JP2006170916A - Optical element and projection exposure device using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical element showing an excellent reflection characteristic over a long period in use under an extreme ultraviolet ray. <P>SOLUTION: An upper layer 32 is formed from an oxidation-resistant metal or a metal material including it. To put it concretely, the upper layer 32 includes as a main component at least one kind of materials produced by adding gold, silver copper or the like to a group comprising ruthenium, rhodium and platinum. Hereby, the upper layer 32 performs a role as an oxidation prevention film. A lower layer 31 inserted between the upper layer 32 and a multilayered film 20 has a double structure comprising two or more diffusion prevention layers, and prevents a component metal constituting the upper layer 32 from diffusing to the multilayered film 20 side. Hereby, deterioration of the oxidation-resistant property of the upper layer 32 which is the outermost surface of this optical element 40 can be prevented, to thereby maintain the reflection characteristic of the optical element 40 over a long period. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a reflective optical element used for extreme ultraviolet rays and the like, and a projection exposure apparatus using the same.

In recent years, with the miniaturization of semiconductor integrated circuits, in order to improve the resolution of an optical system achieved by the light diffraction limit, extreme ultraviolet rays having a shorter wavelength (11 to 14 nm) are used instead of conventional ultraviolet rays. The exposure technology that has been developed has been developed. This is expected to enable exposure with a pattern size of about 5 to 70 nm. However, since the refractive index of the material in this region is close to 1, it is impossible to use a transmission refraction type optical element as in the past. A reflective optical element is used. The mask used in the projection exposure apparatus is also a normal reflection type optical element from the viewpoint of securing transmittance. At this time, in order to achieve a high reflectance in the optical element, it is common to form a reflective surface by alternately laminating a substance having a high refractive index and a substance having a low refractive index on the substrate in the wavelength range of use. (See Patent Document 1).
Japanese Patent Laid-Open No. 2003-14893

  When the optical element as described above is used under extreme ultraviolet rays in the projection exposure apparatus, the environment is a vacuum, but oxygen, moisture and organic substances cannot be completely excluded from the periphery of the optical element. On the other hand, extreme ultraviolet light has very large energy. At this time, oxygen, moisture, and the substance on the surface of the optical element are irradiated with extreme ultraviolet rays to cause an oxidation reaction. Further, when an organic substance and a substance on the surface of the optical element are irradiated with extreme ultraviolet rays, photochemical vapor deposition (photo CVD) occurs, and a carbon film is generated on the surface of the optical element. Due to such a phenomenon, the reflection characteristic of the optical element deteriorates, and there arises a problem that the life of the projection exposure apparatus is shortened by extension of the optical element.

  Therefore, an object of the present invention is to provide an optical element that exhibits good reflection characteristics over a long period of time when used in extreme ultraviolet light or the like.

  Another object of the present invention is to provide a projection exposure apparatus in which the above optical element is incorporated as a projection optical system for extreme ultraviolet rays.

  In order to solve the above problems, an optical element according to a first invention includes (a) a supporting substrate, (b) a multilayer film that is supported on the substrate and reflects extreme ultraviolet rays, and (c- 1) a lower protective layer provided on the outermost layer of the multilayer film and including two or more diffusion prevention layers; and (c-2) an upper protective layer provided on the lower layer; Is provided. In the above optical element, the multilayer film has, for example, a first layer made of a material having a small refractive index difference with respect to the refractive index of vacuum in an extreme ultraviolet region and a second layer made of a material having a large refractive index difference on the substrate. Alternating layers are formed.

  In the present invention, the optical element is a reflective element having a multilayer film, and has good reflection characteristics against extreme ultraviolet rays and the like. In the present invention, a composite protective layer having a lower layer including two or more diffusion prevention layers and an upper layer provided on the lower layer is provided on the outermost layer of the multilayer film. In this case, the upper layer serves to protect the multilayer film from a substance existing around the optical element, that is, a chemical substance remaining in a vacuum in the projection exposure apparatus, and includes a lower layer including two or more diffusion prevention layers. Has a role of preventing the composition of the upper layer (for example, metal in the upper layer) from diffusing to the multilayer film side. In particular, in this optical element, since the lower layer includes two or more diffusion prevention layers, a single layer indicates that the composition of the upper layer diffuses to the multilayer film side due to a phenomenon such as an energy barrier being generated between the diffusion prevention layers. Therefore, the function of the upper layer can be maintained for a long time. As a result, it is possible to prevent deterioration of the multilayer film due to oxidation, composition change, etc. on the surface of the optical element and its vicinity, that is, a decrease in reflectance, and as a result, it is possible to keep the reflection characteristics of the entire optical element good for a long time it can. The “composite protective layer” described above is sufficiently thin or has low light absorption to transmit extreme ultraviolet rays to a desired degree.

  In the optical element according to the second invention, in the optical element according to the first invention, the upper layer contains at least one of an oxidation-resistant substance and a catalytic substance. Here, the “oxidation-resistant substance” means a substance having a property of suppressing an oxidation reaction caused by moisture, oxygen, or the like. The “catalytic substance” means a substance having a positive catalytic action that increases a reaction rate at which carbon in an organic substance is converted to carbon dioxide or the like. For example, when the upper layer contains an oxidation-resistant substance (metal, compound, etc.), it is possible to suppress an oxidizing action in which the optical element is eroded from the surface by moisture or oxygen present around the optical element. On the other hand, when the upper layer contains a catalytic substance (metal, compound, etc.), carbon contained in an organic substance present around the optical element is efficiently converted into a gas such as carbon dioxide by positive catalytic action. Therefore, the generation of a carbon film on the surface of the optical element can be suppressed.

