Reflective mask blank, reflective mask, and method of manufacturing reflective mask and semiconductor device

Abstract

The present invention provides a reflective mask blank for manufacturing a reflective mask capable of suppressing the peeling of an absorber pattern when EUV exposure is performed in an atmosphere containing hydrogen gas. A reflective mask blank comprising a substrate, a multilayer reflective film on the substrate, and an absorber film on the multilayer reflective film, wherein the absorber film comprises an absorption layer and a reflectance adjustment layer, and the absorption layer comprises at least one additive element selected from tantalum (Ta), boron (B) and nitrogen (N), hydrogen (H) and deuterium (D), wherein the content of the boron (B) in the absorption layer is greater than 5 atomic percent, and the content of the additive element in the absorption layer is 0.1 atomic percent or more and 30 atomic percent or less.

Description

Technology Field

[0001] The present invention relates to a reflective mask used in the manufacture of semiconductor devices, etc., and a reflective mask blank used to manufacture the reflective mask. Furthermore, the present invention relates to a method for manufacturing a semiconductor device using the reflective mask. Background Technology

[0002] In semiconductor device manufacturing, the types of light sources for exposure devices have evolved by gradually shortening wavelengths, ranging from the g-line with a wavelength of 436 nm, the i-line with 365 nm, the KrF laser with 248 nm, and the ArF laser with 193 nm. To realize finer pattern transfer, EUV lithography using Extreme Ultra Violet (EUV) with a wavelength of around 13.5 nm has been developed. In EUV lithography, reflective masks are used because there are few materials that are transparent to EUV light. This reflective mask has a basic structure consisting of a low thermal expansion substrate, a multilayer reflective film, a protective film, and a transfer pattern. A multilayer reflective film that reflects exposure light is formed on the low thermal expansion substrate. A protective film is formed on top of the multilayer reflective film to protect it. A desired transfer pattern is formed on top of the protective film. In addition, as representative transfer patterns, there is a binary reflective mask consisting of a relatively thick absorber pattern that sufficiently absorbs EUV light, and a phase-shift reflective mask (halftone phase-shift reflective mask) consisting of a relatively thin absorber pattern that reduces the photodegradation of EUV light by light absorption and generates reflected light that is nearly phase-inverted (phase inversion of about 180°) with respect to the reflected light from the multilayer reflective film. Similar to a transmissive optical phase-shift mask, this phase-shift reflective mask obtains high transfer optical image contrast due to the phase-shift effect. Therefore, the phase-shift reflective mask has a resolution-enhancing effect. Furthermore, since the film thickness of the absorber pattern (phase-shift pattern) of the phase-shift reflective mask is thin, a fine phase-shift pattern with good precision can be formed.

[0003] Technologies related to such reflective masks for EUV lithography and mask blanks for producing them are disclosed in Patent Documents 1 and 2.

[0004] Patent Document 1 describes a reflective mask blank for EUV lithography in which a reflective layer that reflects EUV light and an absorber layer that absorbs EUV light are formed in this order on a substrate. Specifically, the reflective mask blank of Patent Document 1 describes that the absorber layer contains tantalum (Ta), nitrogen (N), and hydrogen (H), and that the total content of Ta and N in the absorber layer is 50 to 99.9 at%, and the content of H is 0.1 to 50 at%. Patent Document 1 also describes that the reflective mask blank of Patent Document 1 has an amorphous crystal state of the film of the absorber layer, and that stress and surface roughness are reduced.

[0005] In addition, Patent Document 2 describes a reflective mask blank for EUV lithography in which a reflective layer that reflects EUV light and an absorber layer that absorbs EUV light are formed in this order on a substrate. Specifically, the reflective mask blank of Patent Document 2 describes that the absorber layer contains at least tantalum (Ta), boron (B), nitrogen (N), and hydrogen (H), and in the absorber layer, the content of B is 1 at% or more and less than 5 at%, the content of H is 0.1 to 5 at%, the total content of Ta and N is 90 to 98.9 at%, and the compositional ratio of Ta and N (Ta:N) is 8:1 to 1:1. As a result, in the reflective mask blank of Patent Document 2, the crystalline state of the film of the absorber layer becomes amorphous, and stress and surface roughness are also reduced. In addition, Patent Document 2 describes that the reflective mask blank of Patent Document 2 has a low content of B (less than 5 at%) in the absorber layer, so there are no problems such as a decrease in the deposition rate or instability of the discharge during deposition when the absorber layer is deposited. Specifically, Patent Document 2 describes that there is no risk of problems such as non-uniformity in the film composition or film thickness, or furthermore, failure to deposit. Prior art literature

[0006] International Publication No. 2009 / 116348 International Publication No. 2010 / 050518

[0007] In EUV lithography, it is known that exposure contamination occurs, such as the deposition of carbon films on reflective masks due to EUV exposure. To suppress this, a technique of introducing hydrogen gas into the atmosphere during exposure has recently been adopted.

[0008] As disclosed in Patent Documents 1 and 2, tantalum (Ta) has conventionally been used as a material for forming the absorber film of a reflective mask blank. However, when EUV exposure is performed in an atmosphere containing hydrogen gas, a problem may arise in which the absorber pattern peels off. The reason for this problem is thought to be as follows. That is, during EUV exposure, hydrogen gas in the exposure atmosphere containing hydrogen gas is absorbed into the absorber pattern as atomic hydrogen (H), causing the volume of the absorber pattern to expand and the compressive stress to increase. Due to this, cracks occur at the interface with weak adhesion in the thin film (e.g., a protective film) placed on the substrate side of the absorber pattern. When a protective film is placed on the substrate side of the absorber pattern, hydrogen may also penetrate into the protective film. When hydrogen penetrates into the protective film, many cracks may occur at the interface between the protective film and the multilayer reflective film. It is believed that atomic hydrogen (H) accumulates within the space of the generated crack to become hydrogen gas, causing the space to expand and detach the absorber pattern.

[0009] Therefore, the present invention aims to provide a reflective mask capable of suppressing the peeling of an absorber pattern when EUV exposure is performed in an atmosphere containing hydrogen gas. Furthermore, the present invention aims to provide a reflective mask blank for manufacturing a reflective mask capable of suppressing the peeling of an absorber pattern.

[0010] The inventors have discovered that by incorporating hydrogen into the absorber membrane in advance, the possibility for new atomic hydrogen (H) to enter the absorber membrane is eliminated, thereby preventing the absorber pattern from peeling off. More specifically, they have discovered that by suppressing membrane stress fluctuations caused by hydrogen intrusion into the absorber pattern, it is possible to prevent the absorber pattern from becoming prone to peeling or from actually peeling off. By incorporating boron into the absorber membrane, it becomes easier to amorphize the crystal structure, and the absorber membrane can be made into one with excellent smoothness. When the absorber membrane contains hydrogen, the membrane density of the absorber membrane decreases, and thus the decay coefficient k decreases. Therefore, in order to prevent a decrease in the decay coefficient by suppressing the decrease in membrane density of the absorber membrane caused by the addition of hydrogen, and also to obtain excellent smoothness by making the absorber membrane into an amorphous structure, it is necessary to include more than 5 atomic percent of boron in the absorber membrane. The inventors arrived at the present invention by obtaining the above knowledge.

[0011] In addition, according to further findings obtained by the inventors, hydrogen contributes little to the amorphization of the crystal structure of the absorber membrane. Therefore, in order to obtain an absorber membrane with excellent smoothness through amorphization, it is necessary for the absorber membrane to contain boron.

[0012] To solve the above problem, the present invention has the following configuration.

[0013] (Composition 1)

[0014] Configuration 1 of the present invention is a reflective mask blank comprising a substrate, a multilayer reflective film on the substrate, and an absorbent film on the multilayer reflective film,

[0015] The above-mentioned absorbing membrane comprises an absorption layer and a reflectance adjusting layer, and

[0016] The absorption layer comprises at least one additive element selected from tantalum (Ta), boron (B), and nitrogen (N), and hydrogen (H) and deuterium (D), and

[0017] The boron (B) content of the above absorption layer is greater than 5 atomic percent, and

[0018] The above-described absorption layer is a reflective mask blank characterized by having an additive element content of 0.1 atomic% or more and 30 atomic% or less.

[0019] (Composition 2)

[0020] Configuration 2 of the present invention is a reflective mask blank of Configuration 1, characterized in that the reflectance adjusting layer comprises at least one additive element selected from tantalum (Ta) and oxygen (O), hydrogen (H) and deuterium (D).

[0021] (Composition 3)

[0022] Composition 3 of the present invention is a reflective mask blank of composition 1 or 2, characterized in that the reflectance adjusting layer further comprises boron (B), and the content of the boron (B) is greater than 5 atomic percent.

[0023] (Composition 4)

[0024] Configuration 4 of the present invention is a reflective mask blank of any one of configurations 1 to 3, wherein the absorption layer comprises a lower surface region including a surface on the substrate side and an upper surface region including a surface opposite to the substrate, and the concentration (atomic %) of the additive element in the lower surface region is higher than the concentration (atomic %) of the additive element in the upper surface region.

[0025] (Composition 5)

[0026] Configuration 5 of the present invention is a reflective mask blank of any one of configurations 1 to 3, wherein the absorption layer comprises a lower surface area including a surface on the substrate side and an upper surface area including a surface opposite to the substrate, and the concentration (atomic %) of the additive element in the upper surface area is higher than the concentration (atomic %) of the additive element in the lower surface area.

