JP2010087392A - Optical system, exposure apparatus, and method of manufacturing electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely prevent flare light from reaching an image formation surface. <P>SOLUTION: This optical system is provided with a flare diaphragm S3 having a plurality of shade plates 21, 22 and drive parts 21a, 22a in an optical path of the optical system between the last optical element (mirror) PM6 and a wafer W, and capable of changing the shape of an aperture SH; and the shape of the aperture SH of the flare diaphragm S3 is changed, interlocking with the number of apertures defined by an NA diaphragm of the optical system. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical system suitable for use in an exposure apparatus or the like, an exposure apparatus including the optical system, and an electronic device manufacturing method using the exposure apparatus.

  In recent years, with the miniaturization of semiconductor integrated circuits, EUV (Extreme UltraViolet) having a shorter wavelength (about 5 to 50 nm) is used instead of conventional ultraviolet rays in order to improve the resolution of an optical system limited by the diffraction limit of light. ) Exposure technology using light (extreme ultraviolet) has been developed. This is expected to enable exposure with a pattern size of about 22 to 45 nm. Since the refractive index of a substance in the wavelength region of EUV light is close to 1, a transmission-refractive optical element such as a conventional lens cannot be used, and a mirror that is a reflective optical element is used.

  An exposure apparatus that uses EUV light as exposure light (hereinafter referred to as EUV exposure apparatus) is a light source that generates EUV light, an illumination optical system that shapes the light, a reflective mask, and a circuit pattern on the mask that is reduced on the wafer. A projection optical system for projecting is provided. As the light source, a laser plasma method, a discharge plasma method, or the like is used.

  As the illumination optical system and the projection optical system, as described above, a reflection optical system in which a reflecting mirror (mirror) is combined is used. The projection optical system includes, for example, four or six EUV reflecting mirrors coated with a multilayer film. These reflecting mirrors achieve a high reflectance by the interference effect by matching the phases of reflected light at each interface of the multilayer film.

  In order to define an optimum numerical aperture (NA) according to the pattern to be exposed and transferred, a variable type NA diaphragm whose aperture diameter can be changed is provided on or near the pupil plane of the projection optical system. Yes. Further, in order to define the shape of the exposure light on the surface conjugate with the pattern surface of the mask of the illumination optical system or in the vicinity thereof, or in order to perform exposure amount control (Does Control) in the scanning type exposure apparatus, the variable type An illumination field stop is provided.

  The optical path of the exposure light needs to be evacuated in order to suppress light absorption, and the mirror group constituting the optical system is accommodated in a vacuum chamber. Such an EUV exposure apparatus is described in Patent Document 1 below, for example.

  By the way, when exposure light (EUV light) is irradiated onto a mirror or mask as an optical element constituting the optical system, the reflection surface of the optical element is finished with high accuracy, but depending on the processing accuracy. Stray light (light resulting from irregular reflection due to minute irregularities on the reflecting surface) is generated. When flare light (light that protrudes outside the original light flux of exposure light) of this stray light reaches the imaging plane, the imaging performance of the optical system deteriorates, such as the contrast of the image on the imaging plane being reduced. . If a pattern is exposed and transferred onto a wafer (photosensitive substrate) with exposure light accompanied by such flare light, a highly accurate pattern cannot be formed.

  As a technique for coping with this, the conventional flare stop is, for example, as shown in FIG. 13, the final optical element (optical element closest to the imaging surface) L2 of the optical system and the imaging surface (wafer W). It is constituted by a plate-shaped fixed diaphragm plate 110 provided in the optical path between the surface and the surface.

  The fixed diaphragm plate 110 has an opening 110a. The opening 110a is a variable NA diaphragm provided on or near the pupil plane of the optical system in order to more reliably shield flare light reaching the imaging plane. 120 corresponds to the maximum NA defined by 120, and has a shape that substantially matches the cross-sectional shape of the light beam 101 converged by the final optical element L2 at the position (height) corresponding to the fixed aperture plate 110.

  In the figure, a transmission / refraction type optical system including lenses L1 and L2 as optical elements is shown, but this is for the purpose of simplifying the explanation or illustration, and a reflection type optical system including a plurality of mirrors. The same applies to systems. In the figure, M is a mask on which a pattern to be transferred is formed.

  However, when the NA is changed to a smaller value (small NA value) by the NA stop 120, the light beam 102 converged by the final optical element L2 of the optical system is the light beam 101 in FIG. 13 as shown in FIG. Since the shape of the opening 110a of the fixed diaphragm plate 110 cannot be changed with the conventional flare stop, a gap GA is generated between the opening 110a and the light beam 102. For this reason, flare light arrives at the imaging surface via the gap GA, causing deterioration in imaging characteristics. Here, the case where the NA value is changed by the variable NA stop has been described, but the same applies when the aperture value (shape) of the variable illumination field stop provided in the illumination optical system is changed. I can say that.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an optical system with high imaging performance by more reliably suppressing the arrival of flare light on the imaging surface. It is another object of the present invention to provide an exposure apparatus provided with such an optical system and an electronic device manufacturing method using the exposure apparatus.
International Publication No. 2007/004358

  An optical system according to a first aspect of the present invention includes a plurality of multilayer mirrors that reflect extreme ultraviolet rays, and a flare stop that has an opening that allows the extreme ultraviolet rays to pass therethrough and blocks flare light of the extreme ultraviolet rays. The flare stop has a variable mechanism for changing the shape of the opening.

