JP2009099629A - Illumination optical device, exposure method and apparatus, and method of manufacturing electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an illumination optical device for always highly accurately controlling a plurality of polarized states. <P>SOLUTION: The illumination optical system ILS for illuminating a pattern surface of a mask M, includes: a PBS (polarization beam splitter) 4 which is arranged in an optical path of the illumination light and which selectively transmits linearly polarization having a polarization direction in a Z direction; a 1/2 wavelength plate 5 which is arranged in downstream of the PBS 4 and which changes the polarized state of illumination light to a state in which the light is linearly polarized in a direction in parallel with a Z-axis or an X-axis (a first polarized state) or a state in which the light is linearly polarized in a direction inclined by 45° relative to the Z-axis (a second polarized state); and a depolarizer 6 which is arranged in downstream of the 1/2 wavelength plate 5 and which changes the polarized state of illumination light ejected from the 1/2 wavelength plate 5. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an illumination optical apparatus that illuminates a surface to be irradiated with illumination light in a plurality of polarization states, an exposure technique using the illumination optical apparatus, and an electronic device manufacturing technique using the exposure technique.

  For example, in a lithography process for manufacturing an electronic device (including a microdevice) such as a semiconductor element or a liquid crystal display element, a pattern of a mask (reticle or photomask) is transferred to a wafer (or glass plate or the like) via a projection optical system. In order to transfer to each shot area, an exposure apparatus such as a batch exposure type projection exposure apparatus such as a stepper or a scanning exposure type projection exposure apparatus such as a scanning stepper is used. In these exposure apparatuses, the exposure wavelength is shortened in order to increase the resolution. Recently, an excimer laser light source such as a KrF excimer laser (wavelength 248 nm) or an ArF excimer laser (wavelength 193 nm) is used as an exposure light source. in use. In order to obtain a higher resolution, polarized illumination is also used in which the polarization state of illumination light is set to a predetermined linear polarization according to the pattern to be transferred. Since the excimer laser light source emits substantially linearly polarized laser light, it is suitable for polarized illumination.

Actually, depending on the pattern to be transferred, the illumination light may be set in a non-polarized state with a random polarization direction. Therefore, using an excimer laser light source as an exposure light source, polarized light including a rotatable half-wave plate and quarter-wave plate in an illumination optical system, and an optical member for setting a non-polarization state that can be inserted into and removed from the optical path. Proposal of an exposure apparatus that includes a control unit and controls the polarization state of the illumination light illuminated on the mask in various states by combining the rotation of the wave plate in the polarization control unit and the insertion / removal of the optical member. (For example, refer to Patent Document 1).
International Publication No. 2004/051717 Pamphlet

  The conventional polarization control unit is based on the premise that the polarization state of the laser light supplied from the excimer laser light source is a predetermined state, for example, linear polarization in a predetermined direction. However, in practice, the polarization direction of laser light emitted from a laser light source such as an excimer laser light source may fluctuate due to changes over time. In addition, when a light transmission optical system or the like is installed between the excimer laser light source and the polarization control unit, and the optical path to the polarization control unit is long, the laser light is transmitted between the excimer laser light source and the polarization control unit. There is also a possibility that the polarization state of the light beam slightly changes.

Thus, when the polarization state of the laser light incident on the polarization control unit changes from the state determined by design, the polarization state of the laser light (illumination light) emitted from the polarization control unit is changed from the target state. There is a risk that the resolution will be lowered.
The present invention has been made in view of such circumstances, and provides an illumination optical technique capable of always controlling the polarization state of illumination light with high accuracy, and an exposure technique and a device manufacturing technique using the illumination optical technique. The purpose is to do.

  An illumination optical device according to the present invention is an illumination optical device that illuminates a surface (M) to be illuminated with illumination light, and is arranged in the optical path of the illumination light and selectively transmits linearly polarized light having a predetermined polarization direction. A linearly polarized light extraction element (4) to be moved, and a first polarization state arranged downstream of the linearly polarized light extraction element to change the polarization state of the illumination light to the first polarization state (IL3) or the second polarization state (IL7). A polarization state variable element (5) and a second polarization state variable element that is arranged downstream of the first polarization state variable element and changes the polarization state of the illumination light emitted from the first polarization state variable element (6), and the second polarization state variable element changes the first polarization state of the illumination light to the third polarization state (IL4), and changes the second polarization state of the illumination light to the fourth state. It is variable to the polarization state (IL8).

  According to the illumination optical device of the present invention, even if the polarization state of the illumination light supplied from the light source slightly fluctuates due to a change over time or the like, the linearly polarized light that is polarized in the predetermined direction extracted by the linearly polarized light extraction element is the first. It is supplied to the polarization state variable element. In addition, light having a plurality of polarization states can be generated by the first and second polarization state variable elements using the linearly polarized light. Therefore, the polarization state can always be controlled with high accuracy.

