JP2010283249A - Illumination optical system, exposure device, and device manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a lighting area which has a trapezoidal light intensity distribution in a prescribed direction and also has a pupil intensity distribution in a substantially uniform shape with respect to each point. <P>SOLUTION: An illumination optical system which lights up a surface (M; W) to be irradiated with light from a light source (1) includes: an optical integrator (7) having a plurality of wavefront division elements arranged in two dimensions and in parallel; and a condensing optical system (8) which condenses luminous flux passed through the wavefront division elements. A first distance along the optical axis of the illumination optical system between a first rear-side focus position of a wavefront division element associated with a first direction (X direction) in a plane (XZ plane) orthogonal to the optical axis (AX) and a front-side focus position of the condensing optical system is larger than a second distance along the optical axis between a second rear-side focus position of the wavefront division element associated with a second direction (Z direction) in the plane and a front-side focus position of the condensing optical system. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to 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 a device such as a semiconductor element, an imaging element, a liquid crystal display element, and a thin film magnetic head in a lithography process.

  In a typical exposure apparatus of this type, light emitted from a light source forms a secondary light source as a substantial surface light source including a large number of light sources via a fly-eye lens as an optical integrator. The light from the secondary light source is condensed by the condenser lens 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 a wafer (photosensitive substrate) via a projection optical system, and a mask pattern is projected and exposed (transferred) onto the wafer.

  2. Description of the Related Art Conventionally, there is known a scanning type exposure apparatus that projects and exposes a mask pattern onto a wafer (scanning exposure) while moving the mask and the wafer relative to the projection optical system. In a scanning exposure apparatus, a rectangular illumination region (projection region) having a short side along the scanning direction (wafer moving direction) is formed on the wafer. In order to improve the accuracy of exposure amount control along the scanning direction in each shot area (exposure area) on the wafer, there is a technique for setting the light intensity distribution along the scanning direction in the rectangular illumination area to a trapezoidal shape. (For example, refer nonpatent literature 1).

  The technique proposed in Non-Patent Document 1 is formed on a wafer (and thus a mask) by the action of an illumination field stop disposed at a position optically conjugate with the wafer (and thus a mask) in the optical path of the illumination optical system. The outer shape of the illumination area is set to a rectangular shape. In addition, the light intensity distribution along the scanning direction in the rectangular illumination region is trapezoidal by the action of a light shielding member that is arranged at a slight distance from the illumination field stop in the optical axis direction and blocks a part of the illumination light beam. It is set.

Jpn. J. Appl. Phys. Vol. 34 (1995) pp. 6565-6572, Kazuaki Suzuki et al., "Dosage Control for Scanning Exposure with Pulsed Energy Fluctuation and Exposed Position Jitter"

  In the conventional technique in which the light intensity distribution along the scanning direction in the rectangular illumination area is set to a trapezoidal shape by the light shielding member arranged in the vicinity of the illumination field stop, only a light loss occurs due to the light shielding member. In other words, the pupil intensity distribution relating to the region corresponding to the hypotenuse of the trapezoid is partially lost, for example, an asymmetric shape with respect to the axis passing through the optical axis. That is, the pupil intensity distribution for one point in the region corresponding to the hypotenuse of the trapezoid (the pupil intensity distribution corresponding to light incident on one point) is different from the required shape. As a result, for example, when the transfer surface (exposure surface) of the wafer is tilted or defocused (position shift) with respect to the image surface of the projection optical system, it is difficult to accurately transfer the mask pattern to the wafer.

  The present invention has been made in view of the above-described problems, and forms an illumination region having a trapezoidal light intensity distribution along a predetermined direction and a substantially uniform pupil intensity distribution for each point. An object of the present invention is to provide an illumination optical system that can perform the above-mentioned. In addition, using an illumination optical system that has a trapezoidal light intensity distribution along a predetermined direction and forms an illumination region in which the shape of the pupil intensity distribution for each point is almost uniform, a pattern under good illumination conditions An object of the present invention is to provide an exposure apparatus and a device manufacturing method capable of performing accurate transfer of the above.

In order to solve the above problems, in the first embodiment of the present invention, in the illumination optical system that illuminates the illuminated surface based on the light from the light source,
An optical integrator having a plurality of wavefront dividing elements arranged in an optical path between the light source and the irradiated surface and arranged two-dimensionally in parallel;
A condensing optical system disposed in an optical path between the optical integrator and the irradiated surface, and condensing a light beam that has passed through the wavefront splitting element,
The first distance along the optical axis between the first rear focal position of the wavefront splitting element and the front focal position of the condensing optical system in a first direction within a plane orthogonal to the optical axis of the illumination optical system is And a second distance along the optical axis between the second rear focal position of the wavefront splitting element and the front focal position of the condensing optical system in the second direction in the plane. An illumination optical system is provided.

