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

Abstract

The purpose of this invention is to provide a mask substrate that can accurately produce a transfer mask with an auxiliary pattern of a tiny size of about 20 nm. A masking substrate has a structure in which a pattern forming film, a first hard masking film, and a second hard masking film are sequentially deposited on the main surface of a substrate; the pattern forming film contains a transition metal; the first hard masking film contains one or more elements selected from silicon and tantalum and oxygen; the second hard masking film contains a transition metal; the content of the transition metal in the second hard masking film is less than the content of the transition metal in the pattern forming film; on the main surface, the area where the first hard masking film is formed is smaller than the area where the pattern forming film is formed; the second hard masking film and the pattern forming film are at least partially connected.

Description

Technical Field

[0001] This invention relates to a mask substrate, a method for manufacturing a mask for transfer printing, and a method for manufacturing a semiconductor device. Prior Technology

[0002] Generally, photolithography is used to form fine patterns in the manufacturing process of semiconductor devices. This formation typically involves multiple substrates called transfer masks. When miniaturizing the patterns on the semiconductor devices, in addition to miniaturizing the mask patterns formed on the transfer masks, the wavelength of the exposure light source used in photolithography must also be shortened. In recent years, the wavelengths of the exposure light sources used in semiconductor device manufacturing have evolved from KrF excimer lasers (wavelength 248 nm) to ArF excimer lasers (wavelength 193 nm), becoming increasingly shorter.

[0003] In addition to binary masks with a light-blocking pattern made of chromium-based materials on a conventional light-transmitting substrate, a type of halftone phase-shifting mask is known for transfer printing. This halftone phase-shifting mask consists of a portion (transparent portion) that allows light of a substantially high intensity to pass through (transparent portion) and a portion (semi-transparent portion) that allows light of a substantially low intensity to pass through (semi-transparent portion) forming the mask pattern on the transparent substrate. Furthermore, the phase shift of the light passing through the semi-transparent portion results in a relationship where the phase of the light passing through the semi-transparent portion is substantially reversed relative to the phase of the light passing through the transparent portion. This allows the light near the boundary between the transparent and semi-transparent portions to cancel each other out, thus maintaining good contrast at the boundary.

[0004] As a masking substrate for a halftone phase-shift mask, a masking substrate with the following structure is known in the past, which is composed of a halftone phase-shift film constituting a semi-transparent portion, a light-shielding film, and an etched masking film (hard masking film) made of inorganic materials.

[0005] Furthermore, in binary masks, there is a known mask substrate with the following structure: an etched mask film (hard mask film) is deposited on a light-shielding film.

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

[0007] Furthermore, Patent Document 2 discloses a method for manufacturing a mask substrate. The mask substrate is an electronic line drawing mask substrate for forming resist patterns by electronic line drawing. A light-shielding film and an etching mask film made of an inorganic material that is resistant to etching of the light-shielding film are sequentially formed on a transparent substrate. When the etching mask film is formed, a shielding plate is used to shield it so that the film is not formed on at least one side of the substrate.

[0008] [Previous Technical Documents]

[0009] [Patent Literature]

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

[0011] Patent Document 2: Japanese Patent No. 5393972

[0012] In photolithography, the minimum 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 numerical aperture (NA) of the lens in the projection optical system. Therefore, with the requirement for miniaturization of semiconductor components, although the wavelength of exposure light has been shortened and the NA of the projection optical system has been increased, it has reached its limit to meet this requirement by relying solely on shorter wavelengths and higher NA.

[0013] Therefore, in order to improve resolution, a super-resolution technique has been proposed in recent years to achieve miniaturization by reducing the value of the process constant k1 (k1 = resolution linewidth × numerical aperture of the projection optics system / wavelength of the exposure light). As one of the aforementioned super-resolution techniques, there is a method that applies auxiliary patterns or linewidth offsets to the mask pattern according to the characteristics of the exposure optical system to optimize the mask pattern.

[0014] The method of using an auxiliary pattern is a photolithography method using a transfer mask. This transfer mask places a pattern (hereinafter referred to as the auxiliary pattern) that is below the resolution limit of the projection optics system and is not transferred onto the wafer, near the pattern transferred onto the wafer (hereinafter referred to as the main pattern), thereby improving the resolution and depth of focus of the main pattern. The auxiliary pattern is also called a SRAF (Sub Resolution Assist Feature) (hereinafter, in this invention, the auxiliary pattern is also referred to as SRAF).

[0015] However, with the miniaturization of semiconductor device patterns, some difficulties have arisen in the fabrication of transfer masks with auxiliary patterns. Firstly, for example, the auxiliary patterns must, as mentioned above, not be imaged on the wafer itself, and must be much smaller than the main pattern. As a result, with the miniaturization of the main pattern size, the required linewidth of the auxiliary patterns has become increasingly smaller, ranging from hundreds of nm to around 40 nm, or even around 20 nm.

[0016] However, traditional mask substrates have been shown to be difficult to use for transfer masks with auxiliary patterns of a tiny size of around 20nm. Summary of the Invention

[0017] This invention addresses past problems and aims to provide a mask substrate capable of accurately fabricating transfer masks, wherein the transfer mask has auxiliary patterns of approximately 20 nm in size. Furthermore, this invention provides a method for manufacturing a transfer mask using this mask substrate to accurately form fine patterns on a pattern-forming thin film. Finally, this invention aims to provide a method for manufacturing a semiconductor device using a transfer mask manufactured according to the above-described method.

[0018] To achieve the above-mentioned objectives, the present invention has the following structure.

[0019] (Component 1)

[0020] A masking substrate has a structure in which a pattern forming film, a first hard masking film, and a second hard masking film are sequentially deposited on the main surface of a substrate;

[0021] The thin film used to form the pattern contains a transition metal.

[0022] The first hard masking film contains one or more elements selected from silicon and tantalum, and oxygen;

[0023] The second hard masking film contains a transition metal;

[0024] The transition metal content of the second hard mask film is less than that of the transition metal content of the pattern forming film;

[0025] On the main surface, the area where the first hard mask film is formed is smaller than the area where the pattern forming film is formed;

[0026] The second hard mask film is attached to the pattern forming film by at least a portion.

[0027] (Component 2)

[0028] If the masking substrate constitutes 1, the total oxygen and nitrogen content of the second hard masking film is greater than the total oxygen and nitrogen content of the pattern forming film.

[0029] (Component 3)

[0030] If a masking substrate constitutes 1 or 2, wherein on the main surface, the area where the second hard masking film is formed is larger than the area where the first hard masking film is formed.

[0031] (Component 4)

[0032] If any of the masking substrates 1 to 3 are formed, the difference between the content of the transition metal in the pattern forming film and the content of the transition metal in the second hard masking film is 10 atomic% or more.

[0033] (Component 5)

[0034] If any of the masking substrates 1 to 4 are formed, wherein the total oxygen and nitrogen content of the second hard masking film is 30 atomic% or more.

[0035] (Composition 6)

[0036] If any of the masking substrates 1 to 5 are formed, wherein the thickness of the second hard masking film is less than 5 nm.

[0037] (Component 7)

[0038] If any of the masking substrates 1 to 6 are formed, wherein the total oxygen and nitrogen content of the first hard masking film is 50 atomic% or more.

[0039] (Composition 8)

[0040] Such as forming any of the masking substrates 1 to 7, wherein the oxygen content of the first hard masking film is 50 atomic% or more.

