JP2004363570A - Substrate with reflective multilayer film, reflective mask blank, and reflective mask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide materials for a multilayer protective film which provides protection against oxidation without deteriorating its reflectance. <P>SOLUTION: In the reflective multilayer film which is formed by alternatively accumulating materials having relatively high reflectance and low reflectance at the wavelength of incident light, each protective film is made of (a) a single element of Zr, Nb, Y, La, Rh, Ti, or B, (b) a material containing at least one of Zr, Nb, Y, La, Rh, Ti, Si, or Mo as a main component, or (c) a material containing Si and B as main components. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a reflective mask for exposure used in semiconductor manufacturing and the like, and a substrate with a reflective multilayer film suitable for the reflective mask.

In recent years, with the miniaturization of semiconductor devices, EUV lithography, which is an exposure technique using EUV (Extreme Ultra Violet) light, is expected to be promising in the semiconductor industry. Here, EUV light refers to light in a wavelength range of a soft X-ray region or a vacuum ultraviolet region, and specifically, light having a wavelength of about 0.2 to 100 nm. As a mask used in EUV lithography, for example, a reflective mask for exposure described in Patent Document 1 below has been proposed.
Such a reflective mask has a reflective multilayer film that reflects exposure light formed on a substrate, and an absorption film that absorbs exposure light is formed in a pattern on the reflective multilayer film. Light incident on the reflective mask in the exposure machine is absorbed in a portion having an absorption film, and an image reflected by the reflective multilayer film is transferred to a semiconductor substrate through a reflection optical system in a portion having no absorption film.

As the reflective multilayer film, for example, a film in which Mo and Si having a thickness of several nm are alternately stacked for about 40 to 50 periods as shown in FIG. Are known. In order to increase the reflectivity, it is desirable to use a Mo layer having a large refractive index as the uppermost layer. However, Mo is easily oxidized when exposed to the air, and as a result, the reflectivity decreases. Therefore, for example, a Si layer is provided as an uppermost layer as a protective film for preventing oxidation.
As for a multilayer protective film applied to a multilayer reflector or the like, for example, Patent Document 2 below discloses materials such as ruthenium, aluminum oxide, and silicon carbide. Further, Patent Document 3 below discloses a protective film having a double layer structure including a lower layer of Si or Be and an upper layer for preventing oxidation.

Japanese Patent Publication No. 7-27198 JP 2001-330703 A JP 2001-523007 A

When a conventional Si layer is provided as a protective film, a sufficient antioxidant effect cannot be obtained if the thickness of the Si layer is small. Since the layer slightly absorbs EUV light, there is a problem that the reflectance is reduced when the layer is thickened.
In the case of a reflective multilayer film in a reflective mask, the environment for pattern formation on the absorber layer, or the environment for pattern formation on the buffer layer when a buffer layer is provided between the reflective multilayer film and the absorber layer. It is also necessary to have resistance. That is, the material of the protective film, which is the uppermost layer of the reflective multilayer film, needs to consider the condition that a large etching selectivity with respect to the absorber layer or the buffer layer can be obtained.
Conventionally disclosed protective film materials have not been sufficiently satisfactory when examined from the above viewpoints.
Therefore, an object of the present invention is, first, to provide a protective film material capable of sufficiently obtaining an antioxidant effect of a reflective multilayer film without causing a decrease in the reflectance of the reflective multilayer film. An object of the present invention is to provide a substrate with a reflective multilayer film provided with a protective film suitable for a reflective mask.

In order to solve the above problems, a first invention is a substrate with a reflective multilayer film provided on a substrate with a reflective multilayer film for reflecting light to be used, wherein the reflective multilayer film is provided with respect to light to be used. It has a multilayer film in which a material having a relatively high refractive index and a material having a relatively low refractive index are alternately and periodically laminated, and a protective film on the multilayer film.
(A) a simple substance of Zr, Nb, Y, La, Rh, Ti, and B; (b) a material mainly containing at least one element selected from Zr, Nb, Y, La, Rh, Ti, Si, and Mo ( c) A substrate with a reflective multilayer film, which is formed of any of materials containing Si and B as main components.
As described above, by using a specific material for the protective film of the reflective multilayer film, it is possible to prevent the reflective multilayer film from being oxidized without lowering the reflectance.
In a second aspect, the material (b) includes at least one of Zr, Nb, Y, La, Rh, Ti, Si, and Mo and at least one element selected from B, C, N, and O. The substrate with a reflective multilayer film according to the first invention, which is a substance.
As described above, among the compounds mainly containing at least one of Zr, Nb, Y, La, Rh, Ti, Si, and Mo used for the protective film, the borides, carbides, nitrides, and oxides are particularly This is suitable for the present invention because a high reflectance can be obtained.

According to a third aspect of the present invention, the material of the protective film is:
R = (r _X / r _T ) [1 + exp (−2αz)] + exp (−2αz)
(Where, r _x : amplitude reflectance of reflected light at the outermost surface of the multilayer film, r _T : amplitude reflectance of reflected light from the multilayer film excluding the uppermost layer and its lower layer, α: −4πk ₂ / λ ₀ , K ₂ : absorption coefficient of the layer below the uppermost layer, λ ₀ : wavelength in vacuum, z: phase)
Wherein the R index defined by the formula (1) is larger than 1.
The R index will be described in detail later, but by selecting a material having an R index larger than 1 and using it for the protective film of the reflective multilayer film, it is possible to increase the reflectivity as compared with the case of using the conventional Si protective film. Can be done. That is, by providing a protective film by selecting a specific material, a high reflectance can be obtained simultaneously with a sufficient antioxidant effect of the reflective multilayer film.
According to a fourth aspect of the present invention, the protective film is formed on a material having a relatively low refractive index with respect to light to be used among materials constituting the multilayer film. The substrate with a reflective multilayer film according to any one of the above.
In the present invention, in order to increase the reflectivity, a material having a relatively low refractive index among materials having a relatively high refractive index and a relatively low refractive index with respect to light to be used, which constitutes the reflective multilayer film, is used. It is preferable that the uppermost protective film is formed first.
A fifth invention is the substrate with a reflective multilayer film according to any one of the first to fourth inventions, wherein the multilayer film is an alternately laminated film of Mo and Si.
This alternately laminated film of Mo and Si can be preferably used as a reflective multilayer film particularly for EUV light having a wavelength of 13 to 14 nm.

