JP2007027226A - Reflecting optical system, illumination optical device, and exposure apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflecting optical system which can bend an extremely-short ultraviolet ray at a desired angle while suppressing an imbalance of polarization properties of the extremely-short ultraviolet ray and a loss of light intensity. <P>SOLUTION: The reflecting optical system 4 which bends the traveling direction of an extremely-short ultraviolet ray at a predetermined angle includes a first multilayer film mirror 4a into which the extremely-short ultraviolet ray is incident at a predetermined angle, and a second multilayer film mirror 4b into which the extremely-short ultraviolet ray reflected by the first multilayer film mirror 4a is incident at a predetermined angle. The traveling direction of the extremely-short ultraviolet ray incident into the first multilayer film mirror 4a and that of the extremely-short ultraviolet ray reflected by the second multilayer film mirror 4b form an angle θ which is larger than 70° and smaller than 110°. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a reflection optical system used in lithography such as a semiconductor integrated circuit, an illumination optical apparatus including the reflection optical system, and an exposure apparatus including the reflection optical system.

  In an exposure apparatus that uses extremely short ultraviolet light (EUV light, wavelength 1 nm to 100 nm) as exposure light, there is no material that transmits and refracts EUV light, so the optical system is composed of multilayer mirrors utilizing the interference effect. ing. The reflectance of light with respect to the multilayer mirror varies depending on the polarization of incident light. When light enters the multilayer mirror at an incident angle other than oblique incidence, the reflectance of S-polarized light is usually higher than that of P-polarized light. Further, when the P-polarized light is incident at an angle called a Brewster angle near an incident angle of 45 °, the reflectance becomes zero. That is, when light is incident on the multilayer mirror at an incident angle of 45 °, the light reflected by the multilayer mirror becomes light containing almost only S-polarized light regardless of the degree of polarization of the incident light. Since an illumination optical system used in an exposure apparatus requires a high balance of polarization characteristics, EUV light is incident on a multilayer mirror at an incident angle of 45 ° and is not bent at a substantially right angle (for example, Patent Documents). 1).

International Publication No. 2004/090955 Pamphlet

  By the way, when the light traveling direction is bent at a substantially right angle, light is incident on one multilayer mirror at an incident angle of 45 °, and two or more multilayer mirrors are used so that the incident angle is 45 ° on the multilayer mirror. It is conceivable that the light is incident at an incident angle other than. However, since the reflectance of S-polarized light of EUV light with respect to the multilayer mirror is higher than that of P-polarized light, increasing the number of multilayer mirrors increases the degree of polarization of S-polarized light of EUV light. The polarization characteristic balance of the optical system is further deteriorated. Further, for example, when EUV light having a wavelength of about 13.5 nm is used, the reflectance of the Mo / Si multilayer mirror used for EUV light is 60 to 70%, so that the number of multilayer mirrors can be increased. The loss of the amount of EUV light is large, leading to a reduction in throughput of the entire illumination optical system. Therefore, in order to avoid the deterioration of the polarization property balance and the decrease in the throughput, the optical system using EUV light (particularly the illumination optical system) does not employ an optical system that bends the EUV light substantially at right angles. The degree of freedom of system design and configuration was lost.

  An object of the present invention is to provide a reflection optical system that can bend the ultrashort ultraviolet light at a desired angle while suppressing deterioration in the polarization characteristic balance of the ultrashort ultraviolet light and loss of the amount of light, and an illumination equipped with the reflection optical system An optical apparatus and an exposure apparatus provided with the reflection optical system are provided.

  The reflective optical system according to the present invention is a reflective optical system that bends the traveling direction of ultrashort ultraviolet light at a predetermined angle. The first multilayer mirror that makes the ultrashort ultraviolet light incident at a predetermined angle; A second multilayer mirror that makes the ultra-short ultraviolet light reflected by the multilayer mirror incident at a predetermined angle, and a traveling direction of the ultra-short ultraviolet light incident on the first multilayer mirror; The angle θ formed with the traveling direction of the ultra-short ultraviolet light reflected by the second multilayer mirror is 70 ° <θ <110 °.