[0041] (Composition 9)

[0042] Such as forming any of the masking substrates 1 to 8, wherein the thickness of the first hard masking film is 7 nm or more.

[0043] (Composition 10)

[0044] Such as any of the masking substrates 1 to 9, wherein the thickness of the thin film used to form the pattern is less than 60 nm.

[0045] (Composition 11)

[0046] If any of the masking substrates 1 to 10 are formed, wherein the thin film for pattern formation is a light-shielding film, and a phase-shifting film is provided between the substrate and the light-shielding film.

[0047] (Composition 12)

[0048] For example, the masking substrate constituting 11, wherein the phase-shifting film system contains silicon.

[0049] (Composition 13)

[0050] If the masking substrate constitutes 11 or 12, wherein the phase shift film has the function of allowing the exposure light to pass through with a transmittance of more than 1%, and the function of causing the exposure light passing through the phase shift film to have a phase difference of more than 150 degrees and less than 210 degrees between it and the exposure light passing through the air at the same distance as the thickness of the phase shift film.

[0051] (Composition 14)

[0052] A method for manufacturing a transfer mask, comprising the following steps, using a mask substrate constituting any one of 1 to 10 mask substrates:

[0053] The process of forming a transfer pattern on the second hard mask film using a resist film having a transfer pattern formed on the second hard mask film as a mask, and forming the transfer pattern on the second hard mask film by dry etching using an oxygen-chlorine gas;

[0054] The process of forming the transfer pattern on the first hard mask film using a second hard mask film with the transfer pattern formed thereon as a mask, and forming the transfer pattern on the first hard mask film by dry etching using fluorine-based gases; and

[0055] The process of forming a transfer pattern on a thin film by using a first hard mask film with the transfer pattern as a mask and dry etching with an oxygen-chlorine gas to form the transfer pattern.

[0056] (Composition 15)

[0057] A method for manufacturing a transfer mask, comprising the following steps, using a mask substrate as described in 11 to 13:

[0058] The process of forming a transfer pattern on the second hard mask film using a resist film having a transfer pattern formed on the second hard mask film as a mask, and forming the transfer pattern on the second hard mask film by dry etching using an oxygen-chlorine gas;

[0059] The process of forming a transfer pattern on a first hard mask film by using a second hard mask film with the transfer pattern as a mask and dry etching with fluorine-based gas;

[0060] The process of forming a transfer pattern on a first hard mask film with the transfer pattern formed thereon, using dry etching with an oxygen-chlorine gas; and...

[0061] The process involves using a light-shielding film with the transfer pattern as a mask and forming the transfer pattern on the phase-shift film by dry etching with fluorine-based gases.

[0062] (Composition 16)

[0063] A method for manufacturing a semiconductor device includes a step of exposing and transferring a transfer pattern onto a resist film on a semiconductor substrate using a transfer mask manufactured by a method for manufacturing a transfer mask, such as 14 or 15.

[0064] According to the mask substrate of the present invention, a transfer mask with an auxiliary pattern of approximately 20 nm in size can be fabricated with high precision. Furthermore, the present invention can manufacture a transfer mask in which fine patterns can be precisely formed on a pattern-forming thin film using the mask substrate. Finally, the present invention provides a method for manufacturing a semiconductor device using a transfer mask manufactured by the above-described method. Simple Explanation of the Diagram

[0065] Figure 1 is a cross-sectional view showing the structure of the masking substrate (binary masking substrate) in the first embodiment of the present invention.

[0066] Figure 2 is a cross-sectional view showing the structure of the masking substrate (phase-shift masking substrate) in the second embodiment of the present invention.

[0067] Figure 3 is a cross-sectional view showing the structure of the transfer mask (binary mask) in the first embodiment of the present invention.

[0068] Figure 4 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. Implementation

[0069] Before describing the embodiments of the present invention, the process of completing the present invention will be described below.

[0070] When forming auxiliary patterns with a linewidth of approximately 20 nm on a patterning film (such as a light-shielding film) made of transition metal-based materials, it is difficult to form the auxiliary pattern on the patterning film using dry etching with an organic resist pattern as a mask. This is because during dry etching, the etching amount in the thickness direction of the resist pattern is greater, necessitating a thicker resist film. Furthermore, the etching amount in the sidewall direction of the resist pattern (side etching amount) is also relatively large. Generally, anticipating the effect of this side etching, the linewidth is made larger than the actual formed linewidth, and the pattern is drawn and exposed on the resist film using electron beams. If the side etching amount is very large, this adjustment becomes difficult.

[0071] To address these issues, a hard mask film made of silicon-based material is considered, placed between the pattern-forming thin film and the resist pattern. In this case, the following process is first performed: the hard mask film is dry-etched using the resist pattern as a mask to form the hard mask pattern; then, the pattern-forming thin film is dry-etched using the hard mask film as a mask to form the thin film pattern. The hard mask film essentially does not have the optical limitations required of the pattern-forming thin film. Therefore, the thickness of the hard mask film can be thinner than that of the pattern-forming thin film. Furthermore, the thickness of the resist film is sufficient only to function as a mask during the dry etching process when the hard mask film is patterned.

[0072] The thinner the hard mask film, the thinner the resist film can be. However, during dry etching of the pattern forming film, although not as noticeably as with the pattern forming film, the hard mask film will still be etched. Furthermore, if the hard mask film becomes thinner, there is a tendency for the verticality of the sidewalls of the pattern formed by dry etching to decrease. When using the hard mask pattern as a mask to dry etch the pattern forming film, the edges of the hard mask pattern (the top and sidewall edges of the hard mask pattern) are particularly easy to etch. During this dry etching, if the pattern edges are etched and become rounded, there is a tendency for the shape accuracy (LER, Line Edge Roughness, etc.) of the pattern formed on the pattern forming film to decrease. If the hard mask film is made thinner, the shape accuracy of the pattern formed on the pattern forming film will decrease. When forming auxiliary patterns with a linewidth of approximately 20 nm on the pattern forming film, the effect of this decrease in shape accuracy is particularly noticeable. Therefore, the hard mask film must have a certain thickness.

[0073] Generally, when patterning is applied to a resist film using electron beams, a grounding pin or other current-removing mechanism contacts the underlying film to release the charged electrons from the resist film. However, due to the poor conductivity of silicon oxide-based hard mask films, it is difficult to release electrons from the resist film to the outside using only the hard mask film. Transition metal-based patterning films have higher conductivity, allowing electrons in the resist film to be released from the patterning film to the outside via the hard mask film. However, as the thickness of the hard mask film increases, electrons in the resist film have difficulty passing through the hard mask film to reach the patterning film. Therefore, if the thickness of the hard mask film is increased, a problem of charge accumulation occurs during electron beam patterning. On the other hand, in recent years, a multi-beam writer using multiple electron guns to pattern the resist film has been developed. This problem becomes more pronounced when using a multi-beam writer to expose and pattern the resist film. Furthermore, this problem still occurs even when tantalum oxide-based materials are used as hard mask films.