A sixth invention is characterized in that the thickness of the protective film is optimized so that the reflectance of light reflected on the reflective multilayer film is maximized. A substrate with a reflective multilayer film according to any one of the above.
In using the material of the present invention for a protective film, it is possible to maximize the reflectance by appropriately selecting the thickness of the protective film. Therefore, it is preferable that the protective film is formed with a film thickness optimized so that the reflectance is maximized.
A seventh invention is the substrate with a reflective multilayer film according to any one of the first to sixth inventions, wherein the thickness of the protective film is 1.0 nm to 4.0 nm.
By setting the thickness of the protective layer using the material of the present invention within the above range, the reflectance can be increased as compared with, for example, the case where a conventional Si protective film is used.

According to an eighth aspect, there is provided a reflective mask blank comprising a substrate with a reflective multilayer film according to any one of the first to seventh aspects, wherein the reflective mask blank has an absorber layer for absorbing exposure light. is there.
By using a highly stable protective film using the material of the present invention as a protective film of the reflective multilayer film constituting the reflective region of the reflective mask blank, the reflective multilayer film can be sufficiently coated without impairing the reflectance. It is suitable for the production of a reflection type mask because it has an excellent antioxidation effect, has resistance to the etching process when forming a pattern on the absorber layer and the like, and has a high etching selectivity with the absorber layer and the like.
A ninth aspect of the present invention is the reflective mask according to the eighth aspect, wherein a buffer layer containing Cr alone or Cr as a main component is formed between the protective film and the absorber layer. Blanks.
By providing a buffer layer using the material of the present invention between the protective film and the absorber layer, the etching selectivity with the buffer layer can be further increased, which is suitable for the production of a reflective mask.
A tenth aspect of the present invention is a reflective mask, wherein a predetermined transfer pattern is formed on the absorber layer of the reflective mask blank according to the eighth or ninth aspect.
The reflection type mask obtained by using the above-mentioned reflection type mask blank does not cause a decrease in the reflectance due to oxidation or the like in the reflection region of the exposure light (the portion without the absorber pattern). Thus, a highly reflective mask can be obtained.

Hereinafter, embodiments of the present invention will be described in detail.
The substrate with a reflective multilayer film of the present invention is formed on a substrate by forming a reflective multilayer film in which a material having a relatively high refractive index to light to be used and a material having a relatively low refractive index are alternately and periodically laminated. Yes (see FIG. 6 described above), in the present invention, a specific material is used for the uppermost protective film of the reflective multilayer film.
The protective film of the present invention,
(A) a simple substance of Zr, Nb, Y, La, Rh, Ti, and B; (b) a material mainly containing at least one element selected from Zr, Nb, Y, La, Rh, Ti, Si, and Mo ( c) It is formed of any of the materials containing Si and B as main components.
By using such a specific material for the protective film of the reflective multilayer film, a highly stable protective film can be obtained, and the oxidation of the reflective multilayer film can be prevented without lowering the reflectance. Further, by appropriately selecting the thickness of the protective film, the reflectance can be increased, and a sufficient antioxidant effect of the reflective multilayer film can be obtained.

Examples of the material mainly containing at least one element selected from Zr, Nb, Y, La, Rh, Ti, Si, and Mo in (b) above include Zr, Nb, Y, La, Rh, Ti, Si, A compound containing at least one element of Mo and at least one element selected from B, C, N, and O is exemplified.
Among such compounds containing at least one of Zr, Nb, Y, La, Rh, Ti, Si, and Mo as the main components, borides, carbides, nitrides, oxides, and the like particularly have high reflectance. This is preferable for the present invention. _{Specifically, NbC, NbN, ZrB 2,} ZrC, ZrN, NbSi 2, YSi, ZrSi 2, ZrO 2, Y 2 O 3, Nb 2 O, Si 3 N 4, Mo 2 N, LaN, YN, TiN _{, TiO 2, NbB 2, Mo} 2 C, YC 2, SiC, MoSi 2, LaSi, LaB 6 , and the like.
Examples of the material (c) containing Si and B as main components include SiB _{6 and the} like.
Further, in the present invention, of the material having a relatively high refractive index and a relatively low refractive index with respect to light to be used, which constitutes the reflective multilayer film, the uppermost layer is protected on the material having a relatively low refractive index. Forming a film is preferable for increasing the reflectance.

n_x：物質Xの複素屈折率の実数部
k_x：物質Xの複素屈折率の虚数部
なお、Ｘ線波長領域における物質の複素屈折率は、単位体積中に存在する原子の種類と数で決定されるため、物質の密度と組成式が明確であれば計算可能である。 In the present invention, the material of the protective film is preferably a material having an R index larger than 1. By selecting a material whose R index is larger than 1 and using it for the protective film of the reflective multilayer film, it is possible to increase the reflectance as compared with the case of using the conventional Si protective film, and to obtain a sufficient reflection multilayer film. A high reflectance can be obtained simultaneously with the antioxidant effect.
Here, the R index will be described.
The reference structural model is a Mo / Si multilayer film without a protective film as shown in FIG. The top layer is a Mo layer, but this Mo layer is changed to another material to prevent a decrease in reflectance.
To simplify the calculation, the optical path is divided into three as shown in FIG. In these calculations, in EUV exposure, the angle of incidence of EUV light on the mask surface was nearly perpendicular, so the calculation of the reflectivity at the interface was approximated in the case of normal incidence.
The first optical path (optical path 1) is light reflected on the outermost surface of the multilayer film. Amplitude reflectance of the reflected light of the optical path of the top layer of material with the substance X, comprising an amplitude reflectance as r _X far To the following equation. Here, R _X is the energy reflectance at the interface between the substance X and vacuum or at the Si interface (the refractive index of Si can be approximated to vacuum at around 13.4 nm).

n _x : real part of complex refractive index of substance X
k _x : the imaginary part of the complex refractive index of the substance X The complex refractive index of the substance in the X-ray wavelength region is determined by the type and number of atoms present in a unit volume. If it is clear, it can be calculated.

ここでαは以下のように記述される。
α=2ω₀k₂/c (3)
ω₀：真空中での光の角速度
k₂：最上層の下にある層の吸収係数
c：光速
また、角速度ω₀には以下の関係式が成り立つ。
ω＝2πν₀＝2πc／λ₀ (4)
ν₀：真空中での光の振動数
λ₀：真空中での波長
(3)と(4)式から次式が求まる。
α＝−4πk₂／λ₀ (5) The second optical path (optical path 2) is the reflected light at the interface between the uppermost layer material and the underlying Si layer. Amplitude reflectance r _'X of the reflected light of the optical path is as follows in consideration of the absorption due to the optical path.

