JP2010157743A - Illumination optical apparatus, projection aligner, exposure method, and device manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an illumination optical apparatus which reduces illumination light loss and achieves superior illumination uniformity in illuminating a mask with light of a predetermined polarization state, and related others. <P>SOLUTION: The illumination optical apparatus includes an optical polarization conversion member which is included in an illumination optics for illuminating a first object based on light from a light source of a substantially single polarization state. The optical polarization state of the illumination light that distributes in a specific orbicular zone is converted to a predetermined polarization state by the optical polarization conversion member, wherein the specific orbicular zone corresponds to a predetermined orbicular zone in a predetermined plane normal to the optical axis of the illumination optics. The optical polarization conversion member includes a plurality of optical polarization conversion elements which are arranged at respectively different positions in a plane normal to the optical axis of the illumination optics. The optical polarization conversion elements are formed of a material having optical rotatory power. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exposure technique used in a lithography process for manufacturing various devices such as a semiconductor integrated circuit (LSI or the like), an image sensor, or a liquid crystal display, and more specifically, a mask pattern is formed with light in a predetermined polarization state. It is related with the exposure technique illuminated with. The present invention also relates to a device manufacturing technique using the exposure technique.

  When forming a fine pattern of an electronic device such as a semiconductor integrated circuit or a liquid crystal display, a pattern of a reticle (or a photomask, etc.) as a mask drawn by enlarging the pattern to be formed approximately 4 to 5 times is projected. A method is used in which an exposure transfer is performed by reducing on a wafer (or glass plate or the like) as a substrate to be exposed (photosensitive member) via an optical system. For the exposure transfer, a stationary exposure type projection exposure apparatus such as a stepper and a scanning exposure type projection exposure apparatus such as a scanning stepper are used. The resolution of the projection optical system is proportional to the value obtained by dividing the exposure wavelength by the numerical aperture (NA) of the projection optical system. The numerical aperture (NA) of the projection optical system is obtained by multiplying the sine of the maximum incident angle of the illumination light for exposure to the wafer by the refractive index of the medium through which the light beam passes.

Therefore, in order to cope with miniaturization of semiconductor integrated circuits and the like, the exposure wavelength of the projection exposure apparatus has been made shorter. At present, the main exposure wavelength is 248 nm of the KrF excimer laser, but the 193 nm of the shorter wavelength ArF excimer laser is also entering the practical stage. Further, there has been proposed a projection exposure apparatus using a so-called vacuum ultraviolet light source such as an F ₂ laser having a shorter wavelength of 157 nm and an Ar ₂ laser having a wavelength of 126 nm. In addition to shortening the wavelength, it is possible to increase the resolution by increasing the numerical aperture (increasing NA) of the projection optical system. Therefore, development has been made to further increase the NA of the projection optical system. The NA of the current state-of-the-art projection optical system is about 0.8.

  On the other hand, as a technique for improving the resolution of a transferred pattern even when projection optical systems having the same exposure wavelength and the same NA are used, a method using a so-called phase shift reticle and a distribution of incident angles of illumination light on the reticle are predetermined. So-called super-resolution techniques such as annular illumination, dipole illumination, and quadrupole illumination that control the distribution are also in practical use.

  Among them, the annular illumination limits the incident angle range of the illumination light to the reticle, that is, the distribution of the illumination light on the pupil plane of the illumination optical system with the optical axis of the illumination optical system as the center. By limiting to the predetermined ring zone region, the effect of improving the resolution and the depth of focus is exhibited (for example, see Patent Document 1). On the other hand, the dipole illumination and the quadrupole illumination correspond not only to the incident angle range but also to the incident direction of the illumination light when the pattern on the reticle has a specific directionality. By limiting to the direction, the resolution and the depth of focus are greatly improved (for example, see Patent Documents 2 and 3).

  There has also been proposed an attempt to improve the resolution and depth of focus by optimizing the polarization state of the illumination light with respect to the direction of the pattern on the reticle. In this method, illumination light is converted into linearly polarized light having a polarization direction (electric field direction) in a direction perpendicular to the periodic direction of the pattern, that is, in a direction parallel to the longitudinal direction of the pattern. It improves (for example, refer nonpatent literature 1).

  Also in annular illumination, let the polarization direction of illumination light coincide with the circumferential direction in the annular region where the illumination light is distributed on the pupil plane of the illumination optical system to improve the resolution and contrast of the projected image. An attempt has been made (see, for example, Patent Document 4).

JP-A-61-91662 Japanese Patent Laid-Open No. 4-101148 JP-A-4-225357 JP-A-6-053120

ThimothyA. Brunner, et al .: "High NA Lithographic imaging at Brewster'sange1", SPIE (USA) Vo1.4691, pp.1-24 (2002)

  In the prior art as described above, when performing annular illumination, on the pupil plane of the illumination optical system, when attempting to change the polarization state of the illumination light to linearly polarized light substantially matching the circumferential direction of the annular region, There was a problem that the loss of illumination light amount increased and the illumination efficiency decreased.

  This will be described in detail. Illumination light emitted from the narrow-band KrF excimer laser light source, which has been the mainstream in recent years, is uniform linearly polarized light. If this is guided to the reticle while maintaining the polarization state as it is, the reticle is illuminated with uniform linearly polarized light, so a straight line that coincides with the circumferential direction of the annular zone of the pupil plane of the illumination optical system as described above. Needless to say, polarized light cannot be realized.

  In the above-mentioned Patent Document 4, a laser light source of linearly polarized light is used, and a predetermined approximate annular zone is placed in a plane (that is, in the pupil plane) that has a Fourier transform relationship with respect to the reticle pattern in the illumination optical system. A plurality of half-wave plates in which spatial filters that transmit illumination light beams distributed only in the region, the two-pole region, or the four-pole region are arranged, and the directions of the optical axes of the spatial filters are mutually rotated It has been proposed to realize linearly polarized light in which the polarization state of the illumination light is substantially matched with the circumferential direction around the optical axis of the illumination optical system without loss of the amount of illumination light.

  However, the Fourier transform surface, which is the arrangement position of the plurality of half-wave plates disclosed in Patent Document 4, is a surface that substantially coincides with the exit side surface of the fly-eye lens that is an illuminance uniformizing means. A half-wave plate that functions effectively with respect to such an illumination light beam needs to be a very thin wave plate in order to cope with a large opening angle (incident angle) of the illumination light beam. There is a problem that processing is difficult.

  In Patent Document 4, in the embodiment of illumination (quadrupole illumination) in which the illumination light beam is distributed in four predetermined regions on the Fourier transform plane, the plurality of half-wave plates are arranged on the light source side from the fly-eye lens. It is disclosed that it may be arranged. In addition, since the opening angle of illumination light is generally smaller on the light source side than the fly-eye lens, the requirement for the incident angle characteristic to the half-wave plate is relaxed.

  However, if the plurality of half-wave plates are arranged closer to the light source side than the fly-eye lens for annular illumination, illuminance non-uniformity (illuminance unevenness) of the illumination light beam on the reticle surface is likely to occur. In annular illumination, the fly-eye lens needs to be continuously arranged on the pupil plane in the illumination optical system, and as a result, it is shielded by the boundary region of the plurality of wave plates, the holding mechanism, etc. This is because the illumination light having deteriorated uniformity is incident on the fly-eye lens, and the adverse effect remains on the reticle surface.

  The present invention has been made in view of such a problem, and when illuminating a mask such as a reticle with illumination light in a predetermined polarization state, exposure that reduces light loss and achieves good illuminance uniformity. The first object is to provide technology.

  Furthermore, the present invention can reduce a decrease in the amount of illumination light when setting the polarization state of the illumination light in a region such as an annular zone, dipole, quadrupole or the like on the pupil plane of the illumination optical system to a predetermined state. It is a second object of the present invention to provide an exposure technique that can improve the resolution and the like without substantially reducing the processing capability.

  Another object of the present invention is to provide a device manufacturing technique that can manufacture a high-performance device with a high processing capacity by using the exposure technique.

  An illumination optical apparatus according to the present invention is an illumination optical apparatus that irradiates a first object (R) with illumination light from a light source (1) having a substantially single polarization state via an illumination optical system (ILS). Polarized light that converts the polarization state of the illumination light distributed in a specific annular zone region, which is a predetermined annular zone region within a predetermined plane perpendicular to the optical axis (AX2) of the illumination optical system, into a predetermined polarization state A conversion member (12a etc.) is provided. In particular, the polarization conversion member includes a plurality of polarization conversion elements disposed at different positions in a plane perpendicular to the optical axis of the illumination optical system, and the plurality of polarization conversion elements are formed of a material having optical activity. Has been.

