Patent Application
20120015306
The present invention relates to an illumination optical system, an exposure apparatus provided with the illumination optical system, and a device manufacturing method using the exposure apparatus.
In general, an exposure apparatus for manufacturing microdevices such as semiconductor integrated circuits is provided with an illumination optical system for guiding exposure light emitted from a light source, to a mask such as a reticle on which a predetermined pattern is formed. The illumination optical system is provided with a fly's eye lens as an optical integrator. When the exposure light is incident into the fly's eye lens, a predetermined light intensity distribution is formed on an illumination pupil plane which is optically in a Fourier transform relation with an illumination target surface of a mask on the exit plane side of the fly's eye lens (the predetermined light intensity distribution will be referred to hereinafter as “pupil intensity distribution”). The illumination pupil plane on which the pupil intensity distribution is formed is also referred to as a secondary light source consisting of a large number of illuminants.
The exposure light emitted from the secondary light source is condensed by a condenser lens and thereafter illuminates the mask in a superimposed manner. Then the exposure light passing through the mask travels through a projection optical system to illuminate a region on a substrate such as a wafer coated with a photosensitive material. As a result, the pattern of the mask is projected for exposure (or transferred) onto the substrate.
Incidentally, integration (micronization) of the pattern formed on the mask has been becoming higher and higher in recent years. For accurately transferring the microscopic pattern of the mask onto the substrate, it is essential to form an illumination region with a uniform illuminance distribution (which will also be referred to as “still exposure region”) on the substrate. A conventional technology for accurately transferring the microscopic pattern of the mask onto the substrate was to form the pupil intensity distribution, for example, of an annular shape or a multi-polar shape (dipolar, quadrupolar, or other shape) on the illumination pupil plane so as to improve the depth of focus and the resolving power of the projection optical system (cf. Patent Document 1).
[Patent Document] U.S. Patent Application Laid-Open No. 2006/0055834
Incidentally, for accurately transferring the microscopic pattern of the mask onto the substrate, it is necessary not only to adjust the pupil intensity distribution on the illumination pupil plane into a desired shape but also to adjust light intensities at respective points on the substrate as a final illumination target surface to almost uniform ones. If there is variation among the light intensities at the respective points on the substrate, the line width of the pattern will vary depending upon positions on the substrate, which has raised a risk of failure in accurately transferring the microscopic pattern of the mask in a desired line width across the entire exposure region on the substrate.
The present invention has been accomplished in view of the above-described circumstances and it is an object of the present invention to provide an illumination optical system, an exposure apparatus, and a device manufacturing method allowing adjustment of the light intensity distribution on the illumination target surface.
For solving the above-described problem, the present invention employs the following configuration in correspondence to
An illumination optical system according to the present invention is summarized as an illumination optical system (13) for illuminating an illumination target surface (Ra, Wa) with light (EL) from a light source (12), which comprises: an optical integrator (26) which forms a predetermined light intensity distribution on an illumination pupil plane (27) in an illumination optical path of the illumination optical system (13) with incidence of the light (EL) from the light source (12) thereinto; a transmission filter (64, 81, 82, 81A, 82A) arranged on the illumination target surface (Ra, Wa) side with respect to the optical integrator (26) and in at least one region out of a first adjustment region (63) set including the illumination pupil plane (27) in an optical-axis direction of the illumination optical system (13) and a second adjustment region (80) set including a pupil. conjugate plane (83) optically conjugate with the illumination pupil plane (27), and having a transmittance characteristic varying according to positions of the light (EL) incident thereinto; and a movement mechanism (70) which moves the transmission filter (64, 81, 82, 81A, 82A) along the optical-axis direction in the at least one region.
In the above configuration, the transmission filter (64, 81, 82, 81A, 82A) is formed with the transmittance characteristic varying according to positions of incidence of the light (EL). The transmission filter (64, 81, 82, 81A, 82A) with this characteristic is arranged in at least one region out of the first adjustment region and the second adjustment region. Then the transmission filter (64, 81, 82, 81A, 82A) is moved along the optical-axis direction of the illumination optical system (13), whereby light intensity distributions at respective points on the illumination target surface (Ra, Wa) (also referred to as “pupil intensity distributions”) are independently adjusted. For this reason, it becomes feasible to adjust the light intensity distributions at respective points on the illumination target surface (Ra, Wa) to distributions with properties substantially identical to each other.
For describing the present invention in an easily understood manner, the illumination optical system according to the present invention was described above in correspondence to reference signs in the drawings showing embodiments, but it is needless to mention that the present invention is not limited only to the embodiments.
The present invention allows adjustment of the light intensity distribution on the illumination target surface.
The first embodiment as a specific example of the present invention will be described below on the basis of
As shown in
The illumination optical system 13 is provided with a shaping optical system 17 for converting the exposure light EL emitted from the light source device 12, into a parallel beam of a predetermined sectional shape (e.g., a nearly rectangular cross section), and a first reflecting mirror 18 which reflects the exposure light EL emitted from the shaping optical system 17, to the reticle R side (the +Y-directional side and the right side in
The illumination optical system 13 is provided with an afocal optical system 20 into which the exposure light EL emitted from the diffraction optical element 19 is incident (which is also called “afocal optic”). This afocal optical system 20 has a first lens unit 21 (only one lens of which is illustrated in
In the optical path between the first lens unit 21 and the second lens unit 22, a correction filter 24 having a transmittance distribution of different transmittances according to positions of incidence of the exposure light EL is provided at or near a position optically conjugate with an illumination pupil plane 27 of a below-described optical integrator 26. This correction filter 24 is a filter obtained by forming a pattern of light-blocking dots comprised of chromium or chromium oxide on a glass substrate having an entrance plane and an exit plane parallel to each other.
A zoom optical system 25 for varying the σ value (σ value=numerical aperture on the reticle R side of the illumination optical system 13/numerical aperture on the reticle R side of the projection optical system 15) is provided on the reticle R side of the afocal optical system 20 and the zoom optical system 25 is arranged on the exit side with respect to the predetermined plane 23. The exposure light EL to be emitted from the zoom optical system 25 is converted into a parallel beam by the zoom optical system 25 and thereafter the parallel beam is incident into the optical integrator 26 arranged on the exit side of the zoom optical system 25. Then the optical integrator 26 divides the wavefront of the incident exposure light EL into a plurality of beams and forms a predetermined light intensity distribution (also referred to as “pupil intensity distribution”) on the illumination pupil plane 27 located on the exit side (+Y-directional side) thereof. The illumination pupil plane 27 on which the pupil intensity distribution is formed is also referred to as a secondary light source 60 consisting of a large number of surface illuminants (cf.
