JP2006049761A - Optical element, manufacturing method thereof, and projection aligner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical element which shows good reflection characteristics for an extended period, and also to provide a projection aligner which has the optical element keeping characteristics for an extend period built in as an projection optical system or the like. <P>SOLUTION: A protective layer 30 is provided as a top surface layer, which contains at least any one of silicon dioxide, alumina, chrome oxide, trichromic dioxide, chromium trioxide, zirconium dioxide, niobium oxide, niobium dioxide, diniobium pentoxite, molybdenum dioxide, ruthenium dioxide, ruthenium dioxide, ruthenium trioxide, ruthenium tetraoxide, dirhodium trioxide, and rhodium dioxide. Even if extreme ultraviolet ray is irradiated in a projection aligner, the oxidizing reaction on the surface of an optical element 50 is suppressed. Then a good reflection characteristics of the optical element 50 is maintained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical element for extreme ultraviolet light, a method for manufacturing the optical element, and a projection exposure apparatus using the optical element.

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 exposure apparatus is also a normal reflection type optical element from the viewpoint of securing transmittance. At this time, in order to achieve high reflectivity in an optical element or the like, it is common to alternately stack a material having a high refractive index and a material having a low refractive index on a substrate in a used wavelength region (Patent Document). 1).
Japanese Patent Laid-Open No. 2003-14893

  In the exposure apparatus, when the above-described optical element or the like is used under extreme ultraviolet rays, the environment is a vacuum, but oxygen and moisture cannot be completely excluded from the periphery of the optical element or the like. On the other hand, extreme ultraviolet light has very large energy. At this time, oxygen, moisture, etc. and the material on the surface of the optical element are irradiated with extreme ultraviolet rays to cause an oxidation reaction. When such oxidation gradually proceeds, the reflection characteristics of the optical element gradually deteriorate, and stable performance cannot be exhibited. Therefore, there arises a problem that the lifetime of the exposure apparatus is shortened by extending the optical element.

  Accordingly, an object of the present invention is to provide an optical element that exhibits good reflection characteristics over a long period of time. It is another object of the present invention to provide a projection exposure apparatus incorporating an optical element capable of maintaining characteristics over a long period of time as a projection optical system or the like.

  In order to solve the above problems, an optical element according to a first invention is provided on a supporting substrate, a multilayer film that is supported on the substrate and reflects extreme ultraviolet light, and an outermost layer of the multilayer film. And a protective layer containing an inorganic oxide for suppressing an oxidation reaction caused by the atmospheric gas, wherein the inorganic oxide is at least one selected from the group consisting of alumina, chromium oxide, trichromium dioxide, and chromium trioxide. It is.

  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. Moreover, in this invention, an optical element is equipped with the protective layer containing the alumina and other inorganic oxides for suppressing the oxidation reaction by atmospheric gas. Therefore, the protective layer containing the inorganic oxide serves as a barrier, for example, suppresses the oxidation reaction of water or oxygen remaining in the vacuum in the projection exposure apparatus on the surface of the optical element. By suppressing moisture and the like from entering the inside of the optical element and oxidizing the multilayer film, it is possible to prevent a decrease in reflectance due to oxidation of the optical element. Thus, the reflection characteristics of the entire optical element can be maintained. That is, the protective layer functions as an antioxidant film for the optical element. In this case, the protective layer tends to be stable as an oxide, and can be densely formed even if the protective layer is thin. In forming the protective layer, the protective layer can be formed by a two-step process in which a raw material, which will be described later, is formed and then oxidized, and it is easy to achieve complete oxidation of the protective layer. By completely oxidizing the protective layer, it is possible to prevent the refractive index and extinction coefficient of the outermost surface from changing, and further the reflection characteristics of the optical element from changing.

  In order to solve the above problems, an optical element according to a second invention is provided on a supporting substrate, a multilayer film that is supported on the substrate and reflects extreme ultraviolet light, and an outermost layer of the multilayer film. And a protective layer containing an inorganic oxide for suppressing an oxidation reaction caused by an atmospheric gas. The inorganic oxide includes zirconium dioxide, niobium oxide, niobium dioxide, niobium pentoxide, molybdenum dioxide, ruthenium dioxide, It is at least one selected from the group consisting of ruthenium oxide, ruthenium tetroxide, dirhodium trioxide and rhodium dioxide.