[0027] (Composition 6)

[0028] Configuration 6 of the present invention is a reflective mask blank of any one of configurations 1 to 5, characterized in that it includes a protective film between the multilayer reflective film and the absorbent film, and the protective film includes at least one additive element selected from ruthenium (Ru), hydrogen (H), and deuterium (D).

[0029] (Composition 7)

[0030] Configuration 7 of the present invention is a reflective mask characterized in that the absorbent film in the reflective mask blank of any one of configurations 1 to 6 has a patterned absorbent pattern.

[0031] (Composition 8)

[0032] Configuration 8 of the present invention is a method for manufacturing a reflective mask characterized by forming an absorber pattern by patterning the absorber film of a reflective mask blank of any one of configurations 1 to 6.

[0033] (Composition 9)

[0034] Configuration 9 of the present invention is a method for manufacturing a semiconductor device characterized by having a process of setting a reflective mask of configuration 7 in an exposure device having an exposure light source that emits EUV light, and transferring a transfer pattern to a resist film formed on a substrate to be transferred.

[0035] According to the present invention, a reflective mask capable of suppressing the peeling of an absorber pattern when EUV exposure is performed in an atmosphere containing hydrogen gas can be provided. Additionally, according to the present invention, a reflective mask blank for manufacturing a reflective mask capable of suppressing the peeling of an absorber pattern can be provided. Brief explanation of the drawing

[0036] FIG. 1 is a schematic cross-sectional view of a main part to explain the schematic configuration of an embodiment of the reflective mask blank of the present invention. FIG. 2 is a schematic cross-sectional view of a main part to explain the schematic configuration of another embodiment of the reflective mask blank of the present invention. FIG. 3 is a schematic cross-sectional view of a main part to explain the schematic configuration of another embodiment of the reflective mask blank of the present invention. Figures 4a-4e are examples of process diagrams showing the main cross-sectional schematic of the process of manufacturing a reflective mask from a reflective mask blank. Figures 5a-5e are another example of a process diagram showing a main cross-sectional schematic of the process of manufacturing a reflective mask from a reflective mask blank. Specific details for implementing the invention

[0037] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Furthermore, the following embodiments are merely forms for embodying the present invention and do not limit the scope of the present invention. Additionally, in the drawings, identical or equivalent parts are denoted by the same reference numerals to simplify or omit their description.

[0038] <Composition of reflective mask blank (100) and method of manufacturing the same>

[0039] FIG. 1 is a schematic cross-sectional view of a main part for explaining the configuration of a reflective mask blank (100) of an embodiment of the present invention. As shown in FIG. 1, the reflective mask blank (100) of the present embodiment has a substrate (1), a multilayer reflective film (2) that reflects EUV light, which is an exposure light formed on the first main surface (surface) side, and an absorbing film (4) that absorbs EUV light formed on the multilayer reflective film (2), and these are stacked in this order. Also, as shown in FIG. 1, the reflective mask blank (100) of the present embodiment may additionally have a protective film (3) installed between the multilayer reflective film (2) and the absorbing film (4) to protect the multilayer reflective film (2). In the reflective mask blank (100) of the present embodiment, the absorbing film (4) has an absorption layer (42) and a reflectance adjustment layer (44) installed on the absorption layer (42). Also, on the second main surface (back side) of the substrate (1), a back conductive film (5) for an electrostatic chuck is formed.

[0040] FIG. 2 shows a reflective mask blank (100) of another embodiment. As shown in FIG. 2, the reflective mask blank (100) of this embodiment may additionally have an etching mask film (6) formed on an absorbent film (4).

[0041] Additionally, the above-described reflective mask blank (100) includes a configuration in which a back-side conductive film (5) is not formed. Furthermore, the above-described reflective mask blank (100) includes a configuration of a resist film attached mask blank in which a resist film (11) is formed on an etching mask film (6).

[0042] In this specification, for example, the description “multilayer reflective film (2) formed on the substrate (1)” or “multilayer reflective film (2) on the substrate (1)” includes cases where, in addition to meaning that the multilayer reflective film (2) is arranged in contact with the surface of the substrate (1), it also includes cases where another film is formed between the substrate (1) and the multilayer reflective film (2). The same applies to other films. Furthermore, in this specification, for example, “film A is arranged in contact with film B” means that film A and film B are arranged to be in direct contact without interposing another film between film A and film B.

[0043] In this specification, hydrogen (H) and / or deuterium (D) included in a thin film, such as an absorbent film (4), of the reflective mask blank (100) of the present embodiment are referred to as "additive elements." Furthermore, since hydrogen (H) and deuterium (D) exhibit similar properties, unless specifically explained otherwise, some or all of the hydrogen (H) constituting a predetermined thin film can be replaced with deuterium (D).

[0044] Below, each component of the reflective mask blank (100) will be described in detail.

[0045] <<Board (1)>>

[0046] In order to prevent distortion of the absorber pattern (4a) due to heat during exposure to EUV light, the substrate (1) is preferably used to have a low coefficient of thermal expansion within the range of 0±5 ppb / ℃. For example, materials having a low coefficient of thermal expansion within this range may be used, such as SiO2-TiO2 glass, multi-component glass ceramics, etc.

[0047] The first main surface on the side where the transfer pattern of the substrate (1) (which is formed by patterning the absorber film (4) described later) is formed is surface-processed to have high flatness in terms of obtaining at least pattern transfer precision and positional precision. In the case of EUV exposure, in the 132 mm × 132 mm area of ​​the main surface on the side where the transfer pattern of the substrate (1) is formed, it is preferable that the flatness is 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less. Also, the second main surface on the side opposite to the side where the absorber film (4) is formed is a surface that is electrostatically chucked when set in the exposure device, and in the 142 mm × 142 mm area, it is preferable that the flatness is 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less.

[0048] In addition, the surface smoothness of the substrate (1) is also an extremely important factor. The surface roughness of the first main surface of the substrate (1) on which the transfer absorber pattern (4a) is formed is preferably 0.1 nm or less in root mean square roughness (RMS). Furthermore, the surface smoothness can be measured using an atomic force microscope.

[0049] In addition, the substrate (1) is preferably made to have high rigidity to prevent deformation caused by film stress of a film (multilayer reflective film (2), etc.) formed thereon. In particular, it is preferably made to have a high Young's modulus of 65 GPa or higher.

[0050] <<Multilayer reflective film (2)>>

[0051] The multilayer reflective film (2) provides the function of reflecting EUV light in the reflective mask (200). The multilayer reflective film (2) is a multilayer film in which each layer, composed mainly of elements with different refractive indices, is periodically stacked.

[0052] Generally, a multilayer film in which a thin film of a light element or its compound, which is a high refractive index material (high refractive index layer), and a thin film of a heavy element or its compound, which is a low refractive index material (low refractive index layer), are alternately stacked for about 40 to 60 cycles is used as a multilayer reflective film (2). The multilayer film may be stacked in multiple cycles with a stacking structure of high refractive index layer / low refractive index layer, in which a high refractive index layer and a low refractive index layer are stacked in this order from the substrate (1) side, and may also be stacked in multiple cycles with a stacking structure of low refractive index layer / high refractive index layer, in which a low refractive index layer and a high refractive index layer are stacked in this order from the substrate (1) side, in which a low refractive index layer and a high refractive index layer are stacked in this order, in which case a low refractive index layer / high refractive index layer is stacked in multiple cycles. In addition, it is preferable that the outermost layer of the multilayer reflective film (2), that is, the surface layer opposite to the substrate (1) of the multilayer reflective film (2), be a high refractive index layer. In the multilayer film described above, when a stacking structure of a high refractive index layer and a low refractive index layer stacked in this order from the substrate (1) is stacked multiple times with one period as the stacking structure of a high refractive index layer / low refractive index layer, the top layer becomes a low refractive index layer. In this case, if the low refractive index layer forms the outermost surface of the multilayer reflective film (2), it oxidizes easily, and the reflectivity of the reflective mask (200) decreases. Therefore, it is preferable to additionally form a high refractive index layer on the top layer of the low refractive index layer to form a multilayer reflective film (2). On the other hand, in the multilayer film described above, when a stacking structure of a low refractive index layer and a high refractive index layer stacked in this order from the substrate (1) side is stacked multiple times with one period as the stacking structure of a low refractive index layer / high refractive index layer, the top layer becomes a high refractive index layer, so it may be left as is.

[0053] In this embodiment, a layer containing silicon (Si) is used as the high refractive index layer. As for the material containing Si, in addition to Si alone, it may be a Si compound containing boron (B), carbon (C), nitrogen (N), and oxygen (O) in addition to Si. By using a layer containing Si as the high refractive index layer, a reflective mask (200) for EUV lithography with excellent reflectivity of EUV light is obtained. Also, in this embodiment, a glass substrate is preferably used as the substrate (1). Si also has excellent adhesion to the glass substrate. Also, as the low refractive index layer, a metal alone selected from molybdenum (Mo), ruthenium (Ru), rhodium (Rh), and platinum (Pt), or an alloy thereof, is used. For example, as a multilayer reflective film (2) for EUV light with a wavelength of 13 nm to 14 nm, a Mo / Si periodic stacked film is preferably used, in which Mo films and Si films are alternately stacked for about 40 to 60 periods. In addition, the high refractive index layer, which is the uppermost layer of the multilayer reflective film (2), may be formed of silicon (Si), and a silicon oxide layer containing silicon and oxygen may be formed between the uppermost layer (Si) and the Ru-based protective film (3). By doing so, mask cleaning resistance can be improved.

