JP7646402B2 - Illumination optical system, exposure apparatus, and method for manufacturing article - Google Patents

Description

The present invention relates to an illumination optical system, an exposure apparatus, and a method for manufacturing an article.

In the photolithography process for manufacturing devices such as semiconductor elements, an exposure apparatus is generally used to transfer a pattern formed on an original (mask or reticle) onto a substrate (silicon substrate or glass substrate) coated with a photosensitive agent. With exposure apparatus, the patterns transferred to the substrate are becoming increasingly finer, and even a slight change in the exposure conditions can increase the defect rate and reduce the yield.

In the illumination optical system that illuminates the original, defects that cause the line width of the pattern formed on the substrate to be non-uniform due to uneven illuminance in the illumination area are suppressed by making the accumulated exposure amount within the illumination area uniform. For example, a technique for making the accumulated exposure amount uniform has been proposed for a scanning exposure device that transfers the pattern of the original to the substrate by scanning the original and substrate relatively with slit-shaped exposure light (see Patent Document 1). In Patent Document 1, a variable slit device is used to change the width of the slit-shaped exposure light in the scanning direction depending on the position in the slit direction (direction perpendicular to the scanning direction), thereby making the accumulated exposure amount uniform.

In addition, as semiconductor elements become finer, exposure devices are required to achieve even higher resolution. To meet this demand, the numerical aperture (NA) of the projection optical system is increased (higher NA) and the wavelength of the exposure light is shortened. When the wavelength of the exposure light is shortened, the transmittance of the glass material generally decreases and the number of types of glass material that can be used in the projection optical system becomes extremely limited, making it difficult to correct the chromatic aberration of the projection optical system, and it is necessary to narrow the wavelength width of the exposure light to a level where the effect of chromatic aberration can be ignored. For example, in projection optical systems that use light with a wavelength of 300 nm or less, usable glass materials are limited to quartz and fluorite, so a laser is used as the exposure light (exposure light source). Specifically, excimer lasers are widely used as short-wavelength light sources for exposure devices because they have very high energy and can be expected to achieve high throughput.

On the other hand, because excimer lasers are pulsed lasers, in scanning exposure devices, misalignment between the scanning speed and the pulse oscillation can cause exposure unevenness on the original or substrate. In order to reduce exposure unevenness caused by the effects of pulse oscillation, a technique has been proposed that relaxes the accuracy of synchronization between the scanning speed and pulse oscillation by making the light intensity distribution in the scanning direction on the illuminated surface (original) substantially an isosceles trapezoid or an isosceles triangle. However, in order to make the light intensity distribution in the scanning direction on the illuminated surface substantially an isosceles trapezoid or an isosceles triangle, it is possible to use a light-reducing element such as an ND filter, but this leads to a loss of light.

Therefore, a technology has been proposed for forming a light intensity distribution such as an isosceles trapezoid or an isosceles triangle with little light loss (see Patent Document 2). In Patent Document 2, the principal ray of the light beam is focused at a position a predetermined distance away from the illuminated surface in the optical axis direction in a plane including the scanning direction on the illuminated surface and the optical axis of the illumination optical system, thereby forming an inclined region due to blurring of the light beam on the illuminated surface. By forming the light intensity distribution of such an inclined region into a predetermined shape, it is possible to reduce the variation in the exposure amount while suppressing the decrease in illumination efficiency (light loss). To achieve this, Patent Document 2 provides an anamorphic lens such as a cylindrical lens in the illumination optical system that superimposes the light beam from the optical integrator on the illuminated surface. According to the technology disclosed in Patent Document 2, the shape of the light intensity distribution in the scanning direction on the illuminated surface can be determined so that the variation in the integrated exposure amount caused by the variation in the scanning speed and the timing shift of the pulse oscillation is minimized.

Japanese Patent Application Publication No. 10-340854 Japanese Patent Application Publication No. 7-230949

However, if an anamorphic lens such as a cylindrical lens is provided in the illumination optical system that superimposes the light beam from the optical integrator on the illuminated surface, the numerical aperture or exit pupil position of the illumination optical system will differ between the scanning direction and the direction perpendicular to the scanning direction. As a result, the transfer characteristics of the pattern transferred onto the substrate will differ between the scanning direction and the direction perpendicular to the scanning direction.

The present invention has been made in consideration of the problems with the conventional technology, and has as an exemplary object to provide an illumination optical system that is advantageous for illuminating an illuminated surface.

In order to achieve the above object, an illumination optical system according to one aspect of the present invention is an illumination optical system that illuminates an illuminated surface, and has an optical integrator that forms a secondary light source with light from a light source, the optical integrator including an incident-side optical element on which a plurality of first optical elements are arranged, and an exit-side optical element including a plurality of second optical elements arranged corresponding to each of the plurality of first optical elements, the plurality of first optical elements and the plurality of second optical elements are arranged periodically in a first direction and a second direction intersecting the first direction, and the arrangement period of the plurality of first optical elements and the arrangement period of the plurality of second optical elements are different in at least one of the first direction and the second direction.

The present invention provides an illumination optical system that is advantageous for illuminating a surface to be illuminated.

1 is a schematic cross-sectional view showing a configuration of an exposure apparatus according to one aspect of the present invention. 1 is a schematic cross-sectional view showing an example of a configuration from an integrator to an intermediate illumination surface. 1 is a schematic cross-sectional view showing an example of a configuration from an integrator to an intermediate illumination surface. 1 is a schematic cross-sectional view showing a state of a light ray illuminating a point on an intermediate illumination plane. 1 is a schematic cross-sectional view showing a state of a light ray illuminating a point on an intermediate illumination plane. 1 is a schematic cross-sectional view showing an example of a configuration from an integrator to an intermediate illumination surface. 1 is a schematic cross-sectional view showing a state of a light ray illuminating a point on an intermediate illumination plane. 1 is a schematic cross-sectional view showing an example of a configuration from an integrator to an intermediate illumination surface. 1 is a schematic cross-sectional view showing an example of a configuration from an integrator to an intermediate illumination surface.

