC sputtering apparatus, and reactive sputtering (DC sputtering) is performed using a chromium (Cr) target in a mixed gas environment of argon (Ar), carbon dioxide (CO2), and helium (He). As a result, a light-shielding film (CrOC film) 30 composed of chromium, oxygen, and carbon is formed with a film thickness of 18 nm in contact with the phase shift film 20. A mask was also used during the sputtering for forming the light-shielding film 30. However, the mask used herein has an opening in the shape of a square with a side length of 150 mm based on the center of the substrate (i.e., the design area is a square area with a side length of 150 mm). The size of one side length of the main surface 11 of the substrate is 151.2 mm, and the margin from the design area is quite small.

[0108] Next, a heat treatment is performed on the light-transmissive substrate 10 having the above-described light-shielding film (CrOC film) 30 formed thereon. Specifically, using a hot plate, the heating temperature is set to 280°C and the heating time is set to 5 minutes in the atmosphere for the heat treatment. After the heat treatment, for the light-transmissive substrate 10 having the phase shift film 20 and the light-shielding film 30 laminated thereon, using a spectrophotometer (Cary 4000 manufactured by Agilent Technologies), the optical density at the wavelength (about 193 nm) of the light of an ArF excimer laser for the laminated structure of the phase shift film 20 and the light-shielding film 30 is measured, and as a result, it is confirmed that it exceeds 2.0.

[0109] Next, enlarged image data is obtained for each of the four corners of the main surface 11a of the light-transmissive substrate 10 having the light-shielding film 30 formed thereon, using a CCD camera. The boundary between the light-shielding film 30 and the main surface 11a can be visually recognized in each of the obtained image data. However, in the image data for each of these four corners, a portion where the entire main surface 11a is covered by the light-shielding film 30 was found (there is a possibility that the light-shielding film 30 spreads to the chamfered surface 13). That is, it was determined that the mask was not placed in an appropriate position. Then, for the image data of each of the four corners, with the side surface 12 as a reference, the distance to the boundary between the region where the main surface 11a is exposed (the region where the light-shielding film 30 is not formed) and the region where the light-shielding film 30 is formed is measured respectively. Based on this result, the difference between the center 17 of the light-transmissive substrate 10 and the center of the mask during sputtering is calculated, and the setting position of the mask is finely adjusted.

[0110] Next, another light-transmissive substrate 10 was prepared, and a phase shift film 20 and a light-shielding film 30 were formed by sputtering in the same order as above. Further, in the same order as above, image data of each of the four corners of the main surface 11a of the light-transmissive substrate 10 on which the light-shielding film 30 was formed were obtained. Then, in the same order as above, for each of the image data of the four corners, the distance to the boundary between the region where the main surface 11a was exposed and the region where the light-shielding film 30 was formed was measured with the side surface 12 as a reference. As a result, at any of the four corners, the boundary between the region where the main surface 11a was exposed and the region where the light-shielding film 30 was formed could be visually recognized. In addition, the distances to the boundary with the side surface 12 as a reference were also substantially the same.

[0111] Next, the film thickness distribution near the boundary between the main surface 11a and the light-shielding film 30 was measured with a contact type micro shape measuring machine (ET-4000 manufactured by Kosaka Laboratory Ltd.). The results are as Figure 5 shown. From this result, it was found that the light-shielding film 30 was formed starting from a position at a distance between 0.47 mm and 0.53 mm from the side surface 12 on the main surface 11a toward the inside. In addition, the surface reflectance Rf of light with wavelengths from 400 nm to 700 nm was measured at a plurality of measurement sites (sites) where the thickness of the light-shielding film 30 was between 9 nm and 10 nm. The average value was 23.65%, and the surface reflectance Rf of light in the above wavelength range was 20% or more. Further, the contrast (Rf / Rs) of the surface reflectance Rf of the light-shielding film 30 at the above measurement sites with respect to the surface reflectance Rs of the main surface 11a was calculated. The minimum result was 3.29, which was 3.0 or more. Further, the surface reflectance RfB of light with a wavelength of 400 nm, the surface reflectance RfG of light with a wavelength of 550 nm, and the surface reflectance RfR of light with a wavelength of 700 nm at the measurement position where the surface reflectance Rf was the maximum (24.69%) were 24.96%, 25.06%, and 24.08%, respectively. The standard deviation calculated among the three surface reflectances RfB, RfG, and RfR was 0.441, which was 1.0 or less.