The optical integrator 26 is arranged in such a manner that an entrance plane thereof (a plane on the −Y-directional side and the left plane in
On the exit side of the optical integrator 26, there is an unshown illumination aperture stop, which is arranged at a position substantially optically conjugate with an entrance pupil plane of the projection optical system 15 and which is provided for defining a range of contribution of the secondary light source 60 to illumination. This illumination aperture stop has a plurality of aperture portions of different sizes and shapes. In the illumination aperture stop, an aperture portion corresponding to the cross-sectional shape of the exposure light EL emitted from the secondary light source 60 is located in the optical path of the exposure light EL. Specifically, in a case where the cross-sectional shape of the exposure light EL emitted from the secondary light source 60 is annular, the illumination aperture stop is driven so as to locate the aperture portion of the shape corresponding to the annular shape in the optical path of the exposure light EL. In a case where the cross-sectional shape of the exposure light EL emitted from the secondary light source 60 is quadrupolar, the illumination aperture stop is driven so as to locate the aperture portion of the shape corresponding to the quadrupolar shape in the optical path of the exposure light EL.
On the exit side of the optical integrator 26 and the illumination aperture stop, there is a distribution correction optical system 31 provided for correcting light intensity distributions at respective points in an illumination region ER1 (cf.
On the exit side of the distribution correction optical system 31, there are a first condenser optical system 28 composed of at least one lens (only one lens of which is illustrated in
A second condenser optical system 30 composed of a lens having a power is provided on the exit side of the reticle blind 29, and the second condenser optical system 30 converts the light incident from the reticle blind 29 side into a nearly parallel beam. On the exit side of the second condenser optical system 30, there is an imaging optical system 32 provided. This imaging optical system 32 is provided with an entrance-side lens unit 33, a second reflecting mirror 34 which reflects the exposure light EL emitted from the entrance-side lens unit 33, to the −Z-directional side (the lower side in
The reticle stage 14 is arranged, as shown in
A pupil intensity distribution measuring device 36 is provided near the reticle stage 14. This pupil intensity distribution measuring device 36 is a device that measures a pupil intensity distribution formed by incident beams entering a point in the illumination region ER1 on the reticle R, in the secondary light source 60, for each point (or for each position). The pupil intensity distribution measuring device 36 is provided with a beam splitter 37 for reflecting part of the exposure light EL (the part will also be referred to as “reflected light”) emitted from the exit-side lens unit 35 toward the reticle R, a measurement lens 38 into which the reflected light from the beam splitter 37 is incident, and a detection unit 39 into which the reflected light from the measurement lens 38 is incident. This detection unit 39 has a CCD imaging device, a photodiode, or the like and the detection unit 39 outputs a detection signal according to the incident reflected light to a control unit 40. The control unit 40 derives the pupil intensity distribution for each point in the illumination region ER1, based on the detection signal from the detection unit 39. The pupil intensity distribution measuring device 36 is disclosed, for example, in Japanese Patent Application Laid-Open No. 2006-54328 and in Japanese Patent Application Laid-Open No. 2003-22967 and U.S. Patent Application Laid-Open No. 2003/0038225 corresponding thereto.
The projection optical system 15 is provided with a lens barrel 41 filled inside with an inert gas such as nitrogen and a plurality of lenses not shown are provided along the optical path (Z-axis direction) of the exposure light EL in the lens barrel 41. In the lens barrel 41, an aperture stop 42 is arranged at a position in an optical Fourier transform relation with the installation position of the surface Wa of the wafer W and the installation position of the illumination target surface Ra of the reticle R. Then an image of the circuit pattern on the reticle R illuminated with the exposure light EL is projected and transferred to the wafer W on the wafer stage 16, as demagnified at a predetermined reduction ratio through the projection optical system 15. The optical path herein refers to a passage in which the exposure light EL is intended to pass in an operating state.
The wafer stage 16 is provided with a planar mounting surface 43 approximately perpendicular to the optical axis of the projection optical system 15 and the wafer W is mounted on the mounting surface 43. In addition, the wafer stage 16 is provided with an unillustrated wafer stage driving unit for moving the wafer W held thereon, in a predetermined stroke in the X-axis direction. Furthermore, the wafer stage 16 is provided with a mechanism for finely adjusting the position of the wafer W so that the surface Wa of the wafer W becomes perpendicular to the optical axis of the projection optical system 15.
When the image of the pattern is projected onto the wafer W, using the exposure apparatus 11 of the present embodiment, the reticle R is driven by the aforementioned reticle stage driving unit so as to move in the predetermined stroke from the +X-directional side to the −X-directional side (from the near side to the far side with respect to the plane of
The optical integrator 26 in the present embodiment will be described below on the basis of
As shown in
Entrance surfaces 50a, 51a approximately perpendicular to the optical axis AX of the illumination optical system 13 are formed on the entrance side of the first micro fly's eye lens 50 located on the entrance side and on the entrance side of the second micro fly's eye lens 51 located on the exit side, respectively. Furthermore, exit surfaces 50b, 51b approximately perpendicular to the optical axis AX of the illumination optical system 13 are formed on the exit side of the first micro fly's eye lens 50 and on the exit side of the second micro fly's eye lens 51, respectively. A plurality of (ten in
A plurality of (ten in
When attention is focused on the refracting action in the X-axis direction of the optical integrator 26, the exposure light EL (i.e., the parallel beam) incident along the optical axis AX of the illumination optical system 13 undergoes wavefront division at intervals of the first width H1 along the X-axis direction by the respective cylindrical lens faces 52 formed in the entrance surface 50a of the first micro fly's eye lens 50. Then beams resulting from the wavefront division by the respective cylindrical lens faces 52 are subjected to focusing action by individually corresponding cylindrical lens faces out of the cylindrical lens faces 53 formed in the entrance surface 51a of the second micro fly's eye lens 51 and thereafter are focused each on the illumination pupil plane 27 located on the exit side of the optical integrator 26. When attention is focused on the refracting action in the Z-axis direction of the optical integrator 26, the exposure light EL (i.e., the parallel beam) incident along the optical axis AX of the illumination optical system 13 undergoes wavefront division at intervals of the second width H2 along the X-axis direction by the respective cylindrical lens faces 54 formed in the exit surface 50b of the first micro fly's eye lens 50. Then beams resulting from the wavefront division by the respective cylindrical lens faces 54 are subjected to focusing action by individually corresponding cylindrical lens faces out of the cylindrical lens faces 55 formed in the exit surface 51b of the second micro fly's eye lens 51 and thereafter are focused each on the illumination pupil plane 27 located on the exit side of the optical integrator 26. From a large number of point light sources (not shown) formed on the illumination pupil plane 27, beams of exposure light EL are emitted with a divergence angle corresponding to the Z-axis direction larger than that corresponding to the X-axis direction because of the magnitudes of the widths H1, H2 of the cylindrical lens faces 52-55 and the arrangement positions of the cylindrical lens faces 52-55 in the Y-axis direction. Namely, the beams of exposure light EL emitted from the illumination pupil plane 27 have the spread along the Z-axis direction larger than the spread along the X-axis direction.