  Further, in the optical element according to the third invention, in the optical element according to the first and second inventions, the diffusion preventing layer is made of silicon dioxide, zirconium dioxide, niobium oxide, niobium dioxide, niobium pentoxide, molybdenum dioxide, oxidized The main component is at least one selected from the group consisting of chromium, dichromium trioxide, chromium trioxide, carbon tetraboride, alumina, carbon, silicon carbide, silicon nitride, boron nitride, molybdenum silicide, and chromium. In this case, the composition of the upper layer in the upper layer, that is, the oxidation-resistant substance, the catalytic substance, and the like can be reliably prevented from diffusing to the multilayer film side. When the diffusion preventing layer is an oxide, the diffusion preventing layer is likely to be chemically and structurally stable.

  When the upper layer contains as a main component at least one selected from the group consisting of ruthenium, rhodium, platinum, gold, silver, niobium, palladium and the like, these are oxidation-resistant metals, and block of the diffusion prevention layer Protects the multilayer film from moisture, oxygen and the like held on the surface. Further, when the upper layer contains as a main component at least one selected from the group consisting of nickel, palladium, platinum, silver, ruthenium, rhodium, etc., these are catalytic metals and block the diffusion preventing layer To suppress the generation of a carbon film on the surface of the optical element.

  The upper layer is made of silicon dioxide, zirconium dioxide, niobium oxide, niobium dioxide, niobium pentoxide, molybdenum dioxide, alumina, chromium oxide, dichromium trioxide, chromium trioxide, ruthenium dioxide, ruthenium trioxide, tetraoxide. When containing as a main component at least one selected from the group consisting of ruthenium, dirhodium trioxide, rhodium dioxide, carbon, silicon carbide, silicon nitride, boron nitride, molybdenum silicide, etc., these are oxidation resistant materials, The multilayer film is protected from moisture and oxygen by being held on the surface by the block of the diffusion preventing layer. On the other hand, when the upper layer contains titanium oxide or the like as a main component, these are catalytic materials, and are prevented from being formed on the surface of the optical element by being held on the surface by the block of the diffusion prevention layer. To do.

  A projection exposure apparatus according to a fourth aspect of the invention includes (a) a light source that generates extreme ultraviolet light, (b) an illumination optical system that guides the extreme ultraviolet light from the light source to a transfer mask, and (c) a mask. A projection optical system for forming the pattern image on the sensitive substrate. In the projection exposure apparatus, at least one of the mask, the illumination optical system, and the projection optical system includes the optical element according to the first to third aspects of the invention.

  In the projection exposure apparatus, by using any one of the optical elements described above, the reflectance of the optical element is reduced due to oxidation, carbon film formation, composition change, etc. on the surface of the optical element and its vicinity. Therefore, the reflection characteristics of the optical element can be maintained over a long period of time, and the projection exposure apparatus can have a long life.

[First Embodiment]
FIG. 1 is a cross-sectional view showing the structure of the optical element according to the first embodiment. The optical element 40 of this embodiment is, for example, a concave reflecting mirror, and includes a substrate 10 that supports a multilayer structure, a reflective multilayer film 20, and a composite protective layer 30 that is a surface layer. Among these, the composite protective layer 30 is a film in which a lower layer 31 having a multilayer structure and an upper layer 32 having a single layer structure are laminated as will be described later.

  The substrate 10 is formed by processing, for example, synthetic quartz glass or low expansion glass, and its upper surface 10a is polished to a mirror surface with a predetermined accuracy. The upper surface 10a can be a concave surface as shown in the figure, but can be a convex surface, a flat surface, a multi-surface, or other shapes depending on the application of the optical element 40.

The multilayer film 20 is a reflective film composed of several to several hundred thin films formed by, for example, alternately laminating two kinds of substances having different refractive indexes on the substrate 10. The multilayer film 20 is formed by laminating a large number of materials with low absorption in order to increase the reflectance of the optical element 40 that is a reflecting mirror, and based on the optical interference theory so that the phases of the reflected waves are matched. The thickness of each layer is adjusted. That is, the thin film layer L1 having a relatively low refractive index and the thin film layer L2 having a relatively high refractive index are reflected on the substrate 10 with respect to the wavelength region of extreme ultraviolet rays used in the projection exposure apparatus. The multilayer film 20 is formed by stacking alternately or in an arbitrary order with a predetermined film thickness so that the phases are matched. The two types of thin film layers L1 and L2 constituting the multilayer film 20 can be a molybdenum layer and a silicon layer, respectively. The order in which the thin film layers L1 and L2 are stacked and the condition of which thin film layer is the uppermost layer can be changed as appropriate according to the application of the optical element 40. The material of the thin film layers L1 and L2 is not limited to the combination of molybdenum and silicon. For example, the multilayer film 20 can be formed by appropriately combining a material such as molybdenum, ruthenium, or rhodium with a material such as silicon, beryllium, or carbon tetraboride (B ₄ C).

In the multilayer film 20, a boundary film (not shown) can be further provided between the thin film layer L1 and the thin film layer L2. In particular, when metal, silicon, or the like is used as the thin film layers L1 and L2 forming the multilayer film 20, the materials forming the respective materials are mixed in the vicinity of the boundary between the thin film layer L1 and the thin film layer L2, and the interface is ambiguous. It is easy to become. Thereby, the reflection characteristic is affected, and the reflectance of the optical element 40 may be lowered. Therefore, in order to clarify the interface, a boundary film is further provided between the thin film layer L1 and the thin film layer L2 when the multilayer film 20 is formed. As a material, for example, B ₄ C or C, molybdenum carbide (MoC), molybdenum dioxide (MoO ₂ ), or the like is used. By clarifying the interface in this way, the reflection characteristics of the optical element 40 are improved.