The following embodiments are described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe multiple features, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicate explanations are omitted.

Figure 1 is a schematic cross-sectional view showing the configuration of an exposure apparatus EX according to one aspect of the present invention. The exposure apparatus EX is a lithography apparatus used in the manufacturing process of devices such as semiconductor elements, which forms a pattern on a substrate. In this embodiment, the exposure apparatus EX is a step-and-scan type exposure apparatus (scanner) that exposes (scanning-exposes) the substrate 21 while moving the original 18 and the substrate 21 in the scanning direction, thereby transferring the pattern of the original 18 onto the substrate. However, the exposure apparatus EX can also employ the step-and-repeat type or other exposure methods.

As shown in FIG. 1, the exposure apparatus EX has an illumination optical system IL that illuminates an original 18 (reticle or mask) with light from a light source 1, and a projection optical system 20 that projects the pattern of the original 18 onto a substrate 21 (wafer or glass plate). The exposure apparatus EX also has an original stage 19 that holds and moves the original 18, and a substrate stage 22 that holds and moves the substrate 21.

In this embodiment, the light source 1 is a pulsed light source that oscillates in a pulsed manner, and includes, for example, an ArF excimer laser with a wavelength of approximately 193 nm or a KrF excimer laser with a wavelength of approximately 248 nm, and emits light (exposure light) for illuminating the original 18.

The illumination optical system IL includes a deflection optical system 2, an exit angle preserving optical element 4, a diffractive optical element 5, a condenser lens 6, a prism unit 8, and a zoom lens unit 9. The illumination optical system IL also includes an optical integrator 100, an aperture stop 11, a condenser lens 12, a field stop 13, a masking unit 15, an imaging optical system 16, and a folding mirror 17.

The light guide optical system 2 guides the light from the light source 1 to the exit angle preserving optical element 4 via the folding mirror 3. The exit angle preserving optical element 4 is provided on the light source side of the diffractive optical element 5 and includes an optical integrator such as a fly's eye lens, a microlens array, or a fiber bundle. The exit angle preserving optical element 4 guides the light from the light source 1 to the diffractive optical element 5 while maintaining the divergence angle constant. The exit angle preserving optical element 4 reduces the effect of output fluctuations of the light source 1 on the light intensity distribution (pattern distribution) formed by the diffractive optical element 5.

The diffractive optical element 5 is disposed on a plane that is in a Fourier transform relationship with the pupil plane of the illumination optical system IL. The diffractive optical element 5 converts the light intensity distribution of light from the light source 1 by diffraction to form a desired light intensity distribution on the pupil plane of the illumination optical system IL, which is a plane conjugate to the pupil plane of the projection optical system 20, or on a plane conjugate to the pupil plane of the illumination optical system IL. The diffractive optical element 5 may be configured as a computer generated hologram (CGH) designed by a computer so that a desired diffraction pattern is obtained on the diffraction pattern plane. In this embodiment, the light source shape formed on the pupil plane of the projection optical system 20 is called the effective light source shape. Note that the "effective light source" means the light intensity distribution or light angle distribution on the illuminated surface and the conjugate plane of the illuminated surface.

The illumination optical system IL may be provided with a plurality of diffractive optical elements 5. For example, each of the plurality of diffractive optical elements 5 is attached (mounted) to one corresponding to a plurality of slots of a turret (not shown), and an arbitrary diffractive optical element 5 is placed in the optical path of the illumination optical system IL. Each of the plurality of diffractive optical elements 5 forms a different effective light source shape. These effective light source shapes include a small circular shape (relatively small circular shape), a large circular shape (relatively large circular shape), annular shape, dipole shape, quadrupole shape, and other shapes. A method of illuminating an illuminated surface with an effective light source shape that is annular, dipole, or quadrupole shape is called modified illumination.

The light from the exit angle preserving optical element 4 is diffracted by the diffractive optical element 5 and directed to the condenser lens 6. The condenser lens 6 collects the light diffracted by the diffractive optical element 5 and forms a diffraction pattern (light intensity distribution) on the diffractive surface 7.

The diffractive surface 7 is a surface that has an optical Fourier transform relationship with the diffractive optical element 5. By replacing the diffractive optical element 5 arranged in the optical path of the illumination optical system IL, the shape of the light intensity distribution formed on the diffractive surface 7 can be changed. The light intensity distribution formed on the diffractive surface 7 passes through the prism unit 8 and the zoom lens unit 9, and is guided to the optical integrator 100 via the folding mirror 10.

The prism unit 8 adjusts the annular ratio and other parameters of the light intensity distribution formed on the diffractive surface 7 and guides it to the zoom lens unit 9. The zoom lens unit 9 enlarges or reduces the light intensity distribution formed on the diffractive surface 7 while maintaining a roughly similar shape, and guides it to the optical integrator 100.

The optical integrator 100 forms a number of secondary light sources according to the intensity distribution of the incident light and guides them to the condenser lens 12. The detailed configuration of the optical integrator 100 will be described later.

The aperture stop 11 is located near the exit surface of the optical integrator 100, i.e., at the pupil plane of the illumination optical system IL.

The condenser lens 12 collects a large number of light beams guided from the optical integrator 100 and illuminates the intermediate illumination surface 14, which is the illuminated surface of the condenser lens 12, in a superimposed manner. When the light beams enter the optical integrator 100 and are collected by the condenser lens 12, the intermediate illumination surface 14 is illuminated with a light intensity distribution that is approximately rectangular.