[0112] The region where the light-shielding film 30 was formed (i.e., the inner region 14) was divided into regions of 55 μm × 55 μm, and the average of the film thicknesses measured in each region was taken, thereby calculating the average film thickness of the light-shielding film 30. The calculated average film thickness of the light-shielding film 30 was 18 nm.

[0113] Next, prepare another light-transmissive substrate 10. In the same order as above, form a phase shift film 20 by sputtering, and form a light-shielding film 30 by sputtering at the set position of the finely adjusted mask plate. Next, place the light-transmissive substrate 10 with the phase shift film 20 and the light-shielding film 30 laminated in a single-piece DC sputtering apparatus. Using a silicon (Si) target, form a hard mask film 31 composed of silicon, nitrogen, and oxygen with a thickness of 5 nm on the light-shielding film 30 and inside the end portion of the light-shielding film 30 by reactive sputtering (DC sputtering) in an environment of a mixed gas of argon (Ar) and nitric oxide (NO). At this time, use a mask plate having a square opening with a side length of 146 mm based on the center of the substrate. Furthermore, perform a prescribed cleaning process to fabricate the mask blank 100 of Example 1.

[0114] Prepare a substrate on which only the light-shielding film 30 is formed on the main surface 11a of another light-transmissive substrate 10 under the same conditions and heat treatment is performed. Measure the sheet resistance value of this light-shielding film 30. As a result, it is 0.246 kΩ / Square, which is 0.5 kΩ / Square or less. In addition, using a spectroscopic ellipsometer, measure the refractive index n and extinction coefficient k of the light-shielding film 30 for light with wavelengths from 400 nm to 700 nm. As a result, the extinction coefficient k for light with a wavelength of 400 nm is 2.33, the extinction coefficient k for light with a wavelength of 550 nm is 2.53, and the extinction coefficient k for light with a wavelength of 700 nm is 3.01, which can be confirmed to be 2.0 or more. In addition, the refractive index n for light with a wavelength of 400 nm is 2.52, the refractive index n for light with a wavelength of 550 nm is 2.96, and the refractive index n for light with a wavelength of 700 nm is 3.57.

[0115] Furthermore, analyze the light-shielding film 30 by X-ray photoelectron spectroscopy (with XPS and RBS correction). As a result, it can be confirmed that the region near the surface on the side opposite to the light-transmissive substrate 10 side of the light-shielding film 30 (the region with a depth of about 2 nm from the surface) has a compositional gradient portion with a higher oxygen content than other regions (the oxygen content is 40 atomic% or more). In addition, it is known that the average value of the contents of each constituent element in the region of the light-shielding film 30 other than the compositional gradient portion is Cr: 71 atomic%, O: 14 atomic%, C: 15 atomic%. Furthermore, the difference in each constituent element in the thickness direction of the region of the light-shielding film 30 other than the compositional gradient portion is 3 atomic% or less, and it can be confirmed that there is substantially no compositional gradient in the thickness direction.

[0116] Next, using the mask blank 100 of Example 1, a halftone type phase shift mask 200 of Example 1 was manufactured in the following order. First, the surface of the hard mask film 31 was subjected to HMDS treatment. Next, by spin coating, an antireflective film made of a chemically amplified resist for electron beam lithography was formed in contact with the surface of the hard mask film 31 with a film thickness of 80 nm. Next, for this antireflective film, a first pattern as a phase shift pattern to be formed on the phase shift film 20 was electron beam lithographed, and a prescribed development process and cleaning process were performed to form an antireflective pattern 40a having the first pattern (see Figure 3 (a)). At the time of this electron beam lithography, at the ground pin grounding portion 16, the light shielding film 30 was brought into contact with a ground pin (not shown). Thereby, an electron beam can be lithographed at a desired position on the antireflective film to form a desired antireflective pattern 40a.