  The composite protective layer 30 covers the entire surface of the multilayer film 20 to protect the multilayer film 20 from the surrounding environment (generally, a reduced pressure or vacuum environment that efficiently transmits extreme ultraviolet rays). A lower layer 31 provided on the outermost surface layer 20 and an upper layer 32 provided on the lower layer 31 and serving as the outermost surface of the optical element 40.

Among these, the lower layer 31 includes two or more diffusion prevention layers, and each diffusion prevention layer includes silicon dioxide (SiO ₂ ), zirconium dioxide (ZrO ₂ ), niobium oxide (NbO), niobium dioxide (NbO). ₂ ), niobium pentoxide (Nb ₂ O ₅ ), molybdenum dioxide (MoO ₂ ), chromium oxide (CrO), dichromium trioxide (Cr ₂ O ₃ ), chromium trioxide (CrO ₃ ), carbon tetraboride (B ₄ C), alumina (Al ₂ O ₃ ), carbon, silicon carbide (SiC), silicon nitride (SiN, Si ₂ N ₃ , Si ₃ N ₄ ), boron nitride (BN), and molybdenum silicide (Mo ₃₎ Si, Mo ₅ Si ₃ ), and chromium, or a material containing these. The lower layer 31 is formed of a relatively dense material having a high shielding property as described above, and has a property of preventing components constituting the upper layer 32 from diffusing into the multilayer film 20. Here, the lower layer 31 is configured not only to have a diffusion preventing function but also to include two or more diffusion preventing layers. For the reason described below, a single component prevents a single diffusion. The anti-diffusion ability is higher than when the layer is formed.

  In other words, since the optical element 40 is used under extreme ultraviolet light, there are only a limited number of materials that can be used as a material for the diffusion prevention layer inserted between the multilayer film 20 and the upper layer 32. Further, when importance is attached to the diffusion preventing layer as the diffusion preventing layer, a material having a somewhat large absorption coefficient must be used, and the film thickness of such a material cannot be increased. Furthermore, although the density of the diffusion preventing layer depends on the film forming method, it becomes less than that of the bulk material by a general method such as sputtering. On the other hand, the anti-diffusion ability of the anti-diffusion layer depends not only on the material used and the thickness and density of the layer, but also on the number of laminated anti-diffusion layers. That is, in the optical element 40 of the present embodiment, the upper layer 32 is configured by using the energy barrier formed between the plurality of diffusion prevention layers by configuring the lower layer 31 with two or more diffusion prevention layers. This prevents the components to diffuse into the multilayer film 20 within a certain range. As a result, the composition of the upper layer 32, which is a protective film against the external environment, can be maintained in a stable state for a long period of time, and the phenomenon in which the optical element 40 is eroded from the surface by moisture and oxygen under extreme ultraviolet rays, A phenomenon in which carbon contained therein is converted into a gas such as carbon dioxide and a carbon film is generated on the optical element surface 40 can be reliably suppressed.

  In forming the lower layer 31 having a multilayer structure, a discontinuous interface can be formed in the layer by sequentially laminating a plurality of different materials. In addition, by changing the film forming conditions stepwise for the same material or providing an intermediate process, a discontinuous interface can be formed in the lower layer 31, and a multilayer structure can be obtained.

2A and 2B are enlarged sectional views conceptually illustrating a specific example of the structure of the lower layer 31. FIG. As shown in FIG. 2A, when the lower layer 31 has a two-layer structure, the lower first diffusion prevention layer 31a is formed of, for example, B ₄ C, and the thickness thereof is about 2 nm. The second diffusion preventing layer 31b is made of, for example, SiO ₂ and has a thickness of about 1 nm. The first diffusion prevention layer 31a and the second diffusion prevention layer 31b can be produced by any method such as vapor deposition and sputtering as long as a dense film can be formed without deteriorating the surface roughness. Specific thicknesses of the respective layers 31 a and 31 b are appropriately determined according to reflection characteristics desired for the optical element 40. In order to help form a dense film without deteriorating the surface roughness, another layer that does not have a diffusion preventing function is provided between the lower layer 31, that is, the first diffusion preventing layer 31a and the surface layer of the multilayer film 20. A material may be deposited.

Further, as shown in FIG. 2B, when the lower layer 31 has a three-layer structure, the lower first diffusion prevention layer 131a is formed of, for example, Al ₂ O ₃ to have a thickness of about 1 nm. The central second diffusion prevention layer 131b is formed of, for example, MoSi ₂ to have a thickness of about 2 nm, and the upper third diffusion prevention layer 131c is formed of, for example, BN to have a thickness of about 1 nm. . The manufacturing method of each diffusion prevention layer 131a, 131b, 131c does not ask | require film-forming methods, such as a vapor deposition and a sputtering method, if a precise | minute film | membrane is made without making surface roughness worse. Specific thicknesses of the respective layers 131a, 131b, and 131c are appropriately determined according to reflection characteristics desired for the optical element 40. In order to help form a dense film without deteriorating the surface roughness, the lower layer 31, that is, the first diffusion prevention layer 131 a and the surface layer of the multilayer film 20, has another diffusion prevention function. A material may be deposited.

  In addition to the above-mentioned silicon dioxide and the like, the diffusion preventive material constituting the lower layer 31 includes oxides, borides, silicides, carbides, nitrides, fluorides, and beryllium of nonmetallic elements such as silicon and boron. Compound, Sr, Ba, Sc, Y, La, Ca, Pr, Nd, Sm, Eu, Gd, Tb, Ti, Zr, V, Nb, Mo, Tc, Ru, Rh, Pd, Al, Cr, Be , Ga, Dy, Hf, Re, Fe, Th, Rb and other metal oxides, borides, silicides, carbides, nitrides, fluorides, and beryllium compounds can be used.

