JP7116368B2 - Illumination apparatus and method, exposure apparatus and method, and device manufacturing method - Google Patents

Description

The present invention relates to an illumination technique for illuminating an object with illumination light, an exposure technique using the illumination technique, and a device manufacturing technique using the exposure technique.

Conventionally, in the photolithography process for manufacturing electronic devices such as liquid crystal display devices, semiconductor devices, and thin-film magnetic heads, a mask pattern illuminated by an illumination device is projected onto a photosensitive agent such as photoresist through a projection optical system. An exposure apparatus is used to transfer the coating onto a substrate such as a plate.
As a conventional lighting device, it has an optical system consisting of a plurality of conical or pyramidal optical members for controlling the cross-sectional shape of the illumination light beam from the mercury lamp, and increases the efficiency of using the illumination light when performing annular illumination. For this reason, an illumination device is used that controls the cross-sectional shape of an illumination light flux using its optical system in accordance with the shape of an annular illumination light source (see, for example, Patent Document 1).

Illumination methods other than annular illumination are also used in the exposure apparatus. In such a case as well, it is desirable to take into consideration how to improve the utilization efficiency of the illumination light.

U.S. Pat. No. 5,719,704

According to a first aspect, there is provided an illumination device for illuminating a mask, comprising a light source for generating illumination light, an optical system for adjusting the tilt angle of the illumination light, and condensing the illumination light via the optical system. a first condensing optical system that emits light; an optical member that emits the illumination light through the optical system to the first condensing optical system while maintaining the tilt angle of the illumination light; comprising an aperture stop for adjusting the numerical aperture of the illumination light emitted from the optical optical system, and a second condensing optical system for guiding the illumination light with the adjusted numerical aperture to the mask, the first condensing optical system The system has an optical element group including a plurality of optical elements that homogenize the illuminance distribution of the illumination light, and the illumination light that has passed through the optical member passes through the plurality of optical elements of the first condensing optical system. distributed over a region wider than the size of the entrance of the element, the optical member is configured by bundling a plurality of optical fiber strands, the number of the optical fiber strands constituting the exit end of the optical member, and the optical An illumination device is provided in which the aperture stop adjusts the numerical aperture of the illumination light within a range in which the number of light source images formed at the exit end of each of the plurality of optical elements of the element group is approximately equal .

According to a second aspect, there is provided an exposure apparatus for exposing a mask pattern onto a substrate, comprising an illumination device according to the first aspect, and a projection device for forming an image of the mask pattern illuminated by the illumination device onto the substrate. An exposure apparatus is provided comprising: an optical system;
According to a third aspect, there is provided an illumination method for illuminating a mask, comprising adjusting the tilt angle of illumination light generated from a light source, and adjusting the tilt angle of the illumination light to emitting through an optical member that maintains the tilt angle, concentrating the emitted illumination light, adjusting the numerical aperture of the illumination light, and adjusting the numerical aperture of the illumination light to the mask, and collecting the illumination light includes homogenizing the illuminance distribution of the illumination light using an optical element group including a plurality of optical elements, and The illumination light that has passed through the member is distributed over a region wider than the size of the entrance apertures of the plurality of optical elements. The numerical aperture of the illumination light is adjusted within a range in which the number of the constituent optical fiber strands and the number of light source images formed at the exit end of each of the plurality of optical elements of the optical element group are approximately equal. , a lighting method is provided.

According to a fourth aspect, there is provided an exposure method for exposing a mask pattern onto a substrate, comprising illuminating the mask using the illumination method of the third aspect, and forming an image of the illuminated mask pattern. forming on a substrate.

1 is a perspective view showing a schematic configuration of an exposure apparatus according to one embodiment; FIG. It is a figure which shows the structure of the illuminating device which concerns on one Embodiment. FIG. 2 is a diagram showing configurations of a partial projection optical system and a stage system according to one embodiment; 4 is a flow chart showing an example of an illumination method and an exposure method; (A) is a diagram showing the main part of the illumination device when the σ value of the illumination light is large, and (B) is a diagram showing the main part of the illumination device when the σ value of the illumination light is small. (A) shows the main part of the illumination device of the comparative example, (B) shows the light intensity distribution at the incident end of the light guide fiber, and (C) shows the light intensity distribution at the incident end of the fly-eye lens. It is a diagram. 7A is a diagram showing a partial illumination optical system, and FIG. 7B is an enlarged view showing the exit end of the light guide fiber of FIG. 7A. (A) is a diagram showing an example of the aperture of the aperture diaphragm during annular illumination, (B) is a diagram showing an example of the aperture of the aperture diaphragm during large-σ illumination, and (C) is a diagram of the aperture diaphragm during small-σ illumination. It is a figure which shows an example of opening. (A) and (B) are conceptual diagrams showing an exit surface of a fly's eye lens. (A) is a diagram showing a configuration example of a variable power optical system, (B) is a diagram showing a configuration example of a switching optical system, and (C) is a diagram showing an example of an optical member for controlling the tilt angle of a laser beam. is. It is a flow chart which shows an example of an electronic device manufacturing method.

One embodiment will be described with reference to FIGS. 1-9B. FIG. 1 is a perspective view showing an exposure apparatus EX according to this embodiment. In this embodiment, the exposure apparatus EX synchronously moves a mask M and a flat plate P as a substrate coated with a photosensitive agent with respect to a projection optical system PL having a plurality of catadioptric partial projection optical systems. A step-and-scan type exposure apparatus for transferring an image of a pattern formed on a mask M onto a plate P will be described.

In the following description, in FIG. 1, the X-axis and the Y-axis are taken so as to be orthogonal within a plane parallel to the plate P, and the Z-axis is taken perpendicular to the plane (XY plane). As an example, the XY plane is set parallel to the horizontal plane, and the Z axis is set parallel to the vertical line. Moreover, in this embodiment, the scanning direction, which is the direction in which the mask M and the plate P are synchronously moved, is set in the direction parallel to the X axis (X direction). At this time, the non-scanning direction perpendicular to the scanning direction is the direction parallel to the Y axis (Y direction).