  The optical system according to the first aspect of the present invention further includes an NA stop that defines a numerical aperture of the optical system, and the variable mechanism changes the shape of the opening according to the numerical aperture of the NA stop. Can be. In this case, the NA aperture is a variable NA aperture, and the variable mechanism can change the shape of the aperture in conjunction with the numerical aperture of the variable NA aperture.

  The optical system according to the first aspect of the present invention further includes an illumination field stop for defining an illumination field, and the variable mechanism changes the shape of the opening according to the aperture value of the illumination field stop. Can be. In this case, the illumination field stop may be a variable illumination field stop, and the variable mechanism may change the shape of the opening in conjunction with the aperture value of the variable illumination field stop.

  An optical system according to a second aspect of the present invention includes a plurality of multilayer mirrors that reflect extreme ultraviolet rays, and a flare stop that has an opening that allows the extreme ultraviolet rays to pass therethrough and blocks flare light from the extreme ultraviolet rays. An optical system comprising a variable mechanism that changes a position of the flare stop in a direction along an optical axis of the optical system.

  In the optical system according to the second aspect of the present invention, the optical system further includes an NA stop that defines the numerical aperture of the optical system, and the variable mechanism follows the optical axis of the flare stop in accordance with the numerical aperture of the NA stop. You can change the position of the direction. In this case, the NA stop is a variable NA stop, and the variable mechanism can change the position of the flare stop along the optical axis in conjunction with the numerical aperture of the variable NA stop.

  The optical system according to the second aspect of the present invention may further include an illumination field stop that defines an illumination field, and the variable mechanism follows the optical axis of the flare stop according to an aperture value of the illumination field stop. You can change the position of the direction. In this case, the illumination field stop is a variable illumination field stop, and the variable mechanism changes the position of the flare stop along the optical axis in conjunction with the stop value of the variable illumination field stop. it can.

  In the optical system according to the first or second aspect of the present invention, the flare stop may be arranged between a mirror closest to the imaging plane of the optical system and the imaging plane among the plurality of mirrors. it can. In this case, the flare stop can be disposed in the vicinity of the imaging plane. The flare stop may be disposed in the vicinity of a mirror closest to the imaging plane.

  In the optical system according to the first or second aspect of the present invention, when the optical system has at least one intermediate imaging plane, the flare stop is set to the intermediate imaging plane among the plurality of mirrors. It can arrange | position between a pair of mirrors which pinch | interpose. In this case, the flare stop can be disposed in the vicinity of the intermediate imaging plane. The flare stop may be disposed in the vicinity of one of the pair of mirrors sandwiching the intermediate image plane.

  In the optical system according to the first or second aspect of the present invention, as the multilayer mirror, one in which a multilayer film in which at least two materials are alternately laminated is formed can be used.

  An exposure apparatus according to a third aspect of the present invention is an exposure apparatus that projects and exposes an image of a first surface onto a second surface, and includes the above-described optical system according to the present invention.

  An electronic device manufacturing method according to a fourth aspect of the present invention includes a step of exposing a substrate using the above-described exposure apparatus according to the present invention, and a step of developing the exposed substrate. To do.

  Since the optical system according to the first aspect of the present invention has the variable mechanism for changing the shape of the opening of the flare stop, for example, the change of the opening shape of the NA stop or the shape of the illumination field stop is changed. If the cross-sectional shape of the light beam that passes through the flare stop changes with this, the shape of the opening of the flare stop can be changed accordingly, so that the flare light reaches the imaging plane. Therefore, it is possible to realize an optical system that can be more reliably suppressed and has high imaging performance.

  The optical system according to the second aspect of the present invention includes the variable mechanism that changes the position of the flare stop along the optical axis of the optical system. For example, the aperture shape of the NA stop and the illumination field stop When the cross-sectional shape of the light beam passing through the flare stop changes due to the change in the aperture shape, the position of the flare stop along the optical axis can be changed accordingly. Can be more reliably suppressed, and an optical system with high imaging performance can be realized.

  Moreover, according to the exposure apparatus which concerns on the 3rd aspect of this invention, since the optical system with such a high imaging performance is provided, exposure precision can be improved.

  Furthermore, according to the method for manufacturing an electronic device according to the fourth aspect of the present invention, since such an exposure apparatus with high exposure accuracy is used, a highly integrated, high-performance and highly reliable electronic device is manufactured. Can do.

  Hereinafter, an embodiment in which the optical system of the present invention is applied to a projection optical system of a projection exposure apparatus will be described with reference to the drawings.

[Overall configuration of exposure apparatus]
FIG. 1 is a view showing an outline of the exposure apparatus of this example. The exposure apparatus of this example is an EUV exposure apparatus that uses EUV (Extreme UltraViolet) light, which is extreme ultraviolet light having a wavelength of about 5 nm to 100 nm, as exposure light.

  This exposure apparatus mounts an illumination optical system ILS that illuminates a pattern surface (mask surface) of a reflective mask M with illumination light (exposure light) IL for exposure from the light source device 1, and a mask M. A mask stage MS for positioning M, a projection optical system (imaging optical system) PL for projecting a pattern image of the mask M onto a wafer W (photosensitive substrate), and a wafer W are mounted. A wafer stage WS is provided.

  In FIG. 1, the normal direction of the mounting surface of the wafer W is the Z direction, the direction parallel to the paper surface of FIG. 1 in the plane perpendicular to the Z direction is the Y direction, and the direction perpendicular to the paper surface is the X direction. . The exposure apparatus is a scanning exposure apparatus that projects the mask pattern on the mask M onto the wafer W while scanning and moving the mask M and the wafer W in the Y direction in FIG. It is.

