JP2004247527A - Illumination optical apparatus, aligner, and exposure method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an illumination optical apparatus capable of uniformizing the optical strength distribution in an angular direction of a luminous flux made incident onto planes to be illuminated, by excellently correcting uneven optical strength distribution in a secondary light source formed in an illumination pupil plane. <P>SOLUTION: The illumination optical apparatus for illuminating the planes (M, W) to be illuminated on the basis of the luminous flux from a light source (1) is provided with a correction means (7) that is spaced by a prescribed distance d (mm) from the illumination pupil plane optically in a relation of Fourier transform to the planes to be illuminated, so as to correct the optical strength distribution of the luminous flux formed by the secondary light source or the luminous flux from the secondary light source depending on the optical strength distribution in the secondary light source formed on the illumination pupil plane. The correction means has a correction filter having a prescribed transmissivity distribution. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an illumination optical apparatus, an exposure apparatus, and an exposure method, and more particularly, to an exposure apparatus for manufacturing a micro device such as a semiconductor device, an imaging device, a liquid crystal display device, and a thin-film magnetic head by a lithography process.
[0002]
[Prior art]
In a typical exposure apparatus of this type, a light beam emitted from a light source is passed through a fly-eye lens (or a micro fly-eye lens or the like) as an optical integrator to serve as a substantial surface light source composed of many light sources. Form a secondary light source. The light flux from the secondary light source is restricted via an aperture stop arranged near the rear focal plane of the fly-eye lens, and then enters the condenser lens.
[0003]
The light beam condensed by the condenser lens illuminates the mask on which the predetermined pattern is formed in a superimposed manner. The light transmitted through the mask pattern forms an image on the wafer via the projection optical system. Thus, the mask pattern is projected and exposed (transferred) on the wafer. The pattern formed on the mask is highly integrated, and it is indispensable to obtain a uniform illuminance distribution on the wafer in order to accurately transfer this fine pattern onto the wafer.
[0004]
[Problems to be solved by the invention]
However, unevenness in light intensity distribution occurs in the secondary light source formed on the illumination pupil plane due to, for example, a manufacturing error of an optical member constituting the projection optical system, and as a result, the wafer to be irradiated is In some cases, unevenness in the light intensity distribution in the angular direction of the light beam incident on the light source may occur.
[0005]
In this case, the imaging performance of the projection optical system is deteriorated due to the unevenness of the light intensity distribution in the angular direction of the light beam incident on the wafer, and the line width of the pattern actually formed on the wafer is substantially different from the desired line width. (A phenomenon in which the line width of a pattern to be originally formed to have a predetermined line width actually varies depending on the position), that is, a problem that a line width abnormality occurs.
[0006]
The present invention has been made in view of the above-described problems, and satisfactorily corrects the light intensity distribution unevenness in the secondary light source formed on the illumination pupil plane, so that the angle direction of the light flux incident on the irradiation surface can be improved. It is an object of the present invention to provide an illumination optical device that can make the light intensity distribution uniform. Further, the present invention uses an illumination optical device capable of uniforming the light intensity distribution in the angular direction of a light beam incident on a surface to be illuminated, and performs a good exposure without substantially causing a line width abnormality. An object of the present invention is to provide an exposure apparatus and an exposure method that can be performed.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problems, according to a first embodiment of the present invention, an illumination optical device that illuminates a surface to be irradiated based on a light beam from a light source includes
The light intensity distribution unevenness in the secondary light source formed on the illumination pupil plane, which is arranged at a distance d (mm) from the illumination pupil plane that is optically in a Fourier transform relationship with the illumination target surface. Accordingly, a correction unit for correcting the light intensity distribution of the light beam forming the secondary light source or the light beam from the secondary light source is provided, and the distance d is
0.01 <1 / d <2
An illumination optical device characterized by satisfying the following conditions:
[0008]
According to a preferred aspect of the first aspect, the correction means has a correction filter having a predetermined transmittance distribution. In this case, the correction unit includes a plurality of correction filters having transmittance distributions different from each other, and the plurality of correction filters are switched with respect to an illumination light path according to light intensity distribution unevenness in the secondary light source. Preferably, it is configured to be possible.
[0009]
Alternatively, according to a preferred aspect of the first aspect, the correction unit includes a first correction filter having a first transmittance distribution and a second correction filter having a second transmittance distribution. The first correction filter and the second correction filter are arranged close to each other along the optical axis, and are configured to be rotatable around the optical axis or an axis parallel to the optical axis. In this case, it is preferable that the first correction filter and the second correction filter are configured to be movable along a plane intersecting the optical axis. Further, the correction unit includes a plurality of sets of the first correction filter and the second correction filter, and the plurality of sets of the first correction filter and the second correction filter are configured to control light intensity distribution unevenness in the secondary light source. Is preferably configured to be switchable with respect to the illumination light path in accordance with
[0010]
Alternatively, according to a preferred aspect of the first aspect, the correction unit includes a light blocking member for partially blocking a light beam forming the secondary light source or a peripheral portion of a light beam from the secondary light source. In this case, it is preferable that the light shielding member is movable along a plane intersecting the optical axis and has a predetermined light shielding ratio distribution.