The exposure apparatus EX includes an illuminator ILA for illuminating the pattern surface (hereinafter also referred to as the mask surface) of the mask M supported by the mask stage MST (see FIG. 3) with illumination light having a uniform illuminance distribution; It has a system PL and a control section 30 comprising a computer for controlling the operation of the entire apparatus. The illumination device ILA includes a first row of a plurality of (here, four) illumination areas 21a, 21c, 21e, and 21g arranged along the Y direction (non-scanning direction) on the mask surface, and a first row of illumination areas 21a, 21c, 21e, and 21g. A plurality of (here, three) illumination regions (not shown) in the second row located between the illumination regions 21a to 21g are illuminated in a state shifted in the scanning direction (X direction) with respect to the illumination regions 21a to 21g. . Although the illumination device ILA illuminates the seven illumination areas on the mask surface in this way, the arrangement and number of the illumination areas are arbitrary.

In this embodiment, since a field stop is arranged in the projection optical system PL as will be described later, the illumination regions 21a to 21g may have a shape slightly larger than the image of the field stop on the mask surface. The illumination device ILA, as shown in FIG. 2, has three light sources 2a, 2b, and 2c consisting of ultra-high pressure mercury lamps. Illumination lights 3a, 3b and 3c emitted from the light sources 2a, 2b and 2c are collected by elliptical mirrors 4a, 4b and 4c, respectively. The light sources 2a-2c are arranged at the first focal positions of the elliptical mirrors 4a-4c, and the light source images 5a, 5b, 5c of the light sources 2a, 2b, 2c are located at the second focal positions of the elliptical mirrors 4a, 4b, 4c. is formed. During periods in which the mask M is not illuminated, the illumination lights 3a, 3b and 3c are blocked by shutters (not shown) arranged near the second focal points of the elliptical mirrors 4a, 4b and 4c. The number of light sources 2a, 2b, and 2c is arbitrary, and the number of light sources may be one (for example, only light source 2a).

Illumination lights 3a, 3b, 3c emitted as diverging lights from the light source images 5a, 5b, 5c are condensed at the incident ends 12a, 12b, 12c of the light guide fiber 10 by the variable magnification optical systems 8a, 8b, 8c, respectively. be. The variable-magnification optical systems 8a, 8b, and 8c respectively form images 9a, 9b, and 9c of the light source images 5a, 5b, and 5c with variable magnification (hereinafter referred to as light source images) on the entrance surfaces of the entrance ends 12a, 12b, and 12c. do. The variable magnification optical systems 8a to 8c are, for example, zoom lenses having a front lens group system 6 movable along the optical axis by a driving section 6a and a rear lens group system 7 movable along the optical axis by a driving section 7a. It is a lens (zoom optical system). The control unit 30 controls the positions of the front lens group 6 and the rear lens group 7 via the driving units 6a and 7a, thereby controlling the magnification of the variable magnification optical systems 8a to 8c.

Here, y1 is the height (image height) of the light source image 9a when the variable magnification optical system 8a is at the minimum magnification, and α1 is the maximum tilt angle of the illumination light 3a forming the light source image 9a with respect to the optical axis. do. Let y2 be the height of the light source image 9a when the magnification of the variable-magnification optical system 8a is higher than the maximum magnification, and α2 be the maximum tilt angle of the illumination light 3a with respect to the optical axis at this time. The maximum tilt angle is also 1/2 of the so-called cone angle. When the light intensity distribution of the light source image 9a is a normal distribution (Gaussian distribution), the height of the light source image 9a means that the light intensity in the light intensity distribution is about 10% to 50% of the maximum intensity. It is also possible to consider it as the interval between the positions where the distance is equal to or, for example, about 30%. Assuming that the variable magnification optical system 8a satisfies the sine condition, the following relationship holds.

y1·sinα1=y2·sinα2 (1)
Here, since the height y2 is higher than the height y1, the tilt angle α2 is smaller than the tilt angle α1 according to Equation (1). Therefore, the variable magnification optical systems 8a to 8c are optical systems that can control or adjust the maximum tilt angle of the illumination light incident on the incident ends 12a to 12c by forming the light source images 9a to 9c with variable magnification. be. In this embodiment, the variable magnification optical systems 8a to 8c are controlled to have the same magnification.

A light guide fiber 10 as a light transmission member is a fiber bundle configured by randomly bundling a large number of optical fiber strands 11 (see FIG. 5A), and has three incident ends 12a, 12b and 12c. , and a plurality (here, seven) of exit ends (only exit ends 14a and 14B are shown in FIG. 2) corresponding to a plurality (here, seven) of illumination areas, and incident ends 12a to 12c. Illumination lights 3a to 3c received from are distributed to a plurality of exit ends thereof. As a result, at least part of each of the illumination lights 3a to 3c is emitted from each of the plurality of emission ends, and the illumination device ILA can mix and emit the illumination lights emitted from the plurality of light sources 2a to 2c. can. It is assumed here that the light guide fiber 10 is configured to distribute the illumination light received from the incident ends 12a to 12c to a plurality of exit ends at substantially equal light quantity ratios.

Further, the optical fiber strand 11 maintains the inclination angle of the incident light flux so that the maximum inclination angle of the incident light flux and the maximum inclination angle of the emitted light flux are approximately equal to each other. is. Therefore, the maximum tilt angles of the illumination lights 3a to 3c incident on the incident ends 12a to 12c of the light guide fiber 10 and the maximum tilt angles of the illumination lights emitted from the plurality of exit ends are substantially equal. Also, as an example, the illumination lights emitted from the variable magnification optical systems 8a to 8c enter the corresponding incident ends 12a to 12c in a state in which the principal rays are parallel to the optical axis, that is, in a so-called telecentric state. . As a result, the illumination light can be uniformly incident within the range of incident angles that can be transmitted by the respective optical fiber strands 11 of the light guide fiber 10 . Further, the maximum tilt angle of the illumination light emitted from the variable magnification optical systems 8a to 8c is controlled within a range smaller than the maximum transmittable incident angle (tilt angle) of the optical fiber line 11. FIG.

Each of the illumination lights 20a, 20c, etc. emitted from the plurality of exit ends 14a, 14b, etc. of the light guide fiber 10 illuminates the partial illumination areas 21a, 21c, etc. of the mask M (seven here). The light enters the partial illumination optical systems IL1 to IL7 (the partial illumination optical systems IL2 and IL4 to IL7 are omitted from the drawing) having the same configuration. The partial illumination optical systems IL1 to IL7 are associated with partial projection optical systems PL1 to PL7, respectively, which will be described later, and are arranged in a staggered pattern along the non-scanning direction (Y direction) orthogonal to the scanning direction.

