Optical Components and Instruments

Abstract

To provide a technique that is advantageous in improving an optical characteristic of an optical component.SOLUTION: An optical component includes a base and a multilayer film including a first layer group provided on the base and a second layer group provided between the first layer group and the base. A first dielectric layer and a second dielectric layer are alternately stacked in the second layer group, a third dielectric layer and a fourth dielectric layer are alternately stacked in the first layer group, a refractive index of the first dielectric layer is higher than a refractive index of the second dielectric layer, a refractive index of the third dielectric layer is higher than a refractive index of the fourth dielectric layer, the composition of the first dielectric layer and the composition of the second dielectric layer are different from each other, the first dielectric layer contains a compound of a first metal element, and the third dielectric layer contains a compound of a second metal element different from the first metal element.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an optical component having a laminated film. [Background technology]

[0002] 2. Description of the Related Art Laminated films in which a plurality of dielectric layers are stacked are used in a variety of optical components, such as anti-reflection films, reflective films, and filter films, due to their high degree of design freedom.

[0003] Patent Documents 1 and 2 disclose optical elements having a dielectric multilayer film. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2005-345492 A [Patent Document 2] Japanese Patent Application Publication No. 7-244205 Summary of the Invention [Problem to be solved by the invention]

[0005] The techniques described in Patent Documents 1 and 2 do not sufficiently consider the improvement of the optical characteristics of optical elements. Therefore, an object of the present invention is to provide a technique that is advantageous for improving the optical characteristics of optical components. [Means for solving the problem]

[0006] A first aspect of the means for solving the above problem provides a laminated film including a base, a first layer group provided on the base, and a second layer group provided between the first layer group and the base, wherein a first dielectric layer and a second dielectric layer are alternately laminated in the second layer group, a third dielectric layer and a fourth dielectric layer are alternately laminated in the first layer group, a refractive index of the first dielectric layer is higher than a refractive index of the second dielectric layer, and a refractive index of the third dielectric layer is higher than a refractive index of the fourth dielectric layer, and at least one of (i) the refractive index of the third dielectric layer is higher than the refractive index of the first dielectric layer, (ii) a difference between the refractive index of the third dielectric layer and the refractive index of the fourth dielectric layer is larger than a difference between the refractive index of the first dielectric layer and the refractive index of the second dielectric layer, and (iii) a density of the third dielectric layer is lower than a density of the first dielectric layer. The first dielectric layer contains ytterbium fluoride. The optical component is characterized by the above. Effect of the Invention

[0008] According to the present invention, it is possible to provide a technique that is advantageous in improving the optical characteristics of an optical component. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a schematic diagram illustrating optical components. [Diagram 2] Periodic table. [Diagram 3] FIG. 2 is a schematic diagram illustrating optical components. [Figure 4] FIG. 1 is a schematic diagram illustrating an optical device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment 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. In addition, common components may be described by mutually referring to multiple drawings without notice. Also, descriptions of components with common reference numerals may be omitted.

[0011] The optical component 30 will be described with reference to FIG. 1. The optical component 30 includes a base 10 and a laminated film 20 provided on the base 10. The optical component 30 can be used such that light is incident on the laminated film 20 from the side opposite to the base 10. Alternatively, the optical component 30 can be used such that light is incident on the laminated film 20 from the side of the base 10. The laminated film 20 in the optical component 30 can be used as a reflective film such that light of a predetermined wavelength is reflected by the laminated film 20. Alternatively, the laminated film 20 in the optical component 30 can be used as a filter film such that light of a predetermined wavelength is selectively transmitted by the laminated film 20. Alternatively, the laminated film 20 can be used as an anti-reflection film for suppressing reflection in the optical component 30.

[0012] The laminated film 20 includes a dielectric layer group 27 and a dielectric layer group 28. The dielectric layer group 27 is provided between the dielectric layer group 28 and the substrate 10. The laminated film 20 may further include a dielectric layer group 29. The dielectric layer group 28 is provided between the dielectric layer group 27 and the dielectric layer group 29.

[0013] The laminated film 20 includes a dielectric layer 21, a dielectric layer 22, a dielectric layer 23, and a dielectric layer 24. Furthermore, the laminated film 20 may include a dielectric layer 25 or may include a dielectric layer 26, but the laminated film 20 does not have to include at least one of the dielectric layer 25 and the dielectric layer 26. Since the laminated film 20 is formed by laminating a large number of dielectric layers, it can also be called a dielectric multilayer film or a dielectric laminated film.

[0014] The dielectric layer group 27 includes a dielectric layer 21 and a dielectric layer 22. The dielectric layer 21 is provided between the dielectric layer 22 and the substrate 10. In the dielectric layer group 27, the dielectric layer 21 and the dielectric layer 22 are preferably alternately stacked. The dielectric layer group 28 includes a dielectric layer 23 and a dielectric layer 24. The dielectric layer 23 is provided between the dielectric layer 24 and the substrate 10. In the dielectric layer group 28, the dielectric layer 23 and the dielectric layer 24 are preferably alternately stacked. Here, the alternate stacking of the first type layer and the second type layer means a state in which 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 four layers are required for the first type layer and the second type layer to be alternately stacked. However, in the dielectric layer group 27 of FIG. 1, one each of the two types of dielectric layers 21 and 22 is described, totaling two layers. Here, the embodiment in which the laminated film 20 includes the dielectric layer group 27 and the dielectric layer group 28 has been described, but the laminated film 20 may have a configuration in which sets of the dielectric layer 21, the dielectric layer 22, the dielectric layer 23, and the dielectric layer 24 are repeatedly laminated. The dielectric layer 25 and the dielectric layer 26 are included in the dielectric layer group 29. In the dielectric layer group 29, the dielectric layer 25 and the dielectric layer 26 do not have to be alternately laminated, or may be alternately laminated.

[0015] The dielectric layer 21 is provided between the substrate 10 and the dielectric layer 23. The refractive index Na of the dielectric layer 21 is higher than the refractive index Nb of the dielectric layer 22 (Na > Nb). The distance Db between the dielectric layer 21 and the dielectric layer 22 is smaller than the thickness Ta of the dielectric layer 21 (Db < Ta). This means that the dielectric layer 21 and the dielectric layer 22 are arranged in the vicinity of each other (proximate). Typically, the dielectric layer 22 is in contact with the dielectric layer 21 and the distance Db is zero, but another dielectric layer (not shown) may be arranged between the dielectric layer 21 and the dielectric layer 22. The refractive index Nc of the dielectric layer 23 is higher than the refractive index Nd of the dielectric layer 24 (Nc > Nd). The distance Dc between the dielectric layer 22 and the dielectric layer 23 depends on the number of layers between the dielectric layers 22 and 23 of interest, but can be less than 1 μm. The distance Dc may be larger than the thickness Tb and the thickness Tc. The distance Dd between the dielectric layer 23 and the dielectric layer 24 is smaller than the thickness Tc of the dielectric layer 23 (Dd < Tc). Typically, the dielectric layer 24 is in contact with the dielectric layer 23 and the distance Dd is zero, but another dielectric layer (not shown) may be arranged between the dielectric layer 23 and the dielectric layer 24. The distance Df between the dielectric layer 25 and the dielectric layer 26 is smaller than the thickness Te of the dielectric layer 25 (Df < Te). Typically, the dielectric layer 26 is in contact with the dielectric layer 25 and the distance Df is zero, but another dielectric layer (not shown) may be arranged between the dielectric layer 25 and the dielectric layer 26. The distance De between the dielectric layer 24 and the dielectric layer 25 depends on the number of layers between the dielectric layers 24 and 25 of interest, but can be less than 1 μm. The distance De may be larger than the thickness Td and the thickness Tf.

