Optical element and apparatus

Abstract

To provide a technique advantageous for achieving an optical element having good optical characteristics.SOLUTION: The optical element comprises a substrate and an optical structure provided on the substrate. The optical structure at least includes at least one oxide layer and at least one fluoride layer. Distance between the one oxide layer and the one fluoride layer is smaller than thickness of the one fluoride layer. When hafnium content in the at least one oxide layer is denoted by [Hf] at%, silicon content in the at least one oxide layer is denoted by [Si] at%, 0.095≤[Si] / ([Si]+[Hf])<0.902 is satisfied.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical element having an oxide layer and a fluoride layer. [Background technology]

[0002] Hafnium oxide has the characteristics of a high refractive index and a high dielectric constant, and its application in optical elements is being considered.

[0003] Patent Document 1 discloses an antireflection coating having a high-refractive index layer and either an intermediate-refractive index layer below the high-refractive index layer or a low-refractive index layer above the high-refractive index layer. Patent Document 1 lists ZrO2, HfO2, Sc2O3, SiO2, Al2O3, NdF3, LaF3, CaF2, CeF3, GdF3, HoF3, ErF3, DyF3, MgO, ThF4, YF3, YbF3, BaF3, and SrF3 as materials for the high-refractive index layer. Patent Document 1 also lists NdF3, LaF3, CaF2, CeF3, GdF3, HoF3, ErF3, DyF3, MgO, ThF4, YF3, YbF3, BaF3, and SrF3 as materials for the intermediate-refractive index layer. In Patent Document 1, MgF2, Na3AlF6, LiF, BaF3, SrF3, CaF2, NaF, and SiO2 are listed as materials for the low refractive index layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-167003 Summary of the Invention [Problem to be solved by the invention]

[0005] The inventors have found that when a fluoride layer is stacked in close proximity to a hafnium oxide layer, light absorption may occur between the hafnium oxide layer and the fluoride layer. Such light absorption reduces the optical properties of the optical element, such as transmittance and reflectance, and is therefore preferably reduced.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a technique that is advantageous in realizing an optical element having good optical characteristics. [Means for solving the problem]

[0007] One embodiment of the present invention, which is a means for solving the above-mentioned problems, provides an optical element comprising a substrate and an optical structure provided on the substrate, wherein the optical structure has at least one oxide layer and at least one fluoride layer, the distance between the one oxide layer and the one fluoride layer is smaller than the thickness of the one fluoride layer, and the optical element satisfies 0.095≦[Si] / ([Si]+[Hf])<0.902, where [Hf] is the hafnium content in the at least one oxide layer and [Si] is the silicon content in the at least one oxide layer. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a technique that is advantageous in realizing an optical element having good optical characteristics. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view of an optical element. [Figure 2] Schematic diagram of a sputtering film formation device. [Figure 3] FIG. [Figure 4] FIG. 1 is a diagram illustrating an interface absorption rate. [Figure 5] FIG. [Figure 6] FIG. [Figure 7] FIG. 4 is a diagram illustrating the transmittance of an anti-reflection film. [Figure 8] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description and drawings, common reference numerals are used to designate components common to multiple drawings. Therefore, common components will be described with mutual reference to multiple drawings, and descriptions of components with common reference numerals will be omitted as appropriate.

[0011] 1(a) to 1(c) are schematic cross-sectional views of an optical element 100 according to this embodiment. The optical element 100 includes a substrate 101 and an optical structure 102 formed on the substrate 101. The optical structure 102 includes at least one oxide layer 102a and at least one fluoride layer 102b. The optical structure 102 can also be called a multilayer film. Here, of the at least one oxide layer 102a and the at least one fluoride layer 102b, attention is focused on one oxide layer 102a and one fluoride layer 102b that are close to each other. The distance between the oxide layer 102a and the fluoride layer 102b of interest is smaller than at least one, preferably both, of the thickness of the oxide layer 102a and the thickness of the fluoride layer 102b of interest. That is, the oxide layer 102a and the fluoride layer 102b are close to each other means that the distance between them is smaller than their thicknesses. Typically, the oxide layer 102a and the fluoride layer 102b of interest are in contact with each other, and the distance between the oxide layer 102a and the fluoride layer 102b of interest is zero. The distance between the oxide layer 102a and the fluoride layer 102b of interest may be less than 10 nm. It is sufficient to have at least one combination in which the oxide layer 102a and the fluoride layer 102b are in contact with each other. The order in which the oxide layer 102a and the fluoride layer 102b are in contact with each other may be such that the fluoride layer 102b is on top of the oxide layer 102a, or such that the oxide layer 102a is on top of the fluoride layer 102b. However, a dielectric layer having a smaller thickness than the oxide layer 102a and the fluoride layer 102b of interest may be interposed between them.

[0012] The oxide layer 102a contains hafnium and silicon. The hafnium content in the oxide layer 102a is [Hf] at %, and the silicon content in the oxide layer 102a is [Si] at %. The oxygen content in the oxide layer 102a is [O] at %. Here, "at %" means "atomic percentage," which is the ratio of the number of specific atoms to the total number of atoms in the target composition. "at %" can also be written as "atomic %" or "atomic %."

[0013] The ratio of silicon to hafnium, which are the main components other than oxygen in the oxide layer 102a, can be expressed as [Si] / ([Si]+[Hf]). This ratio is dimensionless, but expressed as a percentage, it is [Si] / ([Si]+[Hf])×100%. Hereinafter, this [Si] / ([Si]+[Hf]) will be referred to simply as the "silicon ratio," but [Si] / ([Si]+[Hf]) is to be distinguished from the silicon content, which is expressed as [Si] at%. Because the main metal components other than oxygen in the oxide layer 102a are multiple elements (silicon and hafnium), the oxide layer 102a can be referred to as either a composite oxide layer or a metal oxide layer. The fluoride layer 102b may be a simple metal fluoride layer, but may also be a composite fluoride layer in which the main components other than fluorine in the fluoride layer 102b are multiple elements.

[0014] The oxide layer 102a preferably satisfies 0.095≦[Si] / ([Si]+[Hf])<0.902. The oxide layer 102a more preferably satisfies [Si] / ([Si]+[Hf])≧0.219. The oxide layer 102a preferably satisfies [Si] / ([Si]+[Hf])≦0.670, more preferably satisfies [Si] / ([Si]+[Hf])≦0.410. The oxide layer 102a preferably satisfies [Hf]≧3.2 at%, more preferably satisfies [Hf]≧10.5 at%, and even more preferably satisfies [Hf]≧18.6 at%. The oxide layer 102a preferably satisfies [Hf]≦29.2 at%, and more preferably satisfies [Hf]≦24.7 at%. The oxide layer 102a preferably satisfies [Si]≦29.3 at% and more preferably satisfies [Si]≦21.3 at% and further preferably satisfies [Si]≦12.9 at%. The oxide layer 102a preferably satisfies [Si]≧3.1 at% and more preferably satisfies [Si]≧6.9 at%. The oxide layer 102a preferably satisfies 65.0 at%≦[O]≦68 at%.