[0074] Therefore, to address this conductivity issue, a second hard mask film (a transition metal-based hard mask film) was considered, further deposited on a silicon oxide-based or tantalum oxide-based hard mask film (the first hard mask film). Generally, it is desirable that the thickness-to-linewidth ratio of the resist pattern, i.e., the aspect ratio, be 1:2 or less. This is to suppress resist pattern tilting, and its necessity becomes even greater when dealing with fine patterns with linewidths as small as 20 nm. In other words, the resist pattern thickness is required to be 40 nm or less. To form a pattern on the second hard mask film using dry etching with the aforementioned thin resist pattern as a mask, the etching rate of the second hard mask film must be accelerated. Generally, there is a tendency for the etching rate to decrease as the transition metal content of the second hard mask film increases. Furthermore, in the second hard mask film, there is a tendency for the etching rate to increase as the content of gaseous elements such as oxygen or nitrogen at room temperature increases. An attempt was made to increase the etching rate by adding these elements to reduce the content of transition metals in the second hard mask film. However, it was found that while the etching rate increased due to the reduction of the transition metal content in the second hard mask film, the conductivity decreased. That is, although the second hard mask film described above is not like the first hard mask film, its conductivity is significantly reduced compared to the patterning film, making it difficult to fully release the electrons charged on the resist film during electron line exposure.

[0075] The inventors of this case painstakingly researched how to solve these problems and invented a method for electrically connecting a pattern-forming thin film to a second hard mask film.

[0076] That is, the masking substrate of the present invention has a structure in which a pattern forming film, a first hard masking film and a second hard masking film are sequentially deposited on the main surface of a substrate. The pattern forming film contains a transition metal, the first hard masking film contains one or more elements selected from silicon and tantalum and oxygen, the second hard masking film contains a transition metal, the content of the transition metal in the second hard masking 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 masking film is formed is smaller than the area where the pattern forming film is formed, and the second hard masking film and the pattern forming film are at least partially connected.

[0077] <Implementation Type 1>

[0078] [Mask substrate and its manufacturing]

[0079] The following description will be provided with reference to the diagrams for each implementation type.

[0080] Figure 1 is a cross-sectional view showing the structure of a mask substrate (binary mask substrate) 10 related to the first embodiment of the present invention. The mask substrate 10 of the present invention shown in Figure 1 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 deposited on a substrate 1.

[0081] The substrate 1 can be formed of quartz glass, aluminosilicate glass, soda lime glass, low thermal expansion glass (SiO2-TiO2 glass, etc.), etc., in addition to synthetic quartz glass. Among these, synthetic quartz glass is particularly good as a substrate material for forming the mask substrate because it has a higher transmittance of light relative to ArF exposure light and also has sufficient rigidity to prevent deformation.

[0082] In this embodiment, a first hard masking film 3 and a second hard masking film 4 are laminated on the light-shielding film 2. The light-shielding film 2, the first hard masking film 3, and the second hard masking film 4 can be either single-layer structures or laminated structures with two or more layers. Furthermore, the layers in the single-layer or laminated structures can be composed of approximately the same composition in the thickness direction of the film or layer, or they can be composed of a gradient in the thickness direction of the layers.

[0083] The light-shielding film 2 is a pattern-forming film formed when a binary mask is manufactured from a mask substrate, and a transfer pattern is formed thereon. The binary mask requires that the pattern of the light-shielding film 2 has high light-shielding performance. Only for the light-shielding film 2, the optical density (OD) relative to the exposed light must be 2.8 or higher, preferably 3.0 or higher.

[0084] The light-shielding film 2 is formed from a material that can be patterned by dry etching using an etching gas containing chlorine-based gases. Examples of materials with the above-mentioned characteristics include materials containing transition metals. Examples of transition metals contained in the light-shielding film 2 include any one of the following metals or alloys of such metals: molybdenum (Mo), tungsten (W), titanium (Ti), chromium (Cr), nickel (Ni), vanadium (V), zirconium (Zr), ruthenium (Ru), rhodium (Rh), niobium (Nb), and palladium (Pd).

[0085] The material forming the light-shielding film 2 can contain one or more elements selected from oxygen, nitrogen, carbon, boron, and hydrogen, provided that the optical concentration is within a range that will not significantly decrease. To reduce the reflectivity of the light-shielding film 2 relative to the exposed light on the surface opposite to the substrate 1, the surface layer opposite to the substrate 1 can contain more oxygen or nitrogen. The silicon content of the light-shielding film 2 is preferably 5 atomic% or less, more preferably 3 atomic% or less, and even more preferably, the maximum peak value of the narrow band spectrum of Si2p obtained by X-ray photoelectron spectroscopy is below the detection limit. Furthermore, as described later, the light-shielding film 2 is formed by sputtering. Therefore, the light-shielding film 2 can also contain inert gases such as argon (Ar), krypton (Kr), xenon (Xe), helium (He), and neon (Ne).

[0086] The light-shielding film 2 is preferably formed of a chromium-containing material. Besides chromium metal, examples of chromium-containing materials forming the light-shielding film 2 include materials that contain one or more elements selected from oxygen (O), nitrogen (N), carbon (C), boron (B), and fluorine (F). Generally, although chromium-based materials are etched by a mixture of chlorine-based and oxygen gases, the etching rate of chromium metal relative to this etching gas is not very high. Considering the need to increase the etching rate relative to the chlorine-based and oxygen-based gas mixture, the material forming the light-shielding film 2 is preferably a material that contains one or more elements selected from oxygen, nitrogen, carbon, boron, and fluorine. Furthermore, the chromium-containing material forming the light-shielding film 2 can also 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-based and oxygen-based gas mixture can be further accelerated.

[0087] To form SRAF patterns with a linewidth of approximately 20 nm with high precision, the thickness of the light-shielding film 2 is preferably 60 nm or less, and 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.

[0088] The first hard masking film 3 is formed of a material containing one or more elements selected from silicon and tantalum and oxygen, so that it can have etching selectivity relative to the etching gas used when etching the light-shielding film 2.

[0089] As a material containing silicon and oxygen, SiO2, SiON, etc. are preferred. In this case, the total silicon and oxygen content of the first hard mask film 3 is preferably 96 atomic% or more, and more preferably 98 atomic% or more. Furthermore, the total silicon, nitrogen, and oxygen content of the first hard mask film 3 is preferably 96 atomic% or more, and more preferably 98 atomic% or more. In addition, the first hard mask film 3 formed by the silicon and oxygen material can be positioned between the light-shielding film 2 and the second hard mask film 4 to include the transition metal within a range that allows for sufficient etching selectivity.

[0090] Furthermore, as a material containing tantalum and oxygen, examples include materials that contain 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, the first hard masking film 3 preferably contains boron among these materials.

[0091] 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 preferably 50 atomic% or more, more preferably 55 atomic% or more, and even more preferably 60 atomic% or more. In this way, the etching selectivity relative to the etching gas when patterning the light-shielding film 2 and the second hard mask film 4 can be further improved. Conversely, because the impedance value of the first hard mask film 3 is higher, when electron lines are used to trace the exposure, electrons irradiated on the resist film become more difficult to escape through the first hard mask film.

[0092] The first hard mask film 3, viewed from above (on the main surface of the substrate 1), is preferably formed to be a smaller area than the area where the light-shielding film 2 is formed. With this configuration, the light-shielding film 2 and the second hard mask film 4 can be easily joined at least partially. The first hard mask film 3 only needs to be of the size required to cover the pattern transfer area. For example, the first hard mask film 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 1.

[0093] In order for the first hard mask film 3 to function as a hard mask by forming an SRAF pattern of about 20 nm with high precision on the light-shielding film 2 (pattern forming film), its film thickness 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 about 20 nm with high precision on the first hard mask film 3 by dry etching using the pattern of the second hard mask film with a thinner film thickness (described later) as a mask, the film thickness of the first hard mask film 3 is preferably 20 nm or less, and more preferably 15 nm or less.