[0016] The dielectric layer 21 contains a compound of the metal element Mtla. The dielectric layer 23 contains a compound of the metal element Mtlc. The metal element Mtlc is an element different from the metal element Mtla. Note that two elements being different elements means that they have different atomic numbers, and two elements being the same element means that they have the same atomic number. FIG. 2 shows a periodic table with element symbols and atomic numbers, where the hatched elements are metal elements and the non-hatched elements are non-metal elements.

[0017] The composition of the dielectric layer 21 is different from the composition of the dielectric layer 23. The composition here refers to at least one of the combination of all elements constituting the dielectric layers 21 and 23 and the ratio of all elements.

[0018] The dielectric layers 21 and 23 have a higher refractive index than the dielectric layers 22 and 24 located nearby each other. Of the two dielectric layers located nearby each other, the dielectric layer (dielectric layers 21 and 23) with a relatively higher refractive index is called a high refractive index layer, and the dielectric layer (dielectric layers 22 and 24) with a relatively lower refractive index is called a low refractive index layer. The physical thickness required to set the optical thickness of the dielectric layers 21 and 23 within a predetermined range can be smaller than the physical thickness required to set the optical thickness of the dielectric layers 22 and 24 within a predetermined range. Therefore, there is a high degree of freedom in material selection and film thickness setting. Therefore, the dielectric layers 21 and 23 are suitable for making the compositions of each layer different. The optical thickness of each of the dielectric layers 21, 22, 23, and 24 can be appropriately set according to the wavelength λ of the light to be transmitted or reflected, and is typically less than the wavelength λ, for example, λ / 8 to 3λ / 8. The optical thicknesses of the dielectric layers 21, 22, 23, and 24 may be different or the same.

[0019] In a dielectric multilayer film, the desired optical characteristics are achieved by utilizing the interference of reflected light at the interface between the low and high refractive index layers, so it is better to have a high reflectance at the interface between the low and high refractive index layers. For a low and high refractive index layer located near each other (e.g. forming an interface), the refractive index of the low refractive index layer is Nt and the refractive index of the high refractive index layer is Nk. The reflectance R between the low and high refractive index layers (e.g. at the interface) can be simply expressed as R={(Nk-Nt) / (Nk+Nt)} 2 In other words, the smaller the sum of the refractive index Nt of the low refractive index layer and the refractive index Nk of the high refractive index layer, the higher the reflectance R, and the larger the difference between the refractive index Nt of the low refractive index layer and the refractive index Nk of the high refractive index layer, the higher the reflectance R.

[0020] The concentration Ccc of the metal element Mtlc in the dielectric layer 23 may be different from the concentration Cca of the metal element Mtlc in the dielectric layer 21 (Ccc≠Cca). The concentration Ccc of the metal element Mtlc in the dielectric layer 23 is preferably higher than the concentration Cca of the metal element Mtlc in the dielectric layer 21 (Ccc>Cca). In a typical example, the dielectric layer 21 may not contain the metal element Mtlc, in which case the concentration Cca of the metal element Mtlc in the dielectric layer 21 is zero. In a modified example, the dielectric layer 21 may contain a compound of the metal element Mtla and a compound of the metal element Mtlc, and the dielectric layer 23 may also contain a compound of the metal element Mtla and a compound of the metal element Mtlc.

[0021] The concentration Caa of the metal element Mtla in the dielectric layer 21 may be different from the concentration Cmac of the metal element Mtla in the dielectric layer 23 (Caa ≠ Cac). The concentration Cmaa of the metal element Mtla in the dielectric layer 21 is preferably higher than the concentration Cac of the metal element Mtla in the dielectric layer 23 (Caa > Cac). In a typical example, the dielectric layer 23 may not contain the metal element Mtla, in which case the concentration Cca of the metal element Mtla in the dielectric layer 21 is zero. In another example, the dielectric layer 21 may contain a compound of the metal element Mtla and a compound of the metal element Mtlc, and the dielectric layer 23 may also contain a compound of the metal element Mtla and a compound of the metal element Mtlc.

[0022] The metal element Mtla can be a transition element. Also, the metal element Mtlc can be a transition element. In the periodic table shown in FIG. 2, the elements surrounded by a thick frame are transition elements, and the elements outside the thick frame are typical elements. When comparing compounds in which the nonmetallic elements of the compound are the same elements, compounds of transition metal elements generally have a higher refractive index than compounds of typical metal elements, and are therefore suitable as materials for high refractive index layers. However, at least one of the metal elements Mtla and Mtlc may be a typical element.

[0023] The compound contained in the dielectric layer 21 is, for example, a compound of a metal element Mtla and a nonmetal element Ntla, and is, for example, a boride, a carbide, a nitride, an oxide, a fluoride, a sulfide, a phosphide, or a chloride, and is typically an oxide or a fluoride. The compound contained in the dielectric layer 23 is, for example, a compound of a metal element Mtlc and a nonmetal element Ntla, and is, for example, a boride, a carbide, a nitride, an oxide, a fluoride, a sulfide, a phosphide, or a chloride, and is typically an oxide or a fluoride. The nonmetal element Ntlc may be the same element as the nonmetal element Ntla, or the nonmetal element Ntlc may be an element different from the metal element Mtla.

[0024] The metal element Mtla may be a rare earth element. The metal element Mtlc may be a rare earth element. Rare earth elements are elements with atomic numbers 21, 39, and 57 to 71. The dielectric layer 21 may contain a fluoride. The compound contained in the dielectric layer 21 may be a fluoride of the metal element Mtla. The dielectric layer 23 may contain a fluoride. The compound contained in the dielectric layer 23 may be a fluoride of the metal element Mtlc.

[0025] Many metal fluorides have lower absorption of ultraviolet light than many metal oxides, and therefore, in an optical component 30 intended to utilize ultraviolet light by transmission or reflection, it is effective in improving the utilization efficiency of ultraviolet light for at least one of the dielectric layers 21 and 23 to contain a metal fluoride.

[0026] The dielectric layer 23 may contain at least one of neodymium fluoride (NdF3), lanthanum fluoride (LaF3), gadolinium fluoride (GdF3), samarium fluoride (SmF3), cerium fluoride (CeF3), and aluminum oxide (Al2O3). The dielectric layer 21 may contain ytterbium fluoride (YbF3).

[0027] In other examples, the metal element Mtla can be a Group 4 element or a Group 5 element.

[0028] Moreover, the metal element Mtlc can be an element of Group 4 or Group 5. When the metal element Mtla or the metal element Mtlc is titanium, zirconium or hafnium, and the nonmetal element Ntla or Ntlc is oxygen, the dielectric layers 21 and 22 contain titanium oxide, zirconium oxide or hafnium oxide.

[0029] In another example, the metal element Mtla can be a Group 12 element or a Group 13 element. Also, the metal element Mtlc can be a Group 12 element or a Group 13 element. When the metal element Mtla or the metal element Mtlc is zinc, aluminum, gallium, or indium, and the nonmetal element Ntla or Ntlc is oxygen, the dielectric layers 21 and 22 contain zinc oxide, aluminum oxide, or gallium oxide.

