JP2020160354A - Substrate having multilayer reflection film, reflection type mask blank, reflection type mask and method for manufacturing semiconductor device - Google Patents

Abstract

To provide a reflection type mask blank including a multilayer reflection film having high reflectance to exposure light and having a low background level when inspecting a defect; and a substrate having a multilayer reflection film used for manufacturing a reflection type mask.SOLUTION: A substrate having a multilayer reflection film includes the multilayer reflection film consisting of a multilayer film obtained by alternately laminating a low refractive index layer and a high refractive index layer on a substrate and for reflecting exposure light. The multilayer reflection film includes an upper layer and a lower layer arranged between the upper layer and the substrate. The lower layer includes at least one additive element selected from boron (B), carbon (C), zirconium (Zr), nitrogen (N), oxygen (O) and hydrogen (H). The upper layer does not substantially include the additive elements.SELECTED DRAWING: Figure 1

Description

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

In recent years, in the semiconductor industry, with the high integration of semiconductor devices, a fine pattern exceeding the transfer limit of the conventional photolithography method using ultraviolet light has been required. In order to enable such fine pattern formation, EUV lithography, which is an exposure technique using extreme ultraviolet (hereinafter referred to as "EUV") light, is promising. Here, EUV light refers to light in a wavelength band of a soft X-ray region or a vacuum ultraviolet region, and specifically, light having a wavelength of about 0.2 to 100 nm. A reflective mask has been proposed as a transfer mask used in this EUV lithography. In such a reflective mask, a multilayer reflective film that reflects the exposure light is formed on the substrate, and an absorber film that absorbs the exposure light is formed in a pattern on the multilayer reflective film.

The light incident on the reflective mask set in the exposure apparatus is absorbed by the portion with the absorber film and reflected by the multilayer reflective film in the portion without the absorber film. The reflected image is transferred onto the semiconductor substrate through the catadioptric system to form a mask pattern. As the multilayer reflective film, for example, one that reflects EUV light having a wavelength of 13 to 14 nm, a film in which Mo and Si having a thickness of several nm are alternately laminated, and the like are known.

As a technique for manufacturing a substrate with a multilayer reflective film having such a multilayer reflective film, Patent Document 1 describes a vacuum chamber for arranging the substrate in a vacuum and a multilayer stack without removing the substrate from the vacuum. An integrated extreme ultraviolet blank production system is described that includes a deposition system for deposition and a processing system for processing layers on a multi-layer stack deposited as an amorphous metal layer. As the amorphous metal layer, it is described that it is alloyed with amorphous molybdenum and boron, nitrogen, or carbon.

Patent Document 2 describes that in a multilayer reflector having a multilayer structure composed of alternating layers of high absorption layers and low absorption layers of soft X-rays or vacuum ultraviolet rays, the high absorption layer is one or more of a single transition metal. A multilayer film reflector for soft X-rays or vacuum ultraviolet rays is described, wherein the low absorption layer has either silicon nitride or boron nitride as a main component. There is.

Patent Document 3 states that in a multilayer reflector having a multilayer structure composed of alternating layers of high absorption layers and low absorption layers of soft X-rays and vacuum ultraviolet rays, the high absorption layers are bismuth or lead alone or each of them. The low absorption layer is characterized by having one or more of carbon, silicon, boron or beryllium as a main component of the above-mentioned compounds. Multilayer film reflectors for use are described.

Patent Document 4 describes in a multilayer film reflector for soft X-rays / vacuum ultraviolet rays having a multilayer thin film structure composed of alternating layers of high absorption layers and low absorption layers of soft X-rays / vacuum ultraviolet rays, the high absorption layer is a transition metal. The main component is one or more of the boride, carbide, silicide, nitride or oxide of the above, and the low absorption layer is a simple substance of carbon, silicon, boron or berylium or a compound thereof. A multilayer film reflector for soft X-rays and vacuum ultraviolet rays, which comprises one or more of the above as a main component, is described.

Special Table 2016-591329 Patent No. 2566564 JP-A-63-88501 Special Fairness 7-97159

The substrate with a multilayer reflective film is a substrate with a multilayer reflective film, that is, from the viewpoint of improving the defect quality due to the miniaturization of patterns in recent years and the optical characteristics (surface reflectance of the multilayer reflective film, etc.) required for the reflective mask. , The interface of each layer of the multilayer reflective film and / or the surface of the multilayer reflective film is required to have higher smoothness. To improve the defect quality of the multi-layer reflective film substrate, the surface of the multi-layer reflective film-equipped substrate, that is, the interface and / or the multi-layer reflective film surface of each layer of the multi-layer reflective film, is smoothed to smooth the multi-layer reflective film. By reducing the roughness of the interface of each layer and / or the noise (background noise) caused by the surface roughness of the surface of the multilayer reflective film, it is possible to detect minute defects (defect signals) existing in the substrate with the multilayer reflective film. can do. The multilayer reflective film is formed by alternately laminating high refractive index layers and low refractive index layers on the surface of a mask blank substrate. Each of these layers is generally formed by sputtering using a sputtering target made of a material for forming the layers.

As a sputtering method, since it is not necessary to generate plasma by electric discharge, ion beam sputtering is used because impurities are not easily mixed in the multilayer reflective film and the ion source is independent and the conditions can be set relatively easily. It is preferably carried out. From the viewpoint of the smoothness of each layer of the formed multilayer reflective film and the in-plane uniformity of the film thickness of each layer, a large angle with respect to the normal of the main surface of the mask blank substrate (the straight line orthogonal to the main surface). That is, the sputter particles are made to reach at an oblique angle or an angle close to parallel to the main surface of the substrate to form a high refractive index layer and a low refractive index layer.

At the time of exposure using a reflective mask, the exposure light is absorbed by the absorber film formed in a pattern, and the exposure light is reflected by the multilayer reflection film at the portion where the multilayer reflection film is exposed. In order to obtain high contrast during exposure, it is desirable that the reflectance of the multilayer reflective film to the exposure light is high.

In order to increase the reflectance of the multilayer reflective film to the exposure light, it is conceivable to improve the crystallinity of each layer constituting the multilayer reflective film (increasing the crystal grain size). However, when the crystal grain size is increased, the noise (background level: BGL) at the time of defect inspection becomes high, and there arises a problem that the time required for defect inspection increases. This is because if the background level during defect inspection becomes too high, noise will be detected as defects, and it will take a long time to determine the actual defects that contribute to transfer and the pseudo defects that do not contribute to transfer. caused by. Further, when the background level at the time of defect inspection becomes high, there is a problem that the actual defect contributing to transfer is erroneously determined as noise and is not detected. It is considered that the reason why the problem of high background level occurs is that the crystal particles become coarse and the smoothness of the interface of each layer of the multilayer reflective film and / or the surface of the multilayer reflective film deteriorates. Deterioration of the smoothness of the interface and / or the surface of the multilayer reflective film of each layer of the multilayer reflective film increases the scattering of the inspection light irradiated during the defect inspection, which causes an increase in the background level during the defect inspection. Is possible.

Therefore, an object of the present invention is to provide a reflective mask blank and a reflective mask having a multilayer reflective film having a high reflectance to exposure light and a low background level at the time of defect inspection. Further, the present invention is a substrate with a multilayer reflective film used for manufacturing a reflective mask blank and a reflective mask having a multilayer reflective film having a high reflectance to exposure light and a low background level at the time of defect inspection. The purpose is to provide. A further object of the present invention is to provide a method for manufacturing a semiconductor device using the reflective mask.

Another object of the present invention is to obtain a substrate with a multilayer reflective film, a reflective mask blank, and a reflective mask that can reliably detect actual defects that contribute to transfer.

The present inventors have a lower layer (crystal grain size) having a laminated film in which low refractive index layers having amorphous or finely divided crystal grains and high refractive index layers are alternately laminated when forming a multilayer reflective film. By forming a lower layer (smaller layer), and then forming an upper layer having a laminated film in which low refractive index layers and high refractive index layers that contribute to high reflectance and have improved crystallinity are alternately laminated. The present invention has been made by finding that a multilayer reflective film having a high reflectance to exposure light and a good surface smoothness can be obtained. Specifically, the lower layer is made of boron, carbon, zirconium, nitrogen, and oxygen in order to form a laminated film in which low refractive index layers having amorphous or finely divided crystal grains and high refractive index layers are alternately laminated. The material contains at least one additive element of choice. Further, in order to form the upper layer as a laminated film in which low refractive index layers and high refractive index layers having improved crystallinity are alternately laminated, the low refractive index and high refractive index substantially not containing the above-mentioned additive elements. It is used as a material for. By having a multilayer reflective film with good surface smoothness, the background level during defect inspection is lowered, so the time required for defect inspection of a substrate with a multilayer reflective film having a multilayer reflective film should be shortened. Can be done.

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, which comprises a multilayer film in which low refractive index layers and high refractive index layers are alternately laminated on a substrate, and which includes a multilayer reflective film for reflecting exposure light. There,
The multilayer reflective film includes an upper layer and a lower layer arranged between the upper layer and the substrate.
The underlayer contains at least one additive element selected from boron (B), carbon (C), zirconium (Zr), nitrogen (N), oxygen (O) and hydrogen (H).
The upper layer is a substrate with a multilayer reflective film, characterized in that it does not substantially contain the additive element.