  The light source generates the illumination light in a substantially single polarization state, and the illumination optical system substantially determines the illuminance of the illumination light irradiated on the first object in addition to the polarization conversion member. In order to make it uniform, an illuminance uniforming member (14) may be provided. In this case, the polarization conversion member is disposed closer to the light source than the illuminance uniforming member.

  For example, the material having optical activity may be quartz. The plurality of polarization conversion elements formed of a material having optical rotation may have different thicknesses.

  According to the present invention, for example, by setting the material, thickness, and shape of the polarization conversion member to predetermined ones, among the illumination lights emitted from the light source, the illumination light that passes through the specific annular zone region Can be converted into a predetermined polarization state.

  In addition, since the polarization conversion member is arranged on the light source side with respect to the illuminance uniforming member, the opening angle of the illumination light beam transmitted through the polarization conversion member, that is, the incident angle to the polarization conversion member can be reduced. As a result, the degree of freedom of selection of the polarization conversion member is increased to improve its feasibility, and the polarization state of the illumination light can be controlled with almost no loss of light amount.

  In this case, of the illumination light, the specific illumination light (ILL1, ILD1, etc.) that passes through the specific ring zone region and is applied to the first object at a predetermined incident angle (φ) is mainly S-polarized light. It can be set as the illumination light of the polarization state used as a component.

  Further, the predetermined polarization state of the illumination light distributed in the specific ring zone region is assumed to be a polarization state mainly composed of linearly polarized light in the circumferential direction around the optical axis of the illumination optical system. You can also. The predetermined surface can be a Fourier transform surface for the first object in the illumination optical system.

  Moreover, you may have the light beam limiting member (9a, 9b) which restrict | limits the illumination light irradiated to the 1st object to the light beam substantially distributed in the specific ring zone area | region. Further, the light flux limiting member may further restrict the light flux to a plurality of substantially discrete regions within the specific annular zone region. In these cases, annular illumination, dipole illumination, quadrupole illumination, or the like can be realized without substantially reducing the amount of illumination light.

  The light flux limiting member includes, for example, a diffractive optical element disposed between the light source and the polarization conversion member. By using the diffractive optical element, the light loss can be further reduced.

  The illumination optical device according to the present invention may include illuminance non-uniformity eliminating means (B1 or the like) for eliminating illuminance non-uniformity of the illumination light on the first object caused by the polarization conversion member. The illuminance non-uniformity eliminating means may include a holding mechanism (13a, 13b, etc.) that holds the plurality of wave plates outside the optical path of the illumination light. Moreover, as an example, the illuminance non-uniformity eliminating means may include a substrate that holds the plurality of wavelength plates and is transparent to the illumination light.

  The illuminance uniforming member is, for example, a fly eye lens (14). As an example, the non-uniform illuminance eliminating means is a shielding member (B1 or the like) disposed in the vicinity of the exit side surface of the fly-eye lens or the conjugate surface thereof. The shielding member may be a member that shields a portion of light flux corresponding to a boundary portion of the plurality of wave plates constituting the polarization conversion member in the vicinity of the exit side surface of the fly-eye lens or the conjugate surface thereof. . Thereby, the illuminance uniformity of the illumination light on the first object can be further improved.

  In addition, as an example, the illuminance non-uniformity eliminating means may be configured such that the width of the illuminance lowering portion formed on the incident surface of the fly-eye lens by the boundary portions of the plurality of wave plates constituting the polarization conversion member is changed to the fly-eye lens. The illuminance non-uniformity of the illumination light on the first object is eliminated by extending the width of each lens element constituting the lens. Thereby, the illuminance uniformity of the illumination light on the first object can be further improved without loss of the illumination light quantity.

  As an example, the illumination optical apparatus of the present invention can include a loading / unloading mechanism for retracting the polarization conversion member out of the optical path of the illumination light.

  Next, an exposure apparatus according to the present invention has the illumination optical apparatus of the present invention as an illumination optical apparatus for illuminating a first object, and projects a pattern image on the first object onto a second object. (25). According to the present invention, the illumination light that illuminates the first object is polarized in a predetermined direction in the circumferential direction of the specific annular zone while the polarization state of the illumination light passing through the specific annular zone has almost no light loss. State.

  Further, as an example, the specific illumination light that passes through the specific ring zone region and is irradiated on the first object in a predetermined incident angle range can be made into illumination light in a polarization state mainly composed of S-polarized light. . As a result, it is possible to improve the imaging performance when the fine pattern formed on the first object is projected onto the second object via the projection optical system.

  In addition, a light flux limiting member may be provided in the illumination optical device in the exposure apparatus of the present invention, and the illumination light irradiated on the first object may be limited within the specific ring zone region. As a result, the first object is illuminated with linearly polarized light having a polarization direction substantially coincident with the circumferential direction of the annular region under conditions of annular illumination. As a result, the projected image of the line-and-space pattern arranged on the first object at a fine pitch in an arbitrary direction is mainly formed by illumination light whose polarization direction is parallel to the longitudinal direction of the line pattern. Imaging properties such as contrast, resolution and depth of focus are improved.

  Further, the luminous flux limiting member may limit the illumination light applied to the first object to a plurality of specific substantially discrete regions within the specific ring zone region. Thus, the first object is illuminated with linearly polarized light that matches the circumferential direction of the discrete regions under conditions such as dipole illumination or quadrupole illumination. As a result, the projected image of the line-and-space pattern arranged on the first object with a fine pitch in a predetermined direction is mainly formed by illumination light whose polarization direction is parallel to the longitudinal direction of the line pattern. Imaging properties such as contrast, resolution and depth of focus are improved.

  Next, the exposure method according to the present invention uses the projection exposure apparatus of the present invention to expose the photoconductor (W) as the second object with the pattern image of the mask (R) as the first object. It is. According to the present invention, the first object can be illuminated with annular illumination, dipole illumination, quadrupole illumination, or the like, and the polarization state of the illumination light incident on the first object is suitable for exposure of a fine pattern on the mask. Polarization state. Therefore, a pattern formed with a fine pitch on the mask can be transferred with good imaging characteristics with almost no light loss.

  A device manufacturing method according to the present invention is a device manufacturing method including a lithography process, and a pattern is transferred to a photoreceptor using the exposure method of the present invention in the lithography process. According to the present invention, a pattern can be transferred with high processing capability and high imaging characteristics.

  According to the present invention, since the polarization state of the illumination light is controlled using the polarization conversion member, it is possible to reduce the light amount loss when the first object (mask) is illuminated with the illumination light in the predetermined polarization state. Further, since the polarization conversion member is arranged on the light source side with respect to the illuminance uniformizing means such as a fly-eye lens, there is an effect that there are few restrictions on the selection of the polarization conversion member.

  Furthermore, according to the present invention, an illumination optical apparatus and a projection exposure apparatus with good illuminance uniformity are provided in order to eliminate the illuminance non-uniformity of the illumination light on the first object caused by the polarization conversion member by the illuminance non-uniformity eliminating means. It is possible to realize.

  Further, by using a light flux limiting member, when illuminating the first object with annular illumination, dipole illumination, quadrupole illumination, or the like, at least one of the specific annular zone area is hardly reduced. The polarization state of the illumination light passing through the region of the part can be set to a state in which linearly polarized light parallel to the circumferential direction of the specific annular region is a main component.

  Therefore, in an exposure apparatus equipped with such an illumination optical system, an image is formed when exposing a pattern in which line patterns having a longitudinal direction are arranged at a fine pitch along the direction of the linearly polarized light on the first object. Characteristics can be improved. Further, the polarization state of the illumination light passing through at least a part of the specific annular zone with the first object being annular illumination, and linearly polarized light parallel to the circumferential direction of the specific annular zone is mainly used. By irradiating with illumination light in a component state, it is possible to improve the imaging characteristics of a pattern having an arbitrary direction on the first object.

  Further, by using the luminous flux restricting member, the above-described improvement of the imaging performance can be achieved by realizing the above-described annular illumination, dipole illumination, quadrupole illumination, or the like without substantially reducing the amount of illumination light. It is possible to provide a projection exposure apparatus and an exposure method that can be realized without a decrease in throughput.