Specifically, non-metal oxides such as SiO and B ₂ O ₃ can be used as the diffusion preventing material constituting the lower layer 31. Also, Sc ₂ O ₃ , Tb ₂ O ₃ , PdO, Pd ₂ O ₃ , PdO ₄ , RuO ₂ , RuO ₃ , RuO ₄ , Rh ₂ O ₃ , RhO ₂ , TiO, Ti ₂ O ₃ , TiO ₂ , MoO , Mo ₂ O ₃ , Mo ₂ O ₅ , VO, V ₂ O ₃ , VO ₂ , V ₂ O _{5 and} other metal oxides can be used. _{Further, BaO, BeO, Be 2 O} , CaO, Eu 2 O 3, Gd 2 O 3, La 2 O 3, Mo 4 O 11, Mo 8 O 23, MoO 3, Mo 9 O 24, NdO, Nd 2 O _{3, PrO 1.778, PrO 1.833,} PrO 1.8, PrO 1.818, Sm 2 O 3, SrO, Ti 3 O 2, Ti 2 O, Ti 3 O, Ti 1-x O, Ti n O _2n-1 (n = 2-9), VO _1.76 , VO _1.57 , VO _1.80 , VO _1.84 , VO _1.86 , V ₆ O ₁₃ , V ₈ O, V ₄ O, Metal oxides such as V ₂ O, V ₃ O ₅ , V ₄ O ₇ , V ₅ O ₉ , V ₇ O ₁₃ , V ₆ O ₁₃ , Y ₂ O ₃ , ZrO _2-x can also be used.

As the diffusion preventing material constituting the lower layer 31, non-metal borides such as SiB _x SiB ₆ and SiB ₃ can be used. _{Further, BeB 2, CaB 6, ScB} 2, ScB 12, GdB 6, TiB 2, ZrB 2, TaB 2, Cr 4 B, CrB, Cr 3 B 4, CrB 2, Mo 2 B 5, W 2 B 3, Metal borides such as W ₂ B ₅ , ZrB ₁₂ , GaB ₆ , SrB ₆ , NbB, Nb ₃ B ₄ , and NbB ₂ can be used. _{Furthermore, BeB 12, BeB 9, BeB} 6, BeB 4, Be 2 B, Be 4 B, EuB 6, GdB 2, Gd 2 B 5, GdB 4, GdB 66, Mo 2 B, MoB, Mo 3 B 2, _{MoB 2, MoB 4, Nb 3} B 2, Nd 2 B 5, NdB 4, NdB 6, NdB 66, Pr 2 B 5, PrB 4, PrB 6, RhB 1.1, Rh 7 B 3, RuB, Ru 7 _{B 3, Ru 2 B 3,} RuB 2, Sm 2 B 5, SmB 4, SmB 6, SmB 66, TbB 2, TbB 4, TbB 6, TbB 12, TbB 66, TiB, Ti 3 B 4, V 3 B _{2, VB, V 5 B 6} , V 3 B 4, V 2 B 3, a metal boride VB _2, etc. can be used.

As the diffusion preventing material constituting the lower layer _{31, BaSi 2, LaSi 2,} DySi 2, ZrSi, ZrSi 2, HfSi 2, CrSi 2, MnSi 2, ReSi 2, FeSi 2, PdSi, ThSi 2, CaSi, Ca 2 Si , CaSi ₂ , V ₂ Si, VSi ₂ , RuSi, RhSi ₂ , TbSi _{2 and} other metal silicides can be used. _{Furthermore, BaSi, Nb 5 Si 3,} NbSi 2, Pd 3 Si, Pd 2 Si, Pd 9 Si 4, Ru 2 Si, Ru 2 Si 3, Sr 2 Si, SrSi 2, SrSi, TiSi, Ti 3 Si, Ti ₅ Si ₃ , Ti ₃ Si, Ti ₅ Si ₄ , TiSi ₂ , Ti ₆ Si ₅ , V ₃ Si, V ₅ Si ₃ , V ₆ Si ₅ , Y ₅ Si ₃ , Y ₅ Si ₄ , YSi, Y ₃ Si Metal silicides such as ₅ , Zr ₂ Si, Zr ₄ Si, Zr ₅ Si ₃ , Zr ₃ Si ₂ and Zr ₅ Si ₄ can also be used.

As the diffusion preventing material constituting the lower layer _{31, LaC 2, Be 2 C} , Mo 2 C, MoC, VC, V 4 C 3, V 5 C, TiC, metal carbides such as ZrC can be used. Furthermore, Eu ₄ C ₂ , Eu ₂ C ₃ , EuC ₂ , EuC ₆ , Gd ₂ C, Gd ₄ C ₂ , Gd ₂ C ₃ , GdC ₂ , La ₂ C ₃ , MoC _1-x , Nb ₂ C, NbC , Nd ₂ C ₃ , NdC ₂ , Sc ₂ C, Sc ₄ C ₃ , Sc ₁₃ C ₁₀ , Sc ₁₅ C ₁₉ , Sm ₃ C, Sm ₂ C ₃ , SmC ₂ , Tb ₄ C ₂ , Tb ₂ C, Tb _{2 C 3, TbC 2, Ti} 2 C, V 2 C, V 4 C 3-x, V 6 C 5, V 8 C 7, Y 2 C, Y 4 C 2, Y 15 C 19, Y 2 C 3 , YC _{2 and} other metal carbides can also be used.

As the diffusion preventing material constituting the lower layer 31, a non-metallic nitride such as BN ₂ can be used. _{Furthermore, YN, Ca 3 N 2,} ScN, ZrN, Zr 3 N 2, Sr 3 N 2, TiN, Ti 3 N 4, NbN, NdN, Be 3 N 2, Ba 3 N 2, VN, MoN, Mo 2 Metal nitrides such as N, LaN, and AlN can be used. Furthermore, metal nitrides such as Nb ₂ N, Ti ₂ N, V ₂ N _1-x , VN _1-x , and V ₃₂ N ₂₈ can also be used.

