JP2007198782A - Multilayer-film reflecting mirror and exposure system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer-film reflecting mirror which suppresses a degradation in reflectance by preventing the diffusion occurring on a substance of high reflectance and that occurring on a substance of low reflectance. <P>SOLUTION: In the multilayer-film reflecting mirror 2 including a multilayer film 12 constituted by depositing at least two kinds of layers 6 and 8, composed mainly of prescribed substances, alternately and periodically on the surface of a substrate to form the film 12, diffusion prevention layers 10a and 10b which are different in material and/or thickness are formed on the basis of a prescribed substance forming a lower layer in every interface of the multilayer film 12. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a multilayer film reflecting mirror having a multilayer film formed on a substrate surface and an exposure apparatus including the multilayer film reflecting mirror.

  In recent years, with the progress of miniaturization of semiconductor integrated circuits, in order to improve the resolving power of an optical system limited by the diffraction limit of light, instead of the conventional ultraviolet rays, a wavelength shorter than this (for example, about 11 to 14 nm) A projection exposure apparatus using extreme ultraviolet rays has been developed (see Patent Document 1).

Japanese Patent Laid-Open No. 2003-14893

  In the above-described projection exposure apparatus (EUV exposure apparatus) using extreme ultraviolet rays, since there is no substance that transmits extreme ultraviolet rays, the optical system needs to be constituted by a reflecting mirror. Since the rate is very close to 1, unlike a conventional optical element using refraction or reflection, a multilayer mirror that intensifies light by interference is used. This multilayer mirror has a multilayer film in which a substance having a high refractive index (for example, Si) and a substance having a low refractive index (for example, Mo) are alternately stacked on a substrate in the wavelength region to be used.

  However, when a material with a high refractive index and a material with a low refractive index are stacked alternately, diffusion occurs between the two materials, leading to a decrease in optical properties such as a decrease in reflectivity and a decrease in half-value width. Therefore, it is necessary to prevent diffusion that occurs between a material having a high refractive index and a material having a low refractive index. Here, the diffusion state occurs when a material having a low refractive index is stacked on a material having a high refractive index and a diffusion occurring when a material having a high refractive index is stacked on a material having a low refractive index. Are known to be different.

  An object of the present invention is to provide a multilayer film reflecting mirror that prevents diffusion occurring on a material having a high refractive index and diffusion occurring on a material having a low refractive index, and prevents a decrease in reflectance, and the multilayer film reflecting mirror. An exposure apparatus is provided.

  The multilayer film reflector of the present invention comprises a multilayer film (12) constituted by alternately and periodically forming at least two kinds of layers (6, 8) mainly composed of a predetermined substance on a substrate surface. In the multilayer-film reflective mirror (2) provided, the diffusion prevention layer (10a, 10a, at least one of the material and the thickness is different based on a predetermined substance that forms a lower-layer film for each interface of the multilayer film (12). 10b) is formed.

  The exposure apparatus of the present invention is characterized in that the multilayer mirror (2) of the present invention is provided in at least a part of the optical system.

  According to the multilayer film reflecting mirror of the present invention, the diffusion prevention layer having at least one of the material and the thickness different from each other is formed on the basis of the predetermined substance that forms the lower layer film for each interface of the multilayer film. Diffusion between substances at the interface of the multilayer film can be prevented. Therefore, it is possible to prevent a decrease in reflectance due to diffusion between substances at the interface.

  Further, according to the exposure apparatus of the present invention, a diffusion prevention layer having at least one of a material and a thickness different from each other based on a predetermined substance that forms a lower layer film for each interface of the multilayer film on at least a part of the optical system. Is provided, the diffusion of substances at the interface of the multilayer film can be prevented and good exposure can be performed.

  A multilayer film reflecting mirror according to a first embodiment of the present invention will be described with reference to the drawings. The multilayer reflector is used in, for example, an EUV exposure apparatus that uses extreme ultraviolet light (EUV light) as exposure light. FIG. 1 is a cross-sectional view of the multilayer-film reflective mirror 2 according to the first embodiment. As shown in FIG. 1, the multilayer-film reflective mirror 2 includes a multilayer film 12 on the surface of a low thermal expansion glass substrate 4 that has been polished into a highly accurate shape. Here, in the multilayer film 12, a layer containing the substance 1 as a main component (hereinafter referred to as “substance 1 layer”) 6 and a layer containing the substance 2 as a main component (hereinafter referred to as “substance 2 layer”) 8 alternately and periodically. A diffusion prevention layer 10 a is formed between the substance 1 layer 6 and the substance 2 layer 8, and a diffusion prevention layer 10 b is formed between the substance 2 layer 8 and the substance 1 layer 6. .

