JP4482874B2 - Projection optical system, exposure apparatus, and exposure method - Google Patents

Description

  The present invention relates to a projection optical system, an exposure apparatus, and an exposure method, and more particularly to a projection optical system suitable for an exposure apparatus used when a device such as a semiconductor element or a liquid crystal display element is manufactured in a photolithography process. .

  In a photolithography process for manufacturing semiconductor elements, etc., a mask (or reticle) pattern image is projected and exposed on a photosensitive substrate (a wafer coated with a photoresist, a glass plate, etc.) via a projection optical system. An exposure apparatus is used. In the exposure apparatus, as the degree of integration of semiconductor elements and the like is improved, the resolving power (resolution) required for the projection optical system is increasing.

  Therefore, in order to satisfy the requirement for the resolution of the projection optical system, it is necessary to shorten the wavelength λ of the illumination light (exposure light) and increase the image-side numerical aperture NA of the projection optical system. Specifically, the resolution of the projection optical system is represented by k · λ / NA (k is a process coefficient). The image-side numerical aperture NA is n, where n is the refractive index of the medium (usually a gas such as air) between the projection optical system and the photosensitive substrate, and θ is the maximum incident angle on the photosensitive substrate.・ It is expressed by sinθ.

  In this case, if the maximum incident angle θ is increased to increase the image-side numerical aperture, the incident angle to the photosensitive substrate and the exit angle from the projection optical system increase, and the reflection loss on the optical surface increases. Thus, a large effective image-side numerical aperture cannot be ensured. Therefore, an immersion technique is known in which an image-side numerical aperture is increased by filling a medium such as a liquid having a high refractive index in the optical path between the projection optical system and the photosensitive substrate.

  Here, for example, when an attempt is made to secure a large image-side numerical aperture and a large image field (an effective imaging region in which the aberration is suppressed within a desired range) by using an immersion technique or the like, the optical members constituting the projection optical system It is necessary to increase the effective diameter, and inconvenience arises in that a high-quality optical material cannot be stably used to form an optical member having a large effective diameter. In particular, if a large image-side numerical aperture is ensured, the object-side numerical aperture inevitably increases, so the effective diameter of the lens near the object surface tends to increase.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a projection optical system that can selectively use a combination of a numerical aperture and an image field. In addition, the present invention uses a projection optical system that can selectively use a combination of a numerical aperture and an image field, and by using a combination of an exposure area and a resolution, an exposure that can perform good projection exposure with high accuracy. An object is to provide an apparatus and an exposure method.

In order to solve the above problems, in the first embodiment of the present invention, in a projection optical system that projects an image of a first surface on a second surface in a reduced scale,
The maximum numerical aperture on the second surface side is configured to be set to at least two different values,
The maximum image height when the maximum numerical aperture on the second surface side is set to one of the at least two different values, and the maximum numerical aperture on the second surface side is the at least two different values. A projection optical system characterized in that the maximum image height when set to the other value is substantially different.

In the second aspect of the present invention, in the projection optical system that projects the reduced image of the first surface onto the second surface,
When the maximum numerical aperture on the second surface side is NA and the maximum numerical aperture on the second surface side is NA, the incident angle of the light beam incident on each optical surface and the output angle of the light beam emitted from each optical surface When the maximum value of A is A,
0.52 <sinA / NA <0.95
A projection optical system characterized by satisfying the above conditions is provided.

  In a third aspect of the present invention, an illumination system for illuminating the mask set on the first surface, and an image of a pattern on the mask for projecting onto a photosensitive substrate set on the second surface An exposure apparatus comprising the projection optical system of the first form or the second form is provided.

  In a fourth aspect of the present invention, an illumination process for illuminating the mask set on the first surface, and an image of the pattern on the mask via the projection optical system of the first or second form is provided on the second surface. And an exposure step of performing projection exposure on a photosensitive substrate set to (1).

  In the projection optical system of the present invention, the maximum numerical aperture on the image side (second surface side) can be set to two different values, and the maximum image height corresponding to each of the two maximum numerical apertures (and thus the image field). Are substantially different from each other. That is, the present invention realizes a projection optical system that can be selectively used between a combination of a relatively large numerical aperture and a relatively small image field and a combination of a relatively small numerical aperture and a relatively large image field. Can do.