The lower layer having a laminated film in which low refractive index layers and high refractive index layers are alternately laminated contains a predetermined additive element, so that the crystal grains of the lower layer can be made finer or amorphous. In the substrate with a multilayer reflective film according to the configuration 1 of the present invention, noise during defect inspection of the multilayer reflective film caused by coarsening of the crystal grains due to having a lower layer in which the crystal grains are refined or amorphized is generated. It is possible to suppress the problem that the increase, the time required for defect inspection, and the actual defect contributing to transcription are not detected. Further, in the substrate with the multilayer reflective film of the configuration 1 of the present invention, an upper layer which is a laminated film using materials (low refractive index layer and high refractive index layer) substantially containing no additive element is formed on the lower layer. By doing so, it is possible to obtain a multilayer reflective film having a high reflectance to the exposure light.

(Structure 2)
Configuration 2 of the present invention comprises that the low index layer comprises at least one selected from molybdenum (Mo), ruthenium (Ru), niobium (Nb), rhodium (Rh), and platinum (Pt). It is a substrate with a multilayer reflective film of configuration 1, which is a feature.

According to the configuration 2 of the present invention, a multilayer reflective film having a relatively high reflectance can be obtained by forming a low refractive index layer of the multilayer film using a predetermined material.

(Structure 3)
Configuration 3 of the present invention is a substrate with a multilayer reflective film of configuration 1 or 2, wherein the high-refractive index layer contains silicon (Si).

According to the configuration 3 of the present invention, a multilayer reflective film having a relatively high reflectance can be obtained by forming a high refractive index layer of the multilayer film using a predetermined material.

(Structure 4)
The configuration 4 of the present invention is characterized in that the content of the additive element in the low refractive index layer of the lower layer is higher than the content of the additive element in the high refractive index layer of the lower layer. A substrate with a multilayer reflective film according to any one of 3 to 3.

In order to obtain a multilayer reflective film having a high reflectance, it is more effective to add the additive element to the low refractive index layer. Therefore, according to the configuration 4 of the present invention, a multilayer reflective film having a higher reflectance can be obtained.

(Structure 5)
The configuration 5 of the present invention is a substrate with a multilayer reflective film according to any one of configurations 1 to 4, wherein the high refractive index layer of the lower layer does not substantially contain the additive element.

In order to obtain a multilayer reflective film having a high reflectance, it is effective to add the additive element only to the low refractive index layer, not to the high refractive index layer. Therefore, according to the configuration 5 of the present invention, a multilayer reflective film having a higher reflectance can be obtained.

(Structure 6)
In the configuration 6 of the present invention, the content of the additive element in the low refractive index layer of the lower layer is paired so that the reflectance of the multilayer reflective film with respect to EUV light having a wavelength of 13.5 nm is 67% or more. The multilayer of any of the configurations 1 to 5, characterized in that the period of the multilayer reflective film and the period of the lower layer are adjusted when the low refractive index layer and the high refractive index layer are set as one cycle. It is a substrate with a reflective film.

According to the configuration 6 of the present invention, a predetermined reflectance can be obtained by appropriately adjusting the content of the additive element in the lower low refractive index layer, the period of the entire multilayer reflective film, and the period of the lower layer reflective film. A multilayer reflective film having a content of 67% or more can be obtained.

(Structure 7)
The configuration 7 of the present invention is characterized in that the multilayer reflective film includes a laminated film having 30 to 60 cycles with the pair of the low refractive index layer and the high refractive index layer as one cycle. It is a substrate with a multilayer reflective film according to any one of 6.

According to the configuration 7 of the present invention, the multilayer reflective film is provided with a laminated film having 30 to 60 cycles (pair) when a pair of low refractive index layer and high refractive index layer is one cycle (pair). Therefore, a multilayer reflective film having a relatively high reflectance can be obtained in a relatively short time.

(Structure 8)
The configuration 8 of the present invention is characterized in that the lower layer includes a laminated film having 3 to 20 cycles with the pair of the low refractive index layer and the high refractive index layer as one cycle. It is a substrate with any of the multilayer reflective films.

According to the configuration 8 of the present invention, the lower layer is provided with a laminated film having 3 to 20 cycles (pairs) with a pair of low-refractive-index layers and high-refractive-index layers as one cycle (pair) with respect to exposure light. It is possible to more reliably obtain a multilayer reflective film having a high reflectance and a low background level during defect inspection.

(Structure 10)
The configuration 9 of the present invention is a substrate with a multilayer reflective film according to any one of configurations 1 to 8, characterized in that a protective film is provided on the multilayer reflective film.

According to the configuration 9 of the present invention, since the protective film is formed on the multilayer reflective film, it is applied to the surface of the multilayer reflective film when manufacturing a reflective mask (EUV mask) using the substrate with the multilayer reflective film. Since damage can be suppressed, the reflectance characteristic of the reflective mask to EUV light becomes good.

(Structure 10)
The configuration 10 of the present invention has an absorber film on the multilayer reflective film of the substrate with the multilayer reflective film of any one of configurations 1 to 8 or on the protective film of the substrate with the multilayer reflective film of the configuration 9. It is a reflective mask blank characterized by this.

By using the reflective mask blank of the configuration 10 of the present invention, it is possible to manufacture a reflective mask having a multilayer reflective film having a high reflectance to exposure light and a low background level at the time of defect inspection.

(Structure 11)
The configuration 11 of the present invention is a reflective mask characterized by having an absorber pattern in which the absorber film of the reflective mask blank of the configuration 10 is patterned on the multilayer reflective film.

According to the configuration 11 of the present invention, it is possible to obtain a reflective mask having a multilayer reflective film having a high reflectance to exposure light and a low background level at the time of defect inspection. Further, it is possible to obtain a reflective mask having no actual defects contributing to transfer on the multilayer reflective film.

(Structure 12)
The configuration 12 of the present invention is a method for manufacturing a semiconductor device, which comprises a step of performing a lithography process using an exposure apparatus using the reflective mask of the configuration 11 to form a transfer pattern on a transfer target. is there.

According to the method for manufacturing a semiconductor device according to the configuration 12 of the present invention, a reflective mask having a multilayer reflective film having a high reflectance to exposure light and a low background level at the time of defect inspection is used for manufacturing the semiconductor device. Can be used for. As a result, the throughput in the manufacture of the semiconductor device can be improved. Furthermore, when inspecting defects on a substrate with a multilayer reflective film, a semiconductor device is manufactured using a reflective mask that has no actual defects that contribute to transfer due to its low background level. It is possible to suppress a decrease in the yield of the semiconductor device due to a defect in the reflective film.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a reflective mask blank and a reflective mask having a multilayer reflective film having a high reflectance to exposure light and a low background level at the time of defect inspection. Further, according to the present invention, a substrate with a multilayer reflective film used for manufacturing a reflective mask blank and a reflective mask having a multilayer reflective film having a high reflectance to exposure light and a low background level at the time of defect inspection. Can be provided. Further, according to the present invention, it is possible to provide a method for manufacturing a semiconductor device using the above-mentioned reflective mask.

Further, according to the present invention, it is possible to provide a substrate with a multilayer reflective film, a reflective mask blank, and a reflective mask that can reliably detect actual defects that contribute to transfer.

It is sectional drawing of an example of the substrate with a multilayer reflective film of this invention. It is sectional drawing of another example of the substrate with a multilayer reflective film of this invention. It is sectional drawing of an example of the reflective mask blank of this invention. It is a process drawing which showed the manufacturing method of the reflective mask of this invention 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 shows a schematic cross-sectional view of an example of the substrate 110 with a multilayer reflective film according to the embodiment of the present invention. As shown in FIG. 1, the substrate 110 with a multilayer reflective film of the present embodiment is provided with the multilayer reflective film 5 on the substrate 1. The multilayer reflective film 5 is a film for reflecting exposure light, and is composed of a multilayer film in which low refractive index layers and high refractive index layers are alternately laminated. The multilayer reflective film 5 of the substrate 110 with a multilayer reflective film of the present embodiment includes an upper layer 54 and a lower layer 52 arranged between the upper layer 54 and the substrate 1. Details of the upper layer 54 and the lower layer 52 will be described later. The substrate 110 with a multilayer reflective film of the present embodiment may include the back surface conductive film 2 on the back surface of the substrate 1 (the main surface opposite to the main surface on which the multilayer reflective film 5 is formed).

FIG. 2 shows a schematic cross-sectional view of another example of the substrate 110 with a multilayer reflective film of the present embodiment. In the example shown in FIG. 2, the substrate 110 with a multilayer reflective film includes a protective film 6.

The reflective mask blank 100 can be manufactured by using the substrate 110 with the multilayer reflective film of the present embodiment. FIG. 3 shows a schematic cross-sectional view of an example of the reflective mask blank 100. The reflective mask blank 100 further includes an absorber film 7.

Specifically, the reflective mask blank 100 of the present embodiment has an absorber film 7 on the outermost surface (for example, the surface of the multilayer reflective film 5 or the protective film 6) of the substrate 110 with a multilayer reflective film. By using the reflective mask blank 100 of the present embodiment, it is possible to obtain a reflective mask 200 having a multilayer reflective film 5 having a high reflectance to EUV light.

In the present specification, the “board 110 with a multilayer reflective film” refers to a substrate in which a multilayer reflective film 5 is formed on a predetermined substrate 1. 1 and 2 show an example of a schematic cross-sectional view of the substrate 110 with a multilayer reflective film. The "board 110 with a multilayer reflective film" includes a thin film other than the multilayer reflective film 5, such as a protective film 6 and / or a back surface conductive film 2. In the present specification, the “reflective mask blank 100” refers to a substrate 110 with a multilayer reflective film in which an absorber film 7 is formed. The "reflective mask blank 100" includes a thin film other than the absorber film 7 (for example, an etching mask film and a resist film 8) further formed.