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

In the third embodiment of the present invention, using the exposure apparatus of the second 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 illumination optical system according to one aspect of the present invention, the light intensity distribution along the predetermined direction of the illumination area formed on the irradiated surface is trapezoidal due to the defocusing action on the condensing optical system of the wavefront dividing element with respect to the predetermined direction. Set to. In this case, since the light beam that forms the pupil intensity distribution of the required shape is not blocked by the illumination pupil immediately after the optical integrator, the shape of the pupil intensity distribution for each point becomes substantially uniform over the entire illumination area.

  In other words, the illumination optical system of the present invention can form an illumination region having a trapezoidal light intensity distribution along a predetermined direction and a substantially uniform pupil intensity distribution for each point. Therefore, in the exposure apparatus of the present invention, it is preferable to use an illumination optical system that has a trapezoidal light intensity distribution along a predetermined direction and forms an illumination region in which the shape of the pupil intensity distribution for each point is substantially uniform. The pattern can be accurately transferred under various illumination conditions, and as a result, 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 perspective view which shows schematically the structure of the cylindrical micro fly's eye lens of FIG. It is the 1st figure explaining the disadvantage of a prior art based on the structure corresponding to FIG. 1 and FIG. It is the 2nd figure explaining the disadvantage of a prior art based on the structure corresponding to FIG. 1 and FIG. It is a 1st figure explaining the principal part structure and effect | action of this embodiment. It is a 2nd figure explaining the principal part structure and effect | action of this embodiment. It is a perspective view which shows roughly the structure of the cylindrical micro fly's eye lens which has another form from FIG. 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 is along the normal direction of the transfer surface (exposure surface) of the wafer W, which is a photosensitive substrate, and the Y-axis is 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, an ArF excimer laser light source that supplies light with a wavelength of 193 nm, a KrF excimer laser light source that supplies light with a wavelength of 248 nm, or the like can be used. The light emitted from the light source 1 is converted into a light beam having a required cross-sectional shape by the shaping optical system 2 and then enters the afocal lens 4 via, for example, a diffractive optical element 3 for annular illumination.

  The afocal lens 4 includes a front lens group 4a and a rear lens group 4b. The front focal position of the front lens group 4a substantially coincides with the position of the diffractive optical element 3, and the rear focal point of the rear lens group 4b. This is an afocal system (non-focal optical system) set so that the position and the position of the predetermined surface 5 indicated by a broken line in the figure substantially coincide with each other. The diffractive optical element 3 is formed by forming a step having a pitch of about the wavelength of exposure light (illumination light) on the substrate, and has a function of diffracting an incident beam to a desired angle.

  Specifically, the diffractive optical element 3 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 3 is emitted from the afocal lens 4 with a ring-shaped angular distribution after forming a ring-shaped light intensity distribution on the pupil plane of the afocal lens 4.

  The light emitted from the afocal lens 4 passes through a zoom lens 6 for varying a σ value (σ value = mask-side numerical aperture of the illumination optical system / mask-side numerical aperture of the projection optical system) and is cylindrical as an optical integrator. The light enters the micro fly's eye lens 7. As shown in FIG. 2, the cylindrical micro fly's eye lens 7 includes a first fly eye member (first optical member) 7a disposed on the light source side and a second fly eye member (second optical member) disposed on the mask side. Member) 7b.

  On the light source side (incident side) surface of the first fly's eye member 7a and the light source side surface of the second fly's eye member 7b, a plurality of cylindrical refractive surfaces (cylindrical lens groups) arranged side by side in the X direction. ) 7aa and 7ba are formed with a pitch px. A plurality of cylindrical refractive surfaces (cylindrical lens groups) arranged side by side in the Z direction are provided on the mask side (exit side) surface of the first fly eye member 7a and the mask side surface of the second fly eye member 7b. 7ab and 7bb are formed with a pitch pz (pz> px).

  Focusing on the refraction action in the X direction of the cylindrical micro fly's eye lens 7 (that is, the refraction action in the XY plane), a group of parallel light beams incident along the optical axis AX are formed on the light source side of the first fly eye member 7a. Corresponding in a group of refracting surfaces 7ba formed on the light source side of the second fly's eye member 7b after being wave-divided by the refracting surface 7aa along the X direction at a pitch px and receiving a condensing action on the refracting surface. The light is focused on the refracting surface.