Hereinafter, an exemplary embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a view showing a schematic configuration of the exposure apparatus of the present embodiment. In FIG. 1, the exposure apparatus includes an exposure light source 1, an illumination optical system ILS that illuminates a pattern surface (mask surface) of a mask M with exposure illumination light (exposure light) IL from the light source 1, and a mask. A mask stage (not shown) that positions M, a projection optical system PL that projects an image of the pattern of the mask M onto a wafer W (photosensitive substrate), and a wafer stage (not shown) that positions the wafer W The main control system 20 is a computer that controls the operation of the entire apparatus, and various drive systems. In FIG. 1, the Z axis is set along the normal direction of the mounting surface of the wafer W, the Y axis is perpendicular to the paper surface of FIG. 1 in the direction parallel to the paper surface of FIG. X axis is set in each direction.

The exposure apparatus shown in FIG. 1 includes an ArF excimer laser light source that supplies a substantially linearly polarized laser beam having a wavelength of 193 nm as the light source 1. As the light source 1, a KrF excimer laser light source that supplies laser light with a wavelength of 248 nm, an F ₂ laser light source that supplies laser light with a wavelength of 157 nm, or a mercury lamp that supplies bright lines such as i-line (365 nm) is used. Can do. When a mercury lamp is used, the light source 1 has a configuration including a mercury lamp, an elliptical mirror, and a collimator lens.

  Illumination light IL, which is a substantially parallel light beam emitted from the light source 1 in the Z direction and is substantially linearly polarized laser light, has an elongated rectangular cross section along the X direction, and has a beam matching unit (not shown). The light enters the beam expander 2 (shaping optical system) including the lenses 2a and 2b having refractive power in the pair of ZY planes. The cross section of the illumination light IL is expanded in the Y direction by the beam expander 2 and is shaped into a light beam having a predetermined rectangular cross section.

  Illumination light IL emitted from the beam expander 2 is reflected in the Y direction by a mirror 3 for bending an optical path, and then sequentially, a prism type polarization beam splitter (hereinafter referred to as PBS) 4 and an illumination optical system ILS. The light passes through a half-wave plate 5 rotatable around the optical axis AXI and a depolarizer 6 and enters one of diffractive optical elements (DOE) 7A, 7B, 7C, and the like. A polarization controller (detailed later) is configured including the PBS 4, the half-wave plate 5, and the depolarizer 6.

  In general, a diffractive optical element is formed by two-dimensionally forming a minute step having a pitch of the exposure wavelength on a glass substrate, and has an action of diffracting an incident beam at various desired angles. The diffractive optical element 7A is a divergent light beam forming element having a function of diffracting an incident rectangular parallel light beam to form a circular light beam in the far field. Further, the incident illumination light IL is diffracted, and two illumination areas decentered in the X direction and the Z direction (corresponding to the Y direction on the mask surface) approximately symmetrically with respect to the optical axis AXI in the far field. Diffractive optical elements 7B and 7C for dipole illumination having a function of forming an illumination field), diffractive optical elements for quadrupole illumination (not shown) for forming four eccentric illumination areas, and an annular illumination area Diffractive optical elements (not shown) for annular illumination, etc. are formed. These diffractive optical elements 7A to 7C and the like are held around the disk 8 as an example. Further, for example, the illumination control system 21 rotates the disk 8 by a drive unit 23 such as a rotary motor in accordance with a command for setting the illumination condition from the main control system 20, so that the diffractive optical according to the illumination condition The element is configured to be arranged on the optical path of the illumination light IL. In FIG. 1, a diffractive optical element 7A for normal illumination is set on the optical path of the illumination light IL.

  In FIG. 1, a light beam diffracted through the diffractive optical element 7A (or 7B, 7C, etc.) is a front group lens system 9a, a first prism 10a having a concave conical surface, and a second prism having a convex conical surface. The microlens array 11 as an optical integrator is illuminated through the axicon system 10 and the rear group lens system 9b. The front lens group 9a and the rear lens system 9b constitute a zoom lens (variable magnification optical system) 9 that can continuously change the focal length within a predetermined range. The zoom lens 9 optically couples the exit surface of the diffractive optical element 7A and the rear focal plane of the microlens array 11 optically in a conjugate manner. In other words, the zoom lens 9 substantially connects the exit surface of the diffractive optical element 7A and the entrance surface of the microlens array 11 in a Fourier transform relationship.

  Illumination light IL emitted from the diffractive optical element 7A or the like has an illumination area (an illumination field) having a predetermined shape such as a circular shape or a bipolar shape on the rear focal plane of the zoom lens 9 (and hence the incident surface of the microlens array 11). Form. As described above, the diffractive optical apparatus 7A and the like and the zoom lens 9 constitute an illumination area forming unit. The overall size of the illumination area changes depending on the focal length of the zoom lens 9. The focal length of the zoom lens 9 is desired by driving the lens systems 9a and 9b of the zoom lens 9 along the optical axis AXI by driving units 24 and 26 including a slide mechanism, for example, based on commands of the illumination control system 21, respectively. Is controlled to the value of

  In the axicon system 10, the conical surfaces of the first prism 10 a and the second prism 10 b are arranged to face each other, and the second prism 10 b includes, for example, a drive unit including a slide mechanism based on a command from the illumination control system 21. 25 along the optical axis AXI. Thus, by controlling the distance along the optical axis AXI of the prisms 10a and 10b, the position of the light beam emitted from the diffractive optical element 7A and the like in the radial direction with respect to the optical axis AXI on the incident surface of the microlens array 11 Can be controlled. Therefore, for example, when using the bipolar illumination areas 32A and 32B in FIG. 3B described later, the distance between the prisms 10a and 10b of the axicon system 10 in FIG. 1 is controlled to control the illumination areas 32A and 32B. The distance from the central optical axis AXI can be controlled. On the other hand, by controlling the focal length of the zoom lens 9, the individual sizes of the illumination areas 32A and 32B can be controlled.