The imaging optical system 16 projects the light intensity distribution formed on the intermediate illumination plane 14 onto the original 18, which is the illuminated surface of the illumination optical system IL, via the folding mirror 17. In this way, the original 18 and the intermediate illumination plane 14 are in an optically conjugate relationship.

The masking unit 15 is disposed on the intermediate illumination plane 14. The masking unit 15 is disposed to define the illumination range of the master 18 held on the master stage 19, and is scanned in synchronization with the master stage 19 and the substrate stage 22. In FIG. 1, the scanning direction of the masking unit 15 is the Z direction, and the scanning direction of the master 18 and the substrate 21 is the X direction.

The field stop 13 is provided at a position away from the intermediate illumination plane 14 and the masking unit 15 in the optical axis direction (X direction) of the illumination optical system IL. The field stop 13 defines the illumination range in the scanning direction (Z direction at the position of the field stop 13) of the intermediate illumination plane 14, which is the illuminated surface of the condenser lens 12.

The field stop 13 is located away from the intermediate illumination plane 14 in the optical axis direction of the illumination optical system IL, so that the light partially blocked by the field stop 13 has a substantially trapezoidal light intensity distribution in the scanning direction at the intermediate illumination plane 14. This makes it possible to reduce the effects of uneven exposure that occurs in the exposure apparatus EX when the scanning speed or timing of pulse oscillation is shifted.

In this embodiment, the field stop 13 is disposed near the intermediate illumination surface 14, but it may also be disposed near the original 18, which is the surface to be illuminated. Also, in this embodiment, the field stop 13 is disposed closer to the light source than the intermediate illumination surface 14, but this is not limited thereto, and it may also be disposed closer to the original than the intermediate illumination surface 14.

Furthermore, the field stop 13 may be a variable field stop whose opening width in the scanning direction can be changed for each direction perpendicular to the scanning direction (non-scanning direction (Y direction). By changing the opening width in the scanning direction of the field stop 13, the length in the scanning direction of the light intensity distribution formed in the illumination area can be changed. This makes it possible to correct unevenness in the accumulated exposure amount in the non-scanning direction during scanning exposure.

The projection optical system 20 includes multiple optical components (optical elements such as lenses and mirrors) and projects the pattern of the original 18 onto the substrate 21. The resolution of the pattern of the original 18 depends on the numerical aperture (NA) of the projection optical system 20 and the effective light source shape.

During exposure, light emitted from the light source 1 illuminates the original 18 held on the original stage 19 via the illumination optical system IL. The pattern of the original 18 is imaged onto the substrate 21 held on the substrate stage 22 by the projection optical system 20. At this time, the pattern of the original 18 is transferred to the substrate 21 by scanning the original 18 and the substrate 21 at a speed ratio equal to the reduction magnification ratio of the projection optical system 20.

The configuration of the optical integrator 100 in the illumination optical system IL will be described below. Figures 2 and 3 are schematic cross-sectional views showing a portion of the configuration of the illumination optical system IL, specifically, the configuration from the optical integrator 100 to the intermediate illumination surface 14, where Figure 2 shows a cross section in the XY plane and Figure 3 shows a cross section in the XZ plane.

In this embodiment, the optical integrator 100 is composed of an incident side integrator 101, which is an incident side optical element, and an exit side integrator 102, which is an exit side optical element. The incident side integrator 101 and the exit side integrator 102 are lens arrays (fly-eye lenses) arranged in the scanning direction (Z direction) and the non-scanning direction (Y direction) perpendicular to (intersecting) the scanning direction, respectively.

The incident side integrator 101 includes a plurality of incident side element lenses (first optical elements) 101a arranged periodically in the scanning direction (first direction) and the non-scanning direction (second direction). The exit side integrator 102 includes a plurality of exit side element lenses (second optical elements) 102a arranged corresponding to each of the incident side element lenses 101a. Note that element lenses (not shown) are also arranged in planes other than the XY plane and the XZ plane. In Figs. 2 and 3, the incident side integrator 101 and the exit side integrator 102 each exemplarily show a lens array configured by arranging five element lenses in the scanning direction and five element lenses in the non-scanning direction.

The light incident on the optical integrator 100 is split into multiple beams by the entrance side integrator 101. The beams split by the entrance side integrator 101 exit from the individual element lenses 101a of the entrance side integrator 101, enter the corresponding element lenses 102a of the exit side integrator 102, and exit toward the condenser lens 12.

An aperture stop 11 is disposed near the exit surface of the optical integrator 100 (exit side integrator 102). The position of the aperture stop 11 corresponds to the pupil plane of the condenser lens 12.

The light emitted from the optical integrator 100 is collected by the condenser lens 12 and illuminates the intermediate illumination surface 14 in a superimposed manner. As shown in FIG. 2, the light rays that are perpendicularly incident on the center of each optical surface of the element lenses 101a of the entrance side integrator 101 are emitted perpendicularly from the center of the optical surface of the corresponding element lens 102a of the exit side integrator 102. In other words, the light rays that are perpendicularly incident on the center of each optical surface of the element lenses 101a of the entrance side integrator 101 are each emitted from the optical integrator 100 parallel to the optical axis (X-axis) of the illumination optical system IL. The light rays that are emitted parallel to the optical axis of the illumination optical system IL are collected at a position a distance fc from the condenser lens 12 (principal point) via the condenser lens 12 having a focal length fc.

The intermediate illumination plane 14 is located at a distance fc from the condenser lens 12 (principal point). Therefore, the light intensity distribution in the non-scanning direction at the intermediate illumination plane 14 is a substantially rectangular distribution, as shown in FIG. 2.

