Beam transmission system, exposure device, and illumination optical system of the exposure device

The present invention allows more freely setting of the polarization direction of illumination light on an illumination surface of an exposure device. A beam transmission system (121) that transmits, to an exposure device (130), a linearly polarized optical beam (L) output from a free electron laser device (10) includes: an optical beam splitting unit (50) configured to split the optical beam (L) into a first optical beam (L1) and a second optical beam (L2); and a first polarization direction rotating unit (51) configured to rotate the linear polarization direction of the first optical beam (L1).

BACKGROUND

1. Technical Field

The present disclosure relates to an exposure device, an illumination optical system of the exposure device, and a system that transmits an exposure optical beam from a free electron laser device to the exposure device.

2. Related Art

Recently, rapid progress has been made in refinement of a transfer pattern for optical lithography in the semiconductor process along with refinement of the semiconductor process. Minute fabrication at 20 nm or smaller is requested for the next generation technology. The request for minute fabrication at 20 nm or smaller is expected to be met by developing, for example, an exposure device including a combination of an extreme ultraviolet (EUV) light generation device configured to generate extreme ultraviolet light having a wavelength of 13.5 nm and a reduced projection reflective optics.

Three kinds of disclosed EUV light generation devices are a laser produced plasma (LPP) device that uses plasma generated by irradiating a target material with pulse laser light, a discharge produced plasma (DPP) device that uses plasma generated by electrical discharging, and a free electron laser device that uses electrons output from an electron accelerator.

CITATION LIST

Patent Literature

Patent Literature 1: National Publication of International Patent Application No. 2015-525906

Patent Literature 2: National Publication of International Patent Application No. 2015-523720

Patent Literature 3: National Publication of International Patent Application No. 2012-533729

Patent Literature 4: Japanese Unexamined Patent Application Publication No. 2014-3290

Patent Literature 5: US Published Patent Application No. 2015/0323874

Patent Literature 6: US Published Patent Application No. 2015/0173163

SUMMARY

According to an aspect of the present disclosure, a beam transmission system that transmits, to an exposure device, a linearly polarized optical beam output from a free electron laser device, includes: an optical beam splitting unit configured to split the optical beam into a first optical beam and a second optical beam; and a first polarization direction rotating unit configured to rotate a linear polarization direction of the first optical beam.

According to another aspect of the present disclosure, a beam transmission system that transmits, to an exposure device, a linearly polarized optical beam output from a free electron laser device, includes: a first free electron laser device configured to output a first optical beam; a second free electron laser device configured to output a second optical beam; and a first polarization direction rotating unit configured to rotate a linear polarization direction of the first optical beam.

According to an aspect of the present disclosure, an illumination optical system of an exposure device that illuminates the illumination surface of the exposure device with the optical beam transmitted by the exposure device according to the aspect of the present disclosure or the beam transmission system according to the other aspect of the present disclosure, includes: a first field facet mirror irradiated with the first optical beam; a second field facet mirror irradiated with the second optical beam; and a pupil facet mirror irradiated with the first optical beam via the first field facet mirror and the second optical beam via the second field facet mirror.

EMBODIMENTS

1. Overall description of EUV exposure device and beam transmission system

2. Comparative example

2.1 Configuration of comparative example

2.2 Operation of comparative example

2.3 Problem of comparative example

3.1 Configuration of Embodiment 1

3.2 Operation of Embodiment 1

3.3 Effects of Embodiment 1

4.1 Configuration of Embodiment 2

4.2 Operation of Embodiment 2

4.3 Effects of Embodiment 2

5.1 Configuration of Embodiment 3

5.2 Operation of Embodiment 3

5.3 Effects of Embodiment 3

6.1 Configuration of Embodiment 4

6.2 Operation of Embodiment 4

6.3 Effects of Embodiment 4

7.1 Configuration of Embodiment 5

7.2 Operation of Embodiment 5

7.3 Effects of Embodiment 5

8. Modification 1 of optical beam splitting unit

8.1 Configuration of Modification 1 of optical beam splitting unit

8.2 Operation of Modification 1 of optical beam splitting unit

8.3 Effects of Modification 1 of optical beam splitting unit

9. Modification 2 of optical beam splitting unit

9.1 Configuration of Modification 2 of optical beam splitting unit

9.2 Operation of Modification 2 of optical beam splitting unit

10. Modification 1 of polarization direction rotating unit

10.1 Configuration of Modification 1 of polarization direction rotating unit

10.2 Operation of Modification 1 of polarization direction rotating unit

10.3 Effects of Modification 1 of polarization direction rotating unit

Embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

The embodiments described below are merely examples of the present disclosure, and do not limit the content of the present disclosure. Not all configurations and operations described in the embodiments are necessarily essential configurations and operations of the present disclosure. Any identical components are denoted by an identical reference sign, and duplicate description thereof will be omitted.

1. Overall Description of EUV Exposure Device and Beam Transmission System

FIG. 1schematically illustrates an EUV exposure device, and a beam transmission system that transmits an exposure optical beam from a free electron laser device to the EUV exposure device. Hereinafter, a free electron laser device is referred to as an FEL device.FIG. 1schematically illustrates side shapes of a beam transmission system21including an FEL device10, and an EUV exposure device30.

In the present disclosure, a Z direction is defined to be the traveling direction of an optical beam emitted from the FEL device10. An H direction is defined to be a direction parallel to a surface on which the FEL device10is placed and orthogonal to the Z direction. A V direction is defined to be a direction orthogonal to the Z direction and the H direction. The H direction is aligned with the horizontal direction and the V direction is aligned with the vertical direction when the FEL device10and the EUV exposure device30are used in a normal state.

As illustrated inFIG. 1, the FEL device10includes an undulator11configured to control the linear polarization direction of pulse laser light to be output. An optical beam L transmitted through the beam transmission system21according to the present embodiment is pulse laser light output from the FEL device10.

