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

Abstract

The present invention aims to provide a mask blank capable of producing a transfer mask having a fine auxiliary pattern of about 20 nm or less with good accuracy. The mask blank has the following structure: a pattern forming film (2) containing a transition metal, a first hard mask film (3) containing oxygen and one or more elements selected from silicon and tantalum, and a second hard mask film (4) containing a transition metal are sequentially stacked on a main surface of a substrate (1), the content of the transition metal in the second hard mask film is less than that in the pattern forming film, the area of the first hard mask film on the main surface is smaller than that of the pattern forming film, and the second hard mask film at least partially contacts the pattern forming film.

Description

Technical Field

[0001] This invention relates to a method for manufacturing mask blanks, transfer masks, and semiconductor devices. Background Technology

[0002] Generally, photolithography is used to form fine patterns in the manufacturing process of semiconductor devices. Furthermore, the formation of these fine patterns typically requires multiple substrates called transfer masks. When miniaturizing the patterns in 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. In recent years, the exposure light source used in semiconductor device manufacturing has been shortening its wavelength from KrF excimer lasers (wavelength 248 nm) to ArF excimer lasers (wavelength 193 nm).

[0003] As a type of transfer mask, in addition to existing binary masks with a light-blocking pattern containing chromium-based materials on a transparent substrate, halftone phase-shift masks are known. This halftone phase-shift mask consists of a mask pattern formed on a transparent substrate, comprising a portion (transparent portion) that allows light of an intensity substantially contributing to exposure to pass through and a portion (semi-transparent portion) that allows light of an intensity substantially not contributing to exposure to pass through to pass through. Furthermore, the phase of the light passing through the semi-transparent portion is shifted, so that the phase of the light passing through the semi-transparent portion is substantially reversed with the phase of the light passing through the transparent portion. This allows the light passing through the vicinity of the boundary between the transparent and semi-transparent portions to cancel each other out, thereby maintaining good contrast at the boundary.

[0004] As a mask blank for halftone phase shift masks, there are currently known mask blanks with a structure consisting of a halftone phase shift film constituting the semi-transparent part, a light-shielding film, and an etch mask film (hard mask film) formed of inorganic materials stacked together.

[0005] In addition, for binary masks, there are also known mask blanks with a structure in which an etched mask film (hard mask film) is stacked on a light-shielding film.

[0006] For example, Patent Document 1 discloses a mask blank in which a light-shielding film, a silicon-containing mask layer, and a chromium nitride film are sequentially formed on a transparent substrate.

[0007] In addition, Patent Document 2 discloses a method for manufacturing a mask blank, wherein the mask blank is a mask blank for electron beam drawing to form an etch-resistant pattern by electron beam drawing. The manufacturing method includes: sequentially forming a light-shielding film and an etching mask film on a transparent substrate, wherein the etching mask film is formed from an inorganic material that is resistant to etching of the light-shielding film, and when forming the etching mask film, a shielding plate is used to shield so that no film is formed on at least one side of the substrate.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent No. 5348866

[0011] Patent Document 2: Japanese Patent No. 5393972 Summary of the Invention

[0012] The problem the invention aims to solve

[0013] In photolithography, the smallest size (resolution) that can be transferred using a projection exposure device is directly proportional to the wavelength of the light used for exposure and inversely proportional to the aperture number (NA) of the lens in the projection optical system. Therefore, with the requirement for miniaturization of semiconductor devices, the wavelength of exposure light is shortened and the NA of the projection optical system is increased. However, the limit has been reached in meeting this requirement by shortening the wavelength and increasing the NA alone.

[0014] Therefore, in order to improve resolution, super-resolution techniques have been proposed in recent years to achieve miniaturization by reducing the value of the process constant k1 (k1 = resolution linewidth × number of apertures in the projection optics system / wavelength of the exposure light). As one such super-resolution technique, there is a method to optimize the mask pattern by assigning auxiliary patterns and linewidth offsets to the mask pattern in accordance with the characteristics of the exposure optics system.

[0015] The method of using an auxiliary pattern is as follows: a pattern (hereinafter referred to as an auxiliary pattern) that is below the resolution limit of the projection optics system and not transferred to the wafer is placed near the pattern transferred to the wafer (hereinafter referred to as the main pattern), and a transfer mask that has the effect of improving the resolution and depth of focus of the main pattern is used. The auxiliary pattern is also called SRAF (Sub Resolution Assist Feature) (hereinafter, in this invention, the auxiliary pattern is also referred to as SRAF).

[0016] However, with the miniaturization of semiconductor device patterns, difficulties have arisen in the fabrication of transfer masks with auxiliary patterns. Firstly, auxiliary patterns, as mentioned above, need to be smaller than the main pattern size to avoid being imaged on the wafer. As a result, with the miniaturization of the main pattern size, the required linewidth of the auxiliary pattern has been reduced to a tiny size of approximately 100 nm to 40 nm, and further to approximately 20 nm.

[0017] However, it was found that it is difficult to fabricate transfer masks with auxiliary patterns of such small size as about 20 nm using existing mask blanks.

[0018] This invention was made to solve existing problems, and its object is to provide a mask blank capable of fabricating transfer masks with auxiliary patterns of a small size of about 20 nm with good precision. Furthermore, this invention provides a method for manufacturing a transfer mask, which, by using this mask blank, enables the formation of fine patterns on a patterning thin film with good precision. Additionally, this invention aims to provide a method for manufacturing a semiconductor device using a transfer mask manufactured by such a method.

[0019] Problem Solving Methods

[0020] To achieve the above-mentioned objectives, the present invention includes the following solutions.

[0021] (Option 1)

[0022] A mask blank has the following structure: a pattern forming film, a first hard mask film, and a second hard mask film are sequentially stacked on the main surface of a substrate.

[0023] The thin film used to form the above pattern contains a transition metal.

[0024] The first hard mask film mentioned above contains oxygen and one or more elements selected from silicon and tantalum.

[0025] The second hard mask film mentioned above contains a transition metal.

[0026] The transition metal content of the second hard mask film is less than that of the thin film for pattern formation.

[0027] The area on the main surface where the first hard mask film is formed is smaller than the area where the pattern forming film is formed.

[0028] The second hard mask film is at least partially in contact with the pattern forming film.

[0029] (Option 2)

[0030] According to the mask blank described in Scheme 1, wherein...

[0031] The total oxygen and nitrogen content of the second hard mask film is greater than the total oxygen and nitrogen content of the pattern forming film.

[0032] (Option 3)

[0033] According to the mask blank described in scheme 1 or 2, wherein,

[0034] The area on the main surface where the second hard mask film is formed is larger than the area where the first hard mask film is formed.

[0035] (Option 4)

[0036] According to any one of Schemes 1 to 3, the mask blank, wherein...

[0037] The difference between the content of the transition metal in the thin film for forming the pattern and the content of the transition metal in the second hard mask film is 10 atomic percent or more.

[0038] (Option 5)

[0039] The mask blank according to any one of Schemes 1 to 4, wherein

[0040] The total oxygen and nitrogen content of the second hard mask film mentioned above is 30 atomic percent or more.

[0041] (Option 6)

[0042] According to any one of Schemes 1 to 5, the mask blank, wherein...

[0043] The thickness of the second hard mask film mentioned above is less than 5 nm.

[0044] (Option 7)

[0045] According to any one of Schemes 1 to 6, the mask blank, wherein...

[0046] The total oxygen and nitrogen content of the first hard mask film is 50 atomic percent or more.

[0047] (Option 8)

[0048] According to any one of Schemes 1 to 7, the mask blank, wherein...

[0049] The oxygen content of the first hard mask film mentioned above is 50 atomic percent or more.

[0050] (Option 9)

[0051] According to any one of schemes 1 to 8, the mask blank, wherein...

[0052] The thickness of the first hard mask film mentioned above is 7 nm or more.

[0053] (Option 10)

[0054] The mask blank according to any one of schemes 1 to 9, wherein...

[0055] The thickness of the thin film used to form the above pattern is less than 60 nm.

