JP2021056502A - Substrate with multi-layered reflecting film, reflective mask blank, reflective mask and method for manufacturing the same, and method for manufacturing semiconductor device - Google Patents

Abstract

To provide a substrate with multi-layered reflecting film for manufacturing a reflective mask having a protective film with high tolerance to etching gas and high tolerance to washing.SOLUTION: A substrate with multi-layered reflecting film has: a substrate 1; a multi-layered reflecting film 5 provided on the substrate; and a protective film 6 provided on the multi-layered reflecting film, in which the protective film contains ruthenium (Ru), and at least one additive material selected from the group consisting of aluminum (Al), yttrium (Y), zirconium (Zr), rhodium (Rh) and hafnium (Hf), and the content of the additive material is 5 atom% or more and less than 50 atom% .SELECTED DRAWING: Figure 1

Description

The present invention relates to a reflective mask used for manufacturing a semiconductor device, a substrate with a multilayer reflective film used for manufacturing a reflective mask, and a reflective mask blank. The present invention also relates to a method for manufacturing a semiconductor device using the reflective mask.

With the recent demand for higher density and higher precision of VLSI devices, EUV lithography, which is an exposure technique using extreme ultraviolet (hereinafter referred to as EUV) light, is expected to be promising. EUV light refers to light in the wavelength band of the soft X-ray region or the vacuum ultraviolet region, and specifically refers to light having a wavelength of about 0.2 to 100 nm.

The reflective mask is an absorber which is a multilayer reflective film formed on a substrate for reflecting exposure light and a patterned absorber film formed on the multilayer reflective film for absorbing exposure light. Has a pattern. The light incident on the reflective mask mounted on the exposure machine for pattern transfer on the semiconductor substrate is absorbed in the portion having the absorber pattern and reflected by the multilayer reflective film in the portion without the absorber pattern. The light image reflected by the multilayer reflective film is transferred onto a semiconductor substrate such as a silicon wafer through a reflective optical system.

In order to achieve high density and high accuracy of the semiconductor device by using the reflective mask, the reflective region (surface of the multilayer reflective film) in the reflective mask has high reflectance with respect to the UV light which is the exposure light. It is necessary to prepare.

As the multilayer reflective film, a multilayer film in which elements having different refractive indexes are periodically laminated is generally used. For example, as the multilayer antireflection film for EUV light having a wavelength of 13 to 14 nm, a Mo / Si periodic laminated film in which Mo film and Si film are alternately laminated for about 40 cycles is preferably used.

Examples of the reflective mask used for EUV lithography include the reflective mask described in Patent Document 1. Patent Document 1 describes a substrate, a reflective layer formed of a multilayer film formed on the substrate and alternately laminated with two different types of films, and a buffer layer composed of a ruthenium film formed on the reflective layer. , A reflective photomask having an absorber pattern made of a material capable of absorbing soft X-rays formed on the buffer layer having a predetermined pattern shape is described. The buffer layer described in Patent Document 1 is also generally referred to as a protective film.

Patent Document 2 describes a substrate with a multilayer reflective film provided on the substrate with a multilayer reflective film that reflects exposure light. Further, in Patent Document 2, a protective film for protecting the multilayer reflective film is formed on the multilayer reflective film, and the protective film includes a reflectance reduction suppressing layer, a blocking layer, and an etching stopper layer. It is described that the protective film is formed by laminating and in this order. Further, in Patent Document 2, the etching stopper layer is made of ruthenium (Ru) or an alloy thereof, and specific examples of the ruthenium alloy include ruthenium niobium (RuNb) alloy and ruthenium zirconium (RuZr) alloy. , Ruthenium rhodium (RuRh) alloy, ruthenium cobalt (RuCo) alloy, ruthenium renium (RuRe) alloy are described.

Patent Documents 3 and 4 describe a substrate with a multilayer reflective film having a substrate, a multilayer reflective film, and a Ru-based protective film formed on the multilayer reflective film for protecting the multilayer reflective film. .. Patent Documents 3 and 4 describe that the surface layer of the multilayer reflective film on the opposite side to the substrate is a layer containing Si.

Patent Document 3 describes that a block layer that prevents the transfer of Si to the Ru-based protective film is provided between the multilayer reflective film and the Ru-based protective film. In Patent Document 3, Ru and its alloy material can be mentioned as the constituent material of the Ru-based protective film 18, and Ru and Nb, Zr, Rh, Ti, Co and Re are used as the alloy of Ru. It is described that a Ru compound having at least one metal element selected from the above group is suitable.

Further, Patent Document 4 describes that the Ru-based protective film contains a Ru compound containing Ru and Ti, and the Ru compound contains more Ru than RuTi having a stoichiometric composition.

JP-A-2002-122981 Japanese Unexamined Patent Publication No. 2014-170931 International Publication No. 2015/012151 International Publication No. 2015/037564

In the process of manufacturing the reflective mask, the absorber film is etched through the resist film and / or the etching mask film when the absorber pattern is formed. In order to make the shape of the absorber pattern as designed, it is necessary to perform a slight overetching when etching the absorber film. Therefore, the film under the absorber film (the film on the substrate side) is also etched. A protective film is provided to prevent the multilayer reflective film under the absorber film from being damaged during overetching of the absorber film. Therefore, the protective film is required to have high resistance to the etching gas of the absorber film.

For example, Ru or RuNb is used as the material of the protective film having high resistance to the etching gas of the absorber film. When the etching mask film formed on the absorber film is a Cr-based material, a mixed gas of chlorine gas and oxygen gas is used as the etching gas in order to peel off the etching mask film. The protective films of Ru and RuNb have low resistance to mixed gases including oxygen gas. Therefore, when the etching mask film is peeled off, the multilayer reflective film formed under the protective film may be damaged. In addition, the protective film damaged when the etching mask film is peeled off may not have sufficient resistance in the subsequent step of modifying the absorber pattern.

In EUV lithography for manufacturing semiconductor devices, there are few substances that are transparent to the exposure light. Therefore, the EUV pellicle for preventing foreign matter from adhering to the mask pattern surface of the reflective mask is not technically easy. Further, in EUV lithography, exposure contamination such as carbon film deposition on the mask and oxide film growth occurs due to EUV exposure. Therefore, when the mask is used in the manufacture of a semiconductor device, it is necessary to frequently perform cleaning with a cleaning solution such as sulfuric acid hydrogen peroxide (SPM) to remove foreign substances and contamination on the mask. However, the protective films of Ru and RuNb have a problem that they are not sufficiently resistant to SPM cleaning.

Thin films made of Ru and RuNb are easy to crystallize and have high crystallinity. A thin film with high crystallinity is inferior in density to an amorphous thin film. Therefore, it is considered that the protective film made of Ru and RuNb has a low resistance to a predetermined etching gas, and has a problem that the resistance to cleaning such as SPM cleaning is not sufficient.

Therefore, an object of the present invention is to provide a reflective mask having a protective film having high resistance to etching gas and high resistance to cleaning. Another object of the present invention is to provide a substrate with a multilayer reflective film and a reflective mask blank for producing a reflective mask having a protective film having high resistance to etching gas and high resistance to cleaning.

In order to solve the above problems, the present invention has the following configurations.

(Structure 1)
The configuration 1 of the present invention is a substrate with a multilayer reflective film having a substrate, a multilayer reflective film provided on the substrate, and a protective film provided on the multilayer reflective film.
The protective film comprises ruthenium (Ru) and at least one additive material selected from aluminum (Al), yttrium (Y), zirconium (Zr), rhodium (Rh) and hafnium (Hf). The substrate with a multilayer reflective film is characterized in that the content of the material is 5 atomic% or more and less than 50 atomic%.

(Structure 2)
In the configuration 2 of the present invention, the protective film includes a first layer and a second layer from the substrate side.
The first layer is ruthenium (Ru), magnesium (Mg), aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), germanium (Ge), zirconium (Zr), niobium ( Containing at least one selected from Nb), molybdenum (Mo), rhodium (Rh), hafnium (Hf) and tungsten (W).
The second layer is the substrate with a multilayer reflective film according to the first configuration, which comprises the ruthenium (Ru) and the additive material.

(Structure 3)
The substrate with a multilayer reflective film of configuration 3 of the present invention is characterized in that the protective film, the first layer, or the second layer further contains nitrogen (N). It is a board with.

(Structure 4)
The configuration 4 of the present invention is a substrate with a multilayer reflective film according to any one of configurations 1 to 3, wherein the Ru content of the second layer is smaller than the Ru content of the first layer. ..

(Structure 5)
Configuration 5 of the present invention is a reflective mask blank having an absorber film on the protective film of the substrate with a multilayer reflective film according to any one of configurations 1 to 4.

(Structure 6)
Configuration 6 of the present invention is a reflective mask blank of Configuration 5, characterized in that an etching mask film containing chromium (Cr) is contained on the absorber film.

(Structure 7)
Configuration 7 of the present invention is a reflective mask characterized in that the absorber film in the reflective mask blank of configuration 5 or 6 contains a patterned absorber pattern.

(Structure 8)
In the configuration 8 of the present invention, the etching mask film of the reflective mask blank of the configuration 6 is patterned to form an etching mask pattern.
Using the etching mask pattern as a mask, the absorber film is patterned to form an absorber pattern.
This is a method for manufacturing a reflective mask, which comprises removing the etching mask pattern with a mixed gas of a chlorine-based gas and an oxygen gas.