  In the multilayer film in which the substance 1 layer 6 and the substance 2 layer 8 are alternately and periodically laminated, the substance 2 / substance 1 interface where the substance 2 layer 8 is laminated on the substance 1 layer 6, and the substance 2 layer 8 There is a substance 1 / substance 2 interface on which a substance 1 layer 6 is laminated. At the substance 2 / substance 1 interface and the substance 1 / substance 2 interface, high energy is applied when the substance 2 layer 8 (substance 1 layer 6) is laminated on the substance 1 layer 6 (substance 2 layer 8). Diffusion occurs when the material 2 particles (substance 1 particles) that come in enter the substance 1 layer 6 (substance 2 layer 8), but at the substance 2 / substance 1 interface and the substance 1 / substance 2 interface Diffuse state is different. Therefore, in the embodiment of the present invention, the diffusion prevention layer 10a is laminated on the substance 2 / substance 1 interface, and the diffusion prevention layer 10b different from the diffusion prevention layer 10a is laminated on the substance 1 / substance 2 interface. . That is, by stacking optimized diffusion prevention layers 10a and 10b at the substance 2 / substance 1 interface and the substance 1 / substance 2 interface, respectively, the substance 2 diffuses into the substance 1 layer 6 and the substance 1 becomes a substance. Each of the two layers 8 can be prevented from diffusing.

  In the case where a multilayer film is formed by periodically laminating a layer mainly composed of the substance 1, a layer mainly composed of the substance 2, and a layer mainly composed of the substance 3, the substance 2 / the substance 1 By stacking optimized diffusion prevention layers at each of the interface, substance 3 / substance 2 interface, and substance 1 / substance 3 interface, substance 2 becomes substance 1 layer, substance 3 becomes substance 2 layer, substance It is possible to prevent 1 from diffusing into each of the three substance layers.

  The material and thickness of the diffusion preventing layer are determined based on a predetermined substance and film forming conditions for forming a lower layer film for each interface of the multilayer film. Further, not only the substance that forms the lower layer film, but also the substance that forms the lower layer film and the substance that forms the film formed on the lower layer, that is, the substance that forms the lower layer film at the interface and the upper layer film. The material and thickness of the diffusion preventing layer are also determined by the combination of substances to be formed.

The material for the diffusion preventing layer, for _{example, B 4 C, C, MoSi} 2, MoC, MoO 2 and the like are used. In addition, oxides, borides, silicides, carbides, nitrides, fluorides, and beryllium compounds of non-metallic elements such as silicon and boron, Sr, Ba, Sc, Y, La, Ca, Pr, Nd, Various metals such as Sm, Eu, Gd, Tb, Ti, Zr, V, Nb, Mo, Tc, Ru, Rh, Pd, Al, Cr, Be, Ga, Dy, Hf, Re, Fe, Th, Rb, The oxides, borides, silicides, carbides, nitrides, fluorides, and beryllium compounds can be used.

Specifically, non-metal oxides such as SiO ₂ , SiO, B ₂ O ₃ can be used as the material of the diffusion preventing layer. _{Further, NbO, NbO 2, Nb 2} O 5, CrO, Cr 2 O 3, CrO 3, Al 2 O 3, ZrO 2, 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, MoO 2, Mo 2 O 5, VO, V 2 O 3, VO Metal oxides such as ₂ , V ₂ O ₅ 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.

Further, as the material of the diffusion preventing layer, non-metal borides such as SiB _x , SiB ₆ , SiB ₃ can also 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.

Further, as the material of the diffusion preventing _{layer, 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 Metal silicides such as ₂ , V ₂ Si, VSi ₂ , RuSi, RhSi ₂ and TbSi ₂ can also be used. Furthermore, 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.

Further, non-metal carbides such as SiC and B ₄ C can be used as the material of the diffusion preventing layer. 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.

In addition, non-metal nitrides such as SiN, Si ₂ N ₃ , Si ₃ N ₄ , BN, and BN ₂ can be used as the material of the diffusion prevention layer. _{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. 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.

Moreover, fluorides such as SrF ₂ , NiF ₂ , YF ₃ can be used as the material of the diffusion preventing layer. Further, as the material of the diffusion preventing _{layer, 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, Zr beryllium compounds such as e ₂ can be used.