  The exposure apparatus of this example has a vacuum chamber 10 in which the inside is maintained in a vacuum atmosphere, and the entire optical path from the EUV light emission point to the wafer W is housed in the vacuum chamber 10. The mask stage MS is provided with an electrostatic chuck type mask holder (not shown), and the mask M is held by the mask holder. Similarly, the wafer stage WS is provided with an electrostatic chuck type wafer holder (not shown), and the wafer W is held by the wafer holder. Further, the mask stage MS and the wafer stage WS can be driven with a predetermined stroke in the Y direction by a mask stage driving unit (not shown) and a wafer stage driving unit (not shown), respectively, and the X direction, the Z direction, It is also possible to drive in the θX direction that is the rotation direction around the direction, the θY direction that is the rotation direction around the Y direction, and the θZ direction that is the rotation direction around the Z direction.

  A control unit (not shown) is arranged, and various commands are given from the control unit to each part of the exposure apparatus such as the mask stage MS and the wafer stage WS. The exposure light emitted from the light source device 1 such as a laser excitation type plasma light source or a discharge excitation type plasma light source is made into a substantially parallel light beam by the collimator mirror 2 and is incident on the illumination optical system ILS.

  The exposure light (illumination light IL) incident on the illumination optical system ILS enters the optical integrator 3. That is, the illumination light IL includes a first fly-eye mirror 3a (first uniformizing optical element) and a second fly-eye mirror 3b (second uniformizing optical element) that constitute the reflective optical integrator 3. To form a substantial surface light source having a predetermined shape on the pupil plane (illumination optical system pupil plane) of the illumination optical system ILS on (or in the vicinity of) the second fly-eye mirror 3b.

  After that, the illumination light IL is in the shape of an arc slit by the illumination field stop S1 arranged in the optical path between the fly-eye mirror 3a and the condenser mirror 4 and at a position conjugate with or near the pattern surface of the mask M. It is shaped. The illumination field stop S is not particularly limited, but in this embodiment, an opening for shaping the illumination light IL into an arc slit shape or a rectangular slit shape (in this embodiment, an arc slit shape) according to the aperture value. This is a variable illumination field stop that can be changed continuously or stepwise. The illumination light IL shaped by the illumination field stop S1 is then condensed by the condenser mirror 4 and deflected by the plane mirror 5 for bending the optical path, so that the pattern surface of the mask M is substantially converted into an arc slit illumination light IL. Illuminate uniformly.

  Illumination light IL (exposure light) reflected by the pattern surface of the mask M and incident on the projection optical system PL is reflected by the first mirror PM1, and the aperture stop S2 disposed on or near the pupil plane of the projection optical system PL. Then, the light enters the second mirror PM2. The illumination light IL (exposure light) reflected by the second mirror PM2 is reflected in the order of the third mirror PM3, the fourth mirror PM4, the fifth mirror PM5, and the sixth mirror PM6, and masks the exposure area on the wafer W. An image of the pattern is formed.

  Each of the mirrors PM1 to PM6 constituting the projection optical system PL is a reflective optical element having a multilayer film in which at least two materials are laminated on the surface of a mirror substrate made of low thermal expansion glass. As the multilayer film, a film formed by alternately stacking, for example, about 40 to 50 layers of molybdenum (Mo) and silicon (Si) having a reflection peak at a wavelength of 13.5 nm can be used. Note that the mirrors and the like constituting the illumination optical system ILS are similarly configured.

  An NA stop S2 is provided in the optical path between the second mirror PM2 and the third mirror PM3 and on or near the pupil plane of the projection optical system PL. The NA stop S2 defines an NA (Numerical Aperture) for the light beam passing through the pupil of the projection optical system PL, and the NA stop S2 of this embodiment forms a circular or elliptical opening. This is a variable NA diaphragm that includes a plurality of light shielding blades for driving and a drive unit that moves them appropriately, and whose opening diameter can be changed continuously or stepwise. In addition to the configuration including the plurality of light-shielding blades and the drive unit, the NA diaphragm S2 is replaced with a plurality of diaphragm plates each having openings having different opening shapes in the optical path. It may be configured to be arranged. In this case, each of the diaphragm plates may be replaced automatically by providing a drive unit, or may be replaced manually. Further, the configuration of the NA aperture S2 may be other configurations.

  The light emitted from the light source device 1 includes not only EUV light (extreme ultraviolet light) that contributes to exposure but also non-exposure light (OutOfBand light) that does not contribute to exposure, such as visible light, ultraviolet light, and infrared light. These non-exposure lights are also reflected by mirrors arranged at the subsequent stage, causing flare light, and especially visible light and infrared light are thermally deformed at the mirror arranged at the subsequent stage. This is not preferable. For this reason, although illustration is omitted, it is preferable to provide a filter for cutting off the non-exposure light upstream of the illumination optical system ILS. Such a filter can be provided, for example, in the optical path between the collimator mirror 2 and the first fly-eye mirror 3a.

  By providing such a filter, it is possible to reduce the amount of non-exposure light that reaches the downstream mirror, etc., and therefore it is possible to reduce the occurrence of flare light due to the non-exposure light, and to thermally deform the mirror, etc. Can also be reduced. However, in this embodiment, since a flare stop to be described later is provided, even when such a filter is not provided, flare light caused by EUV light, including flare light caused by non-exposure light, The light can be reliably shielded.