[0094] Furthermore, the film density of the first hard mask film 3 is preferably 1.5 g / cm³ to 9.0 g / cm³. As long as the film density of the first hard mask film 3 is at or above the aforementioned lower limit, its resistance to physical etching during dry etching of the light-shielding film 2 can be improved. In particular, when the first hard mask film 3 is formed of a material containing silicon and oxygen, the film density is preferably 1.5 g / cm³ to 3.0 g / cm³. On the other hand, when the first hard mask film 3 is formed of a material containing tantalum and oxygen, the film density is preferably 7.5 g / cm³ to 9.0 g / cm³.

[0095] Furthermore, a second hard masking film 4 is deposited on the first hard masking film 3. The second hard masking film 4 must have high etching selectivity relative to the etching gas used to pattern the first hard masking film 3. From this perspective, the second hard masking film 4 preferably contains a transition metal. Examples of transition metals contained in the second hard masking film 4 include any one of the following metals or alloys: molybdenum (Mo), tantalum (Ta), tungsten (W), titanium (Ti), chromium (Cr), hafnium (Ht), nickel (Ni), vanadium (V), zirconium (Zr), ruthenium (Ru), rhodium (Rh), niobium (Nb), and palladium (Pd). The second hard masking film 4 is preferably formed of a material that can be patterned by dry etching using an etching gas containing chlorine-based gases. Furthermore, if the light-shielding film 2 and the second hard masking film 4 contain the same transition metal, it is easier to etch them using dry etching with the same etching gas, which is preferable.

[0096] It is preferable to include at least one of oxygen and nitrogen in the second hard mask film 4, as this improves the etching rate; the presence of oxygen is even more desirable. Furthermore, to further improve the etching rate compared to the light-shielding film 2, the total oxygen and nitrogen content of the second hard mask film 4 is preferably greater than that of the light-shielding film 2. For the same reason, the transition metal content of the second hard mask film 4 is preferably less than that of the light-shielding film 2. Further, 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. Further, the transition metal content of the second hard mask film 4 is preferably 60 atomic% or less, more preferably 55 atomic% or less.

[0097] 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, and more preferably 32 atomic% or more. Also, the oxygen content of the second hard mask film 4 is preferably 20 atomic% or more.

[0098] The second hard masking film 4 is preferably formed of a chromium-containing material. Besides chromium metal, examples of chromium-containing materials for forming the second hard masking film 4 include materials containing one or more elements selected from oxygen (O), nitrogen (N), carbon (C), boron (B), and fluorine (F). Generally, while chromium-based materials are etched by a mixture of chlorine-based and oxygen gases, the etching rate of chromium metal relative to this etching gas is not very high. Considering the need to increase the etching rate relative to the chlorine-based and oxygen-based gas mixture, it is preferable that the material for forming the second hard masking film 4 contains one or more elements selected from oxygen, nitrogen, carbon, boron, and fluorine. Furthermore, the chromium-containing material for forming the second hard masking film 4 may also 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-based and oxygen-based gas mixture can be further accelerated.

[0099] In order to form an SRAF pattern of about 20 nm with high precision by dry etching using a resist pattern with a thickness of less than 40 nm as a mask, the thickness of the second hard mask film 4 is preferably less than 5 nm, and more preferably less than 4 nm. On the other hand, in order to make the pattern of the second hard mask film 4 function fully as a mask during the dry etching of the pattern formed by the first hard mask film, the thickness of the second hard mask film 4 is preferably more than 2 nm.

[0100] On the main surface of substrate 1, the area where the second hard mask film 4 is formed is preferably 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 such a way that they are joined at the outer side of the first hard mask film 3, thereby ensuring conductivity in the outer peripheral area. The second hard mask film 4 is preferably formed to extend beyond the outer periphery of the area where the first hard mask film 3 is formed (i.e., the entire first hard mask film 3 is covered by the second hard mask film 4). On the other hand, a portion of the second hard mask film 4 may be formed to extend beyond the outer periphery of the area where the first hard mask film 3 is formed and to be in contact with the light-shielding film 2, and the portion other than that portion is formed in the same area as the area where the first hard mask film 3 is formed.

[0101] Furthermore, the membrane density of the second hard masking film 4 is preferably 3.5 g / cm3 to 7.0 g / cm3.

[0102] In the mask substrate 10, it is preferable to form an organic material resist film 5 with a film thickness of less than 40 nm, which is attached to the surface of the second hard mask film 4. If so, even when drawing a transfer pattern containing a fine auxiliary pattern of about 20 nm, the aspect ratio of the resist pattern can still be as low as 1:2 or more, thus preventing the resist pattern from tilting or detaching during the development and rinsing of the resist film 5.

[0103] The light-shielding film 2, the first hard mask film 3, and the second hard mask film 4 can be formed separately by reactive sputtering. The sputtering method can be either DC sputtering or RF sputtering. Furthermore, even magnetron sputtering can be a conventional method. DC sputtering is advantageous due to its simpler structure. Additionally, magnetron sputtering offers a faster film formation rate, which is advantageous from the perspective of improving productivity. Moreover, the film formation apparatus can be either in-line or monolithic.

[0104] Furthermore, when the substrate 1 is placed on a rotating stage in the film forming apparatus, and when the light-shielding film 2, the first hard mask film 3, and the second hard mask film 4 are formed, the mask is placed on the main surface of the substrate 1 and the opening area of ​​the mask is adjusted, thereby adjusting the film forming area of ​​each film on the main surface of the substrate 1 to the desired area.

[0105] Furthermore, the resist film 5 is formed by spin coating.

[0106] In this way, although the structure of the masking substrate 10 of this embodiment has been described with reference to FIG1, it is not limited to this structure. For example, a charge dissipation layer (CDL) can be formed on the surface of the resist film 5, or it can be a masking substrate without the resist film 5.

[0107] [Manufacturing Method of Transfer Mask (Binary Mask)]

[0108] The manufacturing method of the transfer mask (binary mask) using the mask substrate 10 related to the first embodiment will be explained using FIG3.

[0109] For the resist film 5 with a thickness of less than 40 nm formed by spin coating on the mask substrate 10 shown in Figure 1, the first pattern to be formed on the light-shielding film 2 is drawn using electron beams, and further specific processes such as development are performed to form a resist film (resist pattern) 5a with the first pattern (see Figure 3(a)). In addition to the pattern (main pattern) transferred onto the semiconductor device, the first pattern also includes an auxiliary pattern with a linewidth of about 20 nm.

[0110] At this time, in a specific area where the second hard mask film 4, located further out than the first hard mask film 3, contacts the light-shielding film 2, a grounding pin (not shown in the figure) is brought into contact to ensure grounding between the resist film 5, the second hard mask film 4, and the light-shielding film 2. This suppresses the accumulation of charge when electron lines are drawn on the resist film 5, thereby enabling exposure drawing with high positional accuracy.

[0111] Next, the second hard mask film 4 is dry-etched using a mixture of chlorine and oxygen gases, with the resist pattern 5a as a mask, to form the second hard mask film (hard mask pattern) 4a having the first pattern (see Figure 3(b)). After that, the resist pattern 5a is removed.