In the present specification, "arranging (forming) the absorber film 7 on the multilayer reflective film 5 (on the multilayer reflecting film 5)" means that the absorber film 7 is arranged in contact with the surface of the multilayer reflecting film 5. In addition to the case where it means that it is (formed), it also includes the case where it means that another film is provided between the multilayer reflective film 5 and the absorber film 7. The same applies to other membranes. 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.

<Substrate 110 with multilayer reflective film>
Hereinafter, the substrate 1 and each thin film constituting the substrate 110 with the multilayer reflective film of the present embodiment 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 absorber pattern 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 on the side on which the transfer pattern of the substrate 1 (the absorber film 7 described later constitutes this) is formed to have a predetermined flatness at least from the viewpoint of obtaining pattern transfer accuracy and position accuracy. The surface is processed. In the case of EUV exposure, the flatness is preferably 0.1 μm or less, more preferably 0.05 μm or less, still more preferably 0.05 μm or less in the region of 132 mm × 132 mm on the main surface on the side where the transfer pattern of the substrate 1 is formed. It is 0.03 μm or less. The second main surface (back surface) on the side 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 142 mm × 142 mm.

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 transfer absorber pattern 7a is formed is preferably 0.15 nm or less in root mean square roughness (Rms), 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 and 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. The base film can be a functional film having a function according to the purpose. For example, a conductive layer for preventing charge-up during mask pattern defect inspection by an electron beam, a flattening layer for improving the flatness of the surface of the substrate 1, and a smoothing layer for improving the smoothness of the surface of the substrate 1 are formed. can do.

As the material of the base film having the above-mentioned conductive function, 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 in Ru or Ta, titanium (Ti), niobium (Nb), molybdenum (Mo), zirconium (Zr), yttrium (Y), boron (B), lantern ( It may be a Ru alloy or a Ta alloy containing at least one metal selected from La), cobalt (Co) and renium (Re). The film thickness of the base film is preferably in the range of, for example, 1 nm to 10 nm.

Further, as the material of the base film for improving the flatness and the smoothness, silicon or a material containing silicon as a main component is preferably used. The material of the base film may be, for example, silicon (Si) alone, or SiO ₂ , SiO _x (x <2), SiON, Si ₃ N ₄ , Si containing Si containing oxygen (O) and nitrogen (N). It may be a silicon compound of _x N _y (natural number other than x: 3 and y: 4). Similar to the above, the film thickness of the base layer is preferably in the range of, for example, 1 nm to 10 nm.

<< 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. The multilayer reflective film 5 of the present embodiment includes an upper layer 54 and a lower layer 52 arranged between the upper layer 54 and the substrate 1.

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

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, the case where 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 as one cycle (pair) is the most. The upper layer is 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 is reduced. 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 laminated in a plurality of cycles as one cycle (pair). The uppermost 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 material containing silicon (Si) can be used. As a material containing Si, in addition to Si alone, Si is at least selected from boron (B), carbon (C), zirconium (Zr), nitrogen (N), oxygen (O) and hydrogen (H). A Si compound containing one element can be used. 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. In the substrate 110 with a multilayer reflective film of the present embodiment, it is preferable that the low refractive index layer is a layer containing molybdenum (Mo) and the high refractive index layer is a layer containing silicon (Si). 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 layers containing Mo and layers containing Si 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 (the uppermost layer of the upper layer 54), is formed of a layer containing silicon (Si) (for example, a silicon (Si) layer), and the uppermost layer (a layer containing Si). A silicon oxide layer containing silicon and oxygen can be formed between the protective film 6 and the protective film 6. In the case of this structure, the mask cleaning resistance can be improved.

As shown in FIG. 1, the multilayer reflective film 5 of the present embodiment includes an upper layer 54 and a lower layer 52. The lower layer 52 is arranged between the upper layer 54 and the substrate 1. Both the upper layer 54 and the lower layer 52 include a laminated film in which the above-mentioned high refractive index layer and low refractive index layer are alternately laminated. As the material of the high refractive index layer and the low refractive index layer of the upper layer 54 and the lower layer 52, basically, the above-mentioned materials (for example, Si as the high refractive index layer and Mo as the low refractive index layer) are used as the main materials. Can be done. That is, the main materials of the high refractive index layer and the low refractive index layer of the upper layer 54 and the main materials of the high refractive index layer and the low refractive index layer of the lower layer 52 can be the same.

The lower layer 52 of the multilayer reflective film 5 of the present embodiment is made of boron (B), carbon (C), zirconium (Zr), nitrogen (N), oxygen (O) and hydrogen (H) in addition to the above-mentioned main materials. Contains at least one additive element of choice. Specifically, at least one of the material of the high refractive index layer and the material of the low refractive index layer of the lower layer 52 contains the above-mentioned additive element. When the material of the lower layer 52 contains a predetermined additive element in addition to the above-mentioned main material, the crystal grains of the lower layer 52 can be made finer or amorphous. The presence of the additive element contained in the lower layer 52 can be confirmed by XPS (X-ray photoelectron spectroscopy), RBS (Rutherford backscatter analysis), TEM-EDX (energy dispersive X-ray spectroscopy), or the like. ..

The upper layer 54 of the multilayer reflective film 5 of the present embodiment substantially contains no additive element. That is, the upper layer 54 of the present embodiment has a high refractive index layer and a low refractive index layer made of the same material as the conventional multilayer reflective film 5. Therefore, the upper layer 54 is a laminated film having a high reflectance with respect to the exposure light. In addition, "the upper layer 54 does not substantially contain the additive element" means that the additive element is not intentionally blended with the upper layer 54, and an element of the same type as the additive element is inevitably present as an impurity. It does not exclude the case of doing.

Since the crystal grains of the lower layer 52 containing the above additive elements are refined or amorphized, the smoothness of the surface of the multilayer reflective film 5 is improved, while the reflectance of the laminated film of the lower layer 52 is high. It will be lower than the laminated film using the conventional material. By forming an upper layer 54 having a high crystallinity on the lower layer 52, which does not substantially contain the additive element and has improved crystallinity, the reflectance of the lower layer 52 is lowered due to the addition of the additive element to the lower layer 52. Can be suppressed to the extent that there is no effect. Specifically, the reflectance of the multilayer reflective film 5 can be set to 67% or more. Therefore, the multilayer reflective film 5 of the present embodiment includes the predetermined upper layer 54 and the lower layer 52, so that the multilayer reflective film 5 has a high reflectance to the exposure light and a good surface smoothness.

In the substrate 110 with a multilayer reflective film of the present embodiment, the low refractive index layer of the multilayer reflective film 5 is selected from molybdenum (Mo), ruthenium (Ru), niobium (Nb), rhodium (Rh), and platinum (Pt). It is preferable to include at least one of the above. Since these materials have a refractive index of 0.94 or less in EUV light having a wavelength of 13.5 nm, the main material of the low refractive index layer of the multilayer reflective film 5 is relatively these predetermined materials. A multilayer reflective film 5 having a high refractive index can be obtained.

In the substrate 110 with a multilayer reflective film of the present embodiment, it is preferable that the high refractive index layer of the multilayer reflective film 5 contains silicon (Si). Since the main material of the high refractive index layer of the multilayer reflective film 5 is silicon (Si), the multilayer reflective film 5 having a relatively high reflectance can be obtained.

In the substrate 110 with the multilayer reflective film of the present embodiment, the content of the additive element in the low refractive index layer of the lower layer 52 of the multilayer reflective film 5 is higher than the content of the additive element in the high refractive index layer of the lower layer 52. preferable. Further, it is preferable that the high refractive index layer of the lower layer 52 of the multilayer reflective film 5 substantially does not contain additive elements.

In order to obtain the multilayer reflective film 5 having a high reflectance, it is effective to add the additive element to the low refractive index layer. Further, when silicon (Si) is the main material of the high refractive index layer, when an additive element is added to the high refractive index layer, the refractive index in EUV light having a wavelength of 13.5 nm decreases, so that the multilayer reflective film 5 Refractive index may decrease. Therefore, it is preferable that the additive element is added to the lower layer 52 mainly to the low refractive index layer of the lower layer 52. As a result, the decrease in the reflectance of the lower layer 52 can be suppressed, so that the multilayer reflective film 5 having a higher reflectance can be obtained.

In the substrate 110 with a multilayer reflective film of the present embodiment, the main materials of both the lower layer 52 and the upper layer 54 of the multilayer reflective film 5 are silicon (Si) in the high refractive index layer and molybdenum (Mo) in the low refractive index layer. Is preferable. In this case, the additive element contained in the lower layer 52 is preferably at least one selected from boron (B), carbon (C) and nitrogen (N). Further, it is more preferable that the additive element is contained only in the low refractive index layer of the lower layer 52.

In the substrate 110 with a multilayer reflective film of the present embodiment, the content of additive elements in the low refractive index layer of the lower layer 52 is set so that the multilayer reflective film 5 has a reflectance of 67% or more with respect to EUV light having a wavelength of 13.5 nm. When a pair of low refractive index layer and high refractive index layer is regarded as one cycle (pair), it is preferable that the number of cycles (number of pairs) and the number of cycles (number of pairs) of the lower layer 52 are adjusted. As the reflective mask 200 for manufacturing a semiconductor device, the reflectance of the multilayer reflective film 5 to EUV light having a wavelength of 13.5 nm needs to be 67% or more. The multilayer reflective film 5 of the present embodiment appropriately adjusts the content of the additive element in the low refractive index layer of the lower layer 52, the period of the entire multilayer reflective film 5, and the period of the layer reflective film of the lower layer 52. A reflectance of% or more can be obtained.