  Moreover, as a material of the diffusion preventing layer, any material may be used as long as it includes at least one selected from the group consisting of the above-mentioned substances, but a plurality of substances selected from the group consisting of the above-mentioned substances may be used. . In other words, in order to increase the reflectivity of the multilayer mirror, a substance that forms a lower layer film at each interface of the multilayer film, or a substance that forms a lower layer film at each interface of the multilayer film and an upper layer film are formed. The material, structure and thickness of the diffusion prevention layer are optimized based on the combination of substances to be used. In addition, since absorption of a material will become large when it becomes extreme ultraviolet rays, it is preferable that the thickness of a diffusion prevention layer shall be 3 nm or less.

  Here, when forming the multilayer film by laminating the substance 1 layer and the substance 2 layer, the substance 2 becomes the substance 1 layer by optimizing the film formation conditions without forming a diffusion prevention layer for each interface. In addition, the substance 1 may be prevented from diffusing into the substance 2 layer. That is, the diffusion occurs when, for example, the material 1 particles flying with high energy enter the material 2 layer when the material 1 is laminated on the material 2 layer by sputtering or vapor deposition. Therefore, in each of the case where the substance 2 layer is laminated on the substance 1 layer and the case where the substance 1 layer is laminated on the substance 2 layer, diffusion is reduced by optimizing the film formation conditions so as to reduce the energy of the flying particles. It may be prevented. As a method for reducing the energy of the flying particles, for example, an inert gas is introduced into the film forming chamber and the velocity of the flying particles is decreased by colliding with the flying particles.

  Note that when the energy of the flying particles is reduced, there is a possibility that the density of the film becomes low or uniform film formation is hindered by island-like growth. Therefore, for example, in the case of forming the substance 2 layer on the substance 1 layer, the introduction of the inert gas is stopped after the substance 2 layer is formed to a thickness of about 1 nm with the energy of the flying particles reduced. Film formation is performed without reducing the energy of flying particles.

Next, an EUV exposure apparatus according to a second embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a diagram showing a schematic configuration of an EUV exposure apparatus (reduction projection exposure apparatus) according to the second embodiment. In the EUV exposure apparatus shown in FIG. 2, the entire optical path is kept in a vacuum (for example, 1 × 10 ⁻³ Pa or less). The EUV exposure apparatus includes an illumination optical system IL including a light source. EUV light emitted from the illumination optical system IL (generally indicates a wavelength of 5 to 20 nm, specifically, wavelengths of 13.5 nm and 11 nm are used) is reflected by the folding mirror 301 to form a pattern. The reticle 302 is irradiated.

  The reticle 302 is a reflection type reticle, and is held by a chuck 303 a fixed to the reticle stage 303. The reticle stage 303 is configured to be able to move 100 nm or more in the scanning direction, and is configured to be capable of minute movement in the direction perpendicular to the scanning direction and in the optical axis direction. The scanning direction of the reticle stage 303 and the position in the direction orthogonal to the scanning direction are controlled with high accuracy by a laser interferometer (not shown), and the position in the optical axis direction is a reticle focus composed of a reticle focus light transmission system 304 and a reticle focus light reception system 305. It is controlled by a sensor.

  The reticle 302 is formed with a multilayer film (for example, molybdenum (Mo) / silicon (Si) or molybdenum (Mo) / beryllium (Be)) that reflects EUV light, and an absorption layer ( For example, it is patterned by nickel (Ni) or aluminum (Al). The EUV light reflected by the reticle 302 enters the optical barrel 314.

  In the optical barrel 314, a plurality (four in this embodiment) of mirrors 306, 307, 308, and 309 are installed. At least one of these mirrors 306 to 309 is configured by the multilayer-film reflective mirror according to the first embodiment. In this embodiment, although four mirrors are provided as the projection optical system, six or eight mirrors may be provided. In this case, the numerical aperture (NA) can be increased.

  The EUV light that has entered the optical barrel 314 is reflected by the mirror 306, is then sequentially reflected by the mirror 307, the mirror 308, and the mirror 309, exits from the optical barrel 314, and enters the wafer 310. Note that the reduction magnification of the projection optical system including the mirrors 306 to 309 is, for example, 1/4 or 1/5. In addition, an off-axis microscope 315 that performs alignment of the wafer 310 is installed in the vicinity of the optical barrel 314.

