JP7288782B2 - Substrate with multilayer reflective film, reflective mask blank, reflective mask, and method for manufacturing semiconductor device - Google Patents

Description

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

In recent years, in the semiconductor industry, along with the high integration of semiconductor devices, there is a need for fine patterns exceeding the transfer limit of the conventional photolithography method using ultraviolet light. EUV lithography, which is an exposure technique using Extreme Ultra Violet (hereinafter referred to as "EUV") light, is expected to enable formation of such fine patterns. Here, EUV light refers to light in the wavelength band of the soft X-ray region or the vacuum ultraviolet region, specifically light with a wavelength of approximately 0.2 to 100 nm. A reflective mask has been proposed as a transfer mask used in this EUV lithography. Such a reflective mask has a multilayer reflective film formed on a substrate for reflecting exposure light, and an absorber film for absorbing exposure light 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 is reflected by the multilayer reflective film at the portion without the absorber film. The reflected image is transferred onto the semiconductor substrate through a reflective optical system to form a mask pattern. As the multilayer reflective film, for example, a film in which Mo and Si with a thickness of several nanometers are alternately laminated is known as a film that reflects EUV light having a wavelength of 13 to 14 nm.

As a technique for manufacturing a substrate with a multilayer reflective film having such a multilayer reflective film, Patent Document 1 discloses a vacuum chamber for placing 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 depositing and a processing system for processing layers on a multilayer stack deposited as amorphous metal layers. Amorphous metal layers are described as being alloyed with amorphous molybdenum and also with boron, nitrogen or carbon.

Patent Document 2 discloses a multilayer reflector having a multilayer structure consisting of alternate layers of high absorption layers and low absorption layers for soft X-rays or vacuum ultraviolet rays, wherein the high absorption layers are one or more simple transition metals. as a main component, and the low-absorption layer contains either silicon nitride or boron nitride as a main component. there is

Patent Document 3 discloses a multilayer reflector having a multilayer structure consisting of alternate layers of high absorption layers and low absorption layers for soft X-rays and vacuum ultraviolet rays, wherein the high absorption layers are composed of bismuth or lead alone or each of them. soft X-rays and vacuum ultraviolet rays, characterized in that the low-absorption layer comprises, as a main component, one or more of carbon, silicon, boron, or beryllium. A multi-layer reflector is described.

Patent Document 4 discloses a soft X-ray/vacuum ultraviolet multilayer film reflector having a multilayer thin film structure consisting of alternating layers of high absorption layers and low absorption layers for soft X-rays/vacuum ultraviolet rays, wherein the high absorption layer is a transition metal The low-absorption layer is composed of one or more of borides, carbides, silicides, nitrides or oxides of carbon, silicon, boron or beryllium alone or compounds thereof is described as a multilayer film reflector for soft X-rays and vacuum ultraviolet rays, characterized by comprising at least one of the following as a main component.

Japanese translation of PCT publication No. 2016-519329 Patent No. 2566564 JP-A-63-88501 Japanese Patent Publication No. 7-97159

Substrates with multilayer reflective films have been developed from the viewpoint of improving defect quality accompanying the recent miniaturization of patterns and optical properties (surface reflectance of multilayer reflective films, etc.) required for reflective masks. , the interface of each layer of the multilayer reflective film and/or the surface of the multilayer reflective film are required to have higher smoothness. In order to improve the quality of defects in a substrate with a multilayer reflective film, the surface of the substrate with a multilayer reflective film, which is the object of defect inspection, that is, the interface between each layer of the multilayer reflective film and/or the surface of the multilayer reflective film is smoothed, and the multilayer reflective film is smoothed. By reducing the noise (background noise) caused by the interface roughness of each layer and/or the surface roughness of the multilayer reflective film surface, it is possible to detect minute defects (defect signals) present 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 the mask blank substrate. Each of these layers is generally formed by sputtering using a sputtering target made of the material for forming these layers.

As a sputtering method, since it is not necessary to create a plasma by discharge, it is difficult for impurities to mix in the multilayer reflective film, and the ion source is independent, making it relatively easy to set conditions. preferably implemented. 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 to the main surface of the mask blank substrate (a straight line perpendicular to the main surface). That is, the high refractive index layer and the low refractive index layer are formed by causing the sputtered particles to reach the main surface of the substrate at an oblique angle or an angle close to parallel.

During 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 reflective film at the exposed portions of the multilayer reflective film. In order to obtain a 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 (increase the crystal grain size) of each layer constituting the multilayer reflective film. However, when the crystal grain size is increased, the noise (background level: BGL) during defect inspection becomes high, which causes 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 a defect, and it will take a long time to determine whether a real defect contributes to transfer or a pseudo defect that does not contribute to transfer. caused by. Moreover, due to the high background level during the defect inspection, there arises a problem that an actual defect that contributes to transfer is erroneously determined as noise and is not detected. A possible reason for the problem of high background level is that the crystal grains are coarsened and the smoothness of the interface between the layers of the multilayer reflective film and/or the surface of the multilayer reflective film is deteriorated. Due to the deterioration of the smoothness of the interface of each layer of the multilayer reflective film and/or the surface of the multilayer reflective film, the scattering of the inspection light irradiated during the defect inspection increases, which causes an increase in the background level during the defect inspection. can be considered.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a reflective mask blank and a reflective mask having a multilayer reflective film that has a high reflectance to exposure light and a low background level during defect inspection. Further, the present invention provides a reflective mask blank having a multilayer reflective film having a high reflectance to exposure light and a low background level during defect inspection, and a substrate with a multilayer reflective film used for manufacturing the reflective mask. intended to provide A further object of the present invention is to provide a method of manufacturing a semiconductor device using the reflective mask.

Another object of the present invention is 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.

When forming a multilayer reflective film, the present inventors have found that a lower layer (crystal grain size A lower layer with a small value) is formed, and then an upper layer having a laminated film in which a low refractive index layer and a high refractive index layer that contribute to high reflectance and improve crystallinity are alternately laminated is formed. The present inventors have found that a multilayer reflective film having a high reflectance to exposure light and good surface smoothness can be obtained, leading to the present invention. Specifically, since the lower layer is a laminated film in which a low refractive index layer and a high refractive index layer having amorphous or refined crystal grains are alternately laminated, boron, carbon, zirconium, nitrogen, and oxygen The material should contain at least one selected additive element. In addition, since the upper layer is a laminated film in which a low refractive index layer and a high refractive index layer with improved crystallinity are alternately laminated, the low refractive index and high refractive index layers that do not substantially contain the additive element are used. material. By having a multilayer reflective film with good surface smoothness, the background level during defect inspection is reduced, so that the time required for defect inspection of a substrate with a multilayer reflective film having a multilayer reflective film, etc., can be shortened. can be done.

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

(Configuration 1)
Configuration 1 of the present invention is 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 which includes a multilayer reflective film for reflecting exposure light. There is
the multilayer reflective film comprising an upper layer and a lower layer disposed between the upper layer and the substrate;
the underlayer comprises at least one additive element selected from boron (B), carbon (C), zirconium (Zr), nitrogen (N), oxygen (O) and hydrogen (H);
The substrate with a multilayer reflective film is characterized in that the upper layer does not substantially contain the additive element.

