WO2000067303A1

WO2000067303A1 - Exposure method and apparatus

Info

Publication number: WO2000067303A1
Application number: PCT/JP2000/002761
Authority: WO
Inventors: Takashi Aoki; Naomasa Shiraishi
Original assignee: Nikon Corporation
Priority date: 1999-04-28
Filing date: 2000-04-27
Publication date: 2000-11-09
Also published as: AU4143000A

Abstract

An exposure method for conducting exposure with high, uniform illuminance by illuminating light (IL) for exposure even when the illuminating light (IL) is a laser beam having a wavelength in the vacuum ultraviolet region. The illuminating light (IL) which is a linearly-polarized F2 laser beam emitted from a laser light source (1) passes through a prism (3), an oscillating mirror (4), bly-eye lenses (5A, 5B), and a condenser lens (9) and illuminates a reticle (R). The pattern on the reticle (R) is transferred onto a wafer (W) through a projection optical system (PL). The prism (3) is made of a crystal of magnesium fluoride (MgF2) which is a birefringent glass material transparent to the F2 laser beam. The prism (3) has a thickness gradually varying in the direction perpendicular to the optical axis of the illuminating light (IL) and is so disposed that it exhibits birefringence with respect to the illuminating light (IL). The polarized state of the illuminating light (IL) is continuously changed in a predetermined direction in a plane perpendicular to the optical axis.

Description

Description Exposure method and apparatus

The present invention relates to an exposure method used when manufacturing a microdevice such as a semiconductor integrated circuit, an imaging device (CCD or the like), a liquid crystal display, a plasma display, or a thin-film magnetic head by using a lithography technique. Background art

In recent years, as circuit patterns of semiconductor integrated circuits and the like have become finer, the wavelength of exposure illumination light (exposure light) used in an exposure apparatus such as a stepper has been becoming shorter and shorter year by year. In other words, KrF excimer laser light (wavelength: 248 nm) has become the mainstream of exposure light instead of the i-line (wavelength: 365 nm) of mercury lamps, which has been mainly used in the past. In addition, short-wavelength ArF excimer laser light (wavelength: 193 nm) in the vacuum ultraviolet region is being put into practical use. In addition, for the purpose of further shortening the wavelength of exposure light, use of a halogen molecule laser such as an F ₂ laser (wavelength: 157 nm) has been attempted. As described above, in the exposure apparatus, laser light is used as exposure light. Generally, laser light is light that is strongly linearly polarized and has high coherence. Therefore, when laser light is used as the exposure light, speckle-like interference fringes called speckles are generated in the illumination area. The occurrence of this speckle makes the illuminance distribution of the exposure light non-uniform and deteriorates the uniformity of the line width of a circuit pattern formed on a substrate to be exposed such as a wafer. Speed, etc.) It may cause malfunction.

For this reason, for example, in a conventional exposure apparatus using KrF excimer laser light as exposure light, the uniformity of the illuminance distribution of the exposure light is deteriorated by arranging a quartz prism in the illumination optical system. Had been prevented. In this case, since the crystal has birefringence, when the exposure light passes through the prism of the crystal, the speed of the ordinary ray and the extraordinary ray in the prism becomes different due to the birefringence. Therefore, by arranging a quartz prism with a gradually changing thickness in the optical path of the exposure light, the same effect as when a 1Z 4 wavelength plate or 1Z 2 wavelength plate is locally arranged, or those effects An intermediate effect can be obtained, and the polarization state of the exposure light emitted from the prism can be partially changed. For this reason, the spatial coherence (space coherency) of the exposure light is reduced, and the occurrence of speckle can be suppressed.

As described above, in the conventional exposure apparatus, a quartz prism is arranged in the optical path of the exposure light to reduce the coherence of the exposure light. However, ordinary crystals have a large decrease in transmittance for vacuum ultraviolet light with a wavelength of about 200 nm or less. Therefore, if the exposure light is about the ArF excimer laser light, the crystal can be used by taking measures such as prolonging the exposure time against a decrease in illuminance, but the throughput will be significantly reduced. There is an inconvenience. And, the crystal becomes difficult to use to greatly reduced transmittance with respect to a shorter wavelength of F ₂ laser light. Therefore, when laser light in the vacuum ultraviolet region is used as the exposure light, it is difficult to reduce the coherence while keeping the illuminance of the exposure light high and to suppress the occurrence of speckle. It has been difficult to prevent deterioration of the uniformity of the illuminance distribution.

In view of such a point, the present invention provides a method for controlling the illuminance of the illumination light even when using light having a coherence with a wavelength of about the vacuum ultraviolet region as the exposure illumination light. It is a first object of the present invention to provide an exposure method that can increase the uniformity of the illuminance distribution of the illumination light without significantly reducing the illuminance.

A second object of the present invention is to provide an illumination optical device and an exposure device capable of performing such an exposure method.

Further, the present invention seeks a material having a birefringence effect and a high transmittance with respect to illumination light having a wavelength in the vacuum ultraviolet range, and an illumination optical device capable of performing such an exposure method using this material. The third purpose is to provide.