  The microlens array 11 is an optical element composed of a large number of microlenses having positive refractive power arranged densely in the vertical and horizontal directions. Each microlens constituting the microlens array 11 has a rectangular cross section 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). In general, a microlens array is configured by forming a group of microlenses by performing an etching process on a parallel flat glass plate, for example. Each microlens constituting the microlens array 11 is smaller than each lens element constituting an ordinary fly-eye lens. In FIG. 1, for the sake of clarity, the number of microlenses constituting the microlens array 11 is shown to be much smaller than actual.

  Therefore, the light beam incident on the microlens array 11 is two-dimensionally divided by a large number of microlenses, and a large number of light sources are formed on the rear focal plane of each microlens. Thus, an illumination area (for example, a circular area or FIG. 3) formed by the incident light flux on the microlens array 11 is formed on the pupil plane (illumination pupil plane) 12 of the illumination optical system ILS which is the rear focal plane of the microlens array 11. A secondary light source having substantially the same light intensity distribution as the two-pole illumination areas 32A and 32B in (B), that is, a secondary light source composed of a substantial surface light source centered on the optical axis AXI is formed.

  In FIG. 1, the illumination light IL from the secondary light source formed on the rear focal plane (illumination pupil plane 12) of the microlens array 11 is an aperture that defines the contour of the light intensity distribution of the illumination area as necessary. After being restricted through a diaphragm (not shown), transfer is performed through a first relay lens 13, a mask blind 14 (field diaphragm), a second relay lens 15, a mirror 16 for bending an optical path, and a condenser optical system 17. The mask M on which the pattern for use is formed is illuminated in a superimposed manner. The illumination optical system ILS includes an optical member from the beam expander 2 to the polarization controller, and an optical member from the diffractive optical elements 7A to 7C to the condenser optical system 17.

  The illumination light IL having passed through the pattern of the mask M forms an image of the mask pattern on the wafer W coated with a resist (photosensitive material) via the projection optical system PL. In this way, by performing batch exposure or scanning exposure while driving and controlling the wafer W two-dimensionally in a plane (XY plane) orthogonal to the optical axis (parallel to the Z axis) of the projection optical system PL, each wafer W The pattern of the mask M is sequentially exposed in the shot area.

  In the batch exposure, the mask pattern is batch exposed to each shot area of the wafer in accordance with a so-called step-and-repeat method. In this case, the shape of the illumination area on the mask M is a rectangular shape close to a square, and the cross-sectional shape of each microlens of the microlens array 11 is also a rectangular shape close to a square. On the other hand, in scanning exposure, a mask pattern is exposed to each shot area of the wafer W while moving the mask M and the wafer W relative to the projection optical system PL according to a so-called step-and-scan method. In this case, the shape of the illumination area on the mask M is a rectangular shape with a ratio of the short side to the long side of, for example, 1: 3, and the cross-sectional shape of each microlens of the microlens array 11 is a similar rectangular shape. It becomes.

Next, the configuration and operation of the polarization controller including the prism type PBS 4, the half-wave plate 5, and the depolarizer 6 in the illumination optical system ILS in FIG. 1 will be described. In FIG. 2 and the like, for convenience of explanation, the illumination light IL that passes through the polarization controller is represented as illumination lights IL1 to IL8.
First, the PBS 4 of FIG. 1 is supported by a frame (not shown) so that the polarization beam splitter surface is perpendicular to the ZY plane and intersects the Z axis at 45 ° clockwise. In PBS4, a polarizing beam splitter film is attached to the joint surface of a prism having two equilateral triangles in cross section formed from an optical material such as quartz or fluorite (CaF ₂ ) that transmits an ArF excimer laser (wavelength 193 nm). Later, it can be manufactured by joining the two prisms.

  2A, 2B, and 2C are perspective views illustrating an example of the polarization controller in FIG. In FIG. 2A, the PBS 4 transmits the illuminating light IL1 composed of the P-polarized component (light linearly polarized in the Z direction) of the incident illuminating light IL to the half-wave plate 5 side, and is S-polarized. The illumination light IL2 made up of components (light linearly polarized in the X direction) is reflected. The light source 1 in FIG. 1 of the present embodiment is an ArF excimer laser light source that emits substantially linearly polarized laser light, and the polarization direction of the illumination light IL when entering the PBS 4 is in the Z direction (P-polarized light). It is set to be. However, in actuality, the polarization direction of the illumination light IL when entering the PBS 4 due to a subtle change or temporal change in the light emission state of the light source 1 and vibration of the beam matching unit (not shown) is such that the polarization direction is Z. Slightly deviate from the direction or slightly elliptically polarized. However, in the present embodiment, since the PBS 4 is provided, the illumination light IL1 linearly polarized in the Z direction is always supplied from the PBS 4 to the half-wave plate 5. The extinction ratio of the so-called PBS 4 is preferably perfect or higher. However, if the transmittance of the linearly polarized light having the polarization direction substantially orthogonal to the desired polarization direction is approximately 10% or less, The pattern can be exposed without significantly reducing the contrast of the pattern on the wafer.