The first width H1 and the second width H2 of the cylindrical lens faces 52-55 of the micro fly's eye lenses 50, 51 are originally very small. For this reason, the number of wavefront divisions in the optical integrator 26 of the present embodiment is larger than in cases using a fly's eye lens composed of a plurality of lens elements. As a result, a high correlation is exhibited between a global light intensity distribution formed on the entrance side of the optical integrator 26 and a global light intensity distribution of the entire secondary light source formed on the illumination pupil plane 27 on the exit side. Therefore, the light intensity distributions on the entrance side of the optical integrator 26 and on a plane optically conjugate with the entrance side can also be called pupil intensity distributions.
In the case where the diffraction optical element 19 is a diffraction optical element for annular illumination, an illumination field of an annular shape centered on the optical axis AX of the illumination optical system 13 is formed on the entrance side of the optical integrator 26. As a result, the secondary light source 60 of an annular shape, which is the same as the annular illumination field formed on the entrance side, is formed on the illumination pupil plane 27 located on the exit side of the optical integrator 26. In the case where the diffraction optical element 19 is a diffraction optical element for multi-polar illumination, an illumination field of a multi-polar shape consisting of a plurality of illumination zones of a predetermined shape. (arcuate, circular, or other shape) centered on the optical axis AX of the illumination optical system 13 is formed on the entrance side of the optical integrator 26. As a result, the secondary light source 60 of a multi-polar shape, which is the same as the multi-polar illumination field formed on the entrance side, is formed on the illumination pupil plane 27 located on the exit side of the optical integrator 26. It is assumed that the present embodiment employs the diffraction optical element 19 for quadrupolar illumination.
Namely, as shown in
Beams of exposure light EL emitted from the respective surface illuminants 60a-60d are guided onto the reticle R, whereby the illumination region ER1 having the longitudinal direction along the Y-axis direction and the transverse direction along the X-axis direction is formed, as shown in
Specifically, in the case of a first pupil intensity distribution 61 formed by first incident light EL1 (cf.
In general, a light intensity profile along the Z-axis direction of the first pupil intensity distribution 61 corresponding to the center points P1a, P1b is, as shown in
Such light intensity profiles along the Z-axis direction of the pupil intensity distributions 61, 62 have little dependence on positions of respective points along the X-axis direction in the illumination region ER1 and the still exposure region ER2, but tend to vary depending upon positions of respective points along the Y-axis direction in the illumination region ER1 and the still exposure region ER2. For this reason, when the pupil intensity distributions 61, 62 individually corresponding to the respective points P1b, P2b, P3b along the Y-axis direction in the still exposure region ER2 are not uniform, there is a risk of occurrence of variation in the line width of the pattern formed on the wafer W. For solving this problem, the correction filter 24 and distribution correction optical system 31 are provided in the illumination optical system 13 of the present embodiment.
The correction filter 24 in the present embodiment has a transmittance distribution to cause extinction of beams forming the third surface illuminant 60c and the fourth surface illuminant 60d along the Z-axis direction of the secondary light source 60 formed on the illumination pupil plane 27 and to cause little extinction of beams forming the first surface illuminant 60a and the second surface illuminant 60b along the X-axis direction.
Next, the distribution correction optical system 31 in the present embodiment will be described on the basis of
As shown in
This effective filter region 65 is divided into a first filter region 65a corresponding to the first surface illuminant 60a, a second filter region 65b corresponding to the second surface illuminant 60b, a third filter region 65c corresponding to the third surface illuminant 60c, and a fourth filter region 65d corresponding to the fourth surface illuminant 60d. Specifically, the filter regions 65a-65d are formed by partitioning the effective filter region 65 by a first line L1 (indicated by a dashed line in
The third filter region 65c and the fourth filter region 65d out of the filter regions 65a-65d are not subjected to a treatment for extinction of the exposure light EL entering the respective filter regions 65c, 65d. Namely, the beams of exposure light EL emitted from the third surface illuminant 60c and the fourth surface illuminant 60d undergo little extinction even if they pass through the transmission filter 64. On the other hand, a pattern of light-blocking dots comprised of chromium or chromium oxide is formed in each of the remaining first filter region 65a and second filter region 65b, in order to implement extinction of the exposure light EL incident into each of the filter regions 65a, 65b. Specifically, a first transmittance distribution is formed in the first filter region 65a so that the transmittance is the highest in a central region in the Z-axis direction corresponding to the longitudinal direction of the still exposure region ER2 and gradually decreases with distance from the central region in the Z-axis direction. A second transmittance distribution is formed in the second filter region 65b so that the transmittance is the highest in a central region in the Z-axis direction corresponding to the longitudinal direction of the still exposure region ER2 and gradually decreases with distance from the central region in the Z-axis direction. Namely, the first transmittance distribution and the second transmittance distribution are identical to each other. Therefore, the first filter region 65a functions as a first pattern region into which the exposure light EL emitted from the first surface illuminant 60a as a first region of the secondary light source 60 is incident and the second filter region 65b functions as a second pattern region into which the exposure light EL emitted from the second surface illuminant 60b as a second region different from the first surface illuminant 60a in the secondary light source 60 is incident. In
In passing, each of the surface illuminants 60a-60d of the secondary light source 60 formed on the illumination pupil plane 27 is formed by the beams of exposure light EL to enter the respective points in the still exposure region ER2 on the wafer W. Namely, the first incident beam EL1 in the exposure light EL to enter the center point P1b passes at a first angle (predetermined angle) relative to the optical axis AX of the illumination optical system 13 in each surface illuminant 60a-60d. The second incident beam EL2 in the exposure light EL to enter the peripheral point P2b passes at a second angle (predetermined angle) larger than the first angle relative to the optical axis AX of the illumination optical system 13 in each surface illuminant 60a-60d. The third incident beam EL3 in the exposure light EL to enter the peripheral point P3b passes at a third angle (predetermined angle) nearly equal to the second angle relative to the optical axis AX of the illumination optical system 13 in each surface illuminant 60a-60d.