[0015] The material used as the main component of the oxide layer 102a is an oxide containing hafnium (Hf), silicon (Si), and oxygen (O) as the main components, and Hf x Si y O z It can be expressed as follows. The stoichiometric composition of hafnium oxide is HfO2, where [Hf] = 33.3 at%, [O] = 66.6 at%. The stoichiometric composition of silicon oxide is SiO2, where [Si] = 33.3 at%, and [O] = 66.7 at%. Oxide Hf x Si y O z may have an intermediate composition between HfO2 and SiO2. In the following description, the oxide layer 102a containing hafnium (Hf), silicon (Si), and oxygen (O) as main components may be referred to as a hafnium silicon oxide layer or a silicon-containing hafnium oxide layer.

[0016] The oxide layer 102a, whose main components are silicon (Si), hafnium (Hf), and oxygen (O), will now be described. The contents of elements other than hafnium, silicon, and oxygen contained in the oxide layer 102a are defined as Mat% (M≧0) and Nat% (N≧0). The sum of the hafnium content [Hf] at% in the oxide layer 102a, the silicon content [Si] at% in the oxide layer 102a, and the oxygen content [O] at% in the oxide layer 102a, whose main components are hafnium (Hf), silicon (Si), and oxygen (O), is greater than Mat% and Nat% ([Si] + [Hf] + [O] > M, [Si] + [Hf] + [O] > N). The sum of the hafnium content [Hf] at% in the oxide layer 102a, the silicon content [Si] at% in the oxide layer 102a, and the oxygen content [O] at% in the oxide layer 102a is preferably greater than the sum of the contents of all elements other than hafnium, silicon, and oxygen contained in the oxide layer 102a. The sum of the contents of all elements other than hafnium, silicon, and oxygen contained in the oxide layer 102a is 100 - ([Si] + [Hf] + [O]) at %. Since [Si] + [Hf] + [O] > 100 - ([Si] + [Hf] + [O]), [Si] + [Hf] + [O] > 50.0 at %. In the oxide layer 102a, [Si] + [Hf] + [O] is 100 at % or less. In the oxide layer 102a, [Si] + [Hf] + [O] can be greater than 50.0 at %. As described below, the oxide layer 102a of this embodiment can contain elements other than hafnium, silicon, and oxygen (e.g., Ar, Zr), and therefore [Si] + [Hf] + [O] can be less than 100 at %. For example, when the argon content in the oxide layer 102a is [Ar] at %, M = [Ar], and when the zirconium content in the oxide layer 102a is [Zr] at %, N = [Zr]. Here, the example is given in which two types of elements are used except for hafnium, silicon, and oxygen, but the number of types of elements other than hafnium, silicon, and oxygen may be one, three, or four or more.

[0017] Here, instead of the oxide layer 102a, which is a silicon-containing hafnium oxide layer, consider using a silicon-free hafnium oxide layer. If a fluoride layer is disposed near the silicon-free hafnium oxide layer, the fluorine in the fluoride layer may be taken by the silicon-free hafnium oxide layer, and an altered layer prone to light absorption may form between the silicon-free hafnium oxide layer and the fluoride layer. Therefore, by using a silicon-containing hafnium oxide layer as in this embodiment, the formation of such an altered layer is suppressed. As a result, light absorption between the oxide layer and the fluoride layer is reduced, and an optical element with excellent optical properties can be realized.

[0018] The oxide layer 102a may satisfy 0.9 at%≦[Ar]<2.0 at%. The oxide layer 102a may satisfy 0.01 at%≦[Zr]<0.14 at%. Even if the oxide layer 102a contains elements other than hafnium, silicon, and oxygen (e.g., Ar, Zr), good optical properties can be obtained as long as the concentrations are within this range. The oxide layer 102a preferably satisfies [Hf]+[Si]+[O]≧97.0 at% and more preferably satisfies [Hf]+[Si]+[O]≧98.0 at%. The oxide layer 102a may also satisfy [Hf]+[Si]+[O]≦99.2 at% or [Hf]+[Si]+[O]≦98.7 at%. In the oxide layer 102a of this embodiment, it is not necessary to actively add carbon to the oxide layer 102a. The carbon content [C] at % in the oxide layer 102a is preferably less than 1 at %, and preferably 0.1 at % or less. In the oxide layer 102a of this embodiment, the absorption (extinction coefficient) and refractive index of the oxide layer 102a can be controlled by adding hydrogen to the oxide layer 102a. The hydrogen content [H] in the oxide layer 102a may be 0.1 at % or more, or even 1 at % or more. In this embodiment, it is not necessary to actively introduce hydrogen into the oxide layer 102a. The hydrogen content [H] at % in the oxide layer 102a may be less than 0.1 at %. Furthermore, some of the oxygen in the oxide layer 102a may be replaced by hydrogen, resulting in a hydrogen content [H] at % of less than 15 at %. Furthermore, absorption can be controlled by controlling the crystallinity of the oxide layer 102a. An amorphous oxide layer 102a is preferable to a crystalline oxide layer in terms of reducing absorption.

[0019] The material used for the fluoride layer 102b may be, for example, a material containing magnesium fluoride (MgF2) as a main component, but is not limited to this. For example, fluoride materials such as MgF2, Na3AlF6, LiF, BaF3, SrF3, CaF2, NaF, and AlF3 may also be used, or a mixture or compound of two or more of these materials may also be used.

[0020] The optical structure 102 shown in FIG. 1(a) is formed by alternately stacking multiple oxide layers 102a and multiple fluoride layers 102b. The optical structure 102 shown in FIG. 1(a) has a configuration in which the oxide layers 102a and the fluoride layers 102b are alternately stacked in order from the substrate 101 side, with the fluoride layer 102b being the outermost layer. However, the configuration may be changed depending on the application of the optical element. For example, the fluoride layers 102b and the oxide layers 102a may be alternately stacked in order from the substrate 101 side, or a fluoride layer 102b may be added as the outermost layer thereon. Here, the alternating stacking of first-type layers and second-type layers means that at least one second-type layer is located between two first-type layers, and at least one first-type layer is located between two second-type layers. Therefore, at least two layers are required for the first type of layers and the second type of layers to be alternately stacked. It is not essential that the optical structure 102 have an alternately stacked structure in which only the fluoride layers 102b and the oxide layers 102a are alternately stacked. The optical structure 102 may be composed of only one oxide layer 102a and one fluoride layer 102b. In addition, a protective layer may be provided on the outermost fluoride layer 102b to serve as the outermost layer, a dielectric layer having an intermediate refractive index may be sandwiched between the oxide layer 102a and the fluoride layer 102b, or an adhesive layer may be provided between the substrate 101 and the optical structure 102.

[0021] The optical structure 102 shown in FIGS. 1(b) and 1(c) includes alternately stacked oxide layers 102a and dielectric layers 102c having a refractive index lower than that of the oxide layers 102a. Each of the dielectric layers 102c is, for example, a silicon oxide layer. However, the present invention is not limited to this. The dielectric layers 102c may be oxides, nitrides, or carbides of various metal elements or semimetal elements. For example, the dielectric layers 102c may be aluminum oxide, silicon oxide, or yttrium oxide. Since silicon is a semimetal element, it is a metal component, and aluminum oxide, silicon oxide, and yttrium oxide can be referred to as metal oxide layers. The dielectric layers 102c may be simple oxide layers, or may be composite oxide layers in which the main components other than oxygen in the dielectric layers 102c are multiple elements.

[0022] 1(a), (b), and (c), four oxide layers 102a are shown as the multiple oxide layers 102a. From the top (the side farthest from the substrate 101), they are called the topmost oxide layer 102a, the second-highest oxide layer 102a, the second-lowest oxide layer 102a, and the first-lowest oxide layer 102a.

