JP5531518B2 - Polarization conversion unit, illumination optical system, exposure apparatus, and device manufacturing method - Google Patents

Description

  The present invention relates to a polarization conversion unit, an illumination optical system, an exposure apparatus, and a device manufacturing method. More specifically, the present invention relates to an illumination optical system suitable for an exposure apparatus for manufacturing devices such as a semiconductor element, an image sensor, a liquid crystal display element, and a thin film magnetic head in a lithography process.

  In a typical exposure apparatus of this type, a light beam emitted from a light source is passed through a fly-eye lens as an optical integrator, and a secondary light source (generally an illumination pupil) as a substantial surface light source composed of a number of light sources. A predetermined light intensity distribution). Hereinafter, the light intensity distribution in the illumination pupil is referred to as “pupil intensity distribution”. The illumination pupil is a position where the illumination surface becomes the Fourier transform plane of the illumination pupil by the action of the optical system between the illumination pupil and the illumination surface (a mask or a wafer in the case of an exposure apparatus). Defined.

  The light beam from the secondary light source is condensed by the condenser optical system and then illuminates the mask on which a predetermined pattern is formed in a superimposed manner. The light transmitted through the mask forms an image on the wafer via the projection optical system, and the mask pattern is projected and exposed (transferred) onto the wafer. The pattern formed on the mask is highly integrated, and it is indispensable to obtain a uniform illumination distribution on the wafer in order to accurately transfer the fine pattern onto the wafer.

  In recent years, in order to realize an illumination condition suitable for faithfully transferring a fine pattern in an arbitrary direction, an annular secondary light source is formed on the rear focal plane of the fly-eye lens or in the vicinity of the illumination pupil. A technique has been proposed in which a light beam passing through a ring-shaped secondary light source is set so as to be in a linear polarization state whose polarization direction is the circumferential direction (hereinafter referred to as “circumferential polarization state” for short) (for example, (See Patent Document 1).

Japanese Patent No. 3246615

  In the illumination optical system described in Patent Document 1, the circumferential direction of so-called relatively low continuity is set by setting the polarization state of a light beam passing through each of the arc-shaped divided regions divided into four to eight in the circumferential direction. A polarization state is realized. However, in order to satisfactorily exert the effect of circumferentially polarized light, it is desired to realize a continuous circumferentially polarized state.

  The present invention has been made in view of the above-described problems, and provides a polarization conversion unit that is arranged in, for example, the optical path of an illumination optical system and can realize a pupil intensity distribution in a continuous circumferential polarization state. The purpose is to do. The present invention also provides an illumination optical system capable of illuminating an irradiated surface with light in a desired circumferential polarization state using a polarization conversion unit that realizes a pupil intensity distribution in a continuous circumferential polarization state. The purpose is to do. In addition, the present invention can accurately transfer a fine pattern onto a photosensitive substrate under an appropriate illumination condition using an illumination optical system that illuminates a predetermined pattern with light having a desired circumferential polarization state. An object of the present invention is to provide an exposure apparatus and a device manufacturing method.

In order to solve the above problems, in the first embodiment of the present invention, in the polarization conversion unit that converts the incident light into light having a predetermined polarization state and emits the light,
A polarization conversion member that is formed of an optical material having optical rotation and has a form in which the thickness continuously changes along the circumferential direction of a circle centered on the optical axis, and changes the polarization state of incident light;
Provided is a polarization conversion unit comprising a correction member that is disposed on the incident side or the emission side of the polarization conversion member and compensates the light deflection action of the polarization conversion member.

In the second embodiment of the present invention, in the illumination optical system that illuminates the illuminated surface with the light from the light source,
Provided is an illumination optical system comprising a first type of polarization conversion unit disposed in an optical path between the light source and the irradiated surface.

  According to a third aspect of the present invention, there is provided an exposure apparatus comprising the illumination optical system according to the second aspect for illuminating a predetermined pattern, and exposing the predetermined pattern onto a photosensitive substrate.

In the fourth embodiment of the present invention, using the exposure apparatus of the third embodiment, an exposure step of exposing the predetermined pattern to the photosensitive substrate;
Developing the photosensitive substrate to which the predetermined pattern is transferred, and forming a mask layer having a shape corresponding to the predetermined pattern on the surface of the photosensitive substrate;
And a processing step of processing the surface of the photosensitive substrate through the mask layer.

  In the polarization conversion unit of the present invention, by the optical rotation action of the polarization conversion member formed by an optical material having optical rotation and having a form in which the thickness continuously changes along the circumferential direction of the circle centering on the optical axis, Immediately thereafter, a continuous light intensity distribution in the circumferential polarization state is formed. The light deflection action by the polarization conversion member is compensated by the action of the correction member arranged on the incident side or the emission side. Thus, when the polarization conversion unit of the present invention is applied to an illumination optical system, a continuous pupil intensity distribution in the circumferential polarization state is formed on the illumination pupil of the illumination optical system.

  That is, in the polarization conversion unit of the present invention, for example, it is arranged in the optical path of the illumination optical system, so that it is possible to realize a pupil intensity distribution in a continuous circumferential polarization state. In the illumination optical system of the present invention, the irradiated surface can be illuminated with light in a desired circumferential polarization state using a polarization conversion unit that realizes a pupil intensity distribution in a continuous circumferential polarization state. In the exposure apparatus of the present invention, a fine pattern is formed on a photosensitive substrate under appropriate illumination conditions using an illumination optical system that illuminates a pattern surface as an irradiated surface with light having a desired circumferential polarization state. The transfer can be performed accurately, and a good device can be manufactured.