[0030] The difference between the composition of the dielectric layer 21 and the composition of the dielectric layer 23 can improve the functionality of the laminated film 20. When the composition of the dielectric layer 21 and the composition of the dielectric layer 23 are different, the optical properties, chemical properties, and mechanical properties of each dielectric layer are different. The optical properties may be different refractive index and extinction coefficient. The chemical properties may be different diffusion constant and adhesion. The mechanical properties may be different surface shape, thermal expansion coefficient, elasticity coefficient, and the like. The combination of these properties can improve the functionality of the laminated film 20.

[0031] In a dielectric multilayer film, the desired optical characteristics are realized by utilizing the interference of reflected light at the interface between the high-refractive index layer and the low-refractive index layer, so the reflectance between the high-refractive index layer and the low-refractive index layer (for example, at the interface) is preferably high. To achieve this, the refractive index ratio (Nk / Nt) and the refractive index difference (Nk-Nt) between the high-refractive index layer and the low-refractive index layer should be large, and the sum of the refractive indices (Nk+Nt) between the high-refractive index layer and the low-refractive index layer should be small.

[0032] The reflectance Ra at the interface between the dielectric layer 21 and the dielectric layer 22 is Ra={(Na-Nb) / (Na+Nb)} 2 The reflectance Rc at the interface between the dielectric layer 23 and the dielectric layer 24 is expressed as Rc={(Nc-Nd) / (Nc+Nd)} 2It is represented by Ra<Rc. The condition for Ra<Rc is Na / Nb<Nc / Nd, and the condition for Ra>Rc is Na / Nb>Nc / Nd.

[0033] For example, when light is incident on the laminate film 20 from the side opposite to the substrate 10 and light of a predetermined wavelength is reflected by the laminate film 20, it is preferable to satisfy Rc>Ra. This is because arranging a reflection surface (interface) with a higher refractive index closer to the light incident surface (upper surface 202) is advantageous for increasing the reflectance of the laminate film 20. Alternatively, when light is incident on the laminate film 20 from the substrate 10 side and light of a predetermined wavelength is transmitted through the laminate film 20, it is also preferable to satisfy Rc>Ra. This is because arranging a reflection surface (interface) with a higher refractive index farther from the light incident surface (upper surface 202) is advantageous for increasing the transmittance of the laminate film 20.

[0034] The ratio Nc / Nd of the refractive index Nc of the dielectric layer 23 to the refractive index Nd of the dielectric layer 24 may be larger than the ratio Na / Nb of the refractive index Na of the dielectric layer 21 to the refractive index Nb of the dielectric layer 22 (Nc / Nd>Na / Nb). Satisfying Nc / Nd>Na / Nb is advantageous for satisfying Rc>Ra.

[0035] The difference Nc - Nd between the refractive index Nc of the dielectric layer 23 and the refractive index Nd of the dielectric layer 24 may be larger than the difference Na - Nb between the refractive index Na of the dielectric layer 21 and the refractive index Nb of the dielectric layer 22 (Nc - Nd>Na - Nb). The larger Nc - Nd is, the higher the reflectance Rc becomes.

[0036] The sum Nc+Nd of the refractive index Nc of the dielectric layer 23 and the refractive index Nd of the dielectric layer 24 may be smaller than the sum Na+Nb of the refractive index Na of the dielectric layer 21 and the refractive index Nb of the dielectric layer 22 (Nc+Nd<Na+Nb). The smaller Nc+Nd is, the higher the reflectance Rc becomes.

[0037] The refractive index Nc of the dielectric layer 23 may be higher than the refractive index Na of the dielectric layer 21 (Nc > Na). If Nc > Na and Nd ≤ Nb, then Nc / Nd > Na / Nb and Nc - Nd > Na - Nb are satisfied. Even if Nd > Nb, it is preferable that Nc > Na is satisfied.

[0038] Also, for example, when light is incident on the laminated film 20 from the substrate 10 side to the laminated film 20 and light of a predetermined wavelength is reflected by the laminated film 20, it is preferable to satisfy Rc < Ra. This is because arranging a reflection surface (interface) with a higher refractive index closer to the light incident surface (lower surface 201) is advantageous for increasing the reflectance of the laminated film 20. Alternatively, when light is incident on the laminated film 20 from the side opposite to the substrate 10 to the laminated film 20 and light of a predetermined wavelength is transmitted through the laminated film 20, it is also preferable to satisfy Rc < Ra. This is because arranging a reflection surface (interface) with a higher refractive index farther from the light incident surface (upper surface 202) is advantageous for increasing the reflectance of the laminated film 20.

[0039] The ratio Nc / Nd of the refractive index Nc of the dielectric layer 23 to the refractive index Nd of the dielectric layer 24 may be lower than the ratio Na / Nb of the refractive index Na of the dielectric layer 21 to the refractive index Nb of the dielectric layer 22 (Nc / Nd < Na / Nb). Satisfying Nc / Nd < Na / Nb is advantageous for satisfying Rc < Ra.

[0040] The difference Nc - Nd between the refractive index Nc of the dielectric layer 23 and the refractive index Nd of the dielectric layer 24 may be lower than the difference Na - Nb between the refractive index Na of the dielectric layer 21 and the refractive index Nb of the dielectric layer 22 (Nc - Nd < Na - Nb). The larger Nc - Nd is, the higher the reflectance Rc becomes.

[0041] The sum Nc + Nd of the refractive index Nc of the dielectric layer 23 and the refractive index Nd of the dielectric layer 24 may be larger than the sum Na + Nb of the refractive index Na of the dielectric layer 21 and the refractive index Nb of the dielectric layer 22 (Nc + Nd > Na + Nb). The smaller Nc + Nd is, the higher the reflectance Rc becomes.

[0042] The refractive index Nc of the dielectric layer 23 may be higher than the refractive index Na of the dielectric layer 21 (Nc < Na). If Nc < Na and Nd ≥ Nb, then Nc / Nd < Na / Nb and Nc - Nd < Na - Nb are satisfied. Even if Nd < Nb, it is preferable to satisfy Nc < Na.

[0043] It is preferable that the absorption of light by the dielectric layers 21, 22, 23, and 24 is small. However, for example, when selecting a material that may cause light absorption in order to satisfy the refractive index relationship with other dielectric layers, the attenuation coefficient of the dielectric layer 21 is Ka, the attenuation coefficient of the dielectric layer 22 is Kb, the attenuation coefficient of the dielectric layer 23 is Kc, and the attenuation coefficient of the dielectric layer 24 is Kd. Here, the attenuation coefficient is for light of a predetermined wavelength handled in the stacked film 20.

[0044] For example, when light is incident on the stacked film 20 from the side opposite to the substrate 10 with respect to the stacked film 20, it is more preferable to satisfy Ka ≥ Kc than to satisfy Ka < Kc. Also, it is more preferable to satisfy Kb ≥ Kd than to satisfy Kb < Kd. This is because arranging a dielectric layer with less absorption closer to the light incident surface (upper surface 202) is advantageous in suppressing light absorption by the stacked film 20.

[0045] For example, when light is incident on the stacked film 20 from the substrate 10 side with respect to the stacked film 20, it is more preferable to satisfy Ka ≤ Kc than to satisfy Ka > Kc. Also, it is more preferable to satisfy Kb ≤ Kd than to satisfy Kb > Kd. This is because arranging a dielectric layer with less absorption closer to the light incident surface (lower surface 201) is advantageous in suppressing light absorption by the stacked film 20.