It is the figure which partly cut off showing the schematic structure of the projection exposure apparatus of an example of embodiment of this invention. (A) is the figure which looked at 1st Example of polarization conversion member 12a etc. to + Y direction, (B) is sectional drawing which follows the AA 'line of FIG. 2 (A). (A) is the figure which looked at 2nd Example, such as the polarization conversion member 12a, in + Y direction, (B) is sectional drawing which follows the AA 'line of FIG. 3 (A). (A) is the figure which looked at 1st or 2nd Example, such as the polarization conversion member 12a, in + Y direction, (B) is the figure which looked at the entrance plane 14a of the fly-eye lens 14 in + Y direction. (A) is the figure which looked at the polarization conversion member 12a etc. and the fly eye lens 14 in + Z direction, (B) is the figure which looked at the exit surface 14b of the light shielding member B1 etc. and the fly eye lens 14 in -Y direction. (A) is a diagram for explaining that the illuminance distribution on the reticle R1 is made uniform by the fly-eye lens 14, and (B) is that the illuminance distribution on the reticle R1 is reduced by the dimming part S5 on the fly-eye lens entrance surface 14a. FIG. 6C is a diagram for explaining that the illuminance distribution on the reticle R1 is made uniform by increasing the width of the light reducing portion S55 on the fly-eye lens incident surface 14a. . (A) is a perspective view simply showing the relationship between the pupil plane 15 of the illumination optical system ILS of FIG. 1 and the reticle R, and (B) is a view of a part of FIG. FIG. 7C is a view of a part of FIG. 7A viewed in the −X direction. It is a figure which shows an example of the lithography process for manufacturing a semiconductor device using the projection exposure apparatus of embodiment of this invention.

  Hereinafter, an example of a preferred embodiment of the present invention will be described with reference to the drawings. In this example, the present invention is applied to the case where exposure is performed by a scanning exposure type projection exposure apparatus (scanning stepper) having a step-and-scan method.

  FIG. 1 is a partially cutaway view showing a schematic configuration of a projection exposure apparatus of this example including the illumination optical apparatus of this example. In FIG. 1, the projection exposure apparatus of this example includes a light source 1 and an illumination. An optical system ILS and a projection optical system 25 are provided. Among these, the light source 1 and the illumination optical system ILS constitute an illumination optical device, which is an example of a preferred embodiment of the illumination optical device of the present invention.

  The illumination optical system ILS includes a plurality of optical members arranged along the optical axes (illumination system optical axes) AX1, AX2, AX3 from the relay lens 2 after the light source 1 (light source) to the condenser lens 20 (details). An illumination field of view of the pattern surface (reticle surface) of the reticle R as a mask is illuminated with a uniform illuminance distribution with illumination light (exposure light) IL as an exposure beam from the light source 1. That is, the light source 1 and the illumination optical system ILS constitute the illumination optical apparatus of this example. The latter projection optical system 25 reduces an image obtained by reducing a pattern in the illumination field of the reticle R with a projection magnification M (M is a reduction magnification such as 1/4, 1/5, etc.) under the illumination light. Projection is performed on an exposure region on one shot region on the wafer W to which a photoresist as a substrate to be exposed (substrate) or a photoreceptor is applied. Reticle R and wafer W can also be regarded as a first object and a second object, respectively. The wafer W is a disk-shaped substrate having a diameter of about 200 to 300 mm, such as a semiconductor (silicon or the like) or SOI (silicon on insulator). The projection optical system 25 of this example is a refractive optical system, for example, but a catadioptric system or the like can also be used.

  In FIG. 1, the projection optical system 25, reticle R, and wafer W are scanned and exposed in a plane (XY plane) that takes the Z axis parallel to the optical axis AX4 of the projection optical system 25 and is perpendicular to the Z axis. A description will be given by taking the Y axis along the scanning direction of the reticle R and the wafer W (direction parallel to the paper surface of FIG. 1) and taking the X axis along the non-scanning direction (direction perpendicular to the paper surface of FIG. 1). To do. In this case, the illumination field of the reticle R is an elongated area in the X direction, which is the non-scanning direction, and the exposure area on the wafer W is an elongated area conjugate with the illumination field. Further, the optical axis AX4 of the projection optical system 25 coincides with the illumination system optical axis AX3 on the reticle R.

  First, the reticle R on which the pattern to be exposed and transferred is sucked and held on the reticle stage 21, and the reticle stage 21 moves on the reticle base 22 in the Y direction at a constant speed, and X is corrected so as to correct the synchronization error. The reticle R is scanned by slightly moving in the direction, the Y direction, and the rotation direction around the Z axis. The position of the reticle stage 21 in the X direction and the Y direction, and the rotation angle are measured by a movable mirror 23 and a laser interferometer 24 provided thereon. Based on this measurement value and control information from the main control system 34, the reticle stage drive system 32 controls the position and speed of the reticle stage 21 via a drive mechanism (not shown) such as a linear motor. Above the periphery of the reticle R, a reticle alignment microscope (not shown) for reticle alignment is arranged.

  On the other hand, the wafer W is sucked and held on the wafer stage 27 via a wafer holder (not shown), and the wafer stage 27 can move on the wafer base 30 at a constant speed in the Y direction, and step in the X and Y directions. It is placed so that it can move. Further, the wafer stage 27 incorporates a Z leveling mechanism for aligning the surface of the wafer W with the image plane of the projection optical system 25 based on a measured value of an auto focus sensor (not shown). The X- and Y-direction positions and the rotation angle of the wafer stage 27 are measured by a movable mirror 28 and a laser interferometer 29 provided thereon. Based on this measurement value and control information from the main control system 34, the wafer stage drive system 33 controls the position and speed of the wafer stage 27 via a drive mechanism (not shown) such as a linear motor. Further, in the vicinity of the projection optical system 25, for example, an FIA (Fie1d Image A1ignment) type alignment sensor 31 is disposed by an off-axis method for detecting the position of the alignment mark on the wafer W for wafer alignment. ing.

  Prior to exposure by the projection exposure apparatus of the present example, alignment of the reticle R is performed by the above-described reticle alignment microscope, and the position of the alignment mark formed on the wafer W together with the circuit pattern in the previous exposure process is aligned with the alignment sensor. By detecting at 31, the wafer W is aligned. Thereafter, the reticle stage 21 and the wafer stage 27 are driven while the illumination field IL on the reticle R is irradiated with the illumination light IL, and the reticle R and one shot area on the wafer W are synchronously scanned in the Y direction. The operation of stopping the emission of the illumination light IL and driving the wafer stage 27 to move the wafer W stepwise in the X and Y directions is repeated. The ratio of the scanning speed between the reticle stage 21 and the wafer stage 27 during the synchronous scanning is such that the projection magnification of the projection optical system 25 is maintained in order to maintain the imaging relationship between the reticle R and the wafer W via the projection optical system 25. Equal to M. By these operations, the pattern image of the reticle R is exposed and transferred to all shot areas on the wafer W by the step-and-scan method.

Next, the configuration of the illumination optical system ILS of this example will be described in detail. In FIG. 1, an ArF (argon fluorine) excimer laser (wavelength 193 nm) is used as the light source 1 of this example. As the light source 1, other laser light sources such as KrF (krypton fluorine) excimer laser (wavelength 248 nm), F ₂ (fluorine molecule) laser (wavelength 157 nm), or Kr ₂ (krypton molecule) laser (wavelength 146 nm), etc. Can also be used. These laser light sources (including the light source 1) are narrow band lasers or wavelength-selected lasers, and the illumination light IL emitted from the light source 1 generates linearly polarized light by the narrow band or wavelength selection. The polarization state is the main component. Hereinafter, in FIG. 1, the illumination light IL immediately after being emitted from the light source 1 will be described assuming that the main component is linearly polarized light whose polarization direction (electric field direction) matches the X direction in FIG. 1.

  The illumination light IL emitted from the light source 1 is incident on a polarization control member 4 (detailed later) as a polarization control mechanism via the relay lenses 2 and 3 along the illumination system optical axis AX1. Illumination light IL emitted from the polarization control member 4 passes through a zoom optical system (5, 6) composed of a combination of a concave lens 5 and a convex lens 6, is reflected by a mirror 7 for bending the optical path, and is reflected on the illumination optical axis AX2. The light then enters a diffractive optical element (DOE) 9a. The diffractive optical element 9a is composed of a phase type diffraction grating, and the incident illumination light IL is diffracted in a predetermined direction and travels.

  As will be described later, the diffraction angle and direction of each diffracted light from the diffractive optical element 9a serving as a light beam limiting member is determined by the position of the illumination light IL on the pupil plane 15 of the illumination optical system ILS and the reticle R of the illumination light IL. Corresponds to the incident angle and direction. A plurality of diffractive optical elements 9 a and other diffractive optical elements 9 b having a diffractive action different from that are arranged on the turret-shaped member 8. Then, for example, the member 8 is driven by the exchange mechanism 10 under the control of the main control system 34, and the diffractive optical element 9a or the like at an arbitrary position on the member 8 is loaded at a position on the illumination system optical axis AX2. Thus, according to the pattern of the reticle R, the incident angle range and direction of the illumination light to the reticle R (or the position of the illumination light on the pupil plane 15) can be set to a desired range. Further, the incident angle range can be finely adjusted in an auxiliary manner by moving the concave lens 5 and the convex lens 6 constituting the zoom optical system (5, 6) in the direction of the illumination system optical axis AX1, respectively. it can.