[0056] (Option 11)

[0057] According to any one of Schemes 1 to 10, the mask blank, wherein,

[0058] The thin film used for pattern formation is a light-shielding film, and a phase-shifting film is provided between the substrate and the light-shielding film.

[0059] (Option 12)

[0060] According to the mask blank described in Scheme 11, wherein...

[0061] The aforementioned phase-shifting film contains silicon.

[0062] (Option 13)

[0063] According to the mask blank described in scheme 11 or 12, wherein,

[0064] The aforementioned phase-shifting film has the following functions:

[0065] The function of allowing exposure light to pass through with a transmittance of more than 1%, and

[0066] This function creates a phase difference of 150 degrees or more and 210 degrees or less between the exposure light that has passed through the phase shift film and the exposure light that has passed through only the same distance as the thickness of the phase shift film in the air.

[0067] (Option 14)

[0068] A method for manufacturing a transfer mask, which is a method for manufacturing a transfer mask using a mask blank as described in any one of embodiments 1 to 10, the method comprising the following steps:

[0069] The process of forming a transfer pattern on the second hard mask film by using a dry etching process with an oxygen-chlorine gas to form the transfer pattern on the second hard mask film as a mask.

[0070] Using the second hard mask film with the transfer pattern formed thereon as a mask, a process is performed to form the transfer pattern on the first hard mask film by dry etching with fluorine-based gases; and

[0071] Using the first hard mask film with the transfer pattern formed thereon as a mask, a process is performed to form a transfer pattern on the thin film for pattern formation by dry etching with an oxygen-containing chlorine gas.

[0072] (Option 15)

[0073] A method for manufacturing a transfer mask, comprising a method for manufacturing a transfer mask using a mask blank as described in any one of embodiments 11 to 13, the method comprising:

[0074] The process of forming a transfer pattern on the second hard mask film by using a dry etching process with an oxygen-chlorine gas to form the transfer pattern on the second hard mask film as a mask.

[0075] The process of forming a transfer pattern on the first hard mask film by using the second hard mask film with the transfer pattern formed thereon as a mask and dry etching with fluorine gas.

[0076] Using the first hard mask film with the transfer pattern formed thereon as a mask, a process is performed to form the transfer pattern on the light-shielding film by dry etching with an oxygen-chlorine gas; and

[0077] The process involves using the light-shielding film with the transfer pattern formed thereon as a mask, and then using dry etching with fluorine gas to form the transfer pattern on the phase-shifting film.

[0078] (Option 16)

[0079] A method for manufacturing a semiconductor device, the method comprising the following steps:

[0080] Using a transfer mask manufactured by the method described in Scheme 14 or 15, a transfer pattern is exposed and transferred onto a resist film on a semiconductor substrate.

[0081] The effects of the invention

[0082] According to the mask blank of the present invention, a transfer mask having an auxiliary pattern of a small size of about 20 nm can be manufactured with good precision. Furthermore, by using this mask blank, the present invention can manufacture a transfer mask capable of forming fine patterns on a patterning thin film with good precision. Additionally, the present invention can provide a method for manufacturing a semiconductor device using a transfer mask manufactured by such a method. Attached Figure Description

[0083] Figure 1 This is a cross-sectional view showing the structure of the mask blank (binary mask blank) in the first embodiment of the present invention.

[0084] Figure 2 This is a cross-sectional view showing the structure of the mask blank (phase-shifting mask blank) in the second embodiment of the present invention.

[0085] Figure 3 This is a cross-sectional view showing the configuration of the transfer mask (binary mask) in the first embodiment of the present invention.

[0086] Figure 4 This is a cross-sectional schematic diagram showing the manufacturing process of the transfer mask (phase shift mask) in the second embodiment of the present invention.

[0087] Symbol Explanation

[0088] 1 substrate

[0089] 2. Light-shielding film (film for pattern forming)

[0090] 2b A light-shielding film with the second pattern (light-shielding pattern)

[0091] 3. First hard mask

[0092] 3a A first hard mask with a first pattern (first hard mask pattern)

[0093] 4. Second hard mask

[0094] 4a A second hard mask film having the first pattern (second hard mask pattern)

[0095] 4b A second hard mask with the second pattern (second hard mask pattern)

[0096] 5. Anti-corrosion film

[0097] 5a Resist film with pattern 1 (resist pattern)

[0098] 6b Resist film with pattern 2 (resist pattern)

[0099] 10. Mask blank (binary mask blank)

[0100] 11 base plate

[0101] 12. Phase-shifting film (thin film for patterning)

[0102] 12a Phase-shifting film with the first pattern (phase-shifting pattern)

[0103] 13. Light-shielding film (for pattern forming)

[0104] 13a A light-shielding film with pattern 1 (light-shielding pattern)

[0105] 13c Light-shielding film with a third pattern (light-shielding pattern)

[0106] 14 First Hard Mask

[0107] 14a A first hard mask film having a first pattern (first hard mask pattern)

[0108] 15. Second Hard Mask

[0109] 15a A second hard mask film having the first pattern (second hard mask pattern)

[0110] 15b A second hard mask with a second pattern (second hard mask pattern)

[0111] 16. Anti-corrosion film

[0112] 16a Resist film with pattern 1 (resist pattern)

[0113] 17b Resist film with pattern 2 (resist pattern)

[0114] 18c Resist film with third pattern (resist pattern)

[0115] 20. Mask blank (phase-shifting mask blank)

[0116] 100 Transfer Mask (Binary Mask)

[0117] 200 Transfer Mask (Phase Shift Mask) Detailed Implementation

[0118] Before describing the embodiments of the present invention, the process of completing the present invention will be described below.

[0119] When forming an auxiliary pattern with a linewidth of approximately 20 nm as described above on a pattern-forming thin film (such as a light-shielding film) made of a transition metal, it is difficult to form the auxiliary pattern on the pattern-forming thin film using dry etching with an organic resist pattern as a mask. This is because, during dry etching, the resist pattern is etched more in the film thickness direction, requiring a thicker resist film. Furthermore, the resist pattern is also etched more in the sidewall direction (side etching). Generally, the linewidth is expected to be larger than the actual formed linewidth due to the effect of this side etching, and the pattern is drawn on the resist film using an electron beam and then exposed. If the side etching amount is large, this adjustment becomes difficult.

[0120] To address these issues, a hard mask film made of silicon-based material was considered, placed between the patterning thin film and the resist pattern. In this case, the following process is performed: first, the hard mask film is dry-etched using the resist pattern as a mask to form a hard mask pattern; next, the patterning thin film is dry-etched using the hard mask film as a mask to form a thin film pattern. The hard mask film has virtually no optical limitations as required for the patterning thin film. Therefore, the thickness of the hard mask film can be thinner than that of the patterning thin film. Furthermore, the resist film only needs to have a thickness sufficient to function as a mask during the dry etching process when patterning the hard mask film.

[0121] The thinner the hard mask film, the thinner the resist film can be. However, during dry etching of the patterning film, although not as significantly as with the patterning film, the hard mask film is still etched. Furthermore, there is a tendency for the sidewall verticality of the pattern formed by dry etching to decrease as the hard mask film thickness increases. During dry etching of the patterning film using the hard mask pattern as a mask, the edges of the hard mask pattern (the ridges between the upper surface and sidewalls of the hard mask pattern) are particularly prone to etching. If these edges become rounded during dry etching, the shape accuracy (LER, Line Edge Roughness, etc.) of the pattern formed on the patterning film tends to decrease. The thinner the hard mask film, the lower the shape accuracy of the pattern formed on the patterning film. This decrease in shape accuracy is particularly significant when forming auxiliary patterns with a linewidth of approximately 20 nm using the patterning film. Therefore, hard mask films must have a certain thickness.

[0122] Generally, when patterning and exposing a resist film using an electron beam, a grounding mechanism or similar device contacts the thin film beneath the resist to allow charged electrons to escape from the resist. However, silicon oxide-based hard masks lack conductivity, making it difficult for electrons to escape from the resist through the hard mask alone. Transition metal patterning films have higher conductivity, allowing electrons in the resist to escape from the patterning film through the hard mask. However, as the hard mask thickness increases, electrons in the resist become more difficult to pass through and reach the patterning film. Therefore, increasing the thickness of the hard mask can lead to charging problems during electron beam patterning exposure. On the other hand, in recent years, multi-beam writers using multiple electron guns to pattern resists have been developed, and this problem becomes significant when using multi-beam writers for resist exposure. It should be noted that these problems also occur when tantalum oxide-based hard masks are used.