In the substrate 110 with the multilayer reflective film of the present embodiment, the content of the additive element in the low refractive index layer of the lower layer 52 of the multilayer reflective film 5 is preferably 0.5 atomic% or more and 20 atomic% or less. More preferably, it is 5 atomic% or more and 10 atomic% or less. If the content of the additive element in the lower layer 52 is too low, it becomes difficult to refine or amorphize the crystal grains in the lower layer 52. Further, if the content of the additive element in the lower layer 52 is too high, the reflectance of the multilayer reflective film 5 to EUV light having a wavelength of 13.5 nm may be unacceptably lowered. Therefore, the content of the additive element in the low refractive index layer of the lower layer 52 is preferably in the above-mentioned predetermined range. By setting the content of the additive element in the low refractive index layer of the lower layer 52 within a predetermined range, the multilayer reflective film 5 having a high reflectance to the exposure light and a low background level at the time of defect inspection can be obtained more reliably. be able to.

In the substrate 110 with a multilayer reflective film of the present embodiment, the multilayer reflective film 5 includes a pair of low refractive index layers and a high refractive index layer as one cycle (pair) of 30 to 60 cycles (pair). It is preferable to have 35 to 55 cycles (pairs), and even more preferably 35 to 45 cycles (pairs). As the number of cycles (number of pairs) increases, higher reflectance can be obtained, but the formation time of the multilayer reflective film 5 becomes longer. By setting the period of the multilayer reflective film 5 to an appropriate range, the multilayer reflective film 5 having a relatively high reflectance can be obtained in a relatively short time.

In the substrate 110 with the multilayer reflective film of the present embodiment, the lower layer 52 of the multilayer reflective film 5 has 3 cycles (pair) or more and 20 cycles (pair) with a pair of low refractive index layer and high refractive index layer as one cycle (pair). It is preferably 3 cycles (pair) or more and less than 20 cycles (pair), more preferably 3 cycles (pair) or more and 15 cycles (pair). Since the lower layer 52 contains the above-mentioned additive element, the reflectance is lower than that of the upper layer 54 having high crystallinity. Therefore, if the number of cycles (number of pairs) of the low refractive index layer and the high refractive index layer constituting the lower layer 52 is too large, the reflectance of the multilayer reflective film 5 may decrease. On the other hand, if the number of cycles (number of pairs) of the low refractive index layer and the high refractive index layer constituting the lower layer 52 is too small, the effect of refining or amorphizing the crystal grains of the lower layer 52 is weakened. By setting the number of cycles (number of pairs) of the low-refractive index layer and the high-refractive index layer constituting the lower layer 52 to an appropriate range, the multi-layer having high reflectance to exposure light and low background level at the time of defect inspection. The reflective film 5 can be obtained more reliably.

By using the substrate 110 with the multilayer reflective film of the present embodiment, the reflective mask blank 100 and the reflective mask 200 having the multilayer reflective film 5 having a high reflectance to the exposure light and a low background level at the time of defect inspection are used. Can be manufactured. Since the background level at the time of defect inspection is low, defect inspection can be performed in a relatively short time, and actual defects that contribute to transcription can be reliably detected.

The reflectance of the multilayer reflective film 5 of the present embodiment to EUV light alone is usually preferably 67% or more. When the reflectance is 67% or more, it can be preferably used as a reflective mask 200 for manufacturing a semiconductor device. The upper limit of the reflectance is usually preferably 73%. The film thickness and the number of cycles (number of pairs) of the low refractive index layer and the high refractive index layer constituting the multilayer reflective film 5 can be appropriately selected depending on the exposure wavelength. Specifically, the film thickness and the number of cycles (number of pairs) of the low refractive index layer and the high refractive index layer constituting 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 outermost surface (for example, the Si layer) of the multilayer reflective film 5 can be adjusted within a range that does not reduce the reflectance. The film thickness of the outermost surface high refractive index layer (for example, Si layer) can be 3 nm to 10 nm.

The substrate 110 with a multilayer reflective film of the present embodiment preferably has a background level (BGL) of less than 400 when the surface of the multilayer reflective film 5 is inspected for defects by a defect inspection device. The background level (BGL) at the time of defect inspection is, for example, when the surface of the multilayer reflective film 5 is inspected for defects by an Actinic Blank Inspection using EUV light as the inspection light. It means the background value observed as noise. In the case of a blanks defect inspection device using EUV light, the background level (BGL) is automatically measured from the measurement signal.

<< Protective film 6 >>
In the substrate 110 with a multilayer reflective film of the present embodiment, it is preferable to form the protective film 6 on the multilayer reflective film 5 as shown in FIG. Since the protective film 6 is formed 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 is formed on the multilayer reflective film 5 in order to protect the multilayer reflective film 5 from dry etching and washing in the manufacturing process of the reflective mask 200 described later. The protective film 6 also has a function of protecting the multilayer reflective film 5 when correcting black defects in a mask pattern using an electron beam (EB). Here, FIG. 2 shows a case where the protective film 6 has one layer. However, the protective film 6 may have a laminated structure of two layers, or the protective film 6 may have a laminated structure of three or more layers, and the lowermost layer and the uppermost layer may be a layer made of a substance containing, for example, Ru, and the lowermost layer. A metal or alloy other than Ru may be interposed between the top layer and the top layer. The protective film 6 is formed of, for example, a material containing ruthenium as a main component. Materials containing ruthenium as the main component include ru metal alone, Ru with titanium (Ti), niobium (Nb), molybdenum (Mo), zirconium (Zr), yttrium (Y), boron (B), and lantern (La). , Ru alloys containing at least one metal selected from cobalt (Co) and ruthenium (Re), and materials containing nitrogen in them. Among these, it is particularly preferable to use the protective film 6 made of a Ru-based material containing Ti. When the constituent element of the multilayer reflective film 5 is silicon, the phenomenon that silicon diffuses from the surface of the multilayer reflective film 5 to the protective film 6 by using the protective film 6 made of a Ru-based material containing Ti. Can be suppressed. Therefore, the surface roughness during mask cleaning is reduced, and the film is less likely to peel off. Since the reduction of surface roughness is directly linked to the prevention of the decrease in the reflectance of the multilayer reflective film 5 with respect to the EUV exposure light, it is important for improving the exposure efficiency and throughput of EUV exposure.

The Ru content ratio of the Ru alloy used for the protective film 6 is 50 atomic% or more and less than 100 atomic%, preferably 80 atomic% or more and less than 100 atomic%, and more preferably 95 atomic% or more and less than 100 atomic%. In particular, when the Ru content ratio of the Ru alloy is 95 atomic% or more and less than 100 atomic%, it is possible to suppress the diffusion of the constituent elements (for example, silicon) of the multilayer reflective film 5 with respect to the protective film 6. Further, the protective film 6 in this case provides mask cleaning resistance, an etching stopper function when the absorber film 7 is etched, and prevents the multilayer reflective film 5 from changing over time while sufficiently ensuring the reflectance of EUV light. It is possible to combine functions.

In EUV lithography, since there are few substances that are transparent to the exposure light, EUV pellicle that prevents foreign matter from adhering to the mask pattern surface is not technically easy. For this reason, pellicle-less operation that does not use pellicle has become the mainstream. Further, in EUV lithography, exposure contamination occurs such that a carbon film is deposited on the reflective mask 200 and an oxide film is grown due to EUV exposure. Therefore, when the reflective mask 200 is used in the manufacture of a semiconductor device, it is necessary to frequently perform cleaning to remove foreign matter and contamination on the reflective mask 200. For this reason, the EUV reflective mask 200 is required to have an order of magnitude higher mask cleaning resistance than the transmissive mask for photolithography. When the protective film 6 made of a Ru-based material containing Ti is used, a cleaning liquid such as sulfuric acid, sulfuric acid hydrogen peroxide (SPM), ammonia, ammonia hydrogen peroxide (APM), OH radical cleaning water, and ozone water having a concentration of 10 ppm or less is used. The cleaning resistance to hydrogen peroxide is particularly high, and it becomes possible to meet the requirement for mask cleaning resistance.

The film thickness of the protective film 6 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, more preferably 1.5 nm to 6.0 nm.

As a method for forming the protective film 6, a known film forming method can be adopted without particular limitation. Specific examples include a sputtering method and an ion beam sputtering method as a method for forming the protective film 6.

<Reflective mask blank 100>
An embodiment of the reflective mask blank 100 of the present embodiment will be described. By using the reflective mask blank 100 of the present embodiment, it is possible to manufacture a reflective mask 200 having a multilayer reflective film 5 having a high reflectance to exposure light and a low background level at the time of defect inspection.

<< Absorbent Membrane 7 >>
The reflective mask blank 100 has an absorber film 7 on the substrate 110 with the multilayer reflective film described above. That is, the absorber film 7 is formed on the multilayer reflective film 5 (when 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 is one that absorbs EUV light and reflects a part of it 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 reflecting 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 film 7 may be a single-layer film or a multilayer film composed of a plurality of films. In the case of a single-layer film, the number of processes 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 inspection using light. As a result, the inspection sensitivity at the time of mask pattern inspection using light is improved. 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. In the case of the absorber film 7 having a phase shift function, the range of adjustment on the optical surface can be increased by forming the absorber film 7, so that a desired reflectance can be easily obtained. Become.