Next, the half-wave plate 5 is formed of a disk-shaped substrate that is perpendicular to the optical axis AXI (Y-axis) having a size that can cover the cross-sectional shape of the illumination light IL, and is controlled by the illumination control system 21. It is supported by a frame (not shown) so as to be rotationally driven about the optical axis AXI by the controlled drive unit 22 of FIG. The half-wave plate 5 can be formed of a material having a predetermined thickness made of a material having birefringence such as quartz that transmits an ArF excimer laser, magnesium fluoride (MgF ₂ ), and the like. As an example, the drive unit 22 of FIG. 1 monitors a ring-shaped member that holds the half-wave plate 5, a mechanism that rotates the member with a gear, and an absolute value of the rotation angle of the ring-shaped member. And a rotary encoder.

  In FIG. 2A, a half-wave plate 5 has a first crystal axis 5A and a second crystal axis (not shown) perpendicular to the first crystal axis 5A, and when an incident light beam having an exposure wavelength λ is emitted. In addition, a phase difference of 180 ° (λ / 2) occurs between the polarization component in the direction of the first crystal axis 5A and the polarization component in the direction of the second crystal axis. In this case, a state where the first crystal axis 5A of the half-wave plate 5 is parallel to the Z-axis and parallel to the straight line A1 passing through the optical axis AXI is an initial state of the half-wave plate 5. In the present embodiment, the driving unit 22 of FIG. 1 causes the half-wave plate 5 to rotate clockwise (or may be counterclockwise), for example, 45 ° and 22. It can be rotated by 5 °. Therefore, instead of providing a rotary encoder, the drive unit 22 has three limits for detecting the initial state and the state in which the half-wave plate 5 is rotated by 45 ° and 22.5 ° from the initial state. A switch may be provided.

  In FIG. 1, a depolarizer 6 is a disk-shaped disk that is large enough to cover the cross-sectional shape of the illumination light IL and whose central axis is parallel to the optical axis AXI, and has a wedge-shaped crystal prism 6a in the thickness direction. A wedge-shaped quartz glass prism 6b having a complementary shape (for example, a quartz glass prism 6b disposed in close proximity so as to face each other in a state of substantially the same shape as the quartz prism 6a and with a rotation angle different by 180 °); Is supported by a frame (not shown). Instead of the quartz prism 6a, a prism made of a birefringent material such as magnesium fluoride that transmits an ArF excimer laser can also be used. Further, since the optical path of the illumination light IL is bent only by the quartz prism 6a, the quartz glass prism 6b is provided so that the depolarizer 6 has a flat plate shape as a whole so that the optical path of the illumination light IL is not bent. Instead of the quartz glass prism 6b, a prism made of an optical material having no birefringence such as fluorite that transmits an ArF excimer laser or a small birefringence may be used.

  As shown in FIG. 2A, the crystal prism 6a of the depolarizer 6 has a first crystal axis 6aA and a second crystal axis 6aB that are orthogonal to each other in the refractive index in the direction, and the thickness of the crystal prism 6a. As an example, is constant in the direction parallel to the first crystal axis 6aA and changes substantially linearly in the direction parallel to the second crystal axis 6aB. The quartz prism 6a is stably supported at an angle such that the first crystal axis 6aA of the quartz prism 6a is parallel to the Z axis, that is, the second crystal axis 6aB is parallel to the X axis.

  Next, as shown in FIG. 3A, the pattern to be transferred on the mask M in FIG. 1 is a line and space pattern (hereinafter referred to as an L & S pattern) 31X formed with a fine pitch in the X direction. In this case, the illumination light is assumed to be dipole illumination, and the polarization state of the illumination light is assumed to be linearly polarized light whose polarization direction B1 is the Y direction. In this case, the illumination control system 21 on the optical path of the illumination light via the drive unit 23 on the illumination pupil plane 12 based on the command of the main control system 20 in FIG. A diffractive optical element 7B for dipole illumination is installed to increase the amount of light in the two illumination areas 32A and 32B separated in the X direction. Further, the illumination control system 21 sets the rotation angle of the half-wave plate 5 as it is in the initial state of FIG.

  As a result, in FIG. 2A, among the illumination light IL incident on the PBS 4, the illumination light IL1 linearly polarized in the Z direction that has passed through the PBS 4 passes through the half-wave plate 5 as it is and passes in the Z direction. The light is incident on the depolarizer 6 as linearly polarized illumination light IL3. In this case, since the polarization direction of the illumination light IL3 is parallel to the first crystal axis 6aA of the crystal prism 6a, the linearly polarized illumination light IL4 having the same Z direction as that at the time of incidence is emitted from the crystal prism 6a and the depolarizer 6. It is injected. In FIG. 1, since the optical path bending mirror 16 is provided, the Z direction in the polarization controller and the illumination pupil plane 12 corresponds to the Y direction on the mask M.

