JP2001330705A - Antireflection film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antireflection film having its antireflection effect to light in the wide wavelength range of about 350-550 nm and alignment light. SOLUTION: The antireflection film is obtained by successively stacking a first layer L1 comprising a medium refractive index material, a second layer L2 comprising a low refractive index material, a third layer L3 comprising the medium refractive index material, a fourth layer L4 comprising a high refractive index material and a fifth layer L5 comprising the low refractive index material on a substrate L0. When the median wavelength of a wavelength range used is regarded as the designed principal wavelength, the conditional expressions 1.35<nL<1.48, 1.50<nM<1.70 and 1.90<nH<2.60 (where nL, nM and nH are the refractive indexes of the low, medium and high refractive index materials to the designed principal wavelength, respectively) are satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antireflection film, and more particularly to various optical instruments (such as an optical microscope).
The present invention relates to an antireflection film used for antireflection in a two-wavelength region in the optical system described above.

[0002]

2. Description of the Related Art Recently, an optical system using light in the ultraviolet region (wavelength 190 nm to 300 nm) for exposure and light in the long wavelength region (600 nm to 900 nm) for alignment has been developed in a photolithography apparatus and the like. . 193.4n for ultraviolet wavelength
m (ArF laser), 248 nm (KrF laser), etc., and the wavelength of the alignment light (that is, the wavelength at which the photoresist is not exposed) is 632.8 nm (He-Ne laser); 670 nm, 720 nm, 7 nm
80 nm, 810 nm (semiconductor laser) and the like.

For the purpose of use in the above optical system, an antireflection film for preventing reflection in a two-wavelength region is disclosed in Japanese Patent Application Laid-Open No. 6-1606.
No. 02, JP-A-7-244202, JP-A-7-244203, and the like. The layer made of a high refractive index material is H,
Assuming that the layer made of the intermediate refractive index material is M and the layer made of the low refractive index material is L, the antireflection film proposed in JP-A-6-160602 has a five-layer structure of LMLML from the substrate side. MLMLML from the substrate side, and a seven-layer structure LMLMLML from the substrate side. Also,
The anti-reflection film proposed in JP-A-7-244202 has a five-layer structure of MHMHL from the substrate side, and the anti-reflection film proposed in JP-A-7-244203 is LHLHL from the substrate side. It has a five-layer configuration.

[0004]

In the antireflection film having the above-mentioned laminated structure, the important antireflection band on the short wavelength side is narrow, and the antireflection band on the long wavelength side for alignment light is wide. In consideration of the stability of the characteristics at the time of manufacture, the reverse is more preferable, and it is unsuitable for an optical system that requires a wide antireflection band on the short wavelength side. Not only in a photolithography apparatus, but also in an optical system that requires high-precision positioning, an antireflection film that is effective at two wavelengths, that is, a wavelength for use and a wavelength for alignment is required. For example, in an optical system that uses light having a shorter wavelength to increase the resolution in an optical microscope, a wavelength range of 350 nm to 550 nm and 780 n used for alignment are used.
There is a need for an anti-reflection coating at a wavelength of m.

The present invention has been made in view of such circumstances, and has an antireflection film having an antireflection effect in a wide wavelength range of about 350 nm to 550 nm and also having an antireflection effect on alignment light. The purpose is to provide.

[0006]

In order to achieve the above object, the antireflection film of the first invention comprises, in order from the substrate side, a first layer made of an intermediate refractive index material and a first layer made of a low refractive index material. Two layers, a third layer of an intermediate refractive index material, a fourth layer of a high refractive index material, a fifth layer of a low refractive index material,
And a five-layer structure characterized by satisfying the following conditional expressions (1) to (3) when the central wavelength of the wavelength region to be used is set as the design dominant wavelength. 1.35 <nL <1.48 (1) 1.50 <nM <1.70 (2) 1.90 <nH <2.60 (3) where nL is the refractive index of the low-refractive index material with respect to the design dominant wavelength, and nM is the intermediate value with respect to the design dominant wavelength. The refractive index of the refractive index material, nH: the refractive index of the high refractive index material with respect to the design dominant wavelength.