By including a predetermined additive element in the lower layer having a laminated film in which low refractive index layers and high refractive index layers are alternately laminated, the crystal grains of the lower layer can be made finer or amorphous. In the substrate with a multilayer reflective film according to Configuration 1 of the present invention, noise during defect inspection of the multilayer reflective film is reduced due to coarsening of the crystal grains due to the presence of the lower layer in which the crystal grains are made finer or amorphous. It is possible to suppress problems such as an increase, an increase in time required for defect inspection, and failure to detect actual defects that contribute to transfer. Furthermore, in the substrate with a multilayer reflective film of Configuration 1 of the present invention, the upper layer, which is a laminated film using materials (low refractive index layer and high refractive index layer) that do not substantially contain additional elements, is formed on the lower layer. By doing so, it is possible to obtain a multilayer reflective film having a high reflectance with respect to exposure light.

(Configuration 2)
Configuration 2 of the present invention is that the low refractive index layer contains at least one selected from molybdenum (Mo), ruthenium (Ru), niobium (Nb), rhodium (Rh), and platinum (Pt). A substrate with a multilayer reflective film of Configuration 1 is characterized.

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

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

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

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

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

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

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

(Composition 6)
In configuration 6 of the present invention, the content of the additive element in the low refractive index layer of the lower layer is such that the reflectance of the multilayer reflective film for EUV light with a wavelength of 13.5 nm is 67% or more. The multilayer according to any one of Structures 1 to 5, wherein 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 defined as one period. A substrate with a reflective film.

According to configuration 6 of the present invention, 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 predetermined reflectance can be obtained. It is possible to obtain a multilayer reflective film with a ratio of 67% or more.

(Composition 7)
Configuration 7 of the present invention is characterized in that the multilayer reflective film comprises a laminated film of 30 to 60 cycles, with one pair of the low refractive index layer and the high refractive index layer being one cycle. 6. The substrate with a multilayer reflective film according to any one of 6 above.

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

(Composition 8)
Configuration 8 of the present invention is characterized in that the lower layer comprises a laminated film of 3 to 20 periods, with one pair of the low refractive index layer and the high refractive index layer being one period. Any substrate with a multilayer reflective film.

According to the configuration 8 of the present invention, the lower layer is provided with a laminated film of 3 to 20 cycles (pair), with one pair of low refractive index layer and high refractive index layer being one cycle (pair), A multilayer reflective film having a high reflectance and a low background level during defect inspection can be obtained more reliably.

(Configuration 10)
Structure 9 of the present invention is the substrate with a multilayer reflective film according to any one of Structures 1 to 8, further comprising a protective film on the multilayer reflective film.

According to Configuration 9 of the present invention, since the protective film is formed on the multilayer reflective film, the surface of the multilayer reflective film is protected when a reflective mask (EUV mask) is manufactured using a substrate with a multilayer reflective film. Since the damage can be suppressed, the reflectance characteristics of the reflective mask with respect to EUV light are improved.

(Configuration 10)
Structure 10 of the present invention has an absorber film on the multilayer reflective film of the substrate with a multilayer reflective film of any one of Structures 1 to 8 or on the protective film of the substrate with a multilayer reflective film of Structure 9. A reflective mask blank characterized by:

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

(Composition 11)
Structure 11 of the present invention is a reflective mask characterized by having an absorber pattern obtained by patterning the absorber film of the reflective mask blank of Structure 10 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 with a high reflectance to exposure light and a low background level during defect inspection. Furthermore, it is possible to obtain a reflective mask free from actual defects that contribute to transfer on the multilayer reflective film.

(Composition 12)
Structure 12 of the present invention is a method of manufacturing a semiconductor device, comprising a step of forming a transfer pattern on a transfer target by performing a lithography process using an exposure apparatus using the reflective mask of Structure 11. be.

According to the method of manufacturing a semiconductor device according to the twelfth aspect of the present invention, a reflective mask having a multilayer reflective film having a high reflectance with respect to exposure light and a low background level during defect inspection is used for manufacturing a semiconductor device. can be used for As a result, throughput in manufacturing semiconductor devices can be improved. Furthermore, when inspecting a substrate with a multilayer reflective film for defects, since the background level is low, a semiconductor device is manufactured using a reflective mask that does not have actual defects that contribute to transfer onto the multilayer reflective film. It is possible to suppress a decrease in the yield of semiconductor devices caused by defects in the reflective film.

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

1 is a schematic cross-sectional view of an example of a substrate with a multilayer reflective film of the present invention; FIG. FIG. 3 is a schematic cross-sectional view of another example of the substrate with a multilayer reflective film of the present invention; 1 is a schematic cross-sectional view of an example of a reflective mask blank of the present invention; FIG. It is process drawing which showed the manufacturing method of the reflective mask of this invention with the cross-sectional schematic diagram.

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

FIG. 1 shows a schematic cross-sectional view of an example of a substrate 110 with a multilayer reflective film according to an embodiment of the present invention. As shown in FIG. 1, a substrate 110 with a multilayer reflective film of this embodiment comprises a substrate 1 and a multilayer reflective film 5 thereon. 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 this 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 multilayer reflective film-coated substrate 110 of this embodiment can include the back 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 this embodiment. In the example shown in FIG. 2, a substrate 110 with a multilayer reflective film includes a protective film 6. In the example shown in FIG.

A reflective mask blank 100 can be manufactured using the substrate 110 with a multilayer reflective film of this embodiment. FIG. 3 shows a schematic cross-sectional view of an example of the reflective mask blank 100. As shown in FIG. Reflective mask blank 100 further includes an absorber film 7 .

Specifically, the reflective mask blank 100 of this embodiment has the absorber film 7 on the outermost surface of the multilayer reflective film-coated substrate 110 (for example, the surface of the multilayer reflective film 5 or protective film 6). By using the reflective mask blank 100 of this embodiment, a reflective mask 200 having a multilayer reflective film 5 with high reflectance for EUV light can be obtained.

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

In this specification, "arranging (forming) the absorber film 7 on the multilayer reflective film 5 (on the multilayer reflective film 5)" means that the absorber film 7 is arranged in contact with the surface of the multilayer reflective film 5. In addition to the case of meaning (formed), it also includes the case of having another film between the multilayer reflective film 5 and the absorber film 7 . The same applies to other films. Further, in this 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 arranged without interposing another film between the film A and the film B. It means that they are placed in direct contact with each other.

<Substrate 110 with multilayer reflective film>
The substrate 1 and each thin film constituting the substrate 110 with a multilayer reflective film of this embodiment will be described below.

<<Substrate 1>>
The substrate 1 in the substrate 110 with a multilayer reflective film of this embodiment needs to prevent the occurrence of absorber pattern distortion due to heat during EUV exposure. Therefore, as the substrate 1, one 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 within this range, for example, SiO ₂ —TiO ₂ -based glass, multicomponent glass-ceramics, or the like can be used.

The first main surface of the substrate 1 on which the transfer pattern (constituted by the absorber film 7 described later) is formed has a predetermined flatness from the viewpoint of obtaining at least pattern transfer accuracy and positional accuracy. surface treated. In the case of EUV exposure, the flatness is preferably 0.1 μm or less, more preferably 0.05 μm or less, and still more preferably 0.05 μm or less in a 132 mm×132 mm region of the main surface of the substrate 1 on which the transfer pattern is formed. It is 0.03 μm or less. The second main surface (rear surface) opposite to the side on which the absorber film 7 is formed is the surface that is electrostatically chucked when it is set in the exposure apparatus. The second main surface preferably has a flatness of 0.1 μm or less, more preferably 0.05 μm or less, and even more preferably 0.03 μm or less in an area of 142 mm×142 mm.

Moreover, the level of surface smoothness of the substrate 1 is also a very 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 terms of root mean square (Rms), more preferably 0.10 nm or less in terms of 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 due to film stress of a film (such as the multilayer reflective film 5) formed on the substrate 1. FIG. In particular, the substrate 1 preferably has a high Young's modulus of 65 GPa or more.