Then the incident beams EL1-EL3 emitted from a large number of unillustrated point light sources (predetermined points) constituting the first surface illuminant 60a pass each through the first filter region 65a located in the −X-directional side with respect to the division plane D2 in the transmission filter 64. The incident beams EL1-EL3 emitted from a large number of unillustrated point light sources (predetermined points) constituting the second surface illuminant 60b pass each through the second filter region 65b located on the +X-directional side with respect to the division plane D2 in the transmission filter 64. The incident beams EL1-EL3 emitted from a large number of unillustrated point light sources (predetermined points) constituting the third surface illuminant 60c pass each through the third filter region 65c located on the +Z-directional side (the upper side in
As a result, a first incidence region 66 is formed in the first filter region 65a by the exposure light EL emitted from the first surface illuminant 60a and a second incidence region 67 is formed in the second filter region 65b by the exposure light EL emitted from the second surface illuminant 60b. Furthermore, a third incidence region 68 is formed in the third filter region 65c by the exposure light EL emitted from the third surface illuminant 60c and a fourth incidence region 69 is formed in the fourth filter region 65d by the exposure light EL emitted from the fourth surface illuminant 60d.
The distribution correction optical system 31, as shown in
An example of action in adjustment of the pupil intensity distributions 61, 62 corresponding to the respective points P1b, P2b, P3b along the Y-axis direction in the still exposure region ER2 will be described below on the basis of
When the exposure light EL emitted from the light source device 12 is incident into the diffraction optical element 19, the diffraction optical element 19 emits the exposure light EL of the quadrupolar sectional shape. Then this exposure light EL passes through the correction filter 24 arranged at or near the position optically conjugate with the illumination pupil plane 27, whereby the secondary light source 60 having the first surface illuminant 60a and the second surface illuminant 60b subjected to correction (extinction) by the correction filter 24 and the third surface illuminant 60c and the fourth surface illuminant 60d subjected to little correction by the correction filter 24 is formed on the illumination pupil plane 27 formed on the exit side of the optical integrator 26. On this occasion, the correction filter 24 also corrects the pupil intensity distribution on the pupil conjugate plane optically conjugate with the illumination pupil plane 27 (e.g., the arrangement position of the reticle blind 29).
The correction filter 24 in the present embodiment is a filter for reducing the light intensity of the third surface illuminant 60c and the fourth surface illuminant 60d along the Z-axis direction of the secondary light source 60 formed on the illumination pupil plane 27. As described above, in the first pupil intensity distribution 61 corresponding to the center points P1a, P1b in the illumination region ER1 on the reticle R and in the still exposure region ER2 on the wafer W, when the correction filter 24 is not located in the optical path of the exposure light EL, the light intensity of the first surface illuminant 61a and the second surface illuminant 61b along the X-axis direction is weaker than the light intensity of the third surface illuminant 61c and the fourth surface illuminant 61d along the Z-axis direction. For this reason, in the first pupil intensity distribution 61, the correction filter 24 makes the light intensity of the third surface illuminant 61c and the fourth surface illuminant 61d approximately equal to the light intensity of the first surface illuminant 61a and the second surface illuminant 61b. On the other hand, in the second pupil intensity distribution 62 corresponding to the peripheral points P2a, P2b, P3a, P3b in the illumination region ER1 and in the still exposure region ER2, when the correction filter 24 is not located in the optical path of the exposure light EL, the light intensity of the first surface illuminant 62a and the second surface illuminant 62b along the X-axis direction is stronger than the light intensity of the third surface illuminant 62c and the fourth surface illuminant 62d along the Z-axis direction. For this reason, in the second pupil intensity distribution 62, the correction filter 24 increases the difference between the light intensity of the first surface illuminant 61a and the second surface illuminant 62b and the light intensity of the third surface illuminant 62c and the fourth surface illuminant 62d on the contrary.
For adjusting the first pupil intensity distribution 61 and the second pupil intensity distribution 62 to distributions with properties substantially identical to each other, it is necessary to slightly reduce the light intensity of the first surface illuminant 61a and the second surface illuminant 61b of the first pupil intensity distribution 61 and largely reduce the light intensity of the first surface illuminant 62a and the second surface illuminant 62b of the second pupil intensity distribution 62. In the present embodiment, therefore, the pupil intensity distribution measuring device 36 measures the light intensity of the quadrupolar pupil intensity distribution for each point in the still exposure region ER2, in the secondary light source 60 formed on the illumination pupil plane 27. In this example, the measuring device measures each of the first pupil intensity distribution 61 and the second pupil intensity distribution 62 formed on the illumination pupil plane 27 by the incident beams EL1, EL2, EL3 to enter the center point P1b and the peripheral points P2b, P3b in the still exposure region ER2. In this case, the first pupil intensity distribution 61 and the second pupil intensity distribution 62 have mutually different properties. For this reason, through the drive of the unrepresented reciprocal movement device, the transmission filter 64 is arranged in the optical path of the exposure light EL emitted from the first surface illuminant 60a of the secondary light source 60 and in the optical path of the exposure light EL emitted from the second surface illuminant 60b. On this occasion, the transmission filter 64 is located at the position approximately identical in the Y-axis direction to the illumination pupil plane 27 (which will be referred to hereinafter as “initial position”) in the first adjustment region 63.