[0023] In the example shown in FIG. 1(a), four fluoride layers 102b are illustrated as the multiple fluoride layers 102b. Starting from the top (the side farthest from the substrate 101), they are referred to as the topmost fluoride layer 102b, the second-lowest fluoride layer 102b, the second-lowest fluoride layer 102b, and the first-lowest fluoride layer 102b. In the optical structure 102 shown in FIG. 1(a), a fluoride layer 102b is provided adjacent to (in this example, in contact with) each oxide layer 102a. Therefore, since each oxide layer 102a has a fluoride layer 102b adjacent to it, any oxide layer 102a may be focused on. For example, the multiple oxide layers 102a include the first oxide layer 102a from the top and a second-lowest oxide layer 102a that is separate from the first oxide layer 102a from the top. The plurality of fluoride layers 102b include a second fluoride layer 102b from the top of interest and a first fluoride layer 102b from the bottom that is different from the second fluoride layer 102b from the top. The second fluoride layer 102b from the top is located between the first oxide layer 102a and the substrate 101. The second oxide layer 102a from the bottom is located between the second fluoride layer 102b from the top and the substrate 101. The first fluoride layer 102b from the bottom is located between the second oxide layer 102a and the substrate 101.

[0024] In the optical structure 102 shown in FIG. 1(b), the fluoride layer 102b is provided adjacent to (in this example, in contact with) the first oxide layer 102a from the top. Therefore, the first oxide layer 102a and the adjacent fluoride layer 102b are the focus of attention. The optical structure 102 includes the first oxide layer 102a of interest and a second oxide layer 102a that is separate from the first oxide layer 102a from the top. The first oxide layer 102a is located between the fluoride layer 102b and the substrate 101, and the second oxide layer 102a is located between the first oxide layer 102a from the top and the substrate 101. A dielectric layer 102c, which has a lower refractive index than both the first oxide layer 102a and the second oxide layer 102a from the top, is located between the first oxide layer 102a and the second oxide layer 102a from the top. Between the second-from-top oxide layer 102a and the second-from-bottom oxide layer 102a, a dielectric layer 102c having a lower refractive index than the second-from-top oxide layer 102a and the second-from-bottom oxide layer 102a is located. Between the second-from-bottom oxide layer 102a and the substrate 101, the first-from-bottom oxide layer 102a is located. Between the second-from-bottom oxide layer 102a and the first-from-bottom oxide layer 102a, a dielectric layer 102c having a lower refractive index than the second-from-bottom oxide layer 102a and the first-from-bottom oxide layer 102a is located. The first-from-bottom oxide layer 102a is in contact with the substrate 101.

[0025] In the optical structure 102 shown in FIG. 1(c), the fluoride layer 102b is provided adjacent to (in this example, in contact with) the first oxide layer 102a from the bottom. Therefore, it is sufficient to focus on the first oxide layer 102a from the bottom and the fluoride layer 102b adjacent to it. The fluoride layer 102b is provided between the first oxide layer 102a from the bottom and the substrate 101. The fluoride layer 102b is in contact with the substrate 101.

[0026] The substrate 101 can be made of materials such as calcium fluoride crystal, quartz glass, borosilicate crown glass, or other optical glass, resin, or metal. The substrate 101 can have a variety of shapes, such as a flat shape or a shape with a curved surface, depending on the application and type of optical element (for example, a lens, a mirror, a filter, a prism, etc.). For example, the surface of the substrate 101 on the side of the optical structure 102 may be concave or convex, thereby realizing a concave lens, a convex lens, a concave mirror, a convex mirror, etc.

[0027] The high-refractive-index film according to this embodiment is widely applicable to coating optical elements, including lenses, filters, mirrors, prisms, imaging devices (image sensors), and display devices (displays). Furthermore, it can be used in optical devices equipped with optical elements, such as exposure devices, various cameras, and interchangeable lenses. These optical devices may include multiple optical components, including optical elements coated with a film having a configuration in which a hafnium silicon oxide layer and a magnesium fluoride layer are in contact with each other, as well as a holding component (lens barrel) for holding the multiple optical components. By laminating the high-refractive-index film according to embodiment 1 with a low-refractive-index film having a lower refractive index, a high-performance anti-reflection structure or reflective structure can be formed. For example, in an exposure device equipped with an ultraviolet light source, the exposure performance of the exposure device using ultraviolet light can be improved by providing the anti-reflection structure according to embodiment 1 on the lens and / or the reflective structure according to embodiment 1 on the mirror.

[0028] The optical element 100 can be applied to various optical devices. Examples of optical devices equipped with the optical element 100 include camera lenses, telescopes, projectors, exposure devices, and measuring instruments. The optical element 100 is particularly suitable for optical devices equipped with a light source, such as projectors, exposure devices, and measuring instruments. This is because the stacked film 20 of the optical component 30 can be designed to match the wavelength of the light source so that the optical element 100 transmits and / or reflects light from the light source. The light from the light source may be infrared light, visible light, or ultraviolet light. Many fluorides have lower absorption of ultraviolet light than other metal compounds, and are therefore suitable for use when the light source is ultraviolet light.

[0029] FIG. 8 is a schematic diagram of an exposure apparatus as an example of optical apparatus EQP. Optical apparatus 300, which is an exposure apparatus, includes a light source 301, an illumination optical system 302, and a mirror unit 303 consisting of a mirror holder and a mirror. Optical apparatus 300 also includes a reticle stage 305 that supports a reticle 304, a projection optical system 306 that projects the pattern of the reticle 304, and a substrate stage 308 that supports a substrate 307. Exposure light 309 from light source 301 is reflected by a mirror 320 in the illumination optical system and directed to the reticle 304. The exposure light 309 carrying the pattern of the reticle 304 is collected by the projection optical system 306 and projected onto the substrate 307. The pattern formed on the reticle 304 by light source 301 and optical element 100 is projected onto the substrate 307. A photoresist is applied to the substrate 307, and the photoresist is exposed by the exposure light 309. The substrate 307 may be a semiconductor wafer or a glass substrate for an FPD (flat panel display). The exposure light 309 of the exposure tool is typically ultraviolet light. The wavelength of the exposure light 309 is 436 nm for a g-line light source and approximately 365 nm for an i-line light source. The wavelength of the exposure light is approximately 248 nm for a KrF excimer laser light source, approximately 193 nm for an ArF excimer laser light source, and 10 to 20 nm for an EUV (extreme ultraviolet) light source. Here, an example is shown in which the optical element 100 is used for the lenses of the illumination optical system 302 and the projection optical system 306, but the optical element 100 may also be used for the mirror 320. Alternatively, the projection optical system may be composed of a mirror, and the optical element 100 may be used for this mirror. The projection optical system may be a reduced projection type, an equal magnification projection type, or an enlarged projection type. Although a transmissive reticle 304 is shown here as an example, a reflective reticle 304 may also be used. The projection optical system 306 may be a refractive type using a lens, or a reflective type using a mirror. The optical element 100 may be used as a mirror in a reflective reduction projection optical system provided in an exposure apparatus equipped with an EUV light source. [Example]

[0030] A method for manufacturing an optical element 100 (optical component) according to this embodiment, which includes an optical structure 102 having an oxide layer 102a and a fluoride layer 102b in contact with each other, will be described below. In the following description, the oxide layer 102a will be a hafnium silicon oxide layer, and the fluoride layer 102b will be a magnesium fluoride layer. An oxide layer comparable to the oxide layer 102a as a hafnium silicon oxide layer is a hafnium oxide layer or a silicon oxide layer.