  Therefore, in the exposure apparatus and the exposure method of the present invention, a projection optical system capable of selectively using a combination of the numerical aperture and the image field is used to perform projection exposure with a relatively large resolution in a relatively small exposure area, and a relatively large size. Projection exposure can be performed on the exposure region with a relatively small resolution. That is, in the exposure apparatus and the exposure method of the present invention, by properly using a combination of the exposure area and the resolution, it is possible to perform a good projection exposure with high accuracy, and thus a good device can be manufactured.

  The projection optical system of the present invention is an optical system that projects a reduced image of a first surface (a mask when applied to an exposure apparatus) onto a second surface (a photosensitive substrate when applied to an exposure apparatus). The maximum numerical aperture on the image side (second surface side) can be set to two different values, for example. The maximum image height when the image-side maximum numerical aperture is set to one value is substantially different from the maximum image height when the other value is set.

  Therefore, in the projection optical system of the present invention, it is possible to selectively use a combination of a relatively large numerical aperture and a relatively small image field and a combination of a relatively small numerical aperture and a relatively large image field. When the projection optical system of the present invention is applied to an exposure apparatus or exposure method, projection exposure is performed with a relatively large resolution in a relatively small exposure area, and projection exposure is performed with a relatively small resolution in a relatively large exposure area. be able to. Hereinafter, based on each conditional expression of this invention, the structure of this invention is demonstrated in detail.

In the present invention, it is preferable that the following conditional expression (1) is satisfied. In conditional expression (1), NA1 is the first maximum numerical aperture on the largest image side, and Y1 is the maximum image height when the maximum numerical aperture on the image side is NA1. NA2 is the second maximum numerical aperture on the smallest image side, and Y2 is the maximum image height when the maximum numerical aperture on the image side is NA2. TL is a distance between the first surface and the second surface, that is, a distance between object image points.
35 <(NA1-NA2) .TL / (Y2-Y1) <150 (1)

  The upper limit value of conditional expression (1) is a value determined by design constraints, and exceeding this upper limit value makes it difficult to correct aberrations, which is not preferable. On the other hand, if the lower limit of conditional expression (1) is not reached, the difference between the largest first maximum numerical aperture NA1 and the smallest second maximum numerical aperture NA2 becomes too small. This is not preferable because the advantage of using the combination with the resolution is lost. In order to further enhance the effect of the present invention, it is preferable to set the upper limit value of conditional expression (1) to 100 and the lower limit value to 40.

In the present invention, it is preferable that the following conditional expressions (2) and (3) are satisfied.
1.03 <Y2 / Y1 <1.5 (2)
0.02 <(NA1-NA2) <0.2 (3)

  When the upper limit value of conditional expression (2) is exceeded, the maximum image height Y1 corresponding to the largest first maximum numerical aperture NA1 and the image field becomes smaller. As a result, when it is applied to an exposure apparatus, the exposure area becomes too small, the throughput is lowered, and the chip cost is likely to increase, which is not preferable. On the other hand, below the lower limit value of conditional expression (2), the maximum image height Y1 corresponding to the largest first maximum numerical aperture NA1 becomes too large, and it is difficult to correct coma and the like over the entire image field. This is not preferable. In order to further enhance the effect of the present invention, it is preferable to set the upper limit value of conditional expression (2) to 1.3 and the lower limit value to 1.1.

  If the upper limit of conditional expression (3) is exceeded, the difference between the largest first maximum numerical aperture NA1 and the smallest second maximum numerical aperture NA2 becomes too large to be realized by one projection optical system, and the optical system This is not preferable because the manufacturing cost of the is significantly increased. On the other hand, if the lower limit value of conditional expression (3) is not reached, the difference between the largest first maximum numerical aperture NA1 and the smallest second maximum numerical aperture NA2 becomes too small. This is not preferable because the advantage of using the combination with the resolution is lost, and the improvement of the resolution is not expected. In order to further enhance the effect of the present invention, it is preferable to set the upper limit value of conditional expression (3) to 0.15 and the lower limit value to 0.04.