[0123] Therefore, to address the conductivity issue, a second hard mask (a transition metal-based hard mask) was considered, further deposited on a first hard mask (a silicon oxide-based or tantalum oxide-based hard mask). Generally, the thickness-to-width ratio of the resist pattern is preferably 1:2 or less. This is especially necessary for fine patterns with a linewidth of 20 nm to suppress resist pattern collapse. That is, the resist pattern thickness must be 40 nm or less. In dry etching using such a thin resist pattern as a mask, a faster etching rate is needed to form the pattern on the second hard mask. There is a tendency that the higher the transition metal content in the second hard mask, the lower the etching rate. Furthermore, there is a tendency that the higher the content of elements such as oxygen and nitrogen (which are gases at room temperature) in the second hard mask, the faster the etching rate. Adding these elements to reduce the transition metal content in the second hard mask, thereby increasing the etching rate, was considered. However, it was found that while reducing the amount of transition metal in the second hard mask film increased the etching rate, it also led to a decrease in conductivity. That is, it was found that although such a second hard mask film is not like the first hard mask film, its conductivity is significantly reduced compared to the thin film used for patterning, making it difficult for charged electrons on the resist film to escape sufficiently during electron beam exposure.

[0124] The inventors conducted in-depth research to solve these problems and conceived of electrically connecting the pattern-forming thin film to the second hard mask film.

[0125] That is, the mask blank of the present invention has a structure in which a pattern forming film, a first hard mask film, and a second hard mask film are sequentially stacked on the main surface of a substrate. The pattern forming film contains a transition metal, the first hard mask film contains oxygen and one or more elements selected from silicon and tantalum, the second hard mask film contains a transition metal, the content of the transition metal in the second hard mask film is less than the content of the transition metal in the pattern forming film, the area on the main surface where the first hard mask film is formed is smaller than the area where the pattern forming film is formed, and the second hard mask film is at least partially in contact with the pattern forming film.

[0126] <First Embodiment>

[0127] [Mask blanks and their manufacturing]

[0128] The embodiments will now be described with reference to the accompanying drawings.

[0129] Figure 1 This is a cross-sectional view showing the structure of the mask blank (binary mask blank) 10 according to the first embodiment of the present invention. Figure 1The mask blank 10 of the present invention shown has a structure in which a light-shielding film (pattern forming film) 2, a first hard mask film 3, a second hard mask film 4, and a resist film 5 are sequentially stacked on a substrate 1.

[0130] The substrate 1 can be formed of synthetic quartz glass, or it can be formed of quartz glass, aluminosilicate glass, soda-lime glass, low thermal expansion glass (SiO2-TiO2 glass, etc.). Among these, synthetic quartz glass is particularly preferred as a substrate material for forming the mask blank because it has high transmittance of ArF exposure light and sufficient rigidity to prevent deformation.

[0131] In this embodiment, a first hard mask film 3 and a second hard mask film 4 are stacked on the light-shielding film 2. The light-shielding film 2, the first hard mask film 3, and the second hard mask film 4 can be any structure, including single-layer structures and stacked structures with two or more layers. In addition, each layer of the single-layer structure or the stacked structure can be composed of substantially the same composition in the thickness direction of the film or layer, or it can be composed of a gradient in the thickness direction of the layers.

[0132] The light-shielding film 2 is a thin film used for pattern forming when a transfer pattern is formed during the manufacture of a binary mask from a mask blank. The binary mask requires high light-shielding performance for the pattern on the light-shielding film 2. It is required that the optical density (OD) of the light-shielding film 2 alone is 2.8 or higher, more preferably 3.0 or higher.

[0133] The light-shielding film 2 is formed from a material capable of patterning the transfer pattern using dry etching based on an etching gas containing chlorine. Materials containing transition metals are examples of materials possessing such properties. Examples of transition metals contained in the light-shielding film 2 include any one of molybdenum (Mo), tungsten (W), titanium (Ti), chromium (Cr), nickel (Ni), vanadium (V), zirconium (Zr), ruthenium (Ru), rhodium (Rh), niobium (Nb), palladium (Pd), or alloys of these metals.

[0134] The material forming the light-shielding film 2 may contain one or more elements selected from oxygen, nitrogen, carbon, boron, and hydrogen within a range that does not significantly reduce the optical density. To reduce the reflectivity of the surface of the light-shielding film 2 opposite to the substrate 1 for exposure light, it may contain a large amount of oxygen and nitrogen in the surface layer opposite to the substrate 1. The silicon content of the light-shielding film 2 is preferably 5 atomic percent or less, more preferably 3 atomic percent or less, and even more preferably the maximum peak of the narrow spectrum of Si2p obtained by X-ray photoelectron spectroscopy is below the detection limit. It should be noted that the light-shielding film 2 is formed by sputtering as described later. Therefore, the light-shielding film 2 may also contain rare gases such as argon (Ar), krypton (Kr), xenon (Xe), helium (He), and neon (Ne).

[0135] The light-shielding film 2 is particularly preferably formed of a chromium-containing material. Besides chromium metal, examples of chromium-containing materials for forming the light-shielding film 2 include materials containing one or more elements selected from oxygen (O), nitrogen (N), carbon (C), boron (B), and fluorine (F). Generally, chromium-based materials are etched using a mixture of chlorine and oxygen gases, but the etching rate of chromium metal relative to this etching gas is not very high. Considering the need to improve the etching rate relative to the chlorine-oxygen mixture etching gas, the material for forming the light-shielding film 2 is preferably a chromium-containing material containing one or more elements selected from oxygen, nitrogen, carbon, boron, and fluorine. Alternatively, the chromium-containing material for forming the light-shielding film 2 may contain one or more elements selected from molybdenum, indium, and tin. By containing one or more elements selected from molybdenum, indium, and tin, the etching rate relative to the chlorine-oxygen mixture can be further accelerated.

[0136] In order to form SRAF patterns with a linewidth of about 20 nm with high precision, the thickness of the light-shielding film 2 is preferably 60 nm or less, more preferably 50 nm or less. On the other hand, from the viewpoint of ensuring optical density and conductivity, the thickness of the light-shielding film 2 is preferably 30 nm or more.

[0137] The first hard mask 3 is formed of a material containing one or more elements selected from silicon and tantalum and oxygen, so as to have etching selectivity for the etching gas used when etching the light-shielding film 2.

[0138] As the material containing silicon and oxygen, SiO2, SiON, etc. are preferred. In this case, the total content of silicon and oxygen in the first hard mask film 3 is preferably 96 atomic% or more, more preferably 98 atomic% or more. In addition, the total content of silicon, nitrogen, and oxygen in the first hard mask film 3 is preferably 96 atomic% or more, more preferably 98 atomic% or more. It should be noted that the first hard mask film 3 formed from the material containing silicon and oxygen may contain a transition metal within a range that allows for sufficient etching selectivity between the light-shielding film 2 and the second hard mask film 4.

[0139] Furthermore, materials containing tantalum and oxygen can include those containing one or more elements selected from nitrogen, boron, and carbon in addition to tantalum and oxygen. Examples include TaO, TaON, TaBO, TaBON, TaCO, TaCON, and TaBOCN. In this case, for the first hard mask film 3, a material containing boron is preferred among these materials.

[0140] The total oxygen and nitrogen content of the first hard mask film 3 is preferably 50 atomic% or more, more preferably 55 atomic% or more, and even more preferably 60 atomic% or more. Furthermore, the oxygen content of the first hard mask film 3 is more preferably 50 atomic% or more, even more preferably 55 atomic% or more, and even more preferably 60 atomic% or more. This further improves the etch selectivity for etching gases when patterning the light-shielding film 2 and the second hard mask film 4. On the other hand, the high resistivity of the first hard mask film 3 makes it difficult for electrons irradiated onto the resist film to escape through the first hard mask film during electron beam-based patterning exposure.