Still another object of the present invention is to provide a method for manufacturing such an exposure apparatus and a method for manufacturing a device using such an exposure method. Disclosure of the invention

A first exposure method according to the present invention is an exposure method for illuminating a mask (R) with illumination light and transferring the pattern of the mask onto a substrate (W), wherein the wavelength of the illumination light is about 180 nm. An optical element made of magnesium fluoride (MgF ₂ ) is placed on the optical path until the illumination light enters the mask, and a direction substantially perpendicular to the optical path of the illumination light Then, the polarization state of the illumination light is gradually changed.

According to the present invention, when the polarization state of the illumination light is a predetermined state such as linearly polarized light or circularly polarized light, the polarization state is gradually changed in a direction substantially perpendicular to the optical path. For example, by spatially and continuously changing the polarization state of the illumination light in at least one direction in a plane perpendicular to the optical axis of the illumination light, the spatial coherence of the illumination light ( Spatial coherency) is reduced. Therefore, the occurrence of scattering in the illumination area is suppressed, and the uniformity of the illuminance distribution is improved. Furthermore, by changing only the polarization state without substantially reducing the amount of illumination light, When using illumination light in the almost vacuum ultraviolet region with a wavelength of 200 nm or less to enhance resolution, exposure can be performed under favorable conditions that both high illuminance uniformity and high illuminance can be achieved. The entire pattern can be transferred onto the substrate with high line width uniformity and high throughput. In a second exposure method according to the present invention, in a method of illuminating a mask with coherent illumination light and exposing a substrate with the illumination light through the mask, the wavelength of the illumination light is set to 180 nm. In order to reduce the coherence of the illuminating light, the polarization state of the illuminating light is changed by an optical element made of magnesium fluoride prior to incidence on the mask. According to the present invention, similarly to the first exposure method, generation of speckles in the illumination area is suppressed, and the uniformity of the illuminance distribution is improved. In addition, since exposure can be performed under favorable conditions that both high illuminance uniformity and high illuminance can be achieved, the entire mask pattern is transferred onto the substrate with high line width uniformity and high throughput. be able to.

Next, a first illumination optical device according to the present invention is an illumination optical device (15) for illuminating a mask (W) with illumination light having a wavelength of 200 nm or less from a light source (1), On the optical path of the illuminating light between the light source (1) and the mask, the illuminating light is formed of a material that is transmissive and birefringent to the illuminating light, and intersects the optical axis of the illuminating optical device A prism (3) whose thickness changes gradually in the direction is arranged.

According to the present invention, the exposure method of the present invention can be performed. That is, since the prism is formed of a birefringent material, the prism is inclined in a plane perpendicular to the optical axis in a plane perpendicular to the optical axis. According to the position, the polarization state of the illumination light can be continuously changed in a direction perpendicular to the optical axis. Further, as a material of the prism, a wavelength of about 200 nm or less, that is, a relatively high transmittance even in a vacuum ultraviolet region. By using an optical glass material with an excessive ratio, the illuminance on the mask can be kept high. In this case, a crystal of magnesium fluoride (MgF ₂ ) can be used as a material having high transmittance and birefringence even in the vacuum ultraviolet region. Magnesium fluoride has a sufficiently high transmittance for ultraviolet light up to a wavelength of about 130 nm. In particular, when the wavelength is about 180 nm or less in the vacuum ultraviolet region, the transmittance of the conventionally used quartz is greatly reduced, and magnesium fluoride is effective.

Next, a second illumination optical device according to the present invention is an illumination optical device for illuminating a mask (R) with illumination light having a wavelength of 200 nm or less from a light source, and the illumination light from the light source is provided. A prism (which is made of a material that is transparent and birefringent to the illumination light, and whose thickness gradually changes in a direction intersecting the optical axis of the illumination optical device). 3), a vibrating member (4) for vibrating the illumination light passing through the prism, and an optical integray (5A, 5B) for forming a plurality of light source images from the illumination light passing through the vibrating member. And a condenser optical system (9) for guiding the illumination light emitted from the optical integrator to the mask.

According to the present invention, it is possible to improve the uniformity of the illuminance distribution of the illumination light as in the first illumination optical device. Further, by vibrating the vibrating member during illumination, the illuminance unevenness of the illumination light is reduced by the integration effect. In addition, the use of the optical integrator (homogenizer) allows the illumination light to be superimposed, thereby making the illuminance distribution of the illumination light more uniform.

Next, a first exposure apparatus according to the present invention is an exposure apparatus including the illumination optical device (15) of the present invention, and illuminates a mask (R) with illumination light from the illumination optical device. Transfers mask pattern onto substrate (W) It is. According to the first exposure apparatus of the present invention, the exposure method of the present invention can be carried out, and the entire pattern of the mask can be transferred onto the substrate with high line width uniformity at high throughput. it can.