[0054] The reflectance of such a multilayer reflective film (2) alone is typically 65% ​​or more, and the upper limit is typically 73%. In addition, the thickness and period of each constituent layer of the multilayer reflective film (2) can be appropriately selected according to the exposure wavelength and selected to satisfy the law of Bragg reflection. In the multilayer reflective film (2), there are multiple high-refractive-index layers and low-refractive-index layers, but the thicknesses of the high-refractive-index layers and the low-refractive-index layers do not have to be the same. Also, the film thickness of the outermost Si layer of the multilayer reflective film (2) can be adjusted within a range that does not reduce the reflectance. The film thickness of the outermost Si (high-refractive-index layer) can be 3 nm to 10 nm.

[0055] The method of forming a multilayer reflective film (2) is known in the relevant technical field. For example, it can be formed by depositing each layer of the multilayer reflective film (2) by an ion beam sputtering method. In the case of the Mo / Si periodic multilayer film described above, for example, by an ion beam sputtering method, a Si film with a thickness of about 4 nm is first deposited on a substrate (1) using a Si target, and then a Mo film with a thickness of about 3 nm is deposited using a Mo target. The Si film and Mo film deposited in this way are stacked for 40 to 60 cycles, with the deposited Si film and Mo film forming one cycle, to form a multilayer reflective film (2) (the outermost layer is the Si layer). Also, when depositing the multilayer reflective film (2), it is preferable to form the multilayer reflective film (2) by supplying krypton (Kr) ion particles from an ion source and performing ion beam sputtering.

[0056] <<Protective Shield (3)>>

[0057] In the present embodiment, the reflective mask blank (100) preferably has a protective film (3) between the multilayer reflective film (2) and the absorbing film (4). By forming the protective film (3) on the multilayer reflective film (2), damage to the surface of the multilayer reflective film (2) can be suppressed when manufacturing a reflective mask (200) (EUV mask) using the reflective mask blank (100). As a result, the reflectivity characteristics for EUV light are improved.

[0058] A protective film (3) is formed on the multilayer reflective film (2) to protect the multilayer reflective film (2) from dry etching and cleaning during the manufacturing process of the reflective mask (200) described later. Additionally, the protective film (3) also serves to protect the multilayer reflective film (2) during the correction of black defects in the absorber pattern (4a) using an electron beam (EB). The protective film (3) is formed from a material that is resistant to etchants and cleaning solutions. Here, FIG. 1 shows a case where the protective film (3) is a single layer, but it may be made into a stacked structure of three or more layers. For example, the bottom layer and the top layer may be made of a layer containing the above Ru, and a protective film (3) may be formed by interposing a metal other than Ru or an alloy between the bottom layer and the top layer. For example, the protective film (3) may be composed of a material containing ruthenium as a main component. That is, the material of the protective film (3) may be a single Ru metal, a Ru alloy containing at least one metal selected from titanium (Ti), niobium (Nb), molybdenum (Mo), zirconium (Zr), yttrium (Y), boron (B), lanthanum (La), cobalt (Co), and rhenium (Re), and may contain nitrogen. Such a protective film (3) is particularly effective when the absorption layer (42) of the absorber film (4) is patterned by dry etching with a chlorine-based gas (Cl-based gas). It is preferable that the protective film (3) be formed from a material such that the etching selectivity ratio of the absorber film (4) to the protective film (3) in dry etching using a chlorine-based gas (etching rate of the absorber film (4) / etching rate of the protective film (3)) is 1.5 or higher, preferably 3 or higher.

[0059] The Ru content of this Ru alloy is 50 atomic percent or more and less than 100 atomic percent, preferably 80 atomic percent or more and less than 100 atomic percent, and more preferably 95 atomic percent or more and less than 100 atomic percent. In particular, when the Ru content of the Ru alloy is 95 atomic percent or more and less than 100 atomic percent, it is possible to suppress the diffusion of elements (silicon) constituting the multilayer reflective film (2) into the protective film (3) while sufficiently securing the reflectivity of EUV light, and to combine mask cleaning resistance, an etching stopper function when the absorbing film (4) is etched, and a protective film function that prevents changes over time of the multilayer reflective film (2).

[0060] The protective film (3) of the reflective mask blank (100) of the present embodiment preferably comprises at least one additive element selected from ruthenium (Ru), hydrogen (H), and deuterium (D). When the protective film (3) comprises an additive element (hydrogen (H) and / or deuterium (D)), the total content of the additive element is preferably greater than 5 atomic percent, and more preferably greater than 10 atomic percent. By having the protective film (3) between the multilayer reflective film (2) and the absorber film (4), damage to the surface of the multilayer reflective film (2) can be suppressed when manufacturing a reflective mask (200) using the reflective mask blank (100). In addition, by using a specific material as the material for the protective film (3), the adhesion between the multilayer reflective film (2) and the absorber film (4) can be further increased. Therefore, peeling of the protective film (3) and the absorber pattern (4a) can be suppressed more reliably. In addition, the protective film (3) can suppress peeling caused at the interface of the protective film (3) by including at least one additive element selected from hydrogen (H) and deuterium (D).

[0061] In addition, if the total content of the additive element (hydrogen (H) and / or deuterium (D)) in the protective film (3) is greater than the total content of the additive element in the absorption layer (42), the total content of hydrogen (H) or deuterium (D) in the protective film (3) does not necessarily have to be greater than 5 atomic percent, but may be 5 atomic percent or less.

[0062] In addition, according to the inventors' findings, if the total content of the additive element (hydrogen (H) and / or deuterium (D)) of the protective film (3) exceeds 5 atomic percent, there is a possibility that film peeling caused at the interface of the protective film (3) can be sufficiently prevented. In that case, it is not necessary to include the additive element in the absorbent film (4), or it may be sufficient to use a low concentration of the additive element.

[0063] That is, the reflective mask blank (100) of the embodiment in that case is a reflective mask blank (100) having a multilayer reflective film (2), a protective film (3), and an absorber film (4) in this order on a substrate (1). The absorber film (4) of this reflective mask blank (100) includes at least one additive element selected from tantalum (Ta), hydrogen (H), and deuterium (D). The protective film (3) of this reflective mask blank (100) includes at least one additive element selected from ruthenium (Ru), hydrogen (H), and deuterium (D). The content of the additive element in the protective film (3) of this reflective mask blank (100) is greater than 5 atomic percent. By using such a reflective mask blank (100), the peeling of the absorber pattern (4a) of the reflective mask (200) can be suppressed.

[0064] In EUV lithography, since there are few materials that are transparent to the exposure light, it is not technically simple to implement an EUV pellicle that prevents foreign matter from adhering to the mask pattern surface. In this regard, the operation of pellicles that do not use pellicles has become the mainstream. Furthermore, in EUV lithography, exposure contamination occurs, such as carbon film deposition or oxide film growth on the mask due to EUV exposure. Therefore, when using an EUV reflective mask (200) in the manufacturing of a semiconductor device, it is necessary to frequently clean the mask to remove foreign matter or contamination. For this reason, the EUV reflective mask (200) requires a mask cleaning resistance that is significantly different from that of a transmissive mask for photolithography. By using a Ru-based protective film (3) containing Ti, it is possible to satisfy the requirements for mask cleaning resistance, particularly high resistance to cleaning solutions such as sulfuric acid, sulfuric acid (SPM), ammonia, ammonia (APM), OH radical cleaning water, or ozone water with a concentration of 10 ppm or less.

[0065] The thickness of the protective film (3) composed of such Ru or its alloy, etc., is not particularly limited as long as it can perform its function as the protective film (3). In terms of the reflectance of EUV light, the thickness of the protective film (3) is preferably 1.0 nm to 8.0 nm, more preferably 1.5 nm to 6.0 nm.

[0066] As for the method of forming the protective film (3), any method similar to known film forming methods can be adopted without particular limitation. Specific examples include sputtering and ion beam sputtering methods.

[0067] <<absorbent membrane (4)>>

[0068] In the reflective mask blank (100) of the present embodiment, an absorbing film (4) that absorbs EUV light is formed on the multilayer reflective film (2) (or on the protective film (3) if the protective film (3) is formed). The absorbing film (4) has the function of absorbing EUV light. The absorbing film (4) of the present embodiment has an absorption layer (42) and a reflectance adjustment layer (44) installed on the absorption layer (42) (on the surface opposite to the substrate (1) among the two surfaces of the absorption layer (42)).

[0069] The absorber film (4) of the present embodiment has an absorption layer (42). The absorption layer (42) includes at least one additive element selected from tantalum (Ta), boron (B), and nitrogen (N), and hydrogen (H) and deuterium (D). By including a predetermined additive element in the absorber film (4), a reflective mask (200) can be obtained that suppresses the peeling of the absorber pattern (4a) when EUV exposure is performed in an atmosphere containing hydrogen gas.