It is a figure which shows schematically the structure of the exposure apparatus concerning embodiment of this invention. It is a figure which shows the annular | circular shaped pupil intensity distribution formed in the illumination pupil immediately after a micro fly's eye lens. It is a figure which shows roughly the cross-sectional structure along YZ plane of a polarization conversion unit. It is a perspective view which shows roughly the characteristic surface shape of the polarization conversion member in a polarization conversion unit. It is a figure explaining the optical rotatory power of quartz. It is a figure which shows annular | circular shaped light intensity distribution in the continuous circumferential direction polarization | polarized-light state formed by the effect | action of a polarization conversion unit. It is a figure which shows a ring-shaped light intensity distribution in the continuous radial direction polarization | polarized-light state formed by the effect | action of a polarization conversion unit. It is a flowchart which shows the manufacturing process of a semiconductor device. It is a flowchart which shows the manufacturing process of liquid crystal devices, such as a liquid crystal display element.

  Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a drawing schematically showing a configuration of an exposure apparatus according to an embodiment of the present invention. In FIG. 1, the Z axis along the normal direction of the transfer surface (exposure surface) of the wafer W, which is a photosensitive substrate, and the Y axis in the direction parallel to the paper surface of FIG. In the W transfer surface, the X axis is set in a direction perpendicular to the paper surface of FIG. Referring to FIG. 1, in the exposure apparatus of the present embodiment, exposure light (illumination light) is supplied from a light source 1.

  As the light source 1, for example, a KrF excimer laser light source that supplies light with a wavelength of 248 nm, an ArF excimer laser light source that supplies light with a wavelength of 193 nm, or the like can be used. A substantially parallel light beam emitted from the light source 1 along the Z direction has, for example, a rectangular cross section extending along the X direction, and is incident on a beam expander 2 including a pair of lenses 2a and 2b. The light beam incident on the beam expander 2 is enlarged in the plane of FIG. 1 and shaped into a light beam having a predetermined rectangular cross section.

  A substantially parallel light beam via a beam expander 2 as a shaping optical system is deflected in the Y direction by a mirror 3 and then an afocal lens via a polarization state switching unit 4 and a diffractive optical element 5 for annular illumination. 6 is incident. The polarization state switching unit 4 is a quarter-wave plate 4a that sequentially converts the incident elliptically polarized light into linearly polarized light with the crystal optical axis being rotatable about the optical axis AX in order from the light incident side. And a half-wave plate 4b that changes the polarization direction of the linearly polarized light that is incident on the optical axis AX so that the crystal optical axis is rotatable, and a depolarizer that can be inserted into and removed from the illumination optical path (depolarized) Element) 4c.

  The polarization state switching unit 4 has a function of converting light from the light source 1 into linearly polarized light having a desired polarization direction and making it incident on the diffractive optical element 5 with the depolarizer 4c retracted from the illumination optical path. The polarization state switching unit 4 has a function of converting light from the light source 1 into substantially non-polarized light and making it incident on the diffractive optical element 5 in a state where the depolarizer 4c is set in the illumination optical path. The afocal lens 6 includes a front lens group 6a and a rear lens group 6b. The front focal position of the front lens group 6a substantially coincides with the position of the diffractive optical element 5, and the rear focal point of the rear lens group 6b. This is an afocal system (non-focal optical system) set so that the position and the position of the predetermined plane IP indicated by the broken line in the figure substantially coincide.

  In general, a diffractive optical element is formed by forming a step having a pitch of the wavelength of exposure light (illumination light) on a substrate, and has a function of diffracting an incident beam to a desired angle. Specifically, the diffractive optical element 5 for annular illumination has a function of forming an annular light intensity distribution in the far field (or Fraunhofer diffraction region) when a parallel light beam having a rectangular cross section is incident. Have Therefore, the substantially parallel light beam incident on the diffractive optical element 5 forms an annular light intensity distribution on the pupil plane of the afocal lens 6 and then exits from the afocal lens 6 as a substantially parallel light beam.

  On the pupil surface of the afocal lens 6 or in the vicinity thereof, a polarization conversion unit 7 having a correction member 71 and a polarization conversion member 72 and a conical axicon system 8 are arranged in this order from the light incident side. The configuration and operation of the polarization conversion unit 7 and the conical axicon system 8 will be described later. Hereinafter, the basic configuration and operation of the exposure apparatus will be described ignoring the operations of the polarization conversion unit 7 and the conical axicon system 8. The light beam that has passed through the afocal lens 6 passes through a zoom lens 9 for varying the σ value (σ value = mask-side numerical aperture of the illumination optical system / mask-side numerical aperture of the projection optical system), and is a micro fly as an optical integrator. The light enters the eye lens (or fly eye lens) 10.

  The micro fly's eye lens 10 is an optical element composed of a large number of microlenses having positive refractive power arranged densely in the vertical and horizontal directions. In general, a micro fly's eye lens is configured by, for example, performing etching treatment on a plane-parallel plate to form a micro lens group. Each micro lens constituting the micro fly's eye lens is smaller than each lens element constituting the fly eye lens. Further, unlike a fly-eye lens composed of lens elements isolated from each other, a micro fly-eye lens is formed integrally with a large number of micro lenses (micro refractive surfaces) without being isolated from each other.