Further, the second exposure apparatus according to the present invention has an illumination optical system that irradiates a mask with coherent illumination light having a wavelength of about 180 nm or less, and exposes the substrate with the illumination light via the mask. In such an exposure apparatus, an optical element that changes the polarization state of the illumination light is formed of magnesium fluoride in order to reduce the flexibility of the illumination light in the illumination optical system. According to such a second exposure apparatus of the present invention, the second exposure method of the present invention can be performed, and the entire mask pattern can be formed on the substrate with high line width uniformity at high throughput. Can be transcribed.

Further, a method of manufacturing an exposure apparatus according to the present invention includes assembling the illumination optical device of the present invention, a mask stage for holding a mask thereof, and a substrate stage for holding a substrate in a predetermined positional relationship.

Next, the device manufacturing method according to the present invention includes a step of illuminating the mask with the illumination light using the exposure method of the present invention, and transferring a pattern of the mask onto the substrate. According to the present invention, since the exposure method of the present invention is used, the entire mask pattern can be transferred onto the substrate with high line width uniformity without lowering the illuminance of the illumination light. Devices can be manufactured with high throughput. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic configuration diagram illustrating a projection exposure apparatus according to an example of an embodiment of the present invention. FIG. 2 is an enlarged perspective view showing the relationship between the prism 3 in FIG. 1 and the traveling direction and polarization direction of the illumination light. FIG. 3 is a diagram illustrating an example of the polarization state of the illumination light emitted from the prism 3. Figure 4 shows the manufacturing of semiconductor devices. It is a figure showing a fabrication process. BEST MODE FOR CARRYING OUT THE 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 a projection exposure apparatus for manufacturing a semiconductor device.

FIG. 1 shows a schematic configuration of the projection exposure apparatus of the present embodiment. In FIG. 1, at the time of exposure, a laser light source 1 as an exposure light source to an illumination optical system 15 composed of a condenser lens system 9 are used. Illumination light (exposure light) IL illuminates, for example, a rectangular illumination area on the pattern surface (lower surface) of reticle R as a mask. In this example, vacuum ultraviolet (VUV) F ₂ laser light (wavelength: 157 nm) is used as the exposure light. In addition, ArF excimer laser light (wavelength: 193 nm), YAG laser light Even when light having a wavelength of about 200 nm or less, such as harmonics of solid-state laser light or semiconductor laser light, or vacuum ultraviolet light is used as the exposure light, the coherence of the exposure light is strong. In such a case, the present invention is effective.

That is, pulse rates emitted from the laser light source 1 consisting of F ₂ laser light source - illumination light IL consisting laser light is coherent light beam linearly polarized in a predetermined direction. Illumination light IL passes through the temporal coherence retarder 2 is an optical member for reducing the (time coherency I) (described in detail later), magnesium fluoride is a material having a Fuku屈folding resistance (M g F ₂ Incident on the prism 3 made of). When the illumination light IL passes through the prism 3, the polarization state of the illumination light IL changes along a direction orthogonal to the optical axis of the illumination optical system 15, that is, the prism 3 in a plane perpendicular to the optical axis. The polarization state of the illumination light IL continuously changes in the direction perpendicular to the optical axis according to the position of the line projected on the plane perpendicular to the optical axis of the slope of the illumination light IL. space Effective coherency (spatial coherency) is reduced. The illumination light IL that has passed through the prism 3 passes through a vibrating mirror 4 as an optical element for further reducing spatial coherence, and then travels through a first stage fly as an optical integrator (homogenizer). After reaching the eye lens 5A, a plurality of light source images are formed at the rear focal position near the exit surface.

The illumination light IL from the plurality of light source images enters the stop 7 via the lens 6A. The aperture diameter of the aperture 7 is adjustable, and the illuminance (light amount) of the illumination light IL on the reticle R can be controlled by controlling the aperture diameter. A main control system 13 that controls the overall operation of the apparatus controls the aperture diameter of the aperture 7 via an illumination system control device 14. The illumination light IL that has passed through the aperture 7 passes through the lens 6B and the second-stage fly-eye lens 5B, and forms a large number of light source images at the rear focal point near the exit surface of the fly-eye lens 5B. . An aperture stop (σ stop) 5C is arranged near the exit surface. The illumination light IL that has passed through the aperture stop 5C is turned 90 ° downward by a mirror 8 and then condensed by a condenser lens system. Illuminate reticle R via 9. Although the condenser lens system 9 is shown in a simplified manner, it is actually an optical system that forms an image once inside and has a reticle blind (variable field stop) on the image forming surface. The illumination optical system 15 in this example is a double integrator system with a two-stage fly-eye lens (fly-eye and integrator system). The uniformity of the illuminance distribution has been improved.

The reticle R has a predetermined circuit pattern formed on a pattern surface of a transparent substrate such as fluorite or fluorine-doped quartz glass which is transparent to the illumination light IL and does not exhibit birefringence. An enlarged reticle pattern was formed. Illumination light IL that has passed through reticle R is applied to both sides (or to the wafer side). One side) Through a telecentric projection optical system PL, a pattern image in the illumination area of the reticle R is coated with a photoresist as a substrate at a predetermined projection magnification] 3 (3 is 1Z4, 1Z5, etc.) Projected on the wafer W. The wafer W is a disk-shaped substrate such as a semiconductor (silicon or the like) or an SOI (silicon on insulator) for manufacturing a semiconductor device.