Let us now consider a case where the arrangement period of the element lenses in the entrance side integrator 101 and the exit side integrator 102 is the same, and the field stop 13 for forming a trapezoidal light intensity distribution in the scanning direction is placed at a position away from the intermediate illumination plane 14 in the optical axis direction. In this case, part of the light must be blocked by the field stop 13, resulting in a decrease in illumination efficiency.

Also consider the case where the field stop 13 is placed at a distance fc from the condenser lens 12 (the focusing position), and the intermediate illumination plane 14, which is optically conjugate with the original 18, is placed at a position away from the focusing position in the optical axis direction. In this case, the light blocked by the field stop 13 can be kept to a minimum, but the light intensity distribution in the non-scanning direction at the intermediate illumination plane 14 also becomes approximately trapezoidal. For this reason, in order to uniformly illuminate the original 18, the area of the hypotenuse of the light intensity distribution must be blocked by the masking unit 15, resulting in a decrease in illumination efficiency.

Therefore, in order to form a substantially trapezoidal light intensity distribution in the scanning direction while suppressing a decrease in illumination efficiency, it is preferable to focus the light at the position of the intermediate illumination plane 14 that is optically conjugate with the original 18 in the non-scanning direction, and to focus the light at the position of the field stop 13 in the scanning direction.

On the other hand, consider the case where the arrangement period of the element lenses of the entrance side integrator 101 is different from the arrangement period of the element lenses of the exit side integrator 102, as in this embodiment. In FIG. 3, the arrangement period of the element lenses of the entrance side integrator 101 is longer than the arrangement period of the element lenses of the exit side integrator 102.

In this case, the light beam that is perpendicularly incident on the center of each optical surface of the element lenses 101a of the entrance side integrator 101 enters a position offset from the center of the optical surface of the element lenses 102a that correspond to each of the element lenses 101a, as shown in FIG. 3. The light beam that is incident on the exit side integrator 102 is further refracted by each element lens 102a and then exits.

The incidence angle of the light beam on each element lens 102a of the exit side integrator 102 and the deviation of the incidence position of the light beam from the center of the optical surface both increase the further away from the optical axis. Therefore, the emission angle of the light beam from each element lens 102a of the exit side integrator 102 increases the further away from the optical axis. In other words, the emission angle of the light beam from each element lens 102a of the exit side integrator 102 changes monotonically according to the distance from the optical axis. As a result, the light beam that is perpendicularly incident on the center of each optical surface of the element lenses 101a of the entrance side integrator 101 is emitted toward the condenser lens 12 while being condensed.

If the light rays that are incident perpendicularly on the center of each optical surface of the element lenses 101a on the entrance side and emerge from each element lens 102a on the exit side are extended, they will intersect at a point O on the optical axis located at a distance s from (the principal point of) the condenser lens 12 on the original side, as shown in Figure 4. This is equivalent to the light source, as an object for the condenser lens 12, being located at a distance s from the condenser lens 12 on the original side.

Therefore, the focusing position of the light beam focused by the condenser lens 12 is located a distance d in front (towards the light source) of the intermediate illumination plane 14, which is located at a distance fc from the condenser lens 12. Therefore, the light intensity distribution in the scanning direction at a position a distance d towards the light source from the intermediate illumination plane 14 is an approximately rectangular distribution. On the other hand, at the intermediate illumination plane 14, since it is distance d away from the focusing position, the light intensity distribution in the scanning direction is approximately trapezoidal.

In addition, if the field stop 13 for defining the illumination area in the scanning direction and forming an approximately trapezoidal light intensity distribution is placed at a focusing position in the scanning direction (a position at a distance d from the intermediate illumination surface 14 toward the light source), the amount of light blocked by the field stop 13 is minimized. Therefore, it is possible to form an approximately trapezoidal light intensity distribution in the scanning direction while minimizing the decrease in illumination efficiency as much as possible.

The width L of the hypotenuse of the approximately trapezoidal light intensity distribution is expressed by the following formula (1) using the illumination NA (NAIL) at the intermediate illumination plane 14 and a distance d.
L=2d・tan[arcsin(NAIL)]...(1)

Therefore, the position of the field stop 13 or the distance d from the intermediate illumination surface 14 to the focusing position in the scanning direction can be determined from the width L of the hypotenuse of the trapezoid corresponding to the desired light intensity distribution and the illumination NA.

Note that the element lenses in the entrance side integrator 101 and the exit side integrator 102 differ only in their arrangement period in the non-scanning direction, but this does not result in a difference in the illumination NA at the intermediate illumination plane 14 between the scanning direction and the non-scanning direction.

5 is a schematic cross-sectional view showing, in an XZ cross section, the state of a light ray illuminating a point on the intermediate illumination plane 14. Since the condenser lens 12 has a rotationally symmetric refractive power, the light ray illuminating a point on the intermediate illumination plane 14 is the same in the scanning direction and the non-scanning direction. The illumination NA (NAIL) is determined by the diameter EA of the aperture of the aperture stop 11 and the focal length fc of the condenser lens 12, and is expressed by the following formula (2).
NAIL=EA/2÷fc...(2)

Therefore, if the aperture diameter EA of the aperture stop 11 and the focal length fc of the condenser lens 12 are the same in the scanning direction and the non-scanning direction (the aperture stop 11 and the condenser lens 12 are rotationally symmetric), the illumination NA will not differ between the scanning direction and the non-scanning direction.

Here, in order to make the arrangement period of the element lenses in the entrance side integrator 101 and the exit side integrator 102 different, the size of the element lenses in the entrance side integrator 101 and the size of the element lenses in the exit side integrator 102 may be made different. To make the arrangement period in the scanning direction different, the width of the element lenses in the scanning direction may be made different. Alternatively, the size of the element lenses in the entrance side integrator 101 and the exit side integrator 102 may be made the same, and the arrangement period of the element lenses may be adjusted by providing spacers between each element lens. By using spacers, the element lenses in the entrance side integrator 101 and the exit side integrator 102 can be made the same, which is expected to reduce the management costs and manufacturing costs of parts.