(Structure 9)
Configuration 9 of the present invention includes a step of setting the reflective mask of Configuration 7 in an exposure apparatus having an exposure light source that emits EUV light, and transferring the transfer pattern to a resist film formed on a substrate to be transferred. This is a method for manufacturing a semiconductor device.

According to the present invention, it is possible to provide a reflective mask having a protective film having high resistance to etching gas and high resistance to cleaning. Further, according to the present invention, it is possible to provide a substrate with a multilayer reflective film and a reflective mask blank for producing a reflective mask having a protective film having high resistance to etching gas and high resistance to cleaning.

It is sectional drawing of an example of the substrate with a multilayer reflective film of this embodiment. It is sectional drawing of another example of the substrate with the multilayer reflective film of this embodiment. It is sectional drawing of an example of the reflective mask blank of this embodiment. It is sectional drawing of another example of the reflective mask blank of this embodiment. It is a figure which shows the relationship between the content of Rh and the etching ray of the protective film by a mixed gas. It is a figure which shows the measurement result of the diffraction X-ray intensity (CPS) with respect to the diffraction angle 2θ. It is a figure which shows the measurement result of the diffraction X-ray intensity (CPS) with respect to the diffraction angle 2θ about the film which introduced nitrogen (N) at the time of film formation. It is a process drawing which showed an example of the manufacturing method of the reflection type mask of this embodiment by the sectional schematic drawing.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. It should be noted that the following embodiments are embodiments for specifically explaining the present invention, and do not limit the present invention to the scope thereof.

FIG. 1 is a schematic cross-sectional view showing an example of the substrate 110 with a multilayer reflective film of the present embodiment. The substrate 110 with a multilayer reflective film shown in FIG. 1 includes a multilayer reflective film 5 and a protective film 6. The substrate 110 with a multilayer reflective film may further have another thin film such as the back surface conductive film 2.

FIG. 2 is a schematic cross-sectional view of the substrate 110 with a multilayer reflective film similar to that of FIG. However, in the substrate 110 with the multilayer reflective film shown in FIG. 2, the protective film 6 includes the first layer 62 and the second layer 64.

FIG. 3 is a schematic cross-sectional view showing an example of the reflective mask blank 100 of the present embodiment. The reflective mask blank 100 shown in FIG. 3 includes a back surface conductive film 2, a multilayer reflective film 5, a protective film 6, and an absorber film 7. The reflective mask blank 100 may further have another thin film such as a resist film 8.

FIG. 4 is a schematic cross-sectional view showing an example of a reflective mask blank 100 further provided with an etching mask film 9 in addition to the configuration shown in FIG. The reflective mask blank 100 may further have another thin film such as a resist film 8.

In the present specification, among the main surfaces of the mask blank substrate 1, the main surface on which the multilayer reflective film 5 is formed may be referred to as a "front main surface" (or "first main surface"). Further, the main surface on which the multilayer reflective film 5 is not formed may be referred to as a "back side main surface" (or "second main surface"). The back surface conductive film 2 is formed on the "back side main surface" (or "second main surface").

In the present specification, "providing (having) a predetermined thin film on the main surface of the mask blank substrate 1" means that the predetermined thin film is arranged in contact with the main surface of the mask blank substrate 1. In addition to the case of meaning, the case of having another film between the mask blank substrate 1 and the predetermined thin film is also included. Further, for example, "having a film B on the film A" means that the film A and the film B are arranged so as to be in direct contact with each other, and another film between the film A and the film B. Including the case of having a film. Further, in the present specification, for example, "the film A is arranged in contact with the surface of the film B" means that the film A and the film B are placed between the film A and the film B without interposing another film. It means that they are arranged so as to be in direct contact with each other.

Next, the surface roughness (Rms), which is a parameter indicating the surface morphology of the mask blank substrate 1 and the surface morphology of the surface of the thin film constituting the reflective mask blank 100 and the like, will be described.

Rms (Root mean square), which is a typical index of surface roughness, is the root mean square roughness, which is the square root of the value obtained by averaging the squares of the deviations from the mean line to the measurement curve. Rms is expressed by the following equation (1).

式（１）において、ｌは基準長さであり、Ｚは平均線から測定曲線までの高さである。

In formula (1), l is the reference length and Z is the height from the average line to the measurement curve.

Rms has been conventionally used for controlling the surface roughness of the mask blank substrate 1, and the surface roughness can be grasped numerically.

<Substrate 110 with multilayer reflective film>
The substrate 1 constituting the substrate 110 with a multilayer reflective film, which is a kind of the substrate 1 with a thin film of the present embodiment, and each thin film will be described.

<< Board 1 >>
The substrate 1 in the substrate 110 with a multilayer reflective film of the present embodiment needs to prevent the occurrence of the absorber pattern 7a distortion due to heat during EUV exposure. Therefore, as the substrate 1, a substrate 1 having a low coefficient of thermal expansion within the range of 0 ± 5 ppb / ° C. is preferably used. As a material having a low coefficient of thermal expansion in this range, for example, SiO _2- TiO _2- based glass, multi-component glass ceramics, or the like can be used.

The first main surface (front side main surface) on the side where the transfer pattern of the substrate 1 (the absorber film 7 described later constitutes this) is predetermined from the viewpoint of obtaining at least the pattern transfer accuracy and the position accuracy. The surface is processed so that it becomes flat. In the case of EUV exposure, the flatness is preferably 0.1 μm or less, more preferably 0.05 μm or less, and further preferably 0.05 μm or less in the region of 132 mm × 132 mm of the first main surface on the side where the transfer pattern of the substrate 1 is formed. It is preferably 0.03 μm or less. The second main surface (back side main surface) opposite to the side on which the absorber film 7 is formed is a surface that is electrostatically chucked when set in the exposure apparatus. The flatness of the second main surface is preferably 0.1 μm or less, more preferably 0.05 μm or less, still more preferably 0.03 μm or less in a region of 132 mm × 132 mm. The flatness of the second main surface of the reflective mask blank 100 is preferably 1 μm or less, more preferably 0.5 μm or less, still more preferably 0.3 μm or less in the region of 142 mm × 142 mm. Is.

Further, the high surface smoothness of the substrate 1 is also an extremely important item. The surface roughness of the first main surface on which the absorber pattern 7a for transfer is formed is preferably 0.15 nm or less in root mean square roughness (Rms), and more preferably 0.10 nm or less in Rms. The surface smoothness can be measured with an atomic force microscope.

Further, the substrate 1 preferably has high rigidity in order to prevent deformation of the film (multilayer reflective film 5 or the like) formed on the substrate 1 due to film stress. In particular, the substrate 1 preferably has a high Young's modulus of 65 GPa or more.

<< Undercoat >>
The substrate 110 with a multilayer reflective film of the present embodiment can have a base film in contact with the surface of the substrate 1. The base film is a thin film formed between the substrate 1 and the multilayer reflective film 5. By having the base film, it is possible to prevent charge-up at the time of mask pattern defect inspection by an electron beam, reduce the phase defects of the multilayer reflective film 5, and obtain high surface smoothness.

As the material of the base film, a material containing ruthenium or tantalum as a main component is preferably used. For example, Ru metal alone or Ta metal alone may be used, and Ru or Ta may be titanium (Ti), niobium (Nb), molybdenum (Mo), zirconium (Zr), ruthenium (Y), boron (B), or lanthanum (La). ), Cobalt (Co), and / or a Ru alloy or Ta alloy containing a metal such as ruthenium (Re). The film thickness of the base film is preferably in the range of, for example, 1 nm to 10 nm.

<< Multilayer Reflective Film 5 >>

The substrate 110 with a multilayer reflective film of the embodiment includes the multilayer reflective film 5. The multilayer reflective film 5 imparts a function of reflecting EUV light in the reflective mask 200. The multilayer reflective film 5 is a multilayer film in which each layer containing elements having different refractive indexes as main components is periodically laminated.

Generally, as the multilayer reflective film 5, a thin film of a light element or a compound thereof (high refractive index layer) which is a high refractive index material and a thin film of a heavy element or a compound thereof which is a low refractive index material (low refractive index layer). ) And are alternately laminated for about 40 to 60 cycles, and a multilayer film is used.

The multilayer film used as the multilayer reflective film 5 is formed by laminating a laminated structure of a high refractive index layer / a low refractive index layer in which a high refractive index layer and a low refractive index layer are laminated in this order from the substrate 1 side for a plurality of cycles. Alternatively, the laminated structure of the low refractive index layer / high refractive index layer in which the low refractive index layer and the high refractive index layer are laminated in this order from the substrate 1 side may be laminated for a plurality of cycles. The outermost surface layer of the multilayer reflective film 5, that is, the surface layer of the multilayer reflective film 5 on the side opposite to the substrate 1 side is preferably a high refractive index layer. In the above-mentioned multilayer film, when the laminated structure of the high refractive index layer / low refractive index layer in which the high refractive index layer and the low refractive index layer are laminated in this order from the substrate 1 side is laminated for a plurality of cycles, the uppermost layer is It becomes a low refractive index layer. In this case, if the low refractive index layer constitutes the outermost surface of the multilayer reflective film 5, it is easily oxidized and the reflectance of the reflective mask 200 decreases. Therefore, it is preferable to further form a high refractive index layer on the uppermost low refractive index layer to form the multilayer reflective film 5. On the other hand, in the above-mentioned multilayer film, when the laminated structure of the low refractive index layer / high refractive index layer in which the low refractive index layer and the high refractive index layer are laminated in this order from the substrate 1 side is set as one cycle, it is the most. The upper layer is a high refractive index layer. Therefore, in this case, it is not necessary to form a further high refractive index layer.