  Focusing on the refractive action in the Z direction of the cylindrical micro fly's eye lens 7 (ie, the refractive action in the YZ plane), a group of parallel light beams incident along the optical axis AX are formed on the mask side of the first fly's eye member 7a. Corresponding in the group of refracting surfaces 7bb formed on the mask side of the second fly's eye member 7b after the wavefront is divided at the pitch pz along the Z direction by the refracting surfaces 7ab The light is focused on the refracting surface.

  As described above, the cylindrical micro fly's eye lens 7 is composed of the first fly eye member 7a and the second fly eye member 7b in which the cylindrical lens group is formed on both side surfaces, and the size of px is set in the X direction. It has an optical function similar to that of a micro fly's eye lens in which a large number of rectangular minute refracting surfaces having a size of pz in the Z direction are integrally formed vertically and horizontally. That is, the cylindrical micro fly's eye lens 7 is configured by two-dimensionally arranging a number of wavefront division elements having a rectangular cross section having an X direction dimension of px and a Z direction dimension of pz along the XZ plane. It is an optical integrator.

  Each wavefront dividing element constituting the cylindrical micro fly's eye lens 7 has a rectangular wavefront dividing surface having a short side along the X direction and a long side along the Z direction. In the cylindrical micro fly's eye lens 7, a change in distortion due to variations in the surface shape of the microrefractive surface is suppressed to be small. For example, manufacturing errors of a large number of microrefractive surfaces integrally formed by etching process give the illuminance distribution. The influence can be kept small.

  The position of the predetermined surface 5 is disposed at or near the front focal position of the zoom lens 6, and the incident surface of the cylindrical micro fly's eye lens 7 (that is, the incident surface of the first fly's eye member 7 a) is the rear focal position of the zoom lens 6. Or it is arrange | positioned in the vicinity. In other words, in the zoom lens 6, the predetermined surface 5 and the incident surface of the cylindrical micro fly's eye lens 7 are arranged substantially in a Fourier transform relationship, and as a result, the pupil surface of the afocal lens 4 and the cylindrical micro fly's eye lens 7. The incident surface is optically substantially conjugate.

  Accordingly, on the incident surface of the cylindrical micro fly's eye lens 7, for example, an annular illumination field centered on the optical axis AX is formed in the same manner as the pupil surface of the afocal lens 4. The overall shape of the annular illumination field changes in a similar manner depending on the focal length of the zoom lens 6. As described above, each wavefront dividing element of the cylindrical micro fly's eye lens 7 has a rectangular unit wavefront dividing surface having a long side along the Z direction and a short side along the X direction. The unit wavefront dividing surface of the shape is a rectangular shape similar to the shape of the illumination region 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 cylindrical micro fly's eye lens 7 is two-dimensionally divided, and the illumination pupil immediately after that has a light intensity distribution substantially equal to that of the illumination field formed on the incident surface of the cylindrical micro fly's eye lens 7. A secondary light source (pupil intensity distribution) composed of a secondary light source, that is, a substantial surface light source having an annular shape with the optical axis AX as the center is formed.

  Immediately after the cylindrical micro fly's eye lens 7, an illumination aperture stop (not shown) having an annular opening (light transmitting part) corresponding to the annular secondary light source is disposed as necessary. The illumination aperture stop is configured to be detachable with respect to the illumination optical path, and is configured to be switchable with a plurality of aperture stops having apertures having different sizes and shapes. As an aperture stop switching method, for example, a well-known turret method or slide method can be used. The illumination aperture stop is disposed at a position optically conjugate with an entrance pupil plane of the projection optical system PL described later, and defines a range that contributes to illumination of the secondary light source.

  The light that has passed through the cylindrical micro fly's eye lens 7 illuminates the mask blind 9 in a superimposed manner via a condenser optical system 8. Thus, a rectangular illumination field corresponding to the shape and focal length of the unit wavefront dividing surface of the cylindrical micro fly's eye lens 7 is formed on the mask blind 9 as an illumination field stop. The light that has passed through the rectangular opening (light transmission portion) of the mask blind 9 passes through the imaging optical system 10 including the front lens group 10a and the rear lens group 10b, and the mask M on which a predetermined pattern is formed. Are illuminated in a superimposed manner.

  That is, the imaging optical system 10 forms an image of the rectangular opening of the mask blind 9 on the mask M. The pupil plane of the imaging optical system 10 is at a position optically conjugate with the illumination pupil immediately after the micro fly's eye lens 9, and an annular pupil intensity is also applied to the pupil plane of the imaging optical system 10 or the illumination pupil in the vicinity thereof. A distribution is formed.

  A pattern to be transferred is formed on the mask M held on the mask stage MS, and a rectangular shape having a long side along the Y direction and a short side along the X direction in the entire pattern region ( The pattern area of the slit shape is illuminated. The light transmitted through the pattern area of the mask M forms an image of the mask pattern on the wafer (photosensitive substrate) W held on the wafer stage WS via the projection optical system PL. That is, a rectangular stationary image having a long side along the Y direction and a short side along the X direction on the wafer W so as to optically correspond to the rectangular illumination area on the mask M. A pattern image is formed in the exposure area (effective exposure area).

