JP2002156507A - Antireflection film and optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antireflection film and an optical element with low reflectance with respect to wavelength regions in the vicinity of 365 nm or 436 nm and with broad band, effective and excellent antireflection characteristics. SOLUTION: The antireflection film is a multilayer film with four-layered structure formed on a substrate. A first layer and a third layer numbered successively from the substrate side are high refractive index layers with 2.10-2.40 refractive index in 320-450 nm wavelength range. A second layer and a fourth layer are low refractive index layers with 1.42-1.50 refractive index in the same range. Denoting optical film thickness of the first layer to the fourth layer as d1-d4 respectively and the wavelength in use in the same wavelength range as λ0, inequalities 0.05λ0<=d1<=0.07λ0, 0.05λ0<=d2<=0.11λ0, 0.50λ0<=d3<=0.56λ0 and 0.24λ0<=d4<=0.26λ0 hold. The antireflection film optionally has the construction with an exchange of the second layer for a medium refractive index layer. The optical element consists of the antireflection film formed on the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antireflection film coated on the surface of an optical element having optical glass or the like as a base, and an optical element using the same. The antireflection film of the present invention is provided on an optical member such as a lens used for a projection optical system and an illumination optical system of a projection exposure apparatus (stepper or the like) using i-line for lithography.
It is particularly suitable for an anti-reflection film having an anti-reflection effect on ultraviolet light near 365 nm or an anti-reflection film having an anti-reflection effect on ultraviolet light near 436 nm used for g-line.

[0002]

2. Description of the Related Art Conventionally, an oxide and a fluoride film are used as an antireflection film in a region of ultraviolet light and visible light having a wavelength of 400 nm or less (Japanese Patent No. 2586527, Patent No. 25).
No. 86509) is known. Further, an antireflection film comprising a six-layer film having an oxide film structure (Japanese Patent Laid-Open No. 7-26100)
No. 2) is also known.

[0003]

However, the prior art has a problem that the antireflection bandwidth is narrow.

The present invention provides an antireflection film having an excellent antireflection effect in a wide band including ultraviolet light near 365 nm (i-line) or around 436 nm (g-line).

[0005]

The present invention relates to a multilayer film having a four-layer structure formed on a substrate, wherein the first and third layers counted from the substrate side have wavelengths of 320 nm to 450 nm.
m is a high refractive index layer having a refractive index of 2.10 or more and 2.40 or less, and the second layer and the fourth layer have a wavelength of 3
The refractive index in the range of 20 nm to 450 nm is 1.
A low refractive index layer of 42 or more and 1.50 or less, and
The optical thicknesses of the first to fourth layers are d1 and d, respectively.
2, d3 and d4, from a wavelength of 320 nm to 450
When the wavelength to be used in the range of nm is expressed as λ0, 0.05λ0 ≦ d1 ≦ 0.07λ0 0.05λ0 ≦ d2 ≦ 0.11λ0 0.50λ0 ≦ d3 ≦ 0.56λ0 0.24λ0 ≦ d4 ≦ 0.26λ0 Is an antireflection film.

Here, (optical film thickness) = (refractive index) × (geometric film thickness). Within this optical film thickness range, this antireflection film
The refractive index of the substrate is 1.45 in the range of 0 nm to 450 nm.
From 1.94 to 1.94 is preferable from the viewpoint of antireflection characteristics.

[0007] The material of the high refractive index layer is Ta._TwoO_FiveThe main
And the material of the low refractive index layer is SiO _TwoThe main component
Are each preferred.

The present invention also relates to a multilayer film having a four-layer structure formed on a substrate, wherein the first and third layers counted from the substrate side have refractive indices in a wavelength range of 320 nm to 450 nm. A high-refractive-index layer having a wavelength of from 320 nm to 450 nm;
Is a middle refractive index layer having a refractive index of 1.55 or more and 1.65 or less, and the fourth layer has a wavelength of 320 nm to 4 nm.
Refractive index in the range of 50 nm is not less than 1.42 and 1.50
A low refractive index layer that is:
The optical thicknesses of the layers are d1, d2, d3 and d4, respectively.
When the wavelength to be used in the range of 320 nm to 450 nm is represented as λ0, 0.04λ0 ≦ d1 ≦ 0.06λ0 0.06λ0 ≦ d2 ≦ 0.14λ0 0.48λ0 ≦ d3 ≦ 0.55λ0 0.24λ0 ≦ d4 ≦ 0.26λ0.

In the above-mentioned optical film thickness range, it has been found that a high-performance anti-reflection film having a large width of the anti-reflection band and a low reflectance in the reflection optical characteristics determined by the combination of the refractive index and the optical film thickness of each layer. .