As the high refractive index layer, a layer containing silicon (Si) can be used. As a material containing Si, a Si compound containing boron (B), carbon (C), nitrogen (N), oxygen (O) and / or hydrogen (H) may be used in addition to Si alone. it can. By using a high refractive index layer containing Si, a reflective mask 200 having excellent reflectance of EUV light can be obtained. Further, as the low refractive index layer, a simple substance of a metal selected from molybdenum (Mo), ruthenium (Ru), rhodium (Rh), and platinum (Pt), or an alloy thereof can be used. Further, boron (B), carbon (C), nitrogen (N), oxygen (O) and / or hydrogen (H) may be added to these metal simple substances or alloys. In the substrate 110 with a multilayer reflective film of the present embodiment, it is preferable that the low refractive index layer is a molybdenum (Mo) layer and the high refractive index layer is a silicon (Si) layer. For example, as the multilayer reflective film 5 for reflecting EUV light having a wavelength of 13 nm to 14 nm, a Mo / Si periodic laminated film in which Mo layers and Si layers are alternately laminated for about 40 to 60 cycles is preferably used. The high-refractive index layer, which is the uppermost layer of the multilayer reflective film 5, is formed of silicon (Si), and a silicon oxide layer containing silicon and oxygen is formed between the uppermost layer (Si) and the protective film 6. can do. In the case of this structure, the mask cleaning resistance can be improved.

The reflectance of the multilayer reflective film 5 alone is usually 65% or more, and the upper limit is usually 73%. The film thickness and period of each constituent layer of the multilayer reflective film 5 can be appropriately selected depending on the exposure wavelength. Specifically, the film thickness and period of each constituent layer of the multilayer reflective film 5 can be selected so as to satisfy Bragg's reflection law. In the multilayer reflective film 5, there are a plurality of high refractive index layers and a plurality of low refractive index layers, but the film thickness of the high refractive index layers or the film thickness of the low refractive index layers does not necessarily have to be the same. Further, the film thickness of the Si layer on the outermost surface of the multilayer reflective film 5 can be adjusted within a range that does not reduce the reflectance. The film thickness of Si (high refractive index layer) on the outermost surface can be 3 nm to 10 nm.

A method for forming the multilayer reflective film 5 is known in the art, but it can be formed by forming each layer by, for example, an ion beam sputtering method. In the case of the Mo / Si periodic laminated film described above, for example, by the ion beam sputtering method, a Si film having a thickness of about 4 nm is first formed on the substrate 1 using a Si target, and then a thickness of 3 nm is formed using the Mo target. A Mo film of about the same degree is formed, and this is set as one cycle and laminated for 40 to 60 cycles to form a multilayer reflective film 5 (the outermost layer is a Si film). When 60 cycles are used, the number of steps increases from 40 cycles, but the reflectance to EUV light can be increased.

<< Protective film 6 >>
As shown in FIGS. 1 and 2, the substrate 110 with a multilayer reflective film of the present embodiment has a protective film 6 on the multilayer reflective film 5. By having the protective film 6 on the multilayer reflective film 5, it is possible to suppress damage to the surface of the multilayer reflective film 5 when the reflective mask 200 is manufactured by using the substrate 110 with the multilayer reflective film. Therefore, the reflectance characteristic of the obtained reflective mask 200 with respect to EUV light becomes good.

The protective film 6 of the present embodiment contains ruthenium (Ru) and an additive material. The additive material is at least one additive material selected from aluminum (Al), yttrium (Y), zirconium (Zr), rhodium (Rh) and hafnium (Hf). A thin film made of Ru is easy to crystallize and has high crystallinity, and a thin film having high crystallinity is inferior in density to an amorphous thin film. Therefore, when the protective film 6 contains an additive material, the density of the protective film 6 can be increased, and the resistance of the protective film 6 to the etching gas and the resistance to cleaning can be increased. The protective film 6 is a protective film 6 corresponding to the second layer 64, which will be described later. As will be described later, the protective film 6 may further include a first layer 62 in addition to the protective film 6 corresponding to the second layer 64 (see, for example, FIG. 2).

The content of the additive material in the protective film 6 of the present embodiment is 5 atomic% or more and less than 50 atomic%. The content of the additive material is preferably 10 atomic% or more, more preferably 20 atomic% or more. The content of the additive material is preferably 40 atomic% or less, more preferably 35 atomic% or less. By adjusting the amount of the added material added, it is possible to form the protective film 6 which has high resistance to etching gas and SPM cleaning and does not significantly reduce the reflectance of EUV. Therefore, when the content of the additive material in the protective film 6 is within a predetermined range, the decrease in the reflectance of EUV light of the multilayer reflective film 5 with the protective film 6 is suppressed, and the resistance to etching gas and cleaning is improved. Can be high. Further, in the case of an additive material having an extinction coefficient k higher than that of ruthenium (Ru), it is preferable to adjust the extinction coefficient of the protective film 6 to be 0.030 or less, more preferably 0.025 or less. ..

The content of the additive material in the protective film 6 described above can be the content of the additive material in the second layer 64, which will be described later. That is, the content of the additive material in the second layer 64 can be 5 atomic% or more and less than 50 atomic%. The content of the additive material is preferably 10 atomic% or more, more preferably 20 atomic% or more. The content of the additive material is preferably 40 atomic% or less, more preferably 35 atomic% or less.

Next, the case where the additive material contained in the protective film 6 is aluminum (Al), yttrium (Y), zirconium (Zr), rhodium (Rh) and hafnium (Hf) will be described. The protective film 6 described below can be the second layer 64 described later.

When aluminum (Al) is added as an additive material to ruthenium (Ru) as the material of the protective film 6 (or the second layer 64) (for example, in the case of the RuAl film), the chlorine-based gas and oxygen of the protective film 6 Etching resistance to mixed gas, etching resistance to fluorine gas, and sulfuric acid overwater (SPM) cleaning resistance are improved. If the Al concentration in the protective film 6 is too small, the effect of addition cannot be obtained, and if it is too large, the extinction coefficient of the protective film 6 with respect to EUV light becomes high, and the reflectance of the reflective mask 200 decreases. Further, if the Al concentration is too high, the resistance to fluorine gas decreases. Therefore, the Al concentration in the protective film 6 is preferably 5 atomic% or more and 40 atomic% or less, and more preferably 10 atomic% or more and 25 atomic% or less.

When ittrium (Y) is added as an additive material to ruthenium (Ru) as the material of the protective film 6 (or the second layer 64) (for example, in the case of the RuY film), the chlorine-based gas and oxygen of the protective film 6 Etching resistance to mixed gas and etching resistance to fluorine-based gas are increased. If the Y concentration in the protective film 6 is too small, the effect of addition cannot be obtained, and if it is too large, the sulfuric acid hydrogen peroxide (SPM) washing resistance of the protective film 6 decreases. Therefore, the Y concentration in the protective film 6 is preferably 5 atomic% or more and less than 50 atomic%, and more preferably 10 atomic% or more and 40 atomic% or less.

When zirconium (Zr) is added as an additive material to ruthenium (Ru) as the material of the protective film 6 (or the second layer 64) (for example, in the case of RuZr film), the chlorine-based gas and oxygen of the protective film 6 Etching resistance of gas to mixed gas is improved. If the Zr concentration in the protective film 6 is too small, the effect of addition cannot be obtained, and if it is too large, the sulfuric acid hydrogen peroxide (SPM) washing resistance of the protective film 6 decreases. Further, if the Zr concentration is too high, the resistance to chlorine-based gas decreases. Therefore, the Zr concentration in the protective film 6 is preferably 5 atomic% or more and 45 atomic% or less, and more preferably 10 atomic% or more and 25 atomic% or less.

When rhodium (Rh) is added as an additive material to ruthenium (Ru) as the material of the protective film 6 (or the second layer 64) (for example, in the case of the RuRh film), the chlorine-based gas and oxygen of the protective film 6 Etching resistance to mixed gas, etching resistance to chlorine-based gas, etching resistance to fluorine-based gas, and sulfuric acid superwater (SPM) cleaning resistance are improved. If the Rh concentration in the protective film 6 is too small, the effect of addition cannot be obtained, and if it is too large, the extinction coefficient k of the protective film 6 with respect to EUV light becomes high, so that the reflectance of the reflective mask 200 decreases. Therefore, the Rh concentration in the protective film 6 is preferably 15 atomic% or more and less than 50 atomic%, and more preferably 20 atomic% or more and 40 atomic% or less.
FIG. 5 shows the etching rate (nm / s: vertical axis) of the protective film by the Rh content (atomic%: horizontal axis) and the mixed gas (Cl ₂ + O _{2 gas) when Rh is added to Ru as an additive material.} ) Is shown. When the Rh content is 20 atomic% or more, the rate of decrease in the etching rate begins to decrease, when it is 30 atomic% or more, the tendency becomes larger, and when it is 50 atomic% or more, the etching rate hardly changes. From this, it can be seen that the etching resistance of the protective film can be improved by increasing the Rh content. Therefore, it is preferable to increase the Rh content until the rate at which the etching rate decreases begins to decrease. However, since the etching rate hardly changes when the Rh content exceeds 50 atomic%, it is not necessary to increase the Rh content any more. Further, when the Rh content is increased, the reflectance is lowered, and when the Rh content exceeds 50 atomic%, the desired reflectance cannot be obtained. Therefore, the Rh content is less than 50 atomic%. Is preferable. As described above, based on the obtained knowledge, an excellent substrate with a multilayer reflective film can be obtained by considering the improvement of etching resistance and the decrease of reflectance due to the addition of Rh.