Then the first incidence region 66a and the second incidence region 67a formed on the transmission filter 64 by the first surface illuminant 61a and the second surface illuminant 61b of the first pupil intensity distribution 61 are formed in respective central regions in the Z-axis direction in the first filter region 65a and in the second filter region 65b (cf.
When the transmission filter 64 is moved in the +Y-direction (to the right in
The incidence positions into the transmission filter 64 of the respective second incident beams EL2 emitted from the respective surface illuminants 62a-62d of the second pupil intensity distribution 62 corresponding to the peripheral point P2b gradually move in the −Z-direction (to the lower side in
The incidence positions into the transmission filter 64 of the respective third incident beams EL3 emitted from the surface illuminants 62a-62d of the second pupil intensity distribution 62 corresponding to the peripheral point P3b gradually move in the +Z-direction (to the upper side in
When the transmission filter 64 is moved away from the illumination pupil plane 27 along the Y-axis direction as described above, the first incidence regions 66b, 66c corresponding to the peripheral points P2b, P3b are formed at their respective positions different in the Z-axis direction from the position of the first incidence region 66a corresponding to the center point P1b. The second incidence regions 67b, 67c are formed at their respective positions different in the Z-axis direction from the position of the second incidence region 67a. Namely, the first incidence regions 66b, 66c and the second incidence regions 67b, 67c are formed. at the respective positions where the extinction action is stronger than in the first incidence region 66a and the second incidence region 67a in the filter regions 65a, 65b. For this reason, the first incident beams EL1 emitted from the first surface illuminant 61a and the second surface illuminant 61b of the first pupil intensity distribution 61 are subjected to slight extinction by the transmission filter 64 and the second incident beams EL2 and the third incident beams EL3 emitted from the first surface illuminant 62a and the second surface illuminant 62b of the second pupil intensity distribution 62 are subjected to great extinction by the transmission filter 64. In addition, each of the first filter region 65a and the second filter region 65b is formed so that the extinction mode on the +Z-directional side with respect to the center in the Z-axis direction is approximately equal to the extinction mode on the −Z-directional side with respect to the center in the Z-axis direction. Therefore, the second incident beams EL2 and the third incident beams EL3 emitted from the first surface illuminant 62a and the second surface illuminant 62b undergo extinction at the same level as passing through the transmission filter 64.
As a result, the property of the first pupil intensity distribution 61 becomes approximately identical to the property of the second pupil intensity distribution 62. Namely, the light intensity of the first incident beams EL1 to enter the center point P1b of the still exposure region ER2 from the respective surface illuminants 61a-61d become approximately equal to the light intensity of the second incident beams EL2 and the third incident beams EL3 to enter the peripheral points P2b, P3b of the still exposure region ER2 from the respective surface illuminants 62a-62d. Therefore, when an exposure process is executed in this state, occurrence of variation in the line width of the pattern formed on the surface Wa of the wafer W is suppressed because the pupil intensity distributions 61, 62 corresponding to the respective points P1b, P2b, P3b along the Y-axis direction in the still exposure region ER2 on the wafer W have much the same properties.
Therefore, the present embodiment can achieve the effects described below.
(1) The transmission filter 64 arranged in the first adjustment region 63 is formed with the transmittance characteristic varying according to positions of incidence of the exposure light EL. By moving this transmission filter 64 along the optical axis AX of the illumination optical system 13 in the first adjustment region 63, the pupil intensity distributions 61, 62 at the respective points P1b-P3b in the still exposure region ER2 on the wafer W are independently adjusted. This permits the pupil intensity distributions 61, 62 at the respective points P1b-P3b in the still exposure region ER2 to be adjusted to distributions with properties substantially identical to each other.
(2) In the present embodiment, the correction filter 24 for equally adjusting the pupil intensity distributions 61, 62 corresponding to the respective points P1b-P3b in the still exposure region ER2 on the wafer W is provided at the position optically conjugate with the surface Wa of the wafer W on the light source device 12 side with respect to the optical integrator 26. Then the pupil intensity distributions 61, 62 corresponding to the respective points P1b-P3b in the still exposure region ER2 are adjusted so as to be substantially uniform, by the cooperative action of the correction filter 24 and the transmission filter 64. For this reason, the pupil intensity distributions 61, 62 corresponding to the respective points P1b-P3b in the still exposure region ER2 can be adjusted in higher precision than in the case where the correction filter 24 is not located in the optical path of the exposure light EL. Therefore, the exposure process for the wafer W can be carried out under an appropriate illumination condition according to the circuit pattern of the reticle R and, as a result, the pattern can be faithfully formed in a desired line width across the entire area of the wafer W.
(3) In the present embodiment, the transmission filter 64 moves along the Y-axis direction, based on the measurement results calculated based on the detection signals from the pupil intensity distribution measuring device 36, i.e., based on the pupil intensity distributions 61, 62 corresponding to the respective points P1a-P3a in the illumination region ER1 of the reticle R. For this reason, if the pupil intensity distributions 61, 62 vary because of deterioration of at least one optical element out of the various optical elements constituting the illumination optical system 13, the transmission filter 64 is moved based on the measurement results by the pupil intensity distribution measuring device 36, whereby the pupil intensity distributions 61, 62 can be quickly adjusted so that the distributions with the properties are modified to distributions with desired properties.
(4) The transmission filter 64 is arranged near the illumination pupil plane 27. For this reason, as the transmission filter 64 is moved along the Y-axis direction, each of positional relations changes among the incidence regions 66a-69a formed on the transmission filter 64 by the first incident beams EL1 emitted from the respective surface illuminants 61a-61d of the first pupil intensity distribution 61 and the incidence regions 66b-69b, 66c-69c formed on the transmission filter 64 by the second incident beams EL2 and the incident beams EL3 emitted from the respective surface illuminants 62a-62d of the second pupil intensity distribution 62. Namely, the properties of the respective pupil intensity distributions 61, 62 can be adjusted by changing the positional relations among the incidence regions 66a-69a, the incidence regions 66b-69b, and the incidence regions 66c-69c.