[0011]
According to a preferred aspect of the first embodiment, the optical system further includes an optical integrator arranged in an optical path between the light source and the irradiated surface, wherein the correction unit is configured to detect a position between the optical integrator and the irradiated surface. It is located in the light path. Further, the apparatus further includes an aperture stop arranged on the illumination pupil plane to define the shape or size of the secondary light source, wherein the correction unit is arranged closer to the irradiated surface than the aperture stop. preferable.
[0012]
According to a second aspect of the present invention, an illumination optical device according to the first aspect for illuminating a mask on which a predetermined pattern is formed, and a projection optical system for forming a pattern image of the mask on a photosensitive substrate. An exposure apparatus is provided. In this case, a measuring unit for measuring a light intensity distribution on a pupil plane of the projection optical system, and the plurality of correction filters or the plurality of first correction filters according to a measurement result of the light intensity distribution on the pupil plane It is preferable that the apparatus further comprises switching means for switching the second correction filter.
[0013]
According to a third aspect of the present invention, a mask is illuminated via the illumination optical device of the first aspect, and a pattern formed on the illuminated mask is exposed on a photosensitive substrate via a projection optical system. An exposure method is provided. In this case, a measurement step of measuring a light intensity distribution on the pupil plane of the projection optical system, and the plurality of correction filters or the plurality of sets of the first correction filters and And a switching step of switching the two correction filters.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a view schematically showing a configuration of an exposure apparatus provided with an illumination optical device according to an embodiment of the present invention. In FIG. 1, a Y axis is set along a normal direction of a wafer W as a photosensitive substrate, and an X axis and a Z axis are set along two directions orthogonal to each other in a plane parallel to the wafer W. . In FIG. 1, the illumination optical device is set to perform normal circular illumination.
[0015]
The exposure apparatus of the present embodiment includes a laser light source 1 for supplying exposure light (illumination light). As the laser light source 1, for example, a KrF excimer laser light source that supplies light having a wavelength of 248 nm, an ArF excimer laser light source that supplies light having a wavelength of 193 nm, or the like can be used. A substantially parallel light beam emitted from the laser light source 1 has a rectangular cross section elongated in the X direction, and enters a beam expander 2 including a pair of lenses 2a and 2b. Each of the lenses 2a and 2b has a negative refractive power and a positive refractive power, respectively, in the plane of the paper of FIG. 1 (in the YZ plane). Therefore, the light beam incident on the beam expander 2 is enlarged in the plane of FIG. 1 and shaped into a light beam having a predetermined rectangular cross section.
[0016]
A substantially parallel light beam passing through a beam expander 2 as a shaping optical system enters a zoom lens 4 via a diffractive optical element 3 for circular illumination. An entrance surface of a micro fly's eye lens (or fly's eye lens) 5 is positioned near the rear focal plane of the zoom lens 4. Generally, a diffractive optical element is formed by forming a step having a pitch on the order of the wavelength of exposure light (illumination light) on a substrate, and has a function of diffracting an incident beam to a desired angle. Specifically, the diffractive optical element 3 converts a rectangular parallel light beam incident along the optical axis AX into a divergent light beam having a circular cross section.
[0017]
The diffractive optical element 3 is configured to be insertable into and removable from the illumination optical path, and is configured to be switchable between a diffractive optical element 3a for annular illumination and a diffractive optical element 3b for quadrupole illumination. Here, switching between the diffractive optical element 3 for circular illumination, the diffractive optical element 3a for annular illumination, and the diffractive optical element 3b for quadrupole illumination operates based on a command from the control system 20. This is performed by one drive system 21. The change in the focal length of the zoom lens 4 is performed by the second drive system 22 that operates based on a command from the control system 20.
[0018]
The micro fly's eye lens 5 is an optical element including a large number of micro lenses arranged vertically and horizontally and densely. In general, a micro fly's eye lens is formed by, for example, performing an etching process on a parallel flat plate to form a micro lens group. Here, each micro lens constituting the micro fly's eye lens is smaller than each lens element constituting the fly eye lens. Also, unlike a fly-eye lens composed of lens elements separated from each other, the micro fly-eye lens is formed integrally with a large number of minute lenses without being separated from each other. However, the micro fly's eye lens is a wavefront division type optical integrator similar to the fly's eye lens in that the lens elements are arranged vertically and horizontally.