3B is illuminated by linearly polarized illumination light IL4 whose polarization direction B2 is the Z direction, and the L & S pattern 31X of FIG. Since it is illuminated by dipolar illumination linearly polarized in the Y direction, the L & S pattern 31X can be transferred onto the wafer W with high resolution.
On the other hand, when the pattern to be transferred on the mask M in FIG. 1 is an L & S pattern 31Y formed at a fine pitch in the Y direction, as shown in FIG. As polar illumination, the polarization state is assumed to be linearly polarized light whose polarization direction B3 is the X direction. In this case, as shown in FIG. 3D on the illumination pupil plane 12, in order to increase the amount of light in the two illumination areas 33A and 33B separated in the Y direction, 2 on the optical path of the illumination light in FIG. A diffractive optical element 7C for polar illumination is installed. Further, the illumination control system 21 sets the rotation angle of the half-wave plate 5 to 45 ° from the initial state as shown in FIG. That is, the first crystal axis 5A of the half-wave plate 5 is rotated by 45 ° around the optical axis AXI from the straight line A1 in the initial state.

  As a result, in FIG. 2B, the illumination light IL1 linearly polarized in the Z direction emitted from the PBS 4 is rotated linearly by 90 ° by the half-wave plate 5 and linearly polarized in the X direction. The light enters the depolarizer 6 as IL5. In this case, since the polarization direction of the illumination light IL5 is parallel to the second crystal axis 6aB of the crystal prism 6a, the linearly polarized illumination light IL6 having the same X direction as that at the time of incidence is emitted from the crystal prism 6a and the depolarizer 6. It is injected. The dipole illumination regions 33A and 33B on the illumination pupil plane 12 in FIG. 3D are illuminated by linearly polarized illumination light IL6 whose polarization direction B4 is the X direction, and the L & S pattern 31Y in FIG. Since it is illuminated by dipole illumination linearly polarized in the direction, the L & S pattern 31Y can be transferred onto the wafer W with high resolution.

  Next, when the pattern to be transferred on the mask M in FIG. 1 is, for example, a rough pattern with low density, the polarization state of the illumination light is set to random polarization (non-polarization). . In this case, for example, a diffractive optical element 7A is installed on the optical path of the illumination light in FIG. Further, the illumination control system 21 sets the rotation angle of the half-wave plate 5 to 22.5 ° (= 45 ° / 2) from the initial state as shown in FIG. That is, the first crystal axis 5A of the half-wave plate 5 is rotated 22.5 ° around the optical axis AXI from the straight line A1 in the initial state.

  As a result, in FIG. 2C, the illumination light IL1 linearly polarized in the Z direction emitted from the PBS 4 has the polarization direction rotated by 45 ° by the half-wave plate 5 and linearly polarized in the oblique direction. It enters the depolarizer 6 as IL7. In this case, the polarization direction of the illumination light IL7 is inclined at 45 ° with respect to the two crystal axes 6aA and 6aB of the crystal prism 6a, and the thickness of the crystal prism 6a gradually changes along the polarization direction. Therefore, random unpolarized illumination light IL8 is emitted from the quartz prism 6a and the depolarizer 6 depending on the position of the polarization direction (or the shape of elliptically polarized light). Therefore, the pattern of the mask M is illuminated with non-polarized illumination light by irradiating the mask M with the illumination light IL8 superimposed on the microlens array 11 (optical integrator) of FIG.

  As described above, according to the exposure apparatus of the present embodiment, the polarization direction of the illumination light irradiated on the mask M is controlled by controlling the rotation angle of the half-wave plate 5 in the illumination optical system ILS. The linearly polarized light in the X direction, the linearly polarized light in which the polarization direction is the Y direction, and the polarization state can be set to random non-polarized light. Accordingly, since the polarization state of the illumination light can be easily optimized according to the pattern to be transferred, various patterns can be exposed on the wafer W with high resolution.

Effects and modifications of the present embodiment are as follows.
(1) The illumination optical system ILS in FIG. 1 is arranged in the optical path of the illumination light in the illumination optical device that illuminates the pattern surface (illuminated surface) of the mask M with illumination light, and is in the Z direction (predetermined direction). PBS4 (Linear Polarization Extraction Element) that selectively transmits linearly polarized light having the polarization direction of λ and the downstream of PBS4, the polarization state of the illumination light is linearly polarized in a direction parallel to the Z axis or X axis The state of the illumination light IL3, IL5 (first polarization state) in FIGS. 2A and 2B (the first polarization state), or the state of the illumination light IL7 in FIG. 1/2 wavelength plate 5 (first polarization state variable element) that can be changed to the second polarization state) and illumination light that is arranged downstream of the half wavelength plate 5 and emitted from the half wavelength plate 5 A depolarizer 6 (second polarization state variable element) that can change the polarization state of That.