[0070] The tantalum content in the absorption layer (42) is preferably 40 atomic% or more, preferably 50 atomic% or more, and more preferably 60 atomic% or more. The tantalum content in the absorption layer (42) is preferably 95 atomic% or less. The upper limit of the total content of nitrogen and boron in the absorption layer (42) is preferably 50 atomic% or less, and more preferably 45 atomic% or less. The lower limit of the total content of nitrogen and boron in the absorption layer (42) is preferably greater than 5 atomic%, and more preferably greater than 10 atomic%. The nitrogen content in the absorption layer (42) is preferably lower. This is because a lower nitrogen content accelerates the etching rate in chlorine gas, making it easier to remove the absorption layer (42).

[0071] The boron (B) content of the absorption layer (42) is greater than 5 atomic percent, preferably 10 atomic percent or more and 30 atomic percent or less. By having the absorption film (4) contain boron, it is easy to make the crystal structure amorphous, and the absorption film (4) can be made with excellent smoothness. Also, in this embodiment, the absorption film (4) contains hydrogen to suppress the peeling of the absorber pattern (4a). When the absorption film (4) contains hydrogen, the film density of the absorption film (4) is prone to decreasing. By having the absorption film (4) of this embodiment contain boron, an amorphous structured absorption film (4) can be obtained that suppresses the decrease in film density.

[0072] The content of the additive element (hydrogen (H) and / or deuterium (D)) of the absorption layer (42) (the total content of both if both hydrogen (H) and deuterium (D) are included) is 0.1 atomic% or more and 30 atomic% or less, preferably 5 atomic% or more, more preferably 10 atomic% or more, and even more preferably greater than 15 atomic%. By including hydrogen (H) and / or deuterium (D) as additive elements in the absorption layer (42), the possibility of new atomic hydrogen (H) entering the absorber film (4) during EUV exposure in an exposure atmosphere containing hydrogen gas can be eliminated. Therefore, by using the reflective mask blank (100) of the present embodiment, the peeling of the absorber pattern (4a) of the reflective mask (200) can be suppressed. Also, if the content of the additive element exceeds 30 atomic%, the film density of the absorption layer (42) decreases, and the decay coefficient (k) becomes smaller, making it difficult to have the function of absorbing EUV light.

[0073] In terms of reducing the intrusion of atomic hydrogen (H) into the absorption layer (42) during EUV exposure in an exposure atmosphere containing hydrogen gas, the same effect can be obtained regardless of whether hydrogen (H) or deuterium (D) is used as the additive element. However, compared to hydrogen (H), deuterium (D) has a stronger bond with other elements, so it can exist stably within the absorption layer (42). Therefore, it is preferable to use deuterium (D) as the additive element of the absorption layer (42).

[0074] As shown in FIG. 3, the absorption layer (42) of the reflective mask blank (100) of the present embodiment preferably includes a lower surface area (46) including a surface on the substrate (1) side and an upper surface area (48) including a surface on the opposite side from the substrate (1).

[0075] Additionally, in the present specification, among the absorption layers (42), the layer including the lower surface area (46) may be referred to as the lower layer. Likewise, the layer including the upper surface area (48) may be referred to as the upper layer. Also, in the example of FIG. 3, the lower layer is identical to the lower surface area (46), the upper layer is identical to the upper surface area (48), and there is no intermediate area.

[0076] As shown in FIG. 3, the lower surface area (46) is an area that includes the surface on the substrate (1) side of the absorption layer (42) of the absorbing film (4). In the example shown in FIG. 3, the lower surface area (46) includes the surface (interface) of the absorption layer (42) of the absorbing film (4) that is in contact with the protective film (3) (referred to as "lower surface" in this specification) and is an area near that surface. Also, the upper surface area (48) is an area that includes the surface on the opposite side from the substrate (1) (referred to as "upper surface" in this specification) of the two surfaces (interfaces) of the absorption layer (42) of the absorbing film (4). In the example shown in FIG. 3, the upper surface area (48) includes the surface that is in contact with the reflectance adjustment layer (44) of the absorbing film (4) and is an area near that surface. The absorption layer (42) may have only two regions: a lower region (46) and an upper region (48). Additionally, the absorption layer (42) may include an intermediate region (not shown) between the lower region (46) and the upper region (48). The lower region (46) and the upper region (48) have different concentrations of the additive element. However, the ratio of the concentrations of elements other than the additive element, particularly the three elements tantalum (Ta), boron (B), and nitrogen (N), can be basically the same. Also, the concentration distribution of a specific element in the lower region (46) and the upper region (48) does not need to be uniform. The concentration of a specific element in the lower region (46) and the upper region (48) may be the average value of the concentration of the specific element within each region.

[0077] In this embodiment, the concentration (atomic %) of the additive element in the lower surface region (46) can be made higher than the concentration (atomic %) of the additive element in the upper surface region (48). By making the concentration of the additive element in the lower surface region (46) higher than that in the upper surface region (48), even if hydrogen attempts to penetrate from the sidewall of the absorber pattern (4a), it is possible to suppress the penetration of hydrogen from the lower surface region (46) to the interface between the absorber layer (42) and the layer below it. Therefore, the peeling of the protective film (3) and the absorber pattern (4a) can be suppressed more reliably. The ratio of the film thickness of the lower surface region (46) to the film thickness of the absorber layer (42) (film thickness of the lower surface region (46) / film thickness of the absorber layer (42)) is preferably 0.1 or higher, and more preferably 0.2 or higher.

[0078] In this embodiment, the concentration (atomic %) of the additive element in the upper surface region (48) can be made higher than the concentration (atomic %) of the additive element in the lower surface region (46). By making the concentration of the additive element in the upper surface region (48) higher than that in the lower surface region (46), hydrogen can be suppressed from penetrating from the surface of the absorber pattern (4a). Therefore, the peeling of the protective film (3) and the absorber pattern (4a) can be suppressed more reliably. The ratio of the film thickness of the upper surface region (48) to the film thickness of the absorber layer (42) (film thickness of the upper surface region (48) / film thickness of the absorber layer (42)) is preferably 0.1 or higher, and more preferably 0.2 or higher.

[0079] The content of the additive element (hydrogen (H) and / or deuterium (D)) may be uniform or substantially uniform throughout the entire absorption layer (42), which includes the lower surface area (46) and the upper surface area (48). Additionally, the content of the additive element may have a predetermined concentration distribution as described above. The addition of the additive element to the absorption layer (42) makes it easy for the film density of the absorber film (4) to decrease. Therefore, it is preferable to perform the addition of the additive element to the absorption layer (42) only in the necessary areas. Accordingly, as described above, it is preferable that the concentration of the additive element in one of the upper surface area (48) and the lower surface area (46) be higher than that in the other. The concentrations in the upper surface area (48) and the lower surface area (46) can be determined by considering the concentration of hydrogen gas in the exposure atmosphere, etc., and examining which of the upper surface area (48) and the lower surface area (46) is prone to hydrogen intrusion.

[0080] An intermediate region may be provided between the lower surface region (46) and the upper surface region (48) of the absorption layer (42). The concentration distribution of the additive element in the intermediate region is arbitrary. When the lower surface region (46), the upper surface region (48), and the intermediate region are included, the concentration distribution of the additive element in the intermediate region may be a distribution that decreases monotonically or increases monotonically in the depth direction. The concentration of the additive element may decrease monotonically from the upper surface region (48) toward the lower surface region (46) in the depth direction of the absorption layer (42). Also, the concentration of the additive element may increase monotonically from the upper surface region (48) toward the lower surface region (46) in the depth direction of the absorption layer (42). The change in the concentration of the additive element in the depth direction may be gradient and may also change (increase or decrease) in a stepwise manner. In this specification, a monotonically decreasing concentration of an element includes a stepwise decrease in the concentration of the element. In this specification, a monotonic increase in the concentration of an element includes an increase in the concentration of an element in a stepwise manner.

[0081] As described above, the material of the absorption layer (42) comprises tantalum (Ta), boron (B) and nitrogen (N), and a predetermined additive element (hydrogen (H) and / or deuterium (D)). The absorption layer (42) may contain carbon (C) and / or oxygen (O) to the extent that the effect of the present embodiment is obtained. The absorption layer (42) is preferably a TaBNH membrane or a TaBND membrane. If one of the lower surface region (46) and the upper surface region (48) does not contain an additive element, it is preferable to use a TaBN membrane.

[0082] The absorption layer (42) made of the above-described material can be formed by a magnetron sputtering method such as DC sputtering and RF sputtering. For example, the absorption layer (42) can be formed by a reactive sputtering method using a noble gas such as argon (Ar) gas, krypton (Kr) gas and / or xenon (Xe) gas, with nitrogen gas and an additive element gas (hydrogen (H) gas and / or deuterium (D) gas) added, using a target containing tantalum and boron. Additionally, the film formed when one of the lower surface area (46) and the upper surface area (48) does not contain an additive element can be formed by a reactive sputtering method using a noble gas with nitrogen gas added, without the additive element gas.

[0083] In addition, in order to incorporate hydrogen into the absorption layer (42), it is desirable to lower the power when forming the film by magnetron sputtering. On the other hand, if the power during film formation is lowered, the tensile stress in the film being formed increases, and there may be other problems such as the deformation amount of the substrate (1) increasing. The inventors have discovered that by defining the composition ratio of hydrogen and nitrogen in the absorption layer (42), the film stress of the absorber film (4) can be reduced, and the peeling of the absorber pattern (4a) can be prevented. That is, in the composition of the absorption layer (42), the nitrogen (N) content is 0.1 atomic% or more and 40 atomic% or less, the additive element content is 0.1 atomic% or more and 30 atomic% or less, and the composition ratio of the additive element to nitrogen (N) (additive element:nitrogen) is 5:95 to 50:50, preferably 15:85 to 40:60, thereby increasing the tensile stress in the thin film of the absorption layer (42) being formed, and thus suppressing other problems such as the deformation amount of the substrate (1) increasing.