  An illumination optical apparatus according to the present invention is an illumination optical apparatus that illuminates a surface to be irradiated with ultrashort ultraviolet light emitted from a light source, and includes the reflection optical system according to the present invention.

  The exposure apparatus of the present invention is an exposure apparatus for exposing a predetermined pattern illuminated by ultrashort ultraviolet light emitted from a light source on a photosensitive substrate, and includes the reflective optical system of the present invention. .

  According to the reflection optical system of the present invention, two multilayer mirrors are compared with the polarization characteristics of the ultrashort ultraviolet light when the traveling direction of the ultrashort ultraviolet light is bent at a substantially right angle by using one multilayer mirror. The polarization characteristic balance of the ultra-short ultraviolet light is good when the traveling direction of the ultra-short ultraviolet light is bent at a substantially right angle (70 ° <θ <110 °). That is, the ultrashort ultraviolet light can be bent to a desired angle while maintaining a good balance between the S-polarized component and the P-polarized component of the ultrashort ultraviolet light.

  Compared with the reflectivity and polarization characteristics of ultra-short ultraviolet light after bending the traveling direction of ultra-short ultraviolet light substantially at right angles using one multi-layer mirror, it is extremely short using two multi-layer mirrors. The reflectivity of the ultrashort ultraviolet light after the ultraviolet light traveling direction is bent at a substantially right angle (77 ° <θ <97 °) becomes high, and the polarization characteristic balance becomes good. That is, the ultrashort ultraviolet light can be bent at a desired angle while maintaining a good balance between the S-polarized component and the P-polarized component of the ultrashort ultraviolet light and a high reflectance of the ultrashort ultraviolet light.

  Further, according to the illumination optical apparatus of the present invention, since the reflection optical system of the present invention is provided, a good balance between the S-polarized component and the P-polarized component of the ultrashort ultraviolet light and a high reflectivity of the ultrashort ultraviolet light While maintaining the above, it is possible to bend the ultra-short ultraviolet light at a desired angle. Accordingly, it is possible to increase the degree of freedom in the design and configuration of the optical system that guides the ultra-short ultraviolet light to the irradiated surface while suppressing the deterioration of the polarization characteristic balance of the ultra-short ultraviolet light and the loss of the light amount.

  Further, according to the exposure apparatus of the present invention, since the illumination optical system having the reflection optical system of the present invention is provided, a good balance between the S-polarized component and the P-polarized component of the ultrashort ultraviolet light and the ultrashort ultraviolet light Thus, it is possible to bend the ultra-short ultraviolet light at a desired angle while maintaining the high reflectance. Therefore, it is possible to increase the degree of freedom in the design and configuration of the illumination optical system while suppressing the deterioration of the polarization characteristic balance and the loss of the light amount of the ultrashort ultraviolet light, and to perform exposure with high throughput and high resolution. it can.

  A projection exposure apparatus according to a first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a projection exposure apparatus according to this embodiment.

  This projection exposure apparatus includes exposure light (illumination light) emitted by an illumination optical apparatus including a light source 2, a reflection optical system 4, a collector mirror 10, reflection type fly-eye optical systems 12, 14, condenser mirrors 18, 20, and the like. ), That is, formed on the mask M while moving the mask M and the wafer W relative to the reflective projection optical system PL using ultrashort ultraviolet light (hereinafter referred to as EUV light) having a wavelength of 13.5 nm. It is a step-and-scan exposure apparatus that exposes a predetermined pattern on a wafer W as a photosensitive substrate coated with a photosensitive material (resist).

  In this projection exposure apparatus, since the transmittance of EUV light as exposure light to the atmosphere is low, the optical path through which the EUV light passes is covered with a vacuum chamber (not shown).