The material of the high refractive index layer is mainly composed of Ta ₂ O ₅ , the material of the medium refractive index layer is mainly composed of Al ₂ O ₃ , and the material of the low refractive index layer is SiO _2. Is preferably used as a main component.

The term "main component" means that the substance is mainly composed of at least an optical property of the material regarded as the main component to such an extent that it can be regarded as the same as the pure substance. In addition, as a material of each layer, if there is another material having the same refractive index, one or more layers can be replaced with the material.

As the high refractive index layer, TiO ₂ , Nb ₂ O ₅ or the like can be used. Alternatively, MgO or the like can be used as the low refractive index layer.

According to the optical element of the present invention, it is preferable that the material of the lens or the like serving as the base on which the antireflection film is formed is quartz or optical glass in consideration of the refractive index.

The antireflection film of the present invention preferably has a large antireflection bandwidth.

In this specification, the term "substrate" refers to a base member (lens body, prism body, transparent plate, etc.) on which an antireflection film is to be formed, and "optical element" refers to an optical system. The constituent members, such as a lens, a prism, and a parallel flat plate, are intended. In addition, this base is 320 n
Refractive index 1.45 to 1.94 in the range of m to 450 nm
It is preferable from the viewpoint of anti-reflection properties when the ratio is within the range.

[0016]

EXAMPLE 1 An antireflection film of the present embodiment is used on a substrate made of synthetic quartz (in this case, a sample) to reflect light near a light source wavelength of 365 nm (i-line) of an exposure apparatus. An anti-reflection film having an anti-reflection film effect was produced using the film configuration and film thickness shown in Table 1 using a vacuum deposition method. Where λ0
= 365 nm. FIG. 1 shows a schematic diagram of the film configuration. FIG. 2 shows a reflection characteristic diagram of the manufactured antireflection film in a wavelength range of 300 nm to 500 nm. It can be seen that the anti-reflection characteristics are low, with a reflectance of 0.3% or less at 365 nm and a wavelength width of 190% with a reflectance of 0.5% at a wavelength of 190 nm.

The refractive index is a value measured at a wavelength of 365 nm. Hereinafter, the measurement is performed using either a spectrometer or an ellipsometer.

[0018]

[Table 1]

[Example 2] A light source wavelength of 365 nm (i) of an exposure apparatus to which the antireflection film of the present example is applied on a BK7 (BK7 is a trade name of Shot) glass substrate.
An anti-reflection film having an anti-reflection film effect on light near (line) was manufactured by a sputtering method with the film configuration and film thickness shown in Table 2. Here, λ0 = 365 nm. FIG. 3 shows the results of measuring the reflection characteristics of the manufactured antireflection film in the wavelength range of 300 nm to 500 nm. 0.3 reflectance at 365 nm
% Or less, 0.5% reflectivity, wavelength width 190 nm, low reflectivity over a wide bandwidth, and good antireflection characteristics.

The refractive index is a value measured at a wavelength of 365 nm.

[0021]

[Table 2]

[Embodiment 3] The light source wavelength of the exposure apparatus to which the antireflection film of this embodiment is used is 365 nm (i.e.
An anti-reflection film having an anti-reflection film effect on light in the vicinity of (line) was produced by the vacuum deposition method with the film configuration and film thickness shown in Table 3. Here, λ0 = 365 nm. FIG. 4 shows a reflection characteristic diagram of the manufactured antireflection film in a wavelength range of 300 nm to 500 nm.

At 365 nm, reflectance is 0.2% or less, 0.5
It can be seen that the antireflection characteristics have a low reflectance over a wide bandwidth of a% reflectance wavelength width of 160 nm.

The refractive index is a value measured at a wavelength of 365 nm.

[0025]

[Table 3]

[Embodiment 4] A light source near a light source wavelength of 365 nm (i-line) of an exposure apparatus to which the antireflection film of the present embodiment is applied on an SF6 (SF6 is a trade name of Shot Corporation) substrate. An anti-reflection film having an anti-reflection film effect was produced by a sputtering method with the film configuration and film thickness shown in Table 4. Here, λ0 = 365 nm. FIG. 5 shows the results of measuring the reflection characteristics of the manufactured antireflection film in the wavelength range of 300 nm to 500 nm. It was found that the reflectance was 0.2% or less at 365 nm, the reflectance was 0.5%, and the wavelength width was 150 nm.

The refractive index is a value measured at a wavelength of 365 nm.