  Illumination light (diffracted light) IL emitted from the diffractive optical element 9a enters the polarization conversion members 12a and 12b of the present invention through the relay lens 11 along the illumination system optical axis AX2. However, as will be described later, the polarization conversion members 12a and 12b are obtained by disposing a plurality of separated polarization conversion members at different positions on a predetermined annular zone centered on the optical axis AX2. And since it is not necessary to arrange | position the polarization conversion member in the vicinity of optical axis AX2, it is not necessary for all the illumination light beams to inject into polarization conversion members 12a and 12b.

  A fly-eye lens 14 for making the illuminance distribution of the illumination light IL on the reticle R uniform is disposed on the reticle R side of the polarization conversion members 12a and 12b. The illumination light IL emitted from the fly-eye lens 14 passes through the relay lens 16, the field stop 17, and the condenser lens 18, and reaches the mirror 19 for bending the optical path. The illumination light IL reflected here is the illumination system optical axis AX3. Then, the reticle R is illuminated through the condenser lens 20. The pattern on the reticle R thus illuminated is projected and transferred onto the wafer W by the projection optical system 25 as described above.

  If necessary, the field stop 17 can be a scanning type, and scanning can be performed in synchronization with the scanning of the reticle stage 21 and the wafer stage 27. In this case, the field stop may be divided into a fixed field stop and a movable field stop.

  In this configuration, the exit side surface of the fly-eye lens 14 is located in the vicinity of the pupil plane 15 of the illumination optical system ILS. The pupil plane 15 is a pattern of the reticle R through optical members (relay lens 16, field stop 17, condenser lenses 18, 20 and mirror 19) in the illumination optical system ILS from the pupil plane 15 to the reticle R. It acts as an optical Fourier transform surface for the surface (reticle surface). In other words, the illumination light emitted from one point on the pupil plane 15 becomes a substantially parallel light beam and irradiates the reticle R at a predetermined incident angle and incident direction. The incident angle and the incident direction are determined according to the position of the luminous flux on the pupil plane 15.

  The optical path bending mirrors 7 and 19 are not essential in terms of optical performance, but if the illumination optical system ILS is arranged in a straight line, the overall height of the exposure apparatus (height in the Z direction) increases. For the purpose of space saving, it is arranged at an appropriate place in the illumination optical system ILS. The illumination system optical axis AX1 coincides with the illumination system optical axis AX2 due to reflection by the mirror 7, and the illumination system optical axis AX2 coincides with the illumination system optical axis AX3 due to reflection by the mirror 19.

  Hereinafter, a first embodiment of the polarization conversion members 12a and 12b in FIG. 1 will be described with reference to FIG.

  The polarization conversion members in the first embodiment are half-wave plates 12a, 12b, 12c, 12d, 12e, 12f, 12g, and 12h made of a birefringent material such as a uniaxial crystal, which are shown in FIG. As shown in FIG. 4A, the optical axis AX2 of the illumination optical system is the center and adjacent to each other. These half-wave plates 12a to 12h are held by holding members 13a, 13b, 13c, 13d, 13e, 13f, 13g, and 13h, respectively, on the outer periphery of the illuminating light beam and at portions outside the optical path of the illumination light beam. . Further, for example, the holding of the half-wave plate 12c is performed by three screws of the holding screws 13c1, 13c2, and 13c3. For example, the holding of the half-wave plate 12d is three screws of the holding screws 13d1, 13d2, and 13d3. This is done with screws.

  FIG. 2B is a cross-sectional view of the half-wave plates 12a to 12h and the holding members 13a to 13h along the line A-A 'in FIG. The effective portions of the half-wave plates 12a to 12h cover an annular region (hereinafter referred to as “specific annular region”) from the inner radius ri to the outer radius ro centered on the optical axis AX2 of the illumination optical system. To be arranged. Each of the shapes is basically a sector shape lacking a central portion so that it can be arranged in the specific annular zone without any gap, and at the position away from the optical axis AX2 by the outer radius ro or more, the presser screw 13c1, It is fixed and held by holding members 13a to 13h by 13c2, 13c and the like.

  In addition, the holding members 13a to 13h are individually attached to the holding frame 13o by predetermined pressing screws so that the holding member 13c is individually provided on the holding frame 13o by the holding screws 13c1 and 13c2 and the holding member 13d by the holding screws 13d1 and 13d2. It is set individually. The holding members 13a to 13h, the holding frame 13o, the press screws 13c1, 13c2, 13c, and the like, and the press screws 13c1, 13c2, and the like constitute the holding mechanism 13 in FIG.

  The diameter of the illumination light beam is not fixed because it is changed by changing the so-called illumination σ or changing the annular illumination, the 2-pole illumination, the 4-pole illumination, etc. The radius r0 does not exceed. That is, the holding members 13a to 13h are configured to hold the half-wave plates 12a to 12h that are polarization conversion members outside the optical path of the illumination light. In the range of the radius r0 centering on the optical axis AX2 that may be in the optical path of the illumination light, the half-wave plates 12a to 12h do not substantially have a gap in their adjacent portions. In addition, they are arranged without having a holding mechanism to be a light shielding member.

  The plurality of half-wave plates 12a to 12h shifts the phase of the linearly polarized light parallel to the direction by a half wavelength with respect to the phase of the linearly polarized light perpendicular to the direction (hereinafter referred to as “reference direction”). Are arranged in different directions within the plane of FIG. 2A, as indicated by the white arrows corresponding thereto.

  That is, for the half-wave plates 12a and 12b, the reference direction is set parallel to the Z axis. When the illumination light transmitted through the wave plates 12a to 12h has the polarization direction (X polarization) in the X direction as described above, the wave plates 12a and 12b having the reference direction convert the polarization state of the illumination light. Therefore, the illumination light transmitted through the wave plates 12a and 12b is emitted as it is while maintaining the X polarization.

  For the half-wave plates 12c and 12d, the reference direction is set to a direction shifted by 45 degrees with respect to the reference direction of the half-wave plates 12a and 12b. At this time, the X-polarized light incident on the half-wave plates 12c and 12d is converted into a linearly polarized light (Y-polarized light) having a polarization direction in the Y direction after the polarization state is converted. Here, the Y direction coincides with the circumferential direction of the circle passing through the half-wave plates 12c and 12d with the optical axis AX as the center at the positions of the half-wave plates 12c and 12d.

  Further, the reference directions of the half-wave plates 12f and 12g are set to a direction rotated 22.5 degrees to the right with respect to the reference directions of the half-wave plates 12a and 12b. At this time, the X-polarized light incident on the half-wave plates 12f and 12g is converted into linearly polarized light parallel to the straight line represented by Z = −X in the coordinate system in FIG. And about the 1/2 wavelength plates 12e and 12h, the reference direction is set to the direction rotated 22.5 degree | times to the left with respect to the reference direction of the said 1/2 wavelength plates 12e and 12h. At this time, the X-polarized light incident on the half-wave plates 12e and 12h is converted into linearly polarized light parallel to the straight line represented by Z = X in the coordinate system in FIG.

  These polarization directions are the circumferences of circles passing through the half-wave plates 12f, 12g, 12e, and 12h around the optical axis AX at the positions of the half-wave plates 12f, 12g, 12e, and 12h. Match the direction. As a result, of the linearly polarized light in the X direction incident on the plane where the half-wave plates 12a to 12h are arranged, the annular zone in the range from the inner radius ri centered on the optical axis AX2 to the outer radius ro. The illumination light distributed in the region is converted into linearly polarized light whose polarization direction is substantially parallel to the circumferential direction of a circle centered on the optical axis AX2.

  Here, the actual lengths of the inner radius ri and the outer radius ro are selected according to the size of the illumination field on the reticle R to be illuminated, the required numerical aperture of the illumination light, the design policy of the illumination optical system ILS, and the like. It is something that should be done and not decided. However, when the illumination apparatus of the present invention is used as the illumination optical system of the projection exposure apparatus, it should be determined in consideration of the numerical aperture of the projection optical system 25 provided in the projection exposure apparatus.

  That is, the outer radius ro has a size that includes an illumination light beam corresponding to a coherence factor σ value that is a ratio of the numerical aperture of illumination light to the numerical aperture (NA) of the projection optical system 25 at least about 0.8 or more. It is preferable to set the inner radius ri, and it is preferable to set the inner radius ri so as to include a light flux having a σ value of about 0.4.

  Of the half-wave plates 12a to 12h, the half-wave plates 12a and 12c do not need to have a function of converting the polarization state of the illumination light as described above. Instead, it can be replaced with quartz glass having a thickness equivalent to that, and the arrangement can be omitted in some cases.