According to a second aspect of the present invention, there is provided an antireflection film according to the first aspect, further satisfying the following conditional expressions (A1) to (A5). 0.10λ ₀ ≦ n1 ・ d1 ≦ 0.50λ ₀ … (A1) 0.40λ ₀ ≦ n2 ・ d2 ≦ 0.65λ ₀ … (A2) 0.15λ ₀ ≦ n3 ・ d3 ≦ 0.40λ ₀ … (A3) 0.45λ ₀ ≦ n4 D4 ≦ 0.62λ ₀ … (A4) 0.20λ ₀ ≦ n5 d5 ≦ 0.30λ ₀ … (A5) where λ _{0 is the} design dominant wavelength (nm) ni is the refractive index of the i-th layer with respect to the design dominant wavelength λ ₀ (i = 1,2,3,4,
5), di: physical thickness of the i-th layer (i = 1, 2, 3, 4, 5).

The antireflection film of the third invention comprises, in order from the substrate side, a first layer made of a low refractive index material, a second layer made of an intermediate refractive index material, and a third layer made of a low refractive index material. , A fourth layer made of an intermediate refractive index material, a fifth layer made of a high refractive index material, and a sixth layer made of a low refractive index material. Wherein the wavelengths satisfy the following conditional expressions (1) to (3):
It has a layer structure. 1.35 <nL <1.48 (1) 1.50 <nM <1.70 (2) 1.90 <nH <2.60 (3) where nL is the refractive index of the low-refractive index material with respect to the design dominant wavelength, and nM is the intermediate value with respect to the design dominant wavelength. The refractive index of the refractive index material, nH: the refractive index of the high refractive index material with respect to the design dominant wavelength.

According to a fourth aspect of the present invention, in the antireflection film according to the third aspect of the present invention, the following conditional expressions (B1) to (B6) are further satisfied. 0.35λ ₀ ≦ n1 ・ d1 ≦ 0.63λ ₀ … (B1) 0.36λ ₀ ≦ n2 ・ d2 ≦ 0.58λ ₀ … (B2) 0.37λ ₀ ≦ n3 ・ d3 ≦ 0.68λ ₀ … (B3) 0.15λ ₀ ≦ n4・ D4 ≦ 0.38λ ₀ … (B4) 0.45λ ₀ ≦ n5 ・ d5 ≦ 0.59λ ₀ … (B5) 0.20λ ₀ ≦ n6 ・ d6 ≦ 0.28λ ₀ … (B6) where λ _{0 is the} design dominant wavelength (nm ) ni: refractive index of the i-th layer with respect to the design dominant wavelength λ ₀ (i = 1,2,3,4,
5,6) di: Physical thickness of the i-th layer (i = 1, 2, 3, 4, 5, 6).

According to a fifth aspect of the present invention, there is provided an antireflection film comprising, in order from the substrate side, a first layer made of an intermediate refractive index material, a second layer made of a low refractive index material, and a third layer made of an intermediate refractive index material. A fourth layer made of a low refractive index material, a fifth layer made of an intermediate refractive index material, a sixth layer made of a high refractive index material, and a seventh layer made of a low refractive index material. , When the center wavelength of the wavelength region to be used is the design dominant wavelength, the following conditional expression (1)
It has a seven-layer structure characterized by satisfying (3). 1.35 <nL <1.48 (1) 1.50 <nM <1.70 (2) 1.90 <nH <2.60 (3) where nL is the refractive index of the low-refractive index material with respect to the design dominant wavelength, and nM is the intermediate value with respect to the design dominant wavelength. The refractive index of the refractive index material, nH: the refractive index of the high refractive index material with respect to the design dominant wavelength.

An antireflection film according to a sixth aspect of the present invention is characterized in that, in the configuration of the fifth aspect, the following conditional expressions (C1) to (C7) are further satisfied. 0.20λ ₀ ≦ n1 ・ d1 ≦ 0.63λ ₀ … (C1) 0.36λ ₀ ≦ n2 ・ d2 ≦ 0.58λ ₀ … (C2) 0.37λ ₀ ≦ n3 ・ d3 ≦ 0.70λ ₀ … (C3) 0.15λ ₀ ≦ n4・ D4 ≦ 0.38λ ₀ … (C4) 0.20λ ₀ ≦ n5 ・ d5 ≦ 0.34λ ₀ … (C5) 0.15λ ₀ ≦ n6 ・ d6 ≦ 0.29λ ₀ … (C6) 0.20λ ₀ ≦ n7 ・ d7 ≦ 0.28λ ₀ … (C7) where λ ₀ : design dominant wavelength (nm) ni: refractive index of the i-th layer with respect to design dominant wavelength λ ₀ (i = 1,2,3,4,
5,6,7), di: Physical thickness of the i-th layer (i = 1,2,3,4,5,6,7).