[0112] Next, the first hard mask film 3 is dry-etched using a fluorine-based gas with the second hard mask pattern 4a as a mask to form a first hard mask film (first hard mask pattern) 3a with the first pattern (see Figure 3(b)). Then, other resist films are formed by spin coating. Afterwards, the area where the first hard mask pattern 3a is formed is laser-etched onto this resist film, and further specific processing such as development is performed to form a resist film (resist pattern) 6b with the second pattern (see Figure 3(c)). (Furthermore, during this stage, the light-shielding film 2 will remain as shown in Figure 3(b)). Then, the light-shielding film 2 is dry-etched using a mixture of chlorine-based gas and oxygen gas with the first hard mask pattern 3a and the resist pattern 6b as masks to form a light-shielding film (light-shielding pattern) 2a with the first pattern (see Figure 3(c)). At this point, the exposed portion of the second hard mask pattern 4a will be removed by dry etching, thus becoming the second hard mask film (second hard mask pattern) 4b with the second pattern (see Figure 3(c)).

[0113] Then, using the resist pattern 6b and the second hard mask pattern 4b as masks, the first hard mask pattern 3a is dry-etched with fluorine-based gas to remove the first hard mask pattern 3a. Further, the resist pattern 6b is removed and a cleaning process is performed to manufacture a transfer mask (binary mask) 100 (see Figure 3(d)).

[0114] [Semiconductor device manufacturing]

[0115] The semiconductor device manufacturing method of the first embodiment is characterized by using a binary mask (transfer mask) 100 of the first embodiment or a binary mask (transfer mask) 100 manufactured using a mask substrate 10 of the first embodiment to expose and transfer a transfer pattern onto a resist film on a semiconductor substrate. Therefore, by using the binary mask 100 of the first embodiment to expose and transfer the resist film onto the semiconductor device, the accuracy of the design pattern can be sufficiently satisfied to form the resist film on the semiconductor device.

[0116] <Second Implementation Type>

[0117] [Mask substrate and its manufacturing]

[0118] The mask substrate related to the second embodiment of the present invention has a phase-shifting film between a substrate and a light-shielding film, and is used to manufacture a phase-shifting mask (a mask for transfer printing). Figure 2 shows the structure of the mask substrate of the second embodiment. The mask substrate 20 related to the second embodiment has a phase-shifting film 12, a light-shielding film (a thin film for pattern forming) 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. Since the substrate 11 and the resist film 16 are the same as those in the first embodiment, their description is omitted.

[0119] The phase-shift film 12 is formed from a material that can be patterned by dry etching using a fluorine-based etching gas, specifically, it is composed of a silicon-containing material. The phase-shift film 12 preferably has the function of allowing exposure light to pass through with a transmittance of 1% or more (transmittance), and the function of creating a phase difference of 150 degrees to 210 degrees between the exposure light passing through the phase-shift film and the exposure light passing through the same distance in air as the thickness of the phase-shift film. Furthermore, the transmittance of the phase-shift film 12 is preferably 2% or more. The transmittance of the phase-shift film 12 is preferably 30% or less, and more preferably 20% or less.

[0120] The phase-shifting film 12, in addition to silicon, is preferably formed of a nitrogen-containing material. The phase-shifting film 12 may also contain one or more elements selected from metallic elements, non-metallic elements, and metallic elements, provided that it can be patterned by dry etching using fluorine-based gases. The metallic elements may be any type of metallic element other than silicon. The non-metallic elements may be any non-metallic element other than nitrogen, and preferably contain one or more elements selected from, for example, 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).

[0121] The thickness of the phase-shifting film 12 is preferably 80 nm or less, and 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, a thickness of 50 nm or more is necessary. Furthermore, the phase-shifting film 12 can be either a single-layer structure or a multilayer structure with two or more layers. Moreover, the layers in the single-layer or multilayer structure can have a composition that is substantially the same in the thickness direction of the film or layer, or they can have a gradient composition in the thickness direction of the layers.

[0122] Furthermore, the phase-shifting film 12 is preferably formed from an area that is smaller than the area where the light-shielding film 13 is formed when viewed from above (on the main surface of the substrate 1). The area where the phase-shifting film 12 is formed is required to be at least the size of the pattern transfer area. For example, the phase-shifting film 12 is preferably formed to cover an area that includes at least a quadrilateral area with a side length of 132 mm and a reference to the center of the main surface of the substrate 11.

[0123] In the phase-shifting film 12, in order to satisfy the aforementioned conditions related to optical properties and film thickness, the refractive index n of the phase-shifting film relative to the 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-shifting film 12 is preferably 3.1 or lower, more preferably 2.7 or lower. The extinction coefficient k of the phase-shifting film 12 relative to the ArF exposure light is preferably 0.26 or higher, more preferably 0.29 or higher. Furthermore, the extinction coefficient k of the phase-shifting film 12 is preferably 0.62 or lower, more preferably 0.54 or lower.

[0124] Furthermore, the refractive index n and extinction coefficient k of the thin film containing the phase-shift film 12 are not determined solely by the composition of the thin film. The film density and crystallization state of the thin film also influence the refractive index n and extinction coefficient k. Therefore, the film is formed in such a way that the film achieves the desired refractive index n and extinction coefficient k by adjusting the conditions during reactive sputtering. When forming a film by reactive sputtering, adjusting the ratio of the inert gas to the reactive gas (oxygen, nitrogen, etc.) mixture is effective in making the phase-shift film 12 fall within the aforementioned range of refractive index n and extinction coefficient k, but it is not limited to this. Various methods can also be used, such as adjusting the pressure in the film-forming chamber, the electric current applied to the sputtering target, and the positional relationship between the target and the substrate 11 during reactive sputtering. Moreover, these film-forming conditions are inherent to the film-forming apparatus and can be appropriately adjusted to make the formed phase-shift film 12 achieve the desired refractive index n and extinction coefficient k.

[0125] The masking substrate 20 is attached to the phase shift film 12 and has a light-shielding film 13. In this configuration, the light-shielding film 13 must be made of a material that has sufficient etching selectivity relative to the etching gas used when patterning is formed on the phase shift film 12.

[0126] In this case, the same material as the light-shielding film 2 described in the first embodiment can also be used in the light-shielding film 13. Furthermore, as will be explained later, when the light-shielding film 13 is disposed on the phase-shifting film 12, the OD (exposure) is not required to be the same as that of the light-shielding film 2 used in binary masks. Therefore, the film thickness of the light-shielding film 13 is preferably 50 nm or less, and 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.

[0127] After the phase-shift mask is completed, a light-shielding strip is formed by stacking the light-shielding film 13 and the phase-shift film 12. Therefore, the stacking structure of the light-shielding film 13 and the phase-shift film 12 is required to ensure an optical density (OD) greater than 2.0, preferably 2.8 or higher, and more preferably 3.0 or higher.

[0128] A first hard masking film 14 is formed on the light-shielding film 13. The first hard masking film 14 is formed of a material containing one or more elements selected from silicon and tantalum and oxygen, so that it can have etching selectivity relative to the etching gas used when etching the light-shielding film 13. The specific material or film thickness is the same as that of the first hard masking film 3 in the first embodiment.

[0129] Furthermore, the first hard mask film 14 is preferably formed from an area that is smaller than the area where the light-shielding film 13 is formed when viewed from above (on the main surface of the substrate 1). By adopting the above configuration, it is easy to make the light-shielding film 13 and the second hard mask film 15 at least partially adjoin each other. The first hard mask film 14 only needs to be of the required size to cover the pattern transfer area where the phase-shift film 12 is formed. For example, the first hard mask film 14 is preferably formed to cover an area that includes at least a quadrilateral area with a side length of 132 mm based on the center of the main surface of the substrate 11.