[0046] Each dielectric layer of the laminated film 20 may have a unique surface shape due to its crystallinity (crystal grain size) and film formation conditions. The dielectric layers of the laminated film 20 are laminated in order from the substrate 10 side. Therefore, the surface shape of each dielectric layer may be a shape that reflects not only the unique surface shape but also the base shape. In the laminated film 20, it is preferable that the interface between two dielectric layers located close to each other is as flat as possible in order to improve optical characteristics. This is because the loss due to scattering of light at the interface can be suppressed. For this reason, it is preferable that the base shape of each dielectric layer is flat. When the surface shape may differ for each dielectric layer, it is more effective to improve the flatness of the surface shape of the lower dielectric layer that is relatively closer to the substrate 10 than to improve the flatness of the surface shape of the upper dielectric layer that is relatively far from the substrate 10. If the height difference of the unevenness of the surface shape unique to the lower dielectric layer is large, the upper dielectric layer formed thereon may have a surface shape with a large height difference that reflects the unevenness of the lower dielectric layer in addition to the surface shape unique to the upper dielectric layer. However, if the height difference of the unevenness of the surface shape of the lower dielectric layer is small, the upper dielectric layer formed thereon can realize a surface shape close to the inherent surface shape of the upper dielectric layer. Therefore, the surface (surface) of the dielectric layer 21 opposite to the substrate 10 is preferably flatter than the surface (surface) of the dielectric layer 23 opposite to the substrate 10. Similarly, the surface (surface) of the dielectric layer 22 opposite to the substrate 10 is preferably flatter than the surface (surface) of the dielectric layer 24 opposite to the substrate 10. For example, the surface roughness of the surface (upper surface 202) of the laminated film 20 opposite to the substrate 10 may be 1.0 nmRMS or more and 3.0 nmRMS or less. For the dielectric layers 21 and 22, a material whose inherent surface shape is flatter than that of the dielectric layers 23 and 24 can be selected.

[0047] The dielectric layers of the laminated film 20 and the substrate 10 may have different densities. The density of the dielectric layer 21 is ρa, the density of the dielectric layer 22 is ρb, the density of the dielectric layer 23 is ρc, and the density of the dielectric layer 24 is ρd. In general, the higher the density of a material, the greater the stress. Also, the greater the physical thickness of a dielectric layer, the greater the stress. The stress of the dielectric layer may cause the dielectric layer to peel off or crack. Therefore, the density of the dielectric layer with a relatively larger physical thickness may be lower than the density of the dielectric layer with a relatively smaller physical thickness. By doing so, the difference in absolute value of the stress can be reduced. This may be suitable when the positive and negative stresses of the two adjacent dielectric layers (positive: tensile stress, negative: compressive stress) are opposite, but may also be effective when the positive and negative stresses of the two adjacent dielectric layers are the same. If the physical thickness of the low refractive index layer is greater than the physical thickness of the high refractive index layer, the density of the low refractive index layer may be lower than the density of the high refractive index layer. For example, the density ρb of the dielectric layer 22 is preferably lower than the density ρa of the dielectric layer 21 (ρb<ρa). The density ρd of the dielectric layer 24 is preferably lower than the density ρc of the dielectric layer 23 (ρd<ρc).

[0048] In addition, in order to suppress cracks and delamination in the stacked film 20, it is also preferable that the density of the upper dielectric layer is lower than that of the lower dielectric layer. Typically, since the substrate 10 is thicker than the stacked film 20, stress tends to increase, so the absolute value of the stress in the lower dielectric layer is preferably larger. For example, the density ρc of the dielectric layer 23 may be lower than the density ρa of the dielectric layer 21 (ρc < ρa). The density ρd of the dielectric layer 24 may be lower than the density ρb of the dielectric layer 22 (ρd < ρb). When the stress of the substrate 10 is not so large, the density of the upper dielectric layer may be higher than that of the lower dielectric layer, and ρc > ρa and / or ρd > ρb may also be acceptable. Each dielectric layer of the stacked film 20 and the substrate 10 may have different melting points from each other. Let the melting point of the dielectric layer 21 be Ma, the melting point of the dielectric layer 22 be Mb, the melting point of the dielectric layer 23 be Mc, and the melting point of the dielectric layer 24 be Md. When forming the dielectric layer by vapor deposition, during the formation of the upper dielectric layer, the temperature of the lower dielectric may rise, but by devising the vapor deposition apparatus, it is preferable to ensure that the melting point of the lower dielectric layer is not exceeded.

[0049] Of the two dielectric layers (high refractive index layer and low refractive index layer) adjacent to each other, the one with the larger physical film thickness tends to have a longer film formation time. Therefore, if the physical film thickness of the low refractive index layer is larger than that of the high refractive index layer, the melting point of the low refractive index layer may be lower than that of the high refractive index layer. For example, it is preferable that the melting point Mb of the dielectric layer 22 is lower than the melting point Ma of the dielectric layer 21 (Mb < Ma). It is preferable that the melting point Md of the dielectric layer 24 is lower than the melting point Mc of the dielectric layer 23 (Md < Mc).

[0050] In addition, it is also preferable that the melting point of the upper dielectric layer is lower than that of the lower dielectric layer. For example, the melting point Mc of the dielectric layer 23 may be lower than the melting point Ma of the dielectric layer 21 (Mc < Ma). The melting point Md of the dielectric layer 24 may be lower than the melting point Mb of the dielectric layer 22 (Md < Mb). For example, when the melting point of the lower layer or the lower dielectric layer is 1000 °C or higher, if the influence of the temperature rise of the lower dielectric during the formation of the upper dielectric layer on film formation is small, Mc > Ma and / or Md > Mb may also be acceptable.

[0051] The dielectric layer 22 may contain a compound of the metal element Mtlb. The metal element Mtlb of the compound contained in the dielectric layer 22 may be a typical element. The dielectric layer 24 may contain a compound of the metal element Mtld. The metal element Mtld of the compound contained in the dielectric layer 22 may be a typical element. The metal element Mtlb of the compound contained in the dielectric layer 22 and the metal element Mtld of the compound contained in the dielectric layer 24 may be the same element (Mtlc=Mtld). The metal element Mtld may be a metal element different from the metal element Mtlc.

[0052] The metal element Mtlb can be a typical element. Also, the metal element Mtld can be a typical element. When comparing compounds in which the nonmetallic element of the compound is the same element, compounds of typical metal elements generally have a lower refractive index than compounds of transition metal elements, and are therefore suitable as materials for low refractive index layers. However, at least one of the metal elements Mtlb and Mtld may be a transition element.

[0053] The compound contained in the dielectric layer 22 is, for example, a compound of a metal element Mtlb and a nonmetal element Ntlb, and is, for example, a boride, a carbide, a nitride, an oxide, a fluoride, a sulfide, a phosphide, or a chloride, and is typically an oxide or a fluoride. The compound contained in the dielectric layer 24 is, for example, a compound of a metal element Mtld and a nonmetal element Ntld, and is, for example, a boride, a carbide, a nitride, an oxide, a fluoride, a sulfide, a phosphide, or a chloride, and is typically an oxide or a fluoride. The nonmetal element Ntld may be the same element as the nonmetal element Ntlb, or the nonmetal element Ntld may be an element different from the metal element Mtlb.

[0054] The dielectric layer 22 may contain a fluoride. The compound contained in the dielectric layer 22 may be a fluoride of a metal element Mtlc. The dielectric layer 24 may contain a fluoride. The compound contained in the dielectric layer 24 may be a fluoride of a metal element Mtld.

[0055] Many metal fluorides have a smaller absorption of ultraviolet light than many metal oxides, and therefore, in an optical component 30 intended to utilize ultraviolet light by transmission or reflection, it is effective in improving the utilization efficiency of ultraviolet light for at least one of the dielectric layers 22, 22 to contain a metal fluoride.