An antireflection film according to a seventh aspect of the present invention is the antireflection film according to any one of the first to sixth aspects, wherein:
Made of a material with a refractive index of 1.44 to 1.84 for the design dominant wavelength,
The low refractive index material is MgF ₂ , SiO ₂ , SiO, BaF ₂ , LiF, Sr
F ₂ , AlF ₃ , cryolite (Na ₃ AlF ₆ ), thiolite (Na ₅ Al ₃
F ₁₄ ) or a mixture or compound composed of two or more of these as a main component, wherein the intermediate refractive index material is Al ₂ O ₃ , LaF
_3, NdF _3, YF _3, or as a main component a mixture or compound of two or more of these, the high refractive index material, Hf
The main component is O ₂ , Sc ₂ O ₃ , Y ₂ O ₃ , ZrO ₂ , or a mixture or compound composed of two or more thereof.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an antireflection film embodying the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing a laminated structure of a five-layered antireflection film, FIG. 2 is a sectional view showing a laminated structure of a six-layered antireflection film, and FIG. The structure is shown in cross section.

The antireflection film shown in FIG. 1 comprises, in order from the substrate (L0) side, a first layer (L1) made of an intermediate refractive index material, a second layer (L2) made of a low refractive index material, and an intermediate refractive index material. Has a five-layer structure in which a third layer (L3) made of a high refractive index material, a fourth layer (L4) made of a high refractive index material, and a fifth layer (L5) made of a low refractive index material are stacked. . Assuming that a layer made of a high-refractive-index material is H, a layer made of a medium-refractive-index material is M, and a layer made of a low-refractive-index material is L, the MLMHL has a five-layer structure from the substrate (L0) side.

In the antireflection film having a five-layer structure shown in FIG. 1, when the center wavelength of a wavelength region to be used (for example, 350 nm to 550 nm) is set as a design main wavelength, the following conditional expressions (1) to (3) are satisfied. It is desirable to be satisfied. 1.35 <nL <1.48 (1) 1.50 <nM <1.70 (2) 1.90 <nH <2.60 (3) where nL is the refractive index of the low-refractive index material with respect to the design dominant wavelength, and nM is the intermediate value with respect to the design dominant wavelength. The refractive index of the refractive index material, nH: the refractive index of the high refractive index material with respect to the design dominant wavelength.

In the antireflection film having a five-layer structure shown in FIG. 1, it is preferable that the following conditional expressions (A1) to (A5) are further satisfied. 0.10λ ₀ ≦ n1 ・ d1 ≦ 0.50λ ₀ … (A1) 0.40λ ₀ ≦ n2 ・ d2 ≦ 0.65λ ₀ … (A2) 0.15λ ₀ ≦ n3 ・ d3 ≦ 0.40λ ₀ … (A3) 0.45λ ₀ ≦ n4 D4 ≦ 0.62λ ₀ … (A4) 0.20λ ₀ ≦ n5 d5 ≦ 0.30λ ₀ … (A5) where λ _{0 is the} design dominant wavelength ni: the refractive index of the i-th layer with respect to the design dominant wavelength λ ₀ (i = 1,2,3,4,
5), di: physical thickness of the i-th layer (i = 1, 2, 3, 4, 5).

The antireflection film shown in FIG. 2 includes, in order from the substrate (L0) side, a first layer (L1) made of a low refractive index material, a second layer (L2) made of an intermediate refractive index material, and a low refractive index material. The third made of material
A layer (L3), a fourth layer (L4) made of an intermediate refractive index material, a fifth layer (L5) made of a high refractive index material, and a sixth layer (L6) made of a low refractive index material It has a six-layer structure of LMLMHL. It is desirable that the antireflection film having the six-layer structure also satisfies the conditional expressions (1) to (3).

The antireflection film having a six-layer structure shown in FIG. 2 preferably further satisfies the following conditional expressions (B1) to (B6). 0.35λ ₀ ≦ n1 ・ d1 ≦ 0.63λ ₀ … (B1) 0.36λ ₀ ≦ n2 ・ d2 ≦ 0.58λ ₀ … (B2) 0.37λ ₀ ≦ n3 ・ d3 ≦ 0.68λ ₀ … (B3) 0.15λ ₀ ≦ n4・ D4 ≦ 0.38λ ₀ … (B4) 0.45λ ₀ ≦ n5 ・ d5 ≦ 0.59λ ₀ … (B5) 0.20λ ₀ ≦ n6 ・ d6 ≦ 0.28λ ₀ … (B6) where ni is the design dominant wavelength λ ₀ Refractive index of i-th layer (i = 1,2,3,4,
5,6) di: Physical thickness of the i-th layer (i = 1, 2, 3, 4, 5, 6).