In the partial illumination optical systems IL1 and IL3, the illumination light beams 20a . The beams 20c are condensed by the input lens 15, which is a collimating lens, and converted into parallel beams, and then enter the fly-eye lens 16, which is an optical integrator. Illumination lights 20a and 20c incident on the fly-eye lens 16 are wavefront-divided by a large number of lens elements constituting the fly-eye lens 16, and a plurality of light beams are formed on the rear focal plane (exit pupil plane of the illumination optical system) in the vicinity of the exit surface thereof. A secondary light source (surface light source) is formed by a light source image of . An aperture stop 17 is arranged in the rear focal plane. The control unit 30 controls the size and shape of the aperture of the aperture stop 17 via the driving unit 17a. Thereby, the numerical aperture NA of the illumination light that illuminates the mask M by the partial illumination optical systems IL1 and IL3 can be controlled. In the following, the numerical aperture NA of the illumination light is expressed using a σ value (a value obtained by dividing the numerical aperture of the illumination light illuminating the mask by the numerical aperture of the projection optical system on the mask side), which is a coherence factor. . Therefore, the aperture stop 17 can also be called a σ stop. When annular illumination is performed, the aperture diaphragm 17 may be replaced with an annular illumination aperture diaphragm (not shown) having an annular aperture whose size is variable.

The illumination lights 20a and 20c emitted from the aperture of the aperture stop 17 illuminate the corresponding illumination areas 21a and 21c on the mask M via the condenser lens 18 with a substantially uniform illuminance distribution. The configuration of the partial illumination optical systems IL2 and IL4 to IL7 (not shown) is the same as that of the partial illumination optical system IL1. A corresponding illumination area is illuminated with a substantially uniform illuminance distribution.

Illumination light from the illumination regions 21a to 21g on the mask M corresponding to the partial illumination optical systems IL1 to IL7 respectively enters the partial projection optical systems PL1 to PL7. FIG. 3 is a diagram showing the configuration of the partial projection optical system PL1. As shown in FIG. 3, the partial projection optical system PL1 includes a first catadioptric optical system PL11 that forms an intermediate image of a pattern provided in the illumination region 21a corresponding to the mask surface at the opening of the field stop 22. , in cooperation with the first catadioptric optical system PL11, the second catadioptric optical system PL11 forms an image of the pattern of the mask M on the exposure area 23a of the plate P supported by the plate stage PST as a 1:1 erect image. and a system PL12. Further, the partial projection optical systems PL2 to PL7 have the same configuration as the partial projection optical system PL1, and form the images of the patterns formed in the corresponding illumination regions on the mask surface onto the plate P. . The partial projection optical systems PL1 to PL7 are arranged in a houndstooth pattern along the non-scanning direction.

In FIG. 2, the controller 30 is connected to a power supply device 32 that supplies power to the light sources 2a to 2c. The control unit 30 turns on the light sources 2a to 2c via the power supply device 32 when exposing the plate P or calibrating the illumination device ILA. If the required exposure amount is small, it is possible to turn on at least one of the light sources 2a to 2c.

As a basic operation during exposure, the control unit 30 sets illumination conditions including the σ value of the illumination light and the magnification of the variable magnification optical systems 8a to 8c (details will be described later), and turns on the light sources 2a to 2c. Then, the mask M is illuminated by the illumination device ILA, and the mask stage MST supporting the mask M and the plate stage PST supporting the plate P are driven to move the mask M and the plate P to the partial projection optical systems PL1 to PL7. By repeating synchronous movement in the scanning direction (scanning exposure) and moving the plate P in the non-scanning direction or the scanning direction (step movement), the pattern formed on the mask M by the step-and-scan method. A plurality of exposed areas of plate P are exposed with an image of .

Further, when calibrating the illumination device ILA, as an example, illuminance sensors (not shown) are arranged at a plurality of positions in each of the illumination areas 21a to 21g. Then, when the light sources 2a to 2c are turned on to change the σ value and when the magnification of the variable power optical systems 8a to 8c is changed, the illuminance distribution measured by the illuminance sensor is equal to the target. By adjusting the variable magnification optical systems 8a to 8c and the partial illumination optical systems IL1 to IL7 so that the distribution is within a predetermined allowable range, the illuminance distribution becomes uniform.

An example of the operation of the illumination method including the setting of the illumination conditions of the illumination apparatus ILA of this embodiment and the exposure method using the exposure apparatus EX will be described below with reference to the flowchart of FIG. Its operation is controlled by the controller 30 .
First, while the light sources 2a to 2c are not turned on, in step 102 in FIG. An aperture stop 17 is used to control the σ value of the illumination light. In the case of annular illumination, the aperture diaphragm 17 may be replaced with an aperture diaphragm (not shown) for annular illumination. Here, as shown in FIG. 5A, the diameter of, for example, the circular aperture of the aperture diaphragm 17 is set to the maximum value, and the σ value is set to the maximum value NA1 (for example, about 0.8 to 0.9). It is assumed that large σ illumination is performed. In the case of large σ illumination, the illumination light emitted from the exit end 14a of the light guide fiber 10 becomes a parallel beam through the input lens 15, which is the widest range of the incident surface of the fly-eye lens 16 (aperture stop 17). (slightly wider than the area facing the largest aperture of the ). Therefore, it is necessary to set the maximum tilt angle of the illumination light emitted from the emission end 14a to the maximum value within the adjustable range.

Then, in step 104, according to the σ value set by the aperture stop 17, the magnification of the variable magnification optical systems 8a to 8c and the light source images 9a to 9c formed at the incident ends 12a to 12c of the light guide fiber 10 are changed. The maximum inclination angles of the illumination lights 3a to 3c to be formed are adjusted. When an aperture stop for annular illumination is used as the aperture stop 17, the σ value determined by the outer diameter of the annular aperture may be used as the σ value. Here, since the σ value is set to the maximum value NA1, the magnification of the variable-magnification optical systems 8a-8c is set to the minimum value within the variable-magnification range, and the maximum tilt angles of the illumination lights 3a-3c are adjusted. It is set to the maximum value α1 within the possible range. In FIG. 5A, the focal length of the variable magnification optical system 8a is set to f1, and the height of the light source image 9a is set to the minimum value y1 within the adjustable range.