  However, the micro fly's eye lens is the same wavefront division type optical integrator as the fly eye lens in that lens elements having positive refractive power are arranged vertically and horizontally. As the micro fly's eye lens 10, for example, a cylindrical micro fly's eye lens can be used. The configuration and action of the cylindrical micro fly's eye lens are disclosed in, for example, US Pat. No. 6,913,373.

  The position of the predetermined plane IP is disposed in the vicinity of the front focal position of the zoom lens 9, and the incident surface of the micro fly's eye lens 10 is disposed in the vicinity of the rear focal position of the zoom lens 9. In other words, the zoom lens 9 arranges the predetermined plane IP and the incident surface of the micro fly's eye lens 10 substantially in a Fourier transform relationship, and consequently the pupil plane of the afocal lens 6 and the incident surface of the micro fly's eye lens 10. Are arranged almost conjugate optically. Therefore, on the incident surface of the micro fly's eye lens 10, for example, a ring-shaped illumination field centered on the optical axis AX is formed in the same manner as the pupil surface of the afocal lens 6. The overall shape of the annular illumination field changes in a similar manner depending on the focal length of the zoom lens 9.

  Each microlens constituting the micro fly's eye lens 10 has a rectangular cross section similar to the shape of the illumination field to be formed on the mask M (and thus the shape of the exposure region to be formed on the wafer W). The light beam incident on the micro fly's eye lens 10 is two-dimensionally divided by a large number of micro lenses, and the incident surface of the micro fly's eye lens 10 on the rear focal plane or in the vicinity of the illumination pupil as shown in FIG. A secondary light source having a light intensity distribution substantially the same as the illumination field formed on the light source, that is, a secondary light source (annular pupil intensity distribution) 20 composed of a substantial annular light source centered on the optical axis AX. Is done.

  The light beam from the secondary light source 20 formed on the illumination pupil immediately after the micro fly's eye lens 10 illuminates the mask blind 12 in a superimposed manner after passing through the condenser optical system 11. Thus, a rectangular illumination field corresponding to the shape and focal length of each microlens constituting the micro fly's eye lens 10 is formed on the mask blind 12 as an illumination field stop. The light beam that has passed through the rectangular opening (light transmitting portion) of the mask blind 12 receives the light condensing action of the imaging optical system 13 and then illuminates the mask M on which a predetermined pattern is formed in a superimposed manner.

  That is, the imaging optical system 13 forms an image of the rectangular opening of the mask blind 12 on the mask M. The pupil plane of the imaging optical system 13 is another illumination pupil plane at a position optically conjugate with the rear focal plane of the micro fly's eye lens 10 or the illumination pupil plane in the vicinity thereof. Accordingly, an annular pupil intensity distribution is formed on the pupil plane of the imaging optical system 13 as well as the illumination pupil immediately after the micro fly's eye lens 10.

  The light beam transmitted through the mask M held on the mask stage MS forms an image of a mask pattern on the wafer (photosensitive substrate) W held on the wafer stage WS via the projection optical system PL. In this way, batch exposure or scan exposure is performed while the wafer stage WS is two-dimensionally driven and controlled in a plane (XY plane) orthogonal to the optical axis AX of the projection optical system PL, and thus the wafer W is two-dimensionally driven and controlled. As a result, the pattern of the mask M is sequentially exposed in each exposure region of the wafer W.

  The conical axicon system 8 includes, in order from the light source side, a first prism member 8a having a flat surface facing the light source side and a concave conical refractive surface facing the mask side, and a convex conical shape facing the plane toward the mask side and the light source side. And a second prism member 8b facing the refractive surface. The concave conical refracting surface of the first prism member 8a and the convex conical refracting surface of the second prism member 8b are complementarily formed so as to be in contact with each other. Further, at least one of the first prism member 8a and the second prism member 8b is configured to be movable along the optical axis AX, and the concave conical refracting surface of the first prism member 8a and the second prism member 8b. The distance from the convex conical refracting surface is variable.

  In a state where the concave conical refracting surface of the first prism member 8a and the convex conical refracting surface of the second prism member 8b are in contact with each other, the conical axicon system 8 functions as a parallel flat plate, and is formed in a ring shape There is no effect on the secondary light source. However, if the concave conical refracting surface of the first prism member 8a and the convex conical refracting surface of the second prism member 8b are separated, the width of the annular secondary light source (the outer diameter of the annular secondary light source) The outer diameter (inner diameter) of the ring-shaped secondary light source changes while keeping 1/2 of the difference from the inner diameter constant. That is, the annular ratio (inner diameter / outer diameter) and size (outer diameter) of the annular secondary light source change.

  The zoom lens 9 has a function of enlarging or reducing the entire shape of the annular secondary light source in a similar (isotropic) manner. For example, by enlarging the focal length of the zoom lens 9 from a minimum value to a predetermined value, the entire shape of the annular secondary light source is similarly enlarged. In other words, due to the action of the zoom lens 9, both the width and size (outer diameter) change without changing the annular ratio of the annular secondary light source. In this way, the annular ratio and size (outer diameter) of the annular secondary light source can be controlled by the action of the conical axicon system 8 and the zoom lens 9.

  In the present embodiment, as described above, the secondary light source formed by the micro fly's eye lens 10 is used as the light source, and the mask M arranged on the irradiated surface of the illumination optical system (2-13) is Koehler illuminated. For this reason, the position where the secondary light source is formed is optically conjugate with the position of the aperture stop AS of the projection optical system PL, and the formation surface of the secondary light source is the illumination pupil plane of the illumination optical system (2-13). Can be called. Typically, the irradiated surface (the surface on which the mask M is disposed or the surface on which the wafer W is disposed when the illumination optical system including the projection optical system PL is considered) is optical with respect to the illumination pupil plane. A Fourier transform plane.