  Thus, according to the so-called step-and-scan method, the mask stage MS and the wafer stage WS along the X direction (scanning direction) in the plane (XY plane) orthogonal to the optical axis AX of the projection optical system PL, As a result, by moving (scanning) the mask M and the wafer W synchronously, the wafer W has a width equal to the dimension in the Y direction of the static exposure region and corresponds to the scanning amount (movement amount) of the wafer W. A mask pattern is scanned and exposed to a shot area (exposure area) having a length.

  In the present embodiment, as described above, the secondary light source formed by the cylindrical micro fly's eye lens 7 is used as a light source, and the mask M disposed on the irradiated surface of the illumination optical system (2 to 10) 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 to 10). 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 to 10) or a plane optically conjugate with the illumination pupil plane. When the number of wavefront divisions by the cylindrical micro fly's eye lens 7 is relatively large, the overall light intensity distribution formed on the incident surface of the cylindrical micro fly's eye lens 7 and the overall light intensity distribution of the entire secondary light source (pupil) Intensity distribution). For this reason, the light intensity distribution on the incident surface of the cylindrical micro fly's eye lens 7 and a surface optically conjugate with the incident surface can also be referred to as a pupil intensity distribution.

  In place of the diffractive optical element 3 for annular illumination, a plurality of diffractive optical elements (not shown) for multipole illumination (two-pole illumination, four-pole illumination, octupole illumination, etc.) are set in the illumination optical path. Polar lighting can be performed. A diffractive optical element for multipole illumination forms a light intensity distribution of multiple poles (bipolar, quadrupole, octupole, etc.) in the far field when a parallel light beam having a rectangular cross section is incident. It has the function to do. Therefore, the light flux that has passed through the diffractive optical element for multipole illumination is irradiated on the incident surface of the cylindrical micro fly's eye lens 7 with, for example, a plurality of predetermined shapes (arc shape, circular shape, etc.) centered on the optical axis AX. A multipolar illumination field consisting of As a result, the same multipolar secondary light source as the illumination field formed on the incident surface is formed on the illumination pupil immediately after the cylindrical micro fly's eye lens 7.

  Moreover, instead of the diffractive optical element 3 for annular illumination, a 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 cylindrical micro fly's eye lens 7. 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 cylindrical micro fly's eye lens 7. Also, instead of the diffractive optical element 3 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. As a switching method of the diffractive optical element 3, for example, a known turret method or slide method can be used.

  Prior to the description of the main configuration and operation of the present embodiment, the disadvantages of the prior art proposed in Non-Patent Document 1 will be described based on the configuration corresponding to FIG. 1 and FIG. FIG. 3 shows a state in which an illumination field 34 is formed on a predetermined surface 33 via one wavefront splitting element 31 and a condensing optical system 32 disposed on the rear side. Note that the coordinates x, y, and z in FIG. 3 correspond to the coordinates X, Y, and Z in FIGS. 1 and 2.

  The wavefront splitting element 31 corresponds to one wavefront splitting element that constitutes the cylindrical micro fly's eye lens 7. In other words, the incident surface 31aa of the front element 31a of the wavefront splitting element 31 corresponds to a part of the cylindrical refracting surface 7aa formed on the incident side of the first fly's eye member 7a. The exit surface 31ab of the front element 31a corresponds to a part of the cylindrical refracting surface 7ab formed on the exit side of the first fly's eye member 7a.

  Similarly, the incident surface 31ba of the rear element 31b of the wavefront dividing element 31 corresponds to a part of the cylindrical refracting surface 7ba formed on the incident side of the second fly's eye member 7b. The exit surface 31bb of the rear element 31b corresponds to a part of the cylindrical refracting surface 7bb formed on the exit side of the second fly's eye member 7b. The condensing optical system 32 corresponds to the condenser optical system 8.

  The predetermined surface 33 corresponds to the surface of the opening of the mask blind 9, that is, a surface optically conjugate with the pattern surface of the mask M and the transfer surface of the wafer W. In FIG. 3, the upper diagram shows the configuration and operation (in the xy plane) related to the x direction that is the short side direction of the rectangular cross section of the wavefront dividing element 31, and the lower diagram relates to the z direction that is the long side direction ( The structure and action are shown in the yz plane.