[0019]
In this way, the light beam having passed through the diffractive optical element 3 forms a circular illumination field centered on the optical axis AX on the incident surface of the micro fly's eye lens 5 via the zoom lens 4. Here, the size (that is, the diameter) of the formed circular illumination field changes depending on the focal length of the zoom lens 4. The light beam incident on the micro fly's eye lens 5 is two-dimensionally divided by a large number of minute lenses, and a light source is formed on the rear focal plane of each minute lens on which the light beam has entered. Thus, on the rear focal plane of the micro fly's eye lens 5, a circular surface light source having substantially the same light intensity distribution as the circular illumination field formed by the light beam incident on the micro fly's eye lens 5 ( Hereinafter, a “secondary light source” is formed.
[0020]
A light beam from a circular secondary light source formed on the rear focal plane of the micro fly's eye lens 5 enters an aperture stop 6 arranged in the vicinity thereof. The aperture stop 6 is disposed on an illumination pupil plane that has an optical Fourier transform relationship with the mask M (and thus the wafer W), and has a function of defining the shape or size of the secondary light source. The light from the secondary light source through the aperture stop 6 having the circular opening (light transmitting portion) is subjected to the condensing action of the condenser optical system 8 via the correction filter 7, and then the light from the mask M (and, consequently, the mask M) The mask blind 9 arranged on a plane optically conjugate with the wafer W) is illuminated in a superimposed manner. The correction filter 7 is selected from a plurality of correction filters 7a having mutually different transmittance distributions and positioned in the illumination light path.
[0021]
Switching of the plurality of correction filters 7a with respect to the illumination light path is performed by a third drive system 23 that operates based on a command from the control system 20. The configuration and operation of the correction filter 7 will be described later. In this way, a rectangular illumination field similar to the shape of each micro lens constituting the micro fly's eye lens 5 is formed on the mask blind 9. The light flux passing through the rectangular opening (light transmitting portion) of the mask blind 9 irradiates the mask M on which a predetermined pattern is formed in a superimposed manner after receiving the light condensing action of the imaging optical system 10.
[0022]
Thus, the imaging optical system 10 forms an image of the rectangular opening of the mask blind 9 on the mask M supported by the mask stage MS. That is, the mask blind 9 constitutes a field stop for defining an illumination area formed on the mask M (therefore, the wafer W). The light flux transmitted through the pattern of the mask M forms an image of the mask pattern on the wafer W as a photosensitive substrate via the projection optical system PL. In this way, in a plane (XZ plane) orthogonal to the optical axis AX of the projection optical system PL, batch exposure or scan exposure is performed while the wafer W supported by the wafer stage WS is two-dimensionally driven and controlled, whereby the wafer is exposed. The pattern of the mask M is sequentially exposed on each exposure region of W.
[0023]
In the collective exposure, a mask pattern is collectively exposed to each exposure region of a wafer according to a so-called step-and-repeat method. In this case, the shape of the illumination area on the mask M is a rectangular shape close to a square, and the cross-sectional shape of each micro lens of the micro fly's eye lens 5 is also a rectangular shape close to a square. On the other hand, in scan exposure, according to a so-called step-and-scan method, a mask pattern is scanned and exposed on each exposure region of a wafer while the mask and wafer are relatively moved with respect to a projection optical system. In this case, the shape of the illumination area on the mask M is a rectangular shape with a ratio of the short side to the long side of, for example, 1: 3, and the cross-sectional shape of each micro lens of the micro fly's eye lens 5 is similar to this. Shape.
[0024]
Note that the exposure apparatus of the present embodiment is provided with a light intensity distribution measuring device 24 as measuring means for measuring the light intensity distribution on the pupil plane of the projection optical system PL. For details regarding the light intensity distribution measuring device 24, for example, WO99 / 36832, JP-A-11-317349, JP-A-2000-19012, JP-A-2002-110540, and the like can be referred to. The light intensity distribution information on the pupil plane of the projection optical system PL measured by the light intensity distribution measuring device 24 is supplied to the control system 20.
[0025]
The annular illumination can be performed by setting the diffractive optical element 3a in the illumination optical path instead of the diffractive optical element 3. The diffractive optical element 3a for annular illumination converts a rectangular parallel light beam incident along the optical axis AX into a divergent light beam having an annular cross section. Therefore, the light beam having passed through the diffractive optical element 3a forms, for example, an annular illumination field around the optical axis AX on the incident surface of the micro fly's eye lens 5. As a result, an annular secondary light source having substantially the same light intensity distribution as the annular illumination field formed on the incident surface is also formed on the rear focal plane of the micro fly's eye lens 5.