  The pupil intensity distribution is a light intensity distribution (luminance distribution) on the illumination pupil plane of the illumination optical system (2-13) or a plane optically conjugate with the illumination pupil plane. When the number of wavefront divisions by the micro fly's eye lens 10 is relatively large, the overall light intensity distribution formed on the incident surface of the micro fly's eye lens 10 and the overall light intensity distribution (pupil intensity distribution) of the entire secondary light source. ) And a high correlation. Therefore, the light intensity distribution on the incident surface of the micro fly's eye lens 10 and a surface optically conjugate with the incident surface (for example, the pupil surface of the afocal lens 6) can also be referred to as a pupil intensity distribution.

  In place of the diffractive optical element 5 for annular illumination, a diffractive optical element (not shown) for multipole illumination is set in the illumination optical path to thereby provide multipole illumination (bipolar illumination, quadrupole illumination, octupole illumination). Etc.). A diffractive optical element for multipole illumination has a light intensity distribution of multiple poles (bipolar, quadrupole, octupole, etc.) in its far field when a parallel light beam having a rectangular cross section is incident. Has the function of forming. Therefore, the light beam that has passed through the diffractive optical element for multipole illumination has a multipolar illumination field composed of, for example, a plurality of circular illumination fields centered on the optical axis AX on the incident surface of the micro fly's eye lens 10. Form. As a result, the same multipolar secondary light source as the illumination field formed on the incident surface is also formed on the illumination pupil immediately after the micro fly's eye lens 10.

  Moreover, instead of the diffractive optical element 5 for annular illumination, normal circular illumination can be performed by setting a diffractive optical element (not shown) for circular illumination in the illumination optical path. The diffractive optical element for circular illumination has a function of forming a circular light intensity distribution in the far field when a parallel light beam having a rectangular cross section is incident. Therefore, the light beam that has passed through the diffractive optical element for circular illumination forms, for example, a circular illumination field around the optical axis AX on the incident surface of the micro fly's eye lens 10. As a result, a secondary light source having the same circular shape as the illumination field formed on the incident surface is also formed on the illumination pupil immediately after the micro fly's eye lens 10. Further, instead of the diffractive optical element 5 for annular illumination, various forms of modified illumination can be performed by setting a diffractive optical element (not shown) having appropriate characteristics in the illumination optical path.

  FIG. 3 is a diagram schematically showing a cross-sectional configuration along the YZ plane of the polarization conversion unit. FIG. 4 is a perspective view schematically showing a characteristic surface shape of the polarization conversion member in the polarization conversion unit. As described above, the polarization conversion unit 7 is disposed on or near the pupil plane of the afocal lens 6, that is, on the illumination pupil of the illumination optical system (2-13) or in the vicinity thereof. Therefore, when the diffractive optical element 5 for annular illumination is arranged in the illumination optical path, a light beam having an annular cross section enters the polarization conversion unit 7.

  As shown in FIG. 3, the polarization conversion unit 7 includes a correction member 71 and a polarization conversion member 72 in order from the light incident side (light source side; left side in FIG. 3). The polarization conversion member 72 is formed of a crystal material that is an optical material having optical activity, such as quartz, and has a form in which the thickness continuously changes along the circumferential direction of a circle centered on the optical axis AX. As an example, the incident-side surface 72a of the polarization conversion member 72 is formed into a surface shape having a linear step as shown in FIG. 4, and the exit-side (mask-side) surface 72b is formed into a planar shape.

  Specifically, the incident-side surface 72a of the polarization converting member 72 has a linear step extending over the entire surface 72a along the Z direction through the optical axis AX. The semicircular surface 72aa on the + X direction side of the step is linearly increased from the + Z direction side to the −Z direction side along the circumferential direction of the semicircle centered on the optical axis AX. Is formed. On the other hand, the thickness of the semicircular surface 72ab on the −X direction side of the step increases linearly from the −Z direction side to the + Z direction side along the circumferential direction of the semicircle centered on the optical axis AX. It is formed as follows. Here, when considering a cylindrical (cylindrical) coordinate system with the XZ plane orthogonal to the optical axis AX as a reference plane and the position of the optical axis AX on the reference plane as the origin, a semicircular shape on the + X direction side from the step The thickness of the semicircular surface 72ab on the −X direction side of the surface 72aa and the step difference in the optical axis direction (Y direction) depends only on the declination that is the azimuth angle around the optical axis AX. It has a curved shape.

  The correction member 71 is disposed adjacent to the incident side of the polarization conversion member 72 and is made of an optical material having the same refractive index as that of the polarization conversion member 72, that is, quartz. The correction member 71 has a required surface shape for functioning as a compensator that compensates for the light deflection action (change in the traveling direction of light) by the polarization conversion member 72. Specifically, the incident-side surface 71 a of the correction member 71 is formed in a flat shape, and the exit-side surface 71 b has a surface shape complementary to the surface shape of the incident-side surface 72 a of the polarization conversion member 72.