[0117] Next, using the antireflective pattern 40a as a mask, dry etching using CF4 gas was performed to form a hard mask pattern 31a as the first pattern on the hard mask film 31 (see Figure 3 (b)).

[0118] Next, the antireflective pattern 40a was removed. Next, using the hard mask pattern 31a as a mask, dry etching using a mixed gas of chlorine (Cl2) and oxygen (O2) (gas flow ratio Cl2:O2 = 13:1) was performed to form a light shielding pattern 30a as the first pattern on the light shielding film 30 (see Figure 3 (c)).

[0119] Next, using the light shielding pattern 30a as a mask, dry etching using a fluorine-based gas (SF6 + He) was performed to form a phase shift pattern 20a as the first pattern on the phase shift film 20, and at the same time, the hard mask pattern 31a was removed (see Figure 3 (d)).

[0120] Next, on the light shielding pattern 30a, an antireflective film made of a chemically amplified resist for electron beam lithography was formed by spin coating with a film thickness of 150 nm. Next, the antireflective film was exposed and lithographed with a second pattern as a pattern (pattern including a light shielding band pattern) to be formed on the light shielding film, and then prescribed processes such as a development process were performed to form an antireflective pattern 40b having a light shielding pattern (see Figure 3 (e)). Next, using the antireflective pattern 40b as a mask, dry etching using a mixed gas of chlorine (Cl2) and oxygen (O2) (gas flow ratio Cl2:O2 = 4:1) was performed to form a light shielding pattern 30b as the second pattern on the light shielding film 30 (see Figure 3 (f)). Further, the antireflective pattern 40b was removed, and after performing prescribed processes such as cleaning, the phase shift mask 200 was obtained (seeFigure 3 (g))。

[0121] Regarding the phase shift mask 200 fabricated in the above order, simulation of the transfer image when exposing a resist film transferred onto a semiconductor device with exposure light having a wavelength of 193 nm was performed using AIMS193 (manufactured by Carl Zeiss). Verification of the simulated exposure transfer image was carried out, and the results fully met the design specifications. From these results, it can be seen that even if the phase shift mask 200 of this Example 1 is set on the mask stage of an exposure apparatus and exposed onto a resist film on a semiconductor device, ultimately, a circuit pattern formed on the semiconductor device can be precisely formed with high accuracy.

[0122] (Comparative Example 1)

[0123] (Manufacture of Mask Blank)

[0124] The mask blank of this Comparative Example 1 was manufactured in the same order as in Example 1, except for the light-shielding film. The light-shielding film of this Comparative Example 1 had different film-forming conditions from the light-shielding film 3 of Example 1. Specifically, a light-transmissive substrate on which a phase shift film was formed was set in a single-wafer DC sputtering apparatus, and reactive sputtering (DC sputtering) was performed in an environment of a mixed gas of argon (Ar), carbon dioxide (CO2), and helium (He) using a chromium (Cr) target. Thereby, a light-shielding film (CrOC film) composed of chromium, oxygen, and carbon was formed with a film thickness of 24 nm in contact with the phase shift film. Also, as in Example 1 during the sputtering for forming this light-shielding film 30, a mask plate having a square opening with a side length of 150 mm was used.

[0125] Next, heat treatment was performed on the light-transmissive substrate on which the above light-shielding film (CrOC film) was formed under the same conditions as in the case of Example 1. After the heat treatment, for the light-transmissive substrate on which the phase shift film and the light-shielding film were laminated, using a spectrophotometer (Cary4000 manufactured by Agilent Technologies), the optical density at a wavelength (about 193 nm) of light from an ArF excimer laser of the laminated structure of the phase shift film and the light-shielding film was measured, and the result was confirmed to be 3.0 or more.

[0126] Next, in the same order as in Example 1, enlarged image data was obtained using a CCD camera for the four corners of the main surface of the light-transmissive substrate on which the light-shielding film of Comparative Example 1 was formed. However, the boundary between the light-shielding film and the main surface was difficult to visually identify in each of the obtained image data. Therefore, it was difficult to calculate the difference between the center 17 of the light-transmissive substrate 10 and the center of the mask plate during sputtering, and it was difficult to finely adjust the setting position of the mask plate with high precision.