[0084] The film thickness of the absorption layer (42) is preferably 30 nm or more, and more preferably 40 nm or more. Also, the film thickness of the absorption layer (42) is preferably 80 nm or less, and more preferably 70 nm or less.

[0085] As shown in FIGS. 1 to 3, the absorbing film (4) of the present embodiment has a reflectance adjusting layer (44) on the side opposite to the substrate (1) above the absorbing layer (42).

[0086] By making the absorbing film (4) into a laminated film having a reflectance adjustment layer (44) on top of the absorbing layer (42) and setting the film thickness of the reflectance adjustment layer (44) to a predetermined film thickness, for example, when inspecting mask pattern defects using inspection light such as DUV light, this reflectance adjustment layer (44) becomes a film that adjusts the reflectance. Therefore, the inspection sensitivity during mask pattern defect inspection can be increased. For example, when the material of the reflectance adjustment layer (44) is TaBO, by setting the film thickness to about 14 nm, it effectively functions as a film that adjusts the reflectance during mask pattern defect inspection.

[0087] The reflectance adjusting layer (44) preferably comprises at least one additive element selected from tantalum (Ta) and oxygen (O), hydrogen (H) and deuterium (D). Similar to the absorption layer (42), by including a specific additive element in the reflectance adjusting layer (44), the intrusion of atomic hydrogen (H) from the reflectance adjusting layer (44) can be suppressed when EUV exposure is performed in an atmosphere containing hydrogen gas. Therefore, a reflective mask (200) can be obtained that can suppress the peeling of the absorber pattern (4a).

[0088] When the reflectance adjusting layer (44) contains a predetermined additive element, the content of the additive element in the reflectance adjusting layer (44) is preferably 0.1 atomic% or more and 30 atomic% or less, and more preferably greater than 15 atomic% and 30 atomic% or less. In addition, the content of the additive element in the reflectance adjusting layer (44) is preferably 10 atomic% or more higher than the content of the additive element in the absorption layer (42). By ensuring that the content of the additive element in the reflectance adjusting layer (44) is within a predetermined range, it becomes more certain to obtain a reflective mask (200) capable of suppressing the peeling of the absorber pattern (4a).

[0089] It is preferable that the reflectance adjusting layer (44) additionally contain boron (B). By having the reflectance adjusting layer (44) contain boron, it becomes easier to amorphize the crystal structure, and it can be made into an absorbing film (4) with excellent smoothness. In order to ensure amorphization, the content of boron (B) in the reflectance adjusting layer (44) is preferably greater than 5 atomic percent, and more preferably 10 atomic percent or more and 30 atomic percent or less.

[0090] As described above, the material of the reflectance adjusting layer (44) comprises tantalum (Ta) and oxygen (O), and, if necessary, a predetermined additive element (hydrogen (H) and / or deuterium (D)) and / or boron (B). The reflectance adjusting layer (44) is preferably a TaO film or a TaBO film. If the reflectance adjusting layer (44) contains an additive element, it is preferable to use a TaOH film (or TaOD film) or a TaBOH film (or TaBOD film).

[0091] The reflectance adjusting layer (44) made of the above-described material can be formed by a magnetron sputtering method such as DC sputtering and RF sputtering. For example, the reflectance adjusting layer (44) containing a predetermined additive element and boron (B) can be formed by a reactive sputtering method using a target containing tantalum and boron, and a noble gas such as argon (Ar) gas, krypton (Kr) gas and / or xenon (Xe) gas to which oxygen gas and additive element gas (hydrogen (H) gas and / or deuterium (D) gas) are added. Also, for example, if the reflectance adjusting layer (44) does not contain a predetermined additive element, the reflectance adjusting layer (44) can be formed by a reactive sputtering method using a target containing tantalum and boron, and a noble gas to which oxygen gas is added. If the reflectance adjusting layer (44) does not contain boron (B), the reflectance adjusting layer (44) can be formed using a target made of tantalum.

[0092] The film thickness of the reflectance adjusting layer (44) is preferably 15 nm or less, and more preferably 8 nm or less. Also, the film thickness of the absorber film (4) is preferably 90 nm or less, and more preferably 80 nm or less. Also, the surface roughness (RMS) of the surface of the absorber film (4) is preferably 0.5 nm or less.

[0093] Ta, which is the material of the absorber film (4) of the present embodiment, is a material that has a large absorption coefficient (decay coefficient) of EUV light and can be easily dry-etched with chlorine-based gas and / or fluorine-based gas. Therefore, Ta can be said to be a material of the absorber film (4) with excellent processability. In addition, by adding B (furthermore, Si and / or Ge, etc.) to Ta, an amorphous material can be easily obtained. As a result, the smoothness of the absorber film (4) can be improved. Also, if N and / or O are added to Ta, the resistance to oxidation of the absorber film (4) is improved, so the effect of improving stability over time is obtained.

[0094] For etching the absorbent membrane (4) of the present embodiment, fluorine-based gases such as CF4, CHF3, C2F6, C3F6, C4F6, C4F8, CH2F2, CH3F, C3F8, SF6, and F2 may be used. Chlorine-based gases such as Cl2, SiCl4, CHCl3, CCl4, and BCl3 may be used. Additionally, these etching gases may additionally include inert gases such as He and / or Ar, as needed.

[0095] In the reflective mask blank (100) of the present embodiment, by using the absorber film (4) described above, a reflective mask (200) can be obtained that suppresses the peeling of the absorber pattern (4a) when EUV exposure is performed in an atmosphere containing hydrogen gas.

[0096] The absorbing film (4) of the present embodiment may be an absorbing film (4) having a phase shift function that also takes into account the phase difference of EUV light. An absorbing film (4) having a phase shift function is one that absorbs EUV light and simultaneously reflects a portion of it to shift the phase. That is, in a reflective mask (200) patterned with an absorbing film (4) having a phase shift function, in the part where the absorbing film (4) is formed, EUV light is absorbed and photosensitive, while a portion of the light is reflected at a level that does not adversely affect pattern transfer. Also, in the area (field part) where the absorbing film (4) is not formed, EUV light is reflected from the multilayer reflective film (2) through the protective film (3). Therefore, a desired phase difference is achieved between the reflected light from the absorbing film (4) having a phase shift function and the reflected light from the field part. The absorber film (4) having a phase shift function is formed such that the phase difference between the reflected light from the absorber film (4) and the reflected light from the multilayer reflector film (2) is 170 degrees to 190 degrees. As the light with an inverted phase difference of approximately 180 degrees interferes with each other at the pattern edge, the image contrast of the projected optical image is improved. Along with the improvement in image contrast, the resolution increases, and various margins related to exposure, such as exposure amount margin and focus margin, can be greatly increased.

[0097] <<Etching mask (6)>>

[0098] The reflective mask blank (100) of the present embodiment may have an etching mask film (6) on top of an absorbent film (4).

[0099] Materials for the etching mask film (6) that have a high etching selectivity ratio of the absorber film (4) (particularly the reflectance adjustment layer (44)) to the etching mask film (6) may include materials of chromium and chromium compounds. In this case, the absorber film (4) may be etched with a fluorine-based gas or a chlorine-based gas. As for chromium compounds, materials containing chromium (Cr) and at least one element selected from nitrogen (N), oxygen (O), carbon (C), and boron (B) may be included. Examples of chromium compounds include CrN, CrC, CrO, CrON, CrOC, CrCN, CrCON, CrBN, CrBC, CrBO, CrBON, CrBCN, and CrBOCN. Additionally, materials to which hydrogen (H) and / or deuterium (D) is added to these chromium compounds may be included. To increase the etching selectivity ratio in a chlorine-based gas, it is preferable to make the etching mask film (6) a material that substantially does not contain oxygen. Examples of chromium compounds that substantially do not contain oxygen include CrN, CrC, CrCN, CrBN, CrBC, and CrBCN, and materials to which H and / or D are added to these chromium compounds. The Cr content of the chromium compound of the etching mask film (6) is preferably 50 atomic% or more and less than 100 atomic%, and more preferably 80 atomic% or more and less than 100 atomic%. Also, "substantially not containing oxygen" corresponds to the oxygen content in the chromium compound being 10 atomic% or less, preferably 5 atomic% or less. Additionally, the above material may contain a metal other than chromium within the range in which the effects of the embodiments of the present invention are obtained.

[0100] When an etching mask film (6) is formed, it is possible to reduce the film thickness of the resist film (11), which is advantageous for miniaturizing the pattern. The film thickness of the etching mask film (6) is preferably 3 nm or more from the perspective of obtaining the function of an etching mask that forms a transfer pattern on the absorber film (4) with high precision. In addition, the film thickness of the etching mask film (6) is preferably 15 nm or less, and more preferably 10 nm or less, from the perspective of reducing the film thickness of the resist film (11).