<<Base film>>
The substrate 110 with a multilayer reflective film of this 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 planarizing 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.

A material containing ruthenium or tantalum as a main component is preferably used as the material of the underlying film having the conductive function. For example, a single Ru metal or a single Ta metal may be used, and Ru or Ta may be combined with titanium (Ti), niobium (Nb), molybdenum (Mo), zirconium (Zr), yttrium (Y), boron (B), lanthanum ( La), cobalt (Co), and rhenium (Re) containing at least one metal selected from Ru alloy or Ta alloy. The film thickness of the underlying film is preferably in the range of 1 nm to 10 nm, for example.

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

<<multilayer reflective film 5>>
The multilayer reflective film 5 gives the reflective mask 200 a function of reflecting EUV light. The multilayer reflective film 5 is a multilayer film in which layers mainly composed of elements with different refractive indices are stacked periodically. The multilayer reflective film 5 of this 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 its compound which is a high refractive index material and a thin film (low refractive index layer) of a heavy element or its compound which is a low refractive index material ) are alternately laminated for about 40 to 60 cycles (pairs).

The multilayer film used as the multilayer reflective film 5 has a multilayer structure of a high refractive index layer and 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. Alternatively, a lamination structure of a low refractive index layer and a high refractive index layer in which a low refractive index layer and a high refractive index layer are laminated in this order from the substrate 1 side may be used as one cycle, and a plurality of cycles may be stacked. The outermost 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 multilayer film described above, when stacking a plurality of periods (pair) of a multilayer structure of a high refractive index layer and 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, at least 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 form the multilayer reflective film 5 by further forming a high refractive index layer on the uppermost low refractive index layer. On the other hand, in the above-described multilayer film, when a laminated structure of a low refractive index layer and a high refractive index layer in which a low refractive index layer and a high refractive index layer are laminated in this order from the substrate 1 side is laminated for a plurality of periods as one period (pair). has a high refractive index layer as the uppermost layer. Therefore, in this case, it is not necessary to form an additional high refractive index layer.

A material containing silicon (Si) can be used as the high refractive index layer. As the material containing Si, in addition to simple Si, at least Si 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 with excellent EUV light reflectance can be obtained. As the low refractive index layer, a single 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 this 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 with a wavelength of 13 nm to 14 nm, a Mo/Si periodic laminated film in which a layer containing Mo and a layer 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 (layer containing Si) and the protective film 6, a silicon oxide layer containing silicon and oxygen can be formed. In the case of this structure, mask cleaning resistance can be improved.

As shown in FIG. 1, the multilayer reflective film 5 of this embodiment includes an upper layer 54 and a lower layer 52 . A lower layer 52 is arranged between the upper layer 54 and the substrate 1 . Both the upper layer 54 and the lower layer 52 comprise laminated films in which the above-described high refractive index layers and low refractive index layers are alternately laminated. The materials of the high refractive index layer and the low refractive index layer of the upper layer 54 and the lower layer 52 are basically the above materials (for example, Si as the high refractive index layer and Mo as the low refractive index layer) as main materials. can be done. That is, the main material of the high refractive index layer and the low refractive index layer of the upper layer 54 and the main material 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 composed of boron (B), carbon (C), zirconium (Zr), nitrogen (N), oxygen (O) and hydrogen (H) in addition to the main materials described above. At least one selected additive element is included. 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 additive element. The crystal grains of the lower layer 52 can be made finer or amorphous by containing a predetermined additive element in addition to the main material described above. The presence of the additive element contained in the lower layer 52 can be confirmed by XPS (X-ray photoelectron spectroscopy), RBS (Rutherford backscattering spectroscopy), TEM-EDX (energy dispersive X-ray spectroscopy), or the like. .

The upper layer 54 of the multilayer reflective film 5 of this embodiment does not substantially contain additional elements. That is, the upper layer 54 of this 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 exposure light. Note that "the upper layer 54 does not substantially contain additive elements" means that the additive elements are not intentionally added to the upper layer 54, and elements of the same kind as the additive elements are inevitably present as impurities. It does not exclude cases where

In addition, since the crystal grains of the lower layer 52 containing the additive element are made finer or amorphous, the smoothness of the surface of the multilayer reflective film 5 is improved. It is lower than the laminated film using conventional materials. By forming on the lower layer 52 the upper layer 54 which does not substantially contain the additive element and has improved crystallinity and a high reflectance, the addition of the additive element to the lower layer 52 reduces the reflectance of the lower layer 52. can be suppressed to an insignificant extent. Specifically, the reflectance of the multilayer reflective film 5 can be made 67% or more. Therefore, since the multilayer reflective film 5 of the present embodiment includes the predetermined upper layer 54 and the lower layer 52, the multilayer reflective film 5 has a high reflectance with respect to the exposure light and good surface smoothness.

In the substrate 110 with a multilayer reflective film of this 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). preferably includes at least one These materials have a refractive index of 0.94 or less for EUV light with a wavelength of 13.5 nm. A multilayer reflective film 5 with high reflectance can be obtained.

In the multilayer reflective film-attached substrate 110 of the present embodiment, the high refractive index layer of the multilayer reflective film 5 preferably 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 with a relatively high reflectance can be obtained.

In the substrate 110 with a multilayer reflective film of this 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. Moreover, it is preferable that the high refractive index layer of the lower layer 52 of the multilayer reflective film 5 does not substantially contain an additive element.

In order to obtain the multilayer reflective film 5 with 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, adding an additive element to the high refractive index layer lowers the refractive index for EUV light with a wavelength of 13.5 nm. reflectance may decrease. Therefore, it is preferable to add the additive element to the lower layer 52 mainly to the low refractive index layer of the lower layer 52 . As a result, a decrease in the reflectance of the lower layer 52 can be suppressed, so that the multilayer reflective film 5 with a higher reflectance can be obtained.

In the substrate 110 with a multilayer reflective film of this embodiment, the main material of both the lower layer 52 and the upper layer 54 of the multilayer reflective film 5 is silicon (Si) in the high refractive index layer and molybdenum (Mo) in the low refractive index layer. is preferred. 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). More preferably, the additive element is contained only in the low refractive index layer of the lower layer 52 .

In the multilayer reflective film-attached substrate 110 of the present embodiment, the content of the additive element in the lower refractive index layer of the lower layer 52 is It is preferable that the number of periods (number of pairs) and the number of periods (number of pairs) of the lower layer 52 be adjusted when one period (pair) is a pair of low refractive index layer and high refractive index layer. As a reflective mask 200 for manufacturing a semiconductor device, it is necessary that the reflectance of the multilayer reflective film 5 for EUV light with a wavelength of 13.5 nm is 67% or more. In the multilayer reflective film 5 of this embodiment, 67 % or more can be obtained.

In the multilayer reflective film-attached substrate 110 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. It is more preferably 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 make the crystal grains of the lower layer 52 fine or amorphous. Also, if the content of the additive element in the lower layer 52 is too high, the reflectance of the multilayer reflective film 5 for EUV light with a wavelength of 13.5 nm may decrease to an unacceptable level. Therefore, the content of the additive element in the low refractive index layer of the lower layer 52 is preferably within the predetermined range described above. 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 with respect to exposure light and a low background level during defect inspection can be obtained more reliably. be able to.

In the multilayer reflective film-attached substrate 110 of the present embodiment, the multilayer reflective film 5 has 30 to 60 periods (pairs), where one period (pair) is a pair of a low refractive index layer and a high refractive index layer. It is preferable to have 35 to 55 cycles (pairs), more preferably 35 to 45 cycles (pairs). As the number of cycles (number of pairs) increases, a higher reflectance can be obtained, but the formation time of the multilayer reflective film 5 increases. By setting the period of the multilayer reflective film 5 within an appropriate range, it is possible to obtain the multilayer reflective film 5 with a relatively high reflectance in a relatively short period of time.