[0056] Each of the dielectric layers 22 and 24 may be made of any of magnesium fluoride (MgF2), aluminum fluoride (AlF3), sodium fluoride (NaF), lithium fluoride (LiF), calcium fluoride (CaF2), barium fluoride (BaF2), strontium fluoride (SrF3), silicon oxide (SiO2), cryolite (Na3AlF6), and thiolite (Na5Al3F 14 ) may contain at least one of the following.

[0057] The compound contained in any of the dielectric layers 21, 22, 23, 24, 25, and 26 may not be a compound of a metal element but may be a compound of silicon. Any of the dielectric layers 21, 22, 23, and 24 may be any of silicon carbide, silicon nitride, and silicon oxide. Furthermore, any of the silicon carbide, silicon nitride, and silicon oxide may be any of silicon oxycarbide, silicon oxycarbide, and silicon oxynitride.

[0058] The substrate 10 has a surface 101 on the side of the laminated film 20 and a back surface 102 on the side opposite the laminated film 20. The surface 101 may be in contact with the laminated film 20. The shape of the back surface 102 may be the same as or different from the shape of the surface 101. The surface 101 may be flatter than the back surface 102.

[0059] The laminated film 20 has a lower surface 201 on the substrate 10 side and an upper surface 202 on the opposite side to the substrate 10. The lower surface 201 of the laminated film 20 may have the same shape as the surface 101 of the substrate 10. The lower surface 201 on the substrate 10 side of the laminated film 20 may be flatter than the upper surface 202 on the opposite side to the substrate 10 of the laminated film 20. The surface roughness of the upper surface 202 of the laminated film 20 on the opposite side to the substrate 10 may be 1.0 nm RMS or more and 3.0 nm RMS or less.

[0060] The dielectric layer 21 has a lower surface 211 on the side of the substrate 10 and an upper surface 212 on the side opposite to the substrate 10. The dielectric layer 23 has a lower surface 231 on the side of the substrate 10 and an upper surface 232 on the side opposite to the substrate 10. The upper surface 212 of the dielectric layer 21 on the side opposite to the substrate 10 may be flatter than the upper surface 232 of the dielectric layer 23 on the side opposite to the substrate 10. The lower surface 211 of the dielectric layer 21 on the side of the substrate 10 may be flatter than the lower surface 231 of the dielectric layer 23 on the side of the substrate 10.

[0061] The substrate 10 may be any of a conductor, a semiconductor, and an insulator. The substrate 10 may be any of a single crystal, a polycrystal, and an amorphous body. The substrate 10 may be a single crystal or a polycrystal. The substrate 10 may be, for example, a polycrystal of a metal, a single crystal of a semiconductor, a polycrystal of a semiconductor, or a single crystal of an insulator. The substrate 10 may contain at least any one of calcium fluoride (CaF2), magnesium fluoride (MgF2), barium fluoride (BaF2), silicon oxide (SiO2), CLEARCERAM (registered trademark), Zerodur (registered trademark), BK7, etc. The substrate 10 may be fluorite. The substrate 10 may be glass or plastic.

[0062] The laminated film 20 may include a dielectric layer 25. The dielectric layer 21, the dielectric layer 22, the dielectric layer 23, and the dielectric layer 24 are provided between the dielectric layer 25 and the substrate 10. The refractive index Ne of the dielectric layer 25 may be lower than the refractive index Nc of the dielectric layer 23 (Ne < Nc). The refractive index Ne of the dielectric layer 25 may be higher than the refractive index Nd of the dielectric layer 24 (Ne > Nd). The composition of the dielectric layer 25 and the composition of the dielectric layer 24 may be different from each other.

[0063] The dielectric layer 25 may contain a compound of a metal element Mtle. The metal element Mtle of the compound contained in the dielectric layer 25 may be a typical element. The metal element Mtle of the compound contained in the dielectric layer 25 and the metal element Mtld of the compound contained in the dielectric layer 24 may be the same element (Mtle = Mtld). The metal element Mtle may be a different metal element from the metal element Mtld.

[0064] The compound contained in the dielectric layer 25 is, for example, a compound of a metal element Mtle and a nonmetal element Ntle, such as a boride, carbide, nitride, oxide, fluoride, sulfide, phosphide, or chloride, typically an oxide or fluoride. The nonmetal element Ntle may be the same element as the nonmetal element Ntld, or the nonmetal element Ntle may be an element different from the metal element Mtld.

[0065] The dielectric layer 25 may contain at least one of magnesium fluoride, aluminum fluoride, sodium fluoride, lithium fluoride, calcium fluoride, barium fluoride, strontium fluoride, silicon oxide, cryolite, and thiolite.

[0066] The laminated film 20 may include a dielectric layer 26. The dielectric layer 21, the dielectric layer 22, the dielectric layer 23, and the dielectric layer 24 are provided between the dielectric layer 26 and the substrate 10. The refractive index Nf of the dielectric layer 26 may be higher than the refractive index Ne of the dielectric layer 25 (Nf>Ne). The composition of the dielectric layer 26 and the composition of the dielectric layer 23 may be the same as each other.

[0067] The dielectric layer 26 may contain a compound of the metal element Mtlf. The metal element Mtlf of the compound contained in the dielectric layer 26 may be a transition element. The metal element Mtlf of the compound contained in the dielectric layer 26 and the metal element Mtlc of the compound contained in the dielectric layer 23 may be the same element (Mtlf=Mtlc). The metal element Mtlf may be a metal element different from the metal element Mtlc.

[0068] The compound contained in the dielectric layer 26 is, for example, a compound of a metal element Mtlf and a nonmetallic element Ntlf, such as a boride, carbide, nitride, oxide, fluoride, sulfide, phosphide, or chloride, and is typically an oxide or fluoride.

[0069] The dielectric layer 23 may contain at least one of neodymium fluoride, lanthanum fluoride, gadolinium fluoride, samarium fluoride, cerium fluoride, ytterbium fluoride, and aluminum oxide.

[0070] 3(a) shows a more preferred embodiment of the optical component 30. The laminated film 20 includes a dielectric layer group 27 and a dielectric layer group 28. The dielectric layer group 27 is provided between the dielectric layer group 28 and the substrate 10. The laminated film 20 may further include a dielectric layer group 29. The dielectric layer group 28 is provided between the dielectric layer group 27 and the dielectric layer group 29.

[0071] The dielectric layer group 27 includes i (i≧2) dielectric layers 21 (dielectric layers 21-1 to 21-i). Each of the i dielectric layers 21 in the dielectric layer group 27 contains at least two elements contained in one of the i dielectric layers 21 (e.g., dielectric layer 21-2).

[0072] The dielectric layer group 27 includes i dielectric layers 22 (dielectric layers 22-1 to 22-i). The i dielectric layers 22 of the dielectric layer group 27 contain at least two elements contained in one of the i dielectric layers 22 (e.g., dielectric layer 22-2). When the i dielectric layers 21 and the i dielectric layers 22 are alternately stacked in the dielectric layer group 27, i≧2.

[0073] The dielectric layer group 28 includes j dielectric layers 23 (dielectric layers 23-1 to 23-j) (j≧2). Each of the j dielectric layers 23 in the dielectric layer group 28 contains at least two elements contained in one of the j dielectric layers 23 (e.g., dielectric layer 23-2). The dielectric layer group 28 includes j dielectric layers 24 (dielectric layers 24-1 to 24-j). Each of the j dielectric layers 24 in the dielectric layer group 28 contains at least two elements contained in one of the j dielectric layers 24 (e.g., dielectric layer 24-2). When the j dielectric layers 23 and the j dielectric layers 24 are alternately stacked in the dielectric layer group 28, j≧2.