In each optical fiber strand 11 constituting the light guide fiber 10, the maximum tilt angle of the incident light flux and the maximum tilt angle of the exit light flux are substantially equal. Therefore, when the aperture diameter of the aperture diaphragm 17 is maximized, the illumination light 20a emitted from the exit end 14a of the light guide fiber 10 passes through the input lens 15 and the fly-eye lens 16 capable of illuminating the maximum aperture. incident on the region of the incident surface of . Also, the light intensity distribution (illuminance distribution) D1 of the light source image 9a formed at the incident end 12a has a substantially axially symmetrical normal distribution shape, and is strong in the central portion and sharply weakens toward the peripheral portion. When the height of the light source image 9a is the minimum value y1, the portion of the light intensity distribution D1 that is about 10% or less of the maximum value spreads outside the incident surface of the incident end 12a. A portion (more precisely, a light flux obtained by randomly synthesizing the incident illumination lights 3a to 3c) is emitted from the exit end 14a and the like.

The light intensity distribution C31 of the illumination light 20a emitted from the exit end 14a on the incident surface of the fly-eye lens 16 is a substantially axially symmetrical distribution in which the intensity increases slightly as the distance from the optical axis increases, and the intensity decreases sharply outside the optical axis. . The light intensity distribution C31 can be regarded as having a substantially uniform value in the region facing the aperture of the aperture stop 17, and the illumination emitted from the emission end 14a at a maximum inclination angle of approximately α1 to the aperture of the aperture stop 17. Most of the light 20a is incident. For this reason, the illumination light utilization efficiency (hereinafter referred to as Also called illumination efficiency) is high.

Then, in step 106, the light sources 2a to 2c are turned on, and the illumination light 3a to 3c from the light sources 2a to 2c is used by the illumination device ILA to illuminate the variable magnification optical systems 8a to 8c, the light guide fiber 10, the partial illumination optical systems IL1 to The mask M is illuminated via the input lens 15 of IL8, the fly eye lens 16, the aperture stop 17 and the condenser lens 18. FIG. Then, in step 108, the plate P is exposed by synchronously moving the mask M and the plate P with respect to the projection optical system PL while exposing the plate P with the image of the pattern of the mask M by the projection optical system PL. . At this time, since the mask M can be illuminated with high illumination efficiency using the illumination light having the maximum σ value, the pattern formed on the mask M can be exposed onto the plate P with high throughput (productivity) and optical accuracy.

Next, for example, when the pattern of the mask M to be exposed includes a fine isolated pattern such as a pattern of contact holes, in order to perform so-called small σ illumination, in step 102, as shown in FIG. As shown, the diameter of, for example, the circular aperture of the aperture stop 17 is set to the minimum value, and the σ value is set to the minimum value NA2 (eg, approximately 0.05 to 0.1). In this case, the illumination light emitted from the exit end 14a becomes a parallel light beam through the input lens 15, and the smallest area of the incident surface of the fly-eye lens 16 (the area facing the smallest aperture of the aperture stop 17) Therefore, the maximum tilt angle of the illumination light emitted from the emission end 14a may be set to the minimum value α2 within the adjustable range. Therefore, in step 104, the magnification of the variable-magnification optical systems 8a-8c is set to the maximum value within the variable-magnification range, and the maximum tilt angle of the illumination lights 3a-3c is set to the minimum value α2. In FIG. 5B, the focal length of the variable magnification optical system 8a is set to f2, and the height of the light source image 9a is set to the maximum value y2.

At this time, the light intensity distribution D2 of the light source image 9a formed at the incident end 12a has a substantially axially symmetrical normal distribution obtained by enlarging the light intensity distribution D1 of FIG. 5(A) with a magnification ratio of y2/y1. In the light intensity distribution D2, a portion of about 35% or less of the maximum value spreads outside the incident surface of the incident end 12a, and about 60%, for example, of the incident illumination light 3a to 3c is emitted to the exit end 14a. is ejected from If the height y2 of the light source image 9a is the interval of the portion where the light intensity is approximately 30% of the maximum value, the light source image 9a at the height y2 is slightly larger than the width of the incident end 12a.

However, in this case, the maximum tilt angle of the illumination light 20a emitted from the emission end 14a is approximately the minimum value α2, and most of the illumination light 20a enters the fly-eye lens 16 via the input lens 15. In the plane, it is incident on the area facing the smallest aperture of the aperture stop 17 . In this case, the light intensity distribution C11 of the illumination light 20a emitted from the exit end 14a on the incident surface of the fly-eye lens 16 is substantially axially symmetrical as if the light intensity distribution C31 in FIG. 5A was compressed in the radial direction. is the distribution of The light intensity distribution C11 can be regarded as having a substantially uniform value in the region facing the minimum aperture of the aperture stop 17, and the light emitted from the exit end 14a to the aperture of the aperture stop 17 has a maximum tilt angle of approximately α2. Most of the illuminating light 20a is incident. Therefore, even if the illumination light 3a incident on the incident end 12a loses some amount of light, the illumination light 3a of the illumination light 20a that passes through the minimum aperture of the aperture stop 17 and enters the mask M via the condenser lens 18 is utilization efficiency is high. By performing steps 106 and 108 thereafter, a pattern including, for example, an isolated pattern can be exposed onto the plate P with high throughput and high accuracy.

Here, as a comparative example, as shown in FIG. 6A, the magnification of the variable-magnification optical system 8a is set to the minimum as in the case of FIG. value α1), and the aperture stop 17 sets the σ value to the minimum value NA2. In this comparative example, the light intensity distribution C31 of the illumination light 20a emitted from the emission end 14a on the incident surface of the fly-eye lens 16 is considerably large even in the area 16Aa outside the area facing the minimum aperture of the aperture stop 17. getting stronger. Therefore, about 45% of the illumination light 20a emitted from the emission end 14a can pass through the aperture of the aperture stop 17, for example.