  Note that the term “extreme ultraviolet” used in the claims and the specification of the present application refers to visible light, ultraviolet light, infrared light, etc. incidentally generated due to the performance of the light source as described above. There are cases where extreme ultraviolet rays in a strict sense that do not include the above-mentioned light are mentioned, and extreme ultraviolet rays including light such as visible light, ultraviolet light, and infrared light.

  In the optical path between the sixth mirror PM6 as the final optical element of the projection optical system PL and the wafer W, a flare stop S3 or S5 is provided. The flare stop S3 or S5 has a different purpose from the illumination field stop S1 that defines the field shape and the NA stop S2 that defines the NA, and is reflected by the upstream mirrors (3 to 5, PM1 to PM6) and the mask M. This is an apparatus for preventing or suppressing flare light generated by irregular reflection on the surface from reaching the imaging surface (the surface of the wafer W). Hereinafter, the flare stop S3 as the first embodiment and the flare stop S5 as the second embodiment will be described in detail.

[First Embodiment]
2 to 4 are diagrams for explaining the configuration of the flare stop S3 according to the first embodiment of the present invention.

  The flare stop S3 is provided in the optical path between the sixth mirror PM6 and the wafer W. The position of the flare stop S3 in the Z direction may be any position in the optical path between the sixth mirror PM6 and the wafer W, and may be in the vicinity of the imaging plane (the surface of the wafer W) or in the vicinity of the mirror PM6. However, these intermediate positions may be used. From the viewpoint of removing flare light, it is desirable to be as close as possible to the image plane, but there are auto-focus systems (not shown) and optical paths of alignment sensors (not shown) near the image plane. Alternatively, the mirror PM5 or the like may be present depending on the design of the optical system. In this embodiment, the mirror PM5 or the like is not interfered with or influenced by the mirror PM5, and the position is as close as possible to the image plane (FIGS. 2 and 3 is set to the position indicated by the symbol Z1. However, if there is no such circumstance, it is preferable to locate it near the image plane.

  The flare stop S3 defines four openings for light shielding plates 21 to 24 (in FIG. 2 and FIG. 3, the light shielding plate 21 and the light shielding plate), respectively, so as to define openings through which light other than flare light is transmitted. 22 are displayed only). The light shielding plates 21 to 24 are set so that their plate surfaces are substantially parallel to the XY plane. The material of the light shielding plates 21 to 24 is preferably a metal having high thermal conductivity, and for example, stainless steel can be used. The material of the light shielding plates 21 to 24 may be a material that blocks only exposure light, and may be a material that transmits alignment light used for alignment, autofocus light used for autofocus, and the like. Glass such as can be used.

  The light shielding plate 21 is slidably driven along the Y direction by the drive unit 21a and is slidably driven at an arbitrary position in the Y direction. The light shielding plate 22 is slidably driven along the Y direction by the drive unit 22a, and is slidably driven at an arbitrary position in the Y direction. The light shielding plate 23 is slidably driven by the drive unit 23a so as to be slidable (advancing and retreating) along the X direction, and is slidably driven at an arbitrary position in the X direction. The light shielding plate 24 is slidably driven along the X direction by the drive unit 24a, and is slidably driven at an arbitrary position in the X direction.

  As each drive part 21a, 22a, 23a, 24a, a piezo actuator provided with a piezo element, a displacement magnifying mechanism, etc., a linear motor, or what consists of a stepping motor and a rack and pinion, etc. can be used. Moreover, each drive part 21a, 22a, 23a, 24a is provided with the position detection sensor for detecting each position of each light shielding plate 21-24, and it can position each light shielding plate 21-24 with high precision. It has become.

  In this embodiment, the inner sides 21b and 22b of the light shielding plate 21 and the light shielding plate 22 facing each other are arcuate, and the inner sides 23b and 24b of the light shielding plate 23 and the light shielding plate 24 facing each other are linear. It has become. Since the shape of the illumination area defined by the illumination field stop S1 of the illumination optical system ILS (that is, the shape of the exposure light on the surface of the wafer W) is an arc slit shape in this embodiment, these sides 21b, 22b, 23b , 24b can define a shape substantially similar to the shape of the arc slit-shaped illumination area. In addition, when the shape of the said illumination area | region is a rectangular slit shape, as FIG. 5 shows, the edge | sides 21b and 22b which the light-shielding plate 21 and the light-shielding plate 22 mutually correspond are formed in linear form. That is, the inner sides 21b, 22b, 23b, and 24b of each of the light shielding plates 21 to 24 are formed so as to define a shape that is substantially similar to the opening shape of the illumination field stop S1.

  In this embodiment, the flare stop S3 is provided with a cooling mechanism (not shown) including a Peltier element or the like. Since the inside of the optical system of the EUV exposure apparatus is evacuated, the flare stop S3 is disposed in an environment close to a heat insulation state. For this reason, when a part of the EUV light is irradiated to the flare stop S3, the temperature easily rises and thermal deformation is assumed to occur. However, cooling with this cooling mechanism suppresses the temperature increase of the flare stop S3. it can. As the cooling mechanism, a type of circulating refrigerant may be used.

  In a state where the NA stop S2 in FIG. 1 is set to the maximum NA, for example, as shown in FIG. 2, the light beam IL1 converged by the mirror PM6 as the final optical element of the projection optical system PL with respect to the principal ray ILM The maximum angle θ1 is relatively large. For this reason, the light shielding plate 21, the light shielding plate 22, the light shielding plate 23, and the light shielding plate 24 of the flare stop S3 are driven in directions away from each other by driving units 21a, 22a, 23a, 24a that drive them. The inner sides 21b, 22b, 23b, and 24b are widened so as to substantially match the shape of the cross section parallel to the XY plane at the position indicated by the reference symbol Z1 of the light beam IL1 converged by the mirror PM6 of the flare stop S3. Positioned in the state.