As long as 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) or fluorine (F) gas). There is no particular limitation. As a substance having such a function, tantalum (Ta) alone or a tantalum compound containing Ta as a main component can be preferably used.

The above-mentioned absorber film 7 such as tantalum and tantalum compound 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 can be formed 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 contains an alloy of Ta. 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.

In addition to tantalum or tantalum compounds, the materials constituting the absorber film 7 include chromium and chromium compounds such as Cr, CrN, CrCON, CrCO, CrCOH, and CrCONH, and materials such as WN, TiN, and Ti. Can be mentioned.

<< Backside conductive film 2 >>
Above the second main surface (back surface) of the substrate 1 (on the opposite side of the forming surface of the multilayer reflective film 5 and above the intermediate layer when an intermediate layer such as a hydrogen intrusion suppression film is formed on the substrate 1) The back surface conductive film 2 for the electrostatic chuck is formed on the surface. The sheet resistance required for the back surface conductive film 2 for the electrostatic chuck is usually 100 Ω / □ 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 the back surface conductive film 2 chromium (Cr) 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. Is preferable. Examples of the Ta compound 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 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. In that case, a substrate 110 with a multilayer reflective film having a back surface conductive film 2 as shown in FIG. 2 can be obtained.

<Other thin films>
The substrate 110 with a multilayer reflective film and the reflective mask blank 100 manufactured by the manufacturing method of the present embodiment have a hard mask film for etching (also referred to as “etching mask film”) and / or a resist film on the absorber film 7. 8 can be provided. As a typical material of the hard mask film for etching, silicon (Si) and at least one element selected from oxygen (O), nitrogen (N), carbon (C) and hydrogen (H) are added to silicon. There are materials such as silicon (Cr), and materials obtained by adding at least one element selected from oxygen (O), nitrogen (N), carbon (C), and hydrogen (H) to silicon. Specific examples thereof include SiO ₂ , SiON, SiN, SiO, Si, SiC, SiCO, SiCN, SiCON, Cr, CrN, CrO, CrON, CrC, CrCO, CrCN, CrOCN and the like. However, when the absorber film 7 is a compound containing oxygen, it is better to avoid a material containing oxygen (for example, SiO ₂ ) as a hard mask film for etching from the viewpoint of etching resistance. When a hard mask film for etching is formed, the film thickness of the resist film 8 can be reduced, which is advantageous for miniaturization of the pattern.

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>
An embodiment of the present invention is a reflective mask 200 in which the absorber film 7 of 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 multilayer reflective film 5 having a high reflectance to exposure light and a low background level at the time of defect inspection.

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

A reflective mask blank 100 is prepared, and a resist film 8 is formed on the outermost surface of the first main surface thereof (on the absorber film 7 as described in the following examples) (reflective mask blank 100). This is not necessary when the resist film 8 is provided), and a desired pattern such as a circuit pattern is drawn (exposed) on the resist film 8 and further developed and rinsed to form a predetermined resist pattern 8a.

The absorber pattern 7a is formed by dry etching the absorber film 7 using this resist pattern 8a as a mask. The etching gas 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-based gas and He in a predetermined ratio. Mixed gas containing, mixed gas containing chlorine-based gas and Ar in a predetermined ratio, CF ₄ , CHF ₃ , C ₂ F ₆ , C ₃ F ₆ , C ₄ F ₆ , C ₄ F ₈ , CH ₂ F ₂ , A gas selected from a fluorine-based gas such as CH ₃ F, C ₃ F ₈ , SF ₆ , F ₂ and a mixed gas containing a fluorine-based gas and O ₂ in a predetermined ratio 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, it is preferable to use an etching gas containing no oxygen at the over-etching step in which the Ru-based protective film 6 is exposed to etching.

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.

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

<Manufacturing method of semiconductor devices>

The method for manufacturing a semiconductor device according to the embodiment of the present invention includes 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.

In the present embodiment, a reflective mask 200 having a multilayer reflective film 5 having a high reflectance to exposure light and a low background level at the time of defect inspection can be used for manufacturing a semiconductor device. As a result, the throughput in the manufacture of the semiconductor device can be improved. Further, since the semiconductor device is manufactured by using the reflective mask 200 having no actual defect contributing to transfer on the multilayer reflective film 5, it is possible to suppress the decrease in the yield of the semiconductor device due to the defect of the multilayer reflective film 5. it can.

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 processes such as etching of the film to be processed, formation of insulating film, conductive film, introduction of 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, each embodiment will be described with reference to the drawings.

(Experiment 1, Experiment 2, Experiment 3-1 and Experiment 4-1)
As Experiment 1, Experiment 2, Experiment 3-1 and Experiment 4-1 as shown in FIG. 1, a substrate 110 with a multilayer reflective film was produced in which a multilayer reflective film 5 was formed on one main surface of the substrate 1. The substrate 110 with the multilayer reflective film of Experiment 1, Experiment 2, Experiment 3-1 and Experiment 4-1 was prepared as follows.

((Board 1))
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.

((Multilayer reflective film 5 in Experiment 1))
In Experiment 1, a multilayer reflective film 5 having a lower layer 52 and an upper layer 54 was formed on the first main surface of the above-mentioned substrate 1 by using a DC sputtering apparatus. The multilayer reflective film 5 has a high refractive index layer of Si as a main material and a low refractive index layer of Mo as a main material in order to obtain a multilayer reflective film 5 suitable for EUV light having a wavelength of 13.5 nm. When the refractive index layer and the low refractive index layer are set to one cycle (pair), the multilayer reflective film 5 is provided with a total cycle number (number of pairs) of 40 cycles (pairs) including the lower layer 52 and the upper layer 54. The multilayer reflective film 52 is formed by alternately laminating high refractive index layers and low refractive index layers in contact with the substrate 1 by a DC sputtering method in a predetermined gas atmosphere using a Mo target and a Si target. did. First, a high refractive index layer was formed with a thickness of 4.2 nm, and then a low refractive index layer was formed with a thickness of 2.8 nm. This is set as one cycle (pair), and similarly, the lower layer 52 and the upper layer 54 are combined and laminated for 40 cycles (pair), and finally, a Si film of a high refractive index layer is formed with a thickness of 4.0 nm. The multilayer reflective film 5 was formed.

Table 1 shows the gas and flow rate used for film formation of the lower layer 52 and the upper layer 54 of the multilayer reflective film 5 when manufacturing the substrate 110 with the multilayer reflective film of Experiment 1. In Experiment 1 (Experiment 1-1, Experiment 1-2 and Experiment 1-3) shown in Table 1, nitrogen (N) was used by using N ₂ gas in addition to Kr gas when forming the lower layer 52. ) Was introduced into the lower layer 52 as an additive element. When the upper layer 54 was formed, only Kr gas was introduced without using N ₂ gas.

As shown in Table 1, the multilayer reflective film 52 has a low refractive index layer and a high refractive index when the upper layer 54 and the lower layer 52 are combined to form one cycle (pair) of the low refractive index layer and the high refractive index layer. The layers were laminated for 40 cycles (pairs). The lower layer period number (upper layer period number) in Table 1 refers to the period number (number of pairs) when the low refractive index layer and the high refractive index layer constituting the lower layer (upper layer) are regarded as one cycle (pair). The same applies to Table 2, Table 3, and Table 4. The numerical value in parentheses in the predetermined column of Table 1 is the number of cycles (number of pairs) of the upper layer 54. For example, in the case of sample 1 of Experiment 1-1 shown in Table 1, the upper layer 54 has a low refractive index layer and the high refractive index layer as one cycle (pair), 40 cycles (pair), and the lower layer 52 is 0. It was set as a cycle (pair). In Samples 2 to 6 of Experiment 1-1, the number of pairs (periods) of the low refractive index layer and the high refractive index layer of the upper layer 54 to which nitrogen (N) was not added was reduced, and nitrogen (N) was added. The number of pairs (number of cycles) of the low refractive index layer and the high refractive index layer of the lower layer 52 was increased. In the case of Experiment 1-1, six types of substrates 110 with a multilayer reflective film of Samples 1 to 6 were manufactured.

((Multilayer reflective film 5 in Experiment 2))
In Experiment 2, similarly to Experiment 1, a multilayer reflective film 5 provided with a lower layer 52 and an upper layer 54 was formed on the first main surface of the above-mentioned substrate 1 by using a DC sputtering apparatus. The multilayer reflective film 5 has a high refractive index layer of Si as a main material and a low refractive index layer of Mo as a main material in order to obtain a multilayer reflective film 5 suitable for EUV light having a wavelength of 13.5 nm. When the refractive index layer and the low refractive index layer have one cycle (pair), the multilayer reflective film 5 has 40 cycles (pairs) of the lower layer 52 and the upper layer 54. The multilayer reflective film 52 was formed by alternately laminating high refractive index layers and low refractive index layers on the substrate 1 by a DC sputtering method in a predetermined gas atmosphere using a Mo target and a Si target. Similar to Experiment 1, the high refractive index layer was first formed with a thickness of 4.2 nm, and then the low refractive index layer was formed with a thickness of 2.8 nm. This is set as one cycle (pair), and similarly, the lower layer 52 and the upper layer 54 are combined and laminated for 40 cycles (pair), and finally, a Si film of a high refractive index layer is formed with a thickness of 4.0 nm. The multilayer reflective film 5 was formed.