[0101] <<Resist film (11)>>

[0102] The reflective mask blank (100) of the present embodiment may have a resist film (11) on top of the absorber film (4) (on top of the etching mask film (6) if the etching mask film (6) is formed). The reflective mask blank (100) of the present embodiment also includes a form having a resist film (11). In the reflective mask blank (100) of the present embodiment, the resist film (11) can be made thin by selecting an absorber film (4) (absorption layer (42) and reflectance adjustment layer (44)) of a suitable material and / or a suitable film thickness and an etching gas.

[0103] For example, a chemically-amplified resist (CAR) can be used as the material for the resist film (11). By patterning the resist film (11) and etching the absorber film (4) (absorption layer (42) and reflectance adjustment layer (44)), a reflective mask (200) having a predetermined transfer pattern can be manufactured.

[0104] <<Reverse Challenge Bar (5)>>

[0105] On the second main surface (back side) of the substrate (1) (opposite side to the surface on which the multilayer reflective film (2) is formed), a back conductive film (5) for an electrostatic chuck is generally formed. The electrical characteristics (sheet resistance) required for the back conductive film (5) for an electrostatic chuck are typically 100Ω / □ (Ω / Square) or less. The method of forming the back conductive film (5) can be, for example, by magnetron sputtering or ion beam sputtering, using a target of a metal or alloy such as chromium or tantalum.

[0106] The material containing chromium (Cr) of the back conductive film (5) is preferably a Cr compound containing at least one element selected from boron, nitrogen, oxygen, and carbon in Cr. Examples of Cr compounds include CrN, CrON, CrCN, CrCON, CrBN, CrBON, CrBCN, and CrBOCN.

[0107] As for the material containing tantalum (Ta) of the back conductive film (5), it is preferable to use Ta (tantalum), an alloy containing Ta, or a Ta compound containing at least one of boron, nitrogen, oxygen, and carbon in any of these. Examples of Ta compounds include TaB, TaN, TaO, TaON, TaCON, TaBN, TaBO, TaBON, TaBCON, TaHf, TaHfO, TaHfN, TaHfON, TaHfCON, TaSi, TaSiO, TaSiN, TaSiON, and TaSiCON.

[0108] For a material containing tantalum (Ta) or chromium (Cr), it is preferable that the nitrogen (N) present in the surface layer is low. Specifically, it is preferable that the nitrogen content in the surface layer of the back conductive film (5) of the material containing tantalum (Ta) or chromium (Cr) is less than 5 atomic percent, and it is more preferable that the surface layer substantially does not contain nitrogen. This is because, in the back conductive film (5) of the material containing tantalum (Ta) or chromium (Cr), the lower the nitrogen content in the surface layer, the higher the wear resistance.

[0109] The back conductive film (5) is preferably made of a material containing tantalum and boron. By making the back conductive film (5) of a material containing tantalum and boron, a back conductive film (5) having wear resistance and chemical resistance can be obtained. When the back conductive film (5) contains tantalum (Ta) and boron (B), the B content is preferably 5 to 30 atomic percent. The ratio of Ta and B (Ta:B) in the sputtering target used for forming the back conductive film (5) is preferably 95:5 to 70:30.

[0110] The thickness of the back conductive film (5) is not particularly limited as long as it satisfies the function as an electrostatic chuck. The thickness of the back conductive film (5) is typically 10 nm to 200 nm. In addition, this back conductive film (5) also serves to adjust stress on the second main side of the mask blank (100). The back conductive film (5) is adjusted to balance stress from various films formed on the first main side so as to obtain a flat reflective mask blank (100).

[0111] <Reflective mask (200) and method of manufacturing the same>

[0112] The reflective mask (200) of the present embodiment has an absorbent pattern (4a) in which the absorbent film (4) of the reflective mask blank (100) described above is patterned.

[0113] Since the absorber pattern (4a) of the reflective mask (200) absorbs EUV light and can reflect EUV light from the opening of the absorber pattern (4a), a predetermined fine transfer pattern can be transferred to the object to be transferred by irradiating EUV light onto the reflective mask (200) using a predetermined optical system.

[0114] A reflective mask (200) is manufactured using the reflective mask blank (100) of the present embodiment. Here, only a general description is provided, and it will be described in detail later in the examples. Also, here, as shown in FIGS. 4a to 4d, the case in which the reflective mask blank (100) is equipped with an etching mask film (6) is described.

[0115] A reflective mask blank (100) is prepared, and a resist film (11) is formed on an etching mask film (6) formed on an absorbing film (4) on the first main surface (see FIG. 4a; not required if the reflective mask blank (100) is equipped with a resist film (11), and a desired pattern is drawn (exposed) on the resist film (11), and a predetermined resist pattern (11a) is formed by further developing and rinsing (see FIG. 4b).

[0116] In the case of a reflective mask blank (100), the etching mask film (6) is etched using the resist pattern (11a) as a mask to form an etching mask pattern (6a) (see FIG. 4c). The resist pattern (11a) is peeled off by a wet treatment such as oxygen ashing or thermal sulfuric acid. Next, the absorber film (4) (reflectance adjustment layer (44) and absorption layer (42)) is etched using the etching mask pattern (6a) as a mask to form an absorber pattern (4a) (reflectance adjustment layer pattern (44a) and absorption layer pattern (42a)) (see FIG. 4d). The etching mask pattern (6a) is removed to form an absorber pattern (4a) (reflectance adjustment layer pattern (44a) and absorption layer pattern (42a)) (see FIG. 4e). Finally, a reflective mask (200) can be manufactured by performing wet cleaning using an acidic or alkaline aqueous solution.

[0117] In addition, the etching mask pattern (6a) can also be removed by etching it simultaneously with the absorption layer (42) when patterning the absorption layer (42).

[0118] In the reflective mask (200) of the present embodiment, the etching mask pattern (6a) can be left on the absorber pattern (4a) without being removed. However, in that case, it is necessary to leave the etching mask pattern (6a) as a uniform thin film. In order to avoid non-uniformity of the etching mask pattern (6a) as a thin film, in the reflective mask (200) of the present embodiment, it is preferable to remove the etching mask pattern (6a) without placing it.

[0119] In the method for manufacturing the reflective mask (200) of the present embodiment, it is preferable to pattern the etching mask film (6) of the reflective mask blank (100) of the present embodiment described above using a dry etching gas containing a chlorine-based gas and an oxygen gas. In the case of an etching mask film (6) containing chromium (Cr), dry etching can be suitably performed using a chlorine-based gas and an oxygen gas. In addition, it is preferable to pattern the reflectance adjustment layer (44) using a dry etching gas containing a fluorine-based gas. In the case of a reflectance adjustment layer (44) made of a material containing tantalum (Ta) and oxygen (O), dry etching can be suitably performed using a fluorine-based gas. It is preferable to pattern the absorption layer (42) using a dry etching gas containing a fluorine-based gas or a chlorine-based gas that does not contain oxygen. In the case of an absorption layer (42) made of a material containing tantalum (Ta) and nitrogen (N), dry etching can be suitably performed using a fluorine-based gas or a chlorine-based gas that does not contain oxygen. In this way, an absorber pattern (4a) of a reflective mask (200) can be formed.

[0120] By the above process, when EUV exposure is performed in an atmosphere containing hydrogen gas, a reflective mask (200) can be obtained that can suppress the peeling of the absorber pattern (4a).

[0121] <Method for manufacturing a semiconductor device>

[0122] The method for manufacturing a semiconductor device according to the present embodiment includes a process of setting a reflective mask (200) of the present embodiment in an exposure device having an exposure light source that emits EUV light, and transferring a transfer pattern onto a resist film formed on a substrate to be transferred.

[0123] In the method for manufacturing a semiconductor device according to the present embodiment, since the above-described reflective mask blank (100) is used for manufacturing, the peeling of the absorber pattern (4a) can be suppressed when EUV exposure is performed in an atmosphere containing hydrogen gas using the reflective mask (200) of the present embodiment. Therefore, when manufacturing a semiconductor device, a semiconductor device having a fine and high-precision transfer pattern can be manufactured with a high yield.

[0124] By performing EUV exposure using the reflective mask (200) of the above embodiment, a desired transfer pattern based on the absorber pattern (4a) on the reflective mask (200) can be formed on a semiconductor substrate. In addition to this lithography process, a semiconductor device with a desired electronic circuit formed can be manufactured by undergoing various processes such as etching of the film to be processed, formation of an insulating film and a conductive film, introduction of a dopant, and annealing.

[0125] To explain in more detail, the EUV exposure apparatus is composed of a laser plasma light source that generates EUV light, an illumination optical system, a mask stage system, a reduction projection optical system, a wafer stage system, and vacuum equipment. The light source is equipped with a debris trap function, a cut filter that cuts long-wavelength light other than the exposure light, and equipment for differential vacuum exhaust. The illumination optical system and the reduction projection optical system are composed of reflective mirrors. The reflective mask (200) for EUV exposure is electrostatically adsorbed by a conductive film formed on its second main surface and placed on the mask stage.