In the substrate 110 with a 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), where one cycle (pair) is a pair of a low refractive index layer and a high refractive index layer. It is preferably 3 cycles (pairs) or less, more preferably 3 cycles (pairs) or more and less than 20 cycles (pairs), and still more preferably 3 cycles (pairs) or more and 15 cycles (pairs). Since the lower layer 52 contains the additive element, it has a lower reflectance than the upper layer 54 with 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 making the crystal grains of the lower layer 52 finer or amorphous 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 multilayer has a high reflectance for exposure light and a low background level during defect inspection. Reflective film 5 can be obtained more reliably.

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

It is preferable that the reflectance for EUV light of the multilayer reflective film 5 of the present embodiment alone is usually 67% or more. Since the reflectance is 67% or more, it can be preferably used as a reflective mask 200 for manufacturing a semiconductor device. Preferably, the upper limit of the reflectance is usually 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 according to 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 forming the multilayer reflective film 5 can be selected so as to satisfy the law of Bragg reflection. 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 thicknesses of the high refractive index layers or the thicknesses of the low refractive index layers may not necessarily be the same. Also, the film thickness of the outermost surface (for example, 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 high refractive index layer (for example, Si layer) can be from 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 apparatus. 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 apparatus using EUV light as inspection light, the signal level is Means the background value observed as noise. In the case of blank inspection equipment using EUV light, the background level (BGL) is automatically determined from the measurement signal.

<<Protective film 6>>
In the substrate 110 with a multilayer reflective film of this embodiment, it is preferable to form a protective film 6 on the multilayer reflective film 5 as shown in FIG. By forming the protective film 6 on the multilayer reflective film 5, damage to the surface of the multilayer reflective film 5 can be suppressed when the reflective mask 200 is manufactured using the substrate 110 with the multilayer reflective film. Therefore, the obtained reflective mask 200 has good reflectance characteristics with respect to EUV light.

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 cleaning in the manufacturing process of the reflective mask 200 to be described later. The protective film 6 also has the function of protecting the multilayer reflective film 5 during correction of black defects in the mask pattern using an electron beam (EB). Here, FIG. 2 shows the case where the protective film 6 is one layer. However, the protective film 6 may have a two-layer laminated structure, or the protective film 6 may have a laminated structure of three or more layers, the bottom layer and the top layer are made of, for example, a Ru-containing substance, and the bottom layer and the top layer, a metal other than Ru or an alloy can be interposed. The protective film 6 is made of, for example, a material containing ruthenium as its main component. Materials containing ruthenium as a main component include simple Ru metal, Ru containing titanium (Ti), niobium (Nb), molybdenum (Mo), zirconium (Zr), yttrium (Y), boron (B), and lanthanum (La). , Ru alloys containing at least one metal selected from cobalt (Co) and rhenium (Re), and materials containing nitrogen therein. 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, silicon diffuses from the surface of the multilayer reflective film 5 into the protective film 6 by using the protective film 6 made of a Ti-containing Ru-based material. can be suppressed. As a result, surface roughness during mask cleaning is reduced, and film peeling is less likely to occur. Reducing surface roughness is directly linked to preventing a decrease in the reflectance of the multilayer reflective film 5 with respect to EUV exposure light, and is therefore 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 %, 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 element (for example, silicon) of the multilayer reflective film 5 into the protective film 6 . Moreover, the protective film 6 in this case has a mask cleaning resistance, an etching stopper function when the absorber film 7 is etched, and a change prevention of the multilayer reflective film 5 with time, while sufficiently ensuring the reflectance of the EUV light. It is possible to have both functions.

In EUV lithography, there are few materials that are transparent to exposure light, so an EUV pellicle that prevents foreign matter from adhering to the mask pattern surface is not technically simple. For this reason, pellicle-less operation, which does not use a pellicle, has become mainstream. In EUV lithography, EUV exposure causes exposure contamination such as the deposition of a carbon film on the reflective mask 200 and the growth of an oxide film. Therefore, when the reflective mask 200 is being used for manufacturing a semiconductor device, it is necessary to frequently clean the reflective mask 200 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 a transmissive mask for photolithography. When the protective film 6 made of a Ru-based material containing Ti is used, cleaning liquids such as sulfuric acid, sulfuric acid-permeable water (SPM), ammonia, ammonia-permeable water (APM), OH radical cleaning water, and ozone water with a concentration of 10 ppm or less. The cleaning resistance against is particularly high, and it is 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 EUV light reflectance, 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 employed without particular limitation. Specific examples of the method for forming the protective film 6 include a sputtering method and an ion beam sputtering method.

<Reflective mask blank 100>
An embodiment of the reflective mask blank 100 of this embodiment will be described. By using the reflective mask blank 100 of this embodiment, a reflective mask 200 having a multilayer reflective film 5 with a high reflectance to exposure light and a low background level during defect inspection can be manufactured.

<<absorber film 7>>
A reflective mask blank 100 has an absorber film 7 on the above-described substrate 110 with a multilayer reflective film. That is, the absorber film 7 is formed on the multilayer reflective film 5 (on the protective film 6 when the protective film 6 is formed). The basic function of the absorber film 7 is to absorb EUV light. The absorber film 7 may be an absorber film 7 intended to absorb EUV light, or an absorber film 7 having a phase shift function in consideration of the phase difference of EUV light. The absorber film 7 having a phase shift function absorbs EUV light and partially reflects it to shift the phase. That is, in the reflective mask 200 patterned with the absorber film 7 having a phase shift function, the portion where the absorber film 7 is formed absorbs the EUV light and reduces the light to a level that does not adversely affect the pattern transfer. to reflect some light. Further, in a region (field portion) where the absorber film 7 is not formed, the EUV light is reflected from the multilayer reflective film 5 via the protective film 6 . Therefore, there is a desired phase difference between the reflected light from the absorber film 7 having a phase shift function and the reflected light from the field portion. The absorber film 7 having a phase shift function is formed so that the phase difference between the reflected light from the absorber film 7 and the reflected light from the multilayer reflective film 5 is 170 degrees to 190 degrees. The image contrast of the projected optical image is improved by the interference of the light beams with the phase difference of about 180 degrees reversed at the pattern edge portion. As the image contrast is improved, the resolution is increased, and various latitudes related to exposure such as exposure latitude and focus latitude can be increased.

The absorber film 7 may be a single layer film, or may be a multilayer film composed of a plurality of films. In the case of a single-layer film, the number of steps in manufacturing mask blanks can be reduced, resulting in an increase in production efficiency. In the case of a multilayer film, the optical constants and film thickness can be appropriately set so that the upper absorber film serves as an antireflection film during mask pattern inspection using light. This improves the inspection sensitivity during mask pattern inspection using light. In addition, when a film to which oxygen (O) and nitrogen (N), etc., which improve oxidation resistance are added, is used as the upper absorber film, temporal stability is improved. Thus, by making the absorber film 7 a multilayer film, various functions can be added. In the case where the absorber film 7 has a phase shift function, it is possible to widen the range of adjustment on the optical surface by making it a multilayer film, so it is easy to obtain the desired reflectance. Become.

As a material for the absorber film 7, as long as it has a function of absorbing EUV light and can be processed by etching (preferably by dry etching using chlorine (Cl) or fluorine (F)-based gas), It is not particularly limited. Tantalum (Ta) alone or a tantalum compound containing Ta as a main component can be preferably used as a material having such a function.