Therefore, the illumination efficiency of the illumination light 20a incident on the mask M when the magnification of the variable magnification optical system 8a is increased as shown in FIG. is improved by about 30% (=(60/45−1)·100). In this embodiment, three light sources 2a to 2c are used, but if the illumination efficiency is improved by 30%, for example, it is possible to perform exposure by lighting only two light sources 2a and 2b. Therefore, it is possible to extend the life of the light sources 2a to 2c.

FIG. 6B shows the light intensity distributions D1 and D2 of the illumination light 3a at the incident end 12a of FIGS. represents the distance from the center of the incident end 12a as a relative value. The position where the value of the horizontal axis is 50 is, for example, the position of the edge portion of the incident end 12a. Further, the light intensity distribution D3 in FIG. 6B shows the light intensity of the illumination light passing through the aperture of the aperture stop 17 and the illumination light incident on the fly-eye lens 16 in the case of the comparative example in FIG. 6A. This is a distribution obtained by compressing the light intensity distribution D1 by a ratio. The amount of light obtained by integrating the light intensity distribution D2 inside the position ±50 is the amount of light obtained in this embodiment, and the amount of light obtained by integrating the distribution of light intensity D3 is the amount of light obtained in the comparative example. The results also show that the illumination efficiency is improved by this embodiment.

FIG. 6C shows the light intensity distributions C31 and C11 of the illumination light 20a on the incident surface of the fly-eye lens 16 of FIGS. The abscissa of 6(C) represents the distance from the center of the incident surface in terms of σ value, with the center position of the incident surface being 0. The relative intensities of the light intensity distributions C31 and C11 are adjusted so that the values at σ values of 0.88 and 0.65 are equal. In this case, if the values of the light intensity distributions C31 and C11 at the position where the σ value is 0.5 are taken as the average light intensity or the average illuminance, the average illuminance of the light intensity distributions C31 and C11 are almost equal.

Next, in step 102, if the aperture stop 17 is used to set the σ value to an arbitrary value NA3 between the maximum value NA1 and the minimum value NA2, in step 104, the variable power optical systems 8a to 8c The magnification may be set to a value β3 between the minimum value (β1) in the case of FIG. 5A and the maximum value (β2) in the case of FIG. 5B. As an example, β3 is set gradually larger as the σ value NA3 gradually decreases, and the maximum tilt angle of the illumination light incident on the light guide fiber 10 is set gradually smaller, as expressed by the following equation. .

β3=β1+(NA1−NA3)(β2−β1)/(NA1−NA2) (2)
As a result, the mask M can be illuminated with high illumination efficiency according to the σ value (illumination condition) regardless of the σ value, and the pattern of the mask M can be formed on the plate P with high throughput and high accuracy. can be exposed to

7(A) is an enlarged view showing the partial illumination optical system IL1 of FIG. 5(A), and FIG. 7(B) is an enlarged view of the exit end 14a of the light guide fiber 10 of FIG. 7(A) viewed from the front. FIG. 7(A) shows enlarged lens elements 16a having the same shape as one another and forming part of the fly-eye lens 16. FIG. As shown in FIG. 7B, the exit end 14a is constructed by regularly bundling a large number of optical fiber strands 11. As shown in FIG. In FIG. 7A, the exit end 14a is imaged by the input lens 15 and the lens element 16a on the exit surface of the lens element 16a (the so-called pupil plane on which the aperture stop 17 is arranged). Further, since the incident surface of the lens element 16a is imaged on the illumination area 21a of the mask M by the lens element 16a and the condenser lens 18, the illumination area 21a is the exposure field (area conjugate with the opening of the field stop 22 in FIG. 3). ), the shape of each lens element 16a of the fly-eye lens 16 is determined to be slightly larger than .

The light intensity distribution at the incident end 12a of the light guide fiber 10 is changed by the variable magnification optical system 8a. Here, as an example, light emitted from the optical fiber strand 11, on which light having a light intensity of up to about 10% of the maximum light intensity at the time of large σ illumination is incident, passes through the input lens 15 and the fly-eye lens 16. A light source image formed on the plane on which the aperture stop 17 is arranged is regarded as an effective light source image that contributes to illumination. Further, when the light emitted from all the optical fiber wires 11 at the emission end 14a respectively forms an effective light source image, the light is formed on the emission surface of the lens element 16a of the fly-eye lens 16 in the range where the light is incident. The number n1 of effective light source images to be generated is the same as the number n2 of the optical fiber strands 11 forming the exit end 14a.

Below, the ratio (=n1/n2) of the number n1 of effective light source images formed on the exit surface of the lens element 16a to the number n2 of the optical fiber strands 11 forming the exit end 14a is expressed as The filling factor γ of the illumination light from the optical fiber strand 11 is called. In the present embodiment, as an example, the magnification of the variable-magnification optical system 8a (the maximum tilt angle of the illumination light incident on the incident end 12a) is adjusted so that the filling factor γ is maintained at 1 (100%).
At this time, when annular illumination, large-σ illumination, or small-σ illumination is performed, the exit surface of the lens element 16a of the fly-eye lens 16 located within the aperture of the aperture stop 17 is shown in FIGS. 8B, or as shown in FIG. 8C, the effective light source image 24 is formed with the same maximum density distribution (distribution corresponding to the density distribution of the optical fiber strand 11 in FIG. 7B). be done. In FIG. 8A, the aperture of the aperture stop 17 is set to an annular aperture 17c. When annular illumination or large σ illumination is performed, the maximum tilt angle of the illumination light incident on the incident ends 12a to 12c of the light guide fiber 10 from the variable magnification optical systems 8a to 8c is greater than that in the case of small σ illumination. set large.

Also, for convenience of explanation, in FIGS. 8A to 8C and FIGS. 9A and 9B, which will be described later, each lens element 16a of the fly-eye lens 16 is positioned closer to the apertures 17b and 17c than actually. is also greatly represented.
As described above, in the present embodiment, the filling factor γ of the illumination light from the optical fiber strand 11 when performing the annular illumination, the large σ illumination, or the small σ illumination is in the range of 1 in common. The magnification of system 8a is adjusted. In this case, since the number of effective light source images 14 within the aperture of the aperture stop 17 is maximum, the uniformity of the illuminance distribution on the mask M is excellent. Note that the filling factor γ may be approximately 1 (for example, 0.9 to 1).