(5) In the present embodiment, as the transmission filter 64 is moved along the Y-axis direction, the forming positions of the incidence regions 66b-69b, 66c-69c formed by the second incident beams EL2 and the third incident beams EL3 on the transmission filter 64 are displaced each along the Z-axis direction. The first filter region 65a and the second filter region 65b each are formed so as to have different transmittances depending upon positions in the Z-axis direction, corresponding to the displacement along the Z-axis direction of the incidence regions 66b-69b, 66c-69c. For this reason, the properties of the respective pupil intensity distributions 61, 62 can be suitably adjusted by moving the transmission filter 64 of the present embodiment along the Y-axis direction in the first adjustment region 63.
(6) In the present embodiment, the filter regions 65a-65d corresponding to the respective surface illuminants 60a-60d are formed in the single transmission filter 64. For this reason, the configuration of the distribution correction optical system 31 is prevented from becoming complicated, when compared to a configuration wherein transmission filters are individually provided for the respective surface illuminants 60a-60d.
(7) The transmittance distribution of the first filter region 65a is the same distribution as the transmittance distribution of the second filter region 65b. For this reason, it is feasible to approximately equalize the degrees of extinction of the second incident beams EL2 and the third incident beams EL3 emitted from the first surface illuminant 62a and the second surface illuminant 62b of the second pupil intensity distribution 62.
The second embodiment of the present invention will be described below according to
As shown in
As shown in
A first transmittance distribution formed on the first transmission filter 81 is the same as a second transmittance distribution formed on the second transmission filter 82. Specifically, the transmittance distribution of each transmission filter 81, 82 is formed so that the transmittance is the highest in a central region in the Z-axis direction corresponding to the longitudinal direction of the still exposure region ER2 and the transmittance gradually decreases with distance from the central region in the Z-axis direction. Such transmittance distribution is formed of a pattern of light-blocking dots comprised of chromium or chromium oxide.
Each of the incident beams EL1-EL3 emitted from the large number of unillustrated point light sources (predetermined points) constituting the first surface illuminant 60a passes through the first transmission filter 81 located on the −X-directional side with respect to the division plane D3. Each of the incident beams EL1-EL3 emitted from the large number of unillustrated point light sources (predetermined points) constituting the second surface illuminant 60b passes through the second transmission filter 82 located on the +X-directional side with respect to the division plane D3. On the other hand, the incident beams EL1-EL3 emitted from the large number of unillustrated point light sources (predetermined points) constituting the third surface illuminant 60c and the fourth surface illuminant 60d are incident into the entrance-side lens unit 33 without passing through the transmission filters 81, 82. As a result, the first incidence region 66 is formed by the exposure light EL emitted from the first surface illuminant 60a, in the first transmission filter 81 and the second incidence region 67 is formed by the exposure light EL emitted from the second surface illuminant 60b, in the second transmission filter 82.
When the transmission filters 81, 82 are arranged at the same position as the pupil conjugate plane 83 in the Y-axis direction, the incidence regions 66a-66c, 67a-67c are formed each at the center in the Z-axis direction of the transmission filters 81, 82, respectively. For this reason, the incident beams EL1-EL3 emitted from the first surface illuminant 60a and the second surface illuminant 60b are subjected to little extinction by the transmission filters 81, 82. As the transmission filters 81, 82 are moved in the direction away from the pupil conjugate plane 83 in the Y-axis direction, the forming positions of the incidence regions 66a, 67a formed in the transmission filters 81, 82 by the first incident beams EL1 emitted from the first surface illuminant 60a and the second surface illuminant 60b show little displacement in the Z-axis direction. On the other hand, the forming positions of the incidence regions 66b, 67b formed in the transmission filters 81, 82 by the second incident beams EL2 emitted from the first surface illuminant 60a and the second surface illuminant 60b each are gradually displaced in the −Z-direction as the transmission filters 81, 82 are moved along the Y-axis direction away from the pupil conjugate plane 83. The forming positions of the incidence regions 66c, 67c formed in the transmission filters 81, 82 by the third incident beams EL3 emitted from the first surface illuminant 60a and the second surface illuminant 60b each are gradually displaced in the +Z-direction as the transmission filters 81, 82 are moved along the Y-axis direction away from the pupil conjugate plane 83.
When the positions in the Y-axis direction of the transmission filters 81, 82 as described above are adjusted based on the measurement results by the pupil intensity distribution measuring device 36, the properties of the respective pupil intensity distributions 61, 62 for the respective points P1b-P3b in the still exposure region ER2 on the wafer W each are adjusted.
In the present embodiment, the transmission filters 81, 82 can be individually moved along the Y-axis direction. In this case, among the second incident beams EL2 to enter the peripheral point P2b of the still exposure region ER2, the transmittance of the second incident beam EL2 passing through the first transmission filter 81 is different from the transmittance of the second incident beam EL2 passing through the second transmission filter 82. For this reason, if it is desired to make the light intensity of the second incident beam EL2 passing through the first transmission filter 81, different from the light intensity of the second incident beam EL2 passing through the second transmission filter 82, the distance in the Y-axis direction between the first transmission filter 81 and the pupil conjugate plane 83 can be made different from the distance in the Y-axis direction between the second transmission filter 82 and the pupil conjugate plane 83. The same also applies to the third incident beams EL3 to enter the peripheral point P3b of the still exposure region ER2.
Therefore, the present embodiment can achieve the effects described below.
(8) The transmission filters 81, 82 arranged in the second adjustment region 80 each are formed so that their transmittance characteristic varies according to positions of incidence of the exposure light EL. The pupil intensity distributions 61, 62 at the respective points P1b-P3b in the still exposure region ER2 on the wafer W are independently adjusted by moving such transmission filters 81, 82 along the optical axis AX of the illumination optical system 13 in the second adjustment region 80. For this reason, the pupil intensity distributions 61, 62 at the respective points P1b-P3b in the still exposure region ER2 can be adjusted to distributions with properties substantially identical to each other.
(9) In the present embodiment, the correction filter 24 for equally adjusting the pupil intensity distributions 61, 62 corresponding to the respective points P1b-P3b in the still exposure region ER2 on the wafer W is provided at the position optically conjugate with the surface Wa of the wafer W, on the light source device 12 side with respect to the optical integrator 26. Then the pupil intensity distributions 61, 62 corresponding to the respective points P1b-P3b in the still exposure region ER2 are adjusted so as to be almost uniform, by the cooperative action of the correction filter 24 and the transmission filters 81, 82. For this reason, the pupil intensity distributions 61, 62 corresponding to the respective points P1b-P3b in the still exposure region ER2 can be adjusted in higher precision than in the case where the correction filter 24 is not located in the optical path of the exposure light EL. Therefore, the exposure process for the wafer W can be carried out under an appropriate illumination condition according to the circuit pattern of the reticle R and, as a result, the pattern can be faithfully formed in a desired line width across the entire area of the wafer W.