[0031] FIG. 2 is a schematic diagram of a sputtering deposition apparatus 200 used to manufacture an optical element. The sputtering deposition apparatus 200 includes a vacuum chamber 201 as an airtight container and an exhaust system 202 for evacuating the vacuum chamber 201. The apparatus also includes an argon gas inlet port 205 and an oxygen gas inlet port 206 so that gases required for deposition can be introduced into the vacuum chamber 201. The vacuum chamber 201 is also provided with a first sputtering target 209, a backing plate 210, and a magnet mechanism 207. The vacuum chamber 201 is also provided with a second sputtering target 211, a backing plate 212, a magnet mechanism 208, and a substrate holding mechanism 213. The substrate 101 of the optical element is held by the substrate holding mechanism 213, and by applying power from power sources 203 and 204, deposition can be performed by a reactive sputtering method.

[0032] To form a hafnium silicon oxide layer, film formation is performed by a reactive sputtering method according to the following procedure. For example, a substrate 101 made of synthetic quartz glass processed into the shape of a predetermined optical element is set. Furthermore, for example, a 3-inch metal hafnium (purity 99.9 wt% or higher) is set as the sputtering target 209, and a 3-inch polycrystalline silicon (boron-doped conductive silicon) is set as the sputtering target 211 in the vacuum chamber 201. At this time, the vertical distance between the target surface and the substrate surface between the substrate 101 and the sputtering targets 209 and 211 is set to, for example, 200 mm. Furthermore, the two targets 209 and 211 are positioned symmetrically with respect to the central axis of the substrate holding mechanism 213, and the distance between the central axis of the substrate holding mechanism 213 and the central axis of the target 209 or 211 is set to, for example, 100 mm. Then, for example, an exhaust system 202 with an exhaust rate of 1500 L / sec is used, and the pressure is set to 6×10 -5 The vacuum chamber 201 is evacuated to a vacuum of approximately 10 Pa. Under this condition, plasma discharge is generated while introducing argon gas through the argon gas inlet port 205 and oxygen gas through the oxygen gas inlet port 206. Specifically, power is applied from power sources 203 and 204 to sputtering targets 209 and 211 to generate plasma discharge, and a hafnium silicon oxide layer is deposited to a thickness of approximately 100 nm on a substrate 101 having a diameter of 30 mm and a thickness of 2 mm, for example. The thickness of each layer is not necessarily limited to approximately 100 nm, but can be appropriately determined depending on the wavelength of light handled by the optical element and the number of layers constituting the optical structure. The thickness of the hafnium silicon oxide layer in the optical element is, for example, 10 to 1000 nm, e.g., 10 to 100 nm. A 1000 nm hafnium silicon oxide layer may be formed by stacking 100 nm thick hafnium silicon oxide layers without any intervening layers. Then, a magnesium fluoride layer is formed on the hafnium silicon oxide layer by a known film formation method to a thickness of about 100 nm, forming a two-layer film. Specific examples and comparative examples will be described below. Since known film formation methods can be used to form the magnesium fluoride layer, a description thereof will be omitted.

[0033] [Examples 1 to 6], [Comparative Examples 1 to 3] Two-layer films consisting of an oxide layer and a fluoride layer are described as optical structures using Examples 1 to 6 and Comparative Examples 1 to 3. An oxide layer is formed as the lower layer of the two-layer film, and a magnesium fluoride (MgF2) layer is formed on top of the oxide layer so as to contact the oxide layer. The oxide layer differs between Examples 1 to 6 and Comparative Examples 1 to 3. The hafnium silicon oxide layers of Examples 1 to 6 and Comparative Example 2, the hafnium oxide layer of Comparative Example 1, and the silicon oxide layer of Comparative Example 3 were all deposited by introducing argon gas at a flow rate of 65 sccm through argon gas inlet port 205. Each Example and Comparative Example was also deposited by introducing oxygen gas at a flow rate ranging from 10 to 16 sccm through oxygen gas inlet port 206. In Examples 1 to 6 and Comparative Example 2, the silicon ratio ([Si] / ([Si] + [Hf])) was adjusted by changing the ratio of the power applied by power sources 203 and 204. The above conditions are merely examples. For example, a hafnium silicon oxide layer may be formed using a single sputtering target material containing hafnium and silicon at a predetermined ratio. To form a film with a different silicon ratio ([Si] / ([Si]+[Hf])), sputtering targets containing different ratios of hafnium and silicon may be prepared. The silicon ratio ([Si] / ([Si]+[Hf])) and refractive index of the hafnium silicon oxide layers of each example and comparative example were evaluated. Furthermore, the optical absorptivity and interface absorptivity of the two-layer film consisting of a hafnium silicon oxide layer and a magnesium fluoride layer were evaluated.

[0034] The content of each element in the film was evaluated by irradiating the hafnium silicon oxide layer with a high-energy ion beam on the order of MeV and using Rutherford backscattering spectrometry (RBS). Using these results, the hafnium content [Hf]at%, silicon content [Si]at%, and oxygen content [O]at% in the hafnium silicon oxide layer were calculated.

[0035] The optical absorptivity and refractive index were evaluated by measuring the transmittance and reflectance at a light incident angle of 5 degrees using an ultraviolet-visible-near-infrared spectrophotometer in the wavelength range of 200 nm to 500 nm.

[0036] The light absorption rate was calculated using the following formula. A(%) = 100 - T(%) - R(%) (Equation 1) Here, A (%) represents the light absorption rate, T (%) represents the transmittance, and R (%) represents the reflectance.

[0037] The refractive index was measured using the optical thin film analysis and design software FilmWizard from Scientific Computing International. TM The calculation was carried out by analysis using

[0038] To evaluate the suitability of optical elements for exposure equipment using ultraviolet wavelengths, such as DUV, i-line, g-line, and h-line, the optical absorptance (%) was evaluated as the average value for wavelengths from 280 to 450 nm. The optical absorptance of a single-layer film of hafnium silicon oxide and magnesium fluoride was calculated by subtracting the optical absorptance of a single-layer film of hafnium silicon oxide and magnesium fluoride from the optical absorptance of a bilayer film consisting of a hafnium silicon oxide layer and a magnesium fluoride layer. This was defined and evaluated as the interfacial absorptance occurring at the interface between the hafnium silicon oxide layer and the magnesium fluoride layer. Therefore, the interfacial absorptance may take a negative value. The refractive index was evaluated using light with a wavelength of 280 nm as the reference. Of course, optical elements for other applications can be evaluated using a wavelength appropriate for that application as the reference. Wavelengths suitable for optical elements are not limited to those in the ultraviolet region; they may also be wavelengths in the visible light region or infrared region.

[0039] To evaluate the adhesion (abrasion resistance) after the two-layer film was formed, Silbon paper was soaked in OHC solvent and the sample was rubbed 50 times with a weight of 500g, and the appearance (presence or absence of film peeling or scratches) was evaluated. Those that showed no peeling or scratches were rated as A, and those that showed peeling or scratches were rated as B.