[0026]
Further, by setting the diffractive optical element 3b instead of the diffractive optical elements 3 and 3a in the illumination light path, quadrupole illumination can be performed. The quadrupole illumination diffractive optical element 3b converts a rectangular parallel light beam incident along the optical axis AX into a divergent light beam having a quadrupole cross section. Therefore, the light beam having passed through the diffractive optical element 3b forms, for example, a quadrupole illumination field centered on the optical axis AX on the incident surface of the micro fly's eye lens 5. As a result, a quadrupole secondary light source having substantially the same light intensity distribution as the quadrupole illumination field formed on the incident surface is also formed on the rear focal plane of the micro fly's eye lens 5.
[0027]
FIG. 2 is a diagram illustrating a positional relationship between a correction filter arranged in an optical path between the micro fly's eye lens and the condenser optical system in FIG. 1 and an illumination pupil plane. Referring to FIG. 2, a correction filter 7 is provided on an illumination pupil plane optically in a Fourier transform relationship with a mask M (and thus a wafer W) in an optical path between a micro fly's eye lens 5 and a condenser optical system 8. It is arranged in the vicinity of the arranged aperture stop 6.
[0028]
Specifically, the correction filter 7 is arranged at a distance d (mm) from the aperture stop 6 on the mask side (condenser optical system 8 side) of the aperture stop 6. The correction filter 7 is an optical member in the form of a plane-parallel plate made of an optical material such as quartz glass. Then, a correction surface having a predetermined transmittance distribution expressed by the density of the fine dot pattern of, for example, chrome is formed on the light source side (the micro fly's eye lens 5 side) of the correction filter 7.
[0029]
FIG. 3 schematically illustrates a state in which light intensity distribution unevenness including a tilt component occurs on a pupil plane of the projection optical system, and a transmittance distribution formed in a correction filter for correcting the tilt component of the light intensity distribution unevenness. FIG. In FIG. 3A, the vertical axis is the light intensity I, and the horizontal axis is the position coordinate r along the inclination direction of the light intensity distribution with the optical axis AX as the origin on the pupil plane of the projection optical system PL. In FIG. 3B, the vertical axis represents the transmittance T, and the horizontal axis represents the correction surface (the transmittance distribution is formed) of the correction filter 7 optically corresponding to the position coordinate r on the pupil plane of the projection optical system PL. Position coordinates R on the surface on which the image is recorded).
[0030]
As shown in FIG. 3A, a tilt component (defined according to a linear function of the position coordinate r) on the pupil plane of the projection optical system PL due to, for example, a manufacturing error of an optical member constituting the projection optical system PL. May be generated. In this case, even in the secondary light source formed on the illumination pupil plane (the position where the aperture stop is arranged) having an optically conjugate positional relationship with the pupil plane of the projection optical system PL, the pupil plane of the projection optical system PL The same light intensity distribution unevenness as described above occurs.
[0031]
Therefore, in the present embodiment, in order to correct the inclination component of the light intensity distribution unevenness on the pupil plane of the projection optical system PL, a plurality of correction filters 7a having mutually different transmittance distributions are used as shown in FIG. The correction filter 7 having the transmittance distribution T (R) including the various inclination components is selected, and the correction filter 7 is located near the illumination pupil plane which is optically conjugate with the pupil plane of the projection optical system PL (from the illumination pupil plane). (At a position separated by a distance d (mm)).
[0032]
The transmittance distribution T (R) shown in FIG. 3B is represented by the following equation (1).
T (R) = (1-D) / ｛1-D / 2 (1 + R / R _max )｝ (1)
In the equation (1), D is a difference between the maximum transmittance and the minimum transmittance. In the transmittance distribution T (R) shown in FIG. _max , The transmittance T is 1 at the maximum, and R = −R _max At the position of (1), the transmittance T is (1-D) at the minimum. In the present embodiment, a plurality of correction filters having various forms of transmittance distribution are provided without being limited to the correction filters having the tilt components as described with reference to FIG.
[0033]
In the present embodiment, the light intensity distribution on the pupil plane of the projection optical system PL is measured by using the light intensity distribution measuring device 24 as a measuring means while the correction filter 7 is retracted from the illumination optical path as necessary. I do. Then, according to the light intensity distribution unevenness on the pupil plane of the projection optical system PL (that is, the light intensity in the secondary light source formed on the illumination pupil plane which is optically conjugate with the pupil plane of the projection optical system PL) Using the control system 20 and the third drive system 23 as filter switching means, the correction filter 7 having a required transmittance distribution is changed from the plurality of correction filters 7a having different transmittance distributions. Select and position in the illumination light path.
[0034]
As described above, in the present embodiment, the vicinity of the illumination pupil plane which has an optically conjugated positional relationship with the pupil plane of the projection optical system PL (and has an optical Fourier transform relation with the mask M (and thus the wafer W)). The light intensity distribution of the light flux from the secondary light source is corrected by the action of the correction filter 7 having a required transmittance distribution and thus, the light intensity distribution unevenness on the pupil plane of the projection optical system PL is favorably corrected. In addition, the light intensity distribution in the angular direction of the light beam incident on the wafer W can be made uniform. As a result, in the present embodiment, it is possible to perform good exposure without substantially causing a line width abnormality, and to manufacture a good micro device.