[0126] Light from an EUV light source is irradiated onto a reflective mask (200) through an illumination optical system at an angle tilted from 6° to 8° relative to the vertical plane of the reflective mask (200). The reflected light from the reflective mask (200) in response to this incident light is reflected (specularly reflected) in the opposite direction to the incident light and at an angle equal to the incident angle, and is guided to a reflective projection optical system having a reduction ratio of typically 1 / 4, thereby performing exposure to a resist on a wafer (semiconductor substrate) placed on a wafer stage. During this process, at least the area through which the EUV light passes is vacuum-evacuated. Additionally, hydrogen gas is introduced into the atmosphere during exposure to prevent exposure contamination. Furthermore, in this exposure, scan exposure, which involves scanning the mask stage and the wafer stage at a speed corresponding to the reduction ratio of the reduction projection optical system and performing exposure through a slit, is the mainstream method. Then, by developing the exposed resist film, a resist pattern can be formed on the semiconductor substrate. In this embodiment, a reflective mask (200) is used to suppress the peeling of the absorber pattern (4a) when EUV exposure is performed in an atmosphere containing hydrogen gas. Therefore, even if the reflective mask (200) of this embodiment is used repeatedly for EUV exposure, the resist pattern formed on the semiconductor substrate has high dimensional accuracy. Then, by using this resist pattern as a mask and performing etching, etc., a predetermined wiring pattern can be formed on the semiconductor substrate, for example. A semiconductor device is manufactured by undergoing other necessary processes such as such an exposure process, a process for processing the film to be processed, a process for forming an insulating film or a conductive film, a process for introducing a dopant, or an annealing process.

[0127] Examples

[0128] Hereinafter, embodiments will be described with reference to the drawings. In addition, in the embodiments, the same reference numerals are used for like components, and descriptions are simplified or omitted.

[0129] In the following description, the elemental composition of Ta, B, N, and O of the deposited thin film was measured by X-ray photoelectron spectroscopy (XPS), and the elemental composition of H was measured by elastic semiconductor detection analysis (ERDA).

[0130] [Example 1]

[0131] The reflective mask blank (100) of Example 1 will be described. As shown in FIG. 1, the reflective mask blank (100) of Example 1 has a back conductive film (5), a substrate (1), a multilayer reflective film (2), a protective film (3), and an absorber film (4). The absorber film (4) is composed of an absorption layer (42) and a reflectance adjustment layer (44). Then, as shown in FIG. 5a, a resist film (11) is formed on the absorber film (4). FIG. 5a to FIG. 5e are schematic cross-sectional views of the main parts showing the process of manufacturing a reflective mask (200) from the reflective mask blank (100).

[0132] The substrate (1) of Example 1 was manufactured as follows. Specifically, a SiO2-TiO2 glass substrate, which is a low thermal expansion glass substrate of size 6025 (approx. 152 mm × 152 mm × 6.35 mm) with both main surfaces of the first main surface and the second main surface polished, was prepared and used as the substrate (1). Polishing was performed, consisting of a coarse polishing process, a precision polishing process, a localized process, and a touch polishing process, in order to obtain a flat and smooth main surface.

[0133] On the second main surface (back surface) of a SiO2-TiO2-based glass substrate (1), a back surface conductive film (5) made of a CrN film was formed by magnetron sputtering (reactive sputtering) under the following conditions.

[0134] Conditions for forming the back-side conductive film (5): Cr target, mixed gas atmosphere of Ar and N2 (Ar: 90%, N: 10%), film thickness 20 nm.

[0135] Next, a multilayer reflective film (2) was formed on the main surface (first main surface) of the substrate (1) opposite to the side on which the back conductive film (5) was formed. The multilayer reflective film (2) formed on the substrate (1) was made into a periodic multilayer reflective film (2) composed of Mo and Si in order to be a multilayer reflective film (2) suitable for EUV light of a wavelength of 13.5 nm. The multilayer reflective film (2) was formed by alternately stacking Mo layers and Si layers on the substrate (1) by using a Mo target and a Si target and an ion beam sputtering method in an Ar gas atmosphere. First, a Si film was deposited to a thickness of 4.2 nm, and then a Mo film was deposited to a thickness of 2.8 nm. This was done as one cycle, and 40 cycles were stacked in the same manner, and finally, a Si film was deposited to a thickness of 4.0 nm to form the multilayer reflective film (2). Here, 40 cycles were used, but this is not limited to this; for example, 60 cycles may be used. If 60 cycles are used, the number of process steps increases compared to 40 cycles, but the reflectivity to EUV light can be increased.

[0136] Next, a protective film (3) made of RuNb film was formed with a film thickness of 2.5 nm by ion beam sputtering using a RuNb target in an Ar gas atmosphere.

[0137] Next, an absorbent film (4) consisting of an absorption layer (42) and a reflectance adjustment layer (44) was formed on the protective film (3). In addition, Table 1 shows the materials, film thickness, type of gas used during film formation (sputtering), hydrogen (H) content, boron (B) content, and composition ratio of the materials for the protective film (3), absorption layer (42), and reflectance adjustment layer (44) of Example 1. In Table 1, "at%" in the material content and composition ratio means atomic %. In Table 1, "RMS (nm)" indicates the root mean square roughness (RMS) of the mask blank after forming the absorbent film (4).

[0138] Specifically, first, an absorption layer (42) made of a TaBNH film was formed by DC magnetron sputtering. The TaBNH film was formed with the film thickness shown in Table 1 by reactive sputtering in a mixed gas atmosphere of Xe gas, N2 gas, and H2 gas using a TaB mixed sintering target.

[0139] Table 1 shows the elemental ratio of the TaBNH membrane (absorption layer (42)) of Example 1.

[0140] Next, a reflectance adjustment layer (44) made of a TaBO film was formed by magnetron sputtering. The TaBO film was formed with the film thickness shown in Table 1 by reactive sputtering in a mixed gas atmosphere of Ar gas and O2 gas using a TaB mixed sintering target.

[0141] Table 1 shows the elemental ratio of the TaBO film (reflectance adjusting layer (44)) of Example 1. Also, Table 1 shows the root mean square roughness RMS after the formation of the TaBO film (reflectance adjusting layer (44)).

[0142] As described above, the reflective mask blank (100) of Example 1 was manufactured.

[0143] Next, the reflective mask (200) of Example 1 was manufactured using the reflective mask blank (100) of Example 1.

[0144] A resist film (11) with a thickness of 150 nm was formed on the absorber film (4) of the reflective mask blank (100) (Fig. 5a). A chemically amplified resist (CAR) was used to form the resist film (11). A desired pattern was drawn (exposed) on the resist film (11), and a predetermined resist pattern (11a) was formed by further developing and rinsing (Fig. 5b). Next, using the resist pattern (11a) as a mask, a reflectance adjustment layer pattern (44a) was formed by performing dry etching of the TaBO film (reflectance adjustment layer (44)) using CF4 gas (Fig. 5c). After that, the TaBNH film (absorber layer (42)) was patterned by dry etching using Cl2 gas to form an absorber layer pattern (42a) (Fig. 5d).

[0145] After that, the resist pattern (11a) was peeled off by oxygen ashing (Fig. 5e). Finally, wet cleaning was performed using pure water (DIW) to produce the reflective mask (200) of Example 1.

[0146] In addition, if necessary, mask defect inspection can be performed after wet cleaning to properly correct mask defects.

[0147] The reflective mask (200) prepared in Example 1 was set in an EUV scanner, and EUV exposure was performed on a wafer having a workpiece film and a resist film formed on a semiconductor substrate. In order to prevent exposure contamination, hydrogen gas was introduced into the atmosphere during the exposure. Then, by developing the exposed resist film, a resist pattern was formed on the semiconductor substrate having the workpiece film formed.

[0148] By transferring this resist pattern to a workpiece by etching, and by undergoing various processes such as forming an insulating film and a conductive film, introducing a dopant, and annealing, it was possible to manufacture a semiconductor device having desired characteristics.

[0149] EUV exposure was performed by introducing hydrogen gas into the atmosphere during exposure using the reflective mask (200) of Example 1, repeating the exposure 1,000 times. After 1,000 exposures, the peeling of the absorber pattern (4a) of the reflective mask (200) of Example 1 was evaluated, and it was confirmed that no peeling occurred.

[0150] [Example 2]

[0151] The reflective mask blank (100) of Example 2 will be described. The reflective mask blank (100) of Example 2 is the same as the reflective mask blank (100) of Example 1, except that the hydrogen content of the absorption layer (42) is different from that of Example 1. Table 1 shows the composition of the absorption layer (42) of Example 2. That is, in the reflective mask blank (100) of Example 2, only the flow rate of H2 gas in the mixed gas during reactive sputtering was changed so that the composition of the absorption layer (42) shown in Table 1 would be formed during the film formation of the absorption layer (42).

[0152] Table 1 shows the elemental ratio of the TaBNH film (absorption layer (42)) of Example 2. The elemental ratio of the TaBO film (reflectance adjusting layer (44)) of Example 2 was the same as that of Example 1.

[0153] As described above, the reflective mask blank (100) of Example 2 was manufactured.

[0154] Next, using the reflective mask blank (100) of Example 2, the reflective mask (200) of Example 2 was manufactured in the same manner as in Example 1. As in Example 1, the peeling of the absorber pattern (4a) of the reflective mask (200) of Example 2 was evaluated, and it was confirmed that no peeling occurred.

[0155] [Example 3]

[0156] The reflective mask blank (100) of Example 3 will be described. The reflective mask blank (100) of Example 3 is similar to the reflective mask blank (100) of Example 1, except that the reflectance adjusting layer (44) contains hydrogen. Table 1 shows the composition of the absorption layer (42) of Example 3. That is, for the reflective mask blank (100) of Example 3, a mixed gas of Ar gas, O2 gas, and H2 gas was used as the mixed gas during reactive sputtering so that the reflectance adjusting layer (44) had the composition shown in Table 1 when forming the reflectance adjusting layer (44).