At the top of the projection optical system PL, an imaging characteristic correction member 30 made of a parallel plate and having a variable tilt angle is installed, and the main control system 13 is connected to the imaging characteristic correction member 3 via a drive system (not shown). By driving 0, the configuration is such that the desired imaging characteristics (distortion and the like) of the projection optical system PL can be corrected to a desired state. Further, when the exposure light is in the vacuum ultraviolet region as in this example, the projection optical system PL can be constituted by a refraction system. As the system PL, a catadioptric system combining a reflective system and a refractive system, or a reflective system may be used. Examples of the catadioptric system include, for example, Japanese Patent Application Laid-Open No. H10-1040513, U.S. Patent No. 5,650,877, and U.S. Patent No. 5,559,338. Is disclosed in The disclosure of these U.S. patents shall be incorporated into the text as far as the national laws of the designated country designated in this international application or the selected elected country allow. Further, as a projection optical system PL, a pair of reflection elements (primary mirror and secondary mirror) each having an opening (transmission part) through which exposure light passes are arranged on an optical axis on which a plurality of refraction elements are arranged. An optical system that forms a primary image (intermediate image) by using a plurality of refraction elements (for example, Japanese Patent Application No. 10-37011043 and Japanese Patent Application No. 11 _ 6 6 7 6 9 May be used. Hereinafter, the Z axis is taken parallel to the optical axis AX of the projection optical system PL, the X axis is taken parallel to the plane of Fig. 1 in the plane perpendicular to the optical axis AX, and the Y axis is taken perpendicular to the plane of Fig. 1. Will be explained.

First, reticle R is held on reticle stage RST. The stage RST positions the reticle R on the reticle base 31 within a predetermined range in the X direction, the Y direction, and the rotation direction. The position of reticle stage RST (reticle R) is measured with high precision by a laser interferometer incorporated in reticle stage control system 12 and is based on the position information and control information from main control system 13. The reticle stage control system 12 controls the positioning operation of the reticle stage RST.

On the other hand, the wafer W is held on a wafer stage WST via a wafer holder (not shown), and the wafer stage WST is two-dimensionally movably mounted on the wafer base 10. The wafer stage WST positions the wafer W in the X direction and the Y direction by, for example, a linear motor method. The position of wafer stage WST (wafer W) is measured with high precision by a laser interferometer built into wafer stage control system 11, and its position information and control information from main control system 13 are provided. Based on the above, the wafer stage control system 11 controls the positioning operation of the wafer stage WST.

The wafer stage WST has a focus position (optical axis

A position in the X direction) and a Z tilt drive mechanism to control the tilt angle are incorporated. The focus position is measured at a plurality of measurement points on the surface of the wafer W by an auto focus sensor (not shown). Align the surface of W with the image plane of the projection optical system PL. In addition, the illumination system control device 14 causes the laser light source 1 to emit the illumination light IL under the instruction of the main control system 13 at the time of exposure, and instructs the vibration reflecting mirror driving device 4a. Then, while the image of the pattern of the reticle R is being exposed on each shot area on the wafer, the vibration reflecting mirror 4 is continuously vibrated.

When transferring the pattern image of the reticle R to each shot area on the wafer W, the wafer stage W is aligned after the wafer W is aligned. By driving the ST, one shot area on the wafer w is moved to the exposure area of the projection optical system PL. Then, the reticle R is illuminated with the illumination light IL from the illumination optical system 15 for a predetermined time to perform exposure, and then the next shot area on the wafer W is moved to the exposure area to perform exposure. By repeating the step-and-repeat method, a reduced image of the reticle pattern is transferred to each shot area on the wafer W. After that, a semiconductor device is manufactured through processes such as development of a photoresist, etching of a light-shielding film, and stripping of a resist, followed by dicing and bonding.

Further, the projection exposure apparatus of this embodiment can be of a step-and-scan type. In this case, a reticle stage RST is also provided with a continuous moving mechanism in a predetermined scanning direction (Y direction). Is done. Then, the reticle R is illuminated by the illumination light IL from the illumination optical system 15 in a rectangular illumination area elongated in the X direction, and in synchronization with scanning the reticle R in the Y direction with respect to the illumination area, By scanning the wafer W in the Y direction with a projection ratio of [3] as the speed ratio, the image of the reticle scale pattern is sequentially transferred to each shot area on the wafer W.

Next, the operation of the prism 3 made of magnesium fluoride in the illumination optical system 15 of this embodiment will be described with reference to FIGS.