When the protective film 6 (also the second layer 64) contains ruthenium (Ru) and rhodium (Rh), the following conditions are preferable. In the present specification, the peak detected by the X-ray diffraction method is a peak when the measurement data of the diffracted X-ray intensity with respect to the diffraction angle 2θ using CuKα rays is illustrated, and is the measurement data (diffraction X-ray spectrum). The height of the peak when the background is subtracted from) can be assumed to be at least twice the magnitude of the background noise near the peak (width in the noise height direction). The diffraction angle 2θ of the peak can be a diffraction angle 2θ (angle formed by the incident X-ray direction and the diffraction X-ray direction) indicating the maximum value of the peak when the background is subtracted from the measurement data.
In FIG. 6, a single film of ruthenium (Ru) (in parentheses indicates the direction of the crystal), a single film of rhodium (Rh), and a RuRh film (Ru: Rh = 70: 30, Ru: Rh = 50: 50). , Ru: Rh = 30: 70), the result of measuring the diffraction X-ray intensity (CPS) (vertical axis) with respect to the diffraction angle 2θ (horizontal axis) by the X-ray diffraction method using CuKα rays. Is shown. Both the ruthenium (Ru) single film and the rhodium (Rh) single film show a relatively high CPS with respect to the diffraction angle 2θ. It can be seen that the single film has a relatively high crystallinity. In the RuRh film, the CPS for the diffraction angle 2θ changes depending on the ratio of Ru and Rh, and when Ru: Rh = 30: 70, the CPS for the diffraction angle 2θ is the lowest. From this, it can be seen that in the RuRh film, the higher the Rh content, the lower the crystallinity and the higher the denseness. However, when the Rh content increases, the reflectance decreases, and when the Rh content exceeds 50 atomic%, the desired reflectance cannot be obtained. Therefore, the Rh content should be less than 50 atomic%. Is preferable as described above.
Further, as shown in FIG. 6, when Ru: Rh = 70: 30, the diffraction angle is 42.0 degrees and the half width is 0.62, and when Ru: Rh = 50: 50, the diffraction angle is 41.9 degrees and half. The value width was 0.64, and at Ru: Rh = 30: 70, the diffraction angle was 41.7 degrees and the half width was 0.75.
It is preferable that the diffraction angle 2θ has a peak in the range of 41.0 degrees or more and 43.0 degrees or less, and the half width of the peak is 0.6 degrees or more. This is because the half-value width of a single film of ruthenium (Ru (002)) is a little less than 0.6 degrees, and if the half-value width is less than 0.6 degrees, the crystallinity becomes high, which is not preferable. When the half width of the peak is less than 0.6 degrees, the crystallinity becomes high and the density is lost, so that the etching resistance and the cleaning resistance become low.
In this way, the crystallinity can be controlled by the range of the diffraction angle 2θ of the peak and the half width of the peak. By controlling the crystallinity, the resistance to a predetermined etching gas can be increased, and the cleaning resistance to SPM and the like can be increased. The peak diffraction angle 2θ is preferably 41.0 degrees or more, more preferably 41.3 degrees or more. The peak diffraction angle 2θ is preferably 43.0 degrees or less, more preferably 42.0 degrees or less. The half width of the peak is preferably 0.6 degrees or more, and more preferably 0.65 degrees or more. The half width of the peak is preferably 0.8 degrees or less.

FIG. 7 shows three types of films into which nitrogen (N) was introduced when the RuRh film (Ru: Rh = 70: 30) was formed (the amount of N introduced is 3 sccm, 6 sccm, and 12 sccm, respectively). , The result of measuring the diffraction X-ray intensity (CPS) with respect to the diffraction angle 2θ by the X-ray diffraction method using CuKα ray is shown. As shown in FIG. 7, when the introduction amount of N is 3 sccm, the diffraction angle is 41.9 degrees and the half width is 0.68, and when the introduction amount of N is 6 sccm, the diffraction angle is 41.8 degrees and the half width is 0.68. It was 0.68, and when the amount of N introduced was 12 sccm, the diffraction angle was 41.6 degrees and the half width was 0.78. The other membranes are the same as the measurement results of FIG. The diffraction angle 2θ of the peak of the RuRh film (Ru: Rh = 70: 30) is theoretically expected to be 41.8 degrees. It can be seen that by adding nitrogen, the density of the protective film can be increased and the diffraction angle 2θ of the peak of the protective film can be brought close to 41.8 degrees. By bringing the diffraction angle 2θ of the peak of the protective film close to 41.8 degrees, it is possible to reduce the residual stress in the protective film.
From this, when the protective film 6 (also the second layer 64) contains ruthenium (Ru) and rhodium (Rh), it is preferable that the protective film further contains nitrogen (N). By including N, the crystallinity of the protective film can be reduced and the denseness can be improved. In addition, nitrogen is present at the interface between the protective film and the film above the protective film and / or the film below the protective film, and by reducing the residual stress in the protective film, their adhesion is improved. It can be improved and the cleaning resistance can be improved. Furthermore, by improving the adhesion, blister resistance (for example, when hydrogen gas is introduced into the atmosphere during exposure, the phenomenon in which the absorber film floats up from the surface of the protective film and peels off is called "blister"). Can be improved.

When hafnium (Hf) is added as an additive material to ruthenium (Ru) as the material of the protective film 6 (or the second layer 64) (for example, in the case of RuHf film), the chlorine-based gas and oxygen of the protective film 6 Etching resistance to mixed gas and sulfuric acid overwater (SPM) cleaning resistance are improved. If the Hf concentration in the protective film 6 is too small, the effect of addition cannot be obtained, and if it is too large, the extinction coefficient k of the protective film 6 with respect to EUV light becomes high, so that the reflectance of the reflective mask 200 decreases. Therefore, the Hf concentration in the protective film 6 is preferably 5 atomic% or more and 30 atomic% or less, and more preferably 10 atomic% or more and 25 atomic% or less.

As shown in FIG. 2, the protective film 6 of the substrate 110 with a multilayer reflective film of the present embodiment preferably includes a first layer 62 and a second layer 64 from the substrate 1 side. When the protective film 6 includes the first layer 62 and the second layer 64, the second layer 64 can be the same thin film as the protective film 6 described above.

When the multilayer reflective film 5 is a Mo / Si periodic laminated film, Mo is easily oxidized by the atmosphere, so that the reflectance of the multilayer reflective film 5 may decrease. Therefore, the uppermost layer of the multilayer reflective film 5 is made into a Si layer. When the Si film and the protective film 6 made of Ru are in contact with each other, silicon (Si) is easily diffused into the protective film 6. That is, Si from the Si layer of the multilayer reflective film 5 moves toward the Ru-based protective film 6 with the passage of time between the grain boundaries of the Ru-based protective film 6 and diffuses (and forms RuSiO (RuSi)). However, it reaches the surface layer of the Ru-based protective film 6 and undergoes an oxidation reaction with a cleaning liquid or gas to _{generate SiO 2.} Further, when the protective film 6 is not dense, the cleaning liquid or gas permeates into the protective film 6, and SiO ₂ is generated in the protective film 6 (inside or below the protective film 6). Since the adhesion between Ru and SiO ₂ is low, the film may peel off due to repeated cleaning in the manufacturing process of the reflective mask 200 or in use after the product is completed. .. Since the protective film 6 has a predetermined first layer 62, it is possible to prevent silicon (Si) from diffusing from the multilayer reflective film 5 to the protective film 6.

In order to prevent silicon (Si) from diffusing from the multilayer reflective film 5 to the protective film 6, the first layer 62 is composed of ruthenium (Ru), magnesium (Mg), aluminum (Al), and titanium (Ti). , Vanadium (V), Chromium (Cr), Germanium (Ge), Zirconium (Zr), Niobium (Nb), Molybdenum (Mo), Rodium (Rh), Hafnium (Hf) and Tungsten (W). It is preferable to include one. In particular, when the first layer 62 is a RuTi film, a RuZr film, or a RuAl film, the diffusion of silicon (Si) into the protective film 6 can be more reliably suppressed.

The proportion of Ru in the Ru compound of the first layer 62 is preferably more than 50 atomic% and less than 100 atomic%, more preferably 80 atomic% or more and less than 100 atomic%, and more than 95 atomic%. It is particularly preferably less than 100 atomic%.

When the protective film 6 includes the first layer 62 and the second layer 64, the second layer 64 can be the same thin film as the protective film 6 described above. That is, the second layer 64 contains ruthenium (Ru) and at least one additive material selected from aluminum (Al), yttrium (Y), zirconium (Zr), rhodium (Rh) and hafnium (Hf). Can include. Further, the first layer 62 and the second layer 64 may be made of the same material having different composition ratios from each other.