[0040] To evaluate the environmental durability of the two-layer film, the samples were left in a high-temperature, high-humidity environment (60°C, 90%, 100 hours) and then evaluated for appearance (presence or absence of film peeling or cracking). Samples without peeling or cracking were rated as A, samples with confirmed film cracking were rated as B, and samples with confirmed film peeling were rated as C.

[0041] Table 1 shows the compositions of the hafnium silicon oxide layers (Examples 1-6, Comparative Example 2), hafnium oxide layers (Comparative Example 1), and silicon oxide layers (Comparative Example 3) for Examples 1-6 and Comparative Examples 1-3. Table 2 shows the evaluation results of the two-layer films of the hafnium silicon oxide layers (Examples 1-6, Comparative Example 2), hafnium oxide layers (Comparative Example 1), and silicon oxide layers (Comparative Example 3) in Table 1 and the magnesium fluoride layer.

[0042] [Table 1]

[0043] [Table 2]

[0044] The silicon ratio ([Si] / ([Si]+[Hf])) in Example 1 was 0.095. The oxygen atom content in the hafnium silicon oxide layer in Example 1 was 65.9 at%. Furthermore, the average light absorptance of the two-layer film consisting of the hafnium silicon oxide layer and the magnesium fluoride layer in Example 1 at wavelengths of 280 to 450 nm was 0.30%, the average interface absorptance at wavelengths of 280 to 450 nm was 0.09%, and the refractive index at a wavelength of 280 nm was 2.157. There were no problems with either adhesion or environmental resistance.

[0045] The silicon ratio ([Si] / ([Si]+[Hf])) in Example 2 was 0.168. The oxygen atom content in the hafnium silicon oxide layer in Example 2 was 66.5 at %. Furthermore, the average light absorptance of the two-layer film consisting of the hafnium silicon oxide layer and the magnesium fluoride layer in Example 2 at wavelengths of 280 to 450 nm was 0.23%, the average interface absorptance at wavelengths of 280 to 450 nm was 0.02%, and the refractive index at a wavelength of 280 nm was 2.131. There were no problems with either adhesion or environmental resistance.

[0046] The silicon ratio ([Si] / ([Si]+[Hf])) in Example 3 was 0.219. The oxygen atom content in the hafnium silicon oxide layer in Example 3 was 66.4 at%. Furthermore, the average light absorptance of the two-layer film consisting of the hafnium silicon oxide layer and the magnesium fluoride layer in Example 3 at wavelengths of 280 to 450 nm was 0.19%, the average interface absorptance at wavelengths of 280 to 450 nm was 0.00%, and the refractive index at a wavelength of 280 nm was 2.050. There were no problems with either adhesion or environmental resistance.

[0047] The silicon ratio ([Si] / ([Si]+[Hf])) in Example 4 was 0.410. The oxygen atom content in the hafnium silicon oxide layer in Example 4 was 67.1 at%. Furthermore, the average light absorptance of the two-layer film consisting of the hafnium silicon oxide layer and the magnesium fluoride layer in Example 4 at wavelengths of 280 to 450 nm was 0.18%, the average interface absorptance at wavelengths of 280 to 450 nm was -0.05%, and the refractive index at a wavelength of 280 nm was 1.902. There were no problems with either adhesion or environmental resistance.

[0048] The silicon ratio ([Si] / ([Si]+[Hf])) in Example 5 was 0.670. The oxygen atom content in the hafnium silicon oxide layer in Example 5 was 66.9 at%. Furthermore, the average light absorptance of the two-layer film consisting of the hafnium silicon oxide layer and the magnesium fluoride layer in Example 5 at wavelengths of 280 to 450 nm was 0.13%, the average interface absorptance at wavelengths of 280 to 450 nm was -0.06%, and the refractive index at a wavelength of 280 nm was 1.840. There were no problems with either adhesion or environmental resistance.

[0049] The silicon ratio ([Si] / ([Si]+[Hf])) in Example 6 was 0.902. The oxygen atom content in the hafnium silicon oxide layer in Example 6 was 66.7 at%. Furthermore, the average light absorptance of the two-layer film consisting of the hafnium silicon oxide layer and the magnesium fluoride layer in Example 6 at wavelengths of 280 to 450 nm was 0.08%, the average interface absorptance at wavelengths of 280 to 450 nm was -0.08%, and the refractive index at a wavelength of 280 nm was 1.538. There were no problems with adhesion, but slight cracking occurred in the environmental resistance.

[0050] The hafnium oxide layer of Comparative Example 1 had a silicon ratio ([Si] / ([Si]+[Hf])) of 0.000. The oxygen atom content in the hafnium oxide layer of Comparative Example 1 was 65.3 at %. Furthermore, the two-layer film consisting of the hafnium oxide layer and the magnesium fluoride layer of Comparative Example 1 had an average light absorptance of 0.60% at wavelengths of 280 to 450 nm, an average interface absorptance of 0.38% at wavelengths of 280 to 450 nm, and a refractive index of 2.249 at a wavelength of 280 nm. There were no problems with either adhesion or environmental resistance.

[0051] The silicon ratio ([Si] / ([Si]+[Hf])) of Comparative Example 2 was 0.037. The oxygen atom content in the hafnium silicon oxide layer of Comparative Example 2 was 65.1 at%. Furthermore, the average light absorptance of the two-layer film consisting of the hafnium silicon oxide layer and the magnesium fluoride layer of Comparative Example 2 at wavelengths of 280 to 450 nm was 0.49%, the average interface absorptance at wavelengths of 280 to 450 nm was 0.26%, and the refractive index at a wavelength of 280 nm was 2.131. There were no problems with either adhesion or environmental resistance.

[0052] The silicon ratio ([Si] / ([Si]+[Hf])) in Comparative Example 3 was 1.000. The oxygen atom content in the hafnium silicon oxide layer in Comparative Example 3 was 66.6 at%. Furthermore, the average light absorptance of the two-layer film consisting of the hafnium oxide layer and the magnesium fluoride layer in Comparative Example 1 at wavelengths of 280 to 450 nm was 0.03%, the average interface absorptance at wavelengths of 280 to 450 nm was -0.04%, and the refractive index at a wavelength of 280 nm was 1.514. As a result, peeling of the film was confirmed in both adhesion and environmental resistance.

[0053] Comparing Example 1-6 and Comparative Example 1-2, Example 1-6 exhibits a lower optical absorptance than Comparative Example 1-2. The assumed mechanism for this is explained below. In the bilayer film consisting of a silicon-free hafnium oxide layer and a magnesium fluoride layer described in Comparative Example 1, interface absorption occurs. As a result, the optical absorptance of the bilayer film is 0.38% greater than the sum of the optical absorptance of the hafnium oxide monolayer and the magnesium fluoride monolayer. As a result, the optical absorptance of the bilayer film is 0.60%, which is a high absorptance. This is believed to be because even slight defects in the hafnium oxide layer cause fluorine atoms located near the interface to be trapped in the defects in the hafnium oxide, forming an altered fluoride layer with electronic defects near the interface with the fluoride layer. Therefore, it was thought that defects in the oxide could be suppressed by adding silicon atoms, which have a smaller atomic radius than hafnium and are more likely to bond with oxygen. In Examples 1-6, thorough investigations were conducted to identify a region where the total light absorption can be reduced by the effect of reducing the interface absorption by adding silicon. A first guideline for the light absorption is that it is less than the light absorption of a two-layer film consisting of a hafnium oxide layer and a magnesium fluoride layer, and the interface absorption of the hafnium silicon oxide layer and the magnesium fluoride layer is less than 0.1%. A suitable refractive index is 1.80 or more, more preferably 2.1 or more. Comparative Example 3 shows that the two-layer film consisting of a silicon oxide layer and a magnesium fluoride layer has poor adhesion and environmental resistance, resulting in film cracking and peeling. Comparative Example 3 shows that if the silicon content [Si] at% in the hafnium silicon oxide layer is increased too much, the influence of silicon oxide, which has a lower refractive index than hafnium oxide, becomes stronger, resulting in a lower refractive index.