[0141] The first hard mask 3 is preferably formed in an area smaller than the area where the light-shielding film 2 is formed when viewed from above (on the main surface of the substrate 1). This configuration facilitates at least partial contact between the light-shielding film 2 and the second hard mask 4. The first hard mask 3 only needs to be the size required to cover the pattern transfer area. For example, the first hard mask 3 is preferably formed to cover an area that includes at least a quadrilateral region with a side length of 132 mm based on the center of the substrate 11.

[0142] In order for the hard mask to function effectively in forming an SRAF pattern of approximately 20 nm on the light-shielding film 2, which serves as a patterning film, with high precision, the thickness of the first hard mask film 3 is preferably 7 nm or more, and more preferably 12 nm or more. On the other hand, in order to form an SRAF pattern of approximately 20 nm on the first hard mask film 3 with high precision by dry etching using the pattern of the relatively thin second hard mask film (described later) as a mask, the thickness of the first hard mask film 3 is preferably 20 nm or less, and more preferably 15 nm or less.

[0143] Furthermore, the film density of the first hard mask film 3 is preferably 1.5 g / cm³. 3 ~9.0g / cm 3 If the film density of the first hard mask film 3 is above the aforementioned lower limit, the resistance to physical etching during dry etching of the light-shielding film 2 is improved. Particularly when the first hard mask film 3 is formed of a material containing silicon and oxygen, its film density is preferably 1.5 g / cm³. 3 ~3.0g / cm 3 On the other hand, when the first hard mask film 3 is formed of a material containing tantalum and oxygen, its film density is preferably 7.5 g / cm³. 3 ~9.0g / cm 3 .

[0144] Furthermore, a second hard mask 4 is stacked on top of the first hard mask 3. The second hard mask 4 needs to have high etching selectivity for the etching gas used to pattern the first hard mask 3. From this viewpoint, the second hard mask 4 preferably contains a transition metal. Examples of transition metals contained in the second hard mask 4 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), or alloys of these metals. The second hard mask 4 is preferably formed of a material that can be patterned by dry etching using an etching gas containing chlorine. In addition, if the light-shielding film 2 and the second hard mask 4 contain the same transition metal, it is easier to perform etching by dry etching using the same etching gas, which is therefore preferred.

[0145] If the second hard mask film 4 contains at least any element of oxygen and nitrogen, it is preferable from the viewpoint of improving the etching rate, and more preferably it contains oxygen. Furthermore, in order to make the etching rate higher than that of the light-shielding film 2, it is preferable that the total oxygen and nitrogen content of the second hard mask film 4 is greater than that of the light-shielding film 2. For the same reason, it is preferable that the transition metal content of the second hard mask film 4 is less than that of the light-shielding film 2. In addition, the difference between the transition metal content of the light-shielding film 2 and the transition metal content of the second hard mask film 4 is preferably 10 atomic% or more, more preferably 15 atomic% or more. Based on this, the transition metal content of the second hard mask film 4 is preferably 60 atomic% or less, more preferably 55 atomic% or less.

[0146] Furthermore, in order to achieve a certain or higher etching rate for the second hard mask film 4, the total oxygen and nitrogen content of the second hard mask film 4 is preferably 30 atomic% or more, more preferably 32 atomic% or more. Additionally, the oxygen content of the second hard mask film 4 is preferably 20 atomic% or more.

[0147] The second hard mask film 4 is particularly preferably formed of a chromium-containing material. Besides chromium metal, other examples of chromium-containing materials for forming the second hard mask film 4 include materials containing one or more elements selected from oxygen (O), nitrogen (N), carbon (C), boron (B), and fluorine (F). Generally, chromium-based materials are etched using a mixture of chlorine and oxygen gases, but the etching rate of chromium metal relative to this etching gas is not very high. Considering the need to improve the etching rate relative to the chlorine-oxygen mixture etching gas, the material for forming the second hard mask film 4 is preferably a chromium-containing material containing one or more elements selected from oxygen, nitrogen, carbon, boron, and fluorine. Alternatively, the chromium-containing material for forming the second hard mask film 4 may contain one or more elements selected from molybdenum, indium, and tin. By containing one or more elements selected from molybdenum, indium, and tin, the etching rate relative to the chlorine-oxygen mixture can be further accelerated.

[0148] In order to form SRAF patterns of about 20 nm with high precision by using a resist pattern with a film thickness of 40 nm or less as a mask in dry etching, the film thickness of the second hard mask film 4 is preferably 5 nm or less, more preferably 4 nm or less. On the other hand, in order to make the pattern of the second hard mask film 4 function fully as a mask when the pattern is formed on the first hard mask film in dry etching, the film thickness of the second hard mask film 4 is preferably 2 nm or more.

[0149] Preferably, the area on the main surface of the substrate 1 where the second hard mask film 4 is formed is larger than the area where the first hard mask film 3 is formed. Therefore, as described above, since the area where the first hard mask film 3 is formed is smaller than the area where the light-shielding film 2 is formed, the second hard mask film 4 and the light-shielding film 2 can be formed in contact with each other outside the first hard mask film 3, thereby ensuring conductivity in this peripheral region. The second hard mask film 4 is preferably formed beyond the outer periphery of the area where the first hard mask film 3 is formed (i.e., the first hard mask film 3 is entirely covered by the second hard mask film 4). Alternatively, a portion of the second hard mask film 4 may be formed beyond the outer periphery of the area where the first hard mask film 3 is formed and in contact with the light-shielding film 2, while the remaining portion is formed in the same area as the area where the first hard mask film 3 is formed.

[0150] Furthermore, the film density of the second hard mask film 4 is preferably 3.5 g / cm³. 3 ~7.0g / cm 3 .

[0151] In the mask blank 10, it is preferable to form an organic resist film 5 with a thickness of 40 nm or less, which is in contact with the surface of the second hard mask film 4. In this way, even when drawing a transfer pattern containing fine auxiliary patterns of about 20 nm, the aspect ratio of the resist pattern can be reduced to more than 1:2. Therefore, it is possible to suppress the damage and detachment of the resist pattern during development, rinsing, etc. of the resist film 5.

[0152] The light-shielding film 2, the first hard mask film 3, and the second hard mask film 4 can be formed respectively by reactive sputtering. The sputtering method can be either DC sputtering (using a direct current (DC) power supply) or RF sputtering (using a high-frequency (RF) power supply). Alternatively, magnetron sputtering or a conventional method can be used. DC sputtering is preferred for its structural simplicity. Furthermore, magnetron sputtering is preferred for its faster film formation rate and improved productivity. It should be noted that the film formation apparatus can be either in-line or monolithic.

[0153] In addition, when a substrate 1 is arranged on a rotating stage in the film forming apparatus, and when forming the light-shielding film 2, the first hard mask film 3, and the second hard mask film 4, a mask is provided on the main surface of the substrate 1 and the opening area of ​​the mask is adjusted, so that the film forming area of ​​each film on the main surface of the substrate 1 can be adjusted to the desired area.

[0154] In addition, the resist film 5 is formed by spin coating.

[0155] Thus, referring to Figure 1 The structure of the mask blank 10 in this embodiment has been described, but it is not limited to this structure. For example, an antistatic layer (CDL: Charge Dissipation Layer) may be formed on the surface of the resist film 5. Alternatively, the mask blank may not have the resist film 5.

[0156] [Manufacturing method of transfer mask (binary mask)]

[0157] use Figure 3 A method for manufacturing a transfer mask (binary mask) using the mask blank 10 of the first embodiment will be described.

[0158] Using electron beams for Figure 1 The photoresist film 5 with a thickness of less than 40 nm, formed by spin coating in the mask blank 10 shown, is used to draw the first pattern to be formed on the light-shielding film 2. Further processing, such as development, is then performed to form a photoresist film (photoresist pattern) 5a with the first pattern (see reference). Figure 3(a)). In addition to the pattern transferred to the semiconductor device (the main pattern), the first pattern also includes an auxiliary pattern with a linewidth of about 20 nm.