The beam transmission system21includes a chamber20, an opening22provided to the chamber20, a through-hole23provided to the chamber20, and a collector mirror24disposed in the chamber20.

The optical beam L emitted from the FEL device10is incident in the chamber20through the opening22. The opening22is desirably sealed through, for example, an0ring or welded to an output unit of the FEL device10. The collector mirror24is, for example, an off-axis parabolic mirror. The collector mirror24is disposed such that the optical beam L emitted from the FEL device10is incident on the collector mirror24at a predetermined incident angle. The collector mirror24is disposed such that the incident optical beam L is collected at an intermediate focus (IF)25and then is incident in the EUV exposure device30. The above-described intermediate focus is referred to as the IF in the following description and the drawings.

The optical beam L travels out of the chamber20through the through-hole23. The through-hole23is desirably sealed to an optical beam input unit of the EUV exposure device30by a seal member (not illustrated). Any gas in the chamber20is desirably discharged by a discharge device (not illustrated) and maintained in a highly vacuum state so that attenuation of the optical beam L is reduced.

The EUV exposure device30includes an illumination optical system31, a projection optical system32, a reticle33, a wafer34, and a housing39.

The illumination optical system31includes a field facet mirror (FFM)35and a pupil facet mirror (PFM)36. In the following description and the drawings, a field facet mirror is referred to as an FFM, and a pupil facet mirror is referred to as a PFM. The FFM35and the PFM36are disposed to divide the optical beam L into a plurality of optical beams L each to be formed into a plurality of slits on the reticle33as an illumination surface so that the reticle33is illuminated with the slits. The FFM35and the PFM36are disposed such that the optical beams L have predetermined angle distribution relative to the reticle33. In addition, the FFM35and the PFM36are disposed such that all slits substantially overlap with each other on the reticle33.

The projection optical system32includes a concave mirror37and a concave mirror38. The concave mirror37and the concave mirror38are disposed to project and form, on the wafer34, an image of the reticle33being illuminated.

The projection optical system32is a combination of a plurality of mirrors, and may include larger numbers of concave mirrors and convex mirrors.

The EUV exposure device30includes a scanning mechanism (not illustrated) configured to synchronously scan the reticle33and the wafer34relative to the illumination optical system31and the projection optical system32.

The following describes the illumination optical system31in detail with reference toFIG. 2. The illumination optical system31includes the FFM35and the PFM36. The FFM35and the PFM36are what is called micro electro mechanical systems (MEMS) produced by using, for example, a silicon substrate.

The FFM35includes a plurality of facets (field facets)35a. Each facet35ais, for example, a minute mirror having a concave surface in an arc shape. Each slit with which the reticle33is irradiated has the shape of the facet35aas a minute mirror. Each facet35ais coupled with an actuator (not illustrated) configured to change the angle of the facet35aby, for example, electrostatic force.

The PFM36includes a plurality of facets (pupil facets)36a. Each facet36ais, for example, a minute mirror having a concave surface in a circular shape. Each facet36ais coupled with an actuator (not illustrated) configured to change the angle of the facet36aby, for example, electrostatic force.

Each facet35aof the FFM35forms an image at the IF25onto the corresponding one of the facets36aof the PFM36. The PFM36is disposed to form the image of the corresponding facet35areflected on each facet36aonto the reticle33in an overlapping manner.

The angles of the facets35aof the FFM35and the facets36aof the PFM36are individually set by an exposure device control unit60controlling drive of the actuators.

In the configuration described above with reference toFIG. 1, an optical beam L that is pulse laser light output from the FEL device10is incident in the chamber20. The optical beam L is incident on the collector mirror24at a predetermined angle and reflected. The reflected optical beam L is collected at the IF25. The collected optical beam L is incident in the EUV exposure device30through the through-hole23of the chamber20.

The optical beam L incident in the EUV exposure device30is formed into a scanning slit shape on the reticle33through the illumination optical system31. All optical beams L formed in the scanning slit shape are incident on the reticle33in a substantially overlapping manner. InFIG. 2, a resulting sectional shape of the optical beams L in the slit shape is denoted by Ls. The optical beams L each thus formed in the slit shape by the FFM35are converted to have predetermined angle distribution relative to the reticle33and incident on the reticle33at uniform illuminance through the PFM36.

The optical beams L incident on the reticle33are reflected on the reticle33and incident on the wafer34through the projection optical system32. Accordingly, an image of an illuminated part of the reticle33is transferred and formed onto a photoresist on the wafer34.

The reticle33and the wafer34are synchronously scanned relative to the illumination optical system31and the projection optical system32by the above-described scanning mechanism, and accordingly, the entire image of the reticle33is transferred and formed onto the photoresist on the wafer34. The speed of scanning the reticle33and the speed of scanning the wafer34are set to have a ratio in accordance with the magnification of the projection optical system32.

The following describes operation of the FFM35and the PFM36of the illumination optical system31with reference toFIG. 2. The exposure device control unit60determines an optimum shape of illumination light for a pattern of the reticle33. Typically, a plurality of reticles33are sequentially replaced and used at exposure of each wafer34, and the optimum shape of illumination light is determined for each reticle33. The exposure device control unit60controls the angle of each facet35aof the FFM35and the angle of each facet36aof the PFM36to obtain the determined shape of illumination light. This angle control is performed by controlling drive of the actuators coupled with the facets35aand36aas described above.

Examples of the shape of illumination light described above will be described with reference toFIGS. 3 to 5.FIGS. 3 to 5each schematically illustrate the shape of illumination light with the PFM36. InFIGS. 3 to 5, a large circle represents the PFM36, and24small circles illustrated in the large circle represent the facets36aof the PFM36. Each white circle representing one of the24facets36aindicates a state in which the angle of the corresponding facet35aof the FFM35is set so that an optical beam L divided at the facet35aof the FFM35is incident on the facet36a.