  By the way, since these several 1/2 wavelength plates 12a-h are arrange | positioned rather than the fly eye lens 14 at the light source 1 side (incident side), illumination light in each boundary part of the 1/2 wavelength plates 12a-h When the light is reduced (shielded), the accompanying reduction in the light amount distribution of the illumination light deteriorates the uniformity (illuminance uniformity) of the light amount distribution of the illumination light on the incident surface of the fly-eye lens 14. The deterioration of the illuminance uniformity also adversely affects the illuminance uniformity on the reticle R as the first object to be illuminated.

  However, in the present invention, since the gap is not substantially generated at each boundary portion of the half-wave plates 12a to 12h as described above, and the holding mechanism serving as a light shielding member is not provided, the fly Even on the incident surface of the eye lens 14, it is possible to substantially prevent deterioration in illuminance uniformity of illumination light. As a result, it is possible to substantially prevent deterioration in illuminance uniformity of illumination light on the reticle R.

  Accordingly, the half-wave plates 12a to 12h are configured so as not to have a substantial gap at each boundary portion and without having a holding mechanism that serves as a light shielding member. In order to eliminate the non-uniform illuminance of the illumination light on the first object (reticle R) caused by the polarization conversion members (half-wave plates 12a to h), the holding mechanisms 13a to 13h that are held outside the optical path, It can be seen that it constitutes at least a part of the illuminance non-uniformity eliminating means.

  Here, the fact that the gap is not substantially generated means that, for example, the gap generated at each boundary portion of the half-wave plates 12a to 12h is about 3% or less of the outer radius r0. By satisfying this condition, it is possible to reduce the light shielding effect associated with the gap and the adverse effect on the imaging characteristics of illumination light that does not have a preferred polarization direction leaking from the gap to a practically satisfactory level. is there.

  Note that means for eliminating the non-uniformity of the illuminance distribution of the illumination light on the reticle R caused by the boundary portion of the polarization conversion member is not limited to the above-described method. For example, FIGS. As shown in B), a plurality of half-wave plates 120a, 120b, 120c, 120d, 120e, 120f, 120g, and 120h may be held by a transparent substrate 120o that is transparent to illumination light such as quartz glass. good.

  FIG. 3A is a top view showing a plurality of half-wave plates 120a to 120h pasted on such a transparent substrate 120o, and FIG. 3B is a cross-sectional view taken along line A- in FIG. It is sectional drawing showing the cross section in A 'part. This sticking uses, for example, a technique such as so-called optical contact, but can be attached using an adhesive or the like that is transparent to the exposure light as necessary.

  The direction of each of the reference directions indicated by the white arrows shown in each part of the half-wave plates 120a to 120h in FIG. 3A is the half-wave plate 12a shown in FIG. It coincides with the direction of the reference direction of the corresponding position among ˜h. Therefore, also in this example, when the illumination light that is X-polarized light is incident on the half-wave plates 120a to 120h held on the substrate 120o, the illumination light is practically centered on the optical axis AX2. Is converted into linearly polarized light that coincides with the circumferential direction of the circle, and then emitted.

  Further, the conditions to be satisfied by the inner radius ri2 and the outer radius ro2 of the half-wave plates 120a to 120h shown in FIG. 3B are the inner radius ri and the outer radius in the above example shown in FIG. It is the same as the condition to be satisfied by ro.

  Also in this example, the half-wave plates 120a and 120b may be made of quartz glass instead of the half-wave plate, or may be omitted, as in the case of the above embodiment. . In the case of this example, quartz glass or the like having the same thickness as that of the half-wave plates 120a to 120h is also bonded in the vicinity of the optical axis AX2, that is, in the region of the radius ri2 centered on the optical axis AX2. be able to.

  Even in the configuration as in this example, there is virtually no problem with the light-blocking properties of the boundary portions of the half-wave plates 120a to 120h and the adverse effect on the imaging characteristics of illumination light that is not in the preferred polarization direction leaking from the boundary portions. It is possible to reduce the illuminance unevenness of the illumination light on the first object (reticle R) to at least part of the illuminance nonuniformity eliminating means. Can see.

  By the way, the half-wave plate of each said example can be comprised, for example with the crystal | crystallization which is a uniaxial crystal. As for the refractive index of quartz, ArF excimer laser light having a wavelength of 193 nm has an ordinary ray refractive index of 1.6638 and an extraordinary ray refractive index of 1.6774. The wavelengths of ordinary rays and extraordinary rays in the quartz are 116.001 nm and 115.056 nm, respectively, which are obtained by dividing the wavelength in vacuum (193 nm) by the respective refractive indexes. Each time, an optical path difference of 0.945 nm is formed between the two light beams. Therefore, in order to construct a half-wave plate, the thickness of the crystal is set to 7.12 μm, which corresponds to a thickness that proceeds by 61.4 (= 116.001 / 2 / 0.945) wavelengths. Good. Also, a half-wave plate can be formed using a crystal having a thickness of (2n + 1) × 7.12 μm (n is a natural number) that is an odd multiple of this thickness.

  In order to hold the half-wave plate as shown in FIGS. 2A and 2B, a certain amount of thickness is required. In this case, the half-wave plates 12a to 12h are used. It is preferable to increase the thickness and strength as an odd multiple of the above thickness. On the other hand, when the holding method shown in FIGS. 3 (A) and 3 (B) is adopted, the quartz having any thickness described above can be used.

  In addition, even when the methods shown in FIGS. 2A and 2B are employed, a half-wave plate having a structure in which quartz is bonded onto quartz glass or the like can also be employed.

  Further, the configuration of the half-wave plate is not limited to the above-mentioned quartz, and other birefringent materials may be used, and the birefringence plate is formed using intrinsic birefringence of fluorite. You can also. In addition, a material that has birefringence by applying stress to a material such as synthetic quartz that does not have birefringence can be used. Even in that case, the thickness for forming the half-wave plate can be calculated using the above method from the refractive index of the material with respect to the ordinary ray and the extraordinary ray.

  If the pattern formed on the reticle R is very fine, or if the standard required for the pattern dimension of the pattern to be exposed and transferred on the wafer W is extremely strict, as described above, the ½ wavelength is used. There may be a case where the illuminance uniformity of the illumination light on the reticle R cannot be sufficiently achieved only by taking measures so that light is not substantially blocked at each boundary portion of the plates 12a to 12h.

  Therefore, in such a case, the illuminance distribution caused by the boundary portions of the half-wave plates 12a to 12h among the lens elements constituting the fly-eye lens 14 on the exit surface 14b of the fly-eye lens 14. Is provided with a light shielding member for shielding the illumination light emitted from the lens element where the non-uniformity occurs, and the illuminance nonuniformity of the illumination light quantity on the reticle R caused by the boundary portion of the half-wave plates 12a to 12h. It is also possible to adopt a configuration that completely prevents

  Hereinafter, this configuration will be described with reference to FIGS. 4, 5, and 6. FIG. 4A is a diagram showing the configuration of the half-wave plates 12a to 12h. Details of the half-wave plates 12a to 12h are shown in FIG. 2A or FIG. 3A. It is the same as that of ~ h etc. structure. At this time, light shielding properties are produced at the boundary portions of the half-wave plates 12a to 12h, although slightly.

  FIG. 4B shows a state where a dimming portion caused by the boundary portion of the half-wave plate is generated on the fly-eye lens incident surface 14a as viewed from the −Y direction (upstream side of illumination light). FIG. E1, E2, E3, E4, E5, E6, E7, and E8, which are the boundary portions of the half-wave plates 12a to 12h, respectively reduce the illumination light to the fly-eye lens incident surface 14a. Optical regions S1, S2, S3, S4, S5, S6, S7, and S8 are formed. Further, a dimming region Sc corresponding to a boundary portion on the inner side (near the optical axis AX2) of each of the half-wave plates 12a to 12h is formed on the same surface 14a.

  FIG. 5A is a cross-sectional view of each of the half-wave plates 12a to 12h and the fly-eye lens 14 at the position of the line BB ′ shown in FIGS. 4A and 4B. FIG. The dimming portions S5 and S4 due to the boundary portions E4 and E5 are formed on the elements 144 and 145 which are lens elements constituting the fly-eye lens 14, respectively, at the B-B 'line segment position. Therefore, the illumination light of the incident surfaces of the elements 144 and 145 has an uneven illuminance distribution.

  Here, the effect | action of the fly eye lens 14 is demonstrated easily using FIG. 6 (A) and FIG. 6 (B). These drawings are diagrams for explaining the influence on the illuminance distribution on the reticle R when the illuminance uniformity on the incident surface 14a of the fly-eye lens 14 is extremely nonuniform within the predetermined element as described above. is there.