[0157] Table 1 shows the elemental ratios of the TaBNH film (absorption layer (42)) and the TaBOH film (reflectance adjustment layer (44)) of Example 3.

[0158] As described above, the reflective mask blank (100) of Example 3 was manufactured.

[0159] Next, using the reflective mask blank (100) of Example 3, the reflective mask (200) of Example 3 was manufactured in the same manner as in Example 1. In the same manner as in Example 1, the peeling of the absorber pattern (4a) of the reflective mask (200) of Example 3 was evaluated, and it was confirmed that no peeling occurred.

[0160] [Example 4]

[0161] The reflective mask blank (100) of Example 4 will be described. The reflective mask blank (100) of Example 4 is similar to the reflective mask blank (100) of Example 1, except that the absorption layer (42) consists of a lower layer, which is a lower surface region (46), and an upper layer, which is an upper surface region (48). Table 1 shows the composition of the absorption layer (42) of Example 4. That is, for the reflective mask blank (100) of Example 4, a mixed gas of Xe gas, N2 gas, and H2 gas was used as the mixed gas during reactive sputtering so that the composition of the lower layer shown in Table 1 would be obtained when forming the film of the lower layer, which is the lower surface region (46). Also, when forming the upper layer of the upper surface region (48), a mixture of Xe gas and N2 gas was used as the mixed gas for reactive sputtering, so that the composition of the upper layer shown in Table 1 is formed.

[0162] Table 1 shows the elemental ratios of the TaBNH membrane (lower layer of the absorption layer (42)) and the TaBN membrane (upper layer of the absorption layer (42)) of Example 4.

[0163] As described above, the reflective mask blank (100) of Example 4 was manufactured.

[0164] Next, using the reflective mask blank (100) of Example 4, the reflective mask (200) of Example 4 was manufactured in the same manner as in Example 1. At this time, as an absorber pattern (4a), a pattern was formed such that a sparse area and a dense area were formed. As in Example 1, the peeling of the absorber pattern (4a) of the reflective mask (200) of Example 4 was evaluated, and it was confirmed that no peeling occurred in either the sparse area or the dense area of ​​the pattern.

[0165] [Example 5]

[0166] The reflective mask blank (100) of Example 5 will be described. The reflective mask blank (100) of Example 5 is similar to the reflective mask blank (100) of Example 4, except that the lower layer, which is the lower surface region (46), of the absorption layer (42) does not contain hydrogen, and the upper layer, which is the upper surface region (48), contains hydrogen. Table 1 shows the composition of the absorption layer (42) of Example 5. That is, in the reflective mask blank (100) of Example 5, when forming the film of the lower layer, which is the lower surface region (46), a mixture of Xe gas and N2 gas was used as the mixed gas during reactive sputtering, rather than H2 gas, so that the composition of the lower layer shown in Table 1 is obtained. Also, when forming the upper layer of the upper surface region (48), a mixture of Xe gas, N2 gas and H2 gas was used as the mixed gas for reactive sputtering so that the composition of the upper layer shown in Table 1 was formed.

[0167] Table 1 shows the elemental ratios of the TaBN membrane (lower layer of the absorption layer (42)) and the TaBNH membrane (upper layer of the absorption layer (42)) of Example 5.

[0168] As described above, the reflective mask blank (100) of Example 5 was manufactured.

[0169] Next, using the reflective mask blank (100) of Example 5, the reflective mask (200) of Example 5 was manufactured in the same manner as in Example 1. At this time, as an absorber pattern (4a), a pattern was formed such that a sparse area and a dense area were formed. As in Example 1, the peeling of the absorber pattern (4a) of the reflective mask (200) of Example 5 was evaluated, and it was confirmed that peeling occurred in the sparse area of ​​the pattern, but not in the dense area of ​​the pattern.

[0170] [Example 6]

[0171] The reflective mask blank (100) of Example 6 will be described. The reflective mask blank (100) of Example 6 is the same as the reflective mask blank (100) of Example 1, except that the absorption layer (42) contains deuterium (instead of hydrogen). Table 1 shows the composition of the absorption layer (42) of Example 6. That is, in the reflective mask blank (100) of Example 6, the absorption layer (42) was formed using D2 gas instead of H2 gas in the mixed gas during reactive sputtering so that the composition of the absorption layer (42) shown in Table 1 would be formed during the formation of the absorption layer (42).

[0172] Table 1 shows the elemental ratios of the TaBND film (absorption layer (42)) and the TaBO film (reflectance adjusting layer (44)) of Example 6. The elemental ratios of the TaBO film (reflectance adjusting layer (44)) of Example 6 were the same as those of Example 1.

[0173] As described above, the reflective mask blank (100) of Example 6 was manufactured.

[0174] Next, using the reflective mask blank (100) of Example 6, the reflective mask (200) of Example 6 was manufactured in the same manner as in Example 1. As in Example 1, the peeling of the absorber pattern (4a) of the reflective mask (200) of Example 6 was evaluated, and it was confirmed that no peeling occurred.

[0175] [Comparative Example 1]

[0176] As Comparative Example 1, a mask blank (100) was manufactured with a TaBN film as the absorption layer (42). Comparative Example 1 is basically the same as Example 1, except that the absorption layer (42) is a TaBN film (single layer film). The formation of the TaBN film of the absorption layer (42) was performed in the same way as the TaBN film that is the upper layer of the absorption layer (42) of Example 4.

[0177] Next, using the reflective mask blank (100) of Comparative Example 1, the reflective mask (200) of Comparative Example 1 was manufactured in the same manner as in Example 1.

[0178] The reflective mask (200) prepared in Comparative Example 1 was set in an EUV scanner, and EUV exposure was performed on a wafer having a workpiece film and a resist film formed on a semiconductor substrate. In order to prevent exposure contamination, hydrogen gas was introduced into the atmosphere during the exposure. Then, by developing the exposed resist film, a resist pattern was formed on the semiconductor substrate having the workpiece film formed.

[0179] EUV exposure was performed by introducing hydrogen gas into the atmosphere during exposure using the reflective mask (200) of Comparative Example 1, for 1,000 repetitions. After 1,000 exposures, the peeling of the absorber pattern (4a) of the reflective mask (200) of Comparative Example 1 was evaluated, and it was confirmed that peeling had occurred.

[0180] [Table 1]

[0181] Explanation of the symbols

[0182] 1: Substrate 2: Multilayer reflective film 3: Protective barrier 4: Absorbent membrane 4a: Absorber pattern 5: Backside conductive film 6: Etching mask film 6a: Etching mask pattern 11: Resist film 11a: Resist pattern 42: Absorbent layer 42a: Absorbent layer pattern 44: Reflectance adjustment layer 44a: Reflectance adjustment layer pattern 46: Bottom surface area 48: Top surface area 100: Reflective mask blank 200: Reflective mask

Claims

Claim 1 A reflective mask blank comprising a substrate, a multilayer reflective film on the substrate, and an absorber film on the multilayer reflective film, wherein the absorber film comprises an absorption layer and a reflectance adjusting layer, wherein the absorption layer comprises at least one additive element selected from hydrogen (H) and deuterium (D) together with tantalum (Ta), boron (B), and nitrogen (N), the content of the boron (B) in the absorption layer is greater than 5 atomic percent and less than or equal to 30 atomic percent, the content of the additive element in the absorption layer is greater than or equal to 0.1 atomic percent and less than or equal to 30 atomic percent, and the reflectance adjusting layer comprises at least one additive element selected from hydrogen (H) and deuterium (D) together with tantalum (Ta) and oxygen (O). Claim 2 A reflective mask blank according to claim 1, wherein the reflectance adjusting layer further comprises boron (B), and the content of the boron (B) is greater than 5 atomic percent and less than or equal to 30 atomic percent. Claim 3 A reflective mask blank according to claim 1 or 2, characterized in that the concentration (atomic %) of the additive element in the region from the surface on the substrate side to 10% of the film thickness of the absorption layer is higher than the concentration (atomic %) of the additive element in the region from the surface on the side opposite to the substrate to 10% of the film thickness of the absorption layer. Claim 4 A reflective mask blank according to claim 1 or 2, characterized in that the concentration (atomic %) of the additive element in the region from the surface opposite to the substrate to 10% of the film thickness of the absorption layer is higher than the concentration (atomic %) of the additive element in the region from the surface on the substrate side to 10% of the film thickness of the absorption layer. Claim 5 A reflective mask blank according to claim 1 or 2, wherein the protective film is included between the multilayer reflective film and the absorbent film, and the protective film comprises at least one additive element selected from ruthenium (Ru), hydrogen (H), and deuterium (D). Claim 6 A reflective mask characterized in that the absorbent film in the reflective mask blank described in claim 1 or 2 has a patterned absorbent pattern. Claim 7 A method for manufacturing a reflective mask characterized by patterning the absorbent film of the reflective mask blank described in claim 1 or 2 to form an absorbent pattern. Claim 8 A method for manufacturing a semiconductor device characterized by having a process of setting a reflective mask described in claim 6 in an exposure device having an exposure light source that emits EUV light, and transferring a transfer pattern onto a resist film formed on a substrate to be transferred. Claim 9 delete

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