  The light source 2 is a light source that emits EUV light, and a plasma light source or the like that generates plasma by laser or discharge is used. The central wavelength of EUV light is about 13.5 nm, and unpolarized light is guided to the reflection optical system 4.

  The EUV light reflected by a condensing mirror (not shown) provided in the light source 2 enters the reflection optical system 4 that bends the traveling direction of the EUV light to a predetermined angle. FIG. 2 is a diagram showing the configuration of the reflective optical system 4. As shown in FIG. 2, the EUV light is incident on the first multilayer mirror 4a constituting the reflection optical system 4 at an incident angle of 22.5 °. The first multilayer mirror 4a is a mirror of 50 layer pairs of Mo (molybdenum) / Si (silicon) multilayer films having a periodic length of 7.52 nm. In the Mo / Si layer pair, the Mo layer has a thickness of 2.63 nm, and the Si layer has a thickness of 4.89 nm. The configuration of the first multilayer mirror 4a is determined based on the wavelength and incident angle of the EUV light incident on the first multilayer mirror 4a so that the EUV light has the highest reflectance.

  Here, when the incident light enters the first multilayer mirror 4a at an incident angle of 22.5 °, the reflectance of the S-polarized light with respect to the first multilayer mirror 4a is 73.9%, and the reflection of the P-polarized light with respect to the first multilayer mirror 4a. The rate is 62.9%. Since the incident light (EUV light) is non-polarized light, the amount of S-polarized light with respect to the first multilayer mirror 4a is 50% and the amount of P-polarized light with respect to the first multilayer mirror 4a is 50%. The amount of S-polarized light of the EUV light reflected by the first multilayer mirror 4a is 50% × 0.739 (reflectance) = 37.0%, P-polarized light 50% × 0.629 (reflectance) = 31.5% It becomes.

  The EUV light reflected by the first multilayer mirror 4a enters the second multilayer mirror 4b at an incident angle of 22.5 °. The configuration of the multilayer film of the second multilayer mirror 4b is the same as the configuration of the multilayer film of the first multilayer mirror 4a. The configuration of the second multilayer mirror 4b is determined based on the wavelength and incident angle of the EUV light incident on the second multilayer mirror 4b so that the reflectance of the EUV light becomes the highest. Since the optical path of the EUV light is in the same plane, S-polarized light for the first multilayer mirror 4a becomes S-polarized light for the second multilayer mirror 4b, and P-polarized light for the first multilayer mirror 4a is for the second multilayer mirror 4b. P-polarized light. That is, the S polarized light for the first multilayer mirror 4a is reflected as S polarized light by the second multilayer mirror 4b, and the P polarized light for the first multilayer mirror 4a is reflected as P polarized light by the second multilayer mirror 4b. Therefore, the amount of S-polarized light of the EUV light reflected by the second multilayer mirror 4b is 37.0% (the amount of S-polarized light incident on the second multilayer mirror 4b) × 0.739 (reflectance) = 27. The amount of P-polarized light is 31.5% (the amount of P-polarized light when incident on the second multilayer mirror 4b) × 0.629 (reflectance) = 19.8%.

  The reflectivity of EUV light through the reflective optical system 4 (the first multilayer mirror 4a and the second multilayer mirror 4b) is 27.3% (S-polarized reflectance) + 19.8% (P-polarized reflectance). ) = 47.1%. Further, the degree of polarization of the EUV light is 0.16 (S-polarized light) from the balance between the amount of S-polarized light and P-polarized light of the EUV light via the reflective optical system 4. Further, the angle θ formed by the traveling direction of the EUV light incident on the first multilayer mirror 4a and the traveling direction of the EUV light reflected by the second multilayer mirror 4b is 90 °.

  The EUV light emitted from the reflection optical system 4 is collected at or near a second focal position of a collecting mirror (not shown) provided in the light source 2 and reflected by the collector mirror 10. The EUV light reflected by the collector mirror 10 is guided to the reflective fly's eye optical systems 12 and 14 as an optical integrator. The incident-side fly's eye mirror 12 is composed of element mirrors, which are a plurality of concave mirrors arranged in parallel, and is arranged at a position optically conjugate with the mask M surface and wafer W surface or in the vicinity thereof.