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

A tantalum compound for forming the absorber film 7 includes an alloy of Ta. When the absorber film 7 is a Ta alloy, the crystalline state of the absorber film 7 is preferably amorphous or microcrystalline in terms of smoothness and flatness. If the surface of the absorber film 7 is not smooth and 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 preferably 0.5 nm or less, more preferably 0.4 nm or less, still more preferably 0.3 nm or less in terms of root mean square roughness (Rms).

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, a compound containing Ta and B, and further O and Using 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, and a compound containing Ta, Ge and N, etc. can be done.

Ta has a large absorption coefficient for EUV light, and is a material that 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 of the absorber film 7 having excellent workability. Furthermore, by adding B, Si and/or Ge to Ta, an amorphous material can be easily obtained. As a result, the smoothness of the absorber film 7 can be improved. Moreover, if N and/or O are added to Ta, the resistance to oxidation of the absorber film 7 is improved, so that the effect of being able to improve the stability over time can be obtained.

In addition to tantalum or a tantalum compound, 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. mentioned.

<<Back surface conductive film 2>>
Above the second main surface (back surface) of the substrate 1 (on the side opposite to the surface on which the multilayer reflective film 5 is formed, and above the intermediate layer if an intermediate layer such as a hydrogen entry suppression film is formed on the substrate 1) is formed with a back-surface conductive film 2 for electrostatic chuck. For electrostatic chucks, the sheet resistance required for the back surface conductive film 2 is usually 100Ω/□ or less. The method of forming the back conductive film 2 is, for example, magnetron sputtering or ion beam sputtering using a target of metal such as chromium or tantalum, or an alloy thereof. The material containing chromium (Cr) for the back surface conductive film 2 is preferably a Cr compound containing Cr containing at least one selected from boron, nitrogen, oxygen, and carbon. Examples of Cr compounds include CrN, CrON, CrCN, CrCON, CrBN, CrBON, CrBCN and CrBOCN. As the material containing tantalum (Ta) for the back 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 preferred. Examples of Ta compounds include TaB, TaN, TaO, TaON, TaCON, TaBN, TaBO, TaBON, TaBCON, TaHf, TaHfO, TaHfN, TaHfON, TaHfCON, TaSi, TaSiO, TaSiN, TaSiON, and TaSiCON. can. The film thickness of the back surface conductive film 2 is not particularly limited as long as it satisfies the function for electrostatic chucking, but is usually 10 nm to 200 nm. Further, the back conductive film 2 also serves to adjust the stress on the second main surface side of the mask blank 100 . That is, the back 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 absorber film 7 described above, the rear conductive film 2 can be formed on the substrate 110 with a multilayer reflective film. In that case, a substrate 110 with a multilayer reflective film having a rear 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 an “etching mask film”) and/or a resist film on the absorber film 7 . 8 can be provided. Typical materials for etching hard mask films include silicon (Si) and silicon plus at least one element selected from oxygen (O), nitrogen (N), carbon (C) and hydrogen (H). chromium (Cr), and materials obtained by adding at least one element selected from oxygen (O), nitrogen (N), carbon (C) and hydrogen (H) to chromium. Specific examples include SiO ₂ , SiON, SiN, SiO, Si, SiC, SiCO, SiCN, SiCON, Cr, CrN, CrO, CrON, CrC, CrCO, CrCN, and CrOCN. However, when the absorber film 7 is a compound containing oxygen, it is better to avoid using a material containing oxygen (for example, SiO ₂ ) as the 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 patterns.

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 conductive film 2 is provided between the glass substrate as the substrate 1 and the back conductive film 2 containing tantalum or chromium. It is preferable to provide a hydrogen permeation suppression film for suppressing hydrogen permeation. Due to the presence of the hydrogen penetration suppression film, it is possible to suppress hydrogen from being taken into the back conductive film 2 and suppress an increase in compressive stress of the back conductive film 2 .

Any material may be used for the hydrogen permeation suppression film as long as it is a material that is difficult for hydrogen to permeate and can suppress permeation of hydrogen from the substrate 1 to the backside conductive film 2 . Specific examples of materials for the hydrogen penetration suppression film 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 and TaON. The hydrogen penetration suppression film can be a single layer of these materials, or it can be a multi-layer and compositionally graded film.

<Reflective mask 200>
An embodiment of the present invention is a reflective mask 200 having an absorber pattern 7a on the multilayer reflective film 5 by patterning the absorber film 7 of the reflective mask blank 100 described above. By using the reflective mask blank 100 of this embodiment, it is possible to obtain a reflective mask 200 having a multilayer reflective film 5 with a high reflectance to exposure light and a low background level during defect inspection.

A reflective mask 200 is manufactured using the reflective mask blank 100 of the present embodiment. Only a brief description will be given here, and a detailed description will be given later in Examples with reference to the drawings.

A reflective mask blank 100 is prepared, and a resist film 8 is formed on the outermost surface of the first main surface (on the absorber film 7 as described in the following embodiments) (the reflective mask blank 100 ), a desired pattern such as a circuit pattern is drawn (exposed) on the resist film 8, developed, and rinsed to form a predetermined resist pattern 8a.

Using this resist pattern 8a as a mask, the absorber film 7 is dry-etched to form an absorber pattern 7a. As the etching gas, a chlorine-based gas such as Cl ₂ , SiCl ₄ and CHCl ₃ , a mixed gas containing a chlorine-based gas and O ₂ at a predetermined ratio, and a chlorine-based gas and He at a predetermined ratio. mixed gas containing chlorine-based gas and Ar at 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 fluorine-based gases such as CH ₃ F, C ₃ F ₈ , SF ₆ , and F ₂ , mixed gas containing fluorine-based gas and O ₂ at a predetermined ratio, and the like can be used. Here, if the etching gas contains oxygen in the final stage of etching, the surface of the Ru-based protective film 6 is roughened. For this reason, it is preferable to use an etching gas that does not contain oxygen in the over-etching step in which the Ru-based protective film 6 is exposed to etching.

After that, the resist pattern 8a is removed by ashing or a resist stripping solution to form an absorber pattern 7a having a desired circuit pattern formed thereon.

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

<Method for manufacturing a semiconductor device>

The method of manufacturing a semiconductor device according to the embodiment of the present invention has a step of performing a lithography process using an exposure apparatus using the above-described reflective mask 200 to form a transfer pattern on a transfer target.

In this embodiment, a reflective mask 200 having a multilayer reflective film 5 with a high reflectance to exposure light and a low background level during defect inspection can be used for manufacturing a semiconductor device. As a result, throughput in manufacturing semiconductor devices can be improved. Furthermore, since the semiconductor device is manufactured using the reflective mask 200 that does not have actual defects that contribute to transfer on the multilayer reflective film 5, it is possible to suppress the yield reduction of the semiconductor device due to defects in the multilayer reflective film 5. can.

Specifically, by performing EUV exposure using the reflective mask 200 of the present embodiment, a desired transfer pattern can be formed on the semiconductor substrate. In addition to this lithography process, various processes such as etching of the film to be processed, formation of insulating films and conductive films, introduction of dopants, and annealing are performed to manufacture semiconductor devices with desired electronic circuits at a high yield. can do.

Each embodiment will be described below with reference to the drawings.

(Experiment 1, Experiment 2, Experiment 3-1, and Experiment 4-1)
As experiments 1, 2, 3-1, and 4-1, a substrate 110 with a multilayer reflective film was prepared by forming a multilayer reflective film 5 on one main surface of the substrate 1, as shown in FIG. Substrates 110 with multilayer reflective films for Experiments 1, 2, 3-1, and 4-1 were produced as follows.