[0130] Furthermore, a second hard mask film 15 is deposited on the first hard mask film 14. The second hard mask film 15 must have high etch selectivity relative to the etch gas used to pattern the first hard mask film 14. From this viewpoint, the second hard mask film 15 preferably contains a transition metal. The specific material or film thickness is the same as that of the second hard mask film 4 in the first embodiment.

[0131] Furthermore, on the main surface of the substrate 11, the area 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 they are joined on the outer side of the first hard mask film 14, thereby ensuring conductivity in the outer peripheral region.

[0132] Preferably, the second hard mask film 15 is formed to extend beyond the outer periphery of the area where the first hard mask film 14 is formed (that is, the entire first hard mask film 14 is covered by the second hard mask film 15). Alternatively, a portion of the second hard mask film 15 may be formed to extend beyond the outer periphery of the area where the first hard mask film 14 is formed and adjoin the light-shielding film 13, and otherwise formed in the same area as the area where the first hard mask film 14 is formed.

[0133] 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 separately by reactive sputtering, just like in the first embodiment.

[0134] Furthermore, when the phase shift film 12, the light-shielding film 13, the first hard mask film 14, and the second hard mask film 15 are formed, the film formation area of ​​each film can be adjusted to the required area by adjusting the opening area of ​​the mask.

[0135] Furthermore, the resist film 16 is formed by spin coating.

[0136] [Manufacturing method of transfer mask (phase shift mask)]

[0137] The manufacturing method of the transfer mask (phase shift mask) of the mask substrate 20 associated with this second embodiment will be explained using FIG4.

[0138] For the resist film 16 with a thickness of less than 40 nm formed by spin coating on the mask substrate 20 shown in Figure 2, the first pattern to be formed on the phase shift film 12 is drawn using electron beams, and further specific processes such as development are performed to form a resist film (resist pattern) 16a with the first pattern (see Figure 4(a)). In addition to the pattern (main pattern) that has been transferred onto the semiconductor device, this first pattern also includes an auxiliary pattern with a linewidth of about 20 nm.

[0139] At this time, in a specific area where the second hard mask film 15, located further outward than the first hard mask film 14, contacts the light-shielding film 13, grounding pins (not shown in the figure) are brought into contact to ensure grounding between the resist film 16, the second hard mask film 15, and the light-shielding film 13. Thus, the accumulation of charge during the drawing of electron lines on the resist film 16 can be suppressed, thereby enabling exposure drawing with high positional accuracy (and similarly, the accumulation of charge can be suppressed during the formation of the resist patterns 17b and 18c described later, thereby enabling exposure drawing with high positional accuracy).

[0140] Next, using the resist pattern 16a as a mask, a mixture of chlorine and oxygen gases is used to dry etch the second hard mask film 15 to form the second hard mask film (hard mask pattern) 15a with the first pattern (see Figure 4(b)). After that, the resist pattern 16a is removed.

[0141] 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 Figure 4(b)). Next, other resist films are formed by spin coating. Then, the area where the first hard mask pattern 14a is formed is laser-etched onto this resist film, and further specific processing such as development is performed to form a resist film (resist pattern) 17b with the second pattern (see Figure 4(c)). (Furthermore, during this stage, the light-shielding film 13 and the second hard mask pattern 15a remain as shown in Figure 4(b)). Next, 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-based gas and oxygen to form a light-shielding film (light-shielding pattern) 13a with the first pattern (see 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 Figure 4(c)).

[0142] 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 Figure 4(d)). At this time, the first hard mask pattern 14a is removed (see Figure 4(d)).

[0143] Then, the resist pattern 17b is removed and a cleaning process is performed to form other resist films by spin coating. Next, for this resist film, a third pattern to be formed on the light-shielding film 13 is drawn using electron beams, and further specific processes such as development are performed to form a resist film (resist pattern) 18c with the third pattern (see 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 gases 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 to manufacture a transfer mask (phase-shift mask) 200 (see Figure 4(f)).

[0144] [Semiconductor device manufacturing]

[0145] The method for manufacturing a semiconductor device according to the second embodiment is characterized by using a phase shift mask 200 of the second embodiment or a phase shift mask 200 manufactured using a mask substrate 20 of the first embodiment to expose and transfer a resist film for transfer patterns onto a semiconductor substrate. Therefore, if the phase shift mask 200 of the second embodiment is used to expose and transfer the resist film onto the semiconductor device, the pattern can be formed on the resist film of the semiconductor device with sufficient accuracy to meet the design specifications.

[0146] Furthermore, the masking substrate of the present invention can also be a reflective masking substrate used in manufacturing reflective masks for EUV (Extreme Ultraviolet Lithography). In this case, it is preferable to use the above-described pattern-forming thin film to form the absorber film.

[0147] In the case of this reflective shielding substrate, a low thermal expansion glass (such as SiO2-TiO2 glass) is preferably used as the substrate. Furthermore, it is preferable to sequentially deposit multiple layers of reflective film, protective film, absorber film (patterning film), first hard shielding film, and second hard shielding film on the substrate. The structures of the absorber film, first hard shielding film, and second hard shielding film are preferably the same as those shown in the above embodiments. The absorber film is preferably formed from the aforementioned chromium-containing material. On the other hand, a ruthenium-containing material can also be used for the absorber film. Examples of ruthenium-containing materials in this case, besides ruthenium metal monomers, include materials containing at least one of nitrogen and oxygen in ruthenium.

[0148] Multilayer reflective films provide the function of reflecting EUV light in reflective shields. A multilayer reflective film is a film consisting of layers periodically stacked with elements of different refractive indices as the main components. Generally, it uses a multilayer film with approximately 40 to 60 alternating periods (pairs) of thin films of light elements or their compounds of high refractive index materials (high refractive index layers) and thin films of heavy elements or their compounds of low refractive index materials (low refractive index layers).

[0149] As a high refractive index layer, silicon (Si) materials can be used, for example. As a silicon-containing material, in addition to silicon monomers, silicon compounds containing at least one element selected from boron (B), carbon (C), zirconium (Zr), nitrogen (N), and oxygen (O) can be used. As a low refractive index layer, at least one metal monomer selected from molybdenum (Mo), ruthenium (Ru), rhodium (Rh), and platinum (Pt), or alloys thereof, can be used. 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 with approximately 40 to 60 alternating periods of Mo-containing layers and Si-containing layers is preferred.

[0150] The protective film can be made of silicon (Si), materials containing silicon (Si) and oxygen (O), materials containing silicon (Si) and nitrogen (N), or materials containing silicon (Si), oxygen (O), and nitrogen (N), etc. Furthermore, when the absorber film is formed of a ruthenium-containing material, the protective film can be made of chromium (Cr), or a chromium-based material containing chromium (Cr) and at least one element selected from 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 ruthenium-containing materials. Examples of ruthenium-containing materials include Ru metal monomers; 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.

[0151] <Example>

[0152] The following examples will illustrate the embodiments of the present invention in more detail.

[0153] (Example 1)

[0154] [Mask substrate manufacturing]

[0155] Referring to Figure 2, a 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 is prepared. The substrate 11 is prepared by grinding the main surface to a specific surface roughness (Rq is less than 0.2 nm), followed by specific cleaning and drying treatments.