  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. Moreover, in this invention, an optical element is equipped with the protective layer containing a zirconium dioxide other inorganic oxide for suppressing the oxidation reaction by atmospheric gas. Therefore, the protective layer containing the inorganic oxide serves as a barrier, for example, suppresses the oxidation reaction of water or oxygen remaining in the vacuum in the projection exposure apparatus on the surface of the optical element. By suppressing moisture and the like from entering the inside of the optical element and oxidizing the multilayer film, it is possible to prevent a decrease in reflectance due to oxidation of the optical element. Thus, the reflection characteristics of the entire optical element can be maintained. That is, the protective layer functions as an antioxidant film for the optical element. In this case, the protective layer tends to be stable as an oxide. Further, light absorption by the protective layer can be extremely reduced, and it is suitable as an antioxidant film for optical elements. In forming the protective layer, the protective layer can be formed by a two-step process in which a raw material, which will be described later, is formed and then oxidized, and it is easy to achieve complete oxidation of the protective layer. When the protective layer is completely oxidized, it is possible to prevent the refractive index and extinction coefficient of the outermost surface from changing, and further the reflection characteristics of the optical element from changing.

  According to a third invention, in the optical element according to the first and second inventions, the multilayer film is different from the first layer made of a material having a small refractive index difference with respect to the refractive index of vacuum in the extreme ultraviolet region, and the refractive index difference. Second layers made of a material having a large thickness are alternately stacked on the substrate. In this case, it is possible to increase the reflectance of extreme ultraviolet rays by alternately laminating a multilayer film of several to several hundred layers with a predetermined film thickness so that each multilayer film is adapted to the intended extreme ultraviolet rays. . The optical element has, for example, a multilayer film made of Mo / Si on a substrate made of glass or the like in order to improve its reflection characteristics. The Mo layer has a relatively small refractive index, while the Si layer has a relatively large refractive index with respect to the incident extreme ultraviolet rays. It is possible to increase the reflectance of extreme ultraviolet light by alternately laminating these as a multilayer film of several to several hundred layers with a predetermined film thickness.

  In order to solve the above problems, an optical element manufacturing method according to a fourth aspect of the present invention includes a multilayer film manufacturing process in which a multilayer film is formed by alternately stacking substances having different refractive indexes, and an atmosphere on the multilayer film. And a protective layer manufacturing step of manufacturing a protective layer containing an inorganic oxide for suppressing an oxidation reaction by gas.

  In the multilayer film production process, for example, it is possible to increase the reflectance of extreme ultraviolet light by alternately laminating two types of substances with a predetermined film thickness as several to several hundreds of multilayer films to produce a multilayer film. It becomes. Further, the antioxidant film of the optical element can be relatively easily manufactured by the protective layer manufacturing process, and the optical element can stably maintain the optical characteristics (particularly the reflection characteristics in this case) for a long period of time. it can. More specifically, in the protective layer preparation step, for example, as the inorganic oxide, alumina, chromium oxide, trichromium dioxide, chromium trioxide, zirconium dioxide, niobium oxide, niobium dioxide, niobium pentoxide, molybdenum dioxide, dioxide dioxide, etc. By using one of ruthenium, ruthenium trioxide, ruthenium tetroxide, dirhodium trioxide, and rhodium dioxide, a protective layer containing this as the main component can be used to suppress oxidation reactions caused by atmospheric gases. It becomes. As described above, the optical element can be prevented from being oxidized while maintaining the reflectance of extreme ultraviolet rays.

  According to a fifth aspect of the present invention, in the method for manufacturing an optical element according to the fourth aspect of the present invention, the protective layer preparation step forms a inorganic material layer as a raw material constituting the protective layer on the multilayer film. And an oxidation step of forming a protective layer on at least a surface portion of the inorganic material layer by oxidizing the raw material to an inorganic oxide. In this case, the protective layer to be produced is first produced by forming an inorganic material as a raw material on the multilayer film by sputtering or the like in the film forming step, and oxidizing the completed inorganic material layer in the next oxidation step. Is done.