[0159] At this point, in a given area where the second hard mask 4, which is closer to the outer edge than the first hard mask 3, contacts the light-shielding film 2, a grounding pin (not shown) is engaged to ensure grounding between the resist 5, the second hard mask 4, and the light-shielding film 2. Therefore, charging during electron beam drawing on the resist 5 can be suppressed, enabling exposure drawing with high positional accuracy.

[0160] Next, using the resist pattern 5a as a mask, the second hard mask film 4 is dry-etched using a mixture of chlorine and oxygen gases to form the second hard mask film (hard mask pattern) 4a with the first pattern (see reference). Figure 3 (b) Then, the resist pattern 5a is removed.

[0161] Next, using the second hard mask pattern 4a as a mask, the first hard mask film 3 is dry-etched using a fluorine-based gas to form a first hard mask film (first hard mask pattern) 3a with the first pattern (see reference). Figure 3 (b) Next, other resist films are formed by spin coating. Then, the resist film is laser-etched over the area where the first hard mask pattern 3a is formed, and further processed by given treatments such as development, thereby forming a resist film (resist pattern) 6b with the second pattern (see reference). Figure 3 (c) (It should be noted that at this stage, the light-shielding film 2 is as follows) Figure 3 (b) as shown in the image). Then, using the first hard mask pattern 3a and the resist pattern 6b as masks, the light-shielding film 2 is dry-etched using a mixture of chlorine gas and oxygen gas to form a light-shielding film (light-shielding pattern) 2a with the first pattern (see reference). Figure 3 (c)). At this point, the exposed portion of the second hard mask pattern 4a is removed by dry etching, becoming the second hard mask film (second hard mask pattern) 4b with the second pattern (see reference). Figure 3 (c)).

[0162] Then, using the resist pattern 6b and the second hard mask pattern 4b as masks, the first hard mask pattern 3a is dry-etched using a fluorine-based gas to remove it. The resist pattern 6b is then removed, followed by a cleaning process, thereby manufacturing a transfer mask (binary mask) 100 (see reference). Figure 3 (d)).

[0163] Semiconductor device manufacturing

[0164] The semiconductor device manufacturing method of the first embodiment uses the binary mask (transfer mask) 100 of the first embodiment or a binary mask 100 manufactured using the mask blank 10 of the first embodiment to expose and transfer a transfer pattern onto a resist film on a semiconductor substrate. Therefore, when the resist film transferred onto the semiconductor device is exposed using the binary mask 100 of the first embodiment, a pattern can be formed on the resist film on the semiconductor device with a precision that fully meets the design specifications.

[0165] <Second Implementation>

[0166] [Mask blanks and their manufacturing]

[0167] The mask blank of the second embodiment of the present invention has a phase-shifting film between the substrate and the light-shielding film, and the mask blank is used to manufacture a phase-shifting mask (a transfer mask). Figure 2 The structure of the mask blank according to the second embodiment is shown. The mask blank 20 of the second embodiment has a phase shift film 12, a light-shielding film (pattern forming film) 13, a first hard mask film 14, a second hard mask film 15, and a resist film 16 on the main surface of the substrate 11. The substrate 11 and the resist film 16 are the same as in the first embodiment, so their description is omitted.

[0168] The phase-shift film 12 is formed of a material capable of being patterned by dry etching using an etching gas containing fluorine, specifically, a silicon-containing material. The phase-shift film 12 preferably has the following functions: allowing exposure light to pass through with a transmittance of 1% or more (transmittance), and generating a phase difference of 150 degrees or more and 210 degrees or less between the exposure light that has passed through the phase-shift film and the exposure light that has passed through only a distance equal to the thickness of the phase-shift film. Furthermore, the transmittance of the phase-shift film 12 is more preferably 2% or more. The transmittance of the phase-shift film 12 is preferably 30% or less, more preferably 20% or less.

[0169] The phase-shifting film 12 is preferably formed of a material containing nitrogen (N) in addition to silicon. If the phase-shifting film 12 can be patterned using dry etching with a fluorine-based gas, it may further contain one or more elements selected from half-metallic elements, non-metallic elements, and metallic elements. The half-metallic element can be any half-metallic element other than silicon. The non-metallic element can be any non-metallic element other than nitrogen, and preferably contains one or more elements selected from oxygen (O), carbon (C), fluorine (F), and hydrogen (H). Examples of metallic elements include molybdenum (Mo), tungsten (W), titanium (Ti), tantalum (Ta), zirconium (Zr), hafnium (Hf), niobium (Nb), vanadium (V), cobalt (Co), chromium (Cr), nickel (Ni), ruthenium (Ru), tin (Sn), boron (B), and germanium (Ge).

[0170] The thickness of the phase-shifting film 12 is preferably 80 nm or less, more preferably 70 nm or less. The thickness of the phase-shifting film 12 is preferably 50 nm or more. This is because, in order to form the phase-shifting film 12 with an amorphous material and to achieve a phase difference of 150 degrees or more in the phase-shifting film 12, the thickness of the phase-shifting film 12 needs to be 50 nm or more. It should be noted that the phase-shifting film 12 can be any structure, including a single-layer structure and a stacked structure with two or more layers. Furthermore, the layers in the single-layer structure or the stacked structure can have substantially the same composition in the thickness direction of the film or layer, or they can have a compositional gradient in the thickness direction of the layers.

[0171] Furthermore, the phase-shifting film 12 is preferably formed in an area smaller than the area where the light-shielding film 13 is formed when viewed from above (on the main surface of the substrate 1). It is required that the area where the phase-shifting film 12 is formed is at least the size including the pattern transfer area. For example, the phase-shifting film 12 is preferably formed covering an area that includes at least a quadrilateral region with a side length of 132 mm based on the center of the main surface of the substrate 11.

[0172] To satisfy the conditions related to the aforementioned optical properties and film thickness in the phase-shift film 12, the refractive index n of the phase-shift film for exposure light (ArF exposure light) is preferably 1.9 or higher, more preferably 2.0 or higher. Furthermore, the refractive index n of the phase-shift film 12 is preferably 3.1 or lower, more preferably 2.7 or lower. The extinction coefficient k of the phase-shift film 12 for ArF exposure light is preferably 0.26 or higher, more preferably 0.29 or higher. Furthermore, the extinction coefficient k of the phase-shift film 12 is preferably 0.62 or lower, more preferably 0.54 or lower.

[0173] It should be noted that the refractive index n and extinction coefficient k of the thin film containing the phase-shift film 12 are not solely determined by its composition. The film density, crystallization state, and other factors also influence the refractive index n and extinction coefficient k. Therefore, adjusting the conditions during reactive sputtering film formation is necessary to achieve the desired refractive index n and extinction coefficient k. While adjusting the ratio of the rare gas to the reactive gas (oxygen, nitrogen, etc.) mixture during reactive sputtering is effective in achieving the aforementioned range of refractive index n and extinction coefficient k for the phase-shift film 12, it is not limited to this. Other factors include the pressure within the film formation chamber, the electrical current applied to the sputtering target, and the positional relationship between the target and the substrate 11. Furthermore, these film formation conditions are inherent to the film formation apparatus and can be appropriately adjusted to ensure that the formed phase-shift film 12 achieves the desired refractive index n and extinction coefficient k.

[0174] The mask blank 20 has a light-shielding film 13 on the phase-shifting film 12. For the light-shielding film 13 in this configuration, it is necessary to use a material that has sufficient etching selectivity for the etching gas used when patterning the phase-shifting film 12.

[0175] In this case, the light-shielding film 13 can also be the same as the light-shielding film 2 described in the first embodiment above. However, as will be explained later, in the case of the light-shielding film 13 disposed on the phase-shifting film 12, an OD (exposure) similar to that of the light-shielding film 2 used for binary masks is not required. Therefore, the film thickness of the light-shielding film 13 is preferably 50 nm or less, more preferably 45 nm or less. On the other hand, from the viewpoint of ensuring optical density and conductivity, the film thickness of the light-shielding film 13 is preferably 20 nm or more.

[0176] After the phase-shift mask is completed, the light-shielding film 13 forms a light-shielding band or the like in a stacked structure with the phase-shift film 12. Therefore, it is required that the light-shielding film 13 ensures an optical density (OD) greater than 2.0 in the stacked structure with the phase-shift film 12, preferably having an OD of 2.8 or more, and more preferably having an OD of 3.0 or more.