[0054] From the above, it can be seen that a laminated structure of a hafnium silicon oxide layer and a magnesium fluoride layer in which the silicon ratio ([Si] / ([Si]+[Hf])) is in the range of 0.095 or more and 0.902 or less has low optical absorption and is suitable for high-performance optical elements. Furthermore, the oxygen content [O]at% in the hafnium silicon oxide layer is preferably 65.5at% or more and 67.1at% or less. Furthermore, the sum of the hafnium content [Hf]at% and the silicon content [Si]at% and the oxygen content [O]at% is preferably 98.0at% or more. The hafnium content [Hf]at% is preferably 3.2at% or more and 29.2at% or less. The silicon content [Si]at% is preferably 3.1at% or more and 29.3at% or less.

[0055] The hafnium silicon oxide layer of this example contains elements other than hafnium, silicon, and oxygen. For example, the hafnium silicon oxide layer described in the above example may contain argon. This argon originates from argon gas introduced through the argon gas inlet port 205 during film formation. The argon content [Ar] at% in the hafnium silicon oxide layer is preferably less than 2.0 at%. The hafnium silicon oxide layer described in the above example may also contain zirconium. This zirconium originates from the sputtering target 209 used during film formation. The zirconium content [Zr] at% in the hafnium silicon oxide layer is preferably less than 0.14 at%. The zirconium content [Zr] at% in the hafnium silicon oxide layer described in the above example was 0.01 to 0.12 at%. This embodiment can achieve a high refractive index and low optical absorption even while containing argon and zirconium. The carbon content [C] at % in the hafnium silicon oxide layer described in the above examples is below the detection limit.

[0056] For reference, Figure 3 shows a graph representing the average optical absorptance at wavelengths from 280 nm to 450 nm versus the silicon content of oxide films containing hafnium and silicon. Figure 4 shows a graph representing the average interfacial absorptance at wavelengths from 280 nm to 450 nm between a hafnium silicon oxide layer and a magnesium fluoride layer versus the silicon content of oxide films containing hafnium and silicon. Figure 5 shows a graph representing the optical absorptance characteristics at wavelengths from 280 nm to 450 nm versus the silicon content of oxide films containing hafnium and silicon. Figure 6 shows a graph representing the refractive index versus the silicon content of oxide films containing hafnium and silicon.

[0057] 3 and 4 show that when the silicon ratio ([Si] / ([Si] + [Hf])) is 0.095 or more, the optical absorption of the bilayer film consisting of a hafnium silicon oxide layer and a magnesium fluoride layer is less than 0.3%, and the interface absorption between the hafnium silicon oxide layer and the magnesium fluoride layer is less than 0.1%. Furthermore, when the silicon ratio ([Si] / ([Si] + [Hf])) is 0.200 or more, the interface absorption between the hafnium silicon oxide layer and the magnesium fluoride layer is less than 0.00%. The optical absorption of the bilayer film consisting of a hafnium silicon oxide layer and a magnesium fluoride layer varies depending on the silicon ratio ([Si] / ([Si] + [Hf])). Figure 5 shows the optical absorption of the bilayer film consisting of a hafnium silicon oxide layer and a magnesium fluoride layer. As shown in Figure 5, in Example 4, the absorption significantly decreases in the wavelength range from 280 nm to 450 nm. It is clear that a significantly lower light absorption rate is obtained compared to the two-layer film consisting of a hafnium oxide layer and a magnesium fluoride layer in Comparative Example 1.

[0058] As shown in Figure 6, when the silicon ratio ([Si] / ([Si]+[Hf])) is 0.700 or less, it is estimated that a refractive index of 1.8 or more, which is preferable for a high refractive index layer, can be obtained. When the silicon ratio is 0.28 or less, it is clear that a refractive index of 2.00 or more, which is even more preferable for a high refractive index layer, can be obtained.

[0059] [Example 7], [Comparative Example 4] A specific example of an optical structure (anti-reflection structure) fabricated on the surface of a transmissive optical element will be described. In Example 7, an optical structure (anti-reflection structure) was fabricated in which hafnium silicon oxide layers serving as high-refractive index layers and silicon oxide layers serving as low-refractive index layers were alternately stacked, with a magnesium fluoride layer serving as a low-refractive index layer disposed on the outermost surface. This corresponds to the configuration of the optical structure 102 shown in FIG. 1(b). Specifically, a total of seven hafnium silicon oxide layers serving as high-refractive index layers and silicon oxide layers serving as low-refractive index layers were alternately stacked on a quartz substrate serving as a base 101 made of silicon oxide. The optical structure 102 was then fabricated with a magnesium fluoride layer serving as a low-refractive index layer deposited on the outermost surface. The hafnium silicon oxide layer (high-refractive index layer) used had a silicon ratio ([Si] / ([Si]+[Hf])) of 0.410, as described in Example 4. Furthermore, as Comparative Example 4, an optical structure (anti-reflection structure) was fabricated in which hafnium oxide layers as high refractive index layers and silicon oxide layers as low refractive index layers were alternately stacked, with a magnesium fluoride layer as the outermost low refractive index layer. The hafnium oxide layer as the high refractive index layer was the same as that described in Comparative Example 1.

[0060] In consideration of the intended use of the optical element 100, in order to maximize the anti-reflection properties in the wavelength range of 280 nm to 450 nm, the physical film thickness of each layer was optimized based on the refractive index values ​​at a wavelength of 280 nm in Example 4 and Comparative Example 1, and the configuration of the optical structure was determined.

[0061] The specifications of each layer in Example 7 are shown in Table 3.

[0062] [Table 3]

[0063] The specifications of each layer in Comparative Example 4 are shown in Table 3.

[0064] [Table 4]

[0065] FIG. 7 shows the transmittance characteristics of samples in which the optical structures shown in Tables 3 and 4 were formed on both sides of a 2 mm quartz substrate of the optical structures (anti-reflection structures) of Example 7 and Comparative Example 4, respectively. In the wavelength range of 280 nm to 450 nm, the light absorptance per 100 nm of each film material was 0.12% for the hafnium silicon oxide layer, 0.19% for hafnium oxide, almost zero (below the measurement limit) for silicon oxide, and 0.04% for magnesium fluoride. Furthermore, the interface absorption between the hafnium silicon oxide layer and magnesium fluoride was almost zero. The interface absorption between the hafnium oxide layer and the magnesium fluoride layer was 0.38%. Furthermore, the interface absorption between the hafnium silicon oxide layer and the silicon oxide layer, and between the hafnium oxide layer and the silicon oxide layer, were also almost zero. From these light absorptances, the light absorptance per surface of the optical structure (anti-reflection structure) of Example 7 in Table 3 and the transmission loss due to interface absorptance were estimated to be 0.16%. In contrast, the transmission loss due to the optical absorptance and interface absorptance per surface of the optical structure (anti-reflection structure) of Comparative Example 4 in Table 3 was calculated in a similar manner and was found to be 0.55%. In the sample shown in FIG. 7, in addition to the transmission loss due to the optical absorptance and interface absorptance, a reflectance loss is also added. Regarding the loss of the optical structure for two surfaces, when the difference in reflectance due to the difference in the refractive index of the high refractive index material in Example 7 was evaluated as an average value in the wavelength range of 280 nm to 450 nm, Example 7 was 0.38% while Comparative Example 4 was 0.44%, which is only a slight difference. As a result, in terms of the average transmittance in the wavelength range of 280 nm to 450 nm, Example 7 using hafnium silicon oxide achieved a transmittance of 98.9%, which is higher than the 98.1% of Comparative Example 4 using hafnium oxide.