  Therefore, when the NA stop S2 is set to the maximum NA, flare light generated in front of the flare stop S3 is blocked by the respective light shielding plates 21 to 24, and the imaging plane (the surface of the wafer W). The flare light reaching to can be suppressed to a minimum.

  On the other hand, in the state in which the NA stop S2 in FIG. 1 is set to the minimum NA, for example, as shown in FIG. 3, the principal ray of the light beam IL2 converged by the mirror PM6 as the final optical element of the projection optical system PL. The maximum angle θ2 with respect to the ILM is smaller than θ1. For this reason, the light shielding plate 21, the light shielding plate 22, the light shielding plate 23, and the light shielding plate 24 of the flare stop S3 are driven in directions close to each other by the drive units 21a, 22a, 23a, 24a that drive them. The inner sides 21b, 22b, 23b, and 24b are positioned at narrowed positions so as to substantially match the cross-sectional shape parallel to the XY plane at the position Z1 of the light beam IL2 converged by the mirror PM6 of the flare stop S3. Is done. Accordingly, even when the NA aperture is set to the minimum NA, flare light existing in front of the flare aperture S3 is shielded by the respective light shielding plates 21 to 24, and the imaging plane (the surface of the wafer W). The flare light that reaches can be minimized.

  Here, the case where the NA is set to the maximum NA and the case where the NA is set to the minimum NA has been described. However, even if the NA is set to any intermediate NA between the maximum NA and the minimum NA, Corresponding to (interlocking) with this, it is the same that the shape of the opening SH is changed, and therefore detailed description thereof is omitted.

  As described above, when the NA is changed by the NA stop S2, the light shielding plates 21 to 24 of the flare stop S3 are driven by the drive units 21a, 22a, It is made to slide appropriately through 23a, 24a. Thereby, even if the shape of the light beams IL1 and IL2 converged by the mirror PM6 changes due to the change of NA, the flare light can always be shielded in an optimum state. Therefore, highly accurate exposure is possible.

  Note that the shape of the light beam converged by the mirror PM6 also changes depending on the change of the aperture value of the illumination field stop S1, that is, the change of the aperture shape, but this may be handled in the same manner as in the case of changing the NA. Detailed description thereof will be omitted. When both the NA value by the NA stop S2 and the stop value by the illumination field stop S1 are changed, the flare stop is changed according to the change in the shape of the light beam converged by the mirror PM6 due to the change of both. What is necessary is just to operate S3.

  In the above-described embodiment, the flare stop S3 having the four light shielding plates 21 to 24 and the drive units 21a, 22a, 23a, and 24a according to the NA value by the NA stop S2 and / or the stop value by the illumination field stop S1. The aperture shape is automatically changed. However, the NA aperture S2 is provided with a plurality of light-shielding plates each having an opening having a different aperture shape, and an exchange mechanism if necessary. You may comprise so that it can replace | exchange manually or automatically according to the change of the aperture value by NA value and / or illumination field stop S1.

  In the above-described embodiment, the flare stop S3 is disposed in the optical path between the mirror PM6 and the wafer W. However, when the intermediate imaging plane is present in the optical path of the projection optical system PL, the flare stop S3. Instead of or in addition to this, a flare stop having the same configuration as the flare stop S3 can be provided in the optical path between the mirrors having the intermediate imaging plane. For example, as shown in FIG. 1, when there is an intermediate imaging plane IP between the mirror PM4 and the mirror PM5, a flare stop S4 can be provided in the optical path between the mirror PM4 and the mirror PM5. . In this case, the position where the flare stop S4 is provided may be in the vicinity of the mirror PM4, in the vicinity of the mirror PM5, or between these positions, but in the vicinity of the intermediate imaging plane IP. preferable.

  Further, when there are a plurality of such intermediate image formation surfaces in the projection optical system PL, flare stops having the same configuration as the flare stop S3 are provided on two or more of the plurality of intermediate image formation surfaces, respectively. Also good. Here, the case where the flare stop is provided in the projection optical system PL has been described. However, when there is an intermediate image formation surface in the illumination optical system ILS, the same as the flare stop S3 in the vicinity of the intermediate image formation surface. A flare stop having the following structure may be provided.

  By providing a plurality of flare stops in the optical system, it is possible to more effectively suppress the arrival of flare light on the imaging plane (the surface of the wafer W).

[Second Embodiment]
FIGS. 6-8 is a figure for demonstrating the structure of the flare stop S5 which concerns on 2nd Embodiment of this invention.

  The flare stop S5 is provided in the optical path between the sixth mirror PM6 and the wafer W. The position of the flare stop S5 in the Z direction may be any position in the optical path between the sixth mirror PM6 and the wafer W, and may be in the vicinity of the imaging plane (the surface of the wafer W) or in the vicinity of the mirror PM6. However, these intermediate positions may be used. From the viewpoint of removing flare light, it is desirable to be as close to the image plane as possible, but there is an autofocus system (not shown) and an optical path of an alignment sensor near the image plane, or an optical system. In this embodiment, the mirror PM5 or the like may be present depending on the design of the lens. In this embodiment, the mirror PM5 or the like does not interfere with or influence the mirror PM5. To the position indicated by Z3). However, if there is no such circumstance, it is preferable to locate it near the image plane. Since the flare stop S5 of the second embodiment is slid in the Z direction as will be described later, the position in the Z direction is set in consideration of the stroke.