[0177] A first hard mask 14 is formed on the light-shielding film 13. In order to have etching selectivity for the etching gas used to etch the light-shielding film 13, the first hard mask 14 is formed of a material containing oxygen and one or more elements selected from silicon and tantalum. The specific material and film thickness are the same as those of the first hard mask 3 in the first embodiment.

[0178] Furthermore, the first hard mask 14 is preferably formed in an area smaller than the area where the light-shielding film 13 is formed when viewed from above (on the main surface of the substrate 1). This configuration facilitates at least partial contact between the light-shielding film 13 and the second hard mask 15. The first hard mask 14 only needs to be the size required to cover the pattern transfer area where the phase-shifting film 12 is formed. For example, the first hard mask 14 is preferably formed to cover an area that includes at least a quadrilateral region with a side length of 132 mm, referenced to the center of the main surface of the substrate 11.

[0179] Furthermore, a second hard mask 15 is stacked on the first hard mask 14. The second hard mask 15 needs to have high etch selectivity for the etch gas used to pattern the first hard mask 14. From this point of view, the second hard mask 15 preferably contains a transition metal. The specific material and film thickness are the same as those of the second hard mask 4 in the first embodiment.

[0180] Furthermore, the area on the main surface of the substrate 11 where the second hard mask film 15 is formed is preferably larger than the area where the first hard mask film 14 is formed. Therefore, as described above, since the area where the first hard mask film 14 is formed is smaller than the area where the light-shielding film 13 is formed, the second hard mask film 15 and the light-shielding film 13 can be formed in such a way that the second hard mask film 15 and the light-shielding film 13 are in contact with each other on the outer side of the first hard mask film 14, thereby ensuring conductivity in this peripheral region.

[0181] The second hard mask 15 is preferably formed in a region extending beyond the outer periphery of the region where the first hard mask 14 is formed (i.e., the first hard mask 14 is entirely covered by the second hard mask 15). Alternatively, a portion of the second hard mask 15 may be formed in a region extending beyond the outer periphery of the region where the first hard mask 14 is formed and adjoining the light-shielding film 13, while the remaining portion may be formed in the same region as the region where the first hard mask 14 is formed.

[0182] Similar to the first embodiment, the phase-shifting film 12, the light-shielding film 13, the first hard mask film 14, and the second hard mask film 15 can be formed by using reactive sputtering.

[0183] In addition, when forming the phase-shifting film 12, the light-shielding film 13, the first hard mask film 14, and the second hard mask film 15, the film-forming area of ​​each film can be adjusted to the desired area by adjusting the opening area of ​​the mask.

[0184] In addition, the resist film 16 is formed by spin coating.

[0185] [Manufacturing method of transfer mask (phase shift mask)]

[0186] use Figure 4 A method for manufacturing a transfer mask (phase-shifting mask) using the mask blank 20 of the second embodiment will be described.

[0187] Using electron beams to Figure 2 The photoresist film 16 with a thickness of less than 40 nm, formed by spin coating in the mask blank 20 shown, is used to draw the first pattern to be formed on the phase shift film 12. Further processing, such as development, is then performed to form a photoresist film (photoresist pattern) 16a with the first pattern (see reference). Figure 4 (a)). In addition to the pattern transferred to the semiconductor device (main pattern), the first pattern also includes an auxiliary pattern with a linewidth of about 20 nm.

[0188] At this time, in a given area where the second hard mask 15, which is closer to the outer edge than the first hard mask 14, contacts the light-shielding film 13, a grounding pin (not shown) is contacted, ensuring grounding between the resist film 16, the second hard mask 15, and the light-shielding film 13. Therefore, charging during electron beam drawing on the resist film 16 can be suppressed, enabling high-precision exposure drawing (it should be noted that charging can also be suppressed during the formation of the resist patterns 17b and 18c described later, enabling high-precision exposure drawing).

[0189] Next, using the resist pattern 16a as a mask, the second hard mask film 15 is dry-etched using a mixed gas of chlorine and oxygen to form a second hard mask film (hard mask pattern) 15a with the first pattern (see reference). Figure 4 (b) Then, the resist pattern 16a is removed.

[0190] Next, using the second hard mask pattern 15a as a mask, the first hard mask film 14 is dry-etched using a fluorine-based gas to form a first hard mask film (first hard mask pattern) 14a with the first pattern (see reference). Figure 4 (b) Next, other resist films are formed by spin coating. Then, the resist film is laser-etched over the area where the first hard mask pattern 14a is formed, and further processed by given treatments such as development, thereby forming a resist film (resist pattern) 17b with a second pattern (see reference). Figure 4 (c) (It should be noted that at this stage, the light-shielding film 13 and the second hard mask pattern 15a are as follows) Figure 4 (b) as shown in the image). Then, using the first hard mask pattern 14a and the resist pattern 17b as masks, the light-shielding film 13 is dry-etched using a mixture of chlorine gas and oxygen gas to form a light-shielding film (light-shielding pattern) 13a with the first pattern (see reference). Figure 4 (c)). At this point, the exposed portion of the second hard mask pattern 15a is removed by dry etching, resulting in a second hard mask film (second hard mask pattern) 15b with the second pattern (see reference). Figure 4 (c)).

[0191] Then, using the light-shielding pattern 13a as a mask, the phase-shifting film 12 is dry-etched using a fluorine-based gas to form a phase-shifting film (phase-shifting pattern) 12a with the first pattern (see reference). Figure 4 (d)). At this point, the first hard mask pattern 14a is removed (see reference). Figure 4 (d)).

[0192] Then, the resist pattern 17b is removed, a cleaning process is performed, and other resist films are formed by spin coating. Next, an electron beam is used to draw the third pattern to be formed on the resist film in the light-shielding film 13, followed by further processing such as development, thereby forming a resist film (resist pattern) 18c with the third pattern (see reference). Figure 4 (e)). Then, using the resist pattern 18c as a mask, the light-shielding film 13 is dry-etched using a mixture of chlorine and oxygen gas to form a light-shielding film (light-shielding pattern) 13c with the third pattern. Then, the resist pattern 18c is removed and a cleaning process is performed, thereby manufacturing a transfer mask (phase-shifting mask) 200 (see reference). Figure 4 (f)).

[0193] Semiconductor device manufacturing

[0194] The semiconductor device manufacturing method of the second embodiment uses the phase shift mask 200 of the second embodiment or a phase shift mask 200 manufactured using the mask blank 20 of the second embodiment to expose and transfer a transfer pattern onto a resist film on a semiconductor substrate. Therefore, when exposing and transferring the resist film onto the semiconductor device using the phase shift mask 200 of the second embodiment, a pattern can be formed on the resist film on the semiconductor device with a precision that fully meets the design specifications.

[0195] It should be noted that the mask blank of the present invention can be a reflective mask blank used in manufacturing reflective masks for EUV flatbed printing (Extreme Ultraviolet Lithography). In this case, it is preferable to form the absorber film from the above-described pattern-forming thin film.

[0196] In the case of this reflective mask blank, the substrate is preferably made of low thermal expansion glass (such as SiO2-TiO2 glass). Furthermore, it is preferable to have a configuration in which multiple layers of reflective film, protective film, absorber film (patterning film), first hard mask film, and second hard mask film are sequentially stacked on the substrate. The configuration of the absorber film, first hard mask film, and second hard mask film is preferably the same as that shown in the embodiments described above. The absorber film is preferably formed from the aforementioned chromium-containing material. On the other hand, the absorber film may also be made of a ruthenium-containing material. As a ruthenium-containing material in this case, in addition to elemental ruthenium, materials containing at least any element of nitrogen or oxygen in ruthenium can also be cited.

[0197] A multilayer reflective film is a film in a reflective mask that imparts the function of reflecting EUV light. A multilayer reflective film is a multilayer film composed of layers periodically stacked with elements of different refractive indices as the main components. Generally, as a multilayer reflective film, a multilayer film can be formed by alternating layers of thin films of light elements or their compounds as high-refractive-index materials (high-refractive-index layers) and thin films of heavy elements or their compounds as low-refractive-index materials (low-refractive-index layers) for about 40 to 60 cycles (pairs).