When the first layer 62 is a RuTi-containing film (for example, a RuTi film, a RuTiN film, the same applies to other RuY-containing films, etc.), the second layer 64 is a RuY-containing film, a RuZr-containing film, or a RuZr-containing film. A RuRh-containing film is preferable. When the first layer 62 is a RuZr-containing film, it is preferable that the second layer 64 is a RuAl-containing film, a RuY-containing film, a RuZr-containing film, or a RuRh-containing film. In this case, the first layer 62 can more reliably suppress the diffusion of silicon (Si) into the protective film 6, and the second layer 64 makes the protective film 6 resistant to etching gas and cleaning. Can be raised more reliably.

The protective film 6 (first layer 62 and / or second layer 64) includes at least one selected from N, C, O, H and B to the extent that the effects of the present embodiment can be obtained. Can be done. The protective film 6 (first layer 62 and / or second layer 64) preferably contains nitrogen (N) and / or oxygen (O) in order to reduce the crystallinity of the thin film and make it amorphous.

The protective film 6 (first layer 62 and / or second layer 64) of the substrate 110 with the multilayer reflective film of the present embodiment preferably further contains nitrogen (N). Crystallinity can be reduced by further containing nitrogen (N) in the protective film 6 (first layer 62 and / or second layer 64). As a result, the thin film can be densified, so that the resistance to etching gas and cleaning can be further increased. The proportion of N in the Ru compound of the protective film 6 (first layer 62 and / or second layer 64) is preferably greater than 1 atomic% and 20 atomic% or less, and more preferably 3 atomic% or more and 10 atoms. % Or less is preferable.

The protective film 6 (first layer 62 and / or second layer 64) of the substrate 110 with the multilayer reflective film of the present embodiment preferably further contains oxygen (O). Crystallinity can be reduced by further containing oxygen (O) in the protective film 6 (first layer 62 and / or second layer 64). As a result, the thin film can be densified, so that the resistance to etching gas and cleaning can be further increased. The proportion of O in the Ru compound of the protective film 6 (first layer 62 and / or second layer 64) is preferably greater than 1 atomic% and 20 atomic% or less, and more preferably 3 atomic% or more and 10 atoms. % Or less is preferable.

In the substrate 110 with the multilayer reflective film of the present embodiment, the Ru content of the second layer 64 is preferably smaller than the Ru content of the first layer 62. For example, when the first layer 62 is a RuTi film and the second layer 64 is a RuRh film, the first layer 62 is a protective film of silicon (Si) even if the Ti content of the RuTi film is relatively low. Diffusion to 6 can be suppressed. Therefore, the Ru content of the second layer 64 is smaller than the Ru content of the first layer 62, so that the resistance to etching gas and cleaning is further increased, and the silicon (Si) is applied to the protective film 6. Diffusion can be suppressed.

In the substrate 110 with a multilayer reflective film of the present embodiment, the refractive index of the second layer 64 is preferably smaller than the refractive index of the first layer 62. As a result, a substrate with a protective film (a substrate 110 with a multilayer reflective film having the protective film 6) can be produced without lowering the reflectance of EUV light from the multilayer reflective film 5 including the protective film 6. The refractive index of the second layer 64 is preferably 0.920 or less, more preferably 0.885 or less.

The protective film 6 (first layer 62 and / or second layer 64) can be formed by various known methods. Examples of the method of the protective film 6 include an ion beam sputtering method, a sputtering method, a reactive sputtering method, a chemical vapor deposition method (CVD), and a vacuum vapor deposition method. When the first layer 62 is formed by the ion beam sputtering method, it is preferable because the first layer 62 can be continuously formed after the multi-layer reflective film 5 is formed. Further, when the protective film 6 (first layer 62 and / or second layer 64) contains nitrogen and / or oxygen, a reactive sputtering method may be used to obtain a stable film formation. preferable.

When the protective film 6 includes the first layer 62 and the second layer 64, heat treatment is performed after forming the first layer 62 and the second layer 64 or after forming the absorber film 7. Can be done. In this heat treatment, heating can be performed at a temperature higher than the prebaking temperature (about 110 ° C.) of the resist film 8 in the manufacturing process of the reflective mask blank 100. Specifically, the temperature condition of the heat treatment is usually 160 ° C. or higher and 300 ° C. or lower, and preferably 180 ° C. or higher and 250 ° C. or lower.

When the above heat treatment step is performed, at least a part of the metal constituting the first layer 62 is diffused into the second layer 64, and further, between the first layer 62 and the second layer 64, A substrate 110 with a multilayer reflective film having a composition gradient region in which the content of the metal component constituting the first layer 62 continuously decreases toward the second layer 64 is obtained.

The film thickness of the protective film 6 (the sum of the first layer 62 and the second layer 64) is not particularly limited as long as it can function as the protective film 6. From the viewpoint of the reflectance of EUV light, the film thickness of the protective film 6 is preferably 1.0 nm to 8.0 nm, and more preferably 1.5 nm to 6.0 nm. The film thickness of the first layer 62 is preferably 0.5 nm to 2.0 nm, more preferably 1.0 nm to 1.5 nm. The film thickness of the second layer 64 is preferably 1.0 nm to 7.0 nm, and more preferably 1.5 nm to 4.0 nm.

<Reflective mask blank 100>
The reflective mask blank 100 of the present embodiment will be described. The reflective mask blank 100 has an absorber film 7 on the protective film 6 of the substrate 110 with the multilayer reflective film described above.

<< Absorber Membrane 7 >>
The absorber film 7 of the reflective mask blank 100 of the present embodiment is formed on the multilayer reflective film 5 (in the case where the protective film 6 is formed, on the protective film 6). The basic function of the absorber membrane 7 is to absorb EUV light. The absorber film 7 may be an absorber film 7 for the purpose of absorbing EUV light, or may be an absorber film 7 having a phase shift function in consideration of the phase difference of EUV light. The absorber film 7 having a phase shift function absorbs EUV light and reflects a part of the EUV light to shift the phase. That is, in the reflective mask 200 in which the absorber film 7 having a phase shift function is patterned, the portion where the absorber film 7 is formed absorbs EUV light and dims, and the pattern transfer is not adversely affected. Reflects some light. Further, in the region (field portion) where the absorber film 7 is not formed, EUV light is reflected from the multilayer reflection film 5 via the protective film 6. Therefore, a desired phase difference is obtained between the reflected light from the absorber film 7 having the phase shift function and the reflected light from the field portion. The absorber film 7 having a phase shift function is formed so that the phase difference between the reflected light from the absorber film 7 and the reflected light from the multilayer reflective film 5 is 170 degrees to 190 degrees. The image contrast of the projected optical image is improved by the light having the inverted phase difference in the vicinity of 180 degrees interfering with each other at the pattern edge portion. As the image contrast is improved, the resolution is increased, and various exposure-related margins such as exposure amount margin and focal margin can be increased.

The absorber membrane 7 may be a single-layer membrane or a multilayer membrane composed of a plurality of membranes (for example, a lower-layer absorber membrane and an upper-layer absorber membrane). In the case of a single-layer film, the number of steps during mask blank manufacturing can be reduced and the production efficiency is improved. In the case of a multilayer film, its optical constant and film thickness can be appropriately set so that the upper layer absorber film becomes an antireflection film at the time of mask pattern defect inspection using light. This improves the inspection sensitivity at the time of mask pattern defect inspection using light. Further, when a membrane to which oxygen (O), nitrogen (N) or the like for improving oxidation resistance is added to the upper absorber membrane is used, the stability over time is improved. In this way, by making the absorber film 7 a multilayer film, it is possible to add various functions. When the absorber film 7 is an absorber film 7 having a phase shift function, the range of adjustment on the optical surface can be increased by forming a multilayer film, so that a desired reflectance can be easily obtained. Become.

The material of the absorber film 7 has a function of absorbing EUV light and can be processed by etching or the like (preferably, it can be etched by dry etching of chlorine (Cl) -based gas and / or fluorine (F) -based gas). The material is not particularly limited as long as it is a material having a high etching selectivity with respect to the protective film 6 (second layer 64). Those having such a function include palladium (Pd), silver (Ag), platinum (Pt), gold (Au), iridium (Ir), tungsten (W), chromium (Cr), cobalt (Co), and manganese. (Mn), tin (Sn), tantalum (Ta), vanadium (V), nickel (Ni), hafnium (Hf), iron (Fe), copper (Cu), tellurium (Te), zinc (Zn), magnesium (Mg), germanium (Ge), aluminum (Al), rhodium (Rh), ruthenium (Ru), molybdenum (Mo), niobium (Nb), titanium (Ti), zirconium (Zr), ittrium (Y), and At least one metal selected from silicon (Si), or compounds thereof, can be preferably used.

The absorber film 7 can be formed by a magnetron sputtering method such as a DC sputtering method and an RF sputtering method. For example, the absorber film 7 such as a tantalum compound can be formed into a film by a reactive sputtering method using a target containing tantalum and boron and using argon gas to which oxygen or nitrogen is added.