However, the light intensity of the illumination light incident on the incident ends 12a to 12c of the light guide fiber 10 is maximum at the central portion and decreases toward the periphery. Therefore, among the many optical fiber wires 11 constituting the incident end 12a, for example, the light intensity of about 70% or more, 70 to 40%, and about 40 to 10% of the maximum value at the time of large σ illumination. The light source images formed by the illumination light from the optical fiber strand 11 into which the illumination light 3a is incident are assumed to be light source images 24A, 24B, and 24C, respectively. At this time, as shown in FIG. 5A, when the σ value is set large, on the exit surface of the fly-eye lens 16, the exit surface of the lens element 16a within the aperture 17b of the aperture stop 17 has a As shown in 9A, light source images 24A, 24B, and 24C are formed in a random arrangement.

Also, the illumination light emitted from the exit end 14a of the light guide fiber 10 is incident on the plurality of lens elements 16a (optical elements) of the fly-eye lens 16. It is distributed over an area larger than the size of the incident surface).
On the other hand, as shown in FIG. 5B, when the σ value is set small, on the exit surface of the fly-eye lens 16, the exit surface of the lens element 16a within the aperture 17b of the aperture stop 17 is , and as shown in FIG. 9B, light source images 24B with approximately medium light intensity are formed in a regular arrangement. Also, the illumination light emitted from the exit end 14a of the light guide fiber 10 is distributed over a region wider than the size of the entrance apertures of the plurality of lens elements 16a of the fly-eye lens 16 within the small aperture 17b. . Therefore, in the small σ illumination, the light intensity of the light source image 24B formed on the exit surface of each lens element 16a of the fly-eye lens 16 is more uniform than in the case of FIG. will be

Further, as in the comparative example, when performing small σ illumination with a numerical aperture NA2, as indicated by the dotted line in FIG. Since most of the illumination light incident on the outside of the opening 17b is blocked from the opening 17b, the utilization efficiency of the illumination light is lowered.

As described above, the illumination device ILA for illuminating the mask M of this embodiment includes the light source 2a that generates illumination light, the variable power optical system 8a that adjusts the maximum tilt angle of the illumination light in step 104, and the In step 106, an input lens 15 (hereinafter also referred to as a first condensing optical system) that converges the illumination light through the variable power optical system 8a into a parallel light flux, and in step 106, the illumination through the variable power optical system 8a A light guide fiber 10 (hereinafter also referred to as an optical member) that emits light to an input lens 15 while maintaining the maximum tilt angle of the illumination light, and a numerical aperture (σ value) of the illumination light in step 102 It is provided with an aperture stop 17 to be adjusted and a condenser lens 18 (hereinafter also referred to as a second condensing optical system) for guiding the illumination light whose numerical aperture is controlled in step 106 to the mask M. FIG.

According to the illumination device ILA of the present embodiment, when performing small σ illumination with a reduced numerical aperture of the illumination light, the variable magnification optical system 8a reduces the maximum tilt angle of the illumination light, thereby reducing the aperture stop 17 It is possible to increase the proportion of the illumination light incident on the opening of the aperture, and to increase the efficiency of using the illumination light. Therefore, the mask M can be illuminated with a higher illuminance. In addition, when illuminating the mask M with the same illuminance, the life of the light source 2a can be extended, and when using a plurality of light sources 2a to 2c, the number of light sources used can be reduced to reduce the size of the illumination device ILA. Cost reduction can be achieved. Moreover, since the light guide fiber 10 is used, the light source 2a and the mask M can be separated, and the thermal expansion of the mask M can be suppressed.

The exposure apparatus EX for exposing the pattern of the mask M onto the plate P according to the present embodiment includes an illumination device ILA that illuminates the mask M in steps 102 to 106, and a mask M illuminated by the illumination device ILA in step 108. and a projection optical system PL that forms an image of the pattern on the plate P. According to the exposure apparatus EX, the efficiency of using the illumination light in the illumination apparatus ILA is high, so by increasing the illuminance of the illumination light, the pattern of the mask M can be exposed onto the plate P with high throughput and high accuracy. Further, if the illuminance of the illumination light is the same as in the conventional case, the size and cost of the illumination device ILA can be reduced, so that the exposure device EX can be further reduced in size and cost.

Further, since the light guide fiber 10 has a plurality of incident ends 12a to 12c and a plurality of exiting ends 14a and 14b, etc., the illumination light from the plurality of light sources 2a to 2c is randomly mixed to obtain a plurality of partial illuminations. It can be easily split into light beams for the optical systems IL1 to IL7.
Moreover, since the fly-eye lens 16 including a plurality of lens elements 16a is provided, the illuminance distribution of the illumination light in the illumination area of the mask M can be made more uniform.

It should be noted that the above-described embodiment can be modified as follows.
As shown in FIG. 10A, the variable magnification optical system 8a of the above-described embodiment has a front lens group system 6A consisting of three lenses and a rear lens group system 7A consisting of three lenses. However, when adjusting the magnification, for example, a variable magnification optical system 8Aa for adjusting the position of the rear lens group 7A can be used.

Further, as the variable magnification optical system 8a, an optical system of a type that forms an intermediate image of the light source image on the optical path between the light source image 5a and the light source image 9a can be used.
In the above-described embodiment, the variable magnification optical system 8a is used to control the maximum tilt angle of the illumination light. Alternatively, a relay optical system 8Ba may be used in which the magnification is switched by partially exchanging the optical system. The relay optical system 8Ba comprises a front lens system 6A, a first rear lens system 7B comprising a lens 7Ba and a lens group 7Bb having two lenses, and a second rear lens system comprising lenses 7Ca and 7Cb. 7C. When the magnification is low, the front lens group system 6A and the first rear lens group system 7B are used to form the light source image 9a. 2 is used to form a light source image 9a. When the exchangeable relay optical system 8Ba is used in this way, the optical system for controlling the tilt angle can be manufactured at low cost.