Here, α is described as follows.
α = 2ω ₀ k ₂ / c (3)
ω ₀ : angular velocity of light in vacuum
k ₂ : absorption coefficient of the layer below the top layer
c: Speed of light Further, the following relational expression holds for the angular velocity ω ₀ .
ω = 2πν ₀ = 2πc / λ ₀ (4)
ν ₀ : frequency of light in vacuum λ ₀ : wavelength in vacuum
The following equation is obtained from equations (3) and (4).
α = −4πk ₂ / λ ₀ (5)

従って、位相を無視して総ての振幅反射率の和を取ると以下の通りとなる。

上記の式で与えられる振幅反射率がr_Tよりも大きくなれば、反射率が増加することとなる。その条件は以下の通りとなる。

この(8)式の左半分を本発明ではR指数と呼ぶことにする。
本発明者らは、上記の式を使って、本発明の保護膜材料のR指数を算出した。多層膜の構造パラメータは下記表１の通りである。 The third optical path (optical path 3) is the reflected light from the multilayer film excluding the uppermost first layer (substance X layer) and second layer (Si layer). When the amplitude reflectance in the absence of these layers put between r _T, the amplitude reflectance of the third optical path r '' it is as follows.

Therefore, the sum of all the amplitude reflectances ignoring the phase is as follows.

Amplitude reflectance given by the above equation is the larger than r _T, so that the reflectance increases. The conditions are as follows.

In the present invention, the left half of the expression (8) will be referred to as an R index.
The present inventors calculated the R index of the protective film material of the present invention using the above equation. Table 1 shows the structural parameters of the multilayer film.

最上層のMo層を他の物質Ｘに変更する。この構造パラメータは低角XRD（X-Ray Diffraction：X線回折）スペクトルの解析で得られた値をそのまま用いた。入射角6度で13.42nm付近にピーク反射率を、13.38nm付近に中心波長を持つサンプルの多層膜部分である。入射角5度、最上層の物質Xの厚さを例えば2nmとし、r_Tを0.68627698の平方根（39周期の多層膜からの反射光）としてR指数を計算した。
本発明の保護層材料の代表例について算出した結果を下記表２に示す。また、表２に挙げた材料のうち代表的な材料（R指数が高い材料）について、その反射率の膜厚依存性を図３に示す。なお、比較のため、Ｓｉ保護膜についての結果も示してある。

The uppermost Mo layer is changed to another substance X. As this structural parameter, a value obtained by analyzing a low-angle XRD (X-Ray Diffraction) spectrum was used as it is. This is a multilayer film portion of a sample having a peak reflectance near 13.42 nm and a central wavelength near 13.38 nm at an incident angle of 6 degrees. The incident angle was 5 degrees, the thickness of the material X in the uppermost layer was, for example, 2 nm, and the R index was calculated with r _T as the square root of 0.68627698 (light reflected from the multilayer film having 39 periods).
Table 2 below shows the results calculated for representative examples of the protective layer material of the present invention. FIG. 3 shows the dependency of the reflectance on the thickness of a representative material (a material having a high R index) among the materials listed in Table 2. For comparison, the results for the Si protective film are also shown.

図３を見ると、多くの材料で、膜厚が大体2.0〜3.5ｎｍの範囲で、反射率の最大値が存在する。特に、干渉が高まる2.8nmよりも薄い膜厚に多くは反射率の最大値が存在するのは、吸収の影響が大きいためであると考えられる。
以上の結果から、本発明の保護膜材料の中でも、特にR指数が１よりも大きな材料であれば、反射率を高めることが可能である。また、R指数が１以下でも、ＳｉのR指数よりも大きければ、Ｓｉ保護膜と同じ膜厚を積層した場合でも反射率の減少を抑制することが可能となる。
また、図３の結果から、保護膜の膜厚に対し反射率のピークが存在することがわかる。従って、本発明の材料を保護膜に適用するに当たって、その保護膜の厚みを適当に選ぶことによって反射率を最大化することが可能であるため、反射率が最大となるように最適化された膜厚で保護膜を形成することが望ましい。
そして、多くの材料で、保護膜の膜厚を１．０ｎｍ〜４．０ｎｍの範囲内とすることにより、従来のＳｉ保護膜を用いる場合よりも反射率を高めることが可能になる。

Referring to FIG. 3, for many materials, the maximum value of the reflectance exists when the film thickness is approximately in the range of 2.0 to 3.5 nm. In particular, it is considered that the reason why the maximum value of the reflectance mostly exists in a film thickness smaller than 2.8 nm where interference increases is because the influence of absorption is large.
From the above results, among the protective film materials of the present invention, if the material has an R index larger than 1, the reflectance can be increased. Further, even if the R index is 1 or less, if it is larger than the R index of Si, it is possible to suppress a decrease in reflectance even when the same thickness as the Si protective film is laminated.
In addition, it can be seen from the results of FIG. 3 that there is a peak in reflectance with respect to the thickness of the protective film. Therefore, in applying the material of the present invention to a protective film, it is possible to maximize the reflectance by appropriately selecting the thickness of the protective film, and thus the material is optimized so that the reflectance is maximized. It is desirable to form a protective film with a thickness.
By setting the thickness of the protective film in the range of 1.0 nm to 4.0 nm with many materials, the reflectance can be increased as compared with the case where the conventional Si protective film is used.

When the uppermost layer of the multilayer film is formed of a single metal film such as Nb or Zr, the uppermost layer itself may be oxidized, and an oxide layer may be formed on the surface. In such a case, since the R index of the uppermost layer material also changes, it is necessary to consider this when designing the film thickness and the like. The optimum film thickness can be determined experimentally. Further, the formation of the oxide layer causes a decrease in the reflectance as compared with the case where the oxide layer is not formed. Nevertheless, in the case of the single metal material such as Nb or Zr of the present invention, the conventional Si It is possible to obtain a high reflectance as compared with the protective layer.
The substrate with a reflective multilayer film provided with the protective film of the present invention can be preferably used for reflective mask blanks and reflective masks because the substrate has an antioxidant effect on the reflective surface and high reflectance. FIG. 4 is a schematic cross-sectional view showing a reflective mask blank and a step of manufacturing a reflective mask using the mask blank.
In one embodiment of the reflective mask blank, as shown in FIG. 4A, a reflective multilayer film 2 is formed on a substrate 1, and further thereon, a buffer layer 3 and an absorber layer 4 are formed. It has a structure.