  As shown in FIG. 6A, the illumination light applied to the fly-eye lens entrance surface 14a is condensed on the exit surface 14b side by the condensing action (lens action) of each lens element. Then, the light is emitted from each element as a divergent light beam, and the light is superimposed and irradiated on an irradiated object (first object) such as the reticle R1. That is, the entrance surface of each lens element of the fly-eye lens 14 and the reticle R1 are in an imaging relationship, and the illumination light amount distribution on the illumination field ILa of the reticle R1 is due to the averaging effect made by the superimposing action. It will be made uniform.

  However, as shown in FIG. 6B, when the light reducing portion S5 formed on the lens element 145 is a light-shielding portion that is relatively steep and has a large decrease in the amount of light, an averaging effect by the fly-eye lens 14 is obtained. Even in this case, the illumination light quantity distribution ILR1 on the illumination field ILa on the reticle R1 has the light reduction part S5R generated by the light reduction part S5, and the illuminance cannot be made completely uniform. .

  Therefore, as shown in FIG. 5 (B), light shielding members B4, B5, etc. are provided in the vicinity of the fly-eye lens exit surface 14b, and the lens elements 144, 145, etc., deteriorate the illuminance uniformity of illumination on the reticle R1. It can also be set as the structure which shields illumination light.

  The light shielding members B4, B5 and the like are desirably arranged in the vicinity of the exit surface 14b of each fly-eye lens element corresponding to the above-described dimming portions S1 to 8 and the dimming portion Sc. Therefore, it is desirable to arrange the light shielding members B1, B2, B3, B4, B5, B6, B7, B8, and Bc as shown in FIG. FIG. 5B is a view of the light shielding members S1 to 8 and the light shielding member Sc and the fly-eye lens exit surface 14b as viewed from the + Y direction (downstream side of the illumination light).

  The light shielding members S1 to 8 and the light shielding member Sc shield the illumination light from the lens element that deteriorates the illuminance uniformity of the illumination light on the reticle R1 due to the polarization conversion member, and the illumination intensity of the illumination light on the reticle R1 is uniform. In order to contribute to the improvement of the property, it can be seen that at least a part of the non-uniform illuminance eliminating means is configured.

  By providing the light shielding members S1 to 8 and Sc, the illuminance non-uniformity of the illumination light on the reticle R1 due to the polarization conversion member can be completely prevented, so that the polarization conversion members (half-wave plates 12a to 12h). ) Holding method or the like is not limited to the above-described configuration, and various configurations can be employed. However, in order to minimize the width of the dimming portions E1 to 8 and Ec generated on the fly-eye lens incident surface 14a, minimize the number of fly-eye lens elements to be shielded, and minimize the loss of illumination light quantity. As a method for holding the polarization conversion member, it is preferable to employ the method described above.

  The arrangement positions of the light shielding members S1 to 8 and Sc are not limited to the vicinity of the exit surface 14b of the fly-eye lens 14 as described above, but between the fly-eye lens 14 and the reticle R in the illumination optical system ILS. When there is a conjugate plane of the exit surface 14b (that is, the pupil plane 15), it may be arranged on the conjugate plane.

  As shown in FIG. 6B, the deterioration of illuminance uniformity on the reticle R1 occurs because the illuminance distribution of illumination light in one lens element of the fly-eye lens 14 changes sharply. It is. That is, when the illumination light amount distribution on the incident surface 14a of one lens element 145 or the like is so steep that it cannot be averaged by illumination light from other lens elements in the reticle R1, the illuminance on the reticle R1 The deterioration of uniformity cannot be ignored.

  Therefore, the illumination optical system ILS is configured to have a uniform illumination intensity of the illumination light on the reticle R1 even by adopting a configuration in which the light quantity distribution does not change sharply on the entrance surface 14a of the fly-eye lens 14. Is also possible.

  Specifically, the configuration of the illumination optical system ILS, in particular, the configuration of the zoom optical systems 5 and 6, the diffractive optical element 9a, the relay lens 11, the polarization conversion members 12a to 12h and the fly-eye lens 14 in FIG. The illumination light beam IL at the positions of the polarization conversion members 12a to 12h should have a certain degree of divergence. As a result, the boundary portions (dimming portions) of the polarization conversion members (half-wave plates) 12a to 12h are divergent from the light flux and the distance from the polarization conversion members 12a to 12h to the fly-eye lens incident surface 14a. Due to this interaction, the light is projected to the fly-eye lens incident surface 14a with a certain degree of blur.

  Then, as shown in FIG. 6B, when the blur width of the light reducing portion S55 is set to be equal to or larger than the width of each lens element 145 and the like constituting the fly-eye lens 14, the light amount distribution ( It is possible to sufficiently reduce the steepness of the degree of dimming), and hence it is possible to maintain good illuminance uniformity of illumination light on the reticle R1. Here, the blur width of the dimming portion S55 refers to, for example, a half width, based on the average value of the average illumination light amount Ilin1 on the incident surface 14a of the fly-eye lens 14 and the darkest portion light amount of the dimming portion S55. This is the slice width when the light-reducing part S55 is sliced.

  Accordingly, by optimizing the configuration of the illumination optical system ILS and providing the illumination light beam IL at the positions of the polarization conversion members 12a to 12h with a certain degree of divergence, the dimming portion S55 on the incident surface 14a of the fly-eye lens. The structure that increases the blur width of the illumination is also considered to constitute at least a part of the illuminance nonuniformity eliminating means for eliminating the illuminance nonuniformity of the illumination light on the first object (reticle R) caused by the polarization conversion member. Can do.

  It goes without saying that this configuration can be employed in combination with the other illuminance non-uniformity elimination means described above.

  As described above, according to the present invention, the illumination light distributed on the incident surface of the fly-eye lens 14a in the illumination optical system ILS is distributed in a specific annular region between a predetermined inner radius and a predetermined outer radius. The polarization state of the illumination light can be linearly polarized light whose polarization direction substantially coincides with the circumferential direction of a circle centered on the optical axis AX2 of the illumination optical system ILS.

  Since these polarization states are preserved even in the light beam emitted from the fly-eye lens 14, the illumination light distributed there also on the illumination optical system pupil plane 15 on which the exit surface 14b of the fly-eye lens 14 is arranged. Among these, the polarization state of the illumination light distributed in the specific annular zone region between the predetermined inner radius and the predetermined outer radius is expressed by a circle whose polarization direction is substantially centered on the optical axis AX2 of the illumination optical system ILS. The linearly polarized light coincides with the circumferential direction.

  In addition, the illumination light distributed in a position away from the illumination optical system optical axis AX2 by a predetermined distance on the illumination optical system pupil plane 15 is irradiated onto the reticle R with a predetermined incident angle. This will be described with reference to FIGS. 7A, 7B, and 7C.

  FIG. 7A is a perspective view schematically showing the relationship between the pupil plane 15 of the illumination optical system ILS in FIG. 1 and the reticle R. The relay lens 16, the condenser lenses 18, 20, etc. in FIG. Is omitted. On the reticle R, there are fine patterns PX whose longitudinal direction is parallel to the Y direction and having periodicity in the X direction, and fine patterns PY whose longitudinal direction is parallel to the X direction and having periodicity in the Y direction. Is formed.

  FIG. 7B shows a part of a cross-sectional view in the ZX plane of the schematic diagram shown in FIG. In the specific annular zone IL0 on the pupil plane 15 in FIG. 7A, the illumination light distributed in the ILL portion at the left end in the drawing is centered on the incident angle φ as the illumination light ILL1 in FIG. 7B. Is incident on the reticle R while being inclined by a predetermined angular range. The sine value of this incident angle φ is proportional to the distance of the center position of the annular zone IL0 from the illumination system optical axis AX41.

  As described above, in the illumination optical system (illumination optical apparatus) according to the present invention, the illumination light distributed in the specific annular zone IL0 on the pupil plane 15 is linearly polarized light approximately parallel to the circumferential direction of the specific annular zone IL0. Therefore, the polarization state EF1 of the illumination light ILL1 is so-called S-polarized light. Here, S-polarized light is synonymous with S-polarized light defined in general optics, and includes a traveling direction of the illumination light ILL1 and a normal line to the reticle R that is an object to be irradiated (that is, the illumination optical system optical axis AX41). This is polarized light whose polarization direction is perpendicular to the plane, that is, the ZX plane.

  By illuminating the pattern PX having the longitudinal direction in the Y direction and the periodicity in the X direction with the incident azimuth, the incident angle φ, and the polarization state EF1 of the illumination light ILL1, it is projected through the projection optical system 25. The contrast of the image of the pattern PX can be improved. However, since the reason is explained in Patent Document 1 and the like, the explanation is omitted here.

  Although illustration is omitted for convenience of explanation, it goes without saying that in FIG. 7B, the illumination light emitted from the annular zone ILR is irradiated on the reticle R also from the upper right. The polarization state is also S-polarized light.