((substrate 1))
A SiO ₂ —TiO ₂ -based glass substrate, which is a low thermal expansion glass substrate having a size of 6025 (approximately 152 mm×152 mm×6.35 mm) having both the first main surface and the second main surface polished, was prepared. bottom. Polishing comprising a rough polishing process, a fine polishing process, a local polishing process, and a touch polishing process was performed so as to obtain a flat and smooth main surface.

((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 substrate 1 using a DC sputtering apparatus. In order to make the multilayer reflective film 5 suitable for EUV light with a wavelength of 13.5 nm, the high refractive index layer is mainly made of Si and the low refractive index layer is mainly made of Mo. When the refractive index layer and the low refractive index layer are defined as one period (pair), the total number of periods (pair number) of the lower layer 52 and the upper layer 54 is 40 periods (pairs). The multilayer reflective film 52 is formed by alternately laminating a high refractive index layer and a low refractive index layer on the substrate 1 by DC sputtering using a Mo target and a Si target in a predetermined gas atmosphere. bottom. 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 defined as one cycle (pair), and in the same manner, the lower layer 52 and the upper layer 54 are laminated for a total of 40 cycles (pair). A multilayer reflective film 5 was formed.

Table 1 shows gases and flow rates 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 1. In experiment 1 (experiment 1-1, experiment 1-2, and experiment _1-3 ) shown in Table 1, nitrogen (N ) was introduced into the lower layer 52 as an additive element. When forming the upper layer 54, only Kr gas was introduced without using _N2 gas.

As shown in Table 1, when the upper layer 54 and the lower layer 52 together constitute one period (pair) of the low refractive index layer and the high refractive index layer, the multilayer reflective film 52 has a low refractive index layer and a high refractive index layer. The layers were stacked for 40 cycles (pairs). The lower layer periodic number (upper layer periodic number) in Table 1 refers to the periodic number (pair number) when the low refractive index layer and the high refractive index layer constituting the lower layer (upper layer) constitute one period (pair). The same applies to Tables 2, 3, and 4. The numbers in parentheses in the prescribed columns of Table 1 are 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, when the upper layer 54 is one period (pair) of the low refractive index layer and the high refractive index layer, 40 periods (pair) and the lower layer 52 is 0. period (pair). In samples 2 to 6 of Experiment 1-1, the number of pairs (periodic number) of the low refractive index layer and the high refractive index layer in the upper layer 54 to which nitrogen (N) is not added is decreased, and nitrogen (N) is added. The number of pairs (number of periods) 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 multilayer reflective films, Samples 1 to 6, were manufactured.

((Multilayer reflective film 5 in Experiment 2))
In Experiment 2, similarly to Experiment 1, a DC sputtering apparatus was used to form multilayer reflective film 5 having lower layer 52 and upper layer 54 on the first main surface of substrate 1 described above. In order to make the multilayer reflective film 5 suitable for EUV light with a wavelength of 13.5 nm, the high refractive index layer is mainly made of Si and the low refractive index layer is mainly made of Mo. The multilayer reflective film 5 has 40 periods (pairs) of the lower layer 52 and the upper layer 54 when the refractive index layer and the low refractive index layer are defined as one period (pair). The multilayer reflective film 52 was formed by alternately laminating a high refractive index layer and a low refractive index layer on the substrate 1 by DC sputtering using a Mo target and a Si target in a predetermined gas atmosphere. As in Experiment 1, 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 defined as one cycle (pair), and in the same manner, the lower layer 52 and the upper layer 54 are laminated for a total of 40 cycles (pair). A multilayer reflective film 5 was formed.

Table 2 shows gases and flow rates 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 (experiments 2-1 and 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 forming the lower layer 52. bottom.

As shown in Table 2, when the upper layer 54 and the lower layer 52 are combined to form one pair (period) of the low refractive index layer and the high refractive index layer, the multilayer reflective film 52 has a low refractive index layer and a high refractive index layer. The layers were stacked for 40 cycles (pairs). As in Table 1, the numbers in parentheses in the prescribed columns of Table 2 are the number of cycles (number of pairs) of the upper layer 54 .

((Multilayer reflective film 5 of Experiment 3-1))
In Experiment 3-1, a DC sputtering apparatus was used to form a multilayer reflective film 5 having a lower layer 52 and an upper layer 54 on the first main surface of the substrate 1 described above. In order to make the multilayer reflective film 5 suitable for EUV light with a wavelength of 13.5 nm, the high refractive index layer is mainly made of Si and the low refractive index layer is mainly made of Mo. When the refractive index layer and the low refractive index layer are defined as one period (pair number), the total number of periods (pair number) of the lower layer 52 and the upper layer 54 is 40 periods (pairs). The lower layer 52 of the multilayer reflective film 5 uses a Si target and an alloy target of Mo and B, and a Si layer (high (refractive index layers) and Mo layers (low refractive index layers) containing B as an additive element were alternately laminated. The upper layer 54 of the multilayer reflective film 5 is a Si layer (high refractive index layer) that does not contain the above additive elements on the substrate 1 by DC sputtering in a predetermined gas atmosphere using a Si target and a Mo target. and Mo layers (low refractive index layers) containing no additive element were alternately laminated. As in Experiment 1, first, a high refractive index layer (Si 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 defined as one cycle (pair), and in the same manner, the lower layer 52 and the upper layer 54 are laminated for a total of 40 cycles (pair). A multilayer reflective film 5 was formed.

Table 3 shows gases and flow rates 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 3-1. In Experiment 3-1, boron (B) was introduced into the lower layer 52 as an additive element by using an alloy target of Mo and B when forming the low refractive index layer of the lower layer 52 .

As shown in Table 3, in the multilayer reflective film 52, when the upper layer 54 and the lower layer 52 together constitute one cycle (pair) of the low refractive index layer and the high refractive index layer, the low refractive index layer and the high refractive index layer The layers were stacked for 40 cycles (pairs). As in Table 1, the numbers in parentheses in the predetermined columns of Table 3 are the number of cycles (number of pairs) of the upper layer 54 .

((Multilayer reflective film 5 of Experiment 4-1))
In Experiment 4, N ₂ gas was used in addition to the Kr gas when forming the low refractive index layer of the lower layer 52 in Experiment 1-2, and when forming the high refractive index layer of the lower layer 52, A 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, substrates 110 with multilayer reflective films were manufactured for each sample of Experiment 1, Experiment 2, Experiment 3-1, and Experiment 4-1.

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 with a wavelength of 13.5 nm was measured. Tables 1 to 4 show the measurement results of reflectance.

Defect inspection was performed on the multilayer reflective film-attached substrate 110 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 multilayer reflective film 5 is inspected for defects by a predetermined defect inspection apparatus. The "BGL" columns in Tables 1 to 3 show the measurement results of the background level (BGL). 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 multilayer reflective film-attached substrate 110 of each sample of Experiment 1, Experiment 2, Experiment 3-1, and Experiment 4-1 was measured using a flatness measuring device (UltraFlat 200 manufactured by Tropel). The flatness was measured to be 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 was used in addition to Kr gas when forming the lower layer 52 of the multilayer reflective film 5. Nitrogen (N) was introduced 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 (laminated film in which the low refractive index layers and the high refractive index layers are alternately laminated) contained nitrogen (N), whereas the upper layer 54 contained nitrogen (N). I have confirmed that it is not. Further, in Experiments 1-1, 1-2, and 1-3, it was found that the lower layer 52 contained more nitrogen as an additive element as the flow rate of N ₂ gas during film formation increased. confirmed. As shown in Table 1, in Experiments 1-1, 1-2, and 1-3, the N ₂ gas flow rates during film formation were 0.2 sccm, 0.25 sccm, and 0.35 sccm, respectively. Sample 1 of Experiments 1-1, 1-2, and 1-3 has a laminated film in which low refractive index layers and high refractive index layers containing nitrogen (N) as an additive element are alternately laminated. The lower layer 52 was not deposited. 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 The background level (BGL) was as low as less than 400 because the lower layer 52 was formed with a laminated film in which refractive index layers and high refractive index layers were alternately laminated. Therefore, it can be said that the multilayer reflective film 5 having the lower layer 52 containing nitrogen (N) as an additive element can provide the multilayer reflective film 5 with a low background level during defect inspection.