The substrate 1 is in the range of 0 ± 1.0 × 10 ⁻⁷ / ° C., more preferably in the range of 0 ± 0.3 × 10 ⁻⁷ / ° C. in order to prevent distortion of the pattern due to heat during exposure. Those having a low coefficient of thermal expansion are preferred. As a material having a low coefficient of thermal expansion in this range, any of amorphous glass, ceramic, and metal can be used. For example, in the case of amorphous glass, SiO ₂ —TiO ₂ glass, quartz glass, and in the case of crystallized glass, crystallized glass in which β-quartz solid solution is precipitated can be used. As an example of the metal substrate, an Invar alloy (Fe—Ni-based alloy) or the like can be given. Alternatively, a single crystal silicon substrate can be used.
Further, the substrate 1 is preferably a substrate having high smoothness and flatness in order to obtain high reflectance and high transfer accuracy. In particular, it is preferable to have a smooth surface of 0.2 nmRms or less (smoothness in a 10 μm square area) and a flatness of 100 nm or less (flatness in a 142 mm square area). Further, the substrate 1 preferably has high rigidity in order to prevent deformation of a film formed thereon due to film stress. In particular, those having a high Young's modulus of 65 GPa or more are preferable.
The unit Rms indicating the smoothness is a root mean square roughness, which can be measured with an atomic force microscope. The flatness is a value indicating the surface warpage (amount of deformation) indicated by TIR (Total Indicated Reading), and a plane defined by the least square method with respect to the substrate surface is defined as a focal plane, and is located above the focal plane. It is the absolute value of the height difference between the highest position on the substrate surface and the lowest position on the substrate surface below the focal plane.

As described above, the reflective multilayer film 2 is a multilayer film in which elements having different refractive indices are periodically laminated, and generally includes a thin film of a heavy element or a compound thereof and a thin film of a light element or a compound thereof. A multilayer film in which thin films are alternately stacked for about 40 to 50 cycles is used.
For example, as the reflective multilayer film for EUV light having a wavelength of 13 to 14 nm, the above-described Mo / Si periodic laminated film in which Mo and Si are alternately laminated for about 40 periods is preferably used. In addition, as reflective multilayer films used in the region of EUV light, Ru / Si periodic multilayer film, Mo / Be periodic multilayer film, Mo compound / Si compound periodic multilayer film, Si / Nb periodic multilayer film, Si / Mo / There are a Ru periodic multilayer film, a Si / Mo / Ru / Mo periodic multilayer film, a Si / Ru / Mo / Ru periodic multilayer film, and the like. The material may be appropriately selected depending on the exposure wavelength.
The reflective multilayer film 2 can be formed by forming each layer by a DC magnetron sputtering method, an ion beam deposition method, or the like. In the case of the above-described Mo / Si periodic multilayer film, a Si film having a thickness of about several nm is first formed by a DC magnetron sputtering method in an Ar gas atmosphere using an Si target, and then in an Ar gas atmosphere using a Mo target. After forming a Mo film having a thickness of about several nm and stacking this for one cycle for 30 to 60 cycles, finally, a protective film using the material of the present invention is formed to protect the reflective multilayer film. .
Note that a substrate with a reflective multilayer film obtained by forming the reflective multilayer film 2 on the substrate 1 can be preferably used for a reflective mask blank and a reflective mask as in the present embodiment. Can be used as a stable multilayer mirror that does not cause a decrease in reflectivity due to light.

As in the present embodiment, a buffer layer 3 for protecting the reflective multilayer film 2 when forming a pattern on the absorber layer 4 may be provided between the reflective multilayer film and the absorber layer. The material of the buffer layer 3 is selected from those having resistance to the etching environment at the time of pattern formation and correction of the absorber layer 4.
Of such materials, for example, Cr alone or a material containing Cr as a main component is preferable because of excellent film smoothness. The surface smoothness is further improved by changing the crystalline state of the material containing Cr as the main component to microcrystalline or amorphous.
As a material containing Cr as a main component, a material containing Cr and at least one element selected from N, O, and C can be used. Nitrogen is included to provide excellent smoothness, to improve dry etching resistance by adding carbon, and to reduce the stress of the film by adding oxygen. Specifically, CrN, CrO, CrC, CrNC, CrNOC and the like can be mentioned.
In addition to the material containing Cr as a main component, a material containing SiO ₂ , SiON, and Ru as a main component, a material containing Rh as a main component, a material containing Ti as a main component, and the like can be given.
This buffer layer 3 can be formed on the reflective multilayer film by a sputtering method such as an ion beam sputtering method other than the DC sputtering method and the RF sputtering method.
The thickness of the buffer layer 3 is preferably about 20 to 60 nm when the absorber pattern is corrected using the focused ion beam (FIB), but is 5 to 15 nm when the FIB is not used. Degree.

Next, the absorber layer 4 has a function of absorbing exposure light, for example, EUV light, and is preferably made of tantalum (Ta) alone or a material containing Ta as a main component. The material containing Ta as a main component is usually an alloy of Ta. The crystal state of such an absorber layer is preferably one having an amorphous or microcrystalline structure in terms of smoothness and flatness.
Examples of the material containing Ta as a main component include a material containing Ta and B, a material containing Ta and N, a material containing Ta and B, further containing at least one of O and N, a material containing Ta and Si, and a material containing Ta and Si. And a material containing Ta, Ge, and N, a material containing Ta, Ge, and N, and the like. By adding B, Si, Ge, or the like to Ta, an amorphous material can be easily obtained, and the smoothness can be improved. Further, if N or O is added to Ta, the resistance to oxidation is improved, and thus the effect of improving the stability over time can be obtained.

Among them, particularly preferable materials include, for example, a material containing Ta and B (the composition ratio Ta / B is in a range of 8.5 / 1.5 to 7.5 / 2.5), and Ta, B, and N. Materials (N is 5 to 30 at%, and B is 10 to 30 at% when the remaining components are 100). In the case of these materials, a microcrystalline or amorphous structure can be easily obtained, and good smoothness and flatness can be obtained.
Such Ta alone or the absorber layer containing Ta as a main component is preferably formed by a sputtering method such as magnetron sputtering. For example, in the case of a TaBN film, it can be formed by a sputtering method using a target containing tantalum and boron and using an argon gas to which nitrogen is added. When formed by a sputtering method, the internal stress can be controlled by changing the power supplied to the sputter target and the pressure of the supplied gas. Further, since the film can be formed at a low temperature of about room temperature, the influence of heat on the reflective multilayer film and the like can be reduced.
Other than the material containing Ta as a main component, for example, a material such as WN, TiN, or Ti can be used.
Note that the absorber layer 4 may have a laminated structure of a plurality of layers.
The thickness of the absorber layer 4 may be any thickness as long as EUV light as exposure light can be sufficiently absorbed, and is usually about 30 to 100 nm.

In the present embodiment, the reflective mask blank 10 is configured as described above and has a buffer layer. However, depending on the method of forming a pattern on the absorber layer 4 and the method of correcting the formed pattern, this buffer layer May be omitted.
Next, a process of manufacturing a reflective mask using the reflective mask blanks 10 will be described.
The reflective mask blank 10 of the present embodiment (see FIG. 4A) is obtained by sequentially forming each layer of the reflective multilayer film 2, the buffer layer 3, and the absorber layer 4 on the substrate 1, Is as described above.
Then, an absorber pattern is formed on the absorber layer 4 of the reflective mask blank 10. First, an electron beam resist is applied on the absorber layer 4 and baked. Next, drawing is performed using an electron beam drawing machine, and this is developed to form a predetermined resist pattern 5a.