[0028]

[Table 4]

Example 5 An antireflection film having an antireflection film effect on light near a light source wavelength of 365 nm (i-line) of an exposure apparatus to which the antireflection film of this example is used on a synthetic quartz substrate. The film was manufactured using the film configuration and film thickness shown in Table 5 using a vacuum deposition method. Here, λ0 = 365 nm.

FIG. 6 shows a reflection characteristic diagram of the manufactured antireflection film in a wavelength range of 300 nm to 500 nm. 365
0.3% or less in nm, 0.5% reflectance wavelength width 19
It can be seen that the antireflection characteristics are low and have a low reflectance over a wide bandwidth of 0 nm.

The refractive index is a value measured at a wavelength of 365 nm.

[0032]

[Table 5]

[Embodiment 6] An anti-reflection film having an anti-reflection film effect on light having a light source wavelength near 365 nm (i-line) of an exposure apparatus to which the anti-reflection film of this embodiment is used on a BK7 glass substrate. The film was manufactured by the sputtering method with the film configuration and the film thickness shown in Table 6. Here, λ0 = 365 nm. Wavelength of 300nm to 500n of manufactured anti-reflection film
FIG. 7 shows the measurement results of the reflection characteristics in the range of m. 36
0.3% or less reflectance at 5 nm, 0.5% reflectance wavelength width 1
It was found that the film had a low reflectance over a wide bandwidth of 80 nm and good antireflection characteristics.

The refractive index is a value measured at a wavelength of 365 nm.

[0035]

[Table 6]

[Embodiment 7] The light source wavelength of an exposure apparatus to which the antireflection film of this embodiment is used is 365 nm (i.e.
An anti-reflection film having an anti-reflection film effect on light in the vicinity of (line) was manufactured by a vacuum deposition method with the film configuration and film thickness shown in Table 7. Here, λ0 = 365 nm. FIG. 8 shows a reflection characteristic diagram of the manufactured antireflection film in a wavelength range of 300 nm to 500 nm.

At 365 nm, the reflectance is 0.2% or less,
It can be seen that the film has good antireflection characteristics with a low reflectance over a wide bandwidth of% reflectance wavelength width of 150 nm.

The refractive index is a value measured at a wavelength of 365 nm.

[0039]

[Table 7]

[Embodiment 8] The light having a light source wavelength near 365 nm (i-line) of an exposure apparatus to which the antireflection film of this embodiment is used is coated on an SF6 substrate (SF6 is a trade name of Shot Corporation). An anti-reflection film having an anti-reflection film effect was produced by a sputtering method with the film configuration and thickness shown in Table 8. Here, λ0 = 365 nm. FIG. 9 shows the results of measuring the reflection characteristics of the manufactured antireflection film in the wavelength range of 300 nm to 500 nm. It was found that the reflectance was 0.2% or less at 365 nm, the reflectance was 0.5%, and the wavelength width was 150 nm.

The refractive index is a value measured at a wavelength of 365 nm.

[0042]

[Table 8]

Embodiment 9 A light source wavelength of 436 nm (g) of an exposure apparatus to which the antireflection film of this embodiment is applied on a BK7 (BK7 is a trade name of Shot) glass substrate.
An anti-reflection film having an anti-reflection film effect on light near (line) was produced by a sputtering method with the film configuration and film thickness shown in Table 9. Here, λ0 = 436 nm. FIG. 10 shows the results of measuring the reflection characteristics of the manufactured antireflection film in the wavelength range of 300 nm to 650 nm. The reflectance is 0.4 at 436 nm.
The reflectance was 4% or less, the reflectance was 0.5%, and the wavelength width was 250 nm.

The refractive index is a value measured at a wavelength of 436 nm.

[0045]

[Table 9]

[Embodiment 10] A light source wavelength of 436 nm of an exposure apparatus to which the antireflection film of this embodiment is applied on a BK7 (BK7 is a trade name of Shot Company) glass substrate.
An anti-reflection film having an anti-reflection film effect on light near (g line) was produced by the sputtering method with the film configuration and film thickness shown in Table 10. Here, λ0 = 436 nm. FIG. 11 shows the results of measuring the reflection characteristics of the manufactured antireflection film in the wavelength range of 300 nm to 650 nm. A reflectance of 0.4% or less at 436 nm, a 0.5% reflectance wavelength width of 250 nm,
It was found that it had low reflectance over a wide bandwidth and good antireflection characteristics.

The refractive index is a value measured at a wavelength of 436 nm.

[0048]

[Table 10]

[0049]

According to the multilayer antireflection film of the present invention, an effective and good broadband antireflection characteristic with extremely low reflection in a wavelength region around 365 nm or around 436 nm is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration example of an antireflection film of the present invention.