Table 2 shows the gas and the flow rate used for forming the lower layer 52 and the upper layer 54 of the multilayer reflective film 5 when manufacturing the substrate 110 with the multilayer reflective film of Experiment 2. In Experiment 2 (Experiment 2-1 and Experiment 2-2), carbon (C) was introduced into the lower layer 52 as an additive element by using CH ₄ gas in addition to Kr gas when the lower layer 52 was formed. did.

As shown in Table 2, the multilayer reflective film 52 has a low refractive index layer and a high refractive index when the upper layer 54 and the lower layer 52 are combined to form a pair (period) of the low refractive index layer and the high refractive index layer. The layers were laminated for 40 cycles (pairs). Similar to Table 1, the numerical value in parentheses in the predetermined column of Table 2 is the number of cycles (number of pairs) of the upper layer 54.

((Multilayer reflective film 5 in Experiment 3-1))
In Experiment 3-1 a multilayer reflective film 5 having a lower layer 52 and an upper layer 54 was formed on the first main surface of the above-mentioned substrate 1 by using a DC sputtering apparatus. The multilayer reflective film 5 has a high refractive index layer of Si as a main material and a low refractive index layer of Mo as a main material in order to obtain a multilayer reflective film 5 suitable for EUV light having a wavelength of 13.5 nm. When the refractive index layer and the low refractive index layer have one cycle (number of pairs), the multilayer reflective film 5 has a total number of cycles (number of pairs) of 40 cycles (pairs) including the lower layer 52 and the upper layer 54. The lower layer 52 of the multilayer reflective film 5 uses a Si target and an alloy target of Mo and B, and is a Si layer (high) on the substrate 1 which does not contain the above-mentioned additive elements by a DC sputtering method in a predetermined gas atmosphere. The Mo layer (low refractive index layer) containing B as an additive element was alternately laminated and formed. The upper layer 54 of the multilayer reflective film 5 uses a Si target and a Mo target, and is a Si layer (high refractive index layer) containing the above additive elements on the substrate 1 by a DC sputtering method in a predetermined gas atmosphere. And Mo layers (low refractive index layers) not containing the above additive elements were alternately laminated to form. Similar to Experiment 1, the high refractive index layer (Si layer) was first formed with a thickness of 4.2 nm, and then the low refractive index layer was formed with a thickness of 2.8 nm. This is set as one cycle (pair), and similarly, the lower layer 52 and the upper layer 54 are combined and laminated for 40 cycles (pair), and finally, a Si film of a high refractive index layer is formed with a thickness of 4.0 nm. The multilayer reflective film 5 was formed.

Table 3 shows the gas and the flow rate used for film formation of the lower layer 52 and the upper layer 54 of the multilayer reflective film 5 when manufacturing the substrate 110 with the multilayer reflective film of Experiment 3-1. In Experiment 3-1 when the low refractive index layer of the lower layer 52 was formed, boron (B) was introduced into the lower layer 52 as an additive element by using an alloy target of Mo and B.

As shown in Table 3, the multilayer reflective film 52 has a low refractive index layer and a high refractive index when the upper layer 54 and the lower layer 52 are combined to form one cycle (pair) of the low refractive index layer and the high refractive index layer. The layers were laminated for 40 cycles (pairs). Similar to Table 1, the numerical value in parentheses in the predetermined column of Table 3 is the number of cycles (number of pairs) of the upper layer 54.

((Multilayer reflective film 5 in Experiment 4-1))
In Experiment 4, in experiments 1-2, the time of film formation of the low refractive index layer of the lower layer 52, in addition to the Kr gas, a N ₂ gas, during the deposition of the high refractive index layer of the lower layer 52, The substrate 110 with a multilayer reflective film was manufactured in the same manner as in Experiment 1-2 except that the lower layer 52 and the upper layer 54 were formed using only Kr gas without using N ₂ gas.

As described above, the substrate 110 with the multilayer reflective film of each sample of Experiment 1, Experiment 2, Experiment 3-1 and Experiment 4-1 was manufactured.

The reflectance of the multilayer reflective film 5 of the substrate 110 with the multilayer reflective film of each sample of Experiment 1, Experiment 2, Experiment 3-1 and Experiment 4-1 manufactured as described above to EUV light having a wavelength of 13.5 nm. Was measured. Tables 1 to 4 show the measurement results of reflectance.

Defect inspection was performed on the substrate 110 with the multilayer reflective film of each sample of Experiment 1, Experiment 2, Experiment 3-1 and Experiment 4-1 manufactured as described above, and the background level of the multilayer reflective film 5 ( BGL) was measured. The background level (BGL) is automatically measured when the defect inspection of the multilayer reflective film 5 is measured by a predetermined defect inspection apparatus. The background level (BGL) measurement results are shown in the “BGL” column of Tables 1 to 3. As a defect inspection apparatus for defect inspection of the substrate 110 with a multilayer reflective film, a blank defect inspection apparatus (Actinic Blank Inspection) using EUV light as inspection light was used.

Further, the flatness of the multilayer reflective film 5 of the substrate 110 with the multilayer reflective film of each sample of Experiment 1, Experiment 2, Experiment 3-1 and Experiment 4-1 was measured by using a flatness measuring device (UltraFlat200 manufactured by Tropel Co., Ltd.). The flatness was 350 nm.

(Evaluation result of Experiment 1)
In Experiment 1 (Experiment 1-1, Experiment 1-2 and Experiment 1-3) shown in Table 1, N ₂ gas is used in addition to Kr gas when forming the lower layer 52 of the multilayer reflective film 5. Introduced nitrogen (N) into the lower layer 52 as an additive element. On the other hand, in Experiment 1, only Kr gas was introduced when the upper layer 54 of the multilayer reflective film 5 was formed. The presence or absence of nitrogen (N), which is an additive element, in the lower layer 52 and the upper layer 54 was confirmed by TEM-EDX analysis. As a result, the lower layer 52 (the laminated film in which the low refractive index layer and the high refractive index layer were alternately laminated) contained nitrogen (N), but the upper layer 54 contained nitrogen (N). I confirmed that it was not. Further, in Experiment 1-1, Experiment 1-2, and Experiment 1-3, it was found that as the flow rate of the N ₂ gas during film formation increased, the nitrogen content of the additive element contained in the lower layer 52 increased. confirmed. As shown in Table 1, experiments 1-1, Experiment 1-2 and Experiment 1-3, the flow rate of _{N 2} gas at the time of film formation was 0.2 sccm, and 0.25sccm and 0.35sccm respectively. In the case of Sample 1 of Experiment 1-1, Experiment 1-2, and Experiment 1-3, a laminated film in which low refractive index layers and high refractive index layers containing nitrogen (N) as an additive element are alternately laminated is provided. The lower layer 52 was not formed. Therefore, the background level (BGL) of sample 1 was as high as 413. On the other hand, in the case of Samples 2 to 6 of Experiment 1-1, Samples 2 to 4 of Experiment 1-2 and Samples 2 to 3 of Experiment 1-3, low nitrogen (N) was contained as an additive element. The background level (BGL) was a low value of less than 400 because the lower layer 52 having a laminated film in which the refractive index layers and the high refractive index layers were alternately laminated was formed. Therefore, it can be said that the multilayer reflective film 5 having a lower background level at the time of defect inspection can be obtained by having the lower layer 52 containing nitrogen (N) as an additive element.

Experiments 1-1, the flow rate of _{N 2} gas during the formation of the lower layer 52 of the multilayer reflective film 5, and 0.2 sccm, was relatively low. In this case, when the low refractive index layer and the high refractive index layer are set as one cycle (pair), the multilayer reflective film 5 has a low refractive index layer and a high refractive index forming the lower layer 52 during 40 cycles (pair). When the number of cycles (number of pairs) when the layer was one cycle (pair) was 15 cycles (pairs) or less (samples 1 to 4), the reflectance to EUV light was 67% or more, which was a good value. That is, in Experiment 1-1, in order for the multilayer reflective film 5 to obtain good reflectance, the number of cycles (pairs) when the low refractive index layer and the high refractive index layer constituting the lower layer 52 are set as one cycle (pair). It can be said that the number of pairs) is preferably less than 20 cycles (pairs). Considering the above, in Experiment 1-1, in order to obtain a multilayer reflective film 5 having a low background level of less than 400 and a good reflectance of 67% or more, a low refractive index layer and a high refractive index layer constituting the lower layer 52 are obtained. It can be said that the number of cycles (number of pairs) when the rate layer is one cycle (pair) is preferably 3 cycles (pairs) or more and less than 20 cycles (pairs).

Experiment 1-2, the flow rate of _{N 2} gas during the formation of the lower layer 52 of the multilayer reflective film 5, and 0.25Sccm, was moderate values. In this case, when the low refractive index layer and the high refractive index layer are set as one cycle (pair), the multilayer reflective film 5 has a low refractive index layer and a high refractive index forming the lower layer 52 during 40 cycles (pair). When the number of cycles (number of pairs) when the layer was one cycle (pair) was 10 cycles (pairs) or less (samples 1 to 3), the reflectance to EUV light was 67% or more, which was a good value. That is, in Experiment 1-2, in order for the multilayer reflective film 5 to obtain good reflectance, the number of cycles (pairs) when the low refractive index layer and the high refractive index layer constituting the lower layer 52 are set as one cycle (pair). It can be said that the number of pairs) is preferably less than 15 cycles (pairs) (less than 15 cycles (pairs)). In the case of Experiment 1-2 in which the nitrogen content of the additive element was higher than that in Experiment 1-1, it is considered that the decrease in reflectance due to the lower layer 52 was larger. Considering the above, in Experiment 1-2, in order to obtain a multilayer reflective film 5 having a low background level of less than 400 and a good reflectance of 67% or more, a low refractive index layer and a high refractive index layer constituting the lower layer 52 are obtained. When the rate layer is one cycle (pair), the number of cycles (number of pairs) is preferably 3 cycles (pairs) or more and less than 15 cycles (pairs), and 3 cycles (pairs) or more and 10 cycles (pairs) or less. It can be said that it is preferable.