First, in the present embodiment, it will be explained the reason for using magnesium fluoride (M g F ₂₎ as a birefringent optical material. Conventionally, quartz has been used as a birefringent optical material.However, as described above, ordinary quartz greatly reduces the transmittance of vacuum ultraviolet light, especially when the wavelength is less than 180 nm. Has a considerably lower transmittance. On the other hand, as an optical material that has a relatively large transmittance even in the vacuum ultraviolet region with a wavelength of about 200 nm or less, quartz glass doped with fluorite (C a F ₂ ) and fluorine in addition to magnesium fluoride , And And lithium fluoride (L i F). However, magnesium fluoride is a uniaxial crystal and exhibits optical anisotropy (birefringence), whereas fluorite and lithium fluoride are both cubic and exhibit birefringence. Since quartz glass is amorphous and does not exhibit birefringence because it is amorphous, magnesium fluoride is the most suitable optical material that has high transmittance in the vacuum ultraviolet region and exhibits birefringence at present. Further, since the magnesium fluoride having a high transmittance at a wavelength of 1 5 0 wavelength has a 80% degree or more transmittance nm is 1 3 0 nm even 4 about 0% over more than, the exposure light is F ₂ laser (Wavelength: 157 nm), and even a laser beam having a shorter wavelength (for example, a harmonic) can maintain a high transmittance.

Magnesium fluoride can also be used as a window material for vacuum ultraviolet light, but in such applications it is better not to cause birefringence. The optical axis (optic axis), which is the axis of, is set to be approximately parallel to the optical path of the illumination light. On the other hand, in this example, since the birefringence of magnesium fluoride is actively used, a state in which birefringence occurs for the illumination light, that is, the optical axis of the magnesium fluoride and the illumination light They differ in that they are installed in a direction perpendicular to the optical axis.

Hereinafter, the method of using the magnesium fluoride prism 3 will be specifically described.

FIG. 2 shows a state in which the illumination light IL is incident on the prism 3. In this FIG. 2, the illumination light IL travels along the optical axis of the illumination optical system 15 (in this example, parallel to the Z axis). The prism 3 is formed in a wedge shape whose thickness changes linearly in a direction perpendicular to the optical axis (in this example, a direction parallel to the X axis). It is set wider than the cross-sectional shape of the illumination light IL. Magnesium fluoride constituting the prism 3 is birefringent. This is a uniaxial crystal with a characteristic, and is arranged in the illumination optical system 15 (see Fig. 1) so that each of the three axis directions of this crystal is parallel to the X axis, Y axis, and Z axis. ing. In FIG. 2, the 〇 axis and the E axis indicate the direction of the ordinary ray component and the direction of the extraordinary ray component due to birefringence, respectively, and the 0 axis and the E axis are parallel to the X axis and the Y axis, respectively. At this time, the optical axis of the prism 3 is parallel to the E axis (Y axis).

In general, laser light is linearly polarized light due to a window material or the like provided to increase the reflectance of the resonator, and further, the laser light source used in the projection exposure apparatus has a laser light inside a resonator. Prisms and the like for reducing the chromatic aberration of the projection optical system are installed, and the band of the laser light is narrowed. In such a case, the laser light becomes stronger linearly polarized light, and the polarization direction depends on the installation angle of the prism installed in the resonator. The illumination light IL of this example is also strong linearly polarized light, and its polarization direction is set in the direction indicated by the arrow 20.

In this example, the 〇 axis (X axis) or E axis (Y axis) of the crystal of the prism 3 forms a predetermined inclination angle ο; with respect to the polarization direction of the illumination light IL indicated by the arrow 20, and the illumination optical system The prism 3 is arranged so that the thickness of the prism 3 gradually changes in the direction (X direction) orthogonal to the optical axis of the prism. The tilt angle may be any angle other than 0 ° and 90 °, but in order to greatly change the polarization state, the tilt angle is preferably closer to 45 °. Therefore, in this example, the inclination angle is set within a range of about 45 ° ± 10 ° as an example. By arranging the prism 3 so that the 〇 axis or the E axis of the crystal of the prism 3 forms an inclination angle ο; with respect to the polarization direction when the illumination light IL is incident, it is possible to obtain the usual birefringence. By generating a predetermined phase difference between the light beam and the extraordinary light beam, the polarization state of the illumination light I, that is, the ellipticity in the polarization amplitude space representing the degree of polarization, is determined by the length of the optical path of the illumination light IL in the prism 3. It can be changed according to the thickness (thickness). That is, depending on the optical path length in the prism 3, the polarization at the time of emission of the illumination light IL The light state will be different from the polarization state at the time of incidence. Since the thickness of the prism 3 changes gradually along the X direction, the polarization state of the illumination light IL emitted from the prism 3 changes gradually along the X direction.