The antireflection film shown in FIG. 3 includes, in order from the substrate (L0) side, a first layer (L1) made of an intermediate refractive index material, a second layer (L2) made of a low refractive index material, and an intermediate refractive index material. A third layer (L3) made of a low refractive index material, a fourth layer (L4) made of a low refractive index material, a fifth layer (L5) made of a medium refractive index material, and a sixth layer (L5) made of a high refractive index material. L6), a seventh layer (L7) made of a low refractive index material,
Are stacked in a seven-layer structure of MLMLMHL. In the seven-layer antireflection film, the conditional expressions (1) to
It is desirable to satisfy (3).

The antireflection film having a seven-layer structure shown in FIG. 3 preferably further satisfies the following conditional expressions (C1) to (C7). 0.20λ ₀ ≦ n1 ・ d1 ≦ 0.63λ ₀ … (C1) 0.36λ ₀ ≦ n2 ・ d2 ≦ 0.58λ ₀ … (C2) 0.37λ ₀ ≦ n3 ・ d3 ≦ 0.70λ ₀ … (C3) 0.15λ ₀ ≦ n4・ D4 ≦ 0.38λ ₀ … (C4) 0.20λ ₀ ≦ n5 ・ d5 ≦ 0.34λ ₀ … (C5) 0.15λ ₀ ≦ n6 ・ d6 ≦ 0.29λ ₀ … (C6) 0.20λ ₀ ≦ n7 ・ d7 ≦ 0.28λ ₀ … (C7) where ni: refractive index of the i-th layer with respect to the design dominant wavelength λ ₀ (i = 1, 2, 3, 4,
5,6,7), di: Physical thickness of the i-th layer (i = 1,2,3,4,5,6,7).

Antireflection of 5 to 7 layers constitution shown in FIGS.
In the film, the substrate (L0) has a design dominant wavelength λ.₀Succumb to
Made of a material with a refractive index of 1.44 to 1.84, the low refractive index material is Mg
F_Two, SiO _Two, SiO, BaF_Two, LiF, SrF_Two, AlF_Three, Cliolite
(Na_ThreeAlF₆), Thiolite (Na_FiveAl_ThreeF ₁₄) Or these two
The mixture or compound consisting of
The refractive index material is Al_TwoO_Three, LaF_Three, NdF_Three, YF_ThreeOr these
A mixture or compound composed of two or more kinds as a main component,
High refractive index material is HfO_Two, Sc_TwoO_Three, Y_TwoO_Three, ZrO_TwoOr this
A mixture or compound consisting of two or more of these
It is desirable to do.

By forming the antireflection film of 5 to 7 layers shown in FIGS. 1 to 3 from a material satisfying conditional expressions (1) to (3), the antireflection effect can be obtained in a wide wavelength range of about 350 nm to 550 nm. And an antireflection effect can be obtained for alignment light having a wavelength of 720 nm, 780 nm, 810 nm, or the like. And
By setting the optical film thickness nidi of each layer so as to satisfy the conditional expressions (A1) to (A5), (B1) to (B6) or (C1) to (C7),
Antireflection in a two-wavelength region where the antireflection region on the short wavelength side is wide can be more effectively performed. If such an antireflection film having a wide antireflection region on the short wavelength side is used for an optical system such as an optical microscope, light having a shorter wavelength can be used, so that the resolving power can be improved.

[0023]

EXAMPLES An antireflection film embodying the present invention will be more specifically described below with reference to its optical configuration and the like. Examples 1 to 3 having a five-layer structure, Comparative Examples 1 to 3, and Examples 4 to 6 having a six-layer structure, Comparative Examples 4, and Examples 7 to 9 having a seven-layer structure and Comparative Example 5
The optical configuration of the antireflection film is shown in Tables 1 to 14, respectively,
FIGS. 4 to 17 show the spectral reflectance characteristics of the antireflection film (incident angle on the film surface = 0 °).