  In the present invention, when the refractive index of the atmosphere in the optical path of the projection optical system is 1, the optical path between the projection optical system and the image plane (second surface) has a refractive index greater than 1.1. It is preferably filled with a liquid. Thus, by adopting the configuration of the immersion optical system, for example, by interposing a medium having a refractive index larger than 1.1 in the optical path between the photosensitive substrate and the projection optical system, the projection optical system The image-side numerical aperture can be increased.

According to another aspect, the projection optical system according to the second aspect of the invention provides an image of a first surface (a mask when applied to an exposure apparatus) on a second surface (a photosensitive substrate when applied to an exposure apparatus). ), And the following conditional expression (4) is satisfied. In conditional expression (4), NA is the maximum numerical aperture on the image side (second surface side). A is the maximum value of the incident angle of the light beam incident on each optical surface and the exit angle of the light beam emitted from each optical surface when the maximum numerical aperture on the image side is NA.
0.52 <sinA / NA <0.95 (4)

  If the upper limit value of conditional expression (4) is exceeded, the maximum value A of the incident angle or exit angle becomes too large, and decentration aberrations of the lens are likely to occur. On the other hand, if the lower limit value of conditional expression (4) is not reached, the maximum value A of the incident angle or exit angle becomes too small, and it becomes difficult to correct higher-order aberrations such as spherical aberration and coma aberration. In order to further enhance the effect of the second invention, it is preferable to set the upper limit value of conditional expression (4) to 0.9 and the lower limit value to 0.58.

Embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a drawing schematically showing a configuration of an exposure apparatus according to an embodiment of the present invention. In FIG. 1, the Z axis is parallel to the optical axis AX of the projection optical system PL, the Y axis is parallel to the paper surface of FIG. 1 in the plane perpendicular to the optical axis AX, and the X axis is perpendicular to the paper surface of FIG. Are set respectively. The illustrated exposure apparatus includes an ArF excimer laser light source as the light source 100 for supplying illumination light in the ultraviolet region.

  The light emitted from the light source 100 illuminates the reticle (mask) R on which a predetermined pattern is formed in a superimposed manner via the illumination optical system IL. The optical path between the light source 100 and the illumination optical system IL is sealed with a casing (not shown), and the space from the light source 100 to the optical member on the most reticle side in the illumination optical system IL absorbs exposure light. It is replaced with an inert gas such as helium gas or nitrogen, which is a low-rate gas, or is kept in a substantially vacuum state.

  The reticle R is held in parallel to the XY plane on the reticle stage RS via a reticle holder (not shown). A pattern to be transferred is formed on the reticle R, and a rectangular pattern region is illuminated. Reticle stage RS can be moved two-dimensionally along the reticle plane (ie, XY plane) by the action of a drive system (not shown), and its position coordinates are determined by reticle interferometer RIF using reticle moving mirror RM. It is configured to be measured and position controlled. The output of the interferometer RIF is supplied to the reticle control unit CR.

  Light from the pattern formed on the reticle R forms a reticle pattern image on the wafer W, which is a photosensitive substrate, via the projection optical system PL. The wafer W is held parallel to the XY plane on the wafer stage WS via a wafer holder table (not shown). Then, a pattern image is formed in the rectangular still exposure region (effective exposure region) on the wafer W so as to optically correspond to the rectangular illumination region on the reticle R. The wafer stage WS can be moved two-dimensionally along the wafer surface (that is, the XY plane) by the action of a drive system (not shown), and its position coordinates are measured by a wafer interferometer WIF using a wafer moving mirror WM. And the position is controlled. The output of the wafer interferometer WIF is also supplied to the controller CR.

  In the exposure apparatus of the present embodiment, the optical member (parallel plane plate P1 in each embodiment) arranged closest to the reticle among the optical members constituting the projection optical system PL and the boundary lens arranged closest to the wafer. The interior of the projection optical system PL is kept airtight with the Lb, and the gas inside the projection optical system PL is replaced with an inert gas such as helium gas or nitrogen, or is almost in a vacuum state. Is retained. Further, a reticle R and a reticle stage RS are arranged in a narrow optical path between the illumination optical system IL and the projection optical system PL, but a casing (not shown) that hermetically surrounds the reticle R and the reticle stage RS. Is filled with an inert gas such as nitrogen or helium gas, or is kept in a vacuum state.