  In the prior art proposed in Non-Patent Document 1, the rear focal position 31cx of the wavefront dividing element 31 in the x direction and the front focal position 32a of the condensing optical system 32 substantially coincide with each other along the optical axis. The rear focal position 31cz in the z direction of 31 and the front focal position 32a of the condensing optical system 32 substantially coincide with each other along the optical axis. Therefore, a rectangular illumination field 34 having a short side along the x direction and a long side along the z direction is formed on the rear focal position of the condensing optical system 32 or in the vicinity thereof. The

  At this time, as shown in FIG. 4, the light intensity distribution 34x of the illumination field 34 along the x direction which is the short side direction and the light intensity distribution 34z of the illumination field 34 along the z direction which is the long side direction are Both are rectangular (top hat shape with almost constant strength). In the prior art proposed in Non-Patent Document 1, the x-direction of the illumination light beam is arranged at a slight distance in the optical axis direction from the predetermined surface 33 corresponding to the surface of the opening of the mask blind 9 as an illumination field stop. A rectangular light intensity distribution along the x direction (corresponding to the X direction which is the scanning direction) while maintaining the light intensity distribution 34z along the z direction in a rectangular shape by the action of the light shielding member that blocks a part of the side 34x is changed to a trapezoidal light intensity distribution 34xa.

  In other words, the light shielding member blocks a part of the light flux that forms a pupil intensity distribution of a required shape on the illumination pupil immediately after the optical integrator composed of a large number of wavefront splitting elements 31 arranged two-dimensionally in parallel along the xz plane. As a result, the rectangular light intensity distribution 34x is changed to a trapezoidal light intensity distribution 34xa. Therefore, in the prior art, not only the light amount loss due to the light shielding member occurs, but also the pupil intensity related to the region 34a corresponding to the trapezoid hypotenuse of the light intensity distribution 34xa in the illumination field 34 (see the left side of FIG. 4). The distribution is partially lost, for example, an asymmetric shape with respect to an axis passing through the optical axis. The degree of loss of the pupil intensity distribution increases as it approaches the end in the x direction in the area 34a of the illumination field 34.

  Specifically, for example, in annular illumination, pupil intensity distribution related to one point in the region 34a corresponding to the hypotenuse of the trapezoid (light incident on one point in the region 34a is formed on the illumination pupil behind the predetermined surface 33) The light intensity distribution) differs greatly from the ring-shaped shape centered on the optical axis. As a result, when the conventional technique proposed in Non-Patent Document 1 is applied to the exposure apparatus of FIG. 1, for example, when the transfer surface of the wafer W is tilted or defocused with respect to the image plane of the projection optical system PL, It becomes difficult to accurately transfer the pattern of the mask M to the wafer W.

  FIG. 5 is a diagram for explaining the main configuration and operation of the present embodiment. Referring to FIG. 5, the incident surface of the front element 7ea of one wavefront splitting element 7e constituting the cylindrical micro fly's eye lens 7 is a cylindrical refractive surface 7aa formed on the incident side of the first fly's eye member 7a. Is part of. The exit surface of the front element 7ea is a part of a cylindrical refracting surface 7ab formed on the exit side of the first fly's eye member 7a.

  Similarly, the incident surface of the rear element 7eb of the wavefront dividing element 7e is a part of a cylindrical refracting surface 7ba formed on the incident side of the second fly's eye member 7b. The exit surface of the rear element 7eb is a part of a cylindrical refracting surface 7bb formed on the exit side of the second fly's eye member 7b. In FIG. 5, the upper diagram shows the configuration and operation related to the X direction (in the XY plane) that is the short side direction of the rectangular cross section of the wavefront dividing element 7e, and the lower diagram relates to the Z direction that is the long side direction ( The configuration and action are shown in the YZ plane.

  In the present embodiment, the rear focal position 7ez in the Z direction of the wavefront splitting element 7e of the cylindrical micro fly's eye lens 7 and the front focal position 8a of the condenser optical system 8 as the condensing optical system are substantially along the optical axis AX. Match. However, the rear focal position 7ex with respect to the X direction of the wavefront dividing element 7e (corresponding to the scanning direction of the mask and the wafer) is the front side (light source side) from the front focal position 8a of the condenser optical system 8 along the optical axis AX. ).

  In this case, the surface 9a of the opening of the mask blind 9 arranged at or near the rear focal position of the condenser optical system 8 has a short side along the X direction and a long side along the Z direction. A rectangular illumination field 54 is formed. Here, since the rear focal position 7ez in the Z direction of the wavefront dividing element 7e and the front focal position 8a of the condenser optical system 8 substantially coincide with each other along the optical axis AX, as shown in the right side of FIG. Furthermore, the light intensity distribution 54z along the Z direction (long side direction) of the illumination field 54 formed on the rear focal position of the condenser optical system 8 or the surface 9a in the vicinity thereof has a rectangular shape (top hat shape).