  The wafer 310 is held on a chuck 311 a fixed to the wafer stage 311. The wafer stage 311 is installed in a plane orthogonal to the optical axis, and is configured to be movable, for example, 300 to 400 nm in a plane orthogonal to the optical axis. In addition, the wafer stage 311 is configured to be capable of minute movement in the optical axis direction. The position of the wafer stage 311 in the optical axis direction is controlled by a wafer autofocus sensor including a wafer autofocus light transmission system 312 and a wafer autofocus light reception system 313. The position of the wafer stage 311 in the plane orthogonal to the optical axis is controlled with high accuracy by a laser interferometer (not shown).

  At the time of exposure, the reticle stage 303 and the wafer stage 311 have the same speed ratio as the reduction magnification of the projection optical system, for example, (moving speed of the reticle stage 303) :( moving speed of the wafer stage 311) = 4: 1 or 5: 1 for synchronous scanning.

  According to the EUV exposure apparatus according to the second embodiment, at least one of the mirrors constituting the projection optical system is configured by the multilayer film reflecting mirror according to the first embodiment. Good exposure can be performed by an optical system having a highly accurate surface shape that does not cause a decrease in reflectance due to diffusion between substances in the above.

  In the second embodiment, at least one of the mirrors 306 to 309 is configured by the multilayer film reflecting mirror according to the first embodiment, but the mirror and the folding mirror 301 included in the illumination optical system IL. The reticle 302 and the like may be configured by the multilayer film reflecting mirror according to the first embodiment.

In Example 1, molybdenum (Mo) is used as the material 1, silicon (Si) is used as the material 2, SiO ₂ is 1 nm and the Mo layer is formed on the Si layer at the Si / Mo interface where the Si layer is stacked on the Mo layer. 1 nm of B ₄ C was laminated as a diffusion preventing layer on the Mo / Si interface to be laminated. Since SiO ₂ has good affinity with Si and has a strong covalent bond, Mo particles are difficult to diffuse into the Si layer even when heavy Mo comes in, so the Mo particles diffuse into the Si layer at the Mo / Si interface. Can be prevented. Further, _{B 4} C is very light molecular weight, preventing because does not enter the Mo layer, the Si / Mo interface, the flying the Si particles _{B 4} C is received, that the Si particles are diffused into the Mo layer can do.

In Example 2, molybdenum (Mo) is used as the substance 1, silicon (Si) is used as the substance 2, and Ar ² gas is used as an inert gas when forming a layer mainly containing different substances. Introduced up to Pa to reduce the speed of flying particles. The introduction of Ar gas was stopped when the Si layer (Mo layer) was formed to 1 nm on the Mo layer (Si layer), and the density of the film formed thereafter was improved. By reducing the speed of the flying particles, the flying particles can be prevented from entering the lower layer, and diffusion can be prevented from occurring at the Mo / Si interface and the Si / Mo interface. In addition, since the film is formed without reducing the speed of the flying particles in the portion after the interface, a uniform film is finally formed.

It is sectional drawing of the multilayer-film reflective mirror concerning 1st Embodiment. It is a figure which shows schematic structure of the EUV exposure apparatus concerning 2nd Embodiment.

Explanation of symbols

2 ... Multilayer reflection mirror, 4 ... Glass substrate, 6 ... Substance 1 layer, 8 ... Substance 2 layer, 10a, 10b ... Diffusion prevention layer, 12 ... Multilayer film, IL , Illumination optical system, 302, reticle, 303, reticle stage, 306 to 309, mirror, 310, wafer, 311, wafer stage.

Claims (6)

In a multilayer film reflector comprising a multilayer film formed by alternately and periodically depositing at least two types of layers containing a predetermined substance as a main component on the substrate surface,
A multilayer reflector according to claim 1, wherein a diffusion prevention layer having at least one of a material and a thickness different from each other is formed based on a predetermined substance that forms a lower layer film for each interface of the multilayer film.   2. The multilayer film reflection according to claim 1, wherein the multilayer film is configured by alternately and periodically forming a layer mainly composed of the substance 1 and a layer mainly composed of the substance 2. mirror.   The multilayer reflector according to claim 2, wherein the substance 1 is Mo, and the substance 2 is Si.   4. The diffusion prevention layer according to claim 1, wherein the diffusion prevention layer includes at least one selected from the group consisting of carbon, carbide, oxide, nitride, and silicide. 5. Multilayer reflector.   5. The multilayer reflector according to claim 1, wherein the diffusion prevention layer has a thickness of 3 nm or less.   An exposure apparatus comprising the multilayer film reflecting mirror according to claim 1 in at least a part of an optical system.

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