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

[Table 3]

[0027]

[Table 4]

[0028]

[Table 5]

[0029]

[Table 6]

[0030]

[Table 7]

[0031]

[Table 8]

[0032]

[Table 9]

[0033]

[Table 10]

[0034]

[Table 11]

[0035]

[Table 12]

[0036]

[Table 13]

[0037]

[Table 14]

[0038]

As described above, according to the present invention, 35
It is possible to realize an antireflection film having an antireflection effect in a wide wavelength range of about 0 nm to 550 nm and also having an antireflection effect on alignment light. If such an anti-reflection film having a wide anti-reflection region on the short wavelength side is used for the optical system of the optical microscope, light having a shorter wavelength can be used, so that the resolving power can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a laminated structure of a five-layer antireflection film according to the present invention.

FIG. 2 is a cross-sectional view schematically showing a laminated structure of a six-layer antireflection film according to the present invention.

FIG. 3 is a sectional view schematically showing a laminated structure of a seven-layer antireflection film according to the present invention.

FIG. 4 is a graph showing the spectral reflectance characteristics of Example 1.

FIG. 5 is a graph showing the spectral reflectance characteristics of Example 2.

FIG. 6 is a graph showing spectral reflectance characteristics of Example 3.

FIG. 7 is a graph showing the spectral reflectance characteristics of Comparative Example 1.

FIG. 8 is a graph showing the spectral reflectance characteristics of Comparative Example 2.

FIG. 9 is a graph showing the spectral reflectance characteristics of Comparative Example 3.

FIG. 10 is a graph showing spectral reflectance characteristics of Example 4.

FIG. 11 is a graph showing the spectral reflectance characteristics of Example 5.

FIG. 12 is a graph showing spectral reflectance characteristics of Example 6.

FIG. 13 is a graph showing the spectral reflectance characteristics of Comparative Example 4.

FIG. 14 is a graph showing the spectral reflectance characteristics of Example 7.

FIG. 15 is a graph showing the spectral reflectance characteristics of Example 8.

FIG. 16 is a graph showing the spectral reflectance characteristics of Example 9.

FIG. 17 is a graph showing the spectral reflectance characteristics of Comparative Example 5.

[Explanation of symbols]

 L0 ... Substrate L1 ... First layer L2 ... Second layer L3 ... Third layer L4 ... Fourth layer L5 ... Fifth layer L6 ... Sixth layer L7 ... Seventh layer

 ──────────────────────────────────────────────────の Continued on the front page F term (reference) 2K009 AA08 AA09 CC03 CC06 4F100 AA05C AA05E AA17B AA17C AA17D AA17E AA18C AA18E AA19B AA19D AA20C AA20E AA33C AA33E AT00A BA05 BA07B18A JE10 4G059 AA11 AC04 EA01 EA05 EA09 EA16 GA02 GA04 GA12

Claims (7)