[0127] Next, the film thickness distribution near the boundary between the main surface and the light-shielding film of Comparative Example 1 was measured using a contact-type fine shape measuring machine (ET-4000 manufactured by Kosaka Laboratory Ltd.). Based on the above image data, the surface reflectance Rf of multiple measurement sites (sites) where the thickness of the light-shielding film was between 9 nm and 10 nm with respect to light having wavelengths from 400 nm to 700 nm was measured. As a result, the average was 14.85%, and the surface reflectance Rf with respect to light within the above wavelength range was significantly lower than 20%. Furthermore, the contrast (Rf / Rs) of the surface reflectance Rf of the light-shielding film of Comparative Example 1 at the above measurement sites with respect to the surface reflectance Rs of the main surface was calculated. As a result, the maximum value was 2.27, which was significantly lower than 3.0. Furthermore, the surface reflectance RfB of the measurement site with the maximum surface reflectance Rf (15.51%) with respect to light having a wavelength of 400 nm was 17.85%, the surface reflectance RfG with respect to light having a wavelength of 550 nm was 15.37%, and the surface reflectance RfR with respect to light having a wavelength of 700 nm was 13.32%. The standard deviation calculated among the three surface reflectances RfB, RfG, and RfR was 1.853, which significantly exceeded 1.0.

[0128] In addition, the region where the light-shielding film 30 was formed (i.e., the inner region 14) was divided into regions of 55 μm × 55 μm, and the average of the film thicknesses measured in each region was taken. Thus, the average film thickness of the light-shielding film 30 was calculated. The calculated average film thickness of the light-shielding film 30 was 24 nm.

[0129] A substrate on which only a light-shielding film was formed on the main surface of another light-transmissive substrate under the same conditions and heat treatment was performed was prepared. The sheet resistance value of the light-shielding film of Comparative Example 1 was measured. As a result, it was 168 kΩ / Square, which significantly exceeded 1.0 kΩ / Square. In addition, using a spectroscopic ellipsometer, the refractive index n and extinction coefficient k of the light-shielding film with respect to light having wavelengths from 400 nm to 700 nm were measured. As a result, the extinction coefficient k with respect to light having a wavelength of 400 nm was 1.23, the extinction coefficient k with respect to light having a wavelength of 550 nm was 1.27, and the extinction coefficient k with respect to light having a wavelength of 700 nm was 1.2, which was lower than 2.0. In addition, the refractive index n with respect to light having a wavelength of 400 nm was 2.42, the refractive index n with respect to light having a wavelength of 550 nm was 2.64, and the refractive index n with respect to light having a wavelength of 700 nm was 2.67.

[0130] Furthermore, the light-shielding film was analyzed by X-ray photoelectron spectroscopy (with XPS and RBS corrections). As a result, it was confirmed that the region near the surface on the side opposite to the light-transmissive substrate side of the light-shielding film (the region with a depth of about 2 nm from the surface) has a compositional gradient portion with a higher oxygen content than the other regions (the oxygen content is 40 atomic % or more). In addition, it was found that the content of each constituent element in the region of the light-shielding film other than the compositional gradient portion is, on average, Cr: 56 atomic %, O: 29 atomic %, and C: 15 atomic %. Furthermore, the difference in each constituent element in the thickness direction of the region of the light-shielding film other than the compositional gradient portion is 3 atomic % or less, and it was confirmed that there is substantially no compositional gradient in the thickness direction.

[0131] In the light-shielding film of Comparative Example 1, since it is difficult to visually identify the boundary between the region where the main surface is exposed and the region where the light-shielding film is formed, it is difficult to finely adjust the setting position of the mask substrate with high precision. Therefore, it is difficult to reliably prevent the light-shielding film from spreading and forming on the side surface or chamfer surface of the substrate.

[0132] (Manufacture of Phase-Shift Mask)

[0133] Next, using the mask blank of Comparative Example 1, multiple phase-shift masks of Comparative Example 1 were fabricated in the same order as in Example 1.