  The EUV light wave-divided by being incident on the incident-side fly-eye mirror 12 is reflected by the incident-side fly-eye mirror 12 and the other of the reflective fly-eye optical systems 12 and 14 constituting the reflective fly-eye optical systems 12 and 14 via the aperture stop 16. The light enters the exit-side fly-eye mirror 14. The exit-side fly-eye mirror 14 is composed of element mirrors that are a plurality of concave mirrors arranged in parallel corresponding to each of the plurality of element mirrors constituting the entrance-side fly-eye mirror 12, and includes the reflective projection optical system PL. It is arranged at a position optically conjugate with the pupil plane.

  A secondary light source composed of a large number of light source images is formed on or near the exit surface of the exit-side fly-eye mirror 14. The EUV light reflected by the emission side fly-eye mirror 14 enters the condenser mirror 18 through the aperture stop 16. The EUV light incident on the condenser mirror 18 is reflected by the condenser mirror 18 and the condenser mirror 20 and is condensed on the mask M. The EUV light that passes through the illumination optical system including the reflective optical system 4, the collector mirror 10, the reflective fly-eye optical systems 12 and 14, and the condenser mirrors 18 and 20 is a reflective mask on which a predetermined circuit pattern is formed. Uniformly illuminate over M.

  The collector mirror 10, the reflective fly's eye optical systems 12, 14, and the condenser mirror 18 use glass, ceramics, metal, or the like as a substrate, and a multilayer made of molybdenum (Mo) and silicon (Si) on the substrate. A film is formed.

  The EUV light reflected by the reflective mask M forms a secondary light source image at the pupil of the reflective projection optical system PL, and a pattern formed on the mask M on the wafer W as a photosensitive substrate coated with a resist. Project and expose the image.

  According to the reflection optical system according to the first embodiment, two multilayers are compared with the reflectance of EUV light when the traveling direction of the EUV light is bent at a substantially right angle by using one multilayer mirror. Even though the film mirrors (the first multilayer film mirror and the second multilayer film mirror) are used to fold the traveling direction of the EUV light at a substantially right angle, the reflectance of the EUV light becomes high. Compared with the polarization characteristics of EUV light after folding the EUV light in a substantially right angle using one multilayer mirror, the EUV light in the substantially right angle using two multilayer mirrors. The polarization characteristic balance of the EUV light after bending is good.

  As a comparative example, consider a case where EUV light (non-polarized light) having a wavelength of 13.5 nm is incident on a single multilayer mirror and is bent at a substantially right angle. The period of the multilayer film and the thickness and material of each layer are optimized so as to maximize the reflection angle. A 1 nm Mo (thickness 3.54 nm) / Si (thickness 6.57 nm) multilayer film was used. The reflectance of S-polarized light to this multilayer mirror is 72.4%, and the reflectance of P-polarized light is 5.5%. Since the EUV light incident on the multilayer mirror is non-polarized, if the light quantity of S-polarized light is 50% and the light quantity of P-polarized light is 50%, the light quantity of S-polarized light reflected by the multilayer mirror is 50% × 0.724 (reflectance) = 36.2%, and the amount of P-polarized light is 50% × 0.055 (reflectance) = 2.8%. Therefore, the amount of EUV light reflected by this multilayer mirror is 39.0% in total of the amount of S-polarized light and P-polarized light, that is, the reflection of EUV light reflected by the multilayer mirror at an incident angle of 45 °. The rate is 39.0% for non-polarized incidence. In addition, the degree of polarization of the EUV light reflected by the multilayer mirror is 0.86 (S-polarized light) due to the balance between the amounts of S-polarized light and P-polarized light of the EUV light.