  The correction member 71 is arranged so that the crystal optical axis is parallel or perpendicular to the polarization direction of the incident light so as not to change the polarization state of the light passing therethrough. In order to change the polarization state of incident light, the polarization conversion member 72 is set so that the crystal optical axis thereof substantially coincides with the optical axis AX (that is, substantially coincides with the Y direction as the traveling direction of incident light). . Hereinafter, with reference to FIG. 5, the optical rotation of the crystal will be briefly described. Referring to FIG. 5, a parallel flat plate-like optical member 100 made of quartz having a thickness d is arranged so that the crystal optical axis thereof coincides with the optical axis AX. In this case, due to the optical rotation of the optical member 100, the incident linearly polarized light is emitted in a state where the polarization direction is rotated by θ around the optical axis AX.

At this time, the rotation angle (optical rotation angle) θ in the polarization direction due to the optical rotation of the optical member 100 is expressed by the following formula (a) by the thickness d of the optical member 100 and the optical rotation ρ of the crystal. In general, the optical rotation ρ of quartz has a wavelength dependency (a property in which the value of optical rotation varies depending on the wavelength of the light used: optical rotation dispersion), and specifically, it tends to increase as the wavelength of the light used decreases. is there. According to the description on page 167 of “Applied Optics II”, the optical rotation power ρ of quartz with respect to light having a wavelength of 250.3 nm is 153.9 degrees / mm.
θ = d · ρ (a)

  In the present embodiment, for example, when Z-direction linearly polarized light having a polarization direction in the Z direction is incident on the polarization conversion unit 7 (and thus on the polarization conversion member 72), continuous circumferentially polarized light immediately after the polarization conversion member 72. The thickness distribution of the polarization conversion member 72 is set so that the light intensity distribution in the state is formed. That is, the polarization conversion member 72 is a linearly polarized light in which the Z-direction linearly polarized light incident on an arbitrary point on the incident surface 72a has a polarization direction in the tangential direction of a circle passing through the incident point with the optical axis AX as the center. It is formed to be converted into light.

  Thus, when the Z-direction linearly polarized light is incident on the polarization conversion unit 7, a continuous light intensity distribution in the circumferential direction is formed immediately after the polarization conversion member 72, and as a result, illumination immediately after the micro fly's eye lens 10. As shown in FIG. 6, an annular light intensity distribution 21 is formed in the pupil in a continuous circumferential polarization state. Furthermore, the position of another illumination pupil optically conjugate with the illumination pupil immediately after the micro fly's eye lens 10, that is, the pupil position of the imaging optical system 13 and the pupil position of the projection optical system PL (the aperture stop AS is disposed). ), An annular light intensity distribution is formed in a continuous circumferential polarization state corresponding to the light intensity distribution 21.

  In general, in the circumferential polarization illumination based on the annular intensity distribution in the circumferential polarization state or a multipolar (bipolar, quadrupole, octupole, etc.) pupil intensity distribution, the wafer W as the final irradiated surface is formed. The irradiated light becomes a polarization state mainly composed of S-polarized light. Here, the S-polarized light is linearly polarized light having a polarization direction in a direction perpendicular to the incident surface (polarized light having an electric vector oscillating in a direction perpendicular to the incident surface). However, the incident surface is defined as a surface including the normal of the boundary surface at that point and the incident direction of light when the light reaches the boundary surface of the medium (surface to be irradiated: the surface of the wafer W). The As a result, in the circumferential polarization illumination, the optical performance (such as depth of focus) of the projection optical system can be improved, and a mask pattern image with high contrast can be obtained on the wafer (photosensitive substrate).

  If the correction member 71 is omitted, the light traveling direction is changed by the refraction action (and hence the deflection action) of the polarization conversion member 72, and the pupil intensity has a desired circumferential direction polarization state and a desired size and shape. The distribution cannot be formed at a desired position. As a result, light does not form an image in a desired circumferentially polarized state on the wafer, and as a result, it becomes difficult to form a mask pattern image on the wafer with a required contrast.

  As described above, in the polarization conversion unit 7 of the present embodiment, the polarization conversion member 72 having a form in which the thickness continuously changes along the circumferential direction of a circle formed of quartz and centered on the optical axis AX. Due to the optical rotation, a continuous light intensity distribution in the circumferential direction is formed immediately after the polarization conversion member 72. The light deflection action by the polarization conversion member 72 is compensated by the action of the correction member 71 arranged on the incident side. Thus, an annular light intensity distribution 21 is formed on the illumination pupil immediately after the micro fly's eye lens 10 in a continuous circumferential polarization state. That is, in the polarization conversion unit 7 of this embodiment, it is arrange | positioned in the optical path of an illumination optical system (2-13), and can implement | achieve a zone-shaped pupil intensity distribution in the continuous circumferential direction polarization state.

  In the illumination optical system (2 to 13) of this embodiment, the mask M is masked with light in a desired circumferential polarization state using the polarization conversion unit 7 that realizes an annular pupil intensity distribution in a continuous circumferential polarization state. The pattern surface (irradiated surface) can be illuminated. Further, in the exposure apparatus (2 to WS) of the present embodiment, the illumination optical system (2 to 13) that illuminates the pattern surface of the mask M with light having a desired circumferential polarization state is used. A fine pattern can be accurately transferred onto the wafer W by exerting the effect of circumferentially polarized light satisfactorily under appropriate illumination conditions realized in accordance with the characteristics of the pattern.