[0198] As a high refractive index layer, a material containing silicon (Si) can be used, for example. Besides elemental silicon, silicon compounds containing at least one element selected from boron (B), carbon (C), zirconium (Zr), nitrogen (N), and oxygen (O) can also be used as the silicon-containing material. As a low refractive index layer, at least one elemental metal selected from molybdenum (Mo), ruthenium (Ru), rhodium (Rh), and platinum (Pt), or alloys thereof, can be used, for example. As a multilayer reflective film for reflecting, for example, EUV light with wavelengths of 13 nm to 14 nm, a Mo / Si periodic laminated film formed by alternating layers of Mo and Si for approximately 40 to 60 cycles is preferred.

[0199] The protective film can be made of silicon-based materials, such as those containing silicon (Si), silicon (Si) and oxygen (O), silicon (Si) and nitrogen (N), or silicon (Si), oxygen (O), and nitrogen (N). Alternatively, when the absorber film is formed of a ruthenium-containing material, the protective film can be made of a chromium-based material selected from chromium (Cr), or a chromium-based material containing at least one of chromium (Cr) and oxygen (O), nitrogen (N), and carbon (C). On the other hand, depending on the material constituting the absorber film, the protective film can be made of a ruthenium-containing material. Examples of ruthenium-containing materials include elemental Ru, Ru alloys containing at least one metal selected from titanium (Ti), niobium (Nb), molybdenum (Mo), zirconium (Zr), yttrium (Y), boron (B), lanthanum (La), cobalt (Co), rhenium (Re), and rhodium (Rh), and materials containing nitrogen.

[0200] Example

[0201] The embodiments of the present invention will be described in more detail below through examples.

[0202] [Mask blank manufacturing]

[0203] Reference Figure 2A substrate 11 made of synthetic quartz glass with a main surface size of approximately 152 mm × approximately 152 mm and a thickness of approximately 6.35 mm was prepared. The main surface of the substrate 11 was ground to a given surface roughness (less than 0.2 nm in terms of Rq), and then a given cleaning and drying process was performed.

[0204] Next, a substrate 11 was placed in a monolithic DC sputtering apparatus, and a phase-shifting film 12 comprising molybdenum, silicon, and nitrogen was formed on the substrate 11 with a thickness of 69 nm using a mixed sintered target of molybdenum (Mo) and silicon (Si) (Mo:Si = 11 atomic%: 89 atomic%) through reactive sputtering (DC sputtering) using a mixed gas of argon (Ar), nitrogen (N2), and helium (He) as the sputtering gas. A shielding plate was used during the sputtering of this phase-shifting film 12. The shielding plate used had a square opening with a side length of 146 mm relative to the center of the substrate (i.e., the design area was a square area with a side length of 146 mm).

[0205] Next, the substrate 11 on which the phase-shifting film 12 is formed was subjected to a heat treatment to reduce the film stress of the phase-shifting film 12 and to form an oxide layer on the surface. Specifically, the heat treatment was performed in the atmosphere using a heating furnace (electric furnace), with the heating temperature set to 450°C and the heating time set to 1 hour. The transmittance and phase difference of the phase-shifting film 12 after the heat treatment for light with a wavelength of 193 nm were measured using a phase shift measurement device (Lasertec MPM193). The transmittance was 6.0% and the phase difference was 177.0 degrees (°).

[0206] Next, a substrate 11 with a phase-shifting film 12 formed thereon was placed in a monolithic DC sputtering apparatus, and reactive sputtering (DC sputtering) was performed in a mixed gas atmosphere of argon (Ar), carbon dioxide (CO2), and helium (He) using a chromium (Cr) target. As a result, a light-shielding film (CrOC film, Cr:O:C = 70.4 atomic%: 15.4 atomic%: 14.2 atomic%) 13 containing chromium, oxygen, and carbon was formed in contact with the phase-shifting film 12 with a film thickness of 36 nm. A shielding plate was also used during the sputtering of this light-shielding film 13. The shielding plate used here has a square opening 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 side length of the main surface of the substrate 11 is 151.2 mm, and the margin between the design areas is quite small.

[0207] Next, the substrate 11 with the light-shielding film (CrOC film) 13 formed thereon was subjected to heat treatment. Specifically, a hot plate was used, the heating temperature was set to 280°C, and the heating time was set to 5 minutes, and the heat treatment was performed in the atmosphere. After the heat treatment, the optical density of the stacked structure of the phase-shifting film 12 and the light-shielding film 13 was measured at the wavelength (approximately 193 nm) of ArF excimer laser light using a spectrophotometer (Cary4000 manufactured by Agilent Technologies), and the result was confirmed to be 3.0 or higher.

[0208] Next, a first hard mask film 14 (SiO2 film, Si:O = 33.8 atomic%: 66.2 atomic%) was formed on the light-shielding film 13 with a thickness of 12 nm. Specifically, a substrate 11 with a phase-shifting film 12 and a light-shielding film 13 stacked on it was disposed in a monolithic DC sputtering apparatus. Using a silicon (Si) target, argon (Ar) gas and oxygen (O2) gas were used as sputtering gases, and the first hard mask film 14 was formed by DC sputtering. A shielding plate was used during the sputtering of the first hard mask film 14. The shielding plate used had a square opening with a side length of 146 mm based on the center of the substrate (i.e., the design area is a square area with a side length of 146 mm).

[0209] A first hard mask film 14 with a thickness of 12 nm was formed on other substrates, and the film density was measured to be 1.8 g / cm³. 3 In addition, the resistance of the plate was measured, and the result was 40kΩ.

[0210] Next, a second hard mask 15 (CrOCN film, Cr: 54.7 atomic%, O: 22.2 atomic%, C: 11.9 atomic%, N: 11.2 atomic%) was formed on the first hard mask 14 with a thickness of 3 nm. Specifically, a substrate 11 with a phase-shifting film 12, a light-shielding film 13, and the first hard mask 14 stacked was disposed in a monolithic DC sputtering apparatus, and reactive sputtering (DC sputtering) was performed using a chromium (Cr) target in a mixed gas atmosphere of argon (Ar), carbon dioxide (CO2), nitrogen (N2), and helium (He). A shielding plate was used during the sputtering of the second hard mask 15. The shielding plate used had a square opening with a side length of 148 mm based on the center of the substrate (i.e., the design area was a square area with a side length of 148 mm).

[0211] A second hard mask film with a thickness of 3 nm was formed on another substrate, and the film density was measured to be 4.9 g / cm³. 3 In addition, the resistance of the plate was measured, and the result was 200kΩ.

[0212] Then, after performing the given cleaning process, a resist film 16 with a film thickness of 40 nm was formed by spin coating, thus manufacturing the mask blank 20 of Example 1.

[0213] Manufacturing of transfer masks (phase-shifting masks)

[0214] Next, using the mask blank 20 of Example 1, utilizing... Figure 4 The halftone phase shift mask 200 of Example 1 was manufactured in the order described above.

[0215] More specifically, the second hard mask pattern 15a was fabricated using a mixture of chlorine (Cl2) and oxygen (O2) gas (gas flow ratio Cl2:O2 = 15:1) during the etching of the second hard mask 15 (see reference). Figure 4 (b)).

[0216] In addition, the first hard mask pattern 14a was fabricated using CF4 gas as a fluorine-based gas during the etching of the first hard mask film 14 (see reference). Figure 4 (b)).

[0217] In addition, the light-shielding film 13 was etched using a mixture of chlorine (Cl2) and oxygen (O2) gas (gas flow ratio Cl2:O2 = 15:1) to create light-shielding patterns 13a and 13c (see reference). Figure 4 (c) Figure 4 (d)).

[0218] Furthermore, the etching of the phase-shifting film 12 was performed using SF4 gas, a fluorine-based gas, to create the phase-shifting pattern 12a (see reference). Figure 4 (b)).