Fluoride such as SrF ₂ , NiF ₂ , YF ₃ or the like can be used as a diffusion preventing material constituting the lower layer 31.

As the diffusion preventing material constituting the lower layer _{31, BaBe 13, CaBe 13,} EuBe 13, GdBe 13, LaBe 13, Mo 3 Be, MoBe 2, MoBe 12, NbBe 12, Nb 2 Be 17, NbBe 3, NbBe 2, _{nb 3 Be 2, NdBe 13,} PdBe 12, PdBe 5, Pd 2 Be, Pd 3 Be, PdBe, Pd 3 Be 2, Pd 4 Be 3, PrBe 13, Ru 3 Be 17, Ru 3 Be 10, RuBe 2, _{ru 2 Be 3, ScBe 5,} Sc 2 Be 17, ScBe 13, SmBe 13, SrBe 13, TbBe 13, TiBe 2, TiBe 3, Ti 2 Be 17, TiBe 12, VBe 12, VBe 2, YBe 13, ZrBe 13 , Zr ₂ Be ₁₇ , ZrBe ₅ , Beryllium compounds such as ZrBe ₂ can be used.

  Returning to FIG. 1, the upper layer 32 has (1) an oxidation-resistant metal, (2) a reaction stabilizing substance such as niobium, (3) a catalytic metal, depending on the application and use conditions of the optical element 40. (4) Oxidation resistant non-metal (oxidation resistant compound) and (5) Catalytic material (catalytic compound).

(1) In the case of an oxidation resistant metal In the first case, the upper layer 32 is formed of an oxidation resistant metal or a metal material containing the same. More specifically, the upper layer 32 contains at least one selected from the group consisting of ruthenium, rhodium, platinum, gold, silver and the like as a main component. Thereby, the upper layer 32 serves as an antioxidant film. That is, by forming the upper layer 32 containing these oxidation resistant metals on the outermost surface of the optical element 40, the optical element 40 (especially a multilayer film) is formed by moisture or oxygen supplied to the surface of the optical element 40 or in the vicinity thereof. 20) can be prevented from being eroded, and the reflectance of the optical element 40 can be prevented from gradually decreasing with such erosion. As already described, the lower layer 31 inserted between the upper layer 32 and the multilayer film 20 has a function of preventing component metals and the like constituting the upper layer 32 from diffusing to the multilayer film 20 side. Thereby, deterioration of the oxidation resistance of the upper layer 32 which is the outermost surface of the optical element 40 can be prevented, and the reflection characteristic of the optical element 40 can be maintained for a long time.
In the above case, the upper layer 32 is formed of an oxidation-resistant metal such as ruthenium, rhodium, platinum, gold, or silver. However, the oxidation-resistant metal is not limited thereto. In addition to this, for example, even if the upper layer 32 is formed of a metal material containing niobium, palladium, osmium, iridium or the like as a main component, the same effect with respect to oxidation resistance is expected.

(2) Case of Reaction Stabilizing Substance In the second case, the upper layer 32 is formed of niobium or a metal material containing this as a main component. When the upper layer 32 containing niobium is formed on the outermost surface of the optical element 40, niobium oxide tends to be formed on the surface and stabilized. That is, it is considered that the surface of the upper layer 32 is covered with niobium oxide and functions as a dense and stable barrier, so that moisture and oxygen can be prevented from entering the composite protective layer 30, and The oxidation resistance under ultraviolet irradiation can be improved. Note that the lower layer 31 inserted between the upper layer 32 and the multilayer film 20 has a function of preventing niobium or the like constituting the upper layer 32 from diffusing to the multilayer film 20 side. Thereby, deterioration of the oxidation resistance of the upper layer 32 can be prevented, and the reflection characteristics of the optical element 40 can be maintained over a long period of time.

(3) Case of Catalytic Metal In the third case, the upper layer 32 is formed of a catalytic metal or a metal material containing the metal. More specifically, the upper layer 32 contains at least one selected from the group consisting of nickel, palladium, platinum, silver, ruthenium, and rhodium as a main component. Thereby, the upper layer 32 serves as a carbon suppression film. That is, by forming the upper layer 32 containing these catalytic metals on the outermost surface of the optical element 40, the carbon in the organic matter supplied to the surface of the optical element 40 or in the vicinity thereof is converted to carbon dioxide. Can do. Therefore, it is possible to suppress the occurrence of a photo CVD phenomenon in which the carbon film is gradually deposited on the surface of the optical element 40, and it is possible to prevent the reflectance of the optical element 40 from gradually decreasing as the carbon film is deposited. As already described, the lower layer 31 inserted between the upper layer 32 and the multilayer film 20 has a function of preventing the component metals constituting the upper layer 32 from diffusing to the multilayer film 20 side. Thereby, deterioration of the catalytic activity of the upper layer 32 which is the outermost surface of the optical element 40 can be prevented, and the reflection characteristic of the optical element 40 can be maintained over a long period of time.
Of the above catalytic metals, platinum, ruthenium, rhodium, and palladium can also be regarded as oxidation resistant metals, and prevent moisture and oxygen from entering the composite protective layer 30, The oxidation resistance of the layer 32 is enhanced.