Also, between the front lens group system 6 and the rear lens group system 7 of the variable power optical system 8a of the above-described embodiment, as disclosed in US Pat. No. 5,719,704, or An optical system (axicon system) consisting of two conical prism-shaped optical members 7B1 and 7B2 may be provided as indicated by the dotted line in FIG. 10(A). At this time, when normal illumination is performed, the two optical members 7B1 and 7B2 are brought into close contact, and when annular illumination is performed, the distance between the two optical members 7B1 and 7B2 is adjusted so that the front group The cross-sectional shape of the illumination light 3a passing between the lens system 6 and the rear lens group 7 may be an annular shape with a variable size. In this case, the illumination light 20a emitted from the exit end 14a of the light guide fiber 10 is incident on the annular area of the incident surface of the fly-eye lens 16 via the input lens 15. FIG. When performing annular illumination, by adjusting the distance between the two optical members 7B1 and 7B2 according to the size of the annular aperture of the aperture stop, the use of illumination light when performing annular illumination Efficiency can be further improved.

Also, in the above-described embodiment, the fly-eye lens 16 is used as the optical integrator, but instead of the fly-eye lens 16, a microlens array, a rod integrator, or the like may be used.
In the above-described embodiment, ultra-high pressure mercury lamps are used as the light sources 2a-2c, but any other lamps such as discharge lamps can be used as the light sources 2a-2c. Light emitting diodes (LEDs) or the like can also be used as the light sources 2a to 2c. Laser light sources such as solid lasers, gas lasers, or semiconductor lasers may be used as the light sources 2a to 2c. It is also possible to use harmonics of laser light or the like as illumination light.

When a laser light source is used as the light source and the maximum tilt angle of the illumination light is set large, as an example, as shown in FIG. On the optical path of the laser beam LB, a diffraction grating 8C is arranged on which concentric circular (zone plate-like) phase-type concavities and convexities with fine pitches gradually decreasing are formed. The minimum pitch of diffraction grating 8C is defined according to the maximum tilt angle.

When a laser light source is used to set the maximum tilt angle of the illumination light to be small, concentric circular phase-type unevenness similar to the diffraction grating 8C is formed on the optical path of the laser beam LB. A diffraction grating 8D having a minimum pitch larger than that of the diffraction grating 8C is arranged. In this modification, when using the diffraction grating 8C, illumination light with a large maximum tilt angle can be generated, and when using the diffraction grating 8D, illumination light with a small maximum tilt angle can be generated. Effects similar to those of the above-described embodiment can be obtained.

In the above-described embodiments, a multi-lens scanning exposure apparatus has been described as an example. , the above-described embodiments can also be applied to a step-and-repeat type exposure apparatus in which the plate P is sequentially stepped. Also, although three light sources are used as the light sources of the lighting device, the lighting device may have one, two, or four or more light sources. Also, in the above-described embodiment, the light guide fiber has seven exit ends, but the number of exit ends of the light guide fiber may be any number as long as it is one or more.

In the above-described embodiment, illumination light from the plurality of light sources 2a to 2c is branched into light fluxes for the plurality of partial illumination optical systems IL1 to IL7. The mask M may be illuminated via the illumination optical system IL1, and the pattern of the mask M may be transferred to the plate P via one imaging optical system (for example, an optical system similar to the partial projection optical system PL1). In this case, the illumination light 3a from the variable-magnification optical system 8a may be directly incident on the fly-eye lens 16 via the input lens 15 without providing the light guide fiber 10. FIG.

Next, a device manufacturing method using the exposure apparatus or exposure method according to the above embodiment will be described. FIG. 11 is a flow chart showing a manufacturing process of a liquid crystal device such as a liquid crystal display element. As shown in FIG. 11, in the liquid crystal device manufacturing process, a pattern forming process (step 200), a color filter forming process (step 202), a cell assembling process (step 204), and a module assembling process (step 206) are sequentially performed. .

In the pattern forming process of step 200, predetermined patterns such as a circuit pattern and an electrode pattern are formed on a glass substrate coated with a photoresist as a plate using the exposure apparatus or the exposure method described above. This pattern formation step includes an exposure step of transferring a pattern to a photoresist layer using the exposure apparatus or exposure method of the above-described embodiment, and a plate onto which the pattern is transferred is developed to form a photolithography having a shape corresponding to the pattern. It includes a developing step of generating a resist layer as a mask layer and a processing step of processing the surface of the glass substrate via the developed photoresist layer.

In the color filter forming process of step 202, a large number of sets of three dots corresponding to R (red), G (green), and B (blue) are arranged in a matrix, or three dots of R, G, and B are arranged. A color filter is formed by arranging a plurality of pairs of stripe filters in the horizontal scanning direction.
In the cell assembly process of step 204, a liquid crystal panel (liquid crystal cell) is assembled using the glass substrate on which the predetermined pattern is formed in step 200 and the color filters formed in step 202. FIG. Specifically, for example, a liquid crystal panel is formed by injecting liquid crystal between a glass substrate and a color filter.

In the module assembly process of step 206, various parts such as an electric circuit and a backlight for performing the display operation of the liquid crystal panel are attached to the liquid crystal panel assembled in step 204. FIG. As described above, in the device manufacturing method of this embodiment, the exposure apparatus EX or the exposure method of the above-described embodiment is used to form a predetermined pattern on a glass substrate, and the glass substrate is exposed through the predetermined pattern. and processing. According to the exposure apparatus EX or the exposure method of the present embodiment, since exposure can be performed with high illumination efficiency, electronic devices can be manufactured with high throughput and high accuracy.

In addition, the exposure apparatus EX or the exposure method of the above-described embodiments can also be applied when manufacturing semiconductor devices. Further, the above-described embodiments are not limited to application to exposure apparatuses for manufacturing semiconductor devices or liquid crystal devices. , micromachines, thin film magnetic heads, and exposure apparatuses for manufacturing various devices such as DNA chips. Furthermore, the above-described embodiments can also be applied to an exposure apparatus for manufacturing masks (photomasks, reticles, etc.) used for manufacturing various devices using a photolithography process.