[0035]
In the present embodiment, the distance d (mm) between the correction filter 7 and the aperture stop 6 (illumination pupil plane) satisfies the following conditional expression (2).
0.01 <1 / d <2 (2)
If the lower limit of conditional expression (2) is not reached, the correction filter 7 is too far from the illumination pupil plane, and a desired light intensity distribution to be formed on the pupil plane of the projection optical system PL by the action of the correction filter 7 is realized. Becomes difficult. On the other hand, when the value exceeds the upper limit value of the conditional expression (2), the correction filter 7 is too close to the illumination pupil plane, and correction is performed due to the effect of energy concentration in a large number of point light sources (secondary light sources) formed on the illumination pupil plane. The glass substrate or coat of the filter 7 is easily damaged.
[0036]
In the above-described embodiment, the correction surface having the predetermined transmittance distribution is formed on the light source side of the correction filter 7. However, the present invention is not limited to this, and the correction surface may be formed on the mask side of the correction filter 7. You can also. Further, the correction filter 7 is disposed on the mask side of the aperture stop 6. However, unless the correction filter 7 has a substantial adverse effect on the imaging performance of the micro fly's eye lens 5, the diffraction of the dot pattern is also prevented. As long as the phenomenon does not have a substantial adverse effect, the correction filter 7 can be arranged closer to the light source than the aperture stop 6. In this case, by the operation of the correction filter 7, the light intensity distribution of the light beam forming the secondary light source is corrected, and the light intensity distribution unevenness on the pupil plane of the projection optical system PL is favorably corrected.
[0037]
In the above-described embodiment, the light intensity distribution (shape and size of the secondary light source) on the illumination pupil plane (the rear focal plane of the micro fly's eye lens 5) which has an optical Fourier transform relationship with the mask M is described. The illumination condition is switched by changing the illumination condition. It is conceivable that unevenness of the light intensity distribution occurs on the pupil plane of the projection optical system PL according to the switching of the illumination condition. In this case, the plurality of correction filters 7a can be switched with respect to the illumination light path in accordance with switching of illumination conditions.
[0038]
Further, in the above-described embodiment, the plurality of correction filters 7a are switched with respect to the illumination optical path in accordance with the uneven light intensity distribution on the pupil plane of the projection optical system PL. Has a predetermined transmittance distribution when does not substantially change over time, or when the light intensity distribution on the pupil plane of the projection optical system PL does not substantially change due to switching of the illumination condition. The correction filter 7 can be fixedly positioned in the illumination light path.
[0039]
In the above-described embodiment, the correction filter 7 is arranged near the aperture stop 6, but the correction filter 7 has a substantial adverse effect on the optical conjugate relationship between the mask blind 9 and the mask M. The correction filter 7 is optically Fourier-transformed with the mask M (and, consequently, the wafer W) in the optical path of the imaging optical system 10 unless the diffraction phenomenon of the dot pattern has a substantial adverse effect. It can also be located near the position.
[0040]
By the way, in the above-described embodiment, the correction filter 7 is arranged alone near the illumination pupil plane, but the first correction filter having the first transmittance distribution and the second correction filter having the second transmittance distribution are provided. A modification in which the correction filter and the correction filter are arranged near the illumination pupil plane in a state of being close to each other along the optical axis is also possible. In the first modification using a pair of correction filters, the first correction filter and the second correction filter are configured to be rotatable around the optical axis (or an axis parallel to the optical axis).
[0041]
FIG. 4 is a first diagram schematically illustrating the operation of a pair of correction filters used in the first modification. FIG. 5 is a second diagram schematically illustrating the operation of the pair of correction filters used in the first modification. 4 and 5, a region a is a region where the transmittance changes in a range of 0.98 to 1, a region b is a region where a transmittance changes in a range of 0.96 to 0.98, and a region c is a transmittance. Is a region where the transmittance changes in a range of 0.94 to 0.96, a region d is a region where the transmittance changes in a range of 0.92 to 0.94, and a region e is a range where the transmittance is 0.90 to 0.92. Is the area that changes.
[0042]
Further, a region f is a region where the transmittance changes in a range from 0.88 to 0.90, a region g is a region where the transmittance changes in a range from 0.86 to 0.88, and a region h is a region where the transmittance is 0. A region where the transmittance changes in a range from 84 to 0.86, a region i is a region where the transmittance changes in a range from 0.82 to 0.84, and a region j changes in a range where the transmittance is from 0.80 to 0.82. Area. In the examples shown in FIGS. 4 and 5, both the first correction filter and the second correction filter have a distribution in which the transmittance changes from 0.9 to 1 in one direction.