The tantalum compound for forming the absorber film 7 includes an alloy of Ta and the above-mentioned metal. When the absorber membrane 7 is an alloy of Ta, the crystalline state of the absorber membrane 7 is preferably an amorphous or microcrystalline structure from the viewpoint of smoothness and flatness. If the surface of the absorber film 7 is not smooth or flat, the edge roughness of the absorber pattern 7a may increase and the dimensional accuracy of the pattern may deteriorate. The surface roughness of the absorber film 7 is a root mean square roughness (Rms) of 0.5 nm or less, more preferably 0.4 nm or less, and further preferably 0.3 nm or less.

The tantalum compound for forming the absorber film 7 includes a compound containing Ta and B, a compound containing Ta and N, a compound containing Ta, O and N, Ta and B, and further O. Use a compound containing at least one of N, a compound containing Ta and Si, a compound containing Ta, Si and N, a compound containing Ta and Ge, a compound containing Ta, Ge and N, and the like. Can be done.

Ta is a material that has a large EUV light absorption coefficient and can be easily dry-etched with a chlorine-based gas or a fluorine-based gas. Therefore, it can be said that Ta is a material for the absorber membrane 7 having excellent processability. Further, by adding B, Si and / or Ge or the like to Ta, an amorphous material can be easily obtained. As a result, the smoothness of the absorber membrane 7 can be improved. Further, when N and / or O is added to Ta, the resistance of the absorber membrane 7 to oxidation is improved, so that the effect of improving the stability over time can be obtained.

<< Backside conductive film 2 >>
On the second main surface (back side main surface) of the substrate 1 (opposite the formation surface of the multilayer reflection film 5), and when an intermediate layer such as a hydrogen intrusion suppression film is formed on the substrate 1, the intermediate layer On the upper side), the back surface conductive film 2 for the electrostatic chuck is formed. The sheet resistance required for the back surface conductive film 2 for an electrostatic chuck is usually 100 Ω / □ (Ω / square) or less. The method for forming the back surface conductive film 2 is, for example, a magnetron sputtering method or an ion beam sputtering method using a target of a metal such as chromium or tantalum or an alloy thereof. The material containing chromium (Cr) in the back surface conductive film 2 is preferably a Cr compound containing at least one selected from boron, nitrogen, oxygen, and carbon in Cr. Examples of the Cr compound include CrN, CrON, CrCN, CrCON, CrBN, CrBON, CrBCN and CrBOCN. As the material containing tantalum (Ta) of the back surface conductive film 2, Ta (tantalum), an alloy containing Ta, or a Ta compound containing at least one of boron, nitrogen, oxygen, and carbon in any of these is used. It is preferable to use it. Examples of Ta compounds include TaB, TaN, TaO, TaON, TaCON, TaBN, TaBO, TaBON, TaBCON, TaHf, TaHfO, TaHfN, TaHfON, TaHfCON, TaSi, TaSiO, TaSiN, TaSiN, TaSiN, TaSiN, and TaSiN. it can. The film thickness of the back surface conductive film 2 is not particularly limited as long as it satisfies the function for the electrostatic chuck, but is usually 10 nm to 200 nm. Further, the back surface conductive film 2 also has stress adjustment on the second main surface side of the reflective mask blank 100. That is, the back surface conductive film 2 is adjusted so as to obtain a flat reflective mask blank 100 by balancing the stress from various films formed on the first main surface side.

Before forming the above-mentioned absorber film 7, the back surface conductive film 2 can be formed on the substrate 110 with the multilayer reflective film. The substrate 110 with a multilayer reflective film includes a case where the back surface conductive film 2 is arranged on the second main surface of the substrate 110 with a multilayer reflective film shown in FIGS. 1 and 2. Further, the reflective mask blank 100 does not necessarily have to include the back surface conductive film 2.

<Etching mask film 9>
An etching mask film 9 may be formed on the absorber film 7. As the material of the etching mask film 9, a material having a high etching selectivity of the absorber film 7 with respect to the etching mask film 9 is used. Here, the "etching selection ratio of B to A" refers to the ratio of the etching rate between A, which is a layer (mask layer) that is not desired to be etched, and B, which is a layer that is desired to be etched. Specifically, it is specified by the formula "etching selectivity of B with respect to A = etching rate of B / etching rate of A". Further, "high selection ratio" means that the value of the selection ratio defined above is large with respect to the comparison target. The etching selectivity of the absorber film 7 with respect to the etching mask film 9 is preferably 1.5 or more, and more preferably 3 or more.

Examples of the material having a high etching selectivity of the absorber film 7 with respect to the etching mask film 9 include a material of chromium and a chromium compound. When the absorber film 7 is etched with a fluorine-based gas, a material of chromium or a chromium compound can be used. Examples of the chromium compound include a material containing Cr and at least one element selected from N, O, C and H. Further, when the absorber film 7 is etched with a chlorine-based gas that does not substantially contain oxygen, a material of silicon or a silicon compound can be used. Examples of the silicon compound include a material containing Si and at least one element selected from N, O, C and H, metallic silicon (metal silicide) containing a metal in silicon and the silicon compound, and metallic silicon compound (metal silicide). Materials such as compound) can be mentioned. Examples of the metal silicon compound include a material containing a metal, Si, and at least one element selected from N, O, C, and H.

The reflective mask blank 100 of the present embodiment preferably contains an etching mask film 9 containing chromium (Cr) on the absorber film 7. The etching mask film 9 more preferably contains CrN, CrO, CrC, CrON, CrOC, CrCN or CrOCN, and is a CrO-based film (CrO film, CrON film, CrOC film or CrOCN film) containing chromium and oxygen. Is more preferable.

By making the protective film 6 have the above-described configuration, damage to the protective film 6 when the etching mask film 9 containing chromium (Cr) is peeled off by dry etching using a mixed gas of chlorine gas and oxygen gas is suppressed. Can be done.

Further, when the etching mask film 9 is made of silicon or a silicon compound by forming the protective film 6 (or the second layer 64) as a RuAl-containing film, a RuY-containing film, or a RuRh-containing film, the etching mask film 9 is formed. Damage to the protective film 6 when peeled by dry etching using a fluorine-based gas can be suppressed. Therefore, the range of selection of materials or etching conditions for the absorber film 7 and / or the etching mask film 9 is widened. Since damage to the protective film 6 due to dry etching using a fluorine-based gas can be suppressed, the substrate 110 with a multilayer reflective film and the reflective mask blank 100 manufactured by the manufacturing method of the present embodiment have an etching mask film. The resist film 8 can be provided in contact with the absorber film 7 without using 9. A desired pattern such as a circuit pattern is drawn (exposed) on the resist film 8 to form a predetermined resist pattern by further developing and rinsing, and the absorber film 7 is etched using this resist pattern as a mask. , Absorber pattern can be formed.

The film thickness of the etching mask film 9 is preferably 3 nm or more from the viewpoint of obtaining a function as an etching mask that accurately forms a transfer pattern on the absorber film 7. Further, the film thickness of the etching mask film 9 is preferably 15 nm or less from the viewpoint of reducing the film thickness of the resist film 8.

<Other thin films>
In the substrate 110 with a multilayer reflective film and the reflective mask blank 100 of the present embodiment, the substrate 1 to the back surface conductive film 2 are formed between the glass substrate which is the substrate 1 and the back surface conductive film 2 containing tantalum or chromium. It is preferable to provide a hydrogen intrusion suppression film that suppresses the invasion of hydrogen into the conductor. Due to the presence of the hydrogen intrusion suppression film, it is possible to suppress the uptake of hydrogen into the back surface conductive film 2, and it is possible to suppress the increase in the compressive stress of the back surface conductive film 2.

The material of the hydrogen intrusion suppression film may be any kind as long as it is difficult for hydrogen to permeate and can suppress the invasion of hydrogen from the substrate 1 to the back surface conductive film 2. Specific examples of the material for the hydrogen intrusion suppression membrane include Si, SiO ₂ , SiON, SiCO, SiCON, SiBO, SiBON, Cr, CrN, CrON, CrC, CrCN, CrCO, CrCON, Mo, MoSi, and MoSiN. , MoSiO, MoSiCO, MoSiON, MoSiCON, TaO, TaON and the like. The hydrogen intrusion suppression film can be a single layer of these materials, or may be a plurality of layers and a composition gradient film.

<Reflective mask 200>
The present embodiment is a reflective mask 200 in which the absorber film 7 in the above-mentioned reflective mask blank 100 is patterned and the absorber pattern 7a is provided on the multilayer reflective film 5. By using the reflective mask blank 100 of the present embodiment, it is possible to obtain a reflective mask 200 having a protective film 6 having high resistance to etching gas and high resistance to cleaning.

The reflective mask 200 of the present embodiment is used to manufacture the reflective mask 200. Here, only an outline explanation will be given, and later, a detailed explanation will be given with reference to the drawings in the examples.

A reflective mask blank 100 is prepared, and a resist film is formed on the outermost surface of the first main surface thereof (on the etching mask film 9 formed on the absorber film 7 as described in the following examples). 8 is formed (unnecessary when the resist film 8 is provided as the reflective mask blank 100), and a desired pattern such as a circuit pattern is drawn (exposed) on the resist film 8 and further developed and rinsed. The resist pattern 8a of the above is formed.