In Experiment 1-1, the flow rate of the N ₂ gas during the formation of the lower layer 52 of the multilayer reflective film 5 was a relatively low value of 0.2 sccm. In this case, when the multilayer reflective film 5 has a low refractive index layer and a high refractive index layer as one period (pair), the low refractive index layer and the high refractive index layer constituting the lower layer 52 and the high refractive index layer are When the number of cycles (pair number) is 15 cycles (pair) or less (Samples 1 to 4) when the number of cycles (pair) is 1 cycle (pair) of the layer, the reflectance for EUV light is a good value of 67% or more. That is, in Experiment 1-1, in order for the multilayer reflective film 5 to obtain a good reflectance, the number of periods ( 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 with 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 It can be said that the number of cycles (pair number) when the index layer is one cycle (pair) is preferably 3 cycles (pair) or more and less than 20 cycles (pair).

In Experiment 1-2, the flow rate of the N ₂ gas during the formation of the lower layer 52 of the multilayer reflective film 5 was an intermediate value of 0.25 sccm. In this case, when the multilayer reflective film 5 has a low refractive index layer and a high refractive index layer as one period (pair), the low refractive index layer and the high refractive index layer constituting the lower layer 52 and the high refractive index layer are When the number of cycles (pair number) is 10 cycles (pair) or less (Samples 1 to 3) when the number of cycles (pair) is 1 cycle (pair) of the layer, the reflectance for EUV light is a good value of 67% or more. That is, in Experiment 1-2, in order for the multilayer reflective film 5 to obtain a good reflectance, the number of periods ( It can be said that the number of pairs) is preferably less than 15 periods (pairs) (less than 15 periods (pairs)). Compared to Experiment 1-1, in Experiment 1-2, in which the content of the additive element nitrogen is high, the decrease in reflectance due to the lower layer 52 is considered to be greater. Considering the above, in Experiment 1-2, in order to obtain a multilayer reflective film 5 with 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 The number of cycles (pair number) when the rate layer is 1 cycle (pair) is preferably 3 cycles (pair) or more and less than 15 cycles (pair), and 3 cycles (pair) or more and 10 cycles (pair) or less. It can be said that it is preferable to be

In Experiment 1-3, the flow rate of the N ₂ gas during the formation of the lower layer 52 of the multilayer reflective film 5 was a relatively high value of 0.35 sccm. 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 was not obtained. Compared to Experiments 1-1 and 1-2, in the case of Experiment 1-3, in which the content of the additive element is large, the decrease in reflectance due to the lower layer 52 is considered to be even greater. It can be said that it is not possible to obtain a multilayer reflective film 5 with a good reflectance when nitrogen, which is an additive element, is contained in a large amount as in Experiment 1-3.

(Evaluation result of Experiment 2)
In experiment 2 (experiments 2-1 and 2-2 ₎ shown in Table 2, carbon (C ) 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 (laminated film in which low refractive index layers and high refractive index layers are alternately laminated) contained carbon (C), but the upper layer 54 contained carbon (C). I have confirmed that it is 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 lower layer 52 contained more carbon as an additive element. As shown in Table 2, in Experiments 2-1 and 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 the sample 1 of Experiments 2-1 and 2-2, the lower layer 52 is provided with a laminated film in which a low refractive index layer and a high refractive index layer containing carbon (C) as an additive element are alternately laminated. did not film. Therefore, the background level (BGL) of sample 1 was as high as 413. Sample 2 of Experiment 2-1 also had a high background level (BGL) of 410. In contrast, the background level (BGL) was as low as less than 400 for samples 3-6 of experiment 2-1 and samples 2-6 of experiment 2-2. In the case of Experiment 2-1, when a low refractive index layer and a high refractive index layer containing carbon (C) as an additive element are defined as one period (pair), at least three periods (pairs) or more of the lower layer 52, and In the case of Experiment 2-2, it can be said that the multilayer reflective film 5 with a low background level during defect inspection can be obtained by having the lower layer 52 of three cycles (pairs) or more.

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

In Experiment 2-2, the flow rate of CH ₄ gas in forming the lower layer 52 of the multilayer reflective film 5 was a relatively high value of 0.35 sccm. In this case, when the multilayer reflective film 5 has a low refractive index layer and a high refractive index layer as one period (pair), the low refractive index layer and the high refractive index layer constituting the lower layer 52 and the high refractive index layer are When the number of cycles (pair number) is 10 cycles (pair) or less (Samples 1 to 3) when the number of cycles (pair) is 1 cycle (pair) of the layer, the reflectance for EUV light is a good value of 67% or more. Compared to Experiment 2-1, in Experiment 2-2, in which the carbon content of the additive element was high, the decrease in reflectance due to the lower layer 52 was considered to be even greater. In Experiment 2-2, in order for the multilayer reflective film 5 to obtain a good reflectance, the number of cycles (the number of pairs ) is preferably less than 15 periods (pairs) (or 10 periods (pairs) or less). Considering the above, in Experiment 2-2, in order to obtain a multilayer reflective film 5 with 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 The number of cycles (pair number) when the rate layer is 1 cycle (pair) is preferably 3 cycles (pair) or more and less than 15 cycles (pair), and 3 cycles (pair) or more and 10 cycles (pair) or less. It can be said that it is more preferable to be

(Evaluation result of experiment 3-1)
In Experiment 3-1 shown in Table 3, when forming the low refractive index layer of the lower layer 52, by using a Mo alloy target containing boron (B) as an additive element, the lower layer with boron (B) as an additive element 52 low refractive index layers. On the other hand, in Experiment 3-1, the film was formed by using a Mo target when forming the low refractive index layer of the upper layer 54 of the multilayer reflective film 5 . The presence or absence of the additive element boron (B) 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 of the lower layer 52 and the upper layer 54 did not contain boron (B). In the case of the 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 containing no boron are alternately laminated. was not deposited. 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, low refractive index layers containing boron (B) as an additive element and high refractive index layers not containing boron (B) were alternately laminated. The background level (BGL) was as low as less than 400 because the lower layer 52 was deposited with a stacked film. Therefore, it can be said that the multilayer reflective film 5 having the lower layer 52 containing boron (B) as an additive element can provide the multilayer reflective film 5 with a low background level during defect inspection.