FIG. 3 shows an example of a change in the polarization state of the light beams IL1 to IL4 in the linearly polarized illumination light IL incident on the prism 3. In FIG. 3, the light beams IL1 to IL4 Since the length of each optical path (thickness of prism 3) is different from L1 to L4, the phase difference between ordinary ray and extraordinary ray due to birefringence when emitted from prism 3 is Φ1 to Φ4 Also change. Among them, the light beam I L 1 is assumed to be emitted from the prism 3 as linearly polarized light (hereinafter referred to as “0 ° linearly polarized light”) indicated by an arrow 21 Α. On the other hand, assuming that the phase difference φ 2 of the light beam IL 2 is different from the phase difference φ 1 of the light beam IL 1 by 90 ° corresponding to 14 wavelengths, the light beam IL 2 becomes, for example, an arrow 2 The light is emitted from prism 3 as clockwise circularly polarized light indicated by 1 B. Further, assuming that the phase difference φ 3 of the light beam IL 3 is different from the phase difference φ by 180 ° corresponding to 1 Z 2 wavelengths, the light beam IL 3 has a polarization direction of 1 with respect to the light beam IL 1. The light exits from the prism 3 as linearly polarized light indicated by an arrow 21 C different by 80 ° (hereinafter referred to as “linearly polarized light at 180 °”). Also, assuming that the phase difference (/) 4 of the light beam IL 4 is different from the phase difference φ 2 by 270 ° corresponding to 3/4 wavelength, the light beam IL 4 is opposite to the light beam IL 2 The light is emitted from the prism 3 as left-handed circularly polarized light.

That is, the polarization state of the illumination light IL emitted from the prism 3 is 0 ° linearly polarized light, clockwise circularly polarized light, and 18 ° sequentially along the direction (X direction) perpendicular to the optical axis of the illumination optical system. 0. Linearly polarized light, left-handed circularly polarized light, 0 ° linearly polarized light, right-handed circularly polarized light, and so on. Since the coherence between light beams having different polarization states is low, the prism 3 is connected to the illumination optics as shown in Fig. 1. By installing in the system 15, the spatial coherence of the illumination light IL after passing through the prism 3 is reduced.

Note that the tilt angle in FIG. 2 described above is not necessarily 45 °, but when the tilt angle α is 45 °, that is, in the middle of the directions of two crystal axes having different refractive indexes from each other. When the prism 3 is arranged so that the direction of the illumination light IL substantially matches the polarization direction of the illumination light IL, a part of the illumination light IL passing through the prism 3 is completely circularly polarized, so that the illumination light IL There is an advantage that the coherence can be efficiently reduced.

As described above, the illumination light lifting Chi a high transmittance to (F ₂ laser) IL, and the illumination optical system of FIG. 1 the flop rhythm 3 formed by magnesium fluoride is glass material of the birefringent 1 By arranging the illumination light IL inside the reticle R, it is possible to suppress the occurrence of a spike in the illumination area of the reticle R without lowering the illuminance of the illumination light IL, thereby preventing the illumination light IL from deteriorating the uniformity of the illuminance distribution. Can be. As a result, it is possible to prevent the uniformity of the line width of the circuit pattern formed on the wafer W from deteriorating, thereby reducing the decrease in the operating speed of the manufactured device and preventing the device from malfunctioning.

In addition, in the projection exposure apparatus of this example, as shown in FIG. 1, in addition to the prism 3 made of magnesium fluoride, a reflector 2, an oscillating reflector 4, and a flywheel are used as optical elements for uniformizing the illuminance distribution. Eye lenses 5A and 5B are provided to make the illuminance distribution of the illumination light IL more uniform.

First, the retarder (optical delay element) 2 is a partial optical delay element composed of a multiple reflection element composed of a semi-transparent mirror 2a and reflection mirrors 2b and 2c. About 1 to 2 of the light IL is reflected by the semi-transparent mirror 2 a and travels to prism 3. Then, the illumination light IL 5 transmitted through the semi-transparent mirror 2a is reflected by the reflection mirrors 2b and 2c, and its optical path again matches the illumination light directly reflected by the semi-transparent mirror 2a. I have. In this case, semi-transparent mirror 2 Since the illumination light IL 5 transmitted through a has a longer optical path length than the illumination light directly reflected by the semi-transparent mirror 2 a, the illumination light IL traveling toward the prism 3 is allowed to pass through the retarder 2 by passing through the retarder 2. Interference can be reduced.

Further, the vibration reflecting mirror 4 is also an optical element for reducing the occurrence of speckle. By vibrating the vibration reflecting mirror 4 with the vibration axis at the very short period about the optical axis by the vibration reflecting mirror driving device 4a, the light path of the illumination light IL is vibrated within a small angle around the predetermined direction, and the vibration is very small. By changing the optical path length, the spatial responsiveness of the illumination light IL can be reduced. Further, in this example, the use of two-stage fly-eye lenses 5A and 5B makes the illuminance distribution of the illumination light IL more uniform.

Note that the prism 3 made of magnesium fluoride in this example impairs the functions of the above-described optical elements (the retarder 2, the vibration reflecting mirror 4, and the fly-eye lenses 5A and 5B) for uniformizing the illuminance distribution. Needless to say, they can be used together.

Further, in this example, magnesium fluoride was used as an optical material for forming the prism 3. However, if the glass material is birefringent and has a high transmittance to illumination light for exposure, it is used as the prism 3. It goes without saying that you can do it. As a result, the coherence of the illumination light can be reduced and the generation of speckles can be suppressed without lowering the illuminance of the illumination light as in the present example.