[0134] For the fabricated phase-shift masks of Comparative Example 1, in the same manner as in Example 1, AIMS193 (manufactured by Carl Zeiss) was used to simulate the transfer image when exposing and transferring a resist film onto a semiconductor device with exposure light having a wavelength of 193 nm. The simulated exposure transfer image was verified, and as a result, transfer defects were confirmed in several phase-shift masks. It is speculated that this is because incorrect pattern drawing cannot be performed due to charging of the resist, or dust is generated due to the light-shielding film adhering to the chamfer surface of the substrate, which are the main causes of the transfer defects. From this result, it can be said that when the phase-shift mask of Comparative Example 1 is set on the mask stage of an exposure apparatus and exposed and transferred onto a resist film on a semiconductor device, defective portions will ultimately be formed in the circuit pattern formed on the semiconductor device.

[0135] Symbol Explanation

[0136] 10: Light-transmissive substrate

[0137] 11(11a, 11b): Main surface

[0138] 12: Side surface

[0139] 13: Chamfer surface

[0140] 14: Inner region

[0141] 15: Outer peripheral region

[0142] 16: Ground wire pin grounding part

[0143] 17: Center

[0144] 20: Phase shift film

[0145] 20a: Phase shift pattern

[0146] 30: Light-shielding film

[0147] 30a, 30b: Light-shielding pattern

[0148] 31: Hard mask film

[0149] 31a: Hard mask pattern

[0150] 40a, 40b: Resist pattern

[0151] 50: Sputtering target

[0152] 51: Substrate holding part

[0153] 52: Masking plate

[0154] 100: Mask blank

[0155] 200: Phase shift mask

Claims

1. A mask blank, comprising a substrate and a thin film, characterized in that: The substrate has two main surfaces and side surfaces, and a chamfered surface is provided between the two main surfaces and the side surfaces. One of the two main surfaces has: an inner region including the center of the main surface, and an outer peripheral region outside the inner region. The thin film is provided on the inner region of the main surface. The surface reflectance Rs of the outer peripheral region of the main surface to light with a wavelength of 400 nm to 700 nm is 10% or less. When the surface reflectance of a part in the range of 9 nm to 10 nm of the film thickness of the thin film to light with a wavelength of 400 nm to 700 nm is set as Rf, Rf / Rs as the contrast is 3.0 or more.

2. The mask blank according to claim 1, characterized in that: The surface reflectance of the part to light with a wavelength of 400 nm to 700 nm is 20% or more.

3. The mask blank according to claim 1, characterized in that: When the surface reflectance of the part to light with a wavelength of 400 nm is set as RfB, the surface reflectance of the part to light with a wavelength of 550 nm is set as RfG, and the surface reflectance of the part to light with a wavelength of 700 nm is set as RfR, the standard deviation calculated among the three surface reflectances RfB, RfG, and RfR is 1.0 or less.

4. The mask blank according to claim 1, characterized in that: The extinction coefficient k of the thin film to light with a wavelength of 400 nm to 700 nm is 1.5 or more.

5. The mask blank according to claim 1, characterized in that: The average film thickness of the thin film is greater than 10 nm and 60 nm or less.

6. The mask blank according to any one of claims 1 to 5, characterized in that: An intermediate film is provided between the main surface and the thin film in a region from the outer edge of the inner region toward the inner side of the center of the one main surface.

7. The mask blank according to claim 6, characterized in that: The intermediate film is a semi-transparent film that allows the exposure light of an ArF excimer laser to pass through with a transmittance of 1% or more.

8. A transfer mask, characterized in that: It is formed by providing a transfer pattern on the thin film in the mask blank according to any one of claims 1 to 5.

9. A transfer mask, characterized in that: It is formed by providing a transfer pattern on the intermediate film in the mask blank according to claim 6 or 7 and providing a pattern including a light-shielding band on the thin film.

10. A method for manufacturing a semiconductor device, characterized in that: It includes a step of exposing and transferring a transfer pattern onto a resist film on a semiconductor substrate using the transfer mask according to claim 8 or 9.

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