Each hatched facet36aindicates a state in which no optical beam L divided at the corresponding facet35aof the FFM35is incident on the facet36a. The reticle33is illuminated with the optical beams L at angle distribution in accordance with the disposition pattern of the facets36arepresented by white circles.

For example, as illustrated inFIG. 3, the reticle33is illuminated with an optical beam L reflected on a plurality of facets36acontinuous with each other in a schematically circular ring. In this case, the optical beam L spreading from the IF25illustrated inFIG. 2is incident and reflected on the plurality of facets35aof the FFM35. Accordingly, the optical beam L is divided at the plurality of facets35aand emitted from the FFM35. These divided optical beams L are incident on, among the facets36aof the PFM36, those continuous with each other in the schematically circular ring.

The reticle33is illuminated with the divided optical beams L reflected on the plurality of facets36a. The optical beams L on the reticle33form images of the arc-shaped facets35aof the FFM35in a substantially overlapping manner. Accordingly, the reticle33is illuminated at uniform illuminance through the arc shape as a slit. The reticle33is illuminated at angle distribution shaped in the schematically circular ring.

Alternatively, when the angles of the facets35aand36aare set so that a pattern illustrated inFIG. 4is obtained, the reticle33is illuminated at angle distribution of illumination light in a bipolar shape of divisions on the right and left sides. In addition, when the angles of the facets35aand36aare set so that a pattern illustrated inFIG. 5is obtained, the reticle33is illuminated at angle distribution of illumination light in a bipolar shape of divisions on the upper and lower sides.

2. Comparative Example

2.1Configuration of Comparative Example

FIG. 6is a schematic view illustrating the beam transmission system21according to a comparative example for the present invention. Similarly to the configuration illustrated inFIG. 1, a single optical beam L is output from the FEL device10in the configuration illustrated inFIG. 6. The optical beam L is linearly polarized in one direction indicated with Arrow P inFIG. 6.

2.2 Operation of the Comparative Example

Similarly to the configuration illustrated inFIG. 1, an optical beam L is divided into a plurality of beams in the configuration according to the comparative example. Then, the reticle33is illuminated with the divided optical beams L. The optical beams L incident on the reticle33are linearly polarized in the same direction.

2.3 Problem of the Comparative Example

In an EUV exposure device, as described above, the resolving power of a projection optical system is desired to be increased to meet the request for minute fabrication. The request can be satisfied by increasing the numerical aperture (NA) of the projection optical system. However, when the NA of the projection optical system is increased to, for example, 0.5 or larger, an imaging optical beam is incident on a resist on a wafer at such a large angle that the polarization of illumination light has measurable influence. For example, when line and space at 1:1 with a half pitch of 10 nm or smaller is imaged with extreme ultraviolet light having a wavelength of 13.5 nm through p polarization, the contrast of an optical image decreases by 20% or more. To prevent this contrast decrease, not only the shape of illumination light but also the linear polarization direction thereof need to be controlled in accordance with the pattern of a reticle.

However, in the configuration illustrated inFIG. 6according to the comparative example, the linear polarization direction of illumination light is fixed to the one direction in accordance with the linear polarization direction of the optical beam L when emitted from the FEL device10. Thus, with the configuration according to the comparative example, it is difficult to set the linear polarization direction of illumination light to be a preferable direction in accordance with the pattern of a reticle.

The above-described problem is more specifically described below.FIGS. 7, 8, and 9illustrate the linear polarization direction of illumination light set in the configuration illustrated inFIG. 6according to the comparative example when the illumination light has the above-described shapes illustrated inFIGS. 3, 4, and 5, respectively. InFIGS. 7, 8, and 9, the linear polarization direction is indicated by an arrow illustrated in each facet36a. X and Y directions are orthogonal to each other in a plane in which the facets36aare arranged.

The following describes a case in which, as illustrated inFIG. 7, the reticle33is illuminated with optical beams L reflected on a plurality of facets36acontinuous with each other in a schematically circular ring shape. In this case, the linear polarization direction is only in the Y direction, which is determined in accordance with the linear polarization direction of the optical beam L when emitted from the FEL device10.

To obtain such a shape of illumination light, preferable polarization illumination is known to be polarization illumination in a circumferential direction. Specifically, the linear polarization direction is set to be a direction along a schematic circumference to obtain the shape of illumination light in a schematically circular ring shape or a schematically circular shape. Thus, it is desirable that linear polarization directions as illustrated inFIG. 10are set for the illumination light shape illustrated inFIG. 7. However, the configuration illustrated inFIG. 6according to the comparative example has no function to individually set such linear polarization directions of optical beams incident on the PFM36, and thus has difficulties in polarization direction control.

The following describes a case in which the reticle33is illuminated with illumination light having the bipolar shape of divisions on the right and left sides as illustrated inFIG. 8. This illumination light shape is achieved by setting, in the illumination light shape illustrated inFIG. 7, the angles of four facets35aand the angles of four facets36aas illustrated with four long arrows between the facets36ainFIG. 8. In this case, too, the linear polarization direction is in the Y direction, which is determined in accordance with the linear polarization direction of the optical beam L when emitted from the FEL device10, thereby achieving illumination in a desired circumferential direction at least.

The following describes another case in which the reticle33is illuminated with illumination light having the bipolar shape of divisions on the upper and lower sides as illustrated inFIG. 9. This illumination light shape is achieved by setting, in the illumination light shape illustrated inFIG. 7, the angles of four facets35aand the angles of four facets36aas illustrated with four long arrows between the facets36ainFIG. 9. In this case, too, the linear polarization direction is in the Y direction, which is determined in accordance with the linear polarization direction of the optical beam L when emitted from the FEL device10.

In a case of an illumination light shape as illustrated inFIG. 9, it is desirable to set all linear polarization directions to be in the X direction as illustrated inFIG. 11, depending on the pattern of the reticle33, so that illumination is achieved in a desired circumferential direction. However, such setting of linear polarization directions is difficult to achieve with the configuration illustrated inFIG. 6according to the comparative example.