[Claims] A first layer made of an intermediate refractive index material, a second layer made of a low refractive index material, a third layer made of an intermediate refractive index material, and a first layer made of a high refractive index material. Four layers and a fifth layer made of a low refractive index material,
A five-layer antireflection film characterized by satisfying the following conditional expressions (1) to (3) when a center wavelength of a wavelength region to be used is a design dominant wavelength: 1.35 <nL <1.48 (1) 1.50 <nM <1.70 (2) 1.90 <nH <2.60 (3) where nL is the refractive index of the low refractive index material relative to the design dominant wavelength, nM is the refractive index of the intermediate refractive index material relative to the design dominant wavelength, nH is The refractive index of the high refractive index material with respect to the design dominant wavelength. 2. The antireflection film according to claim 1, further satisfying the following conditional expressions (A1) to (A5): 0.10λ ₀ ≦ n1 · d1 ≦ 0.50λ ₀ (A1) 0.40 λ ₀ ≦ n2 ・ d2 ≦ 0.65λ ₀ … (A2) 0.15λ ₀ ≦ n3 ・ d3 ≦ 0.40λ ₀ … (A3) 0.45λ ₀ ≦ n4 ・ d4 ≦ 0.62λ ₀ … (A4) 0.20λ ₀ ≦ n5 ・d5 ≦ 0.30λ ₀ (A5) where λ _{0 is the} design dominant wavelength (nm) ni: the refractive index of the i-th layer with respect to the design dominant wavelength λ ₀ (i = 1,2,3,4,
5), di: physical thickness of the i-th layer (i = 1, 2, 3, 4, 5). 3. A first layer made of a low-refractive-index material, a second layer made of an intermediate-refractive-index material, a third layer made of a low-refractive-index material, and a first layer made of an intermediate-refractive-index material. The following conditional expression is obtained by laminating four layers, a fifth layer made of a high refractive index material, and a sixth layer made of a low refractive index material, and setting a center wavelength of a wavelength region to be used as a design dominant wavelength. 1.35 <nL <1.48 (1) 1.50 <nM <1.70 (2) 1.90 <nH <2.60 (3) Here, nL is the refractive index of the low refractive index material with respect to the design dominant wavelength, nM is the refractive index of the intermediate refractive index material with respect to the design dominant wavelength, and nH is the refractive index of the high refractive index material with respect to the design dominant wavelength. 4. The antireflection film according to claim 3, further satisfying the following conditional expressions (B1) to (B6): 0.35λ ₀ ≦ n1 · d1 ≦ 0.63λ ₀ (B1) 0.36 λ ₀ ≦ n2 ・ d2 ≦ 0.58λ ₀ … (B2) 0.37λ ₀ ≦ n3 ・ d3 ≦ 0.68λ ₀ … (B3) 0.15λ ₀ ≦ n4 ・ d4 ≦ 0.38λ ₀ … (B4) 0.45λ ₀ ≦ n5 ・d5 ≦ 0.59λ ₀ … (B5) 0.20λ ₀ ≦ n6 · d6 ≦ 0.28λ ₀ … (B6) where λ ₀ : design dominant wavelength (nm) ni: refractive index of the i-th layer with respect to design dominant wavelength λ ₀ ( i = 1,2,3,4,
5,6) di: Physical thickness of the i-th layer (i = 1, 2, 3, 4, 5, 6). 5. A first layer made of an intermediate-refractive-index material, a second layer made of a low-refractive-index material, a third layer made of an intermediate-refractive-index material, and a first layer made of a low-refractive-index material, in this order from the substrate side. A central layer of a wavelength region to be used, which is formed by laminating four layers, a fifth layer made of an intermediate refractive index material, a sixth layer made of a high refractive index material, and a seventh layer made of a low refractive index material. Where the following formulas (1) to (3) are satisfied when is the design dominant wavelength: 1.35 <nL <1.48 (1) 1.50 <nM <1.70 (1) 2) 1.90 <nH <2.60 (3) where nL is the refractive index of the low refractive index material relative to the design dominant wavelength, nM is the refractive index of the intermediate refractive index material relative to the design dominant wavelength, and nH is the high refractive index relative to the design dominant wavelength. The refractive index of the material, 6. The antireflection film according to claim 5, further satisfying the following conditional expressions (C1) to (C7): 0.20λ ₀ ≦ n1 · d1 ≦ 0.63λ ₀ (C1) 0.36 λ ₀ ≦ n2 ・ d2 ≦ 0.58λ ₀ … (C2) 0.37λ ₀ ≦ n3 ・ d3 ≦ 0.70λ ₀ … (C3) 0.15λ ₀ ≦ n4 ・ d4 ≦ 0.38λ ₀ … (C4) 0.20λ ₀ ≦ n5 ・d5 ≦ 0.34λ ₀ … (C5) 0.15λ ₀ ≦ n6 · d6 ≦ 0.29λ ₀ … (C6) 0.20λ ₀ ≦ n7 · d7 ≦ 0.28λ ₀ … (C7) where λ ₀ : Design dominant wavelength (nm) ni: refractive index of the i-th layer with respect to the design dominant wavelength λ ₀ (i = 1, 2, 3, 4,
5,6,7), di: Physical thickness of the i-th layer (i = 1,2,3,4,5,6,7). 7. The method according to claim 1, wherein the substrate has a refractive index with respect to a design dominant wavelength.
1.44 to 1.84 material, wherein the low refractive index material is Mg
F ₂ , SiO ₂ , SiO, BaF ₂ , LiF, SrF ₂ , AlF ₃ , cryolite
(Na ₃ AlF ₆ ), thiolite (Na ₅ Al ₃ F ₁₄ ), or a mixture or compound of two or more of these as a main component, wherein the intermediate refractive index material is Al ₂ O ₃ , LaF ₃ , NdF ₃ , YF ₃ , or a mixture or compound composed of two or more thereof as a main component, wherein the high refractive index material is HfO ₂ , Sc ₂ O ₃ , Y ₂ O ₃ , ZrO ₂ ,
The antireflection film according to any one of claims 1 to 6, wherein a mixture or a compound composed of two or more of these components is used as a main component.