In this embodiment, the field stop 13 is disposed near the intermediate illumination plane 14, but this is not limiting. For example, the field stop 13 may be disposed near the original 18 that is optically conjugate with the intermediate illumination plane 14, or may be disposed on the original side of the intermediate illumination plane 14, rather than on the light source side of the intermediate illumination plane 14.

When the field stop 13 is placed closer to the original than the intermediate illumination plane 14, the configuration of the optical integrator 100 in the non-scanning direction is the same as the configuration of the optical integrator 100 when the field stop 13 is placed near the intermediate illumination plane 14. On the other hand, in the scanning direction, as shown in FIG. 6, the arrangement period of the element lenses of the entrance side integrator 101 is made shorter than the arrangement period of the element lenses of the exit side integrator 102.

As a result, light rays that are perpendicularly incident on the center of each optical surface of the element lenses 101a of the entrance-side integrator 101 are emitted toward the condenser lens 12 while diverging. If the light rays that are perpendicularly incident on the center of each optical surface of the element lenses 101a on the entrance side and emitted from each element lens 102a on the exit side are extended, they will intersect at a point O on the optical axis located at a distance s on the light source side from the condenser lens 12 (principal point), as shown in Figure 7. This is equivalent to the light source, as an object for the condenser lens 12, being located at a distance s on the light source side from the condenser lens 12.

Therefore, the focusing position of the light beam focused by the condenser lens 12 is located a distance d behind (towards the original) the intermediate illumination plane 14, which is located at a distance fc from the condenser lens 12. Therefore, the light intensity distribution in the scanning direction at a position a distance d towards the original from the intermediate illumination plane 14 is an approximately rectangular distribution. On the other hand, at the intermediate illumination plane 14, since it is distance d away from the focusing position, the light intensity distribution in the scanning direction is approximately trapezoidal.

In addition, if the field stop 13 is positioned at a distance d from the intermediate illumination surface 14 toward the original, the amount of light blocked by the field stop 13 will be minimized. Therefore, it is possible to form a substantially trapezoidal light intensity distribution in the scanning direction while minimizing the decrease in illumination efficiency as much as possible.

However, in a configuration in which light rays that are perpendicularly incident on the center of each optical surface of the element lenses 101a on the entrance side are emitted toward the condenser lens 12 while diverging, the effective diameter of the condenser lens 12 becomes large. Therefore, a configuration in which light rays that are perpendicularly incident on the center of each optical surface of the element lenses 101a on the exit side are emitted toward the condenser lens 12 while condensing is more advantageous in terms of manufacturing costs and the performance of the illumination optical system IL.

In this embodiment, in the optical integrator 100, the arrangement period of the element lenses in the entrance side integrator 101 and the exit side integrator 102 is made different in the scanning direction, but this is not limited to this. In other words, the arrangement period of the element lenses in the entrance side integrator 101 and the exit side integrator 102 may be made different in the non-scanning direction.

In this case, the field stop 13 is placed at a distance fc from the condenser lens 12. The intermediate illumination plane 14 is then set at a position a predetermined distance d away, and the arrangement period of the element lenses in the non-scanning direction is set so that the focusing position in the non-scanning direction coincides with the intermediate illumination plane 14.

The arrangement period of the element lenses in the entrance side integrator 101 and the exit side integrator 102 may be different for the scanning direction and the non-scanning direction. In this case, the positions of the field stop 13 and the intermediate illumination surface 14 may be set at positions that are a predetermined distance away from the position of the distance fc from the condenser lens 12. Then, the arrangement period of the element lenses in the non-scanning direction may be set for each of the scanning direction and the non-scanning direction so that the focusing positions in the scanning direction and the non-scanning direction by the condenser lens 12 coincide with the field stop 13 and the intermediate illumination surface 14, respectively.

For example, the field stop 13 is placed closer to the light source than the position at the distance fc from the condenser lens 12, and the intermediate illumination plane 14 is set closer to the original than the position at the distance fc from the condenser lens 12. In the scanning direction, the arrangement period of the element lenses of the entrance side integrator 101 is made longer than the arrangement period of the element lenses of the exit side integrator 102. In the non-scanning direction, the arrangement period of the element lenses of the entrance side integrator 101 is made shorter than the arrangement period of the element lenses of the exit side integrator 102.

Here, the relationship between the focal length fc of the condenser lens 12, the focusing position where the light beam perpendicularly incident on the center of each optical surface of the element lenses of the entrance-side integrator 101 is focused by the condenser lens 12, and the arrangement period of the element lenses will be described. If the light beam perpendicularly incident on the center of each optical surface of the entrance-side element lenses 101a and emerging from each of the exit-side element lenses 102a is extended, it will intersect at a point O on the optical axis located at a distance s from (the principal point of) the condenser lens 12 to the original side. The position of point O can be regarded as the object position of the condenser lens 12. In this case, the imaging position fc+d where the object at point O is imaged by the condenser lens 12 of focal length fc is expressed as follows, with the direction in which the light beam travels (positive direction of the X-axis) being positive:
1/(fc+d)=(1/s)+(1/fc)...(3)
That is, when s is infinite, d=0, and the focusing position coincides with the focal point of the condenser lens 12.