3.1 Configuration of Embodiment 1

FIG. 12is a partially broken side view schematically illustrating the configuration of a beam transmission system121and an EUV exposure device130according to Embodiment 1. The EUV exposure device130includes an illumination optical system according to the present invention. In the configuration illustrated inFIG. 12, any component identical to that illustrated inFIGS. 1 and 6is denoted by an identical reference sign, and duplicate description thereof will be omitted.

The following describes, in the configuration according to Embodiment 1, any part different from the configuration illustrated inFIGS. 1 and 6. In Embodiment 1, any configuration other than the difference described below is basically same as the configuration illustrated inFIGS. 1 and 6.

The beam transmission system121according to the present embodiment transmits, to the EUV exposure device130, an optical beam L emitted from the FEL device10. The beam transmission system121includes the FEL device10, the chamber20, and a beam transmission control unit61. The chamber20is provided with a first through-hole123and a second through-hole223. A first collector mirror124, a second collector mirror224, an optical beam splitting unit50, a first polarization direction rotating unit51, and a second polarization direction rotating unit52are disposed in the chamber20.

The optical beam splitting unit50splits, into a first optical beam L1and a second optical beam L2, the optical beam L output from the FEL device10and incident in the chamber20. A detailed configuration of the optical beam splitting unit50will be described later in detail.

The first polarization direction rotating unit51is disposed on the optical path of the first optical beam L1to rotate the linear polarization direction of the first optical beam L1. The second polarization direction rotating unit52is disposed on the optical path of the second optical beam L2to rotate the linear polarization direction of the second optical beam L2.

The first collector mirror124collects the first optical beam L1having passed through the first polarization direction rotating unit51. The first collector mirror124is disposed such that an IF (first IF)125of the collected first optical beam L1substantially coincides with the first through-hole123. The second collector mirror224collects the second optical beam L2having passed through the second polarization direction rotating unit52. The second collector mirror224is disposed such that an IF (second IF)225of the collected second optical beam L2substantially coincides with the second through-hole223.

The beam transmission control unit61controls operation of the first polarization direction rotating unit51and the second polarization direction rotating unit52based on information related to the reticle33, which is transmitted from the exposure device control unit60.

An FEL control unit62is provided to control operation of the FEL device10. The FEL control unit62controls operation of the FEL device10based on a control signal transmitted from the exposure device control unit60. When controlled in this manner, the FEL device10outputs an optical beam L that is pulse laser light at a predetermined timing.

The EUV exposure device130includes a first FFM135and a second FFM235in the illumination optical system31illustrated inFIG. 1. The first FFM135and the second FFM235each have a configuration basically same as that of the FFM35illustrated inFIGS. 1 and 6. The EUV exposure device130also includes a PFM136in the illumination optical system31illustrated inFIG. 1. The PFM136has a function same as that of the PFM36illustrated inFIGS. 1 and 6, but is not completely identical to the PFM36because the PFM136corresponds to the two FFMs. InFIG. 12, each facet (pupil facet) of the PFM136is denoted by136a.

The exposure device control unit60controls the angles of the facets35a(not illustrated inFIG. 12; Refer toFIG. 2) included in the first FFM135and the second FFM235, and the angle of the facets136aincluded in the PFM136. This facet angle control is basically same as the control of the angles of the facets of the FFM35and the PFM36described with reference toFIG. 2.

The optical relation on imaging and the like among the first FFM135, the PFM136, and the reticle33, and the optical relation on imaging and the like among the second FFM235, the PFM136, and the reticle33are basically same as the optical relation among the FFM35, the PFM36, and the reticle33described with reference toFIG. 2.

The following describes a specific configuration of the optical beam splitting unit50with reference toFIG. 13. In the present embodiment, the optical beam splitting unit50includes an oblique incidence high reflection mirror50M. The oblique incidence high reflection mirror50M is formed by using a substrate made of, for example, SiC or AlSi alloy. The oblique incidence high reflection mirror50M is disposed obliquely relative to the traveling direction of the optical beam L output from the FEL device10so that only substantially half of the optical beam L, in other words, the lower half inFIG. 13is reflected. Accordingly, the optical beam L is split into a reflected component as the first optical beam L1and a non-reflected component as the second optical beam L2.

An incident angle θ of the optical beam L relative to the oblique incidence high reflection mirror50M is preferably a value in the range of 80°≤θ<90°, more preferably a value in the range of 87°≤θ<89.7°.

The oblique incidence high reflection mirror SOM is likely to be heated to high temperature when irradiated with the optical beam L, and thus is desirably used while being cooled by flowing cooling water.

When the oblique incidence high reflection mirror50M as described above is used, the first optical beam L1and the second optical beam L2after the splitting proceed while being angled relative to each other. However,FIG. 12schematically illustrates a state in which the first optical beam L1and the second optical beam L2proceed in directions parallel to each other.

The following describes specific configurations of the polarization direction rotating units51and52with reference toFIGS. 14 to 16. The polarization direction rotating units51and52have configurations identical to each other, and thus the following description will be made on the polarization direction rotating unit through which the first optical beam L1passes.FIGS. 14 and 15illustrate a side view and a front view of the polarization direction rotating unit, respectively.FIG. 16is a front view illustrating the polarization direction rotating unit in a state different from that illustrated inFIG. 15.

The polarization direction rotating unit includes a tilt stage70and a rotation member74rotatably held by the tilt stage70. The rotation member74is shaped in a cylinder, part of which is removed, and is held rotatably about the axis of the cylinder by the tilt stage70. A plate75is fixed to the rotation member74, and a first mirror holder76and a second mirror holder77are fixed to the plate75.