The depolarizer 6 changes the polarization state of the illumination lights IL3 and IL5 to the illumination light IL4 and IL6 in the same polarization direction (third polarization state), and changes the polarization state of the illumination light IL7 to the non-polarization state of the illumination light IL8. Variable to (fourth polarization state).
Therefore, even if the polarization state of the illumination light IL supplied from the light source 1 fluctuates due to a change with time or the like, the linearly polarized light extracted in the Z direction extracted by the PBS 4 is supplied to the half-wave plate 5. Also, the illumination light having three different polarization states can be generated by the half-wave plate 5 and the depolarizer 6. Therefore, it is possible to always control a plurality of polarization states with high accuracy.

(2) The half-wave plate 5 is disposed between the PBS 4 and the mask surface, and the depolarizer 6 is disposed between the PBS 4 and the mask surface. With this arrangement, light that is linearly polarized in a desired direction can be supplied to the depolarizer 6.
(3) Further, the half-wave plate 5 is rotatable around the optical axis AXI (first rotation axis). The rotation axis may be a straight line parallel to the optical axis AXI. Therefore, by controlling the rotation angle of the half-wave plate 5, the polarization state of the illumination light after passing through the depolarizer 6 is changed to the Z direction (Y direction on the mask M), the linear polarization in the X direction, and the non-polarization state. It can be easily set with high accuracy to either polarization.

(4) Further, the half-wave plate 5 is rotated around its rotation axis in accordance with the state of polarized illumination (linearly polarized light or non-polarized light) in the illumination condition for illuminating the pattern surface of the mask M. Therefore, the polarization illumination can be controlled only by controlling the rotation angle of the half-wave plate 5.
(5) The depolarizer 6 includes a birefringent crystal prism 6a. Therefore, a member that can easily generate light in a non-polarized state can be manufactured simply by making the quartz prism 6a wedge-shaped.

  As shown in FIG. 4, the depolarizer 6 can be rotated around the optical axis AXI or a straight line (second rotation axis) parallel to the optical axis AXI so that the rotation angle of the depolarizer 6 can be controlled by the drive unit 28. May be. The drive part 28 controlled by the illumination control system 21 of FIG. 1 can be comprised from the gear mechanism which rotates the cylindrical member (not shown) holding the depolarizer 6, as an example.

  In the modification of FIG. 4, when the polarization state of the illumination light that illuminates the mask M is made non-polarized, the rotation angle of the half-wave plate 5 is set to the initial state, and the depolarizer 6 is illustrated by the drive unit 28. Rotate 45 degrees clockwise (or counterclockwise) from the state 2A (initial state). As a result, the polarization direction of the illumination light IL3 polarized in the Z direction from the half-wave plate 5 toward the depolarizer 6 is inclined at 45 ° with respect to both the crystal axes 6aA and 6aB of the crystal prism 6a. 6 emits non-polarized illumination light IL8. In the modification of FIG. 4, since the polarization state of the illumination light IL3 incident on the depolarizer 6 is exactly parallel to the Z axis, the non-polarization state can be set accurately.

On the other hand, in the case of FIG. 2C, a component polarized in the Z direction or the X direction remains in the illumination light IL7 emitted by rotating the half-wave plate 5 by 22.5 °. If it is, it passes through the depolarizer 6 as it is, and the emitted illumination light IL8 may not be completely unpolarized.
(6) Also, in the illumination optical system ILS of FIG. 1, a prism type PBS 4 is used to extract linearly polarized light from the light from the light source 1. Since the PBS 4 has the same optical path (on the same straight line) as the incident light and the necessary exit light, the optical system can be easily designed and manufactured.

  (7) If it is difficult to manufacture a polarizing beam splitter film of PBS4 for ArF excimer laser light and the manufacturing cost of PBS4 is high, an optical member 35 shown in FIG. It may be used. The optical member 35 is obtained by stacking a plurality of (for example, about 10 to 20) glass plates 34 made of flat-plate quartz or the like having a thickness of about 1 mm and is extremely easy to manufacture. When the incident angle θi of the illumination light IL with respect to the optical member 35 is 45 ° as shown in FIG. 5A, the transmittance of the P-polarized illumination light IL1 on one surface of the glass plate 34 is about 99%. The transmittance of the S-polarized illumination light IL2 is about 90%. Therefore, for example, when 15 sheets (30 surfaces) of the glass plates 34 are stacked, the transmittance of S-polarized light is reduced to about 5% or less. Therefore, the optical member 35 can be used as an inexpensive optical member that extracts only approximately P-polarized illumination light IL1 from incident light with high accuracy.

Further, as shown in FIG. 5B, by making the incident angle θi of the illumination light IL incident on the glass plate 34 the Brewster angle θb, the transmittance of the S-polarized illumination light IL2 in the glass plate 34 is further increased. Can be reduced. Therefore, the optical member 35 can be configured using a smaller number of glass plates 34.
The extinction ratio of the so-called optical member 35 (here, a plurality of the glass plates 34 stacked obliquely (for example, about 10 to 20)) is preferably complete or higher, but desired. If the transmittance of linearly polarized light having a polarization direction substantially perpendicular to the polarization direction with respect to the optical member 35 is approximately 10% or less, the pattern can be exposed without significantly reducing the contrast of the pattern on the wafer. .