Next, let us consider the relationship between s and the arrangement period of the element lenses on the entrance side and the exit side of the optical integrator. If s is the distance h from the optical axis of a ray that is perpendicularly incident on the center of each optical surface of the element lens 101a on the entrance side, and the angle θ at which the ray emerges from the element lens 102a on the exit side, then when θ is sufficiently small, it can be expressed as follows:
s=h/θ...(4)
It is expressed as:

Here, if the arrangement period of the element lenses of the incident side integrator 101 is Pi, the element lens arranged on the optical axis is numbered 0, and the element lens on which the light ray is incident is numbered n in the arrangement direction, then h is given by:
h=n×Pi...(5)
It is expressed as:

Here, if the number of element lenses arranged in the periodic direction is odd, the element lens arranged on the optical axis is considered to be the 0th element, and the element lens arranged adjacent to that element lens is considered to be the 1st element. In other words, the distance from the optical axis to the ray perpendicularly incident on the center of the optical surface of the element lens arranged 1st is considered to be h = Pi.

On the other hand, when the number of element lenses arranged in the periodic direction is an even number, there is no element lens on the optical axis, so the element lens adjacent to the optical axis is considered to be the first element lens. Then, the distance from the optical axis of a ray that is perpendicularly incident on the center of the optical surface of that element lens is considered to be h = 0.5 x Pi.

On the other hand, θ is expressed using the focal length fo of the element lens 102a on the exit side, and the deviation e between the center of the optical surface of the element lens 102a on the exit side and the light ray that is perpendicularly incident on the center of the optical surface of the element lens 101a on the entrance side and then incident on each element lens 102a on the exit side.

When e is small enough,
θ=e/fo...(6)
It is expressed as:

In addition, the arrangement period of the element lenses of the exit side integrator 102 is Po,
e=(Po-Pi)×n...(7)
This is expressed as:

Using Equations 4 to 7,
s=(Pi×fо)/(Po-Pi)...(8)
It can be expressed as:

d can be calculated by substituting Equation 8 into Equation 3. In other words, the focusing position of the condenser lens 12 is calculated by the focal length fc of the condenser lens 12, the arrangement periods Pi and Po of the element lenses of the entrance side integrator 101 and the exit side integrator 102, and the focal length fo of the exit side element lens 102a. d can be changed by adjusting the arrangement periods Pi and Po of the element lenses of the entrance side integrator 101 and the exit side integrator 102.

Here, as the absolute value |Po-Pi| of the difference between the arrangement period Pi of the element lenses of the entrance side integrator 101 and the arrangement period Po of the element lenses of the exit side integrator 102 increases, the deviation e also increases. When |e| exceeds Po/2, the light rays that are perpendicularly incident on the center of each optical surface of the entrance side element lenses 101a will no longer be incident on the corresponding element lenses 102a on the exit side. This results in a decrease in illumination efficiency and a decrease in the uniformity of the light intensity distribution on the illuminated surface, which is undesirable.

Therefore,
|e|≦Po/2...(9)
It is preferable to satisfy the following:

In other words, let m be the number of element lenses in the optical integrator, and
Po/2≧｜(Po-Pi)｜×(m-1)/2...(10)
It is preferable to satisfy the following condition.

In this embodiment, an example has been described in which the entrance side integrator 101 and the exit side integrator 102 are each configured with five element lenses arranged in the scanning direction and five element lenses arranged in the non-scanning direction (5 x 5 array). However, the number of element lenses arranged is not limited to this, and may be more or less than a 5 x 5 array. The number of element lenses arranged may also be an odd number or an even number. Furthermore, the number of element lenses arranged in the scanning direction and the non-scanning direction may differ, and the arrangement period of the element lenses may be significantly different between the scanning direction and the non-scanning direction. In this way, the configuration of the element lenses can be selected as appropriate.

The element lenses constituting the optical integrator 100 are not limited to spherical lenses. In order to adjust the light intensity distribution on the illuminated surface, the element lenses may be aspheric lenses or diffractive lenses such as Fresnel zone plates and kinoforms. Furthermore, in order to adjust the aspect ratio of the light intensity distribution (the ratio of the width in the scanning direction to the width in the non-scanning direction of the light intensity distribution formed on the illuminated surface), the element lenses may be anamorphic lenses such as toric lenses and cylindrical lenses.

With reference to Figures 8 and 9, a case where the element lenses constituting the optical integrator are cylindrical lenses will be described. Figures 8 and 9 are schematic cross-sectional views showing the configuration from the optical integrator 200 to the intermediate illumination surface 14 when the element lenses constituting the optical integrator are cylindrical lenses. Figure 8 shows a cross section in the XY plane, and Figure 9 shows a cross section in the XZ plane.

The optical integrator 200 is composed of cylindrical lens arrays 201 and 202 on the entrance side and cylindrical lens arrays 203 and 204 on the exit side. The cylindrical lens arrays 201 and 203 are each cylindrical lens arrays in which element lenses having a curvature only in the scanning direction (Z direction) are arranged in the scanning direction. The cylindrical lens arrays 202 and 204 are each cylindrical lens arrays in which element lenses having a curvature only in the non-scanning direction (Y direction) are arranged in the non-scanning direction.

Each element lens of the cylindrical lens array 201 on the incident side corresponds to each element lens of the cylindrical lens array 203 on the exit side. Also, each element lens of the cylindrical lens array 202 on the incident side corresponds to each element lens of the cylindrical lens array 204 on the exit side.

The light incident on the optical integrator 200 is split into a number of light beams in the scanning direction and non-scanning direction by the cylindrical lens arrays 201 and 202 on the incident side. The light beams exit from the individual element lenses of the cylindrical lens arrays 201 and 202 on the incident side, enter the element lenses of the corresponding cylindrical lens arrays 203 and 204 on the exit side, and are emitted toward the condenser lens 12.

The aperture stop 11 is disposed near the exit surface of the optical integrator 200 (exit side cylindrical lens array 204). The position of the aperture stop 11 corresponds to the pupil plane of the condenser lens 12.