[0074] It is preferable that the value of i and the value of j do not differ extremely. Specifically, it is preferable to satisfy 0.2 ≦ i / j ≦ 5. It is preferable to satisfy i ≦ j, and it is more preferable to satisfy i < j. This is because the dielectric layer group 27 is closer to the substrate 10 than the dielectric layer group 28, so it is less affected by the shape of the base. In order to realize a wavelength dependence with a narrower bandwidth, it is preferable to satisfy at least one of i ≧ 3 and j ≧ 3, and it is more preferable to satisfy at least one of i ≧ 10 and j ≧ 10. In order to simplify the film formation process and reduce the film thickness of the laminated film 20, it is preferable to satisfy i ≦ 30 and j ≦ 30.

[0075] The dielectric layer group 28 includes one dielectric layer 25 and two dielectric layers 26 (dielectric layers 26-1 and 26-2). The dielectric layer 25 is provided between the dielectric layer 26-1 and the dielectric layer 26-2.

[0076] The optical component 30 is applicable to various optical devices EQP. Examples of the optical device EQP equipped with the optical component 30 include a camera lens, a telescope, a projector, an exposure device, a measuring instrument, etc. In particular, it is suitable for optical devices equipped with a light source such as a projector, an exposure device, and a measuring instrument. This is because the laminated film 20 of the optical component 30 can be designed according to the wavelength of the light source so that the optical component 30 transmits and / or reflects the light from the light source. The light from the light source may be any of infrared light, visible light, and ultraviolet light. Since many metal fluorides have less absorption of ultraviolet light than other metal compounds, it is suitable when the light source is ultraviolet light.

[0077] FIG. 4 shows a schematic diagram of an exposure apparatus as an example of the optical apparatus EQP. The optical apparatus EQP, which is an exposure apparatus, includes a light source 1 and mirrors 2 and 3 that constitute an illumination optical system. The optical apparatus EQP also includes a reticle stage 5 that supports a reticle 4, a projection optical system 6 that projects the pattern of the reticle 4, and a substrate stage 8 that supports a substrate 7. Exposure light 9 from the light source 1 is reflected by the mirrors 2 and 3 of the illumination optical system and guided to the reticle 4, and the exposure light 9 with the pattern of the reticle 4 is collected by the projection optical system 6 and projected onto the substrate 7. The pattern formed on the reticle 4 by the light source 1 and the optical component 30 is projected onto the substrate 7. The substrate 7 is coated with a photoresist, and the photoresist is exposed by the exposure light 9. The substrate 7 may be a semiconductor wafer or a glass substrate for an FPD (flat panel display). The exposure light of the exposure apparatus is typically ultraviolet light. The wavelength of the exposure light is 436 nm for a g-line light source and about 365 nm for an i-line light source. The wavelength of the exposure light is about 248 nm for a KrF excimer laser light source, about 193 nm for an ArF excimer laser light source, and 10 to 20 nm for an EUV (extreme ultraviolet) light source. Here, an example in which the optical component 30 is used for the mirrors 2 and 3 of the illumination optical system has been shown, but the optical component 30 may also be used for the lens of the projection optical system. Also, the projection optical system may be configured with a mirror, and the optical component 30 may be used for this mirror. The projection optical system may be a reduced projection type, a unity projection type, or an enlarged projection type. Here, a transmissive reticle 4 has been exemplified, but a reflective reticle 4 may also be used. The projection optical system may be a refractive type using a lens, or a reflective type using a mirror. The optical component 30 may be used for the mirror of a reflective reduced projection optical system provided in an exposure apparatus equipped with an EUV light source. EXAMPLES

[0078] Semiconductor exposure equipment reflects the excimer laser emitted from the light source with mirrors and refracts it with lenses, controlling the optical path to reduce and project the fine pattern formed on the reticle onto the silicon wafer. The light source used is a KrF excimer laser with a wavelength of approximately 248 nm or an ArF excimer laser with a wavelength of approximately 193 nm.

[0079] The mirror used here is formed of a laminated film in which high and low refractive index layers are alternately laminated on a substrate, and the reflectance is increased by utilizing the interference of light. In this case, the greater the difference between the refractive index of the high refractive index material and that of the low refractive index material, the higher the reflectance of the mirror can be obtained. Metal fluorides are suitable for the high and low refractive index layers of mirrors for ultraviolet lasers because they have low absorption of ultraviolet light and high laser resistance. For example, LaF3 (lanthanum fluoride), GdF3 (gadolinium fluoride), NdF3 (neodymium fluoride), etc. are candidates for high refractive index metal fluorides. AlF3 (aluminum fluoride), MgF2 (magnesium fluoride), etc. are candidates for low refractive index metal fluorides.

[0080] For example, a possible configuration is to stack 20 pairs of alternating layers of LaF3 and AlF3 on a substrate, and then stack LaF3, MgF2, and LaF3 on top of them. With this configuration, a theoretical reflectance of 99% or more can be obtained at 193 nm. However, LaF3 used as the high refractive index layer has crystallinity, and the roughness of the interface and surface of the laminated film becomes too large to be ignored, especially when the film is formed by vacuum deposition. If the interface and surface roughness are large, the laser light is scattered, making it difficult to obtain the theoretical reflectance characteristics. As a result, the reflectance of the mirror actually manufactured is several percent lower than the theoretical reflectance. This is also the case when other materials such as GdF3 and NdF3 are used for the high refractive index film.

[0081] Therefore, in this embodiment, an optical component that can be used as a mirror for an ArF excimer laser with an oscillation wavelength of 193 nm and an ultraviolet laser with a light beam incident angle of 45 degrees will be described. It should be noted that the present invention is not limited to this embodiment.

[0082] The substrate used was a fluorite (CaF2) substrate measuring 35 mm x 47 mm x 5 mmt, which had been polished to a surface roughness of 0.8 nm RMS or less. Note that the surface roughness in this example was measured using an atomic force microscope (AFM) at 512 points x 512 points in a mesh pattern over an area of ​​1 μm x 1 μm.

[0083] On the fluorite substrate, M pairs (0≦M≦24) of pairs each consisting of an ytterbium fluoride layer (hereinafter referred to as YbF3) and an aluminum fluoride layer (hereinafter referred to as AlF3) are laminated. On top of that, L pairs (L=24-M) of pairs each consisting of a lanthanum fluoride layer (hereinafter referred to as LaF3) and AlF3 are laminated. On top of that, LaF3, a magnesium fluoride layer (hereinafter referred to as MgF2), and LaF3 are laminated in this order. In this way, a laminated film consisting of 51 dielectric layers in total is formed. The 1st to nth layers are composed of M pairs (M=n / 2) of YbF3 / AlF3, and the n+1th to 48th layers are composed of L pairs (L=24-M=24-n / 2) of LaF3 / AlF3.

[0084] In this embodiment, a vacuum deposition apparatus was used to form the metal fluoride film. Note that the present invention is not limited to the vacuum deposition method, but can also be applied to known physical deposition methods (molecular beam deposition, ion plating, ion beam deposition, sputtering, etc.).