  On the other hand, the reflectance of EUV light reflected by the reflective optical system (two multilayer mirrors) according to the first embodiment is 47.1% as described above in the case of non-polarized incidence, The reflectance of EUV light becomes higher than when EUV light is bent at a substantially right angle by the multilayer mirror. Further, the degree of polarization of the EUV light reflected by the reflecting optical system according to the first embodiment is 0.16 (S-polarized light) as described above, and the EUV light is substantially perpendicular by one multilayer mirror. The polarization characteristic balance of EUV light is better than that of the case where it is bent.

  Therefore, according to the projection exposure apparatus according to the first embodiment, the EUV light is bent substantially at a right angle while maintaining a high reflectance of the EUV light and a good balance between the S-polarized component and the P-polarized component. be able to. That is, it is possible to increase the degree of freedom in the design and configuration of the illumination optical system while suppressing the loss of the EUV light amount and the deterioration of the polarization characteristic balance, and it is possible to perform exposure with high throughput and high resolution.

  In the reflective optical system according to the first embodiment, the traveling direction of the EUV light is bent at a substantially right angle, but the traveling direction of the EUV light incident on the reflective optical system and the EUV light emitted from the reflective optical system. The angle θ formed with the light traveling direction may be in the range of 70 ° <θ <110 °. FIG. 3 is a graph showing the angle between the incident light and the outgoing light to the reflection optical system and the polarization degree of S-polarized light at that time. As shown in FIG. 3, within the range of 70 ° <θ <110 °, the degree of polarization of the EUV light is compared with the case where the traveling direction of the EUV light is bent at the same angle by one multilayer mirror. Since it can improve 0.1 or more, the polarization characteristic of EUV light is maintained with good balance.

  FIG. 4 is a graph showing the angle formed between the incident light and the outgoing light to the reflective optical system, and the transmittance (reflectance) of the EUV light at that time. As shown in FIG. 4, when the angle θ between the traveling direction of the EUV light incident on the reflective optical system and the traveling direction of the EUV light emitted from the reflective optical system is within a range of 77 ° <θ <97 °, Compared to the case where the traveling direction of EUV light is bent at the same angle by a single multilayer mirror, the degree of polarization of EUV light is improved by 0.36 or more, and the polarization characteristics of EUV light are maintained in a well-balanced manner. In addition, the transmittance (reflectance) of EUV light is also increased.

  Next, a projection exposure apparatus according to a second embodiment of the present invention will be described with reference to the drawings. The configuration of the projection exposure apparatus according to the second embodiment is the same as that of the reflection optical system 4 (see FIGS. 5 to 5) that constitutes the projection exposure apparatus according to the first embodiment shown in FIG. (See FIG. 7). Therefore, in the description of the second embodiment, a detailed description of the same configuration as the configuration of the projection exposure apparatus according to the first embodiment is omitted. In the description of the projection exposure apparatus according to the second embodiment, the same reference numerals as those used in the first embodiment are used for the same configuration as the projection exposure apparatus according to the first embodiment. A description will be given using. In the following description, the XYZ orthogonal coordinate system shown in FIG. 1 is set, and the positional relationship of each member will be described with reference to this XYZ orthogonal coordinate system. The XYZ orthogonal coordinate system is set so that the X axis and the Y axis are parallel to the wafer W, and the Z axis is set in a direction orthogonal to the wafer W.

  5-7 is a figure which shows the structure of the reflective optical system 6 concerning this Embodiment. As shown in FIGS. 5 and 6, the EUV light is incident on the first multilayer mirror 6 a constituting the reflective optical system 6 at an incident angle of 27.35 °. The first multilayer mirror 6a is a mirror of 50 layers of Mo (molybdenum) / Si (silicon) multilayers having a periodic length of 7.85 nm. Note that, in one Mo / Si layer pair, the Mo layer has a thickness of 2.75 nm, and the Si layer has a thickness of 5.10 nm. The configuration of the first multilayer mirror 6a is determined based on the wavelength and incident angle of the EUV light incident on the first multilayer mirror 6a so that the reflectance of the EUV light becomes the highest.