  FIG. 2 is a diagram schematically showing a configuration between the boundary lens and the wafer in each example of the present embodiment. Referring to FIG. 2, in each example of the present embodiment, the optical path between the boundary lens Lb disposed on the most wafer side of the projection optical system PL and the wafer W has a refractive index larger than 1.1. Filled with medium Lm. In each embodiment, pure water is used as the medium Lm. In order to continue filling the liquid medium Lm in the optical path between the boundary lens Lb of the projection optical system PL and the wafer W, for example, the technique disclosed in International Publication No. WO99 / 49504 or Japanese Patent Laid-Open No. 10-303114 The technique disclosed in the publication number can be used.

  In the technique disclosed in International Publication No. WO99 / 49504, the liquid (medium Lm) adjusted to a predetermined temperature is supplied between the boundary lens Lb and the wafer W through the supply pipe and the discharge nozzle from the liquid supply device. The liquid is supplied so as to fill the optical path, and the liquid is recovered from the wafer W via the recovery pipe and the inflow nozzle by the liquid supply device. On the other hand, in the technique disclosed in Japanese Patent Laid-Open No. 10-303114, the wafer holder table is configured in a container shape so as to accommodate the liquid (medium Lm), and at the center of the inner bottom (in the liquid). The wafer W is positioned and held by vacuum suction. Further, the lens barrel tip of the projection optical system PL reaches the liquid, and the optical surface on the wafer side of the boundary lens Lb reaches the liquid.

  As described above, an atmosphere in which exposure light is hardly absorbed is formed over the entire optical path from the light source 100 to the wafer W. In this way, the reticle R and the wafer W are moved relative to the projection optical system PL in a plane (XY plane) orthogonal to the optical axis AX of the projection optical system PL via the drive system that receives a command from the control unit CR. Then, a reticle pattern is scanned and exposed on each exposure area of the wafer W according to a so-called step-and-scan method.

In the first embodiment, the lens components constituting the projection optical system PL are all made of quartz (SiO _2). On the other hand, in the second embodiment, the lens component constituting the projection optical system PL is made of quartz or fluorite (CaF ₂ ). In each example, the oscillation center wavelength of ArF excimer laser light, which is exposure light, is 193.306 nm, the refractive index of quartz with respect to this center wavelength is 1.5603261, and the refractive index of fluorite is 1.5014548. is there.

  Further, as the medium Lm interposed between the boundary lens Lb and the wafer W, pure water having a refractive index of 1.435876 with respect to the exposure light is used in the first embodiment, and for the exposure light in the second embodiment. Pure water having a refractive index of 1.436640 is used. In each embodiment, the projection optical system PL is substantially telecentric on both the object side and the image side.

In each embodiment, the aspherical surface has a height in the direction perpendicular to the optical axis as y, and the distance along the optical axis from the tangential plane at the apex of the aspherical surface to the position on the aspherical surface at height y ( When the sag amount is z, the apex radius of curvature is r, the conic coefficient is κ, and the nth-order aspheric coefficient is C _n , the following equation (a) is obtained. In each embodiment, the lens surface formed in an aspherical shape is marked with * on the right side of the surface number.

z = (y ² / r) / [1+ {1− (1 + κ) · y ² / r ² } ^1/2 ]
+ C ₄ · y ⁴ + C ₆ · y ⁶ + C ₈ · y ⁸ + C ₁₀ · y ¹⁰
+ C ₁₂ · y ¹² + C ₁₄ · y ¹⁴ + ... (a)

[First embodiment]
FIG. 3 is a diagram showing a lens configuration of the projection optical system according to the first example of the present embodiment. Referring to FIG. 3, in the projection optical system PL of the first embodiment, in order from the reticle side, a plane parallel plate P1, a biconcave lens L1 with an aspherical concave surface facing the wafer side, and a concave surface facing the reticle side are shown. Negative meniscus lens L2, positive meniscus lens L3 having an aspheric concave surface on the reticle side, positive meniscus lens L4 having a concave surface on the reticle side, biconvex lens L5, and positive surface having a convex surface on the reticle side A meniscus lens L6, a positive meniscus lens L7 having a convex surface facing the reticle side, a positive meniscus lens L8 having an aspherical concave surface facing the wafer side, a biconcave lens L9, and a negative meniscus lens having a convex surface facing the reticle side L10, a biconcave lens L11 having an aspheric concave surface facing the wafer side, a plano-concave lens L12 having an aspheric concave surface facing the reticle side, and a reticle A positive meniscus lens L13 having an aspherical concave surface, a biconvex lens L14, a biconvex lens L15, a negative meniscus lens L16 having a convex surface facing the reticle, a biconvex lens L17, a biconvex lens L18, and a wafer side. A positive meniscus lens L19 having an aspherical concave surface facing the surface, a positive meniscus lens L20 having an aspherical concave surface facing the wafer side, a positive meniscus lens L21 having a convex surface facing the reticle side, and a flat surface facing the wafer side. And a plano-convex lens L22 (boundary lens Lb). In the first example, the medium Lm made of pure water is filled in the optical path between the plano-convex lens L22 as the boundary lens Lb and the wafer W.