  According to a sixth aspect of the present invention, in the method for manufacturing an optical element according to the fourth aspect of the invention, the protective layer manufacturing step includes a film forming step of forming an inorganic material layer made of an inorganic oxide on the multilayer film, and an inorganic layer. And an oxidation step of forming a protective layer on at least the surface portion of the inorganic material layer by further oxidizing the oxide. In this case, the protective layer to be manufactured is prepared by first forming an inorganic oxide on the multilayer film by sputtering or the like in the film forming step, and further oxidizing the completed inorganic material layer in the next oxidation step. The

  According to a seventh aspect of the present invention, in the oxidation step of the optical element manufacturing methods according to the fifth and sixth aspects, the atmosphere and beam containing oxygen with respect to the inorganic material layer while maintaining the substrate at a low temperature below a predetermined temperature. Hit one of them. In this case, since the optical element does not reach a predetermined temperature or higher, damage to the multilayer film or the like due to heating can be prevented when oxidizing the inorganic material layer.

  Moreover, 8th invention oxidizes an inorganic material layer by exposure in any one of oxygen, ozone, and an oxygen radical in the oxidation process of the manufacturing method of the optical element which concerns on 5th-7th invention. In this case, since sufficient oxidation can be achieved at a low temperature, it is possible to form a protective layer having a desired thickness while preventing damage to the optical element due to heating.

  According to a ninth aspect, in the optical element manufacturing method according to the eighth aspect, ozone and oxygen radicals are generated by either ultraviolet irradiation or plasma formation in an oxygen atmosphere. In this case, a necessary oxidation reaction can be obtained while preventing damage to the optical element due to heating in the oxidation step for forming a protective layer having a desired film thickness.

  In order to solve the above-described problems, a projection exposure apparatus according to a tenth aspect of the present invention includes a light source that generates extreme ultraviolet light, an illumination optical system that guides the extreme ultraviolet light from the light source to a transfer mask, and a mask pattern image. Is formed on the sensitive substrate, and at least one of the mask, the illumination optical system, and the projection optical system includes the optical element according to any one of the first to third inventions.

  The projection exposure apparatus uses the optical element according to any one of the first to third inventions, and in the apparatus, oxygen, moisture, and the substance on the surface of the optical element are irradiated with extreme ultraviolet rays to oxidize the reaction. Therefore, the reflection characteristics of the optical element can be maintained over a long period of time, and the optical element has a long life.

[First Embodiment]
FIG. 1 is a sectional view showing the structure of an optical element 50 according to the first embodiment of the present invention. The optical element 50 is a concave reflecting mirror, and includes a substrate 10 serving as a base material that supports a multilayer film structure, a multilayer film 20 for reflection, and a protective layer 30 serving as a surface layer. The multilayer film 20 is a multilayer film of several to several hundred layers formed by, for example, alternately laminating two kinds of substances having different refractive indexes on the substrate 10. The two types of thin film layers L1 and L2 constituting the multilayer film 20 can be, for example, a Mo layer and a Si layer.

  For the multilayer film 20 on the substrate 10, in order to increase the reflectivity of the optical element 50, which is a reflecting mirror, a large number of less absorbing materials are stacked, and based on the optical interference theory so that the phases of the reflected waves match each other. The film thickness of each layer is adjusted. That is, for the extreme ultraviolet wavelength region used in a projection exposure apparatus or the like, the thin film layer L1 (Mo layer in the specific example) having a relatively low refractive index and the thin film layer L2 (in the specific example, Si layer) having a relatively high refractive index. The multilayer film 20 is fabricated on the substrate 10 by a multilayer film fabrication process in which the layers of the reflected waves are alternately laminated in a predetermined film thickness or in an arbitrary order so that the phases of the reflected waves are in phase.

The multilayer film 20 may further include a diffusion prevention film (not shown) 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. As a result, the reflection characteristics are affected, and the reflectance of the optical element 50 may decrease. Therefore, in order to clarify the interface, a diffusion preventing film is further provided between the thin film layer L1 and the thin film layer L2 in forming the multilayer film 20. For example, B ₄ C, C, MoC, or the like is used as the material. By clarifying the interface in this way, the reflection characteristics of the optical element 50 are improved.