(4) Oxidation-resistant material In the fourth case, the upper layer 32 is formed of an oxidation-resistant material or a material including the same. More specifically, the upper layer 32 includes silicon dioxide (SiO ₂ ), zirconium dioxide (ZrO ₂ ), niobium oxide (NbO), niobium dioxide (NbO ₂ ), niobium pentoxide (Nb ₂ O ₅ ), Molybdenum dioxide, alumina (Al ₂ O ₃ ), chromium oxide (CrO), dichromium trioxide (Cr ₂ O3), chromium trioxide (CrO ₃ ), ruthenium dioxide (RuO ₂ ), ruthenium trioxide (RuO ₃ ), It contains at least one selected from the group consisting of ruthenium tetroxide (RuO ₄ ), dirhodium trioxide (Rh ₂ O ₃ ), rhodium dioxide (RhO ₂ ), and carbon as a main component. Thereby, the upper layer 32 serves as an antioxidant film. The lower layer 31 inserted between the upper layer 32 and the multilayer film 20 has a function of preventing component metals, oxygen, and the like constituting the upper layer 32 from diffusing into the multilayer film 20. Due to the presence of the lower layer 31, it is possible to prevent deterioration of the oxidation resistance of the upper layer 32, which is the outermost surface of the optical element 40, and to maintain the reflection characteristics of the optical element 40 over a long period of time.

  In addition to the above-mentioned silicon dioxide or the like, simple boron can be used as the oxidation resistant material constituting the upper layer 32.

  In addition, oxides, borides, silicides, carbides, nitrides, fluorides, and beryllium compounds of nonmetallic elements such as silicon and boron, Be, Ca, Sc, Gd, Ti, Zr, Ta, Cr, and Mo , W, Zr, Ga, Sr, Nb, Ba, La, Dy, Hf, Mn, Re, Fe, Pd, Th, V, Ru, Rh, Tb, Y, Nd, Al, Ni, Eu, Pr, Sm , Rb and other metal oxides, borides, silicides, carbides, nitrides, fluorides, and beryllium compounds can be used.

Specifically, a non-metal oxide such as SiO, B ₂ O ₃ can be used as an oxidation resistant material constituting the upper layer 32. _{Also, Sc 2 O 3, Tb 2} O 3, PdO, Pd 2 O 3, PdO 4, TiO, Ti 2 O 3, TiO 2, MoO, Mo 2 O 3, Mo 2 O 5, VO, V 2 O 3 , VO ₂ , V ₂ O _{5 and} other metal oxides can be used. _{Further, BaO, BeO, Be 2 O} , CaO, Eu 2 O 3, Gd 2 O 3, La 2 O 3, Mo 4 O 11, Mo 8 O 23, MoO 3, Mo 9 O 24, NdO, Nd 2 O _{3, PrO 1.778, PrO 1.833,} PrO 1.8, PrO 1.818, Sm 2 O 3, SrO, Ti 3 O 2, Ti 2 O, Ti 3 O, Ti 1-x O, Ti n O _2n-1 (n = 2-9), VO _1.76 , VO _1.57 , VO _1.80 , VO _1.84 , VO _1.86 , V ₆ O ₁₃ , V ₈ O, V ₄ O, Metal oxides such as V ₂ O, V ₃ O ₅ , V ₄ O ₇ , V ₅ O ₉ , V ₇ O ₁₃ , V ₆ O ₁₃ , Y ₂ O ₃ , ZrO _2-x can also be used.

As the oxidation resistant material constituting the upper layer 32, non-metal borides such as SiB ₃ , SiB ₆ , and SiB _x can be used. _{Further, BeB 2, CaB 6, ScB} 2, ScB 12, GdB 6, TiB 2, ZrB 2, TaB 2, Cr 4 B, CrB, Cr 3 B 4, CrB 2, Mo 2 B 5, W 2 B 3, Metal borides such as W ₂ B ₅ , ZrB ₁₂ , GaB ₆ , SrB ₆ , NbB, Nb ₃ B ₄ , and NbB ₂ can be used. _{Further, BeB 12, BeB 9, BeB} 6, BeB 4, Be 2 B, Be 4 B, EuB 6, GdB 2, Gd 2 B 5, GdB 4, GdB 66, Mo 2 B, MoB, Mo 3 B 2, _{MoB 2, MoB 4, Nb 3} B 2, Nd 2 B 5, NdB 4, NdB 6, NdB 66, Pr 2 B 5, PrB 4, PrB 6, RhB 1.1, Rh 7 B 3, RuB, Ru 7 _{B 3, Ru 2 B 3,} RuB 2, Sm 2 B 5, SmB 4, SmB 6, SmB 66, TbB 2, TbB 4, TbB 6, TbB 12, TbB 66, TiB, Ti 3 B 4, V 3 B _{2, VB, V 5 B 6} , V 3 B 4, V 2 B 3, a metal boride VB _2, etc. can be used.

As the oxidation resistance material constituting the upper layer _{32, BaSi 2, LaSi 2,} DySi 2, ZrSi, ZrSi 2, HfSi 2, CrSi 2, MoSi 2, MnSi 2, ReSi 2, FeSi 2, PdSi, ThSi 2, CaSi , Ca ₂ Si, CaSi ₂ , V ₂ Si, VSi ₂ , RuSi, RhSi ₂ , TbSi _{2 and} other metal silicides can be used. In addition, BaSi, Mo ₃ Si, Mo ₅ Si ₃ , Nb ₅ Si ₃ , NbSi ₂ , Pd ₃ Si, Pd ₂ Si, Pd ₉ Si ₄ , Ru ₂ Si, Ru ₂ Si ₃ , Sr ₂ Si, SrSi ₂ , _{SrSi, TiSi, Ti 3 Si,} Ti 5 Si 3, Ti 3 Si, Ti 5 Si 4, TiSi 2, Ti 6 Si 5, V 3 Si, V 5 Si 3, V 6 Si 5, Y 5 Si 3, Y _{5 Si 4, YSi, Y 3} Si 5, Zr 2 Si, Zr 4 Si, Zr 5 Si 3, Zr 3 Si 2, Zr metal silicide such as 5 Si ₄ can also be used.