FIG. 2 shows a wavelength 3 of an antireflection film on a quartz substrate having a four-layer film structure.
It is a reflection characteristic figure from 00 nm to 500 nm.

FIG. 3 is a reflection characteristic diagram of an antireflection film on a BK7 substrate having a four-layer film structure at a wavelength of 300 nm to 500 nm.

FIG. 4 shows a wavelength 3 of an antireflection film on a SK10 substrate having a four-layer film structure.
It is a reflection characteristic figure from 00 nm to 500 nm.

FIG. 5 is a graph showing reflection characteristics of an antireflection film on a SF6 substrate having a four-layer film structure at a wavelength of 300 nm to 500 nm.

FIG. 6 shows a wavelength 3 of an antireflection film on a quartz substrate having a four-layer film structure.
It is a reflection characteristic figure from 00 nm to 500 nm.

FIG. 7 is a reflection characteristic diagram of an antireflection film on a BK7 substrate having a four-layer film structure at a wavelength of 300 nm to 500 nm.

FIG. 8 is a reflection characteristic diagram of the antireflection film on the SK10 substrate having a four-layer film structure at a wavelength of 300 nm to 500 nm.

FIG. 9 is a graph showing reflection characteristics of an antireflection film on an SF6 substrate having a four-layer film structure at a wavelength of 300 nm to 500 nm.

FIG. 10 is a graph showing the reflection characteristics of an antireflection film on a BK7 substrate having a four-layer film structure at a wavelength of 300 nm to 650 nm.

FIG. 11 is a graph showing reflection characteristics of an antireflection film on a BK7 substrate having a four-layer film structure at a wavelength of 300 nm to 650 nm.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st layer 2 2nd layer 3 3rd layer 4 4th layer 5 Base

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yasuyuki Suzuki 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Ryuji Bilo 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inside (72) Inventor Hidehiro Kanazawa 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2K009 AA07 BB02 BB04 CC03 DD03 DD04 4G059 AA01 AB01 AB09 AB11 AB13 AC04 EA01 EA05 EB03 EB04 GA02 GA04 GA12

Claims (6)

[Claims] 1. A multilayer film having a four-layer structure formed on a substrate, wherein a first layer and a third layer counted from the substrate side in order are:
It is a high refractive index layer having a refractive index in the range of 320 nm to 450 nm of 2.10 to 2.40, and the second and fourth layers have a refractive index of 1.42 or more in the range of 320 nm to 450 nm. 1. The low refractive index layer having a refractive index of 1.50 or less, and the optical thicknesses of the first to fourth layers are represented by d1, d2, d3, and d4, respectively. To λ
When represented as 0, an antireflection film satisfying 0.05λ0 ≦ d1 ≦ 0.07λ0 0.05λ0 ≦ d2 ≦ 0.11λ0 0.50λ0 ≦ d3 ≦ 0.56λ0 0.24λ0 ≦ d4 ≦ 0.26λ0. 2. A multilayer film having a four-layer structure formed on a substrate, wherein a first layer and a third layer counted from the substrate side in order are:
A high refractive index layer having a refractive index in the range of 320 nm to 450 nm of not less than 2.10 and not more than 2.40;
The second layer is a middle refractive index layer having a refractive index of 1.55 or more and 1.65 or less in a wavelength range of 320 nm to 450 nm, and the fourth layer has a refractive index of 1 in a wavelength range of 320 nm to 450 nm. .42 or more and 1.50 or less, and the optical thicknesses of the first to fourth layers are represented by d1, d2, d3 and d4, respectively.
When the target wavelength in the range of 320 nm to 450 nm is represented as λ0, 0.04λ0 ≦ d1 ≦ 0.06λ0 0.06λ0 ≦ d2 ≦ 0.14λ0 0.48λ0 ≦ d3 ≦ 0.55λ0 0.24λ0 ≦ d4 ≦ An antireflection film having a thickness of 0.26λ0 3. The antireflection film according to claim 1, wherein the material of the high refractive index layer is mainly composed of Ta ₂ O ₅ , and the material of the low refractive index layer is mainly composed of SiO ₂ . Material wherein the high refractive index layer is composed mainly of Ta ₂ O _5, the material of the medium refractive index layer is composed mainly of A1 ₂ 0 _3, the material of the low refractive index layer and the main component of SiO ₂ The antireflection film according to claim 2, wherein 5. The antireflection film according to claim 1, wherein the substrate has a refractive index in a range of 320 nm to 450 nm and a refractive index of 1.45 to 1.94. 6. An optical element comprising a base made of quartz or optical glass, wherein the antireflection film according to claim 1 is provided on the surface of the base.