  On the other hand, the rear focal position 7ex in the X direction of the wavefront dividing element 7e and the front focal position 8a of the condenser optical system 8 are displaced by a certain distance dx along the optical axis AX. As shown in the figure on the left side, the light intensity distribution 54x of the illumination field 54 along the X direction (short side direction) of the illumination field 54 formed on the rear focal position of the condenser optical system 8 or the surface 9a in the vicinity thereof is It becomes trapezoid.

  In this embodiment, the light intensity distribution 54z along the Z direction of the illumination field 54 is set to a rectangular shape by the defocusing action of the wavefront dividing element 7e with respect to the X direction on the condenser optical system 8, and light along the X direction is set. The intensity distribution 54x is set in a trapezoidal shape. That is, in the present embodiment, unlike the conventional technique proposed in Non-Patent Document 1, it does not block the luminous flux that forms the required pupil intensity distribution on the illumination pupil immediately after the cylindrical micro fly's eye lens 7. In the illumination field 54, the pupil intensity distribution relating to the trapezoid hypotenuse of the light intensity distribution 54x (see the left side of FIG. 6) is not lost, and the pupil intensity associated with each point throughout the illumination field 54 is lost. The shape of the distribution becomes almost uniform.

  In this way, the pattern surface of the mask M and the transfer surface of the wafer W which are optically conjugate with the surface 9a of the opening of the mask blind 9 have a short side along the X direction and Y as in the illumination field 54. A rectangular illumination region (projection region) having a long side along the direction (corresponding to the Z direction in the mask blind 9) is formed. Similar to the illumination field 54, this rectangular illumination area has a trapezoidal light intensity distribution along the X direction, a rectangular light intensity distribution along the Y direction, and a pupil for each point. The shape of the intensity distribution is almost uniform.

  As described above, in the illumination optical system (2 to 10) of the present embodiment, an illumination region having a trapezoidal light intensity distribution along the X direction and a substantially uniform pupil intensity distribution regarding each point ( A projection region) can be formed on the mask M (and thus the wafer W). Therefore, in the exposure apparatus (2 to WS) of the present embodiment, illumination optics that has a trapezoidal light intensity distribution along the X direction and forms an illumination region in which the shape of the pupil intensity distribution for each point is substantially uniform. The system (2 to 10) can be used to accurately transfer the pattern of the mask M onto the wafer W under good illumination conditions.

  In the above-described embodiment, the rear focal position 7ex in the X direction of the wavefront dividing element 7e is shifted to the front side with respect to the front focal position 8a of the condenser optical system 8. However, the present invention is not limited to this. Even if the rear focal position 7ex is displaced rearward (mask side) with respect to the front focal position 8a, the same effect as in the above-described embodiment can be obtained.

  In the above-described embodiment, the rear focal position 7ez in the Z direction of the wavefront dividing element 7e and the front focal position 8a of the condenser optical system 8 are substantially matched. However, the present invention is not limited to this, and the rear focal position 7ez is positioned forward or rearward with respect to the front focal position 8a by a distance that is somewhat smaller than the positional shift distance dx of the rear focal position 7ex with respect to the front focal position 8a. Even if they are shifted, the same effect as in the above-described embodiment can be obtained.

  In general, according to the present invention, the first rear focal position (corresponding to 7ex) of the wavefront splitting element in the first direction (corresponding to the X direction in the above-described embodiment) in the plane orthogonal to the optical axis of the illumination optical system and the collection are collected. The first distance (corresponding to dx) along the optical axis with the front focal position (corresponding to 8a) of the optical optical system is the second rear side of the wavefront dividing element in the second direction (corresponding to the Z direction) in the plane. It is important that the distance is larger than the second distance (almost 0 in the above-described embodiment) along the optical axis between the focal position (corresponding to 7ez) and the front focal position of the condensing optical system.

  In the above-described embodiment, the first fly eye member (first optical member) 7a and the second fly eye member (second optical member) 7b constituting the cylindrical micro fly's eye lens 7 are adjacent to each other. However, the present invention is not limited to this, and some optical member (for example, a filter) may be interposed between the first optical member and the second optical member constituting the optical integrator.

  In the cylindrical micro fly's eye lens 7 according to the above-described embodiment, the plurality of cylindrical incident refracting surfaces 7aa of the first fly eye member 7a and the plurality of cylindrical incident refracting surfaces 7ba of the second fly eye member 7b are used. Are arranged along the X direction and have a refractive power in the X direction and no refractive power in the Z direction. The plurality of cylindrical exit refracting surfaces 7ab of the first fly's eye member 7a and the plurality of cylindrical exit refracting surfaces 7bb of the second fly's eye member 7b are arranged along the Z direction and are arranged in the Z direction. And has no refractive power in the X direction.