  The flare stop S5 includes a light shielding plate 31 made of a single thin plate. The light shielding plate 31 has an opening for transmitting light other than flare light, and the plate surface is set to a surface substantially parallel to the XY plane. The material of the light shielding plate 31 is preferably a metal having high thermal conductivity, and for example, stainless steel can be used. Further, the material of the light shielding plate 31 may be a material that blocks only exposure light, and may be a material that transmits alignment light used for alignment, autofocus light used for autofocus, and the like, such as quartz. Glass can be used.

  The light shielding plate 31 is slidably driven along the Z direction by the driving unit 31a and is slidably driven at an arbitrary position in the Z direction.

  As the drive unit 31a, a piezo actuator having a piezo element and a displacement magnifying mechanism, a linear motor, a stepping motor, and a rack and pinion can be used. Further, the drive unit 31a includes a position detection sensor for detecting the position of the light shielding plate 31 in the Z direction, and can position the light shielding plate 31 at an arbitrary position in the Z direction with high accuracy.

  In this embodiment, the opening SH formed in the light shielding plate 31 has a shape of the illumination area defined by the illumination field stop S1 of the illumination optical system ILS (that is, as best shown in FIG. 8). In this embodiment, the shape of the exposure light on the surface of the wafer W is an arc slit shape, so that it is formed so as to define a shape substantially similar to the shape of the illumination area of the arc slit shape. In addition, when the shape of the said illumination area | region is a rectangular slit shape, the opening of the light-shielding plate 31 is formed in the rectangle corresponding to this.

  In this embodiment, the flare stop S5 is provided with a cooling mechanism (not shown) including a Peltier element or the like. Since the inside of the optical system of the EUV exposure apparatus is evacuated, the flare stop S5 is disposed in an environment close to a heat insulation state. For this reason, when a part of the EUV light is irradiated to the flare stop S5, the temperature easily rises and thermal deformation is assumed to occur. However, by cooling with this cooling mechanism, the temperature increase of the flare stop S5 can be suppressed. As the cooling mechanism, a type of circulating refrigerant may be used.

  In a state in which the NA stop S2 in FIG. 1 is set to the maximum NA, for example, as shown in FIG. 6, the light beam IL1 converged by the mirror PM6 as the final optical element of the projection optical system PL with respect to the principal ray ILM The maximum angle θ1 is relatively large. For this reason, the light shielding plate 31 of the flare stop S5 is indicated by the symbol Z2 such that the opening SH substantially matches the shape of the cross section parallel to the XY plane of the light beam IL1 converged by the mirror PM6 of the flare stop S5. Is positioned.

  As described above, the light shielding plate 31 of the flare stop S5 has an opening SH substantially in the shape of a cross section parallel to the XY plane at the position Z1 in the Z direction of the light beam IL1 converged by the mirror PM6 of the flare stop S5. It is positioned at the matching position. Accordingly, when the NA stop S2 is set to the maximum NA, flare light generated in front of the flare stop S5 is blocked by the light blocking plate 31 and reaches the imaging plane (the surface of the wafer W). Flare light can be minimized.

  On the other hand, in the state where the NA stop S2 in FIG. 1 is set to the minimum NA, for example, as shown in FIG. 7, the principal ray of the light beam IL2 converged by the mirror PM6 as the final optical element of the projection optical system PL. The maximum angle θ2 with respect to the ILM is smaller than θ1. Therefore, the driving unit 31a of the flare stop S5 is operated to move the light shielding plate 31 in the + Z direction, and the opening SH is parallel to the XY plane of the light beam IL2 converged by the mirror PM6 of the flare stop S5. The light shielding plate S5 is positioned at a position Z3 where the light shielding plate S5 is raised so as to substantially match the shape of a simple cross section. Therefore, even when the NA aperture is set to the minimum NA, the flare light existing in front of the flare aperture S5 is blocked by the light blocking plate 31 and reaches the imaging plane (the surface of the wafer W). Flare light can be minimized.

  Here, the case where the NA is set to the maximum NA and the case where the NA is set to the minimum NA has been described. However, even if the NA is set to any intermediate NA between the maximum NA and the minimum NA, Similarly, this can be dealt with by adjusting the position of the light shielding plate 31 in the Z direction.

  As described above, when the NA is changed by the NA stop S2, the light shielding plate 31 of the flare stop S5 is appropriately Zed via the driving unit 31a for driving the flare stop S5 in conjunction with the change of the NA value. It is made to slide in the direction. Thereby, even if the shape of the light beams IL1 and IL2 converged by the mirror PM6 changes due to the change of NA, the flare light can always be shielded in an optimum state. Therefore, highly accurate exposure is possible.

  Note that the shape of the light beam converged by the mirror PM6 also changes depending on the change of the aperture value of the illumination field stop S1, that is, the change of the aperture shape, but this may be handled in the same manner as in the case of changing the NA. Detailed description thereof will be omitted. When both the NA value by the NA stop S2 and the stop value by the illumination field stop S1 are changed, the flare stop is changed according to the change in the shape of the light beam converged by the mirror PM6 due to the change of both. What is necessary is just to operate S5.

  In the above-described embodiment, according to the NA value by the NA aperture S2 and / or the aperture value by the illumination field stop S1, the flare stop S5 having the single light shielding plate 31 and the drive unit 31a is positioned in the Z direction ( The height is automatically changed, but the drive unit may be omitted, and the position of the light shielding plate 31 in the Z direction may be manually adjusted.