  In the above-described embodiment, the Z-direction linearly polarized light is incident on the polarization conversion unit 7. However, when the X-direction linearly polarized light having the polarization direction in the X direction is incident on the polarization conversion unit 7, the polarized light is polarized. A light intensity distribution in a continuous radial polarization state is formed immediately after the conversion member 72, and as a result, a ring-like shape in a continuous radial polarization state is formed on the illumination pupil immediately after the micro fly's eye lens 10 as shown in FIG. A light intensity distribution 22 is formed. Further, an annular light intensity distribution is formed in a continuous radial polarization state corresponding to the light intensity distribution 22 at the pupil position of the imaging optical system 13 and the pupil position of the projection optical system PL.

  In general, in radial polarization illumination based on an annular or multipolar pupil intensity distribution in the radial polarization state, the light irradiated on the wafer W as the final irradiated surface is a polarization state in which P-polarized light is the main component. become. Here, the P-polarized light is linearly polarized light having a polarization direction in a direction parallel to the incident surface defined as described above (polarized light whose electric vector is oscillating in a direction parallel to the incident surface). is there. As a result, in the radial polarization illumination, a good mask pattern image can be obtained on the wafer (photosensitive substrate) while suppressing the reflectance of light in the resist applied to the wafer W to be small.

  Moreover, in the above-mentioned embodiment, this invention is demonstrated based on the polarization conversion unit 7 which has a specific structure shown in FIG.1, FIG3 and FIG.4. However, the specific configuration of the polarization conversion unit is not limited to this specific configuration, and various forms are possible. Specifically, the arrangement of the polarization conversion unit, the material of the polarization conversion member, the surface shape of the polarization conversion member, the material of the correction member, the surface shape of the correction member, the positional relationship between the polarization conversion member and the correction member, etc. Is possible.

  For example, in the above-described embodiment, the polarization conversion unit 7 is disposed on or near the pupil plane of the afocal lens 6. However, the present invention is not limited to this, and the polarization conversion unit 7 can be arranged at the position of another illumination pupil of the illumination optical system (2 to 13) or a position in the vicinity thereof. Specifically, the polarization conversion unit 7 can be arranged near the entrance surface of the micro fly's eye lens 10, near the exit surface of the micro fly's eye lens 10, the pupil of the imaging optical system 13, or the vicinity thereof.

  In the above-described embodiment, both the correction member 71 and the polarization conversion member 72 are made of quartz. However, the present invention is not limited to this, and the polarization conversion member can be formed of an optical material having optical activity other than quartz. In addition, the polarization conversion member and the correction member can be formed of different optical materials, that is, optical materials having different refractive indexes. As an example, the polarization conversion member can be formed of quartz, and the correction member can be formed of fluorite or quartz.

  In this case, the polarization conversion member has one planar optical surface (corresponding to the surface 72b in FIG. 3) and the other non-planar optical surface (corresponding to the surface 72a in FIG. 3). The correction member has one planar optical surface (corresponding to the surface 71a in FIG. 3) and the other optical surface having a surface shape slightly different from the surface shape complementary to the other optical surface of the polarization conversion member ( Corresponding to the surface 71b in FIG. Specifically, the surface shape of the other optical surface of the correction member is defined according to the surface shape of the other optical surface of the corresponding polarization conversion member and the refractive index difference between quartz and fluorite or quartz. The Further, since the correction member formed of fluorite or quartz does not change the polarization state of the incident light, the correction member can be disposed on the incident side or the emission side of the polarization conversion member.

  In the above-described embodiment, the correction member 71 and the polarization conversion member 72 are arranged adjacent to each other. However, the present invention is not limited to this, and a configuration including a relay optical system that optically conjugates the correction member and the polarization conversion member to each other is also possible.

  In the above-described embodiment, the incident side surface 72a of the polarization conversion member 72 has a linear step extending along the Z direction through the optical axis AX, that is, the diameter of the surface 72a is 9. It has a corresponding linear step. However, the present invention is not limited to this, and for example, a non-planar surface (corresponding to the surface 72a in FIG. 3) of the polarization conversion member extends along the Z direction from the optical axis AX (with a radius of the surface). A form having a corresponding linear step) is also possible. In this case, the non-planar surface is formed into a surface shape whose thickness varies linearly along the circumferential direction of the circle centered on the optical axis and over the entire circumferential direction. Become.

  In the above description, the operational effects of the present invention are described by taking, as an example, modified illumination in which an annular pupil intensity distribution is formed on the illumination pupil, that is, annular illumination. However, the present invention is similarly applied to, for example, multipolar illumination in which a multipolar pupil intensity distribution is formed without being limited to annular illumination, and the same operational effects can be obtained. Is clear.

  In the above-described embodiment, the micro fly's eye lens 10 is used as the optical integrator, but instead, an internal reflection type optical integrator (typically a rod type integrator) may be used. In this case, a condensing optical system that condenses light from the predetermined surface IP is disposed instead of the zoom lens 9. Then, instead of the micro fly's eye lens 10 and the condenser optical system 11, a rod type is used so that the incident end is positioned at or near the rear focal position of the condensing optical system for condensing the light from the predetermined surface IP. Place the integrator. At this time, the injection end of the rod type integrator is positioned at the mask blind 12. When using a rod type integrator, a position optically conjugate with the position of the aperture stop AS of the projection optical system PL in the imaging optical system 13 downstream of the rod type integrator can be called an illumination pupil plane. In addition, since a virtual image of the secondary light source of the illumination pupil plane is formed at the position of the entrance surface of the rod integrator, this position and a position optically conjugate with this position are also called the illumination pupil plane. Can do. Here, the condensing optical system, the imaging optical system, and the rod integrator can be regarded as a distribution forming optical system.