By using the formed resist pattern 5a as a mask, the absorber layer 4 is dry-etched to form the absorber pattern 4a (see FIG. 2B). When the absorber layer 4 is made of a material containing Ta as a main component, dry etching using chlorine gas can be used.
Note that the resist pattern 5a remaining on the absorber pattern 4a is removed by using hot concentrated sulfuric acid to form a mask 11 (see FIG. 3C).
Usually, an inspection is performed here to determine whether the absorber pattern 4a is formed as designed. For inspection of the absorber pattern 4a, for example, DUV light having a wavelength of about 190 nm to 260 nm is used, and this inspection light is incident on the mask 11 on which the absorber pattern 4a is formed. Here, the inspection light reflected on the absorber pattern 4a and the inspection light reflected on the buffer layer 3 exposed by removing the absorber layer 4 are detected, and the inspection is performed by observing the contrast. Do.

In this way, for example, a pinhole defect (white defect) from which the absorber layer that should not be removed has been removed, or an under-etch defect (black defect) that remains partially without being removed due to insufficient etching is detected. I do. When such a pinhole defect or a defect due to insufficient etching is detected, the defect is corrected.
The pinhole defect can be corrected by, for example, depositing a carbon film or the like on the pinhole by FIB assisted deposition. A method of correcting a defect due to insufficient etching includes a method of removing an unnecessary portion by FIB irradiation. At this time, the buffer layer 3 becomes a protective film for protecting the reflective multilayer film 2 against FIB irradiation.
After the pattern inspection and the correction are completed, the exposed buffer layer 3 is removed according to the absorber pattern 4a, and the pattern 3a is formed on the buffer layer to manufacture the reflective mask 20 (see FIG. 4D). . Here, for example, in the case of a buffer layer made of a Cr-based material, dry etching with a mixed gas containing chlorine and oxygen can be used. In the portion where the buffer layer has been removed, the reflective multilayer film 2, which is the reflection region of the exposure light, is exposed.

The uppermost layer of the exposed reflective multilayer film is formed of the protective film material of the present invention. However, the material containing Nb or Zr as a main component has a high reflectivity, and when the buffer layer is removed, an SiO ₂ or Cr-based buffer is used. This is preferable because a high etching selectivity with the layer can be obtained. Although depending on the material, an etching selectivity of about 6 or more for the Cr-based buffer layer and about 7 or more for the SiO ₂ buffer layer can be obtained.
Further, the advantages of the material (SiB _6, etc.) as a main component the aforementioned B and Si, it is high smoothness of the membrane surface is that the surface is not easily oxidized by dry etching containing oxygen buffer layer.
Further, the advantage of the material containing Y, La, Rh, Ti, Zr, Nb, Si, and Mo as the main components is that the film surface has high smoothness, particularly, nitrides (YN, LaN, TiN, NbN, Si). _{3 N} 4, _Mo 2 _N, etc.), the surface by dry etching containing oxygen is not easily oxidized, because the non-conductor is formed of a thin oxide film be oxidized, the area is small oxide and vacuum absorbed Is large, so that the decrease in reflectance is small.

Lastly, a final confirmation inspection is performed to determine whether the absorber pattern 4a is formed with the dimensional accuracy as specified. Also in the case of this final confirmation inspection, the above-mentioned DUV light is used.
The removal of the buffer layer 3 may be performed as needed. If the required reflectance can be obtained without removing the buffer layer, the buffer layer is processed into the same pattern as the absorber layer. Instead, it can be left on the reflective multilayer film.
The reflective mask manufactured according to the present invention is particularly suitable when EUV light (wavelength: about 0.2 to 100 nm) is used as exposure light. Can be.
Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

(Example 1)
The substrate to be used is a SiO ₂ —TiO ₂ glass substrate (external size: 6 inch square, thickness: 6.3 mm). The thermal expansion coefficient of this substrate is 0.2 × 10 ⁻⁷ / ° C., and the Young's modulus is 67 GPa. This glass substrate was formed by mechanical polishing to have a smooth surface of 0.2 nmRms or less and a flatness of 100 nm or less.
In the present embodiment, a Mo / Si periodic multilayer reflective film was employed as the reflective multilayer film formed on the substrate in order to form a reflective multilayer film suitable for the exposure light wavelength band of 13 to 14 nm. That is, the reflective multilayer film was formed by alternately stacking Mo and Si on the substrate by DC magnetron sputtering. First, a 4.2 nm Si film is formed at an Ar gas pressure of 0.1 Pa using a Si target, and then a 2.8 nm Mo film is formed at an Ar gas pressure of 0.1 Pa using a Mo target. Was repeated for 40 cycles, a 4.2-nm thick Si film was formed, and finally a 2.5-nm thick Zr film was formed as a protective film. The total film thickness is 286 nm. The R index of the Zr protective film is 1.037.
The reflectance of the reflective multilayer film at an incident angle of 2 degrees of 13.4 nm EUV light was 66.5%. The surface roughness of the reflective multilayer film was 0.13 nmRms.
Thus, a substrate with a reflective multilayer film of this example was obtained.

(Example 2)
A buffer layer was formed on the reflective multilayer film of the substrate with a reflective multilayer film obtained in Example 1. As the buffer layer, a chromium nitride film was formed to a thickness of 20 nm. The film was formed by a DC magnetron sputtering method using a Cr target and a mixed gas of Ar and nitrogen as a sputtering gas. In the formed CrNx film, the concentration of N was 10% (X = 0.1).
Next, a material containing Ta, B, and N was formed with a thickness of 80 nm on the buffer layer as an absorber layer. That is, using a target containing Ta and B, 10% of nitrogen was added to Ar, and a film was formed by a DC magnetron sputtering method to obtain a reflective mask blank of this example. In the formed TaBN film, the composition ratio was 0.8 for Ta, 0.1 for B, and 0.1 for N.
Next, using this reflective mask blank, a reflective mask for EUV exposure having a pattern for a 16 Gbit-DRAM having a design rule of 0.07 μm was manufactured as follows.

First, an EB resist was coated on the reflective mask blanks, and a resist pattern was formed by EB drawing and development.
Using this resist pattern as a mask, the absorber layer was dry-etched using chlorine to form a pattern on the absorber layer.
Further, using a mixed gas of chlorine and oxygen, the buffer layer remaining on the reflection region (the portion without the pattern of the absorber layer) is removed by dry etching according to the pattern of the absorber layer, and the reflection multilayer film is formed. It was exposed and a reflective mask was obtained. In the case of the Zr protective film, the etching selectivity with the buffer layer is 8.5.
A final check of the obtained reflective mask was performed, and it was confirmed that a pattern for a 16 Gbit DRAM having a design rule of 0.07 μm was formed as designed. Further, the reflectivity of EUV light in the reflection region was 66.5%.