[0219] Furthermore, in the aforementioned series of processes, during electron beam drawing, a multi-beam writer equipped with two electron guns is used to contact a grounding pin (not shown) in a given area where the second hard mask 15, which is closer to the outer edge of the first hard mask 14, contacts the light-shielding film 13. This allows electron beams to be drawn onto each resist film at desired locations, thereby forming the desired resist patterns 16a, 17b, and 18c. The resist pattern 16a, in addition to the main pattern for transfer, also includes a fine SRAF pattern with a linewidth of 20 nm.

[0220] For the phase-shifting mask 200 of Example 1, the length of the pattern was measured using a length-measuring SEM (CD-SEM: Critical Dimension-Scanning Electron Microscope) centered on the area where the SRAF pattern with a linewidth of 20 nm was formed. The results confirmed that not only the main pattern for transfer, but also the fine SRAF pattern with a linewidth of 20 nm formed a phase-shifting pattern with good LER.

[0221] For the phase shift mask 200 fabricated in the above order, a simulation of the transfer image when exposing the resist film transferred to the semiconductor device using exposure light with a wavelength of 193 nm was performed using an AIMS193 (manufactured by Carl Zeiss). The simulated exposure transfer image was verified, and the results fully met the design specifications. Based on these results, it can be concluded that even if the phase shift mask 200 of this embodiment 1 is placed on the mask stage of the exposure apparatus and the resist film transferred to the semiconductor device is exposed, a circuit pattern can ultimately be formed on the semiconductor device with high precision.

[0222] (Comparative Example 1)

[0223] [Mask blank manufacturing]

[0224] The mask blank of Comparative Example 1 was manufactured in the same order as in Example 1, except for the hard mask film. For the hard mask film of Comparative Example 1, the second hard mask film 15 of Example 1 was not formed, and a film of the same material as the first hard mask film 14 (SiO2 film, Si:O = 34 atomic%: 66 atomic%) was formed with a thickness of 12 nm. Then, after treating the surface of this hard mask film with HMDS (hexamethyldisilazane), a 40 nm resist film was formed by spin coating.

[0225] Manufacturing of transfer masks (phase-shifting masks)

[0226] Next, using the mask blank from Comparative Example 1, the fabrication of a halftone phase-shift mask was attempted.

[0227] The resist film formed on the mask blank of Comparative Example 1 was patterned using an electron beam in the same order as in Example 1. At this time, a grounding pin was contacted in a given area where the hard mask film of Comparative Example 1 contacts the light-shielding film. However, during the formation of the resist pattern, charging occurred, making it impossible to pattern the desired pattern.

[0228] (Comparative Example 2)

[0229] [Mask blank manufacturing]

[0230] The mask blank of Comparative Example 2 was manufactured in the same order as in Example 1, except that the hard mask film was not used. For the hard mask film of Comparative Example 2, only the composition of the second hard mask film 15 was changed from that of Example 1. Specifically, under the same film-forming conditions as the light-shielding film, the second hard mask film was formed into a film containing chromium, oxygen, and carbon (CrOC film, Cr:O:C = 70.4 atomic%: 15.4 atomic%: 14.2 atomic%) with a film thickness of 3 nm. Then, a 40 nm resist film was formed on the hard mask film by spin coating.

[0231] Manufacturing of transfer masks (phase-shifting masks)

[0232] Next, using the mask blank from Comparative Example 2, a halftone phase-shift mask was manufactured. The manufacturing process of the phase-shift mask was the same as that described in Example 1.

[0233] When the resist film formed on the mask blank of Comparative Example 2 was drawn using an electron beam, a grounding pin was contacted in a given area where the second hard mask film of Comparative Example 2 was in contact with the light-shielding film.

[0234] In this way, the phase shift mask of Comparative Example 2 was manufactured in the same manner as in Example 1.

[0235] For the phase-shift mask of Comparative Example 2, the pattern length was measured using a length-measuring SEM (CD-SEM: Critical Dimension-Scanning Electron Microscope) centered on the area where the SRAF pattern with a linewidth of 20 nm was formed. The results showed that several areas where the main transfer pattern and the fine SRAF pattern with a linewidth of 20 nm failed to form a pattern were observed. It is speculated that this is because when the second hard mask film was patterned using dry etching with a 40 nm thick resist pattern as a mask, the etching rate of the second hard mask film was slow, and the resist pattern disappeared before the pattern formation on the second hard mask film was completed.

Claims

1. A mask blank having the following structure: a pattern forming film, a first hard mask film, and a second hard mask film are sequentially stacked on the main surface of a substrate. The thin film used for pattern formation contains a transition metal. The first hard mask film contains oxygen and one or more elements selected from silicon and tantalum. The second hard mask contains a transition metal. The second hard mask film has a lower content of transition metal than the pattern-forming thin film. The area on the main surface where the first hard mask film is formed is smaller than the area where the pattern-forming film is formed. The second hard mask film is at least partially in contact with the pattern forming film.

2. The mask blank according to claim 1, wherein, The combined oxygen and nitrogen content of the second hard mask film is greater than the combined oxygen and nitrogen content of the pattern forming film.

3. The mask blank according to claim 1, wherein, The area on the main surface where the second hard mask is formed is larger than the area where the first hard mask is formed.

4. The mask blank according to claim 1, wherein, The difference between the transition metal content of the thin film used for pattern formation and the transition metal content of the second hard mask film is 10 atomic% or more.

5. The mask blank according to claim 1, wherein, The combined oxygen and nitrogen content of the second hard mask film is 30 atomic percent or more.

6. The mask blank according to claim 1, wherein, The thickness of the second hard mask film is less than 5 nm.

7. The mask blank according to claim 1, wherein, The total oxygen and nitrogen content of the first hard mask film is 50 atomic percent or more.

8. The mask blank according to claim 1, wherein, The oxygen content of the first hard mask film is 50 atomic percent or more.

9. The mask blank according to claim 1, wherein, The thickness of the first hard mask film is 7 nm or more.

10. The mask blank according to claim 1, wherein, The thickness of the thin film used for pattern formation is less than 60 nm.

11. The mask blank according to any one of claims 1 to 10, wherein, The thin film used for pattern formation is a light-shielding film, and a phase-shifting film is provided between the substrate and the light-shielding film.

12. The mask blank according to claim 11, wherein, The phase-shifting film contains silicon.

13. The mask blank according to claim 11, wherein, The phase-shifting membrane has the following functions: The function of allowing exposure light to pass through with a transmittance of more than 1%, and This function enables a phase difference of 150 degrees or more and 210 degrees between the exposure light that has passed through the phase shift film and the exposure light that has passed through only the same distance as the thickness of the phase shift film in the air.

14. A method for manufacturing a transfer mask, comprising the following steps: (The method is described in the original text, but the provided excerpt ends here.) The process of forming a transfer pattern on the second hard mask film using a resist film with a transfer pattern formed on the second hard mask film as a mask by dry etching with an oxygen-containing chlorine gas. Using the second hard mask film with the transfer pattern formed thereon as a mask, a process is performed to form the transfer pattern on the first hard mask film by dry etching with fluorine-based gases; and Using the first hard mask film with the transfer pattern formed thereon as a mask, the transfer pattern is formed in the process of forming the thin film for pattern formation by dry etching with an oxygen-containing chlorine gas.

15. A method for manufacturing a transfer mask, comprising the following steps: (The method is described in the original text, but the provided text is incomplete and cannot be accurately translated without further context.) The process of forming a transfer pattern on the second hard mask film using a resist film with a transfer pattern formed on the second hard mask film as a mask by dry etching with an oxygen-containing chlorine gas. The process of forming a transfer pattern on the first hard mask film by using the second hard mask film with the transfer pattern formed thereon as a mask and dry etching with fluorine gas. Using the first hard mask film with the transfer pattern formed thereon as a mask, a process is performed to form the transfer pattern on the light-shielding film by dry etching with an oxygen-chlorine gas; and The process involves using the light-shielding film with the transfer pattern formed thereon as a mask, and then dry etching the phase-shifting film with fluorine gas to form the transfer pattern.

16. A method for manufacturing a semiconductor device, the method comprising the following steps: Using a transfer mask manufactured by the method for manufacturing a transfer mask according to claim 14 or 15, a transfer pattern is exposed and transferred to a resist film on a semiconductor substrate.

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