[0085] The vacuum deposition apparatus used in this embodiment will be outlined below. Four containers (molybdenum boats) in the vacuum chamber were filled with YbF3 as deposition material α, AlF3 as deposition material β, LaF3 as deposition material γ, and MgF2 as deposition material δ. The four deposition materials were installed in a concentric manner with a radius of 250 mm from the substrate revolution axis located at the center of the chamber, and each was provided with a resistance heating mechanism. The substrate was fixed to a substrate holder and revolved at a height of 1100 mm from the deposition material. The rotation and revolution here means that the substrate rotates around the substrate rotation axis while simultaneously revolving around the substrate revolution axis. It was designed to rotate 2.54 times during one revolution. A shielding mask was installed 100 mm below the substrate, and was processed into a pre-designed shape so that a film could be formed on the substrate with a uniform film thickness. During film formation, the substrate could be heated by a substrate heating mechanism. The deposition rate is monitored by a film thickness monitor placed at the center of the substrate revolution plane, and a mechanism is provided for controlling the current value of the resistance heating so that the deposition rate is constant.

[0086] During film formation, the pressure in the vacuum chamber was 5.0×10 -5 The pressure was set at 100 Pa, and the substrate temperature was 280°C. The deposition materials were sequentially deposited to the prescribed thicknesses to achieve the film design shown in Table 1. The deposition rates of YbF3, AlF3, LaF3, and MgF2 were controlled to 0.6 nm / sec, 0.2 nm / sec, 0.2 nm / sec, and 0.2 nm / sec, respectively. All of the dielectric layers of YbF3, LaF3, AlF3, and MgF2 have tensile stress.

[0087] The theoretical density of LaF3 is 5.9 g / cm 3 The theoretical density of AlF3 is 2.9 g / cm 3 , the density (theoretical density) of MgF2 is 3.2g / cm 3 and the theoretical density of YbF3 is 8.2 g / cm 3 The melting point of LaF3 is 1490°C, that of AlF3 is 1040°C, that of MgF2 is 1248°C, and that of YbF3 is 1159°C.

[0088] The refractive index of LaF3, AlF3, MgF2, and YbF3 formed under the above film forming conditions is 1.69, 1.41, 1.44, and 1.68, respectively. These refractive indices are for light with a wavelength of 193 nm.

[0089] The refractive index of each material was calculated as follows. A single layer of each material was formed with a thickness of 50 to 100 nm on a fluorite substrate with a diameter of 15 mm and a thickness of 2 mm. The reflectance was measured with a spectrometer at a wavelength range of 180 nm to 240 nm with a light incidence angle of 15 degrees. The reflectance was calculated using the optical thin film analysis and design software FilmWizard. TM The refractive index of the single layer film was calculated using the following equation.

[0090] When YbF3 is deposited by vacuum deposition, the refractive index is about 1.63 at a standard deposition rate. However, the inventors have found after extensive research that the refractive index for a wavelength of 193 nm can be increased to 1.65 or more, for example, 1.68, by increasing the deposition rate. The inventors have found that YbF3 with a refractive index of 1.68 can be formed by depositing YbF3 at 0.6 nm / sec in a deposition device with a standard deposition rate of 0.2 nm / sec. It is not clear why the refractive index increases significantly when the deposition rate is increased in the vacuum deposition of YbF3, but it is speculated that this is because the inclusion of impurities can be suppressed by depositing the film at a high speed. Therefore, in an optical component including a substrate and an ytterbium fluoride layer provided on the substrate, the refractive index of the ytterbium fluoride layer for light with a wavelength of 193 nm can be increased to 1.65 or more. The refractive index of the ytterbium fluoride layer for light of a wavelength of 193 nm may be less than 1.69.

[0091] The surface roughness of various metal fluorides may depend on the type of compound. For example, the surface roughness of LaF3, which is used as a high refractive index material (refractive index 1.50 or more), is 5.8 nmRMS, the surface roughness of GdF3 is 6.3 nmRMS, the surface roughness of SmF3 is 8.9 nmRMS, and the surface roughness of YbF3 is 1.1 nmRMS. The surface roughness of AlF3, which is used as a low refractive index material (refractive index 1.50 or less), is 0.9 nmRMS, and the surface roughness of MgF2 is 2.2 nmRMS. In all cases, the same deposition apparatus was used, the substrate was positioned so that the deposition particles were deposited at an incident angle of 70° with respect to the substrate, and a single layer film of 100 nm thickness was formed, and the surface roughness (Rms) of the single layer film was measured by AFM.

[0092] Generally, metal fluorides are crystalline, and therefore the crystal grains cause large surface roughness. Furthermore, AlF3 is exceptionally amorphous, and therefore has small roughness. It can be seen that the high refractive index materials LaF3, GdF3, and SmF3 have large roughness (over 3.0 nm RMS). It can also be seen that YbF3, although a high refractive index material, has a small roughness at the same level as AlF3, which is exceptionally amorphous among metal fluorides. It is assumed that high refractive index metal fluoride materials not listed here also have large surface roughness, since they are crystalline films like LaF3, GdF3, and SmF3. In this way, it can be seen that YbF3 has the unique characteristic of being very smooth among metal fluoride high refractive index materials.

[0093] We investigated the number of pairs M and the number of layers n when YbF3 with a refractive index of 1.68 was used as the high refractive index layer. YbF3 is a high refractive index layer with a small roughness, but its refractive index is less than that of LaF3, which is 1.69. Therefore, it is necessary to make a laminated film by effectively combining YbF3 and LaF3. Specifically, YbF3 was used for the high refractive index layer of the laminated film near the substrate where the amount of light reaching is relatively small, and LaF3 was used for the high refractive index layer of the laminated film on the air side where the amount of light is large. With this configuration, the roughness of the entire laminated film mirror can be suppressed by inserting YbF3 with a small roughness near the substrate, and the theoretical reflectance is increased by using LaF3 for the layer on the air side, and a mirror with a high reflectance can be obtained.

[0094] Table 1 shows film configurations of types A to C in which the number of YbF3 / AlF3 alternating layers and the number of LaF3 / AlF3 alternating layers are changed.

[0095] [Table 1]

[0096] (Type A) On the fluorite substrate, n / 2 pairs of LaF3 and AlF3, 24-n / 2 pairs of LaF3 and AlF3, and then LaF3, MgF2, and LaF3 are laminated on top of that in that order. The physical thickness of each layer at 193 nm is shown in Table 1. The physical thickness of each layer is set so that the optical thickness is 26 to 29% of 193 nm.

[0097] (Type B) On a fluorite substrate, 24 pairs of LaF3 and AlF3 were layered, and on top of that, LaF3, MgF2, and LaF3 were layered in that order. The physical film thickness of each layer at 193 nm is shown in Table 1. In type B, each layer was formed under the same conditions as the same film type in type A.

[0098] (Type C) On a fluorite substrate, 24 pairs of YbF3 and AlF3 are layered, and on top of that, LaF3, MgF2, and LaF3 are layered in that order. The physical film thickness of each layer at 193 nm is shown in Table 1. In type B, each layer was formed under the same conditions as the same film type in type A.

[0099] (evaluation) Table 2 shows the results of comparing the reflectance and surface roughness of optical components of types A, B, and C. Table 2 lists the characteristics when the value of n is changed for type A. Figure 3 (c) also shows the reflectance characteristics of types A and B. At a wavelength of 193 nm, the type A mirror achieves a reflectance that is approximately 0.7% higher than that of type B. The reflectance of the mirror was measured using a spectrometer at a light incidence angle of 45 degrees.