  In the above-described embodiment, a variable pattern forming apparatus that forms a predetermined pattern based on predetermined electronic data can be used instead of a mask. As the variable pattern forming apparatus, for example, a DMD (digital micromirror device) including a plurality of reflecting elements driven based on predetermined electronic data can be used. An exposure apparatus using DMD is disclosed in, for example, Japanese Patent Application Laid-Open No. 2004-304135, International Patent Publication No. 2006/080285 pamphlet and US Patent Publication No. 2007/0296936 corresponding thereto. In addition to a non-light-emitting reflective spatial light modulator such as DMD, a transmissive spatial light modulator may be used, or a self-luminous image display element may be used. Here, the teachings of US Patent Publication No. 2007/0296936 are incorporated by reference.

  The exposure apparatus of the above-described embodiment is manufactured by assembling various subsystems including the respective constituent elements recited in the claims of the present application so as to maintain predetermined mechanical accuracy, electrical accuracy, and optical accuracy. Is done. 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 may be manufactured in a clean room where the temperature, cleanliness, etc. are controlled.

  Next, a device manufacturing method using the exposure apparatus according to the above-described embodiment will be described. FIG. 8 is a flowchart showing a semiconductor device manufacturing process. As shown in FIG. 8, in the semiconductor device manufacturing process, a metal film is vapor-deposited on a wafer W to be a substrate of the semiconductor device (step S40), and a photoresist, which is a photosensitive material, is applied on the vapor-deposited metal film. (Step S42). Subsequently, using the exposure apparatus of the above-described embodiment, the pattern formed on the mask (reticle) M is transferred to each shot area on the wafer W (step S44: exposure process), and the transfer of the wafer W after the transfer is completed. Development, that is, development of the photoresist to which the pattern has been transferred is performed (step S46: development process).

  Thereafter, using the resist pattern generated on the surface of the wafer W in step S46 as a mask, processing such as etching is performed on the surface of the wafer W (step S48: processing step). Here, the resist pattern is a photoresist layer in which unevenness having a shape corresponding to the pattern transferred by the exposure apparatus of the above-described embodiment is generated, and the recess penetrates the photoresist layer. is there. In step S48, the surface of the wafer W is processed through this resist pattern. The processing performed in step S48 includes, for example, at least one of etching of the surface of the wafer W or film formation of a metal film or the like.

  FIG. 9 is a flowchart showing manufacturing steps of a liquid crystal device such as a liquid crystal display element. As shown in FIG. 9, in the liquid crystal device manufacturing process, a pattern forming process (step S50), a color filter forming process (step S52), a cell assembling process (step S54), and a module assembling process (step S56) are sequentially performed. In the pattern forming process of step S50, a predetermined pattern such as a circuit pattern and an electrode pattern is formed on the glass substrate coated with a photoresist as the plate P using the projection exposure apparatus of the above-described embodiment. The pattern forming step includes an exposure step of transferring the pattern to the photoresist layer using the projection exposure apparatus of the above-described embodiment, and development of the plate P on which the pattern is transferred, that is, development of the photoresist layer on the glass substrate. And a developing step for generating a photoresist layer having a shape corresponding to the pattern, and a processing step for processing the surface of the glass substrate through the developed photoresist layer.

  In the color filter forming process in step S52, a large number of sets of three dots corresponding to R (Red), G (Green), and B (Blue) are arranged in a matrix or three R, G, and B A color filter is formed by arranging a plurality of stripe filter sets in the horizontal scanning direction. In the cell assembly process in step S54, a liquid crystal panel (liquid crystal cell) is assembled using the glass substrate on which the predetermined pattern is formed in step S50 and the color filter formed in step S52. Specifically, for example, a liquid crystal panel is formed by injecting liquid crystal between a glass substrate and a color filter. In the module assembling process in step S56, various components such as an electric circuit and a backlight for performing the display operation of the liquid crystal panel are attached to the liquid crystal panel assembled in step S54.

  In addition, the present invention is not limited to application to an exposure apparatus for manufacturing a semiconductor device, for example, an exposure apparatus for a display device such as a liquid crystal display element formed on a square glass plate or a plasma display, It can also be widely applied to an exposure apparatus for manufacturing various devices such as an image sensor (CCD or the like), a micromachine, a thin film magnetic head, and a DNA chip. Furthermore, the present invention can also be applied to an exposure process (exposure apparatus) when manufacturing a mask (photomask, reticle, etc.) on which mask patterns of various devices are formed using a photolithography process.

In the above-described embodiment, ArF excimer laser light (wavelength: 193 nm) or KrF excimer laser light (wavelength: 248 nm) is used as the exposure light. However, the present invention is not limited to this, and other appropriate laser light sources are used. For example, the present invention can also be applied to an F ₂ laser light source that supplies laser light having a wavelength of 157 nm.

  In the above-described embodiment, a so-called immersion method is applied in which the optical path between the projection optical system and the photosensitive substrate is filled with a medium (typically liquid) having a refractive index larger than 1.1. You may do it. In this case, as a technique for filling the liquid in the optical path between the projection optical system and the photosensitive substrate, a technique for locally filling the liquid as disclosed in International Publication No. WO99 / 49504, a special technique, A method of moving a stage holding a substrate to be exposed as disclosed in Kaihei 6-124873 in a liquid bath, or a predetermined stage on a stage as disclosed in JP-A-10-303114. A method of forming a liquid tank having a depth and holding the substrate therein can be employed. Here, the teachings of International Publication No. WO99 / 49504, JP-A-6-124873 and JP-A-10-303114 are incorporated by reference.