The light emitted from the optical integrator 200 is condensed by the condenser lens 12 and illuminates the intermediate illumination surface 14 in a superimposed manner. As shown in FIG. 8, in the non-scanning direction, the arrangement period of the element lenses of the cylindrical lens array 201 on the incident side is equal to the arrangement period of the element lenses of the cylindrical lens array 2042 on the exit side. Therefore, the light beams perpendicularly incident on the center of the optical surface of each element lens of the cylindrical lens array 202 on the incident side are perpendicularly emitted from the center of the optical surface of the corresponding element lens of the cylindrical lens array 204 on the exit side. In other words, the light beams perpendicularly incident on the center of each optical surface of the element lenses of the cylindrical lens array 202 on the incident side are respectively emitted from the optical integrator 200 parallel to the optical axis (X-axis) of the illumination optical system IL. The light emitted parallel to the optical axis of the illumination optical system IL is focused via a condenser lens 12 having a focal length of fc at a position a distance fc from the condenser lens 12 (principal point).

The intermediate illumination plane 14 is located at a distance fc from the condenser lens 12 (principal point). Therefore, the light intensity distribution in the non-scanning direction at the intermediate illumination plane 14 is a substantially rectangular distribution, as shown in FIG. 8.

Next, the light intensity distribution in the scanning direction on the intermediate illumination surface 14 will be described with reference to FIG. 9. As shown in FIG. 9, the arrangement period of the element lenses of the cylindrical lens array 201 on the incident side is longer than the arrangement period of the element lenses of the cylindrical lens array 2042 on the exit side in the scanning direction. Therefore, the light beam that is perpendicularly incident on the center of each optical surface of the element lenses of the cylindrical lens array 201 on the incident side enters the cylindrical lens array 203 on the exit side as shown in FIG. 9. As a result, the light beam enters a position shifted from the center of the optical surface of the corresponding element lens of the cylindrical lens array 203 on the exit side corresponding to each of the element lenses of the cylindrical lens array 201 on the incident side. Then, the light beam that enters the cylindrical lens arrays 203 and 204 on the exit side is further refracted by each element lens and exits.

The angle of incidence of light rays on each element lens of the cylindrical lens array 203 on the exit side, and the amount of deviation in the scanning direction of the incident position of the light rays from the center of the optical surface, both increase the further away from the optical axis toward the periphery. Therefore, the exit angle of light rays from each element lens of the cylindrical lens array 203 on the exit side increases the further away from the optical axis. In other words, the exit angle of light rays from each element lens of the cylindrical lens array 203 on the exit side changes monotonically according to the distance from the optical axis. As a result, light rays that are perpendicularly incident on the center of each optical surface of the element lenses of the cylindrical lens array 201 on the entrance side are emitted toward the condenser lens 12 while being condensed.

Therefore, the focusing position of the light beam focused by the condenser lens 12 is located a distance d in front (towards the light source) of the intermediate illumination plane 14, which is located at a distance fc from the condenser lens 12. Therefore, the light intensity distribution in the scanning direction at a position a distance d towards the light source from the intermediate illumination plane 14 is an approximately rectangular distribution. On the other hand, at the intermediate illumination plane 14, since it is distance d away from the focusing position, the light intensity distribution in the scanning direction is approximately trapezoidal.

In addition, if the field stop 13 for defining the illumination area in the scanning direction and forming an approximately trapezoidal light intensity distribution is placed at a focusing position in the scanning direction (a position at a distance d from the intermediate illumination surface 14 toward the light source), the light blocked by the field stop 13 can be minimized. Therefore, even if the optical integrator is configured with a cylindrical lens array, it is possible to form an approximately trapezoidal light intensity distribution in the scanning direction while minimizing the decrease in illumination efficiency as much as possible.

In this embodiment, cylindrical lens array 201, cylindrical lens array 202, cylindrical lens array 203, and cylindrical lens array 204 are arranged in order from the entrance side to the exit side. Cylindrical lens array 201 is a cylindrical lens array arranged in the scanning direction of the entrance side, and cylindrical lens array 202 is a cylindrical lens array arranged in the non-scanning direction of the entrance side. Cylindrical lens array 203 is a cylindrical lens array arranged in the scanning direction of the exit side, and cylindrical lens array 204 is a cylindrical lens array arranged in the non-scanning direction of the exit side. However, this is not limited to such an arrangement, and various arrangements are possible as long as the relationship between the entrance side and the exit side is reversed.

For example, cylindrical lens array 202 arranged in the non-scanning direction on the incident side may be arranged closer to the light source than cylindrical lens array 201 arranged in the scanning direction on the incident side. Also, cylindrical lens array 204 arranged in the non-scanning direction on the exit side may be arranged closer to the light source than cylindrical lens array 203 arranged in the scanning direction on the exit side.

Furthermore, the cylindrical lens arrays 201 and 203 arranged in the scanning direction on the incident side and the exit side may be arranged closer to the light source than the cylindrical lens array 202 arranged in the non-scanning direction on the incident side.

In addition, in this embodiment, the individual element lenses constituting the optical integrator 100 or 200 are each divided, but this is not limited to the above. For example, multiple element lenses may be integrally formed in one optical element using techniques such as cutting, molding, and etching. The configuration of the optical integrator can be modified and changed in various ways within the scope of its gist.

In this way, in this embodiment, in the illumination optical system IL, a light intensity distribution that reduces exposure unevenness caused by the effects of pulse oscillation can be achieved with little light loss and without causing differences in the transfer characteristics of the pattern transferred to the substrate in the scanning direction and non-scanning direction. Furthermore, an exposure apparatus EX having such an illumination optical system IL can provide high-quality devices (semiconductor elements, liquid crystal display elements, flat panel displays, etc.) with high throughput and good economical performance.