Experiments 1-3, the flow rate of _{N 2} gas during the formation of the lower layer 52 of the multilayer reflective film 5, and 0.35Sccm, was relatively high value. In this case, a multilayer reflective film 5 having a low background level of less than 400 and a reflectance of 67% or more for EUV light could not be obtained. It is considered that the decrease in reflectance due to the lower layer 52 was further increased in the case of Experiment 1-3 in which the content of the additive element was higher than in Experiment 1-1 and Experiment 1-2. When a large amount of nitrogen, which is an additive element, is contained as in Experiment 1-3, it can be said that the multilayer reflective film 5 having good reflectance cannot be obtained.

(Evaluation result of Experiment 2)
In Experiment 2 (Experiment 2-1 and Experiment 2-2) shown in Table 2, carbon (C) was formed by using CH ₄ gas in addition to Kr gas when forming the lower layer 52 of the multilayer reflective film 5. ) Was introduced into the lower layer 52 as an additive element. On the other hand, in Experiment 2, only Kr gas was introduced when the upper layer 54 of the multilayer reflective film 5 was formed. The presence or absence of carbon (C), which is an additive element, in the lower layer 52 and the upper layer 54 was confirmed by TEM-EDX analysis. As a result, the lower layer 52 (the laminated film in which the low refractive index layer and the high refractive index layer were alternately laminated) contained carbon (C), but the upper layer 54 contained carbon (C). I confirmed that it was not. Further, in Experiments 2-1 and 2-2, it was confirmed that as the flow rate of CH ₄ gas during film formation increased, the carbon content of the additive element contained in the lower layer 52 increased. As shown in Table 2, in Experiment 2-1 and Experiment 2-2, the flow rates of CH ₄ gas during film formation were 0.24 sccm and 1.2 sccm, respectively. In the case of Sample 1 of Experiment 2-1 and Experiment 2-2, a lower layer 52 having a laminated film in which low refractive index layers and high refractive index layers containing carbon (C) as an additive element were alternately laminated was formed. Did not film. Therefore, the background level (BGL) of sample 1 was as high as 413. In addition, the background level (BGL) of Sample 2 of Experiment 2-1 was as high as 410. On the other hand, in the cases of Samples 3 to 6 of Experiment 2-1 and Samples 2 to 6 of Experiment 2-2, the background level (BGL) was as low as less than 400. In the case of Experiment 2-1 when the low refractive index layer and the high refractive index layer containing carbon (C) as an additive element are set to one cycle (pair), the lower layer 52 having at least three cycles (pair) and the lower layer 52 and In the case of Experiment 2-2, it can be said that the multilayer reflective film 5 having a low background level at the time of defect inspection can be obtained by having the lower layer 52 having three cycles (pairs) or more.

In Experiment 2-1 the flow rate of CH ₄ gas when the lower layer 52 of the multilayer reflective film 5 was formed was 0.24 sccm, which was a relatively low value. In this case, when the low refractive index layer and the high refractive index layer are set as one cycle (pair), the multilayer reflective film 5 has a low refractive index layer and a high refractive index forming the lower layer 52 during 40 cycles (pair). When the number of cycles (number of pairs) when the layer was one cycle (pair) was 20 cycles (pairs) or less (samples 1 to 5), the reflectance to EUV light was 67% or more, which was a good value. That is, in Experiment 2-1, in order for the multilayer reflective film 5 to obtain good reflectance, the number of cycles (pairs) when the low refractive index layer and the high refractive index layer constituting the lower layer 52 are set as one cycle (pair). It can be said that the number of cycles (pairs) is preferably 20 cycles (pairs) or less. Considering the above, in Experiment 2-1 in order to obtain a multilayer reflective film 5 having a low background level of less than 400 and a good reflectance of 67% or more, a low refractive index layer and a high refractive index layer constituting the lower layer 52 are obtained. When the rate layer is one cycle (pair), the number of cycles (number of pairs) is preferably more than 3 cycles (pairs) and 20 cycles (pairs) or less, and 10 cycles (pairs) or more and 20 cycles (pairs) or less. It can be said that it is more preferable.

In Experiment 2-2, the flow rate of CH ₄ gas when the lower layer 52 of the multilayer reflective film 5 was formed was 0.35 sccm, which was a relatively high value. In this case, when the low refractive index layer and the high refractive index layer are set as one cycle (pair), the multilayer reflective film 5 has a low refractive index layer and a high refractive index forming the lower layer 52 during 40 cycles (pair). When the number of cycles (number of pairs) when the layer was one cycle (pair) was 10 cycles (pairs) or less (samples 1 to 3), the reflectance to EUV light was 67% or more, which was a good value. In the case of Experiment 2-2 in which the carbon content of the additive element is higher than that in Experiment 2-1 it is considered that the decrease in reflectance due to the lower layer 52 is further increased. In Experiment 2-2, in order for the multilayer reflective film 5 to obtain good reflectance, the number of cycles (number of pairs) when the low refractive index layer and the high refractive index layer constituting the lower layer 52 are set as one cycle (pair). ) Is less than 15 cycles (pairs) (or 10 cycles (pairs) or less). Considering the above, in Experiment 2-2, in order to obtain a multilayer reflective film 5 having a low background level of less than 400 and a good reflectance of 67% or more, a low refractive index layer and a high refractive index layer constituting the lower layer 52 are obtained. When the rate layer is one cycle (pair), the number of cycles (number of pairs) is preferably 3 cycles (pairs) or more and less than 15 cycles (pairs), and 3 cycles (pairs) or more and 10 cycles (pairs) or less. It can be said that it is more preferable.

(Evaluation result of Experiment 3-1)
In Experiment 3-1 shown in Table 3, when the low refractive index layer of the lower layer 52 was formed, a Mo alloy target containing boron (B) was used as an additive element, so that the lower layer contained boron (B) as an additive element. It was introduced into the low refractive index layer of 52. On the other hand, in Experiment 3-1 when the low refractive index layer of the upper layer 54 of the multilayer reflective film 5 was formed, a Mo target was used to form the film. The presence or absence of boron (B), which is an additive element, in the lower layer 52 and the upper layer 54 was confirmed by TEM-EDX analysis. As a result, it was confirmed that the low refractive index layer of the lower layer 52 contained boron (B), but the high refractive index layer and the upper layer 54 of the lower layer 52 did not contain boron (B). In the case of Sample 1 of Experiment 3-1, the lower layer 52 provided with a laminated film in which a low refractive index layer containing boron (B) as an additive element and a high refractive index layer not containing boron were alternately laminated. Was not formed. Therefore, the background level (BGL) of sample 1 was as high as 413. On the other hand, in the case of Samples 2 to 5 of Experiment 3-1, a low refractive index layer containing boron (B) as an additive element and a high refractive index layer not containing boron (B) were alternately laminated. The background level (BGL) was a low value of less than 400 because the lower layer 52 provided with the laminated film was formed. Therefore, it can be said that the multilayer reflective film 5 having a lower background level at the time of defect inspection can be obtained by having the lower layer 52 containing boron (B) as an additive element.

In the case of Experiment 3-1 the multilayer reflective film 5 constitutes the lower layer 52 in 40 cycles (pairs) when the low refractive index layer and the high refractive index layer are in one cycle (pair). When the number of cycles (number of pairs) is 10 cycles (pairs) or less (samples 1 to 3) when the high refractive index layer is one cycle (pair), the reflectance to EUV light is as good as 67% or more. It was a value. That is, in Experiment 3-1, in order for the multilayer reflective film 5 to obtain good reflectance, the number of cycles (pairs) when the low refractive index layer and the high refractive index layer constituting the lower layer 52 are set as one cycle (pair). It can be said that the number of pairs) is preferably less than 20 cycles (pairs) (less than 20 cycles (pairs)). Considering the above, in Experiment 3, in order to obtain a multilayer reflective film 5 having a low background level of less than 400 and a good reflectance of 67% or more, a low refractive index layer and a high refractive index layer constituting the lower layer 52 are obtained. The number of cycles (number of pairs) when 1 cycle (pair) is defined as 1 cycle (pair), preferably 3 cycles (pair) or more and less than 20 cycles (pair), and 3 cycles (pair) or more and 10 cycles (pair) or less. Is more preferable.