  In the above-described embodiment, the present invention is applied to the illumination optical system that illuminates the mask (or wafer) in the exposure apparatus. However, the present invention is not limited to this, and an object other than the mask (or wafer) is used. The present invention can also be applied to a general illumination optical system that illuminates the irradiation surface.

DESCRIPTION OF SYMBOLS 1 Light source 4 Polarization state switching part 5 Diffractive optical element 6 Afocal lens 7 Polarization conversion unit 71 Correction member 72 Polarization conversion member 8 Conical axicon system 9 Zoom lens 10 Micro fly eye lens 11 Condenser optical system 12 Mask blind 13 Imaging optical system M Mask PL Projection optical system W Wafer

Claims (19)

In a polarization conversion unit that converts incident light into light having a predetermined polarization state and emits the light,
A polarization conversion member that is formed of a first optical material having optical rotation and has a form in which a thickness continuously changes along a circumferential direction of a circle centered on an optical axis, and changes a polarization state of incident light; ,
A correction member that is disposed on the incident side or the emission side of the polarization conversion member and compensates for the light deflection action of the polarization conversion member ,
The correction member is formed of a second optical material having a refractive index different from that of the first optical material, and is a surface shape defined according to a refractive index difference between the first optical material and the second optical material. A polarization conversion unit characterized by having an optical surface . The polarization conversion unit according to claim 1 , wherein the surface shape of the correction member is defined according to the surface shape of the optical surface of the polarization conversion member . The polarization conversion unit according to claim 1, wherein the polarization conversion member is made of quartz . 4. The polarization conversion unit according to claim 3, wherein the correction member is made of quartz and is disposed on the incident side of the polarization conversion member . In a polarization conversion unit that converts incident light into light having a predetermined polarization state and emits the light,
A polarization conversion member that is formed of quartz and has a form in which the thickness continuously changes along the circumferential direction of a circle centered on the optical axis, and changes the polarization state of incident light;
A correction member that is formed of quartz and compensates for the light deflection effect of the polarization conversion member,
The polarization conversion unit , wherein the correction member is disposed on an incident side of the polarization conversion member . 6. The polarization conversion unit according to claim 4, wherein the correction member is arranged so that a crystal optical axis is parallel or perpendicular to a polarization direction of incident light . The polarization conversion member has one planar optical surface orthogonal to the optical axis,
The correction member has one planar optical surface orthogonal to the optical axis and the other optical surface having a surface shape complementary to the surface shape of the other optical surface of the polarization conversion member. The polarization conversion unit according to any one of claims 4 to 6 . 4. The polarization conversion unit according to claim 3 , wherein the correction member is made of fluorite or quartz, and is disposed on the incident side or the emission side of the polarization conversion member . The polarization conversion member has one planar optical surface orthogonal to the optical axis,
The correction member is defined according to one planar optical surface orthogonal to the optical axis, the surface shape of the other optical surface of the polarization conversion member, and the refractive index difference between quartz and fluorite or quartz. The polarization conversion unit according to claim 8 , further comprising: another optical surface having a surface shape to be formed . The polarization conversion unit according to claim 1, wherein the polarization conversion member and the correction member are disposed adjacent to each other . 11. The optical path of an illumination optical system that illuminates the illuminated surface with light from a light source, wherein the illumination optical system is disposed at or near the illumination pupil of the illumination optical system. The polarization conversion unit described. In the region where the thickness continuously changes along the circumferential direction of the circle in the polarization conversion member, linearly polarized light having a polarization direction in a predetermined direction incident on the region is centered on the optical axis. The polarization conversion unit according to any one of claims 1 to 11, wherein the polarization conversion unit converts the light into a circumferentially polarized light having a polarization direction in a tangential direction of the circle or a radial polarization having a polarization direction in a radial direction of the circle. . The change in the thickness of the polarization conversion member along the circumferential direction of the circle is expressed by a cylindrical coordinate system in which a plane perpendicular to the optical axis is a reference plane and the position of the optical axis on the reference plane is an origin. The polarization conversion unit according to any one of claims 1 to 12, wherein the polarization conversion unit depends only on a declination angle . In the illumination optical system that illuminates the illuminated surface with light from the light source,
An illumination optical system comprising the polarization conversion unit according to any one of claims 1 to 13, which is disposed in an optical path between the light source and the irradiated surface . The illumination optical system according to claim 14, wherein the polarization conversion unit is disposed at or near an illumination pupil of the illumination optical system . The projection pupil is used in combination with a projection optical system that forms a surface optically conjugate with the irradiated surface, and the illumination pupil is at a position optically conjugate with an aperture stop of the projection optical system. 15. The illumination optical system according to 15 . 17. An exposure apparatus comprising the illumination optical system according to claim 14 for illuminating a predetermined pattern, and exposing the predetermined pattern onto a photosensitive substrate . The exposure apparatus according to claim 17, further comprising a projection optical system that forms an image of the predetermined pattern on the photosensitive substrate. An exposure process for exposing the predetermined pattern to the photosensitive substrate using the exposure apparatus according to claim 17 or 18,
Developing the photosensitive substrate to which the predetermined pattern is transferred, and forming a mask layer having a shape corresponding to the predetermined pattern on the surface of the photosensitive substrate;
And a processing step of processing the surface of the photosensitive substrate through the mask layer.

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