[0066] [Example 8], [Comparative Example 5] A specific example in which at least one lens of a lens group provided in an exposure apparatus (semiconductor manufacturing apparatus) is coated with an optical structure (anti-reflection structure) will be described. As Example 8, a lens group was created in which both surfaces of 20 lenses (a total of 40 surfaces) provided in the exposure apparatus were coated with the optical structure (anti-reflection structure) described in Example 7. That is, an optical structure (anti-reflection structure) was formed on the surface of each lens by alternately stacking hafnium silicon oxide layers (high refractive index material) and silicon oxide layers (intermediate refractive index material), with magnesium fluoride (low refractive index material) as the outermost layer. Furthermore, the hafnium silicon oxide layer (high refractive index material) used contained 41.0% silicon when the ratio of the hafnium content [Hf] at % to the silicon content [Si] at % ([Si] / ([Si]+[Hf]) described in Example 4 was used. Furthermore, as Comparative Example 6, a group of lenses was produced in which both surfaces of 20 lenses (40 surfaces in total) were coated with the optical structure (anti-reflection structure) described in Comparative Example 4. That is, an optical structure (anti-reflection structure) was formed on the surface of each lens by alternately layering hafnium oxide layers (high refractive index material) and silicon oxide layers (intermediate refractive index material), with magnesium fluoride (low refractive index material) as the outermost layer.

[0067] For Example 8 and Comparative Example 5, to evaluate their suitability as lenses for use in exposure equipment equipped with an ultraviolet light source, transmission loss due to light absorption was evaluated using the average value of ultraviolet light with wavelengths from 280 nm to 450 nm. The results are shown in Table 5. In lenses for exposure equipment equipped with an ultraviolet light source, ultraviolet light generated by the ultraviolet light source is irradiated onto the optical structure (anti-reflection structure) of the lens, so ultraviolet light was irradiated onto the optical structure (anti-reflection structure) in the same manner. Even in cases where a light source of infrared light or visible light is used, suitability as an optical element can be evaluated in the same manner using the light irradiated onto the optical structure (anti-reflection structure).

[0068] [Table 5]

[0069] In the lens group of Example 8, low light absorptance is achieved at each surface, and transmission loss can be made extremely small, so that transmission loss can be suppressed to 10% or less even at lens surface 40. On the other hand, in Comparative Example 5, low light absorptance, particularly the interface absorptance between the hafnium oxide layer and the magnesium fluoride layer, is significantly increased compared to Example 8, so that transmission loss at lens surface 40 reaches 10% or more.

[0070] The lens group of Example 8 has the effect of increasing the exposure intensity of an exposure apparatus when used in, for example, an illumination lens group or a projection lens group of an exposure apparatus, which makes it possible to shorten the exposure time and improve the processing capacity of the exposure apparatus.

[0071] [Other embodiments] The present invention is not limited to the above-described embodiments and examples, and many modifications are possible within the technical concept of the present invention.

[0072] The high-refractive-index film according to embodiment 1 is widely applicable to coating optical elements, including lenses, filters, mirrors, prisms, imaging devices (image sensors), and display devices (displays). Furthermore, it can be used in optical devices equipped with optical elements, such as exposure devices, various cameras, and interchangeable lenses. These optical devices may include multiple optical components, including optical elements coated with a film having a configuration in which a hafnium silicon oxide layer and a magnesium fluoride layer are in contact with each other, as well as a holding component (lens barrel) for holding the multiple optical components. By laminating the high-refractive-index film according to embodiment 1 and a low-refractive-index film having a lower refractive index, a high-performance anti-reflection structure or reflective structure can be formed. For example, in an exposure device equipped with an ultraviolet light source, the exposure performance of the exposure device using ultraviolet light can be improved by providing the anti-reflection structure according to embodiment 1 on the lens and / or the reflective structure according to embodiment 1 on the mirror.

[0073] [Disclosure details] This specification includes the following disclosure.

[0074] [Matter 1] An optical element comprising a substrate and an optical structure provided on the substrate, the optical structure has at least one oxide layer and at least one fluoride layer; a distance between the one oxide layer and the one fluoride layer is smaller than a thickness of the one fluoride layer; The hafnium content in the at least one oxide layer is [Hf] at %, and the silicon content in the at least one oxide layer is [Si] at %, 0.095≦[Si] / ([Si]+[Hf])<0.902 Optical elements that satisfy the above requirements.

[0075] [Matter 2] [Hf]≧3.2at% Item 1. The optical element according to item 1,

[0076] [Matter 3] [Si]≦29.3at% 3. The optical element according to item 1 or 2,

[0077] [Matter 4] the oxygen content in the at least one oxide layer being [O] at %, [O]≧65.0at% 4. The optical element according to any one of items 1 to 3, which satisfies the above.

[0078] [Matter 5] [Si] / ([Si]+[Hf])≧0.219 5. The optical element according to any one of items 1 to 4, which satisfies the above.

[0079] [Matter 6] the argon content in the at least one oxide layer, expressed as [Ar] at %, 0.9at%≦[Ar]≦1.8at% 6. The optical element according to any one of items 1 to 5, which satisfies the above.

[0080] [Matter 7] the zirconium content in the at least one oxide layer, expressed as [Zr] at %, 0.01at%≦[Zr]≦0.12at% 7. The optical element according to any one of items 1 to 6, which satisfies the above.

[0081] [Matter 8] the oxygen content in the at least one oxide layer being [O] at %, [Hf] + [Si] + [O] ≥ 98.0 at% 8. The optical element according to any one of items 1 to 7, which satisfies the following:

[0082] [Matter 9] 9. The optical element according to any one of items 1 to 8, wherein the optical structure has an anti-reflection structure.

[0083] [Matter 10] 9. The optical element of any one of items 1 to 8, wherein the optical structure has a reflective structure.

[0084] [Matter 11] 11. The optical element according to any one of items 1 to 10, wherein the at least one oxide layer includes a first oxide layer that is the one oxide layer and a second oxide layer that is different from the one oxide layer, the first oxide layer is located between the one fluoride layer and the substrate, the second oxide layer is located between the first oxide layer and the substrate, and a dielectric layer having a refractive index lower than that of the first oxide layer and the second oxide layer is located between the first oxide layer and the second oxide layer.

[0085] [Matter 12] Item 12. The optical element according to item 11, wherein the at least one oxide layer includes a third oxide layer between the second oxide layer and the substrate, and a dielectric layer having a refractive index lower than that of the second oxide layer and the third oxide layer is located between the second oxide layer and the third oxide layer.