Next, using the obtained reflection type mask of the present example, exposure transfer was performed on a semiconductor substrate shown in FIG. 5 by a pattern transfer device using EUV light.
The pattern transfer device 50 equipped with a reflection type mask is roughly composed of a laser plasma X-ray source 31, a reduction optical system 32, and the like. The reduction optical system 32 uses an X-ray reflection mirror. By the reduction optical system 32, the pattern reflected by the reflection type mask 20 is reduced to about 1/4. Since a wavelength band of 13 to 14 nm is used as the exposure wavelength, it was set in advance so that the optical path was in vacuum.
In such a state, EUV light obtained from the laser plasma X-ray source 31 is incident on the reflective mask 20, and the light reflected here is passed through a reduction optical system 32 onto a silicon wafer (semiconductor substrate with a resist layer) 33. Transferred to
Light incident on the reflective mask 20 is absorbed by the absorber layer and is not reflected at a portion where the absorber pattern 4a exists, while light incident on a portion without the absorber pattern 4a is reflected by the reflective multilayer film 2. Is done. Thus, an image formed by the light reflected from the reflective mask 20 enters the reduction optical system 32. The exposure light having passed through the reduction optical system 32 exposes a transfer pattern to a resist layer on the silicon wafer 33. Then, a resist pattern was formed on the silicon wafer 33 by developing the exposed resist layer.
When the pattern was transferred onto the semiconductor substrate as described above, it was confirmed that the accuracy of the reflective mask of this example was 16 nm or less, which is the required accuracy of the 70 nm design rule.

(Example 3)
A substrate with a reflective multilayer film was manufactured in the same manner as in Example 1 except that the protective film in the reflective multilayer film of Example 1 was formed of NbN. The NbN protective film was formed to a thickness of 2.5 nm by an ion beam sputtering method using an Nb target, and was then nitrided by irradiating nitrogen plasma with an assist gun.
The composition of the formed NbN protective film is Nb: 51%, N: 49%, and the R index is 1.047. The EUV light reflectance was 68.2%.
When the substrate with the reflective multilayer film was left in the air for 100 days, no change in the reflectivity of EUV light was observed.
Next, using this substrate with a reflective multilayer film, a reflective mask blank and a reflective mask were manufactured in the same manner as in Example 2. In the case of the NbN protective film, the etching selectivity with respect to the buffer layer is 11. In addition, the reflectivity of EUV light in the reflection area of the reflection type mask was 68.2%.
Further, when the pattern was transferred onto a semiconductor substrate using the apparatus shown in FIG. 5, it was confirmed that the accuracy of the reflective mask of this example was 16 nm or less, which is the required accuracy of the 70 nm design rule.

(Example 4)
A substrate with a reflective multilayer film was manufactured in the same manner as in Example 1 except that the protective film in the reflective multilayer film of Example 1 was formed of NbC. The NbC protective film was formed to a thickness of 2.4 nm by DC magnetron sputtering using an NbC target.
The composition of the formed NbC protective film is Nb: 50%, C: 50%, and the R index is 1.052. The EUV light reflectance was 68.0%.
When the substrate with the reflective multilayer film was left in the air for 100 days, no change in the reflectivity of EUV light was observed.
Next, using this substrate with a reflective multilayer film, a reflective mask blank and a reflective mask were manufactured in the same manner as in Example 2. In the case of the NbC protective film, the etching selectivity with respect to the buffer layer is 15. In addition, the reflectivity of EUV light in the reflection region of the obtained reflection type mask was 68.0%.
Further, when the pattern was transferred onto a semiconductor substrate using the apparatus shown in FIG. 5, it was confirmed that the accuracy of the reflective mask of this example was 16 nm or less, which is the required accuracy of the 70 nm design rule.

(Example 5)
To prepare a reflective multilayer film substrate except for forming a protective film on the reflective multilayer film of Example 1 in SiB ₆ in the same manner as in Example 1. The SiB ₆ protective film was formed to a thickness of 2.1 nm by an ion beam sputtering method using a SiB ₆ target.
The composition of the formed protective film is Si: 14%, B: 86%, and the R index is 1.013. The EUV light reflectance was 67.1%.
When the substrate with the reflective multilayer film was left in the air for 100 days, no change in the reflectivity of EUV light was observed.
Next, using this substrate with a reflective multilayer film, a reflective mask blank and a reflective mask were manufactured in the same manner as in Example 2. In the case of the SiB ₆ protective film, the etching selectivity with respect to the buffer layer is 8. In addition, the reflectivity of EUV light in the reflection region of the obtained reflection type mask was 67.1%.
Further, when the pattern was transferred onto a semiconductor substrate using the apparatus shown in FIG. 5, it was confirmed that the accuracy of the reflective mask of this example was 16 nm or less, which is the required accuracy of the 70 nm design rule.

(Example 6)
A substrate with a reflective multilayer film was manufactured in the same manner as in Example 1 except that the protective film in the reflective multilayer film of Example 1 was formed of ZrC. The ZrC protective film was formed to a thickness of 2.6 nm by a DC magnetron sputtering method using a ZrC target.
The composition of the formed ZrC protective film is Zr: 34%, C: 66%, and the R index is 1.033. The EUV light reflectance was 66.9%.
When the substrate with the reflective multilayer film was left in the air for 100 days, no change in the reflectivity of EUV light was observed.
Next, using this substrate with a reflective multilayer film, a reflective mask blank and a reflective mask were manufactured in the same manner as in Example 2. In the case of the ZrC protective film, the etching selectivity with respect to the buffer layer is 8. In addition, the reflectivity of EUV light in the reflection area of the obtained reflection type mask was 66.9%.
Further, when the pattern was transferred onto a semiconductor substrate using the apparatus shown in FIG. 5, it was confirmed that the accuracy of the reflective mask of this example was 16 nm or less, which is the required accuracy of the 70 nm design rule.

(Example 7)
A substrate with a reflective multilayer film was manufactured in the same manner as in Example 1 except that the protective film in the reflective multilayer film of Example 1 was formed of Nb. The Nb protective film was formed to a thickness of 2.6 nm by an ion beam sputtering method using an Nb target.
The R index of the formed Nb protective film is 1.057. The EUV light reflectance was 68.3%.
Using this substrate with a reflective multilayer film, a reflective mask blank and a reflective mask were manufactured in the same manner as in Example 2. In the case of the Nb protective film, the etching selectivity with respect to the buffer layer is 15. In addition, the reflectivity of EUV light in the reflection region of the obtained reflection type mask was 68.0%.
Further, when the pattern was transferred onto a semiconductor substrate using the apparatus shown in FIG. 5, it was confirmed that the accuracy of the reflective mask of this example was 16 nm or less, which is the required accuracy of the 70 nm design rule.