The first mirror holder76includes two surfaces tilted relative to a direction in which the first optical beam L1proceeds. Among these tilted surfaces, the tilted surface on the back side in the traveling direction of the first optical beam L1holds a first high reflection mirror71, and the tilted surface on the front side in the traveling direction of the first optical beam L1holds a third high reflection mirror73. The second mirror holder77holds a second high reflection mirror72facing to the first high reflection mirror71and the third high reflection mirror73. A motor78configured to rotate the rotation member74by a desired angle is attached to the tilt stage70. Drive of the motor78is controlled by the beam transmission control unit61illustrated inFIG. 12.

The polarization direction rotating unit having the above-described configuration is disposed such that the first optical beam L1proceeds on the rotation center of the rotation member74and is incident on the first high reflection mirror71. The incident first optical beam L1is sequentially reflected on the first high reflection mirror71, the second high reflection mirror72, and the third high reflection mirror73.

3.2 Operation of Embodiment 1

In the configuration illustrated inFIG. 12, the FEL device10outputs an optical beam L that is pulse laser light. The optical beam L is linearly polarized by the undulator11. The optical beam L is incident in the chamber20through the opening22. The optical beam splitting unit50splits the optical beam L into a first optical beam L1and a second optical beam L2. The first optical beam L1is incident on the first polarization direction rotating unit51. The second optical beam L2is incident on the second polarization direction rotating unit52.

For example, the first polarization direction rotating unit51transmits the first optical beam L1without rotating the linear polarization direction of the incident first optical beam L1. The first optical beam L1having passed through the first polarization direction rotating unit51are reflected on the first collector mirror124. The reflected first optical beam L1is emitted out of the chamber20through the first through-hole123, collected at the first IF125, and then incident in the EUV exposure device130.

For example, the second polarization direction rotating unit52rotates the linear polarization direction of the incident second optical beam L2by 90° and transmits the second optical beam L2. The second optical beam L2having passed through the second polarization direction rotating unit52is reflected on the second collector mirror224. The reflected second optical beam L2is emitted out of the chamber20through the second through-hole223, collected at the second IF225, and then incident in the EUV exposure device130.

InFIG. 12, the linear polarization directions of the first optical beam L1and the second optical beam L2, which are parallel to the sheet ofFIG. 12are illustrated with Arrows P. The linear polarization directions thereof perpendicular to the sheet ofFIG. 12are illustrated with Points Q. As illustrated inFIG. 12, the linear polarization direction of the second optical beam L2having passed through the second polarization direction rotating unit52is rotated by 90° relative to the linear polarization direction of the first optical beam L1having passed through the first polarization direction rotating unit51.

The following describes the rotation of the second optical beam L2in detail. A rotation angle φ of the rotation member74relative to the tilt stage70illustrated inFIGS. 15 and 16is defined to be 0° in the state illustrated inFIG. 15. In the state illustrated inFIG. 15, the linear polarization direction of the first optical beam L1before being incident on the first high reflection mirror71is maintained intact after reflection on the third high reflection mirror73. In other words, the linear polarization direction of the optical beam L1is not rotated when the rotation angle φ is 0°.

When the rotation member74is rotated by the rotation angle φ=45°, the state illustrated inFIG. 16is obtained. In this case, the linear polarization direction of the first optical beam L1reflected on the third high reflection mirror73is rotated by 90° relative to the linear polarization direction of the first optical beam L1before being incident on the first high reflection mirror71.

The first optical beam L1incident in the EUV exposure device130is sequentially reflected on the first FFM135and the PFM136and then incident on the reticle33. Refer toFIG. 1since the reticle33is not illustrated inFIG. 12. The second optical beam L2incident in the EUV exposure device130is sequentially reflected on the second FFM235and the PFM136and then incident on the reticle33.

The first FFM135, the second FFM235, the PFM136, and the reticle33have such an optical position relation that the relation of the linear polarization direction between the first optical beam L1incident on the first FFM135and the second optical beam L2incident on the second FFM235is maintained intact on the reticle33.

As described above, the shapes of the optical beams L1and L2incident on the reticle33are controlled by controlling the angles of the facets of the first FFM135, the second FFM235, and the PFM136for each reticle33.

As described above, an image of the reticle33is transferred and formed onto a photoresist on the wafer34by the optical beams L1and L2reflected on the reticle33, and the entire surface image of the reticle33is transferred and formed onto the photoresist by scanning the reticle33and the wafer34.

In the above-described example, the linear polarization direction of the first optical beam L1is not rotated at the first polarization direction rotating unit51, the linear polarization direction of the second optical beam L2is rotated by 90° at the second polarization direction rotating unit52. However, the rotation control of the linear polarization direction is not limited thereto. For example, both of the linear polarization directions of the first optical beam L1and the second optical beam L2may be rotated by 90°, or none of the linear polarization directions of the first optical beam L1and the second optical beam L2may be rotated. In addition, the angle by which each linear polarization direction is rotated may be any angle other than 90°.

Such rotation control of the linear polarization direction is performed by the beam transmission control unit61controlling operation of the first polarization direction rotating unit51and the second polarization direction rotating unit52based on an instruction output from the exposure device control unit60for each sequentially replaced reticle33.

When the linear polarization direction of one of the first optical beam L1and the second optical beam L2is rotated by 90°, the two linear polarization directions on the reticle33are different from each other by 90°. The two linear polarization directions on the reticle33can be set to be different from each other by any angle other than 90° by rotating the linear polarization direction of one of the first optical beam L1and the second optical beam L2by any angle other than 90°. However, the pattern of the reticle33typically includes a longitudinal line and a transverse line orthogonal to each other. Thus, in most cases of setting the two linear polarization directions on the reticle33, the two linear polarization directions need to be set to have an angle of 90° relative to each other. For this reason, when the polarization angle between the first optical beam L1and the second optical beam L2on the reticle33can be set to only one value in addition to 0°, which corresponds to an identical direction, the angle is preferably set to be 90°.