  FIG. 7C shows a part of a cross-sectional view in the YZ plane of the schematic diagram shown in FIG. In the annular zone IL0 on the pupil plane 15 in FIG. 7A, the illumination light distributed in the ILD portion at the lower end in the drawing is centered on the incident angle φ as the illumination light ILD1 in FIG. 7C. Is incident on the reticle R while being inclined by a predetermined angular range.

  Since the illumination light distributed at the lower end ILD in the figure in the specific annular zone IL0 on the pupil plane 15 is also linearly polarized light substantially parallel to the circumferential direction of the specific annular zone IL0, the polarization state of the illumination light ILD1 EF2 is also S-polarized light as described above. The incident azimuth, the incident angle φ, and the polarization state EF2 of the illumination light ILL1 are suitable for the pattern PY having a length in the X direction and periodicity in the Y direction, and is projected through the projection optical system 25. The contrast of the image of the pattern PY can be improved.

  Note that the left end portion (−X direction end portion) ILL, the right end portion (+ X direction end portion) ILR, and the lower end portion in the specific annular zone IL0 on the pupil plane 15 in FIG. (−Y direction end portion) ILD and the like include both ends in the X direction in FIG. 2A and the like among the polarization conversion members (1/2 wavelength plates) 12a to 12h shown in FIG. This corresponds to the illumination light transmitted through the members corresponding to the polarization conversion members 12a, 12b, 12c, and 12d disposed at both ends in the Y direction.

  On the other hand, on the reticle R, as shown in FIG. 7A, not only the pattern whose longitudinal direction coincides with the X direction or the Y direction, but also the longitudinal direction rotated approximately 45 degrees from the X direction and the Y direction. There are cases where such patterns exist. For such a pattern, the polarization conversion members 12e, 12f, 12g, and 12h shown in FIG. 2A and the like are particularly effective.

  However, if the particularly important pattern among the patterns existing on the reticle R, for example, the finest pattern is limited to a pattern having a length in the X direction or the Y direction, it is more effective for these patterns. In order to increase the illumination light from the polarization conversion members 12a, 12b, 12c, and 12d, which is, relative to the illumination light from the other polarization conversion members 12e, 12f, 12g, and 12h, FIG. It is also possible to change the area ratio of the polarization conversion members 12a to 12h.

  That is, the center angle of the polarization conversion members 12a, 12b, 12c, and 12d is increased instead of the polarization conversion members 12a to 12h arranged at equal angles around the optical axis AX2 shown in FIG. The arrangement of the polarization conversion members 12e, 12f, 12g, and 12h may be changed so as to reduce the area by reducing the central angle.

  Note that the number of polarization conversion members 12a to 12h, that is, the number of divisions centered on the optical axis AX2 with respect to the specific annular zone is not limited to the above eight divisions, but is divided into more regions and more Needless to say, the polarization conversion members may be arranged side by side.

  By the way, in the above embodiment, it demonstrated on the assumption that the illumination light quantity distribution formed in the pupil plane 15 of the illumination optical system ILS of FIG. 1 is the above-mentioned specific annular zone area, that is, applied to annular illumination. However, the illumination conditions that can be realized by the illumination optical apparatus and the projection exposure apparatus of the present invention are not necessarily limited to annular illumination. That is, the polarization conversion members 12a to 12h set the polarization state of the illumination light distributed in the specific annular zone in the pupil plane 15 of the illumination optical system to the desired polarization state. Is converted into illumination light mainly composed of linearly polarized light having a polarization direction parallel to the circumferential direction of the specific annular zone, even when limited to a specific partial region within the specific annular zone. Needless to say, you can.

  In this way, in order to collect the illumination light only in a specific region within the specific annular zone, the diffractive optical element 9a in FIG. 1 is replaced, and diffracted light (illumination) generated from another diffractive optical element. Light) may be concentrated in specific discrete regions on the polarization conversion members 12a to 12h. The locations where the illumination light is concentrated are, for example, two locations in the polarization conversion members 12c and 12d in FIG. 2A. Of course, the illumination light may be concentrated at any location on any polarization conversion member. The light may be condensed at a position straddling the members a to h.

  Also, the number of condensing positions may be four. The selection of the position and the number may be determined according to the shape of the pattern to be exposed on the reticle R.

  By the way, the illumination light distributed outside the condensing position is not suitable for the exposure of the pattern to be exposed, and therefore it may be preferable that the light amount distribution is substantially zero. On the other hand, depending on the manufacturing error of the diffractive optical element 9a and the like, diffracted light (hereinafter referred to as "error light") is generated from the diffractive optical element 9a and the like in a direction other than the desired direction. The illumination light may be distributed. Therefore, for example, a further stop may be provided on the exit surface side of the fly-eye lens 14 in FIG. 1 to block this error light. As a result, the illumination light amount distribution other than the plurality of light condensing regions can be completely zero.

  However, there are patterns other than the exposure target pattern on the reticle R, and the error light may be effective for image formation of patterns other than the exposure target. In some cases, the light amount distribution need not be zero.

  In the above embodiment, the illumination light applied to the reticle R1 is assumed to be annular illumination or modified illumination and S-polarized light with respect to the reticle R. However, actual illumination optics is described. In the apparatus and the projection exposure apparatus, it is necessary that the illumination condition and the polarization state of the irradiated object (first object) such as the reticle R can be freely changed to some extent.

  Here, the illumination condition can be changed by changing the illumination σ value or changing to the annular illumination, dipole illumination, or quadrupole illumination by replacing the diffractive optical elements 9a and 9b and the zoom optical systems 5 and 6 described above. Is possible. Thereby, for example, the σ value of the illumination light beam can be reduced to a small σ illumination of about 0.4 or less.

  Such small σ illumination light passes through the vicinity of the optical axis AX2 in FIG. 2A without passing through the polarization conversion members 12a to 12h as shown in FIG. It is not affected by the polarization conversion effect. Therefore, the illumination light IL is incident on the reticle R while maintaining the polarization state when the illumination light IL is emitted from the light source 1 such as a laser. However, depending on the pattern type and directionality of the reticle R1, linearly polarized light in the Y direction is used. In some cases, light is preferred, and in some cases, randomly polarized light is preferred.

  Therefore, in the illumination optical apparatus / projection exposure apparatus of the present invention, the polarization control member 4 is provided in the illumination optical system ILS, so that the polarization state of the illumination light irradiated on the reticle R1 can be changed.

  The polarization control member 4 is, for example, a half-wave plate that can rotate around the optical axis AX1 of the illumination optical system, and can change the transmitted illumination light to X-polarized light or Y-polarized light by changing the arrangement angle. To do. As a result, the polarization state of the small σ illumination light on the reticle R1 can be switched between X-polarized light and Y-polarized light.

  Alternatively, as the polarization control member 4, an element that eliminates the polarization property of the illumination light can be disposed so as to be removable from the illumination system light beam IL. As a result, the illumination optical apparatus / projection exposure apparatus of the present invention can also cope with the case where random polarization illumination is required when illuminating the reticle R1. In addition, as an element which cancels | polarizes light, the wavelength plate and optical rotation member from which the thickness differs according to the position in a surface can be used, for example. As an alternative, the illumination light is made circularly polarized using a quarter wave plate or the like, so that illumination light substantially equivalent to random polarization may be used in terms of the imaging characteristics of the pattern on the wafer W. .

  As described above, even when the illumination light is randomly polarized, if the polarization conversion member of the present invention is composed of the half-wave plates 12a to 12h, the polarization state of the substantially random illumination light is changed to random. There is no conversion to any other state. However, the polarization conversion members 12a to 12h are used when using a large sigma illumination, for the purpose of further improving the illuminance non-uniformity of the illumination light on the reticle R generated due to the polarization conversion member and remaining slightly. It can also be retracted outside the light path of the lighting concept.

  For example, the holding mechanism 13 holding the polarization conversion members 12a and 12b in FIG. 1 is further held by an exchange mechanism (not shown), and the polarization conversion members 12a and 12b are held together with the holding mechanism 13 by driving the exchange mechanism. It can be realized by a loading / unloading mechanism that retracts outside the optical path of the illumination optical system.

  Alternatively, the polarization changing members 12a to 12h are radiated with respect to the optical axis AX2, for example, to the holders 13a to 13h holding the polarization changing members 12a to 12h shown in FIG. 2A and FIG. It is also possible to provide a movable mechanism that can move in the direction so that the polarization changing members 12a to 12h can be retracted outside the illumination optical path.