(10) In the present embodiment, the transmission filters 81, 82 each are moved along the Y-axis direction, based on the measurement results calculated based on the detection signals from the pupil intensity distribution measuring device 36, i.e., based on the pupil intensity distributions 61, 62 corresponding to the respective points P1a-P3a in the illumination region ER1 on the reticle R. For this reason, if the pupil intensity distributions 61, 62 show a change due to deterioration or the like of at least one optical element out of the various optical elements constituting the illumination optical system 13, the pupil intensity distributions 61, 62 can be quickly adjusted to change the distributions with the properties to distributions with desired properties, by moving the transmission filters 81, 82 on the basis of the measurement results by the pupil intensity distribution measuring device 36.
(11) The transmission filters 81, 82 are arranged each near the pupil conjugate plane 83. For this reason, movement of each of the transmission filters 81, 82 along the Y-axis direction results in changing each of positional relations among the incidence regions 66a, 67a formed in the transmission filters 81, 82 by the first incident beams EL1 emitted from the first surface illuminant 61a and the second surface illuminant 61b of the first pupil intensity distribution 61, and the incidence regions 66b, 67b, 66c, 67c formed in the transmission filters 81, 82 by the second incident beams EL2 and the incident beams EL3 emitted from the first surface illuminant 62a and the second surface illuminant 62b of the second pupil intensity distribution 62. Namely, the properties of the pupil intensity distributions 61, 62 can be adjusted by changing the positional relations among the incidence regions 66a, 67a, the incidence regions 66b, 66b, and the incidence regions 66c, 66c.
(12) In the present embodiment, as the transmission filters 81, 82 are moved along the Y-axis direction, the forming positions of the incidence regions 66b, 67c, 66c, 67c formed by the second incident beams EL2 and the third incident beams EL3 in the transmission filters 81, 82 are displaced each along the Z-axis direction. Each of the transmission filters 81, 82 is formed so as to have the transmittances varying depending upon positions in the Z-axis direction, corresponding to the displacement along the Z-axis direction of the incidence regions 66b, 67c, 66c, 67c. For this reason, the properties of the pupil intensity distributions 61, 62 can be suitably adjusted by moving the transmission filters 81, 82 of the present embodiment along the Y-axis direction in the second adjustment region 80.
(13) The first transmittance distribution of the first transmission filter 81 and the second transmittance distribution of the second transmission filter 82 are identical to each other. For this reason, when the distance in the Y-axis direction between the first transmission filter 81 and the pupil conjugate plane 83 is set to be approximately equal to the distance in the Y-axis direction between the second transmission filter 82 and the pupil conjugate plane 83, the degrees of extinction of the second incident beams EL2 and the third incident beams EL3 emitted from the first surface illuminant 62a and the second surface illuminant 62b of the second pupil intensity distribution 62 can be made approximately equal to each other.
(14) In the present embodiment, the transmission filters 81, 82 can be individually moved along the Y-axis direction. For this reason, it is feasible to individually adjust the light intensity of the second incident beams EL2 and the third incident beams EL3 passing through the first transmission filter 81 and the light intensity of the second incident beams EL2 and the third incident beams EL3 passing through the second transmission filter 82. Therefore, the properties and others of the pupil intensity distributions 61, 62 for the respective points P1b-P3b can be adjusted more finely than in the case of the first embodiment.
The third embodiment of the present invention will be described below according to
As shown in
Each of transmittance distributions of the respective transmission filters 81, 82 located on the second condenser optical system 30 side out of the transmission filters 81, 82, 81A, 82A is set, as described above, so that the transmittance is the highest at the center in the Z-axis direction and the transmittance gradually decreases with distance from the center in the Z-axis direction. Each of transmittance distributions of the respective transmission filters 81A, 82A located on the entrance-side lens unit 33 side, different from the transmission filters 81, 82, is set so that the transmittance is the lowest at the center in the Z-axis direction and the transmittance gradually increases with distance from the center in the Z-axis direction.
The distribution correction optical system 31B is provided with the movement mechanism 70 for individually moving the transmission filters 81, 82, 81A, 82A. This movement mechanism 70 is configured so as to be able to individually provide a first drive force for moving each transmission filter 81, 82, 81A, 82A along the Y-axis direction and a second drive force for moving each transmission filter 81, 82, 81A, 82A along the Z-axis direction, to the transmission filters 81, 82, 81A, 82A.
In the present embodiment, when compared to each of the above embodiments, the number of filters arranged in the respective optical paths of the exposure light EL emitted from the first surface illuminant 60a and the second surface illuminant 60b increases and each transmission filter 81, 82, 81A, 82A can be moved not only in the Y-axis direction but also in the Z-axis direction. For this reason, it is feasible to individually adjust the light intensity of each of the incident beams EL1-EL3 passing through the first transmission filters 81, 81A and the light intensity of each of the incident beams EL1-EL3 passing through the second transmission filters 82, 82A, among the incident beams EL1-EL3 to enter the respective points P1b-P3b in the still exposure region ER2 on the wafer W.
The above-described embodiments may be modified into other embodiments as described below.
The diffraction optical element 19 may be replaced by a spatial light modulator, for example, composed of a large number of microscopic element mirrors arranged in an array form and individually driven and controlled in their angle and direction of inclination, which is arranged to divide an incident beam into microscopic units corresponding to respective reflective faces and to deflect the microscopic beam units, thereby converting a cross section of the beam into a desired shape or desired size. The illumination optical system using such a spatial light modulator is disclosed, for example, in Japanese Patent Application Laid-Open No. 2002-353105.
Similarly, in the third embodiment, each of the transmission filters 81, 82, 81A, 82A may be arranged to move in the X-axis direction as well. Each of the transmission filters 81, 82 may be arranged to move only in the Y-axis direction and each of the transmission filters 81A, 82A may be arranged to move in a direction intersecting with the Y-axis direction (e.g., in the X-axis direction or in the Z-axis direction). On this occasion, the transmittance distribution of each transmission filter 81A, 82A may be adjusted so that the transmittance is the highest in the central region in the Z-axis direction and the transmittance gradually decreases with distance from the central region in the Z-axis direction.