3.3 Effects of Embodiment 1

As described above, since the optical beam splitting unit50, the first polarization direction rotating unit51, and the second polarization direction rotating unit52are provided in the present embodiment, one or both of the polarization directions of the first optical beam L1and the second optical beam L2can be freely changed. Accordingly, the two linear polarization directions on the reticle33can be freely set.

The shape of illumination light incident on the reticle33can be freely set by controlling the angles of the facets of each of the first FFM135, the second FFM235, and the PFM136.

With the above-described configuration, for example, the shape and linear polarization pattern of illumination light can be set as illustrated inFIG. 10in the present embodiment. When the shape of illumination light is set as illustrated inFIGS. 9 and 11, the linear polarization pattern of illumination light can be set as illustrated inFIG. 9, or can be set as illustrated inFIG. 11, which is, however, not optimum. Thus, according to the present embodiment, the resolving power of the exposure device can be improved.

4.1 Configuration of Embodiment 2

FIG. 17is a partially broken side view schematically illustrating the configuration of a beam transmission system221and the EUV exposure device130according to Embodiment 2. In the configuration illustrated inFIG. 17, any component identical to that illustrated inFIG. 12is denoted by an identical reference sign, and duplicate description thereof will be omitted.

The beam transmission system221according to Embodiment 2 has a configuration different from that of the beam transmission system121according to Embodiment 1. Specifically, the beam transmission system221includes an optical pulse stretcher80disposed on the optical path of the optical beam L between the FEL device10and the optical beam splitting unit50.FIG. 18illustrates a detailed configuration of the optical pulse stretcher80. As illustrated inFIG. 18, the optical pulse stretcher80includes a reflective first grating85and a reflective second grating86. The first grating85and the second grating86have groove pitches substantially equal to each other.

The first grating85is disposed at a position at which the optical beam L is incident so that the optical beam L has an incident angle α and a diffraction angle β. The second grating86is disposed at a position at which the optical beam L reflected and diffracted on the first grating85is incident so that the incident angle of the optical beam L is substantially equal to β and the diffraction angle thereof is substantially equal to α. The incident and diffraction angles are obtained for the central wavelength of the optical beam L.

4.2 Operation of Embodiment 2

An optical beam L that is pulse laser light output from the FEL device10has a short pulse width of, for example, 0.1 to 0.2 ps (picosecond), and thus has a wide spectrum line width according to the uncertainty principle, thereby having extremely high energy per unit time. When the optical beam L is reflected and diffracted on the gratings85and86, the optical path of a long wavelength component of the optical beam L is shorter whereas the optical path of a short wavelength component of the optical beam L is longer because the diffraction angle differs between the long and short wavelength components. Accordingly, the pulse width of the optical beam L is stretched in accordance with the spectrum line width.

4.3 Effects of Embodiment 2

When the pulse width of the beam L is stretched as described above, the energy of the optical beam L, which is pulse laser light, per unit time decreases. This leads to prevention of damage, due to ablation by the optical beam L, on a film used on the reflection surface of an optical element at a stage later than the optical pulse stretcher80, and a resist on the wafer. Examples of the optical element include the polarization direction rotating units51and52, the collector mirrors124and224, and various optical elements in the EUV exposure device130.

5.1 Configuration of Embodiment 3

FIG. 19is a partially broken side view schematically illustrating the configuration of a beam transmission system321and the EUV exposure device130according to Embodiment 3. In the configuration illustrated inFIG. 19, any component identical to that illustrated inFIG. 12is denoted by an identical reference sign, and duplicate description thereof will be omitted.

The beam transmission system321according to Embodiment 3 has a configuration different from that of the beam transmission system121according to Embodiment 1. Specifically, the beam transmission system321includes a polarization direction rotating unit52only on the optical path of the second optical beam L2among the first optical beam L1and the second optical beam L2split by the optical beam splitting unit50. The polarization direction rotating unit52may be same as the second polarization direction rotating unit52used in the configuration illustrated inFIG. 12.

The beam transmission system321according to the present embodiment includes a first optical pulse stretcher81and a second optical pulse stretcher82disposed on the respective optical paths of the first optical beam L1and the second optical beam L2split by the optical beam splitting unit50. The optical pulse stretchers81and82may be same as the optical pulse stretcher80illustrated inFIG. 18.

The beam transmission system321according to the present embodiment includes an optical beam splitting unit90having a configuration different from that of the optical beam splitting unit50illustrated inFIGS. 12 and 17. The optical beam splitting unit90has a function to select the optical path of the optical beam L, in particular. The following describes the optical beam splitting unit90in detail with reference toFIGS. 20 and 21.

The optical beam splitting unit90includes a movable oblique incidence high reflection mirror90M. The movable oblique incidence high reflection mirror90M has a mirror configuration equivalent to that of the oblique incidence high reflection mirror50M illustrated inFIG. 13. In addition, the optical beam splitting unit90includes an actuator (not illustrated) configured to change the position of the movable oblique incidence high reflection mirror90M.

The movable oblique incidence high reflection mirror90M is driven by the actuator and set to any one of a first state illustrated with solid lines inFIG. 20, a second state illustrated with dashed lines inFIG. 20, and a third state illustrated inFIG. 21. In the first state, the optical beam L is fully reflected on the movable oblique incidence high reflection mirror90M disposed such that the entire optical beam L is incident on the movable oblique incidence high reflection mirror90M. In the second state, the movable oblique incidence high reflection mirror90M is retracted from the optical path of the optical beam L. In the third state, the optical beam L is partially reflected on the movable oblique incidence high reflection mirror90M disposed such that part of the optical beam L is incident on the movable oblique incidence high reflection mirror90M. Drive of the actuator may be manually controlled through a switch or automatically controlled by the beam transmission control unit61.