(Example 8)
A substrate with a reflective multilayer film was manufactured in the same manner as in Example 1 except that the protective film in the reflective multilayer film of Example 1 was formed of Si ₃ N ₄ . The Si ₃ N ₄ protective film was formed to a thickness of 1.5 nm by ion beam sputtering using a Si ₃ N ₄ target and a mixed gas of Ar and N ₂ as a gas supplied to the assist gun. . In addition, since part of nitrogen contained in the target is desorbed by ion beam sputtering alone, in order to compensate for this, nitrogen was irradiated by nitrogen plasma with an assist gun during film formation to compensate for desorbed nitrogen.
The R index of the formed Si ₃ N ₄ protective film is 0.997. The EUV light reflectance was 65.6%.
Using this substrate with a reflective multilayer film, a reflective mask blank and a reflective mask were manufactured in the same manner as in Example 2. In the case of the Si ₃ N ₄ protective film, the etching selectivity with respect to the buffer layer is 15. In addition, the reflectivity of EUV light in the reflection region of the obtained reflection type mask was 65.4%.
Further, when the pattern was transferred onto a semiconductor substrate using the apparatus shown in FIG. 5, it was confirmed that the accuracy of the reflective mask of this example was 16 nm or less, which is the required accuracy of the 70 nm design rule.

(Example 9)
A substrate with a reflective multilayer film was manufactured in the same manner as in Example 1 except that the protective film in the reflective multilayer film of Example 1 was formed of Mo ₂ N. The Mo ₂ N protective film was formed to a thickness of 2.6 nm by an ion beam sputtering method using a Mo target. At this time, nitriding was performed by irradiating nitrogen plasma with an assist gun.
The R index of the formed Mo ₂ N protective film is 1.067. The EUV light reflectance was 67.2%.
Using this substrate with a reflective multilayer film, a reflective mask blank and a reflective mask were manufactured in the same manner as in Example 2. In the case of the Mo ₂ N protective film, the etching selectivity with respect to the buffer layer is 15. The reflectivity of the obtained reflective mask for EUV light in the reflective area was 67.0%.
Further, when the pattern was transferred onto a semiconductor substrate using the apparatus shown in FIG. 5, it was confirmed that the accuracy of the reflective mask of this example was 16 nm or less, which is the required accuracy of the 70 nm design rule.

(Example 10)
A substrate with a reflective multilayer film was manufactured in the same manner as in Example 1 except that the protective film in the reflective multilayer film of Example 1 was formed of LaN. The LaN protective film was formed to a thickness of 2.4 nm by an ion beam sputtering method using a La target. At this time, nitriding was performed by irradiating nitrogen plasma with an assist gun.
The R index of the formed LaN protective film is 0.975. The EUV light reflectance was 66.2%.
Using this substrate with a reflective multilayer film, a reflective mask blank and a reflective mask were manufactured in the same manner as in Example 2. In the case of the LaN protective film, the etching selectivity with respect to the buffer layer is 15. In addition, the reflectivity of EUV light in the reflection region of the obtained reflection type mask was 66.1%.
Further, when the pattern was transferred onto a semiconductor substrate using the apparatus shown in FIG. 5, it was confirmed that the accuracy of the reflective mask of this example was 16 nm or less, which is the required accuracy of the 70 nm design rule.

(Example 11)
A substrate with a reflective multilayer film was manufactured in the same manner as in Example 1 except that the protective film in the reflective multilayer film of Example 1 was formed of YN. The YN protective film was formed to a thickness of 2.5 nm by an ion beam sputtering method using a Y target. At this time, nitriding was performed by irradiating nitrogen plasma with an assist gun.
The R index of the formed YN protective film is 1.027. The EUV light reflectance was 66.7%.
Using this substrate with a reflective multilayer film, a reflective mask blank and a reflective mask were manufactured in the same manner as in Example 2. In the case of the YN protective film, the etching selectivity with respect to the buffer layer is 12. In addition, the reflectivity of EUV light in the reflection region of the obtained reflection type mask was 66.4%.
Further, when the pattern was transferred onto a semiconductor substrate using the apparatus shown in FIG. 5, it was confirmed that the accuracy of the reflective mask of this example was 16 nm or less, which is the required accuracy of the 70 nm design rule.

(Example 12)
A substrate with a reflective multilayer film was manufactured in the same manner as in Example 1 except that the protective film in the reflective multilayer film of Example 1 was formed of TiN. The TiN protective film was formed to a thickness of 2.1 nm by an ion beam sputtering method using a Ti target. At this time, nitriding was performed by irradiating nitrogen plasma with an assist gun.
The R index of the formed TiN protective film is 0.996. The EUV light reflectance was 65.9%.
Using this substrate with a reflective multilayer film, a reflective mask blank and a reflective mask were manufactured in the same manner as in Example 2. In the case of the TiN protective film, the etching selectivity with respect to the buffer layer is 15. The reflectivity of EUV light in the reflection area of the obtained reflection type mask was 65.7%.
Further, when the pattern was transferred onto a semiconductor substrate using the apparatus shown in FIG. 5, it was confirmed that the accuracy of the reflective mask of this example was 16 nm or less, which is the required accuracy of the 70 nm design rule.

(Example 13)
A substrate with a reflective multilayer film was manufactured in the same manner as in Example 1 except that the protective film in the reflective multilayer film of Example 1 was formed of TiO ₂ . The TiO ₂ protective film was formed to a thickness of 2.1 nm by ion beam sputtering using a Ti target and a mixed gas of Ar and O ₂ as a gas supplied to the assist gun.
The R index of the formed TiO ₂ protective film is 0.982. The EUV light reflectance was 65.9%.
Using this substrate with a reflective multilayer film, a reflective mask blank and a reflective mask were manufactured in the same manner as in Example 2. In the case of the TiO ₂ protective film, the etching selectivity with the buffer layer is 21. The reflectivity of EUV light in the reflection area of the obtained reflection type mask was 65.7%.
Further, when the pattern was transferred onto a semiconductor substrate using the apparatus shown in FIG. 5, it was confirmed that the accuracy of the reflective mask of this example was 16 nm or less, which is the required accuracy of the 70 nm design rule.