[0100] [Table 2] Comparing type A and type B, type B has a larger difference between the high refractive index layer and the low refractive index layer, so theoretically type B can obtain a higher reflectance. However, when the roughness of the outermost surface of both is measured by AFM, it is 3.1 nmRMS for type B and 2.4 nmRMS for type A. Therefore, in type A, the surface roughness of the laminated film on the side opposite the substrate is 1.0 nmRMS or more and 3.0 nmRMS or less. Type B has a larger roughness and scattering loss. Therefore, even though type B has a higher theoretical reflectance, type A, which was able to suppress the roughness, is considered to have a higher actual reflectance. This is probably due to the fact that YbF3 has a smaller roughness than other high refractive index films of metal fluorides.

[0101] When the refractive index is 1.63, simply replacing the high refractive index layer from LaF3 to YbF3 does not result in a reflectance that exceeds that of type B even if the roughness is small, but if it can be improved to 1.68, a reflectance higher than that of type B can be obtained depending on the combination of materials for the dielectric layers. With the combination of dielectric layers shown in type A, a reflectance equal to or higher than that of type B was achieved. On the other hand, type C, in which all 48 pairs were YbF3 / AlF3 alternating layers, had small roughness but low reflectance.

[0102] According to this embodiment, the roughness of the interface and surface in the laminated film can be reduced, and as a result, a mirror for an ultraviolet laser having a high reflectance can be provided.

[0103] The above-described embodiments can be appropriately modified without departing from the technical concept. The disclosure of this specification includes not only what is described in this specification, but also all matters that can be understood from this specification and the drawings attached to this specification.

[0104] Furthermore, the disclosure of this specification includes the complement of each concept described in this specification. In other words, if this specification contains a statement that "A is greater than B," for example, even if the statement that "A is not greater than B" is omitted, this specification can be said to disclose that "A is not greater than B." This is because when a statement that "A is greater than B" is made, it is assumed that the case in which "A is not greater than B" is taken into consideration. [Explanation of symbols]

[0105] 10 Base 20 Laminated Film 21~24 Dielectric layers

Claims

1. A substrate; a laminated film including a first layer group provided on the substrate and a second layer group provided between the first layer group and the substrate; Equipped with In the second layer group, first dielectric layers and second dielectric layers are alternately stacked, In the first layer group, third dielectric layers and fourth dielectric layers are alternately stacked, the refractive index of the first dielectric layer is higher than the refractive index of the second dielectric layer; the refractive index of the third dielectric layer is higher than the refractive index of the fourth dielectric layer; (i) the refractive index of the third dielectric layer is higher than the refractive index of the first dielectric layer; (ii) a difference between the refractive index of the third dielectric layer and the refractive index of the fourth dielectric layer is greater than a difference between the refractive index of the first dielectric layer and the refractive index of the second dielectric layer; At least one of the following is satisfied: An optical component, wherein the first dielectric layer contains ytterbium fluoride.

2. The optical component according to claim 1 , wherein the first dielectric layer contains a compound of a first metal element, and the third dielectric layer contains a compound of a second metal element different from the first metal element.

3. the first metallic element is a rare earth element; The second metal element is a rare earth element. The optical component according to claim 2 .

4. the first dielectric layer contains a fluoride; the third dielectric layer contains a fluoride; The optical component according to claim 1 .

5. the third dielectric layer contains at least one of neodymium fluoride, lanthanum fluoride, gadolinium fluoride, samarium fluoride, cerium fluoride, and aluminum oxide; 3. The optical component according to claim 1 or 2.

6. the second dielectric layer contains a compound of a metal element; The optical component according to claim 1 , wherein the fourth dielectric layer contains a compound of a metal element.

7. the metal element of the compound contained in the second dielectric layer is a typical element, The optical component according to claim 6 , wherein the metal element of the compound contained in the fourth dielectric layer is a typical element.

8. the second dielectric layer contains a fluoride; 8. The optical component according to claim 1, wherein the fourth dielectric layer contains a fluoride.

9. 7. The optical component according to claim 1, wherein each of the second dielectric layer and the fourth dielectric layer contains at least one of magnesium fluoride, aluminum fluoride, sodium fluoride, lithium fluoride, calcium fluoride, barium fluoride, strontium fluoride, silicon oxide, cryolite, and thiolite.

10. 10. The optical component according to claim 1, wherein a surface of the first dielectric layer opposite to the substrate is flatter than a surface of the third dielectric layer opposite to the substrate.

11. The laminated film includes i (i≧2) dielectric layers each containing at least two elements contained in the first dielectric layer, and the laminated film includes j (j≧2) dielectric layers each containing at least two elements contained in the third dielectric layer, The optical component according to claim 1 , wherein 0.2≦i / j≦5 is satisfied.

12. A substrate; a laminated film including a first layer group provided on the substrate and a second layer group provided between the first layer group and the substrate; Equipped with In the second layer group, first dielectric layers and second dielectric layers are alternately stacked, In the first layer group, third dielectric layers and fourth dielectric layers are alternately stacked, the refractive index of the first dielectric layer is higher than the refractive index of the second dielectric layer; the refractive index of the third dielectric layer is higher than the refractive index of the fourth dielectric layer; (i) the refractive index of the third dielectric layer is higher than the refractive index of the first dielectric layer; (ii) a difference between the refractive index of the third dielectric layer and the refractive index of the fourth dielectric layer is greater than a difference between the refractive index of the first dielectric layer and the refractive index of the second dielectric layer; At least one of the following is satisfied: An optical component, characterized in that a surface of the first dielectric layer opposite to the substrate is flatter than a surface of the third dielectric layer opposite to the substrate.

13. 13. The optical component according to claim 1, wherein the surface of the laminated film opposite to the substrate has a surface roughness of 1.0 nm RMS or more and 3.0 nm RMS or less.

14. A substrate; a laminated film including a first layer group provided on the substrate and a second layer group provided between the first layer group and the substrate; Equipped with In the second layer group, first dielectric layers and second dielectric layers are alternately stacked, In the first layer group, third dielectric layers and fourth dielectric layers are alternately stacked, the refractive index of the first dielectric layer is higher than the refractive index of the second dielectric layer; the refractive index of the third dielectric layer is higher than the refractive index of the fourth dielectric layer; (i) the refractive index of the third dielectric layer is higher than the refractive index of the first dielectric layer; (ii) a difference between the refractive index of the third dielectric layer and the refractive index of the fourth dielectric layer is greater than a difference between the refractive index of the first dielectric layer and the refractive index of the second dielectric layer; At least one of the following is satisfied: An optical component, characterized in that the surface of said laminated film opposite to said substrate has a surface roughness of 1.0 nm RMS or more and 3.0 nm RMS or less.

15. The laminated film includes a fifth dielectric layer, the first dielectric layer, the second dielectric layer, the third dielectric layer and the fourth dielectric layer are provided between the fifth dielectric layer and the substrate; (d) the refractive index of the fifth dielectric layer is lower than the refractive index of the third dielectric layer and higher than the refractive index of the fourth dielectric layer; and (e) the fifth dielectric layer contains magnesium fluoride; The optical component according to claim 1 , which satisfies at least one of the above.

16. 16. The optical component according to claim 1, wherein the substrate is monocrystalline or polycrystalline.

17. 17. The optical component according to claim 1, wherein the substrate contains calcium fluoride.

18. A light source and an optical component according to any one of claims 1 to 17, An optical device, characterized in that the optical component transmits and / or reflects light from the light source.

19. 20. The optical instrument of claim 18, wherein the light is ultraviolet light.

20. 20. An optical apparatus according to claim 18 or 19, comprising a first stage for supporting a reticle and a second stage for supporting a substrate, the optical apparatus projecting a pattern formed by the light source, the optical component and the reticle onto the substrate.

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