[0043]
Specifically, FIG. 4A shows a composite transmittance distribution obtained when the first correction filter and the second correction filter are arranged in the same manner so that the direction of change in transmittance is horizontal in the figure. . In the state shown in FIG. 4A, a composite transmittance distribution in which the transmittance changes along the horizontal direction from 0.8 to 1 is obtained. FIG. 4B shows a composite transmittance distribution obtained when the first correction filter is rotated 65 degrees counterclockwise and the second correction filter is rotated 65 degrees clockwise from the state of FIG. 4A. Is shown. In the state shown in FIG. 4B, a composite transmittance distribution in which the transmittance changes along the horizontal direction from about 0.86 to about 0.96 is obtained.
[0044]
FIG. 4C shows a composite transmittance distribution obtained when the first correction filter is rotated by 80 degrees counterclockwise and the second correction filter is rotated by 80 degrees clockwise from the state of FIG. 4A. Is shown. In the state shown in FIG. 4C, a composite transmittance distribution in which the transmittance changes along the horizontal direction from about 0.88 to about 0.92 is obtained. FIG. 5A shows a composite transmittance distribution obtained when the first correction filter is rotated 90 degrees counterclockwise and the second correction filter is rotated 90 degrees clockwise from the state of FIG. 4A. Is shown. In the state shown in FIG. 5A, a uniform composite transmittance distribution having a transmittance of about 0.9 is obtained.
[0045]
FIG. 5B shows a case where the first correction filter is rotated 110 (65 + 45) degrees counterclockwise and the second correction filter is rotated 20 (−65 + 45) degrees clockwise from the state of FIG. 4A. 2 shows the obtained composite transmittance distribution. In other words, FIG. 5B shows a composite transmittance distribution obtained when the first correction filter and the second correction filter are integrally rotated counterclockwise by 45 degrees from the state of FIG. 4B. Is shown. In the state shown in FIG. 5B, a combined transmittance distribution obtained by rotating the combined transmittance distribution shown in FIG. 4B counterclockwise by 45 degrees is obtained.
[0046]
As described above, in the first modification, it is possible to obtain a composite transmittance distribution that changes over various ranges by relatively rotating the pair of correction filters. In addition, by integrally rotating the pair of correction filters, it is possible to obtain a composite transmittance distribution that changes along various directions. Furthermore, if necessary, the pair of correction filters are moved relatively or integrally along a direction intersecting the optical axis (typically, a direction orthogonal to the optical axis), so that variously changing synthesis filters can be obtained. A transmittance distribution can be obtained.
[0047]
In the above description with reference to FIGS. 4 and 5, a pair of correction filters having a transmittance distribution in which the transmittance linearly changes in one direction is used. By using a pair of correction filters having a distribution or a pair of correction filters having arbitrary transmittance distributions different from each other, it is possible to obtain a composite transmittance distribution that changes according to various forms. Also, a plurality of sets of the first correction filter and the second correction filter are provided, and the plurality of sets of the first correction filter and the second correction filter are switched with respect to the illumination optical path (the plurality of sets of the first correction filter and the set of the first correction filter are changed from the plurality of sets. By selecting the second correction filter and positioning it in the illumination light path), it is possible to obtain a more variously changing composite transmittance distribution.
[0048]
In the above-described embodiment and the first modification, the correction filter 7 is arranged near the illumination pupil plane. However, the light beam forming the secondary light source or the peripheral portion of the light beam from the secondary light source is partially removed. A second modification in which a light blocking member for blocking light is arranged near the illumination pupil plane is also possible. FIG. 6 is a diagram schematically illustrating a main configuration of a light shielding member used in the second modification. As shown in FIG. 6, a light shielding member 70 used in the second modification includes a pair of blade members 70a and 70b movable in a horizontal direction in the figure and a pair of blade members 70a and 70b movable in a vertical direction in the figure. The blade members 70c and 70d are provided.
[0049]
Here, each blade member is formed by forming a light-shielding thin film such as aluminum or chrome on a quartz glass substrate, for example. Alternatively, each blade member is formed by, for example, forming a predetermined light-shielding rate distribution represented by the density of fine dot patterns such as chrome on a quartz glass substrate. As described above, by partially shielding the peripheral portion of the light beam forming the secondary light source or the light beam from the secondary light source by using the light shielding member 70, the projection optical system PL is used similarly to the case where the correction filter is used. Light intensity distribution unevenness on the pupil plane can be corrected. Note that the light shielding member of the second modification can be used together with the correction filter of the above-described embodiment or the pair of correction filters of the first modification.