The etching mask pattern 9a is formed by dry etching the etching mask film 9 using the resist pattern 8a as a mask. Next, using this etching mask pattern 9a as a mask, the absorber film 7 is dry-etched to form the absorber pattern 7a. The etching gas for dry etching the absorber film 7 includes chlorine-based gas such as _{Cl 2} , SiCl ₄ , and CHCl _{3 , mixed gas containing chlorine-based gas and O 2} in a predetermined ratio, and chlorine. Mixed gas containing system gas and He in a predetermined ratio, mixed gas containing chlorine gas and Ar in a predetermined ratio, CF ₄ , CHF ₃ , C ₂ F ₆ , C ₃ F ₆ , C ₄ F ₆ , From fluorine-based gases such as _{C 4} F ₈ , CH ₂ F ₂ , CH ₃ F, C ₃ F ₈ , SF ₆ , and F _{2 , and mixed gases containing fluorine gas and O 2} in a predetermined ratio, etc. The selected one can be used. Here, if oxygen is contained in the etching gas at the final stage of etching, the surface of the Ru-based protective film 6 is roughened. Therefore, in the over-etching step where the Ru-based protective film 6 is exposed to etching, it is preferable to use an etching gas containing no oxygen. After forming the absorber pattern 7a, the etching mask pattern 9a can be removed with a mixed gas of chlorine-based gas and oxygen gas or a fluorine-based gas.

Then, the resist pattern 8a is removed by ashing or a resist stripping solution to prepare an absorber pattern 7a in which a desired circuit pattern is formed.

By the above steps, the reflective mask 200 of the present embodiment can be obtained.

<Manufacturing method of semiconductor devices>
The present embodiment is a method for manufacturing a semiconductor device, which comprises a step of performing a lithography process using an exposure device using the above-mentioned reflective mask 200 to form a transfer pattern on a transfer target. Specifically, the above-mentioned reflective mask 200 can be set in an exposure apparatus having an exposure light source that emits EUV light, and the transfer pattern can be transferred to a resist film formed on a substrate to be transferred. According to the method for manufacturing a semiconductor device of the present embodiment, even if the thin film of the reflective mask 200 contains impurities (trace materials), the reflective mask 200 does not adversely affect the performance of the reflective mask 200. Since it can be used, it is possible to manufacture a semiconductor device having a fine and highly accurate transfer pattern.

Specifically, a desired transfer pattern can be formed on the semiconductor substrate by performing EUV exposure using the reflective mask 200 of the present embodiment. In addition to this lithography process, various steps such as etching the film to be processed, forming an insulating film, a conductive film, introducing a dopant, and annealing are performed to manufacture a semiconductor device in which a desired electronic circuit is formed with a high yield. can do.

Hereinafter, examples will be described. These examples do not limit the present invention.

(Example)
As an example, a substrate 110 with a multilayer reflective film was produced in which a multilayer reflective film 5 and a protective film 6 were formed on the first main surface of the substrate 1. Table 1 shows the material and composition of the protective film 6 formed as an example. The substrate 110 with a multilayer reflective film of each example was produced in the same manner except that the type of the protective film 6 was different. As the protective film 6 of each example, those described below were used.

The protective film 6 of Examples 1-1 and 1-2 is a RuAl film, and the protective film 6 of Examples 1-3 is a RuAlN film (see FIG. 1). The protective film 6 of Examples 1-4 is a protective film 6 composed of two layers, a first layer 62 of the RuZr film and a second layer 64 of the RuAl film (see FIG. 2).

The protective film 6 of Examples 2-1 and 2-2 is a RuY film, and the protective film 6 of Examples 2-3 is a RuYN film (see FIG. 1). The protective film 6 of Example 2-4 is a protective film 6 composed of two layers, a first layer 62 of the RuTi film and a second layer 64 of the RuY film (see FIG. 2).

The protective film 6 of Examples 3-1 and 3-2 is a RuZr film, and the protective film 6 of Example 3-3 is a RuZrN film (see FIG. 1). The protective film 6 of Example 3-4 is a protective film 6 composed of two layers, a first layer 62 of the RuZr film and a second layer 64 of the RuZr film (see FIG. 2).

The protective film 6 of Examples 4-1 and 4-2 is a RuRh film, and the protective film 6 of Example 4-3 is a RuRhN film (see FIG. 1). The protective film 6 of Example 4-4 is a protective film 6 composed of two layers, a first layer 62 of the RuTi film and a second layer 64 of the RuRh film (see FIG. 2).

The protective film 6 of Examples 5-1 and 5-2 is a RuHf film, and the protective film 6 of Example 5-3 is a RuHfN film (see FIG. 1). The protective film 6 of Example 5-4 is a protective film 6 composed of two layers, a first layer 62 of the RuZr film and a second layer 64 of the RuHf film (see FIG. 2).

The substrate 110 with the multilayer reflective film of the example was produced as follows.

_{A SiO 2-} TiO ₂ system glass substrate, which is a 6025 size (about 152 mm × 152 mm × 6.35 mm) low thermal expansion glass substrate in which both the first main surface and the second main surface are polished, is prepared, and the substrate 1 and the substrate 1 are prepared. did. Polishing was performed by a rough polishing process, a precision polishing process, a local processing process, and a touch polishing process so that the main surface was flat and smooth.

Next, the multilayer reflective film 5 was formed on the first main surface of the substrate 1. The multilayer reflective film 5 was a periodic multilayer reflective film 5 composed of Si and Mo in order to obtain a multilayer reflective film 5 suitable for EUV light having a wavelength of 13.5 nm. Specifically, a Si target and a Mo target were used as a target for a high refractive index material and a target for a low refractive index material. By supplying krypton (Kr) ion particles from an ion source to these targets and performing ion beam sputtering, Si layers and Mo layers were alternately laminated on the substrate 1.

Here, the sputtered particles of Si and Mo were incident on the normal of the first main surface of the substrate 1 at an angle of 30 degrees. First, the Si layer was formed with a film thickness of 4.2 nm, and then the Mo layer was formed with a film thickness of 2.8 nm. This was set as one cycle, and the layers were laminated for 40 cycles in the same manner, and finally a Si layer was formed with a film thickness of 4.0 nm to form a multilayer reflective film 5. Therefore, the material of the lowermost layer of the multilayer reflective film 5, that is, the multilayer reflective film 5 closest to the substrate 1, is Si, and the material of the uppermost layer of the multilayer reflective film 5, that is, the multilayer reflective film 5 in contact with the protective film 6 is also Si. Is.

Next, the protective film 6 shown in Table 1 was formed on the surface of the multilayer reflective film 5 by the ion beam sputtering method. For example, in the case of the protective film 6 of Example 1-1, the target for the ion beam sputtering method was used as a RuAl mixed sintering target having the composition shown in Table 1. In an Ar gas atmosphere, the protective film 6 of Example 1-1 composed of the RuAl film having the composition shown in Table 1 was formed into a film having the film thickness shown in Table 1 by an ion beam sputtering method using a RuAl mixed sintering target. .. Here, the sputtered particles of Ru and Al were incident on the normal of the first main surface of the substrate 1 at an angle of 30 degrees. As for the protective film 6 of other examples, the protective film 6 was formed in the same manner as in Example 1-1.

The protective film 6 of Examples 1-3, Example 2-3, Example 3-3, Example 4-3 and Example 5-3 contains nitrogen (N). These protective films 6 were formed by reactive sputtering in a mixed gas atmosphere of _{Ar gas and N 2 gas.}

Further, the protective film 6 of Examples 1-4, Example 2-4, Example 3-4, Example 4-4 and Example 5-4 is 2 of the first layer 62 and the second layer 642. It is a protective film 6 composed of two layers. Therefore, in these examples, the first layer 62 was formed and then the second layer 64 was formed. Table 2 shows the composition and film thickness of the first layer 62 of these examples. Table 1 shows the composition and film thickness of the second layer 64 of these examples.

As described above, the substrate 110 with the multilayer reflective film of the example was manufactured.

(Comparative Example 1)
A substrate 110 with a multilayer reflective film of Comparative Example 1 was manufactured in the same manner as in Example 1-1, except that the material was a single-layer protective film 6 made of only Ru. As the protective film 6 of Comparative Example 1, a protective film 6 of Comparative Example 1 composed of a Ru film was formed with a film thickness shown in Table 1 by an ion beam sputtering method using a Ru target in an Ar gas atmosphere.

(Reflective mask blank 100)
A reflective mask blank 100 including an absorber film 7 and an etching mask film 9 was manufactured using the substrate 110 with a multilayer reflective film of Examples and Comparative Examples 1 described above. Hereinafter, a method for manufacturing the reflective mask blank 100 will be described.

The absorber film 7 was formed on the protective film 6 of the substrate 110 with a multilayer reflective film by the DC magnetron sputtering method. The absorber film 7 was a laminated film 7 composed of two layers, a TaN film which is an absorption layer and a TaO film which is a low reflection layer. A TaN film was formed as an absorption layer on the surface of the protective film 6 of the substrate 110 with the multilayer reflective film described above by a DC magnetron sputtering method. This TaN film was formed by a reactive sputtering method in a mixed gas atmosphere of _{Ar gas and N 2} gas in which a substrate 110 with a multilayer reflective film was opposed to a Ta target. Next, a TaO film (low reflection layer) was further formed on the TaN film by the DC magnetron sputtering method. Similar to the TaN film, this TaO film was formed by a reactive sputtering method in a mixed gas atmosphere of _{Ar and O 2} with the substrate 110 with a multilayer reflective film facing the Ta target.