[0156] Next, substrate 11 is placed in a monolithic DC sputtering apparatus, and a phase-shifting film 12 composed of molybdenum (Mo) and silicon (Si) mixed sintered target (Mo:Si = 11 atomic%: 89 atomic%) is formed on substrate 11 using reactive sputtering (DC sputtering) with a mixed gas of argon (Ar), nitrogen (N2), and helium (He) as the sputtering gas, to a thickness of 69 nm. A shielding plate is used during the sputtering of this phase-shifting film 12. The shielding plate has a square opening with a side length of 146 mm based on the center of the substrate (that is, the design area is a square area with a side length of 146 mm).

[0157] Next, for the substrate 11 on which the phase-shifting film 12 is formed, a heat treatment is performed to reduce the film stress of the phase-shifting film 12 and to form an oxide layer on the surface. Specifically, the heat treatment is performed in an electric furnace at an atmospheric temperature of 450°C for 1 hour. After measuring the transmittance and phase difference of the phase-shifting film 12 with respect to light with a wavelength of 193 nm using a phase shift measurement device (Lasertec MPM193), the transmittance was found to be 6.0% and the phase difference was 177.0 degrees (deg).

[0158] Next, the substrate 11 with the phase-shifting film 12 formed is placed in a monolithic DC sputtering apparatus, and reactive sputtering (DC sputtering) is performed using a chromium (Cr) target in a mixed gas atmosphere of argon (Ar), carbon dioxide (CO2), and helium (He). Thereby, a light-shielding film (CrOC film Cr:O:C = 70.4 atomic%:15.4 atomic%:14.2 atomic%) 13 composed of chromium, oxygen, and carbon is formed in contact with the phase-shifting film 12 with a film thickness of 36 nm. A shielding plate is also used during the sputtering of this light-shielding film 13. Furthermore, 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). One side of the main surface of the substrate 11 is 151.2 mm in size, leaving very little margin between it and the design area.

[0159] Next, the substrate 11 on which the light-shielding film (CrOC film) 13 is formed is subjected to heat treatment. Specifically, the heat treatment is performed by heating the substrate 11 with the phase-shifting film 12 and the light-shielding film 13 in the atmosphere at a temperature of 280°C for 5 minutes using a heating plate. After the heat treatment, the optical concentration of the phase-shifting film 12 and the light-shielding film 13 laminated on the substrate 11 is measured using a spectrometer (Cary4000 manufactured by Agilent Technologies) at the wavelength (approximately 193 nm) of ArF excimer laser light, and it is confirmed to be 3.0 or higher.

[0160] Next, a first hard mask film 14 (SiO2 film, Si:O = 33.8 atomic%, 66.2 atomic%) is formed on the light-shielding film 13 with a thickness of 12 nm. Specifically, a substrate 11 on which the phase-shifting film 12 and the light-shielding film 13 are deposited is placed in a monolithic DC sputtering apparatus, and a silicon (Si) target is used with argon (Ar) and oxygen (O2) as sputtering gases to form the first hard mask film 14 by DC sputtering. A shielding plate is used during the sputtering of this first hard mask film 14. The shielding plate used has a square opening with a side length of 146 mm based on the center of the substrate (that is, the design area is a square area with a side length of 146 mm).

[0161] A first hard mask film 14 with a thickness of 12 nm was deposited on another substrate, and the film density was measured to be 1.8 g / cm3. Furthermore, the sheet resistance was measured to be 40 kΩ.

[0162] Next, a second hard masking film 15 (CrOCN film, Cr: 54.7 atomic%, O: 22.2 atomic%, C: 11.9 atomic%, N: 11.2 atomic%) is formed on the first hard masking film 14 with a thickness of 3 nm. Specifically, a substrate 11 on which the phase-shifting film 12, the light-shielding film 13, and the first hard masking film 14 are deposited is placed in a monolithic DC sputtering apparatus, and reactive sputtering (DC sputtering) is 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 is used during the sputtering of this second hard masking film 15. The shielding plate used has a square opening with a side length of 148 mm based on the center of the substrate (that is, the design area is a square area with a side length of 148 mm).

[0163] A second hard mask film with a thickness of 3 nm was deposited on another substrate, and the film density was measured to be 4.9 g / cm³. Furthermore, the sheet resistance was measured to be 200 kΩ.

[0164] Then, after a specific cleaning process, a resist film 16 with a thickness of 40 nm is formed by spin coating to produce the mask substrate 20 of Example 1.

[0165] [Manufacturing of a transfer mask (phase shift mask)]

[0166] Next, using the masking substrate 20 of Embodiment 1 and FIG4, the halftone phase shift mask 200 of Embodiment 1 is manufactured in the above-described order of steps.

[0167] More specifically, the etching of the second hard mask film 15 uses a mixture of chlorine (Cl2) and oxygen (O2) (gas flow ratio Cl2:O2=15:1) to create the second hard mask pattern 15a (see Figure 4(b)).

[0168] Furthermore, the etching of the first hard mask film 14 uses CF4 gas as a fluorine-based gas to create the first hard mask pattern 14a (see Figure 4(b)).

[0169] Furthermore, the etching of the light-shielding film 13 uses a mixture of chlorine (Cl2) and oxygen (O2) (gas flow ratio Cl2:O2=15:1) to create the light-shielding patterns 13a and 13c (see Figure 4(c) and Figure 4(d)).

[0170] Furthermore, the etching system of the phase-shifting film 12 uses SF4 gas as a fluorine-based gas to create the phase-shifting pattern 12a (see Figure 4(b)).

[0171] Furthermore, in this series of processes, during the electron line drawing, a multi-beam writer equipped with two electron guns is used, and grounding pins (not shown in the figure) are brought into contact in a specific area where the second hard mask film 15 and the light-shielding film 13 are in contact, located further outward than the first hard mask film 14. In this way, electron lines are drawn on each resist film at the desired location, forming the desired resist patterns 16a, 17b, and 18c. The resist pattern 16a includes not only the main pattern for transfer but also a fine SRAF pattern with a linewidth of 20 nm.

[0172] For the phase-shift mask 200 of Example 1, the length of the SRAF pattern with a linewidth of 20 nm 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 the main pattern for transfer was indeed valid, and that a phase-shift pattern could be formed with good LER for the fine SRAF pattern with a linewidth of 20 nm.

[0173] For the phase shift mask 200 fabricated through the above steps, an AIMS193 (manufactured by Carl Zeiss) was used to simulate the transfer image when the resist film transferred onto the semiconductor device is exposed with exposure light at a wavelength of 193 nm. Verification of this simulated exposure transfer image showed that it fully met the design specifications. Therefore, it can be concluded that even when the phase shift mask 200 of Embodiment 1 is mounted on the mask stage of an exposure apparatus to expose the resist film transferred onto the semiconductor device, the circuit pattern formed on the semiconductor device can still be achieved with high precision.

[0174] (Comparative Example 1)

[0175] [Mask substrate fabrication]

[0176] The masking substrate of Comparative Example 1, except for the hard masking film, was manufactured using the same steps as in Example 1. The hard masking film of Comparative Example 1 did not form the second hard masking film 15 of Example 1, but instead formed a film of the same material as the first hard masking film 14 (SiO2 film, Si:O = 34 atomic%, 66 atomic%) with a thickness of 12 nm. Then, after treating the surface of the hard masking film with HMDS (Hexamethyl disilazane), a 40 nm resist film was formed by spin coating.

[0177] [Manufacturing of a transfer mask (phase shift mask)]

[0178] Next, using the masking substrate of Comparative Example 1, we attempted to create a halftone phase-shift mask.