[0050]
In the exposure apparatus according to the above-described embodiment, a mask (reticle) is illuminated by an illumination optical device (illumination step), and a transfer pattern formed on the mask is exposed onto a photosensitive substrate using a projection optical system (exposure). Through the steps, a micro device (semiconductor element, imaging element, liquid crystal display element, thin film magnetic head, etc.) can be manufactured. Hereinafter, an example of a method for obtaining a semiconductor device as a micro device by forming a predetermined circuit pattern on a wafer or the like as a photosensitive substrate using the exposure apparatus of the above-described embodiment will be described with reference to the flowchart of FIG. Will be explained.
[0051]
First, in step 301 of FIG. 7, a metal film is deposited on one lot of wafers. In the next step 302, a photoresist is applied on the metal film on the l lot of wafers. Thereafter, in step 303, using the exposure apparatus of the above-described embodiment, an image of the pattern on the mask is sequentially exposed and transferred to each shot area on the wafer of the lot through the projection optical system. After that, in step 304, the photoresist on the one lot of wafers is developed, and in step 305, the resist on the one lot of wafers is etched using the resist pattern as a mask to form a pattern on the mask. A corresponding circuit pattern is formed in each shot area on each wafer. Thereafter, a device such as a semiconductor element is manufactured by forming a circuit pattern of an upper layer and the like. According to the above-described semiconductor device manufacturing method, a semiconductor device having an extremely fine circuit pattern can be obtained with high throughput.
[0052]
In the exposure apparatus of the above-described embodiment, a liquid crystal display element as a micro device can be obtained by forming a predetermined pattern (a circuit pattern, an electrode pattern, etc.) on a plate (glass substrate). Hereinafter, an example of the technique at this time will be described with reference to the flowchart in FIG. 8, in a pattern forming step 401, a so-called photolithography step of transferring and exposing a mask pattern onto a photosensitive substrate (eg, a glass substrate coated with a resist) using the exposure apparatus of the above-described embodiment is performed. . By this photolithography process, a predetermined pattern including a large number of electrodes and the like is formed on the photosensitive substrate. Thereafter, the exposed substrate undergoes each of a developing process, an etching process, a resist stripping process, and the like, whereby a predetermined pattern is formed on the substrate, and the process proceeds to the next color filter forming process 402.
[0053]
Next, in the color filter forming step 402, a large number of sets of three dots corresponding to R (Red), G (Green), and B (Blue) are arranged in a matrix, or three sets of R, G, B Are formed in a horizontal scanning line direction to form a color filter. Then, after the color filter forming step 402, a cell assembling step 403 is performed. In the cell assembly step 403, a liquid crystal panel (liquid crystal cell) is assembled using the substrate having the predetermined pattern obtained in the pattern formation step 401, the color filter obtained in the color filter formation step 402, and the like. In the cell assembling step 403, for example, a liquid crystal is injected between the substrate having the predetermined pattern obtained in the pattern forming step 401 and the color filter obtained in the color filter forming step 402, and a liquid crystal panel (liquid crystal cell) is formed. ) To manufacture.
[0054]
Thereafter, in a module assembling step 404, components such as an electric circuit and a backlight for performing a display operation of the assembled liquid crystal panel (liquid crystal cell) are attached to complete a liquid crystal display element. According to the above-described method for manufacturing a liquid crystal display device, a liquid crystal display device having an extremely fine circuit pattern can be obtained with high throughput.
[0055]
In the above-described embodiment, KrF excimer laser light (wavelength: 248 nm) or ArF excimer laser light (wavelength: 193 nm) is used as the exposure light. For example, F that supplies a laser beam having a wavelength of 157 nm ₂ The present invention can also be applied to a laser light source or a light source other than the laser light source, for example, a lamp light source that supplies ultraviolet light such as i-line, g-line, and h-line.
[0056]
Further, in the above-described embodiment, the present invention is applied to the illumination optical device having the specific configuration as shown in FIG. 1, but various modifications are possible for the specific configuration of the illumination optical device. It is. For example, an optical system from the diffractive optical element 3 as the first integrator to the micro fly's eye lens 5 as the second integrator in the above embodiment is disclosed in JP-A-2001-85293 and JP-A-2002-231719. The present invention can also be applied to an illumination optical device obtained by replacing the optical system of the corresponding part.
[0057]
Further, in the above-described embodiment, the present invention has been described by taking as an example a projection exposure apparatus provided with an illumination optical device. However, the present invention is applied to a general illumination optical device for illuminating an irradiated surface other than a mask. Obviously you can.
[0058]
【The invention's effect】
As described above, in the illumination optical device of the present invention, for example, by the action of a correction filter having a required transmittance distribution that is arranged near an illumination pupil plane that is optically Fourier-transformed to the surface to be illuminated, It corrects the light intensity distribution of the light beam forming the secondary light source or the light beam from the secondary light source, and thus satisfactorily corrects the light intensity distribution unevenness in the secondary light source formed on the illumination pupil plane, and enters the irradiated surface. The light intensity distribution in the angular direction of the luminous flux can be made uniform. Therefore, according to the exposure apparatus and the exposure method using the illumination optical device of the present invention, it is possible to perform a good exposure without substantially causing a line width abnormality, and to manufacture a good micro device.