(Evaluation result of Experiment 4-1)
In Experiment 4-1 shown in Table 4, when the low refractive index layer of the lower layer 52 was formed, N ₂ gas was used in addition to Kr gas to use nitrogen (N) as an additive element to lower the lower layer 52. It was introduced into the refractive index layer. On the other hand, only Kr gas was introduced when the high refractive index layer of the lower layer 52 of the multilayer reflective film 5 and the upper layer 54 were formed. The presence or absence of nitrogen (N), which is an additive element in the lower layer 52, was confirmed by TEM-EDX analysis. As a result, it was confirmed that the low refractive index layer of the lower layer 52 contained nitrogen (N), but the high refractive index layer of the lower layer 52 and the upper layer 54 did not contain nitrogen (N). As shown in Table 4, in Experiment 4-1 the flow rate of the N ₂ gas at the time of forming the low refractive index layer of the lower layer 52 was set to 0.25 sccm. In the case of Sample 1 of Experiment 4-1, a laminated film in which a low refractive index layer containing nitrogen (N) as an additive element and a high refractive index layer not containing nitrogen (N) are alternately laminated is provided. The lower layer 52 was not formed. Therefore, the background level (BGL) of sample 1 was as high as 413. Further, the background level (BGL) of the sample 2 in which the lower layer 52 has three cycles (pairs) was as high as 405. On the other hand, in the case of Samples 3 to 6 of Experiment 4-1, a laminated film in which a low refractive index layer containing nitrogen (N) as an additive element and a high refractive index layer not containing nitrogen were alternately laminated. The background level (BGL) was a low value of less than 400 because the lower layer 52 provided with the above was formed. Therefore, it can be said that the multilayer reflective film 5 having a low background level at the time of defect inspection can be obtained by having the lower layer 52 having a low refractive index layer containing nitrogen (N) as an additive element. ..

In the case of Experiment 4-1 when the low-refractive index layer and the high-refractive index layer are in one cycle (pair), the multilayer reflective film 5 constitutes the lower layer 52 in 40 cycles (pair). When the number of cycles (number of pairs) is 20 cycles (pairs) or less (samples 1 to 5) when the high refractive index layer is set to one cycle (pair), the reflectance to EUV light is as good as 67% or more. It was a value. That is, in Experiment 4-1 in order for the multilayer reflective film 5 to obtain good reflectance, the number of cycles (pairs) when the low refractive index layer and the high refractive index layer constituting the lower layer 52 are set as one cycle (pair). It can be said that the number of pairs) is preferably 20 cycles or less. Considering the above, in Experiment 4-1 in order to obtain a multilayer reflective film 5 having a low background level of less than 400 and a good reflectance of 67% or more, a low refractive index layer and a high refractive index layer constituting the lower layer 52 are obtained. When the rate layer is one cycle (pair), the number of cycles (number of pairs) is preferably more than 3 cycles (pairs) and 20 cycles (pairs) or less, and 10 cycles (pairs) or more and 20 cycles (pairs) or less. It can be said that it is more preferable.

(Reflective mask blank 100)
Of the above Experiments 1 to 4, Samples 1 to 4 of Experiment 1-1, Samples 1 to 3 of Experiment 1-2, Sample 1 of Experiment 1-3, Samples 1 to 5 of Experiment 2-1 and Experiment 2- The substrate 110 with a multilayer reflective film of Samples 1 to 3 of 2 and Samples 1 to 3 of Experiment 3 and Samples 1 to 5 of Experiment 4 has a reflectance of 67% or more with respect to EUV light having a wavelength of 13.5 nm, which is exposure light. Yes, it has a multilayer reflective film 5 with high reflectance. However, among the samples of Experiments 1 to 4 described above, the substrate 110 with the multilayer reflective film of Sample 1 of Experiments 1 to 4, Sample 2 of Experiment 2-1 and Sample 2 of Experiment 4-1 is used for defect inspection. Since the background level was as high as 400 or more, the time required for defect inspection was long. Further, since the background level at the time of defect inspection is as high as 400 or more, there is a risk that the substrate 110 with a multilayer reflective film, which is determined not to contain actual defects contributing to transfer, contains actual defects. Therefore, the reflectance is high (67% or more) and the background level is low (less than 400), Samples 2 to 4 of Experiment 1-1, Samples 2 to 3 of Experiment 1-2, and Samples 3 to 5 of Experiment 2-1. , Samples 2 to 3 of Experiment 2-2, Samples 2 to 3 of Experiment 3-1 and Substrate 110 with a multilayer reflective film of Samples 3 to 5 of Experiment 4-1 are used to manufacture a reflective mask blank 100. be able to. Hereinafter, predetermined samples of Experiments 1 to 3 (Samples 2 to 4 of Experiment 1-1, Samples 2 to 3 of Experiment 1-2, Samples 3 to 5 of Experiment 2-1 and Samples 2 to 3 of Experiment 2-2) , A method for manufacturing the reflective mask blank 100 using the samples 2 to 3 of Experiment 3-1 and the substrate 110) with the multilayer reflective film of Samples 3 to 5 of Experiment 4-1 will be described.

((Protective film 6))
A protective film 6 was formed on the surface of the above-mentioned substrate 110 with a multilayer reflective film. In an Ar gas atmosphere, a protective film 6 made of Ru was formed with a film thickness of 2.5 nm by a DC sputtering method using a Ru target.

((Absorbent membrane 7))
Next, a TaBN film having a film thickness of 62 nm was formed as the absorber film 7 by the DC sputtering method. The TaBN film was formed by a reactive sputtering method in a mixed gas atmosphere of Ar gas and N ₂ gas using TaB mixed sintering as a target.

The element ratio of the TaBN film was 75 atomic% for Ta, 12 atomic% for B, and 13 atomic% for N. The refractive index n of the TaBN film at a wavelength of 13.5 nm was about 0.949, and the extinction coefficient k was about 0.030.

((Back conductive film 2))
Next, a back surface conductive film 2 made of CrN was formed on the second main surface (back surface) of the substrate 1 by a magnetron sputtering (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 the predetermined sample of Experiments 1 to 3 is used by using the substrate 110 with the multilayer reflective film of the predetermined sample of Experiments 1 to 3 having high reflectance and low background level. Manufactured.

(Reflective mask 200)
Next, the reflective mask 200 was manufactured using the reflective mask blank 100 of the predetermined sample of Experiments 1 to 4 described above. A method of manufacturing the reflective mask 200 will be described with reference to FIG.

First, as shown in FIG. 4B, a resist film 8 was formed on the absorber film 7 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. 4C). Next, the absorber film 7 (TaBN film) was dry-etched with Cl ₂ gas using the resist pattern 8a as a mask to form the absorber pattern 7a (FIG. 4 (d)). The protective film 6 made of Ru has extremely high dry etching resistance to Cl ₂ gas, and serves as a sufficient etching stopper. Then, the resist pattern 8a was removed by ashing, a resist stripping solution, or the like (FIG. 4 (e)).

As described above, the reflective mask 200 of the predetermined sample of Experiments 1 to 3 was manufactured.

(Manufacturing of semiconductor devices)
A wafer in which a work film and a resist film are formed on a semiconductor substrate by setting the reflective mask 200 manufactured by using the above-mentioned substrate 110 with a multilayer reflective film having high reflectance and low background level in an EUV scanner. EUV exposure was performed on the wafer. 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.

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 Substrate 2 Backside conductive film 5 Multilayer reflective film 6 Protective film 7 Absorber film 7a Absorber pattern 8 Resist film 8a Resist pattern 52 Lower layer 54 Upper layer 100 Reflective mask blank 110 Substrate with multilayer reflective film 200 Reflective mask

Claims (12)

A substrate with a multilayer reflective film, which is composed of a multilayer film in which low refractive index layers and high refractive index layers are alternately laminated on a substrate, and includes a multilayer reflective film for reflecting exposure light.
The multilayer reflective film includes an upper layer and a lower layer arranged between the upper layer and the substrate.
The underlayer contains at least one additive element selected from boron (B), carbon (C), zirconium (Zr), nitrogen (N), oxygen (O) and hydrogen (H).
A substrate with a multilayer reflective film, wherein the upper layer is substantially free of the additive element. 1. The low refractive index layer comprises at least one selected from molybdenum (Mo), ruthenium (Ru), niobium (Nb), rhodium (Rh), and platinum (Pt). The substrate with a multilayer reflective film described in 1. The substrate with a multilayer reflective film according to claim 1 or 2, wherein the high refractive index layer contains silicon (Si). Any one of claims 1 to 3, wherein the content of the additive element in the low refractive index layer of the lower layer is higher than the content of the additive element in the high refractive index layer of the lower layer. Substrate with multilayer reflective film according to the section. The substrate with a multilayer reflective film according to any one of claims 1 to 4, wherein the high refractive index layer of the lower layer does not substantially contain the additive element. The content of the additive element in the low refractive index layer of the lower layer and the pair of the low refractive index layer and the said so that the reflectance of the multilayer reflective film with respect to EUV light having a wavelength of 13.5 nm is 67% or more. The multilayer reflective film according to any one of claims 1 to 5, wherein the period of the multilayer reflective film when the high refractive index layer is set to one cycle and the period of the lower layer are adjusted. With board. The invention according to any one of claims 1 to 6, wherein the period of the multilayer reflective film is 30 to 60 cycles with the pair of the low refractive index layer and the high refractive index layer as one cycle. Substrate with multilayer reflective film. The multilayer layer according to any one of claims 1 to 7, wherein the period of the lower layer is 3 to 20 cycles with the pair of the low refractive index layer and the high refractive index layer as one cycle. Substrate with reflective film. The substrate with a multilayer reflective film according to any one of claims 1 to 8, wherein a protective film is provided on the multilayer reflective film. The absorber film is placed on the multilayer reflective film of the substrate with the multilayer reflective film according to any one of claims 1 to 8 or on the protective film of the substrate with the multilayer reflective film according to claim 9. A reflective mask blank characterized by having. A reflective mask characterized by having an absorber pattern in which the absorber film of the reflective mask blank according to claim 10 is patterned on the multilayer reflective film. A method for manufacturing a semiconductor device, which comprises a step of performing a lithography process using an exposure apparatus using the reflective mask according to claim 11 to form a transfer pattern on a transfer target.