In the case of such optical design that as the transmission filter 64 is moved along the Y-axis direction away from the illumination pupil plane 27, the forming positions of the incidence regions 66b-69b, 66c-69c formed in the transmission filter 64 by the second incident beams EL2 and the third incident beams EL3 are displaced each in the X-axis direction, the transmission filter 64 may be a filter designed as described below. Namely, the transmission filter 64 may be a filter set so that the transmittance is the highest in the central region in the X-axis direction in the first filter region 65a and the second filter region 65b thereof and the transmittance gradually decreases with distance from the central region in the X-axis direction.
Similarly, in the case of such optical design that as the transmission filters 81, 82 are moved along the Y-axis direction away from the pupil conjugate plane 83, the forming positions of the respective incidence regions 66b-69b, 66c-69c formed in the transmission filters 81, 82 by the second incident beams EL2 and the third incident beams EL3 are displaced each in the X-axis direction, the transmission filters 81, 82 may be filters designed as described below. Namely, the transmission filters 81, 82 may be filters set so that the transmittance is the highest in the central region in the X-axis direction and the transmittance gradually decreases with distance from the central region in the X-axis direction.
Furthermore, an optical element without power may be arranged between the pupil conjugate plane 83 and the entrance-side lens unit 33. In this case, the second adjustment region 80 where the transmission filters 81, 82, 81A, 82A are arranged is a region between the second condenser optical system 30 and the optical element without power.
Of course, optical elements without power may be arranged on both sides in the Y-axis direction of the pupil conjugate plane 83. In this case, a region between the optical elements without power is the second adjustment region 80 where the transmission filters 81, 82, 81A, 82A are arranged.
In the second embodiment, the transmission filters 81, 82 may be arranged in the first adjustment region 63. This configuration can also achieve the same effects as the second embodiment. Furthermore, in the third embodiment, the transmission filters 81, 82, 81A, 82A may be arranged in the first adjustment region 63. Furthermore, it is also possible to adopt a configuration wherein the transmission filters 81, 82 each are arranged in the second adjustment region 80 and the transmission filters 81A, 82A each are arranged in the first adjustment region 63. This configuration can also achieve the same effects as the third embodiment.
The following will describe an embodiment of a microdevice manufacturing method using the device manufacturing method with the exposure apparatus 11 in the embodiment of the present invention, in a lithography process.
First, step S101 (design step) is to design functions and performance of microdevices (e.g., circuit design of semiconductor devices or the like) and to design a pattern for realizing the functions. Subsequently, step S102 (mask production step) is to produce a mask (reticle R or the like) on which the designed circuit pattern is formed. On the other hand, step S103 (substrate manufacturing step) is to manufacture a substrate using a material such as silicon, glass, or ceramics (which is a wafer W in the case of the silicon material being used).
Next, step S104 (substrate processing step) is to form an actual circuit and others on the substrate by the lithography technique and others, as described below, using the mask and substrate prepared in steps S101-S104. Thereafter, step S105 (device assembly step) is to assemble devices, using the substrate processed in step S104. This step S105 includes steps such as a dicing step, a bonding step, and a packaging step (chip encapsulation) on an as-needed basis. Finally, step S106 (inspection step) is to perform inspections such as an operation check test and a durability test of microdevices fabricated in step S105. The microdevices are completed through these steps and then they are shipped.
Step S111 (oxidation step) is to oxidize the surface of the substrate. Step S112 (CVD step) is to form an insulating film on the surface of the substrate. Step S113 (electrode forming step) is to form electrodes on the substrate by evaporation. Step S114 (ion implantation step) is to implant ions into the substrate. Each of the above steps S111-S114 constitutes a pretreatment step at each stage of the substrate processing and is selectively executed according to a process necessary at each stage.
After the above-described pretreatment steps are completed at the respective stages of substrate processing, posttreatment steps are carried out as described below. In the posttreatment steps, first, step S115 (resist forming step) is to apply a photosensitive material onto the substrate. Subsequently, step S116 (exposure step) is to transfer the circuit pattern of the mask onto the substrate by the lithography system (exposure apparatus 11) described above. Next, step S117 (development step) is to develop the substrate exposed in step S116 and thereby to form a mask layer consisting of the circuit pattern on the surface of the substrate. Subsequently, step S118 (etching step) is to perform etching to remove the exposed material from the part other than the part on which the resist remains. Thereafter, step S119 (resist removing step) is to remove the photosensitive material unnecessary after completion of the etching. Namely, steps S118 and S119 are to process the surface of the substrate through the mask layer. These pretreatment steps and posttreatment steps are repeatedly carried out, thereby forming multiple circuit patterns on the substrate.
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11 . . . exposure apparatus; 12 . . . light source device; 13 . . . illumination optical system; 15 . . . projection optical system; 26 . . . optical integrator; 27 . . . illumination pupil plane; 28 . . . first condenser optical system as optical element; 30 . . . second condenser optical system as first optical element; 33 . . . entrance-side lens unit as second optical element; 36 . . . pupil intensity distribution measuring device; 40 . . . control unit; 42 . . . aperture stop; 50a, 51a . . . entrance surfaces; 52-55 . . . cylindrical lens faces as unit wavefront division faces; 60a-60d . . . surface illuminants as regions; 63 . . . first adjustment region; 64, 81, 82, 81A, 82A . . . transmission filter; 64a . . . optically transparent member; 65a-65d . . . pattern regions, or filter regions as partial regions; 70 . . . movement mechanism; 72 . . . drive source; 80 . . . second adjustment region; 83 . . . image-plane conjugate plane; AX . . . optical axis; D1-D3 . . . division planes; EL . . . exposure light; ER1 . . . illumination region as irradiated region; ER2 . . . still exposure region as irradiated region; P1a-P3a, P1b-P3b . . . points as predetermined points; Ra . . . illumination target surface; W . . . wafer as substrate; and Wa . . . surface as illumination target surface.
| Number | Date | Country | |
|---|---|---|---|
| 61193802 | Dec 2008 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2009/067340 | Oct 2009 | US |
| Child | 13168068 | US |