  However, the present invention is not limited to the configuration shown in FIG. 2, and various configurations are possible for the configuration of the optical integrator having a plurality of wavefront division elements arranged two-dimensionally in parallel. For example, a cylindrical micro fly's eye lens 17 having another form as shown in FIG. 7 can be used. As shown in FIG. 7, the cylindrical micro fly's eye lens 17 includes a first fly eye member 17a disposed on the light source side and a second fly eye member 17b disposed on the mask side.

  A plurality of cylindrical refractive surfaces (cylindrical lens groups) 17aa and 17ab arranged side by side in the X direction are formed at a pitch p1 on the light source side surface and the mask side surface of the first fly-eye member 17a. ing. A plurality of cylindrical refracting surfaces (cylindrical lens groups) 17ba and 17bb arranged side by side in the Z direction are respectively formed on the light source side surface and the mask side surface of the second fly-eye member 17b at a pitch p2 (p2>). p1).

  Focusing on the refractive action in the X direction of the cylindrical micro fly's eye lens 17 (that is, the refractive action in the XY plane), a group of parallel light beams incident along the optical axis AX are formed on the light source side of the first fly's eye member 17a. Corresponding in a group of refracting surfaces 17ab formed on the mask side of the first fly's eye member 17a after being wavefront divided by the refracting surface 17aa along the X direction at a pitch p1 and receiving a light condensing action on the refracting surface. The light is focused on the refracting surface.

  Focusing on the refractive action in the Z direction of the cylindrical micro fly's eye lens 17 (that is, the refractive action in the YZ plane), a group of parallel light beams incident along the optical axis AX are formed on the light source side of the second fly's eye member 17b. Corresponding in the group of refracting surfaces 17bb formed on the mask side of the second fly's eye member 17b after the wavefront is divided at the pitch p2 along the Z direction by the refracting surface 17ba of the second flyeye member 17b The light is focused on the refracting surface.

  Thus, the cylindrical micro fly's eye lens 17 is composed of the first fly eye member 17a and the second fly eye member 17b in which the cylindrical lens groups are arranged on both sides, and has a size of p1 in the X direction. It has a large number of rectangular microscopic refracting surfaces (unit wavefront dividing surfaces) having a size of p2 in the direction. In other words, the cylindrical micro fly's eye lens 17 is configured by two-dimensionally arranging a number of wavefront division elements having a rectangular cross section having an X-direction dimension of p1 and a Z-direction dimension of p2 along the XZ plane. It is an optical integrator.

  Each wavefront dividing element constituting the cylindrical micro fly's eye lens 17 has a rectangular wavefront dividing surface having a short side along the X direction and a long side along the Z direction. Therefore, even when the cylindrical micro fly's eye lens 17 is used, by applying the present invention in the same manner as in the case of the cylindrical micro fly's eye lens 7 of FIG.

  In the cylindrical micro fly's eye lens 17 of FIG. 7, the plurality of cylindrical incident refracting surfaces 17aa and the plurality of cylindrical exit refracting surfaces 17ab of the first fly's eye member 17a are arranged along the X direction, It has refractive power in the X direction and no refractive power in the Z direction. Further, the plurality of cylindrical incident refracting surfaces 17ba and the plurality of cylindrical exit refracting surfaces 17bb of the second fly's eye member 17b are arranged along the Z direction and have a refractive power in the Z direction. No refractive power in the X direction.

  Further, the present invention is not limited to the cylindrical micro fly's eye lens including a pair of optical members, and can be similarly applied to a wavefront division type optical integrator including a single optical member. In this case, the single optical member includes a plurality of curved (e.g., toric) incident refracting surfaces arranged in parallel two-dimensionally and a plurality of curved exit refracting surfaces arranged two-dimensionally in parallel. And have.

  In the above-described embodiment, the present invention is applied to an exposure apparatus that scans and exposes a pattern in each exposure area of a wafer according to a so-called step-and-scan method while moving the mask and the wafer relative to the projection optical system. The invention is applied. However, the present invention is not limited to this. For an exposure apparatus that sequentially exposes a pattern on a shot area of a wafer according to a so-called step-and-repeat method by performing batch exposure while controlling the wafer in two dimensions. Thus, the present invention can be applied as necessary.

  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. By using such a variable pattern forming apparatus, the influence on the synchronization accuracy can be minimized even if the pattern surface is placed vertically. 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. Note that a variable pattern forming apparatus may be used even when the pattern surface is placed horizontally. 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. In step S44, the exposure apparatus of the above-described embodiment performs pattern transfer using the wafer W coated with the photoresist as the photosensitive substrate, that is, the plate P.