As the oxidation-resistant material constituting the upper layer 32, non-metal carbides such as SiC and B ₄ C can be used. Also, metal carbides such as LaC ₂ , Be ₂ C, Mo ₂ C, MoC, VC, V ₄ C ₃ , V ₅ C, TiC, and ZrC can be used. Furthermore, Eu ₄ C ₂ , Eu ₂ C ₃ , EuC ₂ , EuC ₆ , Gd ₂ C, Gd ₄ C ₂ , Gd ₂ C ₃ , GdC ₂ , La ₂ C ₃ , MoC _1-x , Nb ₂ C, NbC , Nd ₂ C ₃ , NdC ₂ , Sc ₂ C, Sc ₄ C ₃ , Sc ₁₃ C ₁₀ , Sc ₁₅ C ₁₉ , Sm ₃ C, Sm ₂ C ₃ , SmC ₂ , Tb ₄ C ₂ , Tb ₂ C, Tb _{2 C 3, TbC 2, Ti} 2 C, V 2 C, V 4 C 3-x, V 6 C 5, V 8 C 7, Y 2 C, Y 4 C 2, Y 15 C 19, Y 2 C 3 , YC _{2 and} other metal carbides can also be used.

As the oxidation resistant material constituting the upper layer 32, non-metal nitrides such as SiN, Si ₂ N ₃ , Si ₃ N ₄ , BN, and BN ₂ can be used. _{Moreover, YN, Ca 3 N 2,} ScN, ZrN, Zr 3 N 2, Sr 3 N 2, TiN, Ti 3 N 4, NbN, NdN, Be 3 N 2, Ba 3 N 2, VN, MoN, Mo 2 Metal nitrides such as N, LaN, and AlN can be used. Further, non-metal nitrides such as Nb ₂ N, Ti ₂ N, V ₂ N _1-x , VN _1-x , V ₃₂ N ₂₈ can be used.

A metal fluoride such as SrF ₂ , NiF ₂ , YF ₃ can be used as the oxidation resistant material constituting the upper layer 32.

As the oxidation resistance material constituting the upper layer _{32, BaBe 13, CaBe 13,} EuBe 13, GdBe 13, LaBe 13, Mo 3 Be, MoBe 2, MoBe 12, NbBe 12, Nb 2 Be 17, NbBe 3, NbBe 2 _{, Nb 3 Be 2, NdBe 13} , PdBe 12, PdBe 5, Pd 2 Be, Pd 3 Be, PdBe, Pd 3 Be 2, Pd 4 Be 3, PrBe 13, Ru 3 Be 17, Ru 3 Be 10, RuBe 2 _{, Ru 2 Be 3, ScBe 5} , Sc 2 Be 17, ScBe 13, SmBe 13, SrBe 13, TbBe 13, TiBe 2, TiBe 3, Ti 2 Be 17, TiBe 12, VBe 12, VBe 2, YBe 13, ZrBe ₁₃ , Zr ₂ Be ₁₇ , ZrBe ₅ , metal beryllium compounds such as ZrBe ₂ can be used.

(5) Case of Catalytic Material In the fifth case, the upper layer 32 is formed of a catalytic material or a metal material including the same. More specifically, the upper layer 32 is formed of titanium oxide or a metal material containing this as a main component. Thereby, the upper layer 32 serves as a carbon suppression film. The lower layer 31 inserted between the upper layer 32 and the multilayer film 20 has a function of preventing component metals, oxygen, and the like constituting the upper layer 32 from diffusing into the multilayer film 20. Thereby, deterioration of the catalytic activity of the upper layer 32 which is the outermost surface of the optical element 40 can be prevented, and the reflection characteristic of the optical element 40 can be maintained over a long period of time.

  The various types of the upper layer 32 described above can be produced by various film forming methods such as vapor deposition and sputtering if a dense film can be formed without deteriorating the surface roughness. Further, in the formation of the upper layer 32, a large film thickness is desired in order to make maximum use of oxidation resistance and catalytic activity. However, extreme ultraviolet rays are often absorbed by the upper layer 32, and the thickness of the upper layer 32 is, for example, 4 nm or less. The specific thickness is appropriately determined according to the reflection characteristics desired for the optical element 40.

[Second Embodiment]
FIG. 3 is a view for explaining the structure of the projection exposure apparatus according to the second embodiment, in which the optical element 40 of the first embodiment is incorporated as an optical component.

  As shown in FIG. 3, the projection exposure apparatus 100 includes, as an optical system, a light source device 50 that generates extreme ultraviolet rays (wavelength 11 to 14 nm), and an illumination optical system 60 that illuminates the mask MA with extreme ultraviolet illumination light. And a projection optical system 70 for transferring the pattern image of the mask MA to the wafer WA, which is a sensitive substrate, and as a mechanical mechanism, a mask stage 81 for supporting the mask MA and a wafer stage 82 for supporting the wafer WA are provided.

  The light source device 50 includes a laser light source 51 that generates laser light for plasma excitation, and a tube 52 that supplies a gas such as xenon that is a target material into the housing SC. Further, the light source device 50 is provided with a capacitor 54 and a collimator mirror 55. By condensing the laser light from the laser light source 51 with respect to xenon emitted from the tip of the tube 52, the target material in that portion is turned into plasma to generate extreme ultraviolet rays. The condenser 54 collects extreme ultraviolet light generated at the tip S of the tube 52. The extreme ultraviolet rays that have passed through the condenser 54 are emitted outside the casing SC while being converged, and enter the collimator mirror 55. In place of the light source light from the laser plasma type light source device 50 as described above, radiation light from a discharge plasma light source, a SOR light source, or the like can be used.