  (8) In FIG. 1, the half-wave plate 5 is used. However, instead of the half-wave plate 5, the light enters as shown in FIGS. 6 (A) and 6 (B). Optical rotation elements 36A and 36B that emit the illumination light IL5 and IL7 by rotating the polarization direction of the illumination light IL1 by 90 ° and 45 °, respectively, may be used. The optical rotators 36A and 36B can be manufactured by controlling the thickness of a birefringent material such as quartz. In this case, instead of the rotatable half-wave plate 5 of FIG. 1, the optical rotators 36A and 36B may be configured to be detachable with respect to the optical path of the illumination light IL1. For example, the optical rotation elements 36A and 36B may be configured to be switchable with respect to the optical path of the illumination light IL1 using a turret or the like.

(9) The illumination optical system ILS in FIG. 1 is arranged in the optical path between the depolarizer 6 and the mask surface, and the microlens array 11 (optical integrator) for uniformly illuminating the mask surface with the illumination light It has. Thereby, the illuminance distribution on the mask surface can be made uniform. A normal fly-eye lens can be used instead of the microlens array 11.
Instead of the microlens array 11 that is a wavefront division type integrator, a rod type integrator as an internal reflection type optical integrator may be used. In this case, in FIG. 1, a condensing optical system is added to the mask M side of the zoom lens 9 to form a conjugate surface such as the diffractive optical element 7A, and the rod is positioned so that the incident end is positioned near the conjugate surface. Place type integrator.

  In addition, a relay optical system for forming an image of the illumination field stop arranged on the exit end face of the rod-type integrator or in the vicinity of the exit end face on the mask M is disposed. In this configuration, the secondary light source is formed on the pupil plane of the relay optical system (the virtual image of the secondary light source is formed near the incident end of the rod integrator). A relay optical system for guiding the light beam from the rod-type integrator to the mask M is a light guide optical system.

(10) Further, a relay optical system (13, 15) and a condenser optical system 17 which are arranged in the optical path between the microlens array 11 and the mask surface and guide the light beam from the microlens array 11 to the mask surface. (Light guide optical system) is further provided. As a result, the light beam from the optical integrator is superimposed and irradiated onto the mask M.
(11) Further, diffractive optical elements 7A to 7C, etc. (light intensity distribution formation) which are detachably disposed in the optical path between the depolarizer 6 and the mask surface and form illumination light having a light intensity distribution of a predetermined shape. Means). The light intensity distribution of the illumination light can be efficiently formed in a desired distribution by the diffractive optical element 7A or the like. If the use efficiency of the illumination light IL may be reduced, an aperture stop system having various shapes of aperture stops arranged on the illumination pupil plane may be used instead of the diffractive optical element.

(12) In the embodiment of FIG. 1, the light source 1 for supplying the illumination light IL is provided. In the present embodiment, even if the polarization state of the illumination light IL from the light source 1 varies, the polarization control can be performed with high accuracy.
(13) Further, the exposure method of the above embodiment is an illumination method for illuminating the mask surface using the illumination optical system ILS in the exposure method for exposing a pattern to the wafer W (photosensitive substrate) using the projection optical system PL. And a step of exposing the wafer W to a mask pattern arranged on the mask surface.

The exposure apparatus of the above embodiment includes the illumination optical system ILS, the light source 1 that supplies illumination light that illuminates the mask M arranged on the mask surface, and the projection that exposes the pattern of the mask M onto the wafer W. And an optical system PL.
In this case, since polarization control can be performed with high accuracy, a fine pattern can be transferred onto the wafer W with high resolution.

The present invention can also be applied to an immersion type exposure apparatus disclosed in, for example, International Publication No. 99/49504 pamphlet or the like, or a proximity type exposure apparatus.
Further, when an electronic device (microdevice) such as a semiconductor device is manufactured using the exposure apparatus of the above-described embodiment, the electronic device performs function / performance design of the electronic device as shown in FIG. A mask (reticle) manufacturing step 222 based on this design step, a substrate substrate (wafer) manufacturing step 223, and a mask pattern is formed on the substrate by the exposure apparatus (projection exposure apparatus) of the above-described embodiment. Exposure process, development process of the exposed substrate, substrate processing step 224 including heating (curing) and etching process of the developed substrate, and device assembly step (processing process such as dicing process, bonding process, packaging process) ) 225 and the inspection step 226 and the like.

In other words, this device manufacturing method includes a lithography process, and the photosensitive substrate is exposed using the exposure apparatus of the above-described embodiment in the lithography process. At this time, since the polarization control can be performed with high accuracy and a fine pattern can be transferred onto the photosensitive substrate with high resolution, a highly functional electronic device can be manufactured with high accuracy.
Further, the present invention is not limited to the application to the manufacturing process of a semiconductor device. For example, a manufacturing process such as a liquid crystal display element and a plasma display, an imaging element (CMOS type, CCD, etc.), a micromachine, a MEMS ( (Microelectromechanical systems), thin film magnetic heads, and various devices (electronic devices) such as DNA chips can be widely applied.