In addition, the prism 3 is a prism whose thickness changes in a one-dimensional direction, but other than that, the prism whose thickness changes in a two-dimensional direction, for example, intersects each other in a plane perpendicular to the optical axis of the illumination optical system. A prism whose thickness changes gradually in two directions may be used. Further, a prism whose thickness changes in a high-order function of second order or more may be used. In the above embodiment, In order to reduce the coherence (spatial coherency) of the illumination light, a prism was used as a transmission type optical element that changes the polarization state. However, if the polarization state can be changed similarly to the prism, The optical element may have any shape and configuration.

In the above-described embodiment, the retarder 2 and the vibration reflecting mirror 4 are used in addition to the prism 3. However, the present invention is not limited to the combination of the retarder 2 and the vibration reflecting mirror 4. Depending on the uniformity of the illuminance on the reticle or wafer, only one of the retarder 2 and the vibration reflecting mirror 4 may be used, or both may not be used. Further, in the above-described embodiment, a fly eye lens is used as an optical integrator (homogenizer). You may use it together. Of course, the number of optical integrators arranged in the illumination optical system is not limited to two, but may be one or three or more. Further, as a light source for generating light in the vacuum ultraviolet region, eg if the wavelength 1 4 6 nm krypton dimer laser (K r ₂ laser), wavelength 1 3 4 nm of K r A r laser, or a wavelength 1 2 6 nm It is also possible to use an argon dimer laser (Ar ₂ laser).

Since the optical path is shifted by disposing the prism 3 in the optical path of the illumination light IL, it is desirable to further dispose an optical member (prism or the like) for correcting this.

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. 4 shows an example of a semiconductor device manufacturing process. In FIG. 4, first, a wafer W is manufactured from a silicon semiconductor or the like. Then, a photoresist is applied on the wafer W (step S10), and the next step S12 is performed. The reticle R1 is loaded on the reticle stage of the projection exposure apparatus of the above embodiment (FIG. 1), and the pattern (represented by the symbol A) of the reticle R1 is transferred to the entire shot area SE on the wafer W. Transfer (exposure) to The wafer W is, for example, a wafer (12-inch wafer) having a diameter of 300 mm. 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, the reticle R2 is loaded on the reticle stage of the projection exposure apparatus of the above embodiment (FIG. 1). Then, the pattern (represented by the symbol B) of the reticle R 2 is transferred (exposed) to each shot area SE on the wafer W. Then, in step S20, a predetermined pattern is formed in each shot region of the wafer W by performing development, etching, ion implantation, and the like of the wafer W.

The above exposure process to pattern formation process (Step S16 to Step S2

0) is repeated as many times as necessary to produce the desired semiconductor device. Then, through a dicing process (step S22) for separating each chip CP on the wafer W one by one, a bonding process and a packaging process (step S224), a semiconductor device as a product is obtained. Chair SP is manufactured.

The application of the projection exposure apparatus according to the above-described embodiment is not limited to an exposure apparatus for manufacturing a semiconductor. For example, an exposure apparatus for a liquid crystal that exposes a liquid crystal display element pattern to a square glass plate, It can be widely applied to exposure equipment for manufacturing plasma display thin film magnetic heads, imaging devices (CCD, etc.), micro machines, and the like. Also, a reticle or a mask used in an exposure apparatus for manufacturing a device for manufacturing a semiconductor element or the like may be used, for example. For example, the projection exposure apparatus of the above-described embodiment can be suitably used also when manufacturing with an exposure apparatus using far ultraviolet light (DUV light) or vacuum ultraviolet light (VUV light).

Also, the present invention provides a step-and-stitch type reduction projection exposure apparatus that uses, for example, vacuum ultraviolet light or the like as exposure illumination light, or a projection optical system that uses vacuum ultraviolet light or the like as exposure light. Alternatively, the present invention can be applied to a proximity type exposure apparatus that exposes a mask pattern by bringing a mask and a substrate into close contact.

In addition, a single-wavelength laser in the infrared or visible region oscillated from a DFB semiconductor laser or a fiber laser as exposure illumination light, for example, erbium (Er) (or both erbium and ytterbium (Yb)) is used. It is also possible to use harmonics that have been amplified by a coupled fiber amplifier and wavelength-converted to ultraviolet light using a nonlinear optical crystal. For example, if the oscillation wavelength of a single-wavelength laser is in the range of 1.544 to 1.553 / xm, the 8th harmonic in the range of 193 to 194 nm, that is, almost the same as the ArF excimer laser same wave length and comprising the ultraviolet light is obtained, when the oscillation wavelength 1. and 57 to 1.58 01 within the range of 1 0 harmonic in the range of 1. 57 to 1 58 nm, i.e. the F ₂ lasers Ultraviolet light having substantially the same wavelength can be obtained.