The composition (atomic ratio) of the TaN film was Ta: N = 70:30, and the film thickness was 48 nm. The composition (atomic ratio) of the TaO film was Ta: O = 35:65, and the film thickness was 11 nm.

Next, an etching mask film 9 made of a CrOCN film was formed on the absorber film 7 by the DC magnetron sputtering method. The CrOCN film was formed by reactive sputtering using a Cr target in a mixed gas atmosphere of _{Ar gas, N 2} gas and CO _{2 gas.} The etching mask film 9 was formed with a film thickness of 5 nm.

Next, a back surface conductive film 2 made of CrN was formed on the second main surface (back side main surface) of the substrate 1 by a magnetron sputtering method (reactive sputtering method) under the following conditions. Conditions for forming the back surface conductive film 2: Cr target, _{mixed gas atmosphere of Ar and N 2} (Ar: 90 atomic%, N: 10 atomic%), film thickness 20 nm.

As described above, the reflective mask blank 100 of Example and Comparative Example 1 was manufactured.

(Reflective mask 200)
Next, the reflective mask 200 was manufactured using the reflective mask blank 100 of Examples and Comparative Example 1. The production of the reflective mask 200 will be described with reference to FIG.

FIG. 8 (a) is a schematic cross-sectional view of an exemplary reflective mask blank 100 described herein (see, eg, FIG. 4). First, as shown in FIG. 8B, a resist film 8 was formed on the etching mask film 9 of the reflective mask blank 100. Then, a desired pattern such as a circuit pattern was drawn (exposed) on the resist film 8 and further developed and rinsed to form a predetermined resist pattern 8a (FIG. 8 (c)). Next, the etching mask pattern 9a was formed by dry etching the etching mask film 9 with the resist pattern 8a as a mask using a mixed gas of _{Cl 2} gas and O _{2 gas (Cl 2} + O _{2 gas).} (Fig. 8 (d)). The resist pattern 8a was peeled off by oxygen ashing. Using the etching mask pattern 9a as a mask, the TaO film (low reflection layer) of the absorber film 7 is _{dry-etched with CF 4} gas, and then the TaN film is dry-etched with Cl ₂ gas. , An absorber pattern 7a was formed (FIG. 8 (e)).

Then, the etching mask pattern 9a was removed by dry etching using a mixed gas of _{Cl 2} gas and O _{2 gas (Cl 2} + O _{2 gas) (FIG. 8 (f)).} Finally, wet cleaning with pure water (DIW) was performed to produce the reflective mask 200 of Example and Comparative Example 1.

As described above, the reflective mask 200 of Example and Comparative Example 1 was manufactured.

(Evaluation of Reflective Mask 200 of Example and Comparative Example 1)
For each of the above-mentioned Examples and Comparative Example 1, the influence of dry etching when removing the etching mask pattern 9a was evaluated.

Specifically, for each of the above-mentioned Examples and Comparative Example 1, a mask blank having the structure shown in FIG. 4 is manufactured, and in the manufacturing process of the above-mentioned reflective mask 200, the mask blank corresponds to FIG. 8 (e). An etching mask pattern 9a and an absorber pattern 7a were formed. However, the pattern shape of the absorber pattern 7a for evaluation is such that the surface of the protective film 6 is widely exposed so that the reflectance of EUV light can be measured at the portion where the surface of the protective film 6 is exposed. The shape pattern was used. After the absorber pattern 7a was formed, the reflectance (reflectance before etching) of the surface of the protective film 6 with respect to EUV light having a wavelength of 13.5 nm was measured. Next, the etching mask pattern 9a of the CrOCN film was removed by dry etching using a mixed gas of _{Cl 2} gas and O _{2 gas (Cl 2} : O _{2 = 9: 1) (FIG. 8 (f)).} After removing the etching mask pattern 9a by etching, the reflectance (reflectance after etching) of the surface of the protective film 6 with respect to EUV light having a wavelength of 13.5 nm was measured. Column A of Table 3 shows changes in reflectance (reflectance after etching / reflectance before etching) before and after removal of the etching mask pattern 9a by etching. The change in reflectance is shown as a ratio when Comparative Example 1 is 1.

Further, the change in the film thickness of the protective film 6 during dry etching using the above-mentioned _{mixed gas of Cl 2} gas and O ₂ gas (Cl ₂ + O ₂ gas) is measured, and Ru of the protective film 6 due to the mixed gas is measured. The etching rate of each material when the etching rate of the film was set to 1 was calculated as a ratio. Column B of Table 3 shows the etching rate ratio of the protective film 6 with the mixed gas.

As is clear from Table 3, the change in reflectance before and after removal of the etching mask pattern 9a by etching was smaller in all the examples than in Comparative Example 1. Further, as compared with Comparative Example 1, the etching rate of the protective film 6 by the _{mixed gas (Cl 2} + O _{2 gas) was smaller in all the examples.} Therefore, it was clarified that the protective film 6 of the embodiment of the present embodiment has high resistance to the etching gas for removing the etching mask film 9.

Further, when the resistance of the protective film 6 to cleaning using sulfuric acid superwater (SPM) was separately measured, the change in film thickness before and after cleaning was small in all the examples as compared with Comparative Example 1, and EUV light was used. It was clarified that the protective film 6 has high resistance to cleaning because the fluctuation of the reflectance with respect to the light was small.

Table 4 shows the ratio when the film thickness reduction rate when SPM cleaning was performed under the following cleaning conditions was measured and Comparative Example 1 (Ru film) was set to 1.
Cleaning liquid H ₂ SO ₄ : H ₂ O ₂ = 2: 1 (weight ratio)
Cleaning temperature 120 ° C
Cleaning time 10 minutes

As is clear from Table 4, the SPM cleaning resistance of Example 4-2 (Ru: Rh = 70: 30) and Example 4-3 (Ru: Rh: N = 65: 30: 5) was found in Example 4. It can be seen that it is higher than the SPM cleaning resistance of -1 (Ru: Rh = 80: 20). Since the protective film of Example 4-4 is the same as that of Example 4-2, the ratio of the film reduction rate when Comparative Example 1 (Ru film) is 1 is also the ratio of Example 4-2. Is the same as.

(Manufacturing of semiconductor devices)
The reflective mask 200 manufactured by using the substrate 110 with the multilayer reflective film of the example was set in the EUV scanner, and EUV exposure was performed on the wafer on which the film to be processed and the resist film were formed on the semiconductor substrate. Then, by developing this exposed resist film, a resist pattern was formed on the semiconductor substrate on which the film to be processed was formed.

The reflective mask 200 manufactured by using the substrate 110 with the multilayer reflective film of the embodiment has a protective film having high resistance to etching gas and high resistance to cleaning, so that a fine and highly accurate transfer pattern ( The resist pattern) could be formed.

By transferring this resist pattern to the film to be processed by etching and undergoing various steps such as insulating film, forming a conductive film, introducing a dopant, and annealing, a semiconductor device having desired characteristics can be manufactured with a high yield. We were able to.

1 Mask blank board (board)
2 Backside conductive film 5 Multilayer reflective film 6 Protective film 7 Absorber film 7a Absorbent pattern 8 Resist film 8a Resist pattern 9 Etching mask film 9a Etching mask pattern 62 First layer 64 Second layer 100 Reflective mask blank 110 Multilayer Substrate with reflective film 200 Reflective mask

Claims (9)

A substrate with a multilayer reflective film having a substrate, a multilayer reflective film provided on the substrate, and a protective film provided on the multilayer reflective film.
The protective film comprises ruthenium (Ru) and at least one additive material selected from aluminum (Al), yttrium (Y), zirconium (Zr), rhodium (Rh) and hafnium (Hf). A substrate with a multilayer reflective film, characterized in that the content of the material is 5 atomic% or more and less than 50 atomic%. The protective film includes a first layer and a second layer from the substrate side.
The first layer is ruthenium (Ru), magnesium (Mg), aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), germanium (Ge), zirconium (Zr), niobium ( Containing at least one selected from Nb), molybdenum (Mo), rhodium (Rh), hafnium (Hf) and tungsten (W).
The substrate with a multilayer reflective film according to claim 1, wherein the second layer contains the ruthenium (Ru) and the additive material. The substrate with a multilayer reflective film according to claim 1 or 2, wherein the protective film, the first layer, or the second layer further contains nitrogen (N). The substrate with a multilayer reflective film according to claim 2 or 3, wherein the Ru content of the second layer is smaller than the Ru content of the first layer. A reflective mask blank comprising an absorber film on a protective film of the substrate with a multilayer reflective film according to any one of claims 1 to 4. The reflective mask blank according to claim 5, wherein an etching mask film containing chromium (Cr) is contained on the absorber film. A reflective mask according to claim 5 or 6, wherein the absorber film in the reflective mask blank includes a patterned absorber pattern. The etching mask film of the reflective mask blank according to claim 6 is patterned to form an etching mask pattern.
Using the etching mask pattern as a mask, the absorber film is patterned to form an absorber pattern.
A method for producing a reflective mask, which comprises removing the etching mask pattern with a mixed gas of a chlorine-based gas and an oxygen gas. A feature of the present invention is that the reflective mask according to claim 7 is set in an exposure apparatus having an exposure light source that emits EUV light, and the transfer pattern is transferred to a resist film formed on a substrate to be transferred. A method for manufacturing a semiconductor device.

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