  In the following table (1), values of specifications of the projection optical system PL according to the first example are listed. In Table (1), λ is the center wavelength of the exposure light, β is the size of the projection magnification (imaging magnification of the entire system), NA1 is the first maximum numerical aperture on the largest image side, and Y1 is the image side. Is the maximum image height when NA is NA1, NA2 is the second maximum numerical aperture on the smallest image side, Y2 is the maximum image height when the image side maximum numerical aperture is NA2, and TL is the object image. Each point-to-point distance is represented. Further, the surface number is the order of the surfaces from the reticle side, r is the radius of curvature of each surface (vertical radius of curvature: mm in the case of an aspheric surface), and d is the on-axis interval of each surface, that is, the surface interval (mm). N represents the refractive index with respect to the center wavelength. The notation in Table (1) is the same in the following Table (2).

Table (1)
(Main specifications)
λ = 193.306 nm
β = 1/4
NA1 = 1.07
Y1 = 11.5mm
NA2 = 1.00
Y2 = 13.4mm
TL = 1250mm

(Optical member specifications)
Surface number r dn Optical member (reticle surface) 50.000
1 ∞ 8.000 1.5603261 (P1)
2 ∞ 5.225
3 -1943.233 12.000 1.5603261 (L1)
4 * 191.125 47.012
5 -104.228 42.945 1.5603261 (L2)
6 -470.767 1.000
7 * -542.622 39.860 1.5603261 (L3)
8 -202.724 1.000
9 -1066.606 49.498 1.5603261 (L4)
10 -257.416 1.000
11 2900.000 53.600 1.5603261 (L5)
12 -376.177 1.000
13 254.290 54.884 1.5603261 (L6)
14 927.490 1.000
15 192.047 50.000 1.5603261 (L7)
16 405.266 1.000
17 230.501 39.859 1.5603261 (L8)
18 * 322.792 19.156
19 -2992.366 14.004 1.5603261 (L9)
20 96.198 42.051
21 1075.262 14.000 1.5603261 (L10)
22 238.222 39.560
23 -133.879 12.000 1.5603261 (L11)
24 * 248.570 31.009
25 * -309.992 15.000 1.5603261 (L12)
26 ∞ 9.148
27 * -737.276 51.000 1.5603261 (L13)
28 -176.320 1.000
29 1040.000 48.704 1.5603261 (L14)
30 -451.186 1.000
31 725.000 48.768 1.5603261 (L15)
32 -697.471 3.000
33 503.559 30.048 1.5603261 (L16)
34 281.163 111.150
35 724.563 54.923 1.5603261 (L17)
36 -564.358 1.000
37 372.647 56.556 1.5603261 (L18)
38 -1424.995 1.000
39 196.339 41.207 1.5603261 (L19)
40 * 498.912 1.000
41 147.694 36.513 1.5603261 (L20)
42 * 185.195 1.000
43 147.798 52.775 1.5603261 (L21)
44 216.307 2.256
45 238.988 46.298 1.5603261 (L22: Lb)
46 ∞ 6.000 1.435876 (Lm)
(Wafer surface)

(Aspheric data)
4 sides κ = 0
C ₄ = −1.48452 × 10 ⁻⁷ C ₆ = 5.65923 × 10 ⁻¹²
C ₈ = −2.778621 × 10 ⁻¹⁶ C ₁₀ = 2.37952 × 10 ⁻²⁰
C ₁₂ = −1.19751 × 10 ⁻²⁴ C ₁₄ = 1.82016 × 10 ⁻²⁸
C ₁₆ = −5.16714 × 10 ⁻³³