Further, the projection exposure apparatus according to the above-described embodiment includes an illumination optical system including a prism formed of a birefringent glass material that is transparent to illumination light and is made of birefringent glass material, such as magnesium fluoride described above. The projection optical system is incorporated into the exposure apparatus body to perform optical adjustments, and a reticle stage or wafer stage consisting of a large number of mechanical parts is attached to the exposure apparatus body to connect wiring and piping for further comprehensive adjustment (electrical adjustment, operation Confirmation etc.). It is desirable that the projection exposure apparatus be manufactured in a clean room where the temperature, cleanliness, etc. are controlled. It should be noted that the present invention is not limited to the above-described embodiment, and can take various configurations without departing from the gist of the present invention. Further, all disclosures, including the specification, claims, drawings, and abstract, of Japanese Patent Application No. 11-122 906 filed on April 28, 1999, are as follows: , Which is incorporated here by reference in its entirety. Industrial applicability

According to the first or second exposure method of the present invention, the spatial coherence of the illumination light is reduced, and the occurrence of speckle is suppressed, so that the deterioration of the uniformity of the illuminance distribution of the illumination light is suppressed. be able to. Therefore, exposure can be performed with a uniform illuminance distribution using illumination light in a vacuum ultraviolet region having a wavelength of 200 nm or less.

Next, according to the first or second illumination optical device of the present invention, the polarization state of the illumination light can be gradually changed in a direction perpendicular to the optical axis of the illumination light, and the spatial The coherence can be reduced to suppress the occurrence of speckle, and the deterioration of the uniformity of the illuminance of the illumination light can be suppressed. Further, since the second illumination optical device further includes the vibrating member and the optical integre, the illuminance distribution of the illumination light can be made more uniform. In particular, by using a prism made of magnesium fluoride, even when vacuum ultraviolet light is used, high illuminance uniformity and low extinction coefficient can be realized with almost no change in the entire apparatus.

Next, according to the first or second exposure apparatus of the present invention, by performing the exposure method of the present invention, the pattern of the mask is formed on the substrate with high precision, and the height of the device is further increased. Integration and high speed can be achieved.

Further, according to the device manufacturing method of the present invention, a high-performance device can be manufactured with high throughput.

Claims

The scope of the claims

1. An exposure method for illuminating a mask with illumination light and transferring a pattern of the mask onto a substrate,

The wavelength of the illumination light is set to about 180 nm or less, and an optical element formed of magnesium fluoride is arranged on an optical path until the illumination light enters the mask. An exposure method characterized in that the polarization state of the illumination light is gradually changed in a direction perpendicular to the vertical direction.

2. The polarization state of the illumination light is spatially and continuously changed in at least one direction in a plane perpendicular to the optical axis of the illumination light. Exposure method.

3. A method of illuminating a mask with coherent illumination light and exposing a substrate with the illumination light through the mask,

In order to reduce the wavelength of the illumination light to about 180 nm or less, and to reduce the coherence of the illumination light, the polarization state of the illumination light is formed of magnesium fluoride prior to incidence on the mask. An exposure method characterized by changing by an optical element.

4. An illumination optical device for illuminating a mask with illumination light having a wavelength of 200 nm or less from a light source,

On the optical path of the illuminating light between the light source and the mask, the illuminating light is formed of a material having a transmissive property and a birefringence with respect to the illuminating light. An illumination optical device comprising a prism having a gradually changing thickness.

5. An illumination optical device for illuminating a mask with illumination light having a wavelength of 200 nm or less from a light source,

It is arranged on an optical path of illumination light from the light source, and is transmitted with respect to the illumination light. A prism formed of a material having a birefringent property and having a thickness gradually changing in a direction intersecting the optical axis of the illumination optical device;

A vibrating member for vibrating the illumination light passing through the prism,

With the opti-force that forms a plurality of light source images from the illumination light passing through the vibrating member,

A condenser optical system for guiding illumination light emitted from the optical integument to the mask;

An illumination optical device, comprising:

6. The illumination light emitted from the light source is a coherent light beam linearly polarized in a predetermined direction,

The illumination optical device according to claim 4, wherein the prism is disposed such that a direction intermediate between directions of two crystal axes having different refractive indexes substantially matches the predetermined direction. .

7. The illumination light is a light flux having a predetermined coherent polarization state having a wavelength of 180 nm or less, and the material of the prism is a crystal of magnesium fluoride. 7. The illumination optical device according to claim 6.

8. An exposure apparatus provided with the illumination optical device according to any one of claims 4 to 7,

An exposure apparatus, comprising: illuminating a mask with illumination light from the illumination optical device; and transferring a pattern of the mask onto a substrate.

9. An exposure apparatus, comprising: an illumination optical system that irradiates a mask with coherent illumination light having a wavelength of about 180 nm or less, and exposing a substrate to the illumination light via the mask.

An exposure apparatus, wherein an optical element for changing a polarization state of the illumination light is formed of magnesium fluoride in order to reduce coherence of the illumination light in the illumination optical system.

10. The illumination optical device according to any one of claims 4 to 7, a mask stage for holding the mask, and a substrate stage for holding the substrate are assembled in a predetermined positional relationship. A method for manufacturing an exposure apparatus.

11. A step of irradiating the mask with the illuminating light using the exposure method according to any one of claims 1 to 3, and transferring a pattern of the mask onto the substrate. Method of manufacturing devices.