5.2 Operation of Embodiment 3

When the movable oblique incidence high reflection mirror90M is set to the first state, the optical beam L is all reflected and proceeds on the optical path of the first optical beam L1. When the movable oblique incidence high reflection mirror90M is set to the second state, the optical beam L all proceeds on the optical path of the second optical beam L2without being reflected on the movable oblique incidence high reflection mirror90M. When the movable oblique incidence high reflection mirror90M is set to the third state, the optical beam L is split into the first optical beam L1and the second optical beam L2. In this case, too, the first optical beam L1proceeds on the optical path of the first optical beam, and the second optical beam L2proceeds on the optical path of the second optical beam.

5.3 Effects of Embodiment 3

Since the beam transmission system321according to Embodiment 3 includes the single polarization direction rotating unit52, device simplification is achieved as compared to a configuration provided with two polarization direction rotating units.

According to Embodiment 3, it is difficult to individually and optionally change the linear polarization directions of the first optical beam L1and the second optical beam L2. However, as described above, the pattern of the reticle33typically includes a longitudinal line and a transverse line orthogonal to each other. With this configuration, no problem occurs to setting of the linear polarization directions, for example, when the fixed linear polarization direction of the first optical beam L1is set to be parallel to a direction in which the longitudinal line or the transverse line extends on the reticle33. Specifically, the linear polarization direction of the first optical beam L1can be set in this manner when set parallel or right-angled to a side of the reticle33. This is because the longitudinal line or the transverse line of the pattern of the reticle33typically extends in parallel to a side of the reticle33.

The linear polarization direction of the second optical beam L2rotated by the polarization direction rotating unit52may be set parallel or orthogonal to the fixed linear polarization direction of the first optical beam L1on the reticle33.

The optical path selection function of the optical beam splitting unit90enables selective setting of a state in which only one of the first optical beam L1and the second optical beam L2is transmitted to the EUV exposure device130and a state in which both of the optical beams L1and L2are transmitted to the EUV exposure device130.

6.1 Configuration of Embodiment 4

FIG. 22is a partially broken side view schematically illustrating the configuration of a beam transmission system421and the EUV exposure device130according to Embodiment 4. In the configuration illustrated inFIG. 22, any component identical to that illustrated inFIG. 12is denoted by an identical reference sign, and duplicate description thereof will be omitted.

The beam transmission system421according to Embodiment 4 has a configuration different from that of the beam transmission system121according to Embodiment 1. Specifically, the beam transmission system421does not include the optical beam splitting unit50.

In Embodiment 4, two FEL devices of a first FEL device110and a second FEL device210are provided. The first FEL device110outputs a first optical beam L1that is pulse laser light. The second FEL device210outputs a second optical beam L2that is pulse laser light. The second FEL device210is disposed such that the second optical beam L2output from the second FEL device210proceeds in parallel to the first optical beam L1output from the first FEL device110.

The first polarization direction rotating unit51configured to rotate the linear polarization direction of the first optical beam L1is disposed on the optical path of the first optical beam L1. The second polarization direction rotating unit52configured to rotate the linear polarization direction of the second optical beam L2is disposed on the optical path of the second optical beam L2.

In this configuration in which the first FEL device110and the second FEL device210are provided, too, only one of the linear polarization directions of the first optical beam L1and the second optical beam L2may be rotated as in the configuration illustrated inFIG. 19.

6.2 Operation of Embodiment 4

The linear polarization directions of the first optical beam L1and the second optical beam L2are rotated by the first polarization direction rotating unit51and the second polarization direction rotating unit52, respectively. The first optical beam L1and the second optical beam L2are used in the same manner as in the configuration illustrated inFIG. 12.

6.3 Effects of Embodiment 4

In the present embodiment, the two FEL devices110and210are provided, which eliminates the need to provide an optical beam splitting unit.

7.1 Configuration of Embodiment 5

FIG. 23is a partially broken side view schematically illustrating the configuration of a beam transmission system521and the EUV exposure device130according to Embodiment 5. In the configuration illustrated inFIG. 23, any component identical to that illustrated inFIG. 22is denoted by an identical reference sign, and duplicate description thereof will be omitted.

The beam transmission system521according to Embodiment 5 has a configuration different from that of the beam transmission system421according to Embodiment 4. Specifically, the beam transmission system521has the configuration of the beam transmission system421except for the first polarization direction rotating unit51and the second polarization direction rotating unit52.

7.2 Operation of Embodiment 5

The linear polarization direction of the first optical beam L1is set to be in a desired direction on the reticle33by controlling the undulator11of the first FEL device110. The linear polarization direction of the second optical beam L2is set to be in a desired direction on the reticle33by controlling the undulator11of the second FEL device210.

7.3 Effects of Embodiment 5

The two FEL devices110and210are provided in the present embodiment, which eliminates the need to provide an optical beam splitting unit. In addition, one or two polarization direction rotating units do not need to be provided.

8. Modification 1 of Optical Beam Splitting Unit

8.1 Configuration of Modification 1 of Optical Beam Splitting Unit

FIG. 24is a partially broken side view illustrating an optical beam splitting unit according to Modification 1, which is included in a beam transmission system according to the present invention. The optical beam splitting unit according to Modification 1 includes a wedge-shaped oblique incidence high reflection mirror120. Two reflection surfaces divided at a leading end of the wedge-shaped oblique incidence high reflection mirror120, which are upper and lower reflection surfaces inFIG. 24, are each coated with a metal film made of, for example, Au or Ru. The wedge-shaped oblique incidence high reflection mirror120is disposed such that an optical beam L is first incident on the sharp leading end side on the optical path of the optical beam L.

8.2 Operation of Modification 1 of Optical Beam Splitting Unit

The optical beam L first incident on the leading end side of the wedge-shaped oblique incidence high reflection mirror120is reflected on the upper and lower reflection surfaces of the wedge-shaped oblique incidence high reflection mirror120. The optical beams L thus reflected in two split directions proceeds as the first optical beam L1and the second optical beam L2, respectively.