  Further, in each of the above-described embodiments, the present invention has been described by taking an exposure apparatus including an illumination optical apparatus as an example. However, the present invention is applied to a general illumination optical apparatus for illuminating an irradiated surface other than a mask. Obviously it can be done.

It is a figure which shows schematically the structure of the exposure apparatus provided with the illumination optical system of an example of embodiment of this invention. (A), (B), (C) is a perspective view which shows the structure of the polarization control part in FIG. 1, respectively. (A) is a diagram showing an example of a pattern to be transferred, (B) is a diagram showing an example of dipole illumination, (C) is a diagram showing another example of a pattern to be transferred, and (D) is dipole illumination. It is a figure which shows the other example of. It is a perspective view which shows the modification of the polarization control part of FIG. (A) is a figure which shows the optical member which can be used instead of a polarization beam splitter, (B) is a figure which shows the other example of the usage method of the optical member of FIG. 5 (A). (A), (B) is a figure which shows the optical rotatory element which can be used instead of the half-wave plate 5. FIG. It is a flowchart which shows the manufacturing process of the semiconductor device as an electronic device.

Explanation of symbols

  ILS ... illumination optical system, PL ... projection optical system, 1 ... light source, 4 ... polarization beam splitter (PBS), 5 ... 1/2 wavelength plate, 6 ... depolarizer, 6a ... crystal prism, 7A-7C ... diffractive optical element, 9 ... Zoom lens, 10 ... Axicon system, 11 ... Micro lens array, 21 ... Illumination control system

Claims (17)

In the illumination optical device that illuminates the illuminated surface with illumination light,
A linearly polarized light extracting element that is arranged in the optical path of the illumination light and selectively transmits linearly polarized light having a predetermined polarization direction;
A first polarization state variable element that is arranged downstream of the linear polarization extraction element and changes a polarization state of the illumination light to a first polarization state or a second polarization state;
A second polarization state variable element that is arranged downstream of the first polarization state variable element and changes a polarization state of the illumination light emitted from the first polarization state variable element;
The second polarization state variable element changes the first polarization state of the illumination light to a third polarization state, and changes the second polarization state of the illumination light to a fourth polarization state. Optical device. The first polarization state variable element is disposed between the linearly polarized light extraction element and the irradiated surface,
The illumination optical apparatus according to claim 1, wherein the second polarization state variable element is disposed between the first polarization state variable element and the irradiated surface.   The illumination optical apparatus according to claim 1, wherein the first polarization state variable element is rotatable about a first rotation axis.   The illumination optical apparatus according to claim 3, wherein the first polarization state variable element rotates about the first rotation axis according to an illumination condition for illuminating the irradiated surface. The second polarization state variable element includes a birefringent optical member,
The illumination optical device according to any one of claims 1 to 4, wherein the optical member is rotatable about a second rotation axis.   6. The illumination optical apparatus according to claim 1, wherein the linearly polarized light extraction element is a polarization beam splitter.   The illumination optical apparatus according to claim 1, wherein the linearly polarized light extraction element is a plurality of flat glass plates arranged in an overlapping manner.   The illumination optical apparatus according to claim 1, wherein the first polarization state variable element is a half-wave plate.   The illumination optical device according to claim 1, wherein the first polarization state variable element is an optical rotation element. The first polarization state variable element includes at least two optical rotation elements,
The illumination optics according to any one of claims 1, 2, and 5 to 7, wherein the at least two optical rotation elements are configured to be switchable with respect to an optical path of the illumination light. apparatus.   2. An optical integrator disposed in an optical path between the second polarization state variable element and the irradiated surface for uniformly illuminating the irradiated surface with the illumination light. The illumination optical device according to any one of 1 to 10.   12. The optical system according to claim 11, further comprising a light guide optical system that is disposed in an optical path between the optical integrator and the irradiated surface and guides a light beam from the optical integrator to the irradiated surface. The illumination optical device described.   A light intensity distribution forming unit that is detachably disposed in an optical path between the second polarization state variable element and the irradiated surface and forms the illumination light having a light intensity distribution having a predetermined shape; The illumination optical apparatus according to claim 1, wherein the illumination optical apparatus is an illuminating optical apparatus.   The illumination optical apparatus according to claim 1, further comprising a light source unit that supplies the illumination light. In an exposure method for exposing a pattern to a photosensitive substrate using a projection optical system,
An illumination step of illuminating the irradiated surface using the illumination optical device according to any one of claims 1 to 14,
An exposure step of exposing the photosensitive substrate with a pattern of a mask disposed on the irradiated surface;
An exposure method comprising: While comprising the illumination optical device according to any one of claims 1 to 13,
A light source unit for supplying illumination light for illuminating a mask arranged on the irradiated surface;
A projection optical system for exposing the pattern of the mask onto a photosensitive substrate;
An exposure apparatus comprising: An electronic device manufacturing method including a lithography process,
An electronic device manufacturing method using the exposure apparatus according to claim 16 in the lithography process.

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