The manufacturing method of the article in the embodiment of the present invention is suitable for manufacturing articles such as flat panel displays, liquid crystal display elements, semiconductor elements, and MEMS. The manufacturing method includes a step of exposing a substrate coated with a photosensitive agent using the above-mentioned exposure apparatus EX, and a step of developing the exposed photosensitive agent. In addition, a circuit pattern is formed on the substrate by performing an etching process, an ion implantation process, etc., using the developed photosensitive agent pattern as a mask. These steps of exposure, development, etching, etc. are repeated to form a circuit pattern consisting of multiple layers on the substrate. In a post-process, dicing (processing) is performed on the substrate on which the circuit pattern is formed, and chip mounting, bonding, and inspection processes are performed. In addition, the manufacturing method may include other well-known processes (oxidation, film formation, deposition, doping, planarization, resist stripping, etc.). The manufacturing method of the article in the present embodiment is advantageous in at least one of the performance, quality, productivity, and production cost of the article compared to the conventional method.

The invention is not limited to the above-described embodiment, and various modifications and variations are possible without departing from the spirit and scope of the invention. Therefore, the following claims are appended to disclose the scope of the invention.

EX exposure apparatus IL illumination optical system 100 optical integrator 101 incident side integrator 101a element lens 102 exit side integrator 102a element lens

Claims (13)

An illumination optical system that illuminates an illuminated surface,
an optical integrator that forms a secondary light source with light from the light source;
the optical integrator includes an incident-side optical element having a plurality of first optical elements arranged thereon, and an exit-side optical element including a plurality of second optical elements arranged corresponding to the plurality of first optical elements,
an illumination optical system characterized in that the plurality of first optical elements and the plurality of second optical elements are periodically arranged in a first direction and a second direction intersecting the first direction, and an arrangement period of the plurality of first optical elements and an arrangement period of the plurality of second optical elements are different in at least one of the first direction and the second direction. The illumination optical system according to claim 1, characterized in that each of the incident-side optical element and the exit-side optical element is composed of a fly-eye lens having refractive power in the first direction and the second direction. a condenser lens for illuminating the illumination surface with light from the optical integrator;
3. The illumination optical system according to claim 1, wherein the optical integrator is configured to make the focusing position of the light emerging from the condenser lens different in the first direction from the focusing position in the second direction. The illumination optical system according to any one of claims 1 to 3, characterized in that the optical integrator is configured such that the angle of a light ray that is perpendicularly incident on the center of each of the optical surfaces of the plurality of first optical elements and emerges from each of the plurality of second optical elements changes monotonically from the center to the periphery of the optical surface of the optical integrator in at least one of the first direction and the second direction. When the arrangement period of the plurality of first optical elements is Pi, the arrangement period of the plurality of second optical elements is Po, and the number of the arrangements of the first optical elements and the second optical elements is m,
Po/2≧｜(Po-Pi)｜×(m-1)/2
5. The illumination optical system according to claim 1, wherein the following condition is satisfied: An illumination optical system that illuminates an illuminated surface,
an optical integrator that forms a secondary light source with light from the light source;
the optical integrator includes a first optical element group on an incident side and a second optical element group on an exit side,
the first optical element group includes a first optical element and a second optical element in which a plurality of first optical elements are arranged,
The second optical element group is
a third optical element including a plurality of second optical elements arranged corresponding to each of the plurality of first optical elements of the first optical element;
a fourth optical element including a plurality of second optical elements arranged corresponding to each of the plurality of first optical elements of the second optical element;
The first optical element includes the plurality of first optical elements arranged periodically in a first direction,
The second optical element is such that the plurality of first optical elements are periodically arranged in a second direction intersecting the first direction,
The third optical element includes the second optical elements arranged periodically in the first direction,
The fourth optical element is configured such that the plurality of second optical elements are periodically arranged in the second direction,
the first optical element and the third optical element are cylindrical lenses having a refractive power in the first direction,
the second optical element and the fourth optical element are cylindrical lenses having a refractive power in the second direction,
An illumination optical system, characterized in that an arrangement period of the plurality of first optical elements and an arrangement period of the plurality of second optical elements are different in at least one of the first direction and the second direction. 1. An exposure apparatus that exposes a substrate through an original while moving the original and the substrate in a scanning direction, comprising:
an illumination optical system according to claim 1 , which illuminates the original placed on an illumination surface;
a projection optical system that projects a pattern of the original onto the substrate;
An exposure apparatus comprising: The exposure apparatus according to claim 7, characterized in that the illumination optical system illuminates the original using light from a pulsed light source. a masking unit disposed on a conjugate plane of the illumination surface and defining an illumination area on the illumination surface;
9. The exposure apparatus according to claim 7, further comprising: a field stop that is arranged at a position away from a conjugate plane of the illumination surface in the optical axis direction of the illumination optical system and that defines an illumination area in the scanning direction. the field diaphragm is disposed closer to the light source than the masking unit;
10. The exposure apparatus according to claim 9, wherein an arrangement period of the plurality of first optical elements is longer than an arrangement period of the plurality of second optical elements in the scanning direction. the field stop is disposed closer to the original than the masking unit,
10. The exposure apparatus according to claim 9, wherein an arrangement period of the plurality of first optical elements is shorter than an arrangement period of the plurality of second optical elements in the scanning direction. the illumination optical system includes a condenser lens that illuminates the original with light from an optical integrator;
12. The exposure apparatus according to claim 9, wherein in the illumination optical system, a focusing position in the scanning direction of the condenser lens of a light beam perpendicularly incident on the center of each of the optical surfaces of a plurality of first optical elements of an incident-side optical element coincides with the position of the field stop, and a focusing position in a direction intersecting the scanning direction of the condenser lens coincides with the illuminated surface. exposing a substrate using an exposure apparatus according to any one of claims 7 to 12;
developing the exposed substrate;
producing an article from the developed substrate;
A method for producing an article, comprising the steps of:

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