2a, 2b, 2c... Light source 4a, 4b, 4c... Elliptical mirror 8a to 8c... Variable power optical system 10... Light guide fiber 12a, 12b, 12c... Entrance end 14a, 14b... Exit end 15... Input lens 16 Fly eye lens 17 Aperture diaphragm 18 Condenser lens 30 Control unit 32 Power supply EX Exposure device ILA Illumination device IL1, IL3 Partial illumination optical system PL Projection optical system, PL1 to PL7... Partial projection optical system, M... Mask, P... Plate

Claims (23)

A lighting device that illuminates a mask,
a light source that generates illumination light;
an optical system that adjusts the tilt angle of the illumination light;
a first condensing optical system that condenses the illumination light that has passed through the optical system;
an optical member that emits the illumination light that has passed through the optical system to the first condensing optical system while maintaining the tilt angle of the illumination light;
an aperture stop for adjusting the numerical aperture of the illumination light emitted from the first light collecting optical system;
a second condensing optical system that guides the illumination light with the adjusted numerical aperture to the mask;
with
The first light collecting optical system has an optical element group including a plurality of optical elements that homogenize the illuminance distribution of the illumination light,
the illumination light that has passed through the optical member is distributed over a region wider than the size of the entrance openings of the plurality of optical elements of the first condensing optical system;
The optical member is configured by bundling a plurality of optical fiber strands,
the number of the optical fiber strands constituting the exit end of the optical member and the number of light source images formed at the exit ends of the plurality of optical elements of the optical element group are approximately equal to each other, An illumination device that adjusts the numerical aperture of the illumination light with a diaphragm. 2. The illumination device according to claim 1, wherein said optical system adjusts said tilt angle of said illumination light based on the numerical aperture of said aperture stop. 3. The lighting device according to claim 2, wherein said optical system reduces said tilt angle of said illumination light when reducing the numerical aperture of said aperture stop. 3. The illumination device according to claim 2, wherein the optical system increases the tilt angle of the illumination light when increasing the numerical aperture of the aperture stop or when forming the aperture of the aperture stop into an annular shape. . The illumination device according to any one of claims 1 to 4, wherein the optical system is a variable magnification optical system that forms an image of the light source with variable magnification. 6. The illumination device according to claim 5, wherein said variable power optical system increases the magnification of the image of said light source when said aperture stop reduces the numerical aperture. 6. The illumination system according to claim 5, wherein the variable power optical system reduces the magnification of the image of the light source when the numerical aperture of the aperture stop is increased or the aperture of the aperture stop is shaped like an annular zone. Device. The optical member ishaving multiple incident ends,splitting the illumination light that has passed through the optical system into a plurality of light fluxes while maintaining the tilt angle of the illumination light;
a plurality of sets of the light source and the optical system corresponding to the plurality of incident ends of the optical member;
A plurality of sets of the first condensing optical system, the aperture stop, and the second condensing optical system are provided corresponding to the plurality of light beams branched by the optical member,
The illumination device according to any one of claims 1 to 7, which illuminates a plurality of illumination areas of the mask. The illumination device according to any one of claims 1 to 8 , wherein the illuminance distribution of the image of the light source is a normal distribution. An exposure apparatus for exposing a pattern of a mask onto a substrate,
a lighting device according to any one of claims 1 to 9 ;
a projection optical system that forms an image of the pattern of the mask illuminated by the illumination device on a substrate;
an exposure apparatus. The illumination device illuminates a plurality of illumination regions of the mask,
a plurality of the projection optical systems corresponding to the plurality of illumination areas;
11. The exposure apparatus according to claim 10 , further comprising a stage device that relatively scans the mask and the substrate in a direction intersecting the arrangement direction of the plurality of illumination regions. An illumination method for illuminating a mask,
adjusting the tilt angle of the illumination light generated from the light source;
emitting the illumination light with the adjusted tilt angle through an optical member that maintains the tilt angle of the illumination light;
condensing the emitted illumination light;
adjusting the numerical aperture of the illumination light;
guiding the illumination light with the adjusted numerical aperture to the mask;
including
Condensing the illumination light includes homogenizing the illuminance distribution of the illumination light using an optical element group including a plurality of optical elements;
The illumination light that has passed through the optical member is distributed over a region wider than the size of the entrance openings of the plurality of optical elements,
The optical member is configured by bundling a plurality of optical fiber strands,
In a range in which the number of the optical fiber strands constituting the exit end of the optical member and the number of light source images formed at the exit ends of the plurality of optical elements of the optical element group are approximately equal, the illumination A lighting method that adjusts the numerical aperture of light. 13. The illumination method according to claim 12 , wherein adjusting the tilt angle of the illumination light includes adjusting the tilt angle of the illumination light based on a numerical aperture of the illumination light. 14. The illumination method according to claim 13 , wherein the tilt angle of the illumination light is decreased when the numerical aperture of the illumination light is decreased. Adjusting the numerical aperture of the illumination light includes performing annular illumination using the illumination light,
14. The illumination method according to claim 13 , wherein the numerical aperture of the illumination light is increased, or the inclination angle of the illumination light is increased when annular illumination is performed using the illumination light. 16. The illumination method according to any one of claims 12 to 15 , wherein adjusting the tilt angle of the illumination light includes forming an image of the light source with variable magnification. 17. The illumination method according to claim 16 , wherein the magnification of the image of the light source is increased when the numerical aperture of the illumination light is decreased. Adjusting the numerical aperture of the illumination light includes performing annular illumination using the illumination light,
17. The illumination method according to claim 16 , wherein the numerical aperture of the illumination light is increased, or the magnification of the image of the light source is decreased when annular illumination is performed using the illumination light. adjusting the inclination angles of the illumination lights from the plurality of light sources to enter the plurality of incident ends of the optical member;
splitting the illumination light with the tilt angle adjusted into a plurality of light fluxes using the optical member;When, including
Illuminating a plurality of illumination regions of the mask using the plurality of light beams.12~18The illumination method according to any one of . An exposure method for exposing a pattern of a mask onto a substrate,
Illuminating the mask using the illumination method according to any one of claims 12 to 19 ;
forming an illuminated image of the mask pattern on a substrate;
exposure method, including the illumination method comprising illuminating a plurality of illumination regions of the mask;
forming images of the pattern of the mask in the plurality of illumination areas on the substrate, respectively;
21. The exposure method according to claim 20 , comprising relatively scanning the mask and the substrate in a direction intersecting the arrangement direction of the plurality of illumination regions. forming a predetermined pattern on a substrate using the exposure apparatus according to claim 10 or 11 ;
and processing the substrate through the predetermined pattern. forming a predetermined pattern on a substrate using the exposure method according to claim 20 or 21 ;
and processing the substrate through the predetermined pattern.

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