  In the present embodiment, the optical element 50 further includes a protective layer 30 on the outermost layer of the multilayer film 20. This protective layer 30 is formed of a material containing an inorganic oxide. More specifically, the protective layer 30 is formed of an inorganic oxide as a whole, and the inorganic oxide is at least one of silicon dioxide, alumina, chromium oxide, trichromium dioxide, and chromium trioxide. As a main component, it serves as an antioxidant film. Since these substances are both chemically stable oxides, they themselves are not easily oxidized even under extreme ultraviolet rays, and deterioration due to oxidation of the multilayer film 20 therebelow can be prevented. In particular, these substances can form a dense film even if they are thin, so that oxygen and water are difficult to pass through, and have a role of preventing oxidation from proceeding to the inside. Moreover, since the film thickness can be reduced, it is possible to suppress the deterioration of the reflection characteristics of the optical element 50 caused by absorption of extreme ultraviolet rays by the protective layer 30 or the like. As one standard for maintaining the characteristics, it is considered that if the film thickness of the protective layer 30 is 4 nm or less, a decrease in reflectance due to light absorption can be sufficiently suppressed.

  Further, as another aspect of forming the optical element 50, the inorganic oxide to form the protective layer 30 is zirconium dioxide, niobium oxide, niobium dioxide, niobium pentoxide, molybdenum dioxide, ruthenium dioxide, ruthenium trioxide, quaternary. It may contain at least one of ruthenium oxide, dirhodium trioxide, and rhodium dioxide. In this case, it also serves as an antioxidant film. Since these substances are both chemically stable oxides, they themselves are not easily oxidized even under extreme ultraviolet rays, and deterioration due to oxidation of the multilayer film 20 therebelow can be prevented. In addition, even if the oxide is an oxide, light absorption is particularly small, and the oxide is excellent as an antioxidant film that covers the surface of the optical element 50. In particular, even when the above-described oxide is used, it is considered that the reduction in reflectance due to light absorption can be more reliably suppressed if the thickness of the protective layer 30 is 4 nm or less as one reference for maintaining the characteristics. .

  2 and 3 are diagrams for explaining one mode of a protective layer manufacturing process for forming the protective layer 30. FIG. FIG. 2 is a diagram schematically illustrating the structure of a film forming apparatus 60 for performing a film forming process for forming the inorganic material layer 41 on the multilayer film 20 in the protective layer manufacturing process. In the present embodiment, magnetron sputtering is used as an aspect of the film forming method. FIG. 3 is a diagram schematically illustrating the structure of an oxide film forming apparatus 70 for performing an oxidation process for completing the protective layer 30 by oxidizing the inorganic material layer 41 in the protective layer manufacturing process. The protective layer 30 is produced on the surface of the optical element 50 through these two steps. By making the process into two stages, first, in the film forming process, the inorganic oxide is not formed directly, but the film is formed with raw materials such as metal before being oxidized, so that a denser film can be formed. Become. Further, in the subsequent oxidation step, the oxidation step can be performed at a low temperature by being exposed to oxygen gas, ozone, or oxygen radicals.

  First, the film forming process in this embodiment will be described. A film forming apparatus 60 shown in FIG. 2 includes a vacuum chamber 61 as a film forming chamber, a stage 62, a permanent magnet 64, a backing metal 65, a matching circuit 67, a high-frequency power source 68, and a sputtering gas inlet GI. And an exhaust port GE.

  The stage 62 is disposed on the vacuum chamber 61 and serves as an anode 63 that supports the processing target 40 (the optical element 50 before the protective layer 30 is formed) and is applied with a positive voltage. The permanent magnet 64 is disposed below the vacuum chamber 61 so as to face the stage 62, and forms a magnetic field for increasing the sputtering efficiency. The backing metal 65 is installed on the permanent magnet 64 and serves as a cathode 66 that supports a target 69 that is a raw material of the protective layer 30 and to which a negative voltage is applied. The high frequency power supply 68 supplies high frequency power impedance-matched via the matching circuit 67. The sputtering gas inlet GI is installed on the side wall of the vacuum chamber 61 and introduces the sputtering gas. Similarly to the sputtering gas introduction port GI, the exhaust port GE is also connected to an exhaust device (not shown) that is installed on the side wall of the vacuum chamber 61 and exhausts air.

  The processing target 40 fixed on the stage 62 in the vacuum chamber 61 is a stage in which the multilayer film 20 is laminated on the substrate 10. On the other hand, the target 69 disposed facing the stage 62 is a metal or the like that is a raw material for forming the protective layer 30.