  Here, when the light enters the first multilayer mirror 6a at an incident angle of 27.35 °, the reflectance of the S-polarized light with respect to the first multilayer mirror 6a is 73.6%, and the reflection of the P-polarized light with respect to the first multilayer mirror 6a. The rate is 54.9%. Since the incident light (EUV light) is non-polarized light, if the amount of S-polarized light for the first multilayer mirror 6a is 50% and the amount of P-polarized light for the first multilayer mirror 6a is 50% of the amount of incident light, The amount of S-polarized light of EUV light reflected by the first multilayer mirror 6a is 50% × 0.736 (reflectance) = 36.8%, and the amount of P-polarized light is 50% × 0.549 (reflectance) = 27. .5%. The traveling direction of the EUV light incident on the first multilayer mirror 6a is a vector (1, 0, 0), and the normal direction of the first multilayer mirror 6a is a vector (−0.888, −0.325). , 0.325). The direction of S-polarized light with respect to the first multilayer mirror 6a is a vector (0, -0.707, 0.707), and the direction of P-polarized light is a vector (0, 0.707, -0.707).

  The EUV light reflected by the first multilayer mirror 6a is incident on the second multilayer mirror 6b at an incident angle of 27.35 ° as shown in FIG. The configuration of the multilayer film of the second multilayer mirror 6b is the same as the configuration of the multilayer film of the first multilayer mirror 6a. The configuration of the second multilayer mirror 6b is determined based on the wavelength and incident angle of the EUV light incident on the second multilayer mirror 6b so that the reflectance of the EUV light becomes the highest. Here, the traveling direction of the EUV light reflected by the first multilayer mirror 6a and incident on the second multilayer mirror 6b is a vector (−0.577, −0.577, 0.577), and the second multilayer The normal direction of the film mirror 6b is a vector (0.325, 0.325, -0.888). The direction of S-polarized light with respect to the second multilayer mirror 6b is a vector (0, -0.707, -0.707), and the direction of P-polarized light is a vector (-0.817, 0.408, -0.408). It is.

Accordingly, the directions of the S-polarized light and the P-polarized light with respect to the first multilayer mirror 6a do not coincide with the directions of the S-polarized light and the P-polarized light with respect to the second multilayer mirror 6b, and therefore the first multilayer reflected by the first multilayer mirror 6a. S-polarized light and P-polarized light with respect to the film mirror 6a are distributed in the directions of S-polarized light and P-polarized light with respect to the second multilayer mirror 6b, and their ratios are calculated in a state before entering the second multilayer mirror 6b. As a result of calculation,
(1) The ratio of S-polarized light reflected by the first multilayer mirror 6a to S-polarized light with respect to the second multilayer mirror 6b is 0.25.
(2) The proportion of the S-polarized light reflected by the first multilayer mirror 6a that becomes P-polarized with respect to the second multilayer mirror 6b is 0.75.
(3) Of the P-polarized light reflected by the first multilayer mirror 6a, the ratio of S-polarized light to the second multilayer mirror 6b is 0.75.
(4) Of the P-polarized light reflected by the first multilayer mirror 6a, the ratio of being P-polarized with respect to the second multilayer mirror 6b is 0.25.
It becomes.