(Comparative example)
As in Example 1, Si and Mo were alternately stacked on the substrate by DC magnetron sputtering for 40 cycles, and finally, a 11-nm thick Si film was formed as a protective film.
The R index of this Si protective film is 0.995. The reflectivity of EUV light with respect to this reflective multilayer film was 64.2%.
When the substrate with the reflective multilayer film was left in the air for 100 days, almost no change in the reflectivity of EUV light was observed.
As exemplified above, in each of the above embodiments, by forming the protective film with a thin film of about 2 to 3 nm using the material of the present invention, a sufficient anti-oxidation effect of the reflective multilayer film can be obtained, and the EUV light , A high reflectance of 65% or more can be obtained. In the case of a reflective mask, it is desirable that the reflectance of the exposure light in the reflective area of the reflective mask be 65% or more, in order to increase the exposure contrast at the time of pattern transfer and improve the exposure characteristics. On the other hand, in the case where the conventional Si protective film is used, the reflectance is lower than 65% since the thickness is formed to be 11 nm in order to obtain a sufficient oxidation preventing effect, and the reflectance is increased. It is difficult. By the way, when the uppermost layer is a Mo layer and a protective film is not provided thereon, if it is left in the air for 100 days, the reflectance is reduced by about 2 to 3%. It is important to provide a protective film.
In the above-described embodiments, only the examples of the reflective mask blanks and the reflective mask in which the buffer layer is formed between the protective film and the absorber layer made of the material of the present invention have been described. However, the present invention is not limited thereto, and may be a reflective mask blank or a reflective mask in which an absorber layer made of a material such as TaBN is directly formed on a protective film made of the material of the present invention without forming a buffer layer.

(The invention's effect)
As described in detail above, according to the present invention, by using a specific material for the protective film of the reflective multilayer film, the oxidation of the reflective multilayer film can be prevented without reducing the reflectance. I can do it.
In addition, by selecting a material having an R index larger than 1 and using the same as the protective film of the reflective multilayer film according to the present invention, the reflectance can be increased as compared with the case where a conventional Si protective film is used. A high reflectance can be obtained simultaneously with a sufficient antioxidant effect of the film.
Further, in the present invention, the reflectance can be increased by forming the uppermost protective film on a material having a relatively low refractive index with respect to light to be used among the materials constituting the multilayer film.
The present invention is particularly suitable for a reflective multilayer film composed of alternately laminated films of Mo and Si for EUV light having a wavelength of 13 to 14 nm.

Further, in the present invention, it is possible to maximize the reflectance by optimizing the thickness of the protective film, and the protective film is formed with a film thickness optimized so that the reflectance is maximized. Thereby, a high reflectance can be obtained together with an antioxidant effect.
Further, in the present invention, by setting the thickness of the protective layer using the material of the present invention in the range of 1.5 nm to 4 nm, the reflectance can be increased as compared with the case where the conventional Si protective film is used.
Further, according to the present invention, the reflectance is impaired by using a highly stable protective film using the material of the present invention as the protective film of the reflective multilayer film constituting the reflective region of the reflective mask blank. Instead, a sufficient antioxidation effect of the reflective multilayer film can be obtained, and a high etching selectivity with respect to the absorber layer, the buffer layer, and the like can be obtained, which is suitable for manufacturing a reflective mask.
In addition, the reflection type mask obtained by using the above-mentioned reflection type mask blanks is stable according to the present invention because the reflectance is not reduced by the oxidation or the like in the reflection region of the exposure light (the portion without the absorber pattern). A reflection type mask having exposure characteristics is obtained.

FIG. 3 is a cross-sectional view of a reflective multilayer film having a model structure for calculating an R index of a protective film material according to the present invention. FIG. 3 is a schematic diagram of an optical path for calculating an R index of a protective layer material according to the present invention. FIG. 3 is a diagram showing the dependence of the reflectance of a protective film material on the film thickness. It is sectional drawing which shows the structure of one Embodiment of a reflective mask blank, and the process of manufacturing a reflective mask using this mask blank. FIG. 2 is a diagram illustrating a schematic configuration of a pattern transfer apparatus using a reflection type mask. It is sectional drawing of the conventional Mo / Si reflection multilayer film.

Explanation of reference numerals

REFERENCE SIGNS LIST 1 substrate 2 reflective multilayer film 3 buffer layer 4 absorber layer 10 reflective mask blanks 20 reflective mask 50 pattern transfer device

Claims (10)

A substrate with a reflective multilayer film provided on the substrate, a reflective multilayer film that reflects light used,
The reflective multilayer film includes a multilayer film in which a material having a relatively high refractive index with respect to light to be used and a material having a relatively low refractive index are alternately and periodically laminated, and a protective film on the multilayer film. The membrane is
(A) a simple substance of Zr, Nb, Y, La, Rh, Ti, and B; (b) a material mainly containing at least one element selected from Zr, Nb, Y, La, Rh, Ti, Si, and Mo ( c) A substrate with a reflective multilayer film, which is formed of any of materials containing Si and B as main components.   The material (b) is a substance containing at least one of Zr, Nb, Y, La, Rh, Ti, Si, and Mo and at least one element selected from B, C, N, and O. The substrate with a reflective multilayer film according to claim 1. Of the material of the protective film,
R = (r _X / r _T ) [1 + exp (−2αz)] + exp (−2αz)
(Where, r _x : amplitude reflectance of reflected light at the outermost surface of the multilayer film, r _T : amplitude reflectance of reflected light from the multilayer film excluding the uppermost layer and its lower layer, α: −4πk ₂ / λ ₀ , K ₂ : absorption coefficient of the layer below the uppermost layer, λ ₀ : wavelength in vacuum, z: phase)
3. The substrate with a reflective multilayer film according to claim 1, wherein the R index defined by is larger than 1. 3.   The reflection according to any one of claims 1 to 3, wherein the protective film is formed on a material having a relatively low refractive index with respect to light to be used, among materials constituting the multilayer film. Substrate with multilayer film.   5. The substrate with a reflective multilayer film according to claim 1, wherein the multilayer film is an alternately laminated film of Mo and Si.   The reflective multilayer film according to any one of claims 1 to 5, wherein the thickness of the protective film is optimized so that the reflectance of light reflected on the reflective multilayer film is maximized. With board.   7. The substrate with a reflective multilayer film according to claim 1, wherein the thickness of the protective film is 1.0 nm to 4.0 nm.   A reflective mask blank, comprising an absorber layer that absorbs exposure light, on the reflective multilayer film of the substrate with a reflective multilayer film according to claim 1.   The reflective mask blank according to claim 8, wherein a buffer layer containing Cr alone or Cr as a main component is formed between the protective film and the absorber layer.   A reflective mask, wherein a predetermined transfer pattern is formed on the absorber layer of the reflective mask blank according to claim 8.

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