  In the above-described embodiment, the flare stop S5 is disposed in the optical path between the mirror PM6 and the wafer W. However, when the intermediate imaging plane is present in the optical path of the projection optical system PL, the flare stop S5. Instead of or in addition to this, a flare stop having the same configuration as the flare stop S5 or the flare stop S3 according to the first embodiment described above is provided in the optical path between the mirrors having the intermediate imaging plane. Can do. For example, as shown in FIG. 1, when there is an intermediate imaging plane IP between the mirror PM4 and the mirror PM5, a flare stop S4 can be provided in the optical path between the mirror PM4 and the mirror PM5. . In this case, the position where the flare stop S4 is provided may be in the vicinity of the mirror PM4, in the vicinity of the mirror PM5, or between these positions, but in the vicinity of the intermediate imaging plane IP. preferable.

  In addition, when there are a plurality of such intermediate image formation surfaces in the projection optical system PL, the flare stop S5 or the flare according to the first embodiment described above is provided in each of two or more of the plurality of intermediate image formation surfaces. A flare stop having the same configuration as that of the stop S3 may be provided. Here, the case where the flare stop is provided in the projection optical system PL has been described. However, when there is an intermediate image formation surface in the illumination optical system ILS, the flare stop S3 or the above-mentioned is located near the intermediate image formation surface. A flare stop having the same configuration as the flare stop S3 according to the first embodiment may be provided.

  By providing a plurality of flare stops, it is possible to more effectively suppress the arrival of flare light on the imaging plane (the surface of the wafer W).

[Others]
In the first embodiment described above, the shape of the inner surface (the inner surface related to the inner sides 21b, 22b, 23b, 24b) of the openings SH of the four light shielding plates 21 to 24 constituting the flare stop S3 is as shown in FIG. As shown in FIG. 3, it is a plane substantially orthogonal to the plate surface. The shape of the inner surface may be a slope whose width increases from the upper surface to the lower surface, as shown in FIG. Further, as shown in FIG. 10, it may be a slope whose width increases from the lower surface toward the upper surface. Furthermore, as shown in FIG. 11, a substantially V-shaped surface may be used in which the width decreases from the upper surface toward the intermediate portion and the width increases from the intermediate portion toward the lower surface. The one shown in FIG. 9 or 10 may be selected in accordance with the convergence or divergence direction of the light beam to be defined after appropriately setting the inclination angle of the slope. The thing shown in FIG. 11 can be used suitably at the point which can be used irrespective of the convergence or the divergence direction of the light beam to prescribe | regulate.

  In the second embodiment described above, the shape of the inner surface (inner end surface) of the opening SH of the single light shielding plate 31 constituting the flare stop S5 is the same as that described above.

  The projection optical system PL in the above-described embodiment is not limited to the optical system constituted by the above-described six aspherical mirrors PM1 to PM6, but may include other mirrors such as eight mirrors and ten mirrors. A reflection optical system including a number of mirrors can also be used.

  In addition, a mirror (for example, each mirror of the collimator mirror 2, the illumination optical system ILS, and the projection optical system PL) used in the exposure apparatus according to the present embodiment has a multilayer film formed on the reflection surface in order to reflect EUV light. However, this multilayer film may be composed of a Mo / Be multilayer film or the like in addition to the Mo / Si multilayer film. Furthermore, the peak wavelength of EUV light (exposure light) emitted from the light source device 1 of the present embodiment is not limited to 13.5 nm, and may be 11.8 nm.

  In the above description, the semiconductor wafer W is assumed as the substrate to be exposed. However, the substrate to be exposed is not only a semiconductor wafer for manufacturing a semiconductor device, but also a glass substrate for a display device and a thin film magnetic head. Or a mask or reticle original (synthetic quartz, silicon wafer) used in an exposure apparatus, or a film member. Further, the shape of the substrate is not limited to a circle, and may be other shapes such as a rectangle.

  Furthermore, the form of the exposure apparatus to which the optical system of the present embodiment is applied is a step-and-scan type scanning exposure apparatus that scans and exposes the pattern of the mask M by synchronously moving the mask M and the wafer W described above ( A step-and-repeat projection exposure apparatus (stepper) that collectively exposes the pattern of the mask M while the mask M and the wafer W are stationary and sequentially moves the wafer W stepwise. Also good.

  The scanning exposure apparatus of the present embodiment described above assembles various subsystems including the constituent elements recited in the claims of the present application so as to maintain predetermined mechanical accuracy, electrical accuracy, and optical accuracy. It is manufactured by. In order to ensure these various accuracies, before and after assembly, various optical systems are adjusted to achieve optical accuracy, various mechanical systems are adjusted to achieve mechanical accuracy, and various electrical systems are Adjustments are made to achieve electrical accuracy. The assembly process from the various subsystems to the exposure apparatus includes mechanical connection, electrical circuit wiring connection, pneumatic circuit piping connection and the like between the various subsystems. Needless to say, there is an assembly process for each subsystem before the assembly process from the various subsystems to the exposure apparatus. When the assembly process of the various subsystems to the exposure apparatus is completed, comprehensive adjustment is performed to ensure various accuracies as the entire exposure apparatus. The exposure apparatus is preferably manufactured in a clean room where the temperature, cleanliness, etc. are controlled.