Therefore,
The amount of light in (1) is (50% × 0.736) × 0.25 = 9.2%
The amount of light in (2) is (50% × 0.736) × 0.75 = 27.6%
The amount of light in (3) is (50% × 0.549) × 0.75 = 20.6%
The amount of light in (4) is (50% × 0.549) × 0.25 = 6.9%
Thus, the amount of S-polarized light for the second multilayer mirror 6b is (1) + (3) = 29.8%, and the amount of P-polarized light for the second multilayer mirror 6b is (2) + (4) = 34.5. %. When these lights are reflected by the second multilayer mirror 6b, the amount of S-polarized light of the reflected light is 29.8% × 0.736 = 21.9%, and the amount of P-polarized light of the reflected light is 34.5%. × 0.549 = 18.9%. Therefore, the total amount of S-polarized light and P-polarized light is 40.8%, that is, the reflective optical system 6 (the first multilayer mirror 6a and the second multilayer mirror 6b). The reflectivity of EUV light via is 40.8%. Further, the degree of polarization of the EUV light is 0.07 (S-polarized light) due to the balance of the amount of S-polarized light and P-polarized light of the EUV light via the reflective optical system 6. Further, the traveling direction of the EUV light incident on the first multilayer mirror 6a is the vector (1, 0, 0) as described above, and the traveling direction of the EUV light reflected by the second multilayer mirror 6b is the vector ( 0, 0, -1), which exist in different planes located substantially in parallel, but the traveling direction of the EUV light incident on the first multilayer mirror 6a and the EUV light reflected by the second multilayer mirror 6b The angle formed with the traveling direction is 90 °.

  According to the reflective optical system according to the second embodiment, two multilayers are compared with the reflectance of EUV light when the traveling direction of the EUV light is bent at a substantially right angle by using one multilayer mirror. Even though the film mirrors (the first multilayer film mirror and the second multilayer film mirror) are used to fold the traveling direction of the EUV light at a substantially right angle, the reflectance of the EUV light becomes high. Compared with the polarization characteristics of EUV light after folding the EUV light in a substantially right angle using one multilayer mirror, the EUV light in the substantially right angle using two multilayer mirrors. The polarization characteristic balance of the EUV light after bending is good.

  The comparative example used in the first embodiment is compared with the second embodiment. In the comparative example, the reflectance of the EUV light reflected by the multilayer mirror is 39.0% in the case of non-polarized incidence, and the degree of polarization of the EUV light is 0.86 (S-polarized light).

  On the other hand, the reflectance of EUV light reflected by the reflective optical system (two multilayer mirrors) according to the second embodiment is 40.8% as described above in the case of non-polarized incidence. The reflectance of EUV light becomes higher than when EUV light is bent at a substantially right angle by the multilayer mirror. Further, the degree of polarization of the EUV light reflected by the reflecting optical system according to the second embodiment is 0.07 (S-polarized light) as described above, and the EUV light is substantially perpendicular by one multilayer film mirror. The polarization characteristic balance of the EUV light is much better than that when bent into the shape.

  Therefore, according to the projection exposure apparatus according to the second embodiment, the EUV light is bent at a substantially right angle while maintaining a high reflectivity of the EUV light and a good balance between the S-polarized component and the P-polarized component. be able to. That is, it is possible to increase the degree of freedom in the design and configuration of the illumination optical system while suppressing the loss of the EUV light amount and the deterioration of the polarization characteristic balance, and it is possible to perform exposure with high throughput and high resolution.

  In the reflective optical system according to the second embodiment, the traveling direction of the EUV light is bent at a substantially right angle, but the traveling direction of the EUV light incident on the reflective optical system and the EUV light emitted from the reflective optical system. The angle θ formed with the light traveling direction may be in the range of 70 ° <θ <110 °. Within the range of 70 ° <θ <110 °, the polarization characteristics of the EUV light are maintained in a balanced manner as compared with the case where the traveling direction of the EUV light is bent at the same angle by one multilayer mirror.

  Further, when the angle θ formed by the traveling direction of the EUV light incident on the reflecting optical system and the traveling direction of the EUV light emitted from the reflecting optical system is within a range of 77 ° <θ <97 °, one multilayer mirror Compared to the case where the traveling direction of the EUV light is bent at the same angle, the polarization characteristics of the EUV light are not only maintained in a well-balanced manner, but also the reflectance of the EUV light is increased.