8.3 Effects of Modification 1 of Optical Beam Splitting Unit

The configuration of the optical beam splitting unit is simplified by providing the wedge-shaped oblique incidence high reflection mirror120.

9. Modification 2 of Optical Beam Splitting Unit 9.1 Configuration of Modification 2 of Optical Beam Splitting Unit

FIGS. 25 and 26are a side view and a top view, respectively, illustrating an optical beam splitting unit according to Modification 2, which is included in a beam transmission system according to the present invention.

The optical beam splitting unit according to Modification 2 includes a grating140. The grating140includes a plurality of diffraction gratings fabricated to have grooves at a predetermined grating pitch and each having, for example, a rectangular section. These diffraction gratings are formed in such a groove depth that generation of the zeroth light of the optical beam L is prevented but the (+1)-th diffracted light and the (−1)-th diffracted light are both enhanced. The grating140has diffraction surface coated with a multi-layered film made of Mo and Si or a metal film made of, for example, Au or Ru. The grating140is disposed on the optical path of the optical beam L such that the optical beam L is incident on the diffraction surface.

9.2 Operation of Modification 2 of Optical Beam Splitting Unit

The optical beam L incident on the diffraction surface of the grating140is diffracted on the diffraction surface and split into the (+1)-th light and the (−1)-th light. The split optical beams L proceed as the first optical beam L1and the second optical beam L2, respectively.

10. Modification 1 of Polarization Direction Rotating Unit

10.1 Configuration of Modification 1 of Polarization Direction Rotating Unit

FIG. 27is a schematic perspective view illustrating a polarization direction rotating unit according to Modification 1, which is included in a beam transmission system according to the present invention.FIG. 28is a schematic perspective view illustrating Modification 1 in another state. States of the polarization direction rotating unit illustrated inFIGS. 27 and 28are referred to as a first state and a second state, respectively. InFIGS. 27 and 28, the first optical beam L1is incident on the polarization direction rotating unit.

The polarization direction rotating unit according to Modification 1 includes a first high reflection mirror201, a second high reflection mirror202, a third high reflection mirror203, a fourth high reflection mirror204, and a fifth high reflection mirror205. The polarization direction rotating unit also includes a first linear stage301on which the first high reflection mirror201is mounted and that changes the position of the first high reflection mirror201, and a second linear stage302on which the fifth high reflection mirror205is mounted and that changes the position of the fifth high reflection mirror205. The first linear stage301and the second linear stage302are included in mirror moving means in the present disclosure. The beam transmission control unit61controls operation of the first linear stage301and the second linear stage302.

The first high reflection mirror201is disposed to reflect the first optical beam L1in the V direction. The second high reflection mirror202is disposed to reflect the first optical beam L1in the H direction. The third high reflection mirror203is disposed to reflect the first optical beam L1in the Z direction. The V direction, the H direction, and the Z direction correspond to a first reflection direction, a second reflection direction, and a third reflection direction in the present disclosure.

10.2 Operation of Modification 1 of Polarization Direction Rotating Unit

In the first state of the polarization direction rotating unit illustrated inFIG. 27, the first optical beam L1is sequentially reflected on the first high reflection mirror201, the second high reflection mirror202, and the third high reflection mirror203. Specifically, in this state, the first linear stage301is located at a first position, and accordingly, the first high reflection mirror201is inserted into the optical path of the first optical beam L1. The second linear stage302is located at a first position, and accordingly, the fifth high reflection mirror205is removed from the optical path of the first optical beam L1. In this state, the first optical beam L1is reflected on the second high reflection mirror202, and accordingly, the linear polarization direction of the first optical beam L1is rotated by 90°.

In the second state of the polarization direction rotating unit illustrated inFIG. 28, the first optical beam L1is sequentially reflected on the fourth high reflection mirror204and the fifth high reflection mirror205. Specifically, in this state, the first linear stage301is located at a second position, and accordingly, the first high reflection mirror201is removed from the optical path of the first optical beam L1. The second linear stage302is located at a second position, and accordingly, the fifth high reflection mirror205is inserted into the optical path of the first optical beam L1. In this state, the linear polarization direction of the first optical beam L1is not rotated.

10.3 Effects of Modification 1 of Polarization Direction Rotating Unit

The above-described configuration enables selective setting of the state in which the linear polarization direction of the first optical beam L1is not rotated and the state in which the linear polarization direction of the first optical beam L1is rotated by 90°.

The above description is not intended to provide limitation but is merely exemplary. Thus, the embodiments of the present disclosure can be modified without departing from the scope of the accompanying claims, which is to be clearly understood by the skilled person in the art.

Any term used in the present specification and the accompanying claims should be understood as a “non-restrictive” term. For example, the term “include” or “included” should be understood as “the present invention is not limited to a component described as being included”. The term “have” should be understood as “the present invention is not limited to a component described as being had”. When used in the present specification and the accompanying claims, the indefinite article “a” should be understood as “at least one” or “one or more”.

REFERENCE SIGNS LIST

21,121,221,321,421,521Beam transmission system

30EUV exposure device

31Illumination optical system

32Projection optical system

35FFM: Field Facet Mirror

50Optical beam splitting unit

50M Oblique incidence high reflection mirror

51First polarization direction rotating unit

52Second polarization direction rotating unit

60Exposure device control unit

61Beam transmission control unit

62FEL control unit

71First high reflection mirror

73Third high reflection mirror

72Second high reflection mirror

76First mirror holder

77Second mirror holder

90Polarization direction rotating unit

90M Movable oblique incidence high reflection mirror

120Wedge-shaped oblique incidence high reflection mirror

125First IF

130EUV exposure device

201First high reflection mirror

202Second high reflection mirror

203Third high reflection mirror

204Fourth high reflection mirror

205Fifth high reflection mirror

225Second IF

301First linear stage

302Second linear stage

L Optical beam

Ls Sectional shape of optical beam

L1First optical beam

L2Second optical beam