  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 exposure apparatus of the above-described embodiment. In this pattern formation process, an exposure process for transferring the pattern to the photoresist layer using the exposure apparatus of the above-described embodiment and development of the plate P to which the pattern is transferred, that is, development of the photoresist layer on the glass substrate are performed. 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 step of 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, 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. WO 99/49504, A method of moving a stage holding a substrate to be exposed as disclosed in Japanese Patent Laid-Open No. 6-124873 in a liquid bath, or a predetermined depth on a stage as disclosed in Japanese Patent Laid-Open No. 10-303114. A method of forming a liquid tank and holding the substrate in the liquid tank 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, a so-called polarization illumination method disclosed in US Publication Nos. 2006/0170901 and 2007/0146676 can also be applied. Here, the teachings of US Patent Publication No. 2006/0170901 and US Patent Publication No. 2007/0146676 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 3 Diffractive optical element 4 Afocal lens 6 Zoom lens 7, 17 Cylindrical micro fly's eye lens 8 Condenser optical system 9 Mask blind 10 Imaging optical system M Mask PL Projection optical system AS Aperture stop W Wafer

Claims (12)

In the illumination optical system that illuminates the illuminated surface based on the light from the light source,
An optical integrator having a plurality of wavefront dividing elements arranged in an optical path between the light source and the irradiated surface and arranged two-dimensionally in parallel;
A condensing optical system disposed in an optical path between the optical integrator and the irradiated surface, and condensing a light beam that has passed through the wavefront splitting element,
The first distance along the optical axis between the first rear focal position of the wavefront splitting element and the front focal position of the condensing optical system in a first direction within a plane orthogonal to the optical axis of the illumination optical system is And a second distance along the optical axis between the second rear focal position of the wavefront splitting element and the front focal position of the condensing optical system in the second direction in the plane. Illumination optical system. 2. The illumination optical system according to claim 1, wherein the wavefront dividing element has a rectangular wavefront dividing surface having a short side along the first direction and a long side along the second direction. 3. The illumination optical system according to claim 1, wherein the second rear focal position of the wavefront dividing element and the front focal position of the condensing optical system coincide with the optical axis direction. . The optical integrator includes a single optical member,
The single optical member has a plurality of curved incident refracting surfaces arranged in parallel two-dimensionally and a plurality of curved exit refracting surfaces arranged two-dimensionally in parallel. The illumination optical system according to any one of claims 1 to 3. The optical integrator includes a first optical member and a second optical member disposed in an optical path between the first optical member and the irradiated surface,
The first optical member has a plurality of cylindrical first incident refracting surfaces formed side by side in one direction and a plurality of cylindrical surface-shaped first exit refracting surfaces formed side by side in one direction. And
The second optical member includes a plurality of cylindrical second incident refracting surfaces formed side by side in one direction and a plurality of cylindrical second emission refracting surfaces formed side by side in one direction. The illumination optical system according to any one of claims 1 to 3, wherein The plurality of cylindrical first incident refractive surfaces and the plurality of cylindrical second incident refractive surfaces are arranged along the first direction, have a refractive power in the first direction, and No refractive power in the second direction,
The plurality of cylindrical surface-shaped first exit refracting surfaces and the plurality of cylindrical surface-shaped second exit refracting surfaces are arranged along the second direction, have a refractive power in the second direction, and 6. The illumination optical system according to claim 5, wherein there is no refractive power in the first direction. The plurality of cylindrical surface-shaped first incident refracting surfaces and the plurality of cylindrical surface-shaped first exit refracting surfaces are arranged along the first direction and have refractive power in the first direction, and No refractive power in the second direction,
The plurality of cylindrical second incident refracting surfaces and the plurality of cylindrical second refracting surfaces are arranged along the second direction and have refractive power in the second direction, and 6. The illumination optical system according to claim 5, wherein there is no refractive power in the first direction. The illumination optical system according to any one of claims 5 to 7, wherein the first optical member and the second optical member are adjacent to each other. An exposure apparatus comprising the illumination optical system according to claim 1 for illuminating a predetermined pattern, and exposing the predetermined pattern onto a photosensitive substrate. A projection optical system for forming an image of the predetermined pattern on the photosensitive substrate; and moving the predetermined pattern and the photosensitive substrate relative to the projection optical system along a scanning direction to The exposure apparatus according to claim 9, wherein the pattern is projected and exposed onto the photosensitive substrate. The exposure apparatus according to claim 10, wherein the first direction in the optical integrator corresponds to the scanning direction. An exposure step of exposing the predetermined pattern to the photosensitive substrate using the exposure apparatus according to any one of claims 9 to 11,
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.

Images