In the case of Experiment 3-1, when the multilayer reflective film 5 has one period (pair) of a low refractive index layer and a high refractive index layer, the low refractive index layer constituting the lower layer 52 is included in 40 periods (pairs). When the number of cycles (pair number) is 10 cycles (pair) or less (samples 1 to 3) when the number of cycles (pair) is 1 cycle (pair) of the high refractive index layer, the reflectance for EUV light is 67% or more. was a value. That is, in Experiment 3-1, in order for the multilayer reflective film 5 to obtain a good reflectance, the number of periods ( 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 with a low background level of less than 400 and a good reflectance of 67% or more, the low refractive index layer and the high refractive index layer constituting the lower layer 52 The number of cycles (pair number) when is one cycle (pair) is preferably 3 cycles (pair) or more and less than 20 cycles (pair), and is 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 reduce the thickness of the lower layer 52 with nitrogen (N) as an additive element. introduced into the refractive index layer. On the other hand, only Kr gas was introduced when forming the high refractive index layer of the lower layer 52 and the upper layer 54 of the multilayer reflective film 5 . 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 N ₂ gas during the formation of 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 was provided in which a low refractive index layer containing nitrogen (N) as an additive element and a high refractive index layer containing no nitrogen (N) were alternately laminated. The lower layer 52 was not deposited. Therefore, the background level (BGL) of sample 1 was as high as 413. In addition, the background level (BGL) of Sample 2, in which the lower layer 52 has 3 periods (pairs), was a high value of 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 containing no nitrogen were alternately laminated. The background level (BGL) was low, less than 400, because the underlayer 52 was deposited with . Therefore, it can be said that the multilayer reflective film 5 having the lower layer 52 having the low refractive index layer containing nitrogen (N) as an additive element makes it possible to obtain the multilayer reflective film 5 with a low background level during defect inspection. .

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

(Reflective mask blank 100)
Among the above experiments 1-4, samples 1-4 of experiment 1-1, samples 1-3 of experiment 1-2, sample 1 of experiment 1-3, samples 1-5 of experiment 2-1, experiment 2- The substrates 110 with multilayer reflective films of Samples 1 to 3 of Experiment 2, Samples 1 to 3 of Experiment 3, and Samples 1 to 5 of Experiment 4 have a reflectance of 67% or more for EUV light having a wavelength of 13.5 nm, which is exposure light. It has a multi-layer reflective film 5 with high reflectance. However, among the samples of Experiments 1 to 4, the substrates 110 with multilayer reflective films of Sample 1 of Experiments 1 to 4, Sample 2 of Experiment 2-1, and Sample 2 of Experiment 4-1 were used during defect inspection. Since the background level was as high as 400 or more, the time required for defect inspection was long. In addition, since the background level at the time of defect inspection is as high as 400 or higher, there is a risk that the multilayer reflective film-attached substrate 110, which has been determined not to contain actual defects that contribute to transfer, may contain actual defects. Therefore, the reflectance is high (67% or more) and the background level is low (less than 400). , Samples 2 and 3 of Experiment 2-2, Samples 2 and 3 of Experiment 3-1, and Samples 3 and 5 of Experiment 4-1. be able to. Specified samples of Experiments 1-3 (Samples 2-4 of Experiment 1-1, Samples 2-3 of Experiment 1-2, Samples 3-5 of Experiment 2-1, Samples 2-3 of Experiment 2-2) , Samples 2 and 3 of Experiment 3-1, and Samples 3 and 5 of Experiment 4-1.

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

((Absorber film 7))
Next, a TaBN film with a film thickness of 62 nm was formed as the absorber film 7 by a DC sputtering method. The TaBN film was formed by reactive sputtering 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 % Ta, 12 atomic % B, and 13 atomic % N. The TaBN film had a refractive index n of about 0.949 and an extinction coefficient k of about 0.030 at a wavelength of 13.5 nm.

((back surface conductive film 2))
Next, a back conductive film 2 made of CrN was formed on the second main surface (back surface) of the substrate 1 by magnetron sputtering (reactive sputtering) under the following conditions. Conditions for forming the back conductive film 2: Cr target, mixed gas atmosphere of Ar and _N2 (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 was prepared using the substrate 110 with the multilayer reflective film of the predetermined sample of Experiments 1 to 3 having a high reflectance and a 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, developed, and rinsed to form a predetermined resist pattern 8a (FIG. 4(c)). Next, using the resist pattern 8a as a mask, the absorber film 7 (TaBN film) was dry-etched using Cl ₂ gas to form an absorber pattern 7a (FIG. 4D). The protective film 6 made of Ru has extremely high dry etching resistance to _Cl.sub.2 gas and serves as a sufficient etching stopper. After that, the resist pattern 8a is removed by ashing or a resist remover (FIG. 4(e)).

As described above, the reflective masks 200 of predetermined samples for Experiments 1 to 3 were manufactured.

(Manufacture of semiconductor devices)
A wafer in which a film to be processed and a resist film are formed on a semiconductor substrate by setting the reflective mask 200 manufactured using the above substrate 110 with a multilayer reflective film having a high reflectance and a low background level on an EUV scanner. was subjected to EUV exposure. Then, by developing the exposed resist film, a resist pattern was formed on the semiconductor substrate on which the film to be processed was formed.

This resist pattern is transferred to the film to be processed by etching, and various processes such as the formation of insulating films and conductive films, the introduction of dopants, and annealing are performed to manufacture semiconductor devices with desired characteristics at a high yield. We were able to.

REFERENCE SIGNS LIST 1 substrate 2 back 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 (11)

A substrate with a multilayer reflective film, comprising a multilayer film in which a low refractive index layer and a high refractive index layer are alternately laminated on a substrate, and comprising a multilayer reflective film for reflecting exposure light,
the multilayer reflective film comprising an upper layer and a lower layer disposed between the upper layer and the substrate;
the underlayer comprises at least one additive element selected from boron (B), carbon (C), zirconium (Zr), nitrogen (N), oxygen (O) and hydrogen (H);
wherein the upper layer does not substantially contain the additive element;
The content of the additive element in the low refractive index layer as the lower layer is higher than the content of the additive element in the high refractive index layer as the lower layer.
A substrate with a multilayer reflective film characterized by: A substrate with a multilayer reflective film, comprising a multilayer film in which a low refractive index layer and a high refractive index layer are alternately laminated on a substrate, and comprising a multilayer reflective film for reflecting exposure light,
the multilayer reflective film comprising an upper layer and a lower layer disposed between the upper layer and the substrate;
the underlayer comprises at least one additive element selected from boron (B), carbon (C), zirconium (Zr), nitrogen (N), oxygen (O) and hydrogen (H);
wherein the upper layer does not substantially contain the additive element;
A substrate with a multilayer reflective film, wherein the lower high refractive index layer does not substantially contain the additive element. 2. The low refractive index layer includes at least one selected from molybdenum (Mo), ruthenium (Ru), niobium (Nb), rhodium (Rh), and platinum (Pt). 3. The substrate with a multilayer reflective film according to 2 . 4. The substrate with a multilayer reflective film according to claim 1, wherein said high refractive index layer contains silicon (Si). The content of the additive element in the lower low refractive index layer, the pair of low refractive index layers and the 5. The multilayer reflective film according to any one of claims 1 to 4 , wherein the period of the multilayer reflective film and the period of the lower layer are adjusted with respect to one period of the high refractive index layer. board with. 6. The multilayer reflective film according to any one of claims 1 to 5 , wherein the period of the multilayer reflective film is 30 to 60 periods, with one pair of the low refractive index layer and the high refractive index layer being one period. A substrate with a multi-layer reflective film. 7. The multilayer according to any one of claims 1 to 6 , wherein the period of the lower layer is 3 to 20 periods, with one period of the low refractive index layer and the high refractive index layer being one period. Substrate with reflective film. 8. The substrate with a multilayer reflective film according to claim 1, further comprising a protective film on the multilayer reflective film. An absorber film is provided on the multilayer reflective film of the substrate with a multilayer reflective film according to any one of claims 1 to 7 or on the protective film of the substrate with a multilayer reflective film according to claim 8 . A reflective mask blank characterized by comprising: A reflective mask comprising an absorber pattern obtained by patterning the absorber film of the reflective mask blank according to claim 9 on the multilayer reflective film. 11. A method of manufacturing a semiconductor device, comprising the step of performing a lithography process using an exposure apparatus using the reflective mask according to claim 10 to form a transfer pattern on a transfer target.

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