  The illumination optical system 60 includes reflection type optical integrators 61 and 62, a condenser mirror 63, a deflection mirror 64, and the like. Light source light from the light source device 50 is condensed by the condenser mirror 63 while being made uniform as illumination light by the optical integrators 61 and 62, and is incident on a predetermined region (for example, a belt-like region) on the mask MA through the deflection mirror 64. As a result, a predetermined area on the mask MA can be uniformly illuminated by extreme ultraviolet rays having an appropriate wavelength.

  Note that there is no substance having sufficient transmittance in the wavelength range of extreme ultraviolet rays, and a reflective mask is used as the mask MA instead of a transmissive mask.

  The projection optical system 70 is a reduction projection system including a large number of mirrors 71, 72, 73 and 74. A circuit pattern, which is a pattern image formed on the mask MA, forms an image on the wafer WA coated with a resist by the projection optical system 70 and is transferred to the resist. In this case, the area where the circuit pattern is projected at once is a linear or arc-shaped slit area, and a rectangular pattern formed on the mask MA, for example, by scanning exposure that moves the mask MA and the wafer WA synchronously. This circuit pattern can be transferred to a rectangular area on the wafer WA without waste.

Of the light source device 50 described above, the portion disposed on the optical path of extreme ultraviolet rays, the illumination optical system 60, and the projection optical system 70 are disposed in the vacuum vessel 84, and attenuation of exposure light is prevented. Yes. That is, the extreme ultraviolet rays are absorbed and attenuated by the atmosphere, but the entire apparatus is blocked from the outside by the vacuum vessel 84 and the optical path of the extreme ultraviolet rays is set to a predetermined degree of vacuum (for example, 1.3 × 10 ⁻³ Pa or less). By maintaining it, the attenuation of extreme ultraviolet rays, that is, the decrease in brightness and contrast of the transferred image is prevented.

  In the above projection exposure apparatus, the optical elements 54, 55, 61, 62, 63, 64, 71, 72, 73, 74 and the mask MA, which are arranged on the optical path of extreme ultraviolet rays, and the mask MA are exemplified in FIG. Element 40 is used. At this time, the shape of the optical surface of the optical element 40 is not limited to the concave surface, and is appropriately adjusted depending on the place of incorporation such as a flat surface, a convex surface, or a multi-surface.

  The operation of the projection exposure apparatus shown in FIG. 3 will be described below. In this projection exposure apparatus, the mask MA is illuminated by illumination light from the illumination optical system 60, and a pattern image of the mask MA is projected onto the wafer WA by the projection optical system 70. As a result, the pattern image of the mask MA is transferred to the wafer WA.

  In the projection exposure apparatus described above, the optical elements 54, 55, 61, 62, 63, 64, 71, 72, 73, 74, MA, which are controlled with high reflectivity and high accuracy, are used. Exposure is possible. Further, in this projection exposure apparatus, the oxidation reaction is suppressed on the surfaces of the optical elements 54, 55, 61, 62, 63, 64, 71, 72, 73, 74, MA, that is, the optical surface, and the formation of the carbon film is suppressed. As a result, it is possible to prevent the reflection characteristics of these optical elements from deteriorating, thereby extending the life of the projection exposure apparatus.

  Although the present invention has been described based on the above embodiments, the present invention is not limited to the above embodiments. For example, in the above-described embodiment, a projection exposure apparatus using extreme ultraviolet rays as exposure light has been described. However, an optical element 40 as shown in FIG. 1 or the like is incorporated in a projection exposure apparatus that uses ultraviolet rays other than extreme ultraviolet rays as exposure light. And the deterioration of the reflection characteristics of the optical element can be suppressed.

  In addition to the projection exposure apparatus, for example, an optical element 40 as shown in FIG. 1 and the like is also incorporated in various optical instruments including a soft X-ray optical instrument such as a soft X-ray microscope and a soft X-ray analyzer. be able to.

It is sectional drawing explaining the optical element which concerns on 1st Embodiment. (A), (b) is an expanded sectional view explaining the specific example of the structure of a lower layer. It is a figure explaining the projection exposure apparatus which concerns on 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Board | substrate, 20 ... Multilayer film, 30 ... Composite protective layer, 31 ... Lower layer, 32 ... Upper layer, 40 ... Optical element, 50 ... Light source device, 60 ... Illumination optical system, 70 ... Projection optical system, 81 ... Mask Stage 82: Wafer stage L1, L2 Thin film layer WA Wafer

Claims (4)

A supporting substrate;
A multilayer film supported on the substrate and reflecting extreme ultraviolet rays;
A composite protective layer provided on the outermost layer of the multilayer film and including a lower layer including two or more diffusion prevention layers, and an upper layer provided on the lower layer;
An optical element comprising:   The optical element according to claim 1, wherein the upper layer contains at least one of an oxidation-resistant substance and a catalytic action substance.   The diffusion preventing layer is made of silicon dioxide, zirconium dioxide, niobium oxide, niobium dioxide, niobium pentoxide, molybdenum dioxide, chromium oxide, dichromium trioxide, chromium trioxide, carbon tetraboride, alumina, carbon, silicon carbide, 3. The optical element according to claim 1, comprising at least one selected from the group consisting of silicon nitride, boron nitride, molybdenum silicide, and chromium as a main component. A light source that generates extreme ultraviolet light;
An illumination optical system that guides extreme ultraviolet light from the light source to a transfer mask;
A projection optical system that forms a pattern image of the mask on a sensitive substrate;
A projection exposure apparatus, wherein at least one of the mask, the illumination optical system, and the projection optical system includes the optical element according to any one of claims 1 to 3.

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