[Brief description of the drawings]
FIG. 1 is a view schematically showing a configuration of an exposure apparatus including an illumination optical device according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a positional relationship between a correction filter disposed in an optical path between a micro fly's eye lens and a condenser optical system in FIG. 1 and an illumination pupil plane.
FIG. 3 schematically illustrates a state in which light intensity distribution unevenness including a tilt component occurs on a pupil plane of a projection optical system, and a transmittance distribution formed in a correction filter for correcting the tilt component of the light intensity distribution unevenness. FIG.
FIG. 4 is a first diagram schematically illustrating the operation of a pair of correction filters used in a first modification.
FIG. 5 is a second diagram schematically illustrating the operation of a pair of correction filters used in the first modification.
FIG. 6 is a view schematically showing a main configuration of a light shielding member used in a second modification.
FIG. 7 is a flowchart of a method for obtaining a semiconductor device as a micro device.
FIG. 8 is a flowchart of a method for obtaining a liquid crystal display element as a micro device.
[Explanation of symbols]
1 Laser light source
3 Diffractive optical element
4 Zoom lens
5 Micro fly-eye lens
7 Correction filter
8 Condenser optical system
9 Mask blinds
10. Imaging optical system
20 Control system
21-23 drive system
24 Light intensity distribution measuring device
70 Light shielding member
M mask
MS mask stage
PL projection optical system
W wafer
WS wafer stage

Claims (14)

In an illumination optical device that illuminates a surface to be irradiated based on a light beam from a light source,
The light intensity distribution unevenness in the secondary light source formed on the illumination pupil plane, which is arranged at a distance d (mm) from the illumination pupil plane that is optically in a Fourier transform relationship with the illumination target surface. Accordingly, a correction unit for correcting the light intensity distribution of the light beam forming the secondary light source or the light beam from the secondary light source is provided, and the distance d is
0.01 <1 / d <2
An illumination optical device characterized by satisfying the following conditions: The illumination optical device according to claim 1, wherein the correction unit includes a correction filter having a predetermined transmittance distribution. The correction unit has a plurality of correction filters having different transmittance distribution from each other,
The illumination optical device according to claim 2, wherein the plurality of correction filters are configured to be switchable with respect to an illumination optical path according to light intensity distribution unevenness in the secondary light source. The correction means has a first correction filter having a first transmittance distribution and a second correction filter having a second transmittance distribution, and the first correction filter and the second correction filter are optically coupled. The illumination optical device according to claim 1, wherein the illumination optical device is arranged close to each other along an axis, and is rotatable around the optical axis or an axis parallel to the optical axis. The illumination optical device according to claim 4, wherein the first correction filter and the second correction filter are configured to be movable along a plane that intersects the optical axis. The correction unit has a plurality of sets of the first correction filter and the second correction filter,
6. The plurality of sets of the first correction filter and the second correction filter are configured to be switchable with respect to an illumination optical path according to light intensity distribution unevenness in the secondary light source. 7. 3. The illumination optical device according to claim 1. 2. The illumination optical device according to claim 1, wherein the correction unit includes a light blocking member for partially blocking a light beam forming the secondary light source or a peripheral portion of a light beam from the secondary light source. 3. . The illumination optical device according to claim 7, wherein the light shielding member is movable along a plane intersecting an optical axis and has a predetermined light shielding ratio distribution. Further comprising an optical integrator arranged in the optical path between the light source and the irradiated surface,
The illumination optical device according to claim 1, wherein the correction unit is disposed in an optical path between the optical integrator and the surface to be illuminated. Further comprising an aperture stop arranged on the illumination pupil plane to define the shape or size of the secondary light source,
The illumination optical device according to claim 1, wherein the correction unit is disposed closer to a surface to be illuminated than the aperture stop. An illumination optical device according to any one of claims 1 to 10 for illuminating a mask on which a predetermined pattern is formed, and a projection optical system for forming a pattern image of the mask on a photosensitive substrate. An exposure apparatus comprising: A measuring unit for measuring a light intensity distribution on a pupil plane of the projection optical system; The exposure apparatus according to claim 11, further comprising a switching unit for switching a correction filter. A mask is illuminated via the illumination optical device according to any one of claims 1 to 10, and a pattern formed on the illuminated mask is exposed on a photosensitive substrate via a projection optical system. Characteristic exposure method. A measurement step of measuring a light intensity distribution on a pupil plane of the projection optical system; 14. The exposure method according to claim 13, further comprising: a switching step of switching.

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