  In the projection exposure apparatus according to the above-described embodiment, EUV light having a wavelength of 13.5 nm is used as exposure light. However, EUV light having a wavelength of 1 nm to 100 nm may be used as exposure light. In this case, the type and the number of the multilayer films formed on the reflection surfaces of the first multilayer mirror and the second multilayer mirror are the same as the first multilayer in which the wavelength of the exposure light and the exposure light constitute the reflection optical system. Based on the angle of incidence on the film mirror and the second multilayer mirror, it is determined to have an optimum reflectance.

  In the above-described embodiment, the incident angles of the EUV light incident on the first multilayer mirror and the second multilayer mirror are the same, but the incident angle incident on the first multilayer mirror and the second multilayer mirror are the same. The incident angle incident on the film mirror may be different. The first multilayer mirror and the second multilayer mirror have the same multilayer configuration, but the first multilayer mirror and the second multilayer mirror are configured differently. Also good.

  In the projection exposure apparatus according to the above-described embodiment, the reflection optical system is provided in the optical path between the light source and the collector mirror, but the reflection optical system is provided in the other optical path in the illumination optical apparatus. You may do it. Further, a reflecting member having both functions of a collector mirror, a reflective fly's eye optical system, a condenser mirror and the like constituting the illumination optical device and a function of a reflecting optical system that bends EUV light at a predetermined angle may be provided. . Furthermore, the above-described reflection optical system can be used in another optical system such as a projection optical system instead of the illumination optical system.

  In the above-described embodiment, the step-and-scan type exposure apparatus has been described as an example. However, the present invention can also be applied to a step-and-repeat type exposure apparatus. In the above description, non-polarized light is used. However, EUV light other than non-polarized light can be used.

It is a figure which shows schematic structure of the projection exposure apparatus concerning 1st Embodiment. It is a figure which shows the structure of the reflective optical system concerning 1st Embodiment. It is a graph which shows the angle which the incident light and reflected light to a reflective optical system make, and the polarization degree of S polarization at that time. It is a graph which shows the angle | corner which the incident light and output light to a reflective optical system make, and the reflectance of the ultrashort ultraviolet light in that case. It is a figure which shows the structure of the reflective optical system concerning 2nd Embodiment. It is a figure which shows the structure of the reflective optical system concerning 2nd Embodiment. It is a figure which shows the structure of the reflective optical system concerning 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 2 ... Light source 4,6 ... Reflection optical system, 10 ... Collector mirror, 12, 14 ... Reflection type fly eye optical system, 16 ... Aperture stop, 18, 20 ... Condenser mirror, M ... Reflection type mask, PL ... Reflection type Projection optical system, W ... wafer.

Claims (5)

In the reflection optical system that bends the traveling direction of the ultra-short ultraviolet light to a predetermined angle
A first multilayer mirror that makes the ultrashort ultraviolet light incident at a predetermined angle;
A second multilayer mirror that makes the ultra-short ultraviolet light reflected by the first multilayer mirror incident at a predetermined angle;
An angle θ formed between the traveling direction of the ultrashort ultraviolet light incident on the first multilayer mirror and the traveling direction of the ultrashort ultraviolet light reflected by the second multilayer mirror is:
70 ° <θ <110 °
Reflective optical system characterized by being. An angle θ formed between the traveling direction of the ultrashort ultraviolet light incident on the first multilayer mirror and the traveling direction of the ultrashort ultraviolet light reflected by the second multilayer mirror is:
77 ° <θ <97 °
The reflective optical system according to claim 1, wherein:   The ultra-short ultraviolet light incident on the first multilayer mirror and the ultra-short ultraviolet light reflected by the second multilayer mirror are present in different planes positioned substantially parallel to each other. The reflective optical system according to claim 1 or 2. In the illumination optical device that illuminates the irradiated surface with the ultrashort ultraviolet light emitted from the light source,
An illumination optical apparatus comprising the reflective optical system according to any one of claims 1 to 3. In an exposure apparatus that exposes a predetermined pattern illuminated by ultrashort ultraviolet light emitted from a light source on a photosensitive substrate,
An exposure apparatus comprising the reflective optical system according to any one of claims 1 to 3.

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