[0179] For the resist film formed on the mask substrate of Comparative Example 1, electronic line drawing was performed using the same steps as in Example 1. This time, grounding pins were brought into contact in a specific area where the hard mask film and the light-shielding film of Comparative Example 1 met. However, during the formation of the resist pattern, static electricity accumulated, preventing the desired pattern from being drawn.

[0180] (Comparative Example 2)

[0181] [Mask substrate fabrication]

[0182] The mask substrate of Comparative Example 2, except for the hard mask film, was manufactured using the same steps as in Example 1. The hard mask film of Comparative Example 2 was modified from the hard mask film of Example 1, except for the composition of the second hard mask film 15. Specifically, the second hard mask film was formed under the same film-forming conditions as the light-shielding film, using a material composed of 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.

[0183] [Manufacturing of a transfer mask (phase shift mask)]

[0184] Next, a half-tone phase-shift mask was manufactured using the mask substrate of Comparative Example 2. The manufacturing process of the phase-shift mask was the same as that described in Example 1.

[0185] When depicting the resist film formed on the masking substrate of Comparative Example 2 using electronic lines, the grounding pins are brought into contact in a specific area where the second hard masking film and the light-shielding film of Comparative Example 2 are in contact.

[0186] In the same manner as in Example 1, the phase-shift mask of Comparative Example 2 was manufactured.

[0187] For the phase-shift mask in Comparative Example 2, the length of the pattern was measured using a Critical Dimension-Scanning Electron Microscope (CD-SEM) centered on the area where a 20 nm linewidth SRAF pattern was formed. The results showed that several areas where the pattern itself failed to form were observed in both the main pattern used for transfer and the fine 20 nm linewidth SRAF pattern. This is presumably because when the second hard mask film was patterned using dry etching with a 40 nm thick resist pattern as a mask, the slower etching rate of the second hard mask film caused the resist pattern to disappear before the second hard mask film was completed.

[0188] 1:Substrate

[0189] 2: Light-shielding film (film for pattern forming)

[0190] 2b: Light-shielding film with the second pattern (light-shielding pattern)

[0191] 3: First hard masking film

[0192] 3a: A first hard mask film with a first pattern (first hard mask pattern)

[0193] 4: Second hard masking film

[0194] 4a: A second hard mask film with the first pattern (second hard mask pattern)

[0195] 4b: A second hard mask film with a second pattern (second hard mask pattern)

[0196] 5: Resistor film

[0197] 5a: Resistor film with pattern 1 (resistor pattern)

[0198] 6b: Resistor film with pattern 2 (resistor pattern)

[0199] 10: Masking Base (Binary Masking Base)

[0200] 11:Substrate

[0201] 12: Phase-shifting film (thin film for patterning)

[0202] 12a: Phase-shifting film with pattern 1 (phase-shifting pattern)

[0203] 13: Light-shielding film (film for pattern forming)

[0204] 13a: Light-shielding film with pattern 1 (light-shielding pattern)

[0205] 13c: Light-blocking film with the third pattern (light-blocking pattern)

[0206] 14: First hard masking film

[0207] 14a: A first hard mask film having a first pattern (first hard mask pattern)

[0208] 15: Second hard mask film

[0209] 15a: A second hard mask film having the first pattern (second hard mask pattern)

[0210] 15b: Second hard mask film with second pattern (second hard mask pattern)

[0211] 16: Resistor film

[0212] 16a: Resistor film with pattern 1 (resistor pattern)

[0213] 17b: Resistor film with pattern 2 (resistor pattern)

[0214] 18c: A resistive film with a third pattern (resistor pattern)

[0215] 20: Masking substrate (phase-shift masking substrate)

[0216] 100: Transfer mask (binary mask)

[0217] 200: Transfer mask (phase shift mask)

Claims

1. A masking substrate having a structure in which a pattern forming film, a first hard masking film, and a second hard masking film are sequentially deposited on the main surface of a substrate; the pattern forming film contains a transition metal; the first hard masking film contains one or more elements selected from silicon and tantalum and oxygen; the second hard masking film contains a transition metal; the content of the transition metal in the second hard masking film is less than the content of the transition metal in the pattern forming film; on the main surface, the area on which the first hard masking film is formed is smaller than the area on which the pattern forming film is formed; the second hard masking film and the pattern forming film are at least partially connected.

2. The masking substrate of claim 1, wherein the total oxygen and nitrogen content of the second hard masking film is greater than the total oxygen and nitrogen content of the pattern forming film.

3. The masking substrate of claim 1 or 2, wherein the area on the main surface in which the second hard masking film is formed is larger than the area in which the first hard masking film is formed.

4. The masking substrate of claim 1 or 2, wherein the difference between the content of the transition metal in the pattern forming film and the content of the transition metal in the second hard masking film is 10 atomic% or more.

5. The masking substrate of claim 1 or 2, wherein the total oxygen and nitrogen content of the second hard masking film is 30 atomic% or more.

6. The masking substrate of claim 1 or 2, wherein the thickness of the second hard masking film is less than 5 nm.

7. The masking substrate of claim 1 or 2, wherein the total oxygen and nitrogen content of the first hard masking film is 50 atomic% or more.

8. The masking substrate of claim 1 or 2, wherein the oxygen content of the first hard masking film is 50 atomic% or more.

9. The masking substrate of claim 1 or 2, wherein the thickness of the first hard masking film is 7 nm or more.

10. The masking substrate of claim 1 or 2, wherein the thickness of the thin film for pattern formation is 60 nm or less.

11. The masking substrate of claim 1 or 2, wherein the pattern forming film is a light-shielding film, and a phase-shifting film is provided between the substrate and the light-shielding film.

12. The masking substrate of claim 11, wherein the phase-shifting film contains silicon.

13. The mask substrate of claim 11, wherein the phase shift film has the function of allowing exposure light to pass through with a transmittance of more than 1%, and the function of causing the exposure light passing through the phase shift film to have a phase difference of more than 150 degrees and less than 210 degrees between it and the exposure light passing through the air at a distance equal to the thickness of the phase shift film.

14. A method for manufacturing a transfer mask, comprising the steps of: using a mask substrate as described in any one of claims 1 to 10, a method for manufacturing a transfer mask using a resist film having a transfer pattern formed on the second hard mask film as a mask, and forming a transfer pattern on the second hard mask film by dry etching using an oxygen-chlorine gas; using the second hard mask film having the transfer pattern formed as a mask, and forming a transfer pattern on the first hard mask film by dry etching using a fluorine gas; and using the first hard mask film having the transfer pattern formed as a mask, and forming a transfer pattern on the pattern forming film by dry etching using an oxygen-chlorine gas.

15. A method for manufacturing a transfer mask, comprising the following steps: using a mask substrate as described in any one of claims 11 to 13, a method for manufacturing a transfer mask using a resist film having a transfer pattern formed on the second hard mask film as a mask, and forming a transfer pattern on the second hard mask film by dry etching using an oxygen-chlorine gas; using the second hard mask film having the transfer pattern formed as a mask, and forming a transfer pattern on the first hard mask film by dry etching using a fluorine gas; using the first hard mask film having the transfer pattern formed as a mask, and forming a transfer pattern on the light-shielding film by dry etching using an oxygen-chlorine gas; and using the light-shielding film having the transfer pattern formed as a mask, and forming a transfer pattern on the phase-shifting film by dry etching using a fluorine gas.

16. A method for manufacturing a semiconductor device, comprising a step of exposing and transferring a transfer pattern onto a resist film on a semiconductor substrate using a transfer mask manufactured by a method for manufacturing a transfer mask as described in claims 14 or 15.

Images