  First, as a previous step, the vacuum chamber 61 is evacuated using an exhaust device (not shown) connected to the exhaust port GE. At this time, the processing target 40 is placed on the stage 62 in the vacuum chamber 61. Next, a predetermined amount of sputtering gas such as Ar gas is introduced into the vacuum chamber 61 from the sputtering gas inlet GI, and the pressure of the sputtering gas in the vacuum chamber 61 is set to a desired value. Next, the power output from the high-frequency power supply 68 is applied to the target 69 through the backing metal 65 while impedance matching is performed by the matching circuit 67, thereby generating plasma around the target 69. At this time, the density of the plasma is increased by the permanent magnet 64, and sputtering is performed efficiently, and an inorganic material layer 41 that is a raw material of the protective layer 30 is formed on the processing target 40.

  Next, the oxidation process in this embodiment will be described. The oxide film forming apparatus 70 shown in FIG. 3 includes a vacuum chamber 71, a stage 72, an oxidizing gas introduction port RI, an exhaust port RE, and an oxidizing gas supply device 73.

  The stage 72 is disposed above (or below) the vacuum chamber 71 and supports the processing target 140 (the optical element 50 during the formation of the protective layer 30). The oxidizing gas inlet RI is connected to an oxidizing gas supply device 73 that supplies oxygen gas or the like serving as an oxidizing gas, and introduces the oxidizing gas into the vacuum chamber 71. The exhaust port RE is connected to an exhaust device (not shown) for exhausting oxidizing gas or the like. The processing target 140 fixed on the stage 72 in the vacuum chamber 71 is obtained by depositing the inorganic material layer 41 on the multilayer film 20 provided on the substrate 10.

  First, as a previous step, the vacuum chamber 71 is evacuated using an exhaust device (not shown) connected to the exhaust port RE. At this time, the processing target 140 is placed on the stage 72 in the vacuum chamber 71. Next, a predetermined amount of oxygen gas is introduced into the vacuum chamber 71 from the oxidizing gas inlet RI, and the pressure of the oxygen gas in the vacuum chamber 71 is set to a desired value. Thereby, the protective layer 30 which consists of the inorganic oxide which exposed the inorganic material layer 41 to oxygen gas and oxidized the inorganic material layer 41 is produced. Here, when ozone and oxygen radicals are used as the oxidizing gas instead of oxygen gas, ozone is generated by irradiating the oxygen gas with ultraviolet rays in the vacuum chamber 71, or oxygen gas is generated by high frequency or the like. By further providing an activation device 74 for generating plasma, ozone or oxygen radicals are generated. Alternatively, the activation device 74 as described above does not need to be installed in the vacuum chamber 71, and the oxygen gas is irradiated into the oxygen gas in the oxidizing gas supply device 73, or the oxygen gas is turned into plasma by high frequency or the like. Further, ozone or oxygen radicals can be generated and sent into the vacuum chamber 71 through the oxidizing gas inlet RI.

  Note that, as an oxidation process different from the present embodiment, a raw material such as a metal can be oxidized by irradiation with an oxygen ion beam. In this case, the inorganic material layer 41 is accurately oxidized by irradiation with an oxygen ion beam.

  In the present embodiment, the two steps shown in FIGS. 2 and 3 are performed by different devices. However, these steps may be performed as an integrated device connected via an openable / closable partition wall, for example. Absent. In this case, after forming the film in the film forming process, the processing object 40 can be moved from the vacuum chamber 61 to the vacuum chamber 71 without exposing to the atmosphere, and therefore the multilayer film 20 is deteriorated before the protective layer 30 is formed. Can be prevented. Further, in the two steps, if the atmosphere of the sputtering gas or oxidizing gas has little influence on each device in the optical element and the vacuum chamber, the two steps can be performed in one device. is there. In this case, for example, the vacuum chamber 61 and the vacuum chamber 71 are the same, and all the parts in FIGS. 2 and 3 are accommodated in one apparatus.

  In this embodiment, the magnetron sputtering method is used in the film forming step. However, in the film forming step, if a fine film can be formed without deteriorating the surface roughness, film forming techniques such as vapor deposition and other sputtering methods are used. It doesn't matter. For example, it is possible to form a film by ion beam sputtering.

  Further, another material may be formed between the protective layer 30 and the outermost surface layer of the multilayer film 20 in order to help form a delicate film without deteriorating the surface roughness.