  Next, an electronic device manufacturing method using the exposure apparatus according to this embodiment will be described. When an electronic device (microdevice) such as a semiconductor device is manufactured using the exposure apparatus according to the above-described embodiment, the electronic device has a function / performance design step ST111 as shown in FIG. Step ST112 for producing a mask (reticle) based on ST111, Step ST113 for producing a substrate (wafer) as a base material of the device, a step of exposing and transferring a mask pattern to the substrate by the exposure apparatus of the above-described embodiment, exposure Development step of the developed substrate, substrate processing step ST114 including heating (curing) and etching step of the developed substrate, device assembly step (including processing processes such as dicing step, bonding step, packaging step) ST115, and inspection Step ST116 etc. It is produced through. In other words, this device manufacturing method includes a lithography process, and the photosensitive substrate is exposed using the exposure apparatus of the above-described embodiment in the lithography process.

  In the present invention, all the above-described constituent elements can be used in appropriate combination, and some constituent elements may not be used. The embodiment described above is described for facilitating understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

It is a front view which shows schematic structure of the EUV exposure apparatus in embodiment of this invention. It is a front view which shows the principal part of the projection optical system in 1st Embodiment of this invention. It is a front view which shows the principal part of the projection optical system in 1st Embodiment of this invention. It is a top view which shows the structure of the flare stop in 1st Embodiment of this invention. It is a top view which shows the structure of the other flare stop in 1st Embodiment of this invention. It is a front view which shows the principal part of the projection optical system in 2nd Embodiment of this invention. It is a front view which shows the principal part of the projection optical system in 2nd Embodiment of this invention. It is a top view which shows the structure of the flare stop in 2nd Embodiment of this invention. It is sectional drawing which shows the structure of the inner surface of the opening part of the flare stop in 1st or 2nd embodiment of this invention. It is sectional drawing which shows the other structure of the inner surface of the opening part of the flare stop in 1st or 2nd embodiment of this invention. It is sectional drawing which shows the further another structure of the inner surface of the opening part of the flare stop in 1st or 2nd embodiment of this invention. It is a figure which shows the outline | summary of the manufacturing method of the electronic device in embodiment of this invention. It is a side view for demonstrating the problem of the optical system of a prior art. It is a side view for demonstrating the problem of the optical system of a prior art.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Light source device, ILS ... Illumination optical system, PL ... Projection optical system, PM1-PM6 ... Mirror, M ... Mask, W ... Wafer, S1 ... Illumination field stop, S2 ... NA stop, S3, S4, S5 ... Flare stop 21, 22, 23, 24, 31... Shading plate, SH... Opening, 21 a, 22 a, 23 a, 24 a, 31 a... Drive unit, Z 1, Z 2, Z 3.

Claims (19)

Multiple multilayer mirrors that reflect extreme ultraviolet radiation,
An optical system having an opening that allows the extreme ultraviolet light to pass through, and a flare stop that blocks the flare light of the extreme ultraviolet light,
The optical system characterized in that the flare stop has a variable mechanism for changing the shape of the opening. An NA aperture that defines the numerical aperture of the optical system;
The optical system according to claim 1, wherein the variable mechanism changes a shape of the opening according to a numerical aperture of the NA diaphragm. The NA aperture is a variable NA aperture,
The optical system according to claim 2, wherein the variable mechanism changes the shape of the opening in conjunction with the numerical aperture of the variable NA diaphragm. An illumination field stop for defining the illumination field;
The optical system according to claim 1, wherein the variable mechanism changes a shape of the opening according to an aperture value of the illumination field stop. The illumination field stop is a variable illumination field stop,
The optical system according to claim 4, wherein the variable mechanism changes the shape of the opening in conjunction with the aperture value of the variable illumination field stop. Multiple multilayer mirrors that reflect extreme ultraviolet radiation,
An optical system having an opening that allows the extreme ultraviolet light to pass through, and a flare stop that blocks the flare light of the extreme ultraviolet light,
An optical system comprising: a variable mechanism that changes a position of the flare stop in a direction along the optical axis of the optical system. An NA aperture that defines the numerical aperture of the optical system;
The optical system according to claim 6, wherein the variable mechanism changes a position of the flare stop along the optical axis according to the numerical aperture of the NA stop. The NA aperture is a variable NA aperture,
The optical system according to claim 7, wherein the variable mechanism changes a position of the flare stop along the optical axis in conjunction with a numerical aperture of the variable NA stop. An illumination field stop for defining the illumination field;
The optical system according to claim 6, wherein the variable mechanism changes a position of the flare stop along the optical axis in accordance with a stop value of the illumination field stop. The illumination field stop is a variable illumination field stop,
The optical system according to claim 9, wherein the variable mechanism changes a position of the flare stop in the direction along the optical axis in conjunction with a stop value of the variable illumination field stop.   The flare stop is disposed between a mirror closest to the imaging plane of the optical system and the imaging plane among the plurality of mirrors. Optical system.   The optical system according to claim 11, wherein the flare stop is disposed in the vicinity of the imaging plane.   The optical system according to claim 11, wherein the flare stop is disposed in the vicinity of a mirror closest to the imaging plane. The optical system has at least one intermediate imaging plane;
The optical system according to claim 1, wherein the flare stop is disposed between a pair of mirrors that sandwich the intermediate imaging plane among the plurality of mirrors.   The optical system according to claim 14, wherein the flare stop is disposed in the vicinity of the intermediate imaging plane.   The optical system according to claim 14, wherein the flare stop is disposed in the vicinity of one of a pair of mirrors sandwiching the intermediate imaging plane.   The optical system according to claim 1, wherein the multilayer mirror is formed with a multilayer film in which at least two materials are alternately stacked. An exposure apparatus that projects and exposes an image of a first surface onto a second surface,
An exposure apparatus comprising the optical system according to claim 1. A step of exposing a substrate using the exposure apparatus according to claim 18;
And a step of developing the exposed substrate.

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