[0086] [Matter 13] 13. The optical element according to item 11 or 12, wherein the dielectric layer is a silicon oxide layer.

[0087] [Matter 14] the at least one oxide layer includes a first oxide layer that is the one oxide layer and a second oxide layer that is different from the one oxide layer, and the at least one fluoride layer includes a first fluoride layer that is the one fluoride layer and a second fluoride layer that is different from the one oxide layer; 11. The optical element of any one of items 1 to 10, wherein the first fluoride layer is located between the first oxide layer and the substrate, the second oxide layer is located between the first fluoride layer and the substrate, and the second fluoride layer is located between the second oxide layer and the substrate.

[0088] [Matter 15] 15. The optical element according to any one of items 1 to 14, wherein the surface of the substrate on the side of the optical structure is a concave or convex surface.

[0089] [Matter 16] 16. The optical element according to any one of items 1 to 15, wherein the main component of the substrate is silicon oxide or calcium fluoride.

[0090] [Matter 17] 17. The optical element according to any one of items 1 to 16, wherein the optical element is a lens, a mirror or a prism.

[0091] [Matter 18] The optical element according to any one of items 1 to 17, a holding component for holding the optical element, The device characterized by:

[0092] [Matter 19] The optical element according to any one of items 1 to 18, a light source that generates ultraviolet light to irradiate the optical structure; The device characterized by:

[0093] [Matter 20] a reticle stage for mounting a reticle; a substrate stage on which a substrate is mounted, 20. The apparatus of item 19, wherein ultraviolet light generated by the light source is irradiated onto the substrate through the reticle and the optical element.

[0094] The embodiments described above can be modified as appropriate without departing from the technical concept. For example, multiple embodiments can be combined. Furthermore, some features of at least one embodiment can be deleted or replaced. Furthermore, new features can be added to at least one embodiment.

[0095] The disclosure of this specification includes not only what is explicitly described herein but also all matters that can be understood from this specification and the drawings attached hereto. Furthermore, the disclosure of this specification includes the complement of the individual concepts described herein. In other words, if this specification contains a statement that "A is B," for example, it can be said that this specification discloses that "A is not B," even if it omits a statement that "A is not B." This is because a statement that "A is B" presupposes that the case in which "A is not B" is taken into consideration.

[0096] Furthermore, in the specific numerical ranges exemplified herein, the notation "e to f" (e and f are numbers) means greater than or equal to e and / or less than or equal to f. Furthermore, when a range of i to j and a range of m to n are both given (i, j, m, and n are numbers) for the specific numerical ranges exemplified, the combination of the lower limit and the upper limit is not limited to the combination of i and j or the combination of m and n. For example, a combination of multiple sets of lower limits and upper limits may be considered. That is, when a range of i to j and a range of m to n are both given, the range of i to n or the range of m to j may be considered within a range that does not cause a contradiction. Furthermore, "greater than or equal to e" means either e or greater than e (exceeding e), and a value greater than e may be used without adopting e. Furthermore, "less than or equal to f" means either f or smaller than f (less than e), and a value smaller than f may be used without adopting f.

[0097] The embodiments described above can be modified as appropriate without departing from the technical concept. For example, multiple embodiments can be combined. Furthermore, some features of at least one embodiment can be deleted or replaced. Furthermore, new features can be added to at least one embodiment.

[0098] The disclosure of this specification includes not only what is explicitly described herein but also all matters that can be understood from this specification and the drawings attached hereto. Furthermore, the disclosure of this specification includes the complement of each individual concept described herein. In other words, if this specification describes, for example, "A is B," it can be said that this specification discloses the case where "A is not B," even if it omits a description of the case where "A is not B." This is because a description of "A is B" presupposes that the case where "A is not B" is taken into consideration. [Explanation of symbols]

[0099] 100 Optical Elements 101 Base 102 Optical structure 102a High refractive index oxide layer 102b Low refractive index fluoride layer 102c Low refractive index oxide layer

Claims

1. An optical element comprising a substrate and an optical structure provided on the substrate, the optical structure has at least one oxide layer and at least one fluoride layer; a distance between the one oxide layer and the one fluoride layer is smaller than a thickness of the one fluoride layer; The hafnium content in the at least one oxide layer is [Hf] at %, and the silicon content in the at least one oxide layer is [Si] at %, 0.095≦[Si] / ([Si]+[Hf])<0.902 Optical elements that satisfy the above requirements.

2. [Hf]≧3.2at% The optical element according to claim 1 , wherein

3. [Si]≦29.3at% The optical element according to claim 1 , wherein

4. the oxygen content in the at least one oxide layer being [O] at %, [O]≧65.0at% The optical element according to claim 1 , wherein

5. [Si] / ([Si]+[Hf])≧0.219 The optical element according to claim 1 , wherein

6. the argon content in the at least one oxide layer, expressed as [Ar] at %, 0.9at%≦[Ar]≦1.8at% The optical element according to claim 1 , wherein

7. the zirconium content in the at least one oxide layer is expressed as [Zr] at %, 0.01at%≦[Zr]≦0.12at% The optical element according to claim 1 , wherein

8. the oxygen content in the at least one oxide layer being [O] at %, [Hf]+[Si]+[O]≧98.0at% The optical element according to claim 1 , wherein

9. The optical element according to claim 1 , wherein the optical structure has an anti-reflection structure.

10. The optical element according to claim 1 , wherein the optical structure comprises a reflective structure.

11. 9. The optical element according to claim 1, wherein the at least one oxide layer includes a first oxide layer that is the one oxide layer and a second oxide layer that is different from the one oxide layer, the first oxide layer is located between the one fluoride layer and the substrate, the second oxide layer is located between the first oxide layer and the substrate, and a dielectric layer having a refractive index lower than that of the first oxide layer and the second oxide layer is located between the first oxide layer and the second oxide layer.

12. 12. The optical element of claim 11, wherein the at least one oxide layer includes a third oxide layer between the second oxide layer and the substrate, and a dielectric layer having a lower refractive index than the second oxide layer and the third oxide layer is located between the second oxide layer and the third oxide layer.

13. The optical element of claim 11 , wherein the dielectric layer is a silicon oxide layer.

14. the at least one oxide layer includes a first oxide layer that is the one oxide layer and a second oxide layer that is different from the one oxide layer, and the at least one fluoride layer includes a first fluoride layer that is the one fluoride layer and a second fluoride layer that is different from the one oxide layer; 9. The optical element according to claim 1, wherein the first fluoride layer is located between the first oxide layer and the substrate, the second oxide layer is located between the first fluoride layer and the substrate, and the second fluoride layer is located between the second oxide layer and the substrate.

15. The optical element according to claim 1 , wherein the surface of the substrate on the side of the optical structure is a concave or convex surface.

16. 9. The optical element according to claim 1, wherein the main component of the substrate is silicon oxide or calcium fluoride.

17. The optical element according to claim 1 , wherein the optical element is a lens, a mirror, or a prism.

18. The optical element according to any one of claims 1 to 8; a holding component for holding the optical element, A device characterized by:

19. The optical element according to any one of claims 1 to 8; a light source that generates ultraviolet light to irradiate the optical structure; A device characterized by:

20. a reticle stage for mounting a reticle; a substrate stage on which a substrate is mounted, 20. The apparatus of claim 19, wherein ultraviolet light generated by the light source is irradiated onto the substrate through the reticle and the optical element.

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