[Second Embodiment]
In this embodiment, an inorganic oxide is used in the film forming process. In the film forming process of the first embodiment, the inorganic oxide is not directly formed, but is formed using a raw material such as a metal before being oxidized. If film formation is possible, an inorganic oxide may be used in the film formation step.

  Since the apparatus used in this embodiment is the same as that in the first embodiment, it is assumed that FIG. In FIG. 2, as the inorganic oxide used for the target 69 which is a film forming material, in this embodiment, in particular, alumina, chromium oxide, trichromium dioxide, chromium trioxide, zirconium dioxide, niobium oxide, niobium dioxide, dioxide pentoxide. One of niobium, molybdenum dioxide, ruthenium dioxide, ruthenium trioxide, ruthenium tetroxide, rhodium trioxide and rhodium dioxide is used. These are formed by a film forming process. If the composition of the inorganic material layer 41 after film formation is not a chemically stable oxide, the protective layer 30 is formed by performing the same oxidation process as in the first embodiment using the same apparatus as in FIG. Is done.

  Conventionally, as a method for forming an oxide layer, for example, (a) a method using an inorganic substance or a mixture as a target and mixing an oxygen gas or the like into a sputtering gas to synthesize oxide at the time of film formation, (b) a target Method of using oxide itself (c) There is a method of forming a film by using the oxide itself as a target and mixing oxygen gas into the sputtering gas. However, the oxide layer formed is unstable in any method. There is a possibility. However, in the present embodiment, after the film formation process, if necessary, an oxidation process is further included, so that after the film formation, the inorganic material layer 41 is formed by the oxidation process even if the oxidation is not sufficient. It can be oxidized sufficiently, the chemical composition can be established, and a stable oxide can be formed, and the desired protective layer 30 can be formed.

[Third Embodiment]
FIG. 4 is a view for explaining the structure of a projection exposure apparatus according to the third embodiment in which the optical element according to the first or second embodiment is incorporated as an optical component.

The projection exposure apparatus mainly includes an extreme ultraviolet light source S, a condenser C, illumination optical systems IR _{1 to} IR ₄ , a stage MST that supports a mask M, projection optical systems PR _{1 to} PR ₄ , and a sensitive substrate (wafer) WA. It is configured by a supporting stage WST or the like.

  The extreme ultraviolet light source S is provided with a laser light source L that generates laser light for plasma excitation and a tube T that supplies a gas such as a target material such as xenon into the housing SC. By condensing the laser light from the laser light source L onto xenon emitted from the tip of the tube T, the target material in that portion is turned into plasma and emits extreme ultraviolet rays. The capacitor C collects extreme ultraviolet light generated at the tip of the tube T. The extreme ultraviolet rays that have passed through the capacitor C are converged and emitted to the outside of the housing SC and enter the collimator mirror CM. In place of the laser plasma light source as described above, emitted light from a discharge plasma light source, a SOR light source, or the like can be used.

The illumination system optical elements IR _{1 to} IR ₄ are constituted by reflective optical integral IR ₁ , IR ₂ , condenser mirror IR _{3, and the} like. The illumination system optical elements IR _{1 to} IR ₄ can uniformly illuminate a predetermined region on the mask M with extreme ultraviolet rays having a desired wavelength.

  Since there is no completely transparent substance in the extreme ultraviolet wavelength region, a reflective mask is used as the mask M instead of a transmissive mask.

The projection optical systems PR _{1 to} PR ₄ are usually composed of a plurality of multilayer mirrors and the like. The circuit pattern formed on the mask M forms an image on the wafer WA coated with the resist by such projection optical systems PR _{1 to} PR ₄ and is transferred to the resist. Although extreme ultraviolet rays are absorbed and attenuated by the atmosphere, the entire apparatus is covered with a vacuum chamber VC, and the optical path of extreme ultraviolet rays is maintained at a predetermined degree of vacuum (for example, 1.3 × 10 ⁻³ Pa or less). Therefore, the attenuation of extreme ultraviolet rays is reduced.

In the above projection exposure apparatus, the condenser C, the collimator mirror CM, the illumination system optical elements IR _{1 to} IR ₄ , the mask M, or the projection optical systems PR _{1 to} PR ₄ are exemplified in the first or second embodiment. An optical element 50 is used. At this time, the shape of the optical surface of the optical element 50 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.