  In the above embodiment, the laser light source as the light source 1 emits linearly polarized light polarized in the X direction, but the polarization state of the illumination light beam IL emitted from the light source is not limited to this. . For example, a light source that emits linearly polarized light polarized in the Y direction can be used by converting it into linearly polarized light polarized in the X direction using a half-wave plate or the like. If the light source emits light, it can be used by converting it into linearly polarized light polarized in the X direction with a quarter-wave plate or the like. However, the illumination light emitted from the light source 1 is preferably illumination light that can be converted into linearly polarized light by a wave plate or the like, that is, illumination light in a single polarization state.

  However, it is not necessary to have a completely single polarization state. For example, a light source that emits linearly polarized light having a polarization ratio of about 80% or more is sufficient. If the light source has a lower polarization ratio than this, the effect of the present invention that improves the contrast of the projected image of the fine pattern using linearly polarized light cannot be sufficiently obtained.

  For example, in the case where the light source 1 emits circularly polarized illumination light, a configuration in which the illumination light is guided to the polarization conversion member 12a in FIG. It can also be. In that case, the illumination light which permeate | transmitted each polarization conversion member 12a-h can be made into the said desired polarization state by using a quarter wavelength plate as polarization conversion member 12a-h.

  As described above, the polarization conversion members 12a to 12h of the present invention are not limited to the ½ wavelength plate, and can use other wavelength plates according to the polarization state of the illumination light. Further, in addition to the wave plate, a material having optical rotation such as quartz can be used. In this case, for each of the plurality of polarization conversion members, the illumination light transmitted through each polarization conversion member is made from an optical axis using materials having different dextrorotatory or levorotatory optical rotation properties or materials having different thicknesses. It may be converted into linearly polarized light having a polarization direction parallel to the circumferential direction of the circle centered on AX2.

  Therefore, the polarization conversion members 12a to 12h of the present invention can use various optical members without being limited to the wave plate.

  Next, an example of a semiconductor device manufacturing process using the projection exposure apparatus of the above embodiment will be described with reference to FIG.

  FIG. 8 shows an example of a semiconductor device manufacturing process. In FIG. 8, a wafer W is first manufactured from a silicon semiconductor or the like. Thereafter, a photoresist is applied on the wafer W (step S10), and in the next step S12, a reticle (provisionally R1) is loaded on the reticle stage of the projection exposure apparatus of the above embodiment (FIG. 1). The wafer W is loaded on the wafer stage, and the pattern of the reticle R1 (represented by the symbol A) is transferred (exposed) to all the shot areas SE on the wafer W by a scanning exposure method. At this time, double exposure is performed as necessary.

  The wafer W is, for example, a wafer having a diameter of 300 mm (12 inch wafer), and the size of the shot area SE is, for example, a rectangular area having a width of 25 mm in the non-scanning direction and a width of 33 mm in the scanning direction. Next, in step S14, a predetermined pattern is formed in each shot region SE of the wafer W by performing development, etching, ion implantation, and the like.

  Next, in step S16, a photoresist is applied on the wafer W, and then in step S18, a reticle (provisionally R2) is loaded onto the reticle stage of the projection exposure apparatus of the above-described embodiment (FIG. 1). Then, the wafer W is loaded on the wafer stage, and the pattern of the reticle R2 (represented by the symbol B) is transferred (exposed) to each shot area SE on the wafer W by a scanning exposure method. In step S20, a predetermined pattern is formed in each shot region of the wafer W by performing development and etching of the wafer W, ion implantation, and the like.

  The above exposure process to pattern formation process (steps S16 to S20) are repeated as many times as necessary to manufacture a desired semiconductor device. Then, a semiconductor device SP as a product is manufactured through a dicing process (step S22) for separating each chip CP on the wafer W one by one, a bonding process, a packaging process, and the like (step S24). .

  According to the device manufacturing method of this example, since the exposure is performed by the projection exposure apparatus of the above-described embodiment, in the exposure process, the reticle in a predetermined polarization state with increased use efficiency of illumination light (exposure beam) is used. Can illuminate. Accordingly, since the resolution and the like of a periodic pattern with a fine pitch are improved, a highly integrated and high performance semiconductor integrated circuit can be manufactured at a high throughput and at a low cost.

  In the projection exposure apparatus of the above embodiment, an illumination optical system composed of a plurality of lenses and a projection optical system are incorporated in the exposure apparatus main body and optical adjustment is performed, so that a reticle stage or wafer stage composed of a large number of mechanical parts is provided. It can be manufactured by attaching to the exposure apparatus main body, connecting wiring and piping, and further performing general adjustment (electrical adjustment, operation check, etc.). The projection exposure apparatus is preferably manufactured in a clean room in which the temperature, cleanliness, etc. are controlled.

  Further, the present invention can be applied not only to a scanning exposure type projection exposure apparatus but also to a batch exposure type projection exposure apparatus such as a stepper. The magnification of the projection optical system used may be not only a reduction magnification but also an equal magnification or an enlargement magnification. Furthermore, the present invention can be applied to an immersion type exposure apparatus disclosed in, for example, International Publication (WO) No. 99/49504.

  Further, the use of the projection exposure apparatus of the present invention is not limited to the exposure apparatus for manufacturing a semiconductor device, but for example, a liquid crystal display element formed on a square glass plate or a display apparatus such as a plasma display. The present invention can be widely applied to an exposure apparatus and an exposure apparatus for manufacturing various devices such as an image sensor (CCD or the like), a micromachine, a thin film magnetic head, and a DNA chip. Furthermore, the present invention is also applied to an exposure process (exposure apparatus) when manufacturing a mask (a photomask including an X-ray mask, a reticle, etc.) on which a mask pattern of various devices is formed using a photolithography process. be able to.

  In addition, this invention is not limited to the above-mentioned embodiment, Of course, a various structure can be taken in the range which does not deviate from the summary of this invention.

  According to the device manufacturing method of the present invention, the utilization efficiency of the exposure beam (illumination light) can be increased, and a predetermined pattern can be formed with high accuracy. Therefore, various devices such as semiconductor integrated circuits can be manufactured with high accuracy and high processing capability (throughput).

  R ... reticle, W ... wafer, ILS ... illumination optical system, AX2 ... illumination system optical axis, 1 ... light source, 4 ... polarization control member, 9a, 9b ... diffractive optical element, 12a, 12b ... polarization conversion member, 13 ... polarization Control member holding mechanism, 14 ... fly-eye lens, 25 ... projection optical system.

Claims (14)

An illumination optical apparatus comprising an illumination optical system that illuminates a first object based on light of a substantially single polarization state from a light source,
A polarization conversion member that converts a polarization state of the illumination light distributed in a specific annular zone area that is a predetermined annular zone in a predetermined plane perpendicular to the optical axis of the illumination optical system into a predetermined polarization state; ,
The polarization conversion member includes a plurality of polarization conversion elements disposed at different positions in a plane perpendicular to the optical axis of the illumination optical system,
The illumination optical device, wherein the polarization conversion element is formed of a material having optical rotation. An illuminance equalizing member for substantially equalizing the illuminance of the illumination light irradiated on the first object;
The illumination optical apparatus according to claim 1, wherein the polarization conversion member is disposed closer to the light source than the illuminance uniforming member.   The illumination optical apparatus according to claim 2, wherein the illuminance equalizing member is a fly-eye lens.   4. The illumination optical apparatus according to claim 1, wherein the optically rotating material is quartz.   5. The illumination optical apparatus according to claim 1, wherein the plurality of polarization conversion elements formed of a material having an optical rotation have different thicknesses.   The predetermined polarization state of the illumination light distributed in the specific ring zone region is a polarization state mainly composed of a linearly polarized light in a circumferential direction around the optical axis of the illumination optical system. The illumination optical apparatus according to any one of claims 1 to 5.   The illumination optical apparatus according to any one of claims 1 to 6, wherein the predetermined surface is a Fourier transform surface for the first object in the illumination optical system.   The illumination according to any one of claims 1 to 7, further comprising a light beam limiting member that limits the illumination light applied to the first object to a light beam distributed in the specific ring zone region. Optical device.   The illumination optical device according to claim 8, wherein the light flux limiting member further restricts the light flux to a plurality of substantially discrete regions within the specific annular zone region.   The illumination optical device according to claim 8 or 9, wherein the light flux limiting member includes a diffractive optical element provided between the light source and the polarization conversion member.   11. The illumination optical apparatus according to claim 1, further comprising an attachment / detachment mechanism that retracts the polarization conversion member out of an optical path of the illumination light.   A projection optical system that includes the illumination optical apparatus according to any one of claims 1 to 11 as an illumination optical apparatus that illuminates a first object, and projects a pattern image on the first object onto a second object. A projection exposure apparatus comprising:   An exposure method comprising: exposing a photoconductor as the second object with an image of a mask pattern as the first object using the projection exposure apparatus according to claim 12. A device manufacturing method including a lithography process,
A device manufacturing method, wherein a pattern is transferred to a photoconductor using the exposure method according to claim 13 in the lithography process.

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