  In the projection exposure apparatus described above, an optical element with high reflectivity and high precision is used, so that an oxidation reaction on the surface of the optical element in the projection exposure apparatus can be suppressed, and reflection of the optical element can be suppressed. It is possible to prevent the characteristics from deteriorating and thereby to prolong the life of the projection exposure apparatus.

It is sectional drawing which shows the one aspect | mode of the structure of the optical element which concerns on 1st Embodiment. It is a figure for demonstrating the film-forming process of the protective layer preparation processes. It is a figure for demonstrating the oxidation process among protective layer preparation processes. It is a figure of the projection exposure apparatus which concerns on 3rd Embodiment incorporating the optical element which concerns on 1st Embodiment etc. as an optical component.

Explanation of symbols

DESCRIPTION OF SYMBOLS 50 ... Optical element, 30 ... Protective layer, 20 ... Multilayer film, 10 ... Substrate, L1, L2 ... Thin film layer, 40, 140 ... Process object, 41 ... Inorganic material layer, 60 ... Film-forming apparatus, 61, 71 ... Vacuum Chamber, 62, 72 ... Stage, 64 ... Permanent magnet, 65 ... Backing metal, 67 ... Matching circuit, 68 ... High frequency power supply, 69 ... Target, GI ... Sputter gas introduction port, GE, RE ... Exhaust port, 70 ... Oxide film forming apparatus, 73 ... oxidizing gas supply device, 74 ... activation device, RI ... oxidizing gas inlet, S ... extreme ultraviolet light source, C ... capacitor, _IR 1 ~IR 4 _... illumination optical system, M ... mask, MST, WST ... stage, _PR 1 ~PR 4 _... projection optical system, WA ... wafer

Claims (10)

A supporting substrate;
A multilayer film supported on the substrate and reflecting extreme ultraviolet light;
Provided on the outermost layer of the multilayer film, and a protective layer containing an inorganic oxide for suppressing an oxidation reaction by an atmospheric gas,
The optical element, wherein the inorganic oxide is at least one selected from the group consisting of alumina, chromium oxide, trichromium dioxide, and chromium trioxide. A supporting substrate;
A multilayer film supported on the substrate and reflecting extreme ultraviolet light;
Provided on the outermost layer of the multilayer film, and a protective layer containing an inorganic oxide for suppressing an oxidation reaction by an atmospheric gas,
The inorganic oxide is at least one selected from the group consisting of zirconium dioxide, niobium oxide, niobium dioxide, niobium pentoxide, molybdenum dioxide, ruthenium dioxide, ruthenium trioxide, ruthenium tetroxide, rhodium trioxide and rhodium dioxide. An optical element characterized by the above.   The multilayer film is formed by alternately laminating a first layer made of a material having a small refractive index difference with respect to a vacuum refractive index in an extreme ultraviolet region and a second layer made of a material having a large refractive index difference on a substrate. The optical element according to any one of claims 1 and 2. A multilayer film production process for producing a multilayer film by alternately laminating substances having different refractive indexes;
On the multilayer film, a protective layer production step of producing a protective layer containing an inorganic oxide for suppressing an oxidation reaction caused by an atmospheric gas;
The manufacturing method of the optical element which has these. The protective layer manufacturing step includes
A film forming step of forming an inorganic material layer as a raw material constituting the protective layer on the multilayer film;
Oxidizing the raw material into an inorganic oxide to produce the protective layer on at least the surface portion of the inorganic material layer; and
The manufacturing method of the optical element of Claim 4 containing this. The protective layer manufacturing step includes
A film forming step of forming an inorganic material layer made of an inorganic oxide on the multilayer film;
An oxidation step of producing the protective layer on at least a surface portion of the inorganic material layer by further oxidizing the inorganic oxide;
The manufacturing method of the optical element of Claim 4 containing this.   Either of the atmosphere and the beam containing oxygen are applied to the inorganic material layer while the substrate is kept at a low temperature equal to or lower than a predetermined temperature in the oxidation step. The manufacturing method of the optical element of description.   8. The method of manufacturing an optical element according to claim 5, wherein, in the oxidation step, the inorganic material layer is oxidized by exposure to any one of oxygen, ozone, and oxygen radicals. 9.   9. The method of manufacturing an optical element according to claim 8, wherein the ozone and oxygen radical are generated by either ultraviolet irradiation or plasma formation in an oxygen atmosphere. 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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