7 surfaces κ = 0
C ₄ = −1.273342 × 10 ⁻⁸ C ₆ = 2.8022 × 10 ⁻¹³
C ₈ = −4.26931 × 10 ⁻¹⁸ C ₁₀ = 4.55926 × 10 ⁻²²
C ₁₂ = −2.06887 × 10 ⁻²⁶ C ₁₄ = 1.46041 × 10 ⁻³⁰
C ₁₆ = −1.78415 × 10 ⁻³⁵

18 faces κ = 0
C ₄ = −1.79752 × 10 ⁻⁸ C ₆ = 1.95237 × 10 ⁻¹⁴
C ₈ = −3.82843 × 10 ⁻¹⁸ C ₁₀ = −3.88502 × 10 ^{−22
_{C 12 = 1.96652 × 10 -26 C}} 14 = -3.59987 × 10 -31
C ₁₆ = 7.75230 × 10 ⁻³⁷

24 surfaces κ = 0
C ₄ = 1.86641 × 10 ⁻⁸ C ₆ = −2.48589 × 10 ⁻¹²
C ₈ = −3.40085 × 10 ⁻¹⁷ C ₁₀ = 1.29001 × 10 ⁻²⁰
C ₁₂ = −4.97726 × 10 ⁻²⁵ C ₁₄ = −4.18254 × 10 ⁻²⁹
C ₁₆ = 2.90453 × 10 ⁻³³

25 faces κ = 0
C ₄ = −4.42908 × 10 ⁻⁸ C ₆ = 3.224465 × 10 ⁻¹²
C ₈ = −2.17933 × 10 ⁻¹⁸ C ₁₀ = 3.09914 × 10 ⁻²¹
C ₁₂ = −5.89781 × 10 ⁻²⁵ C ₁₄ = 1.44812 × 10 ⁻²⁸
C ₁₆ = −9.31891 × 10 ⁻³³

27 faces κ = 0
^{_{C 4 = 1.28473 × 10 -8 C}} 6 = -1.52185 × 10 -12
C ₈ = 3.27024 × 10 ⁻¹⁷ C ₁₀ = 2.99631 × 10 ⁻²¹
C ₁₂ = −3.1141 × 10 ⁻²⁵ C ₁₄ = 1.24069 × 10 ⁻²⁹
C ₁₆ = −3.63752 × 10 ⁻³⁵

40 faces κ = 0
C ₄ = 1.37642 × 10 ⁻⁸ C ₆ = 7.52294 × 10 ⁻¹⁴
C ₈ = 8.147551 × 10 ⁻¹⁸ C ₁₀ = −2.38664 × 10 ⁻²²
C ₁₂ = 1.89052 × 10 ⁻²⁶ C ₁₄ = −5.772857 × 10 ⁻³¹
C ₁₆ = 1.224235 × 10 ⁻³⁵

42 plane κ = 0
C ₄ = −4.67034 × 10 ⁻⁸ C ₆ = −9.90580 × 10 ⁻¹³
C ₈ = −5.143638 × 10 ⁻¹⁸ C ₁₀ = 1.69872 × 10 ⁻²¹
C ₁₂ = −1.07534 × 10 ⁻²⁵ C ₁₄ = 5.668180 × 10 ⁻³⁰
C ₁₆ = −1.53908 × 10 ⁻³⁴

(Values for conditional expressions)
sin A = 0.885 (A = 62.25 degrees)
(1): (1.07-1.00) × 1250 / (13.4-11.5) = 46.05
(2): 13.4 / 11.5 = 1.165
(3): (1.07-1.00) = 0.07
(4): 0.885 / 1.07 = 0.527
(4): 0.885 / 1.00 = 0.885

  FIG. 4 is a diagram showing lateral aberration when the image-side numerical aperture is NA1 = 1.07 in the first embodiment. On the other hand, FIG. 5 is a diagram showing lateral aberration when the image-side numerical aperture is NA2 = 1.00 in the first embodiment. In each aberration diagram, Y represents the image height. In the first embodiment, as is apparent from the aberration diagram of FIG. 4, when the image-side numerical aperture is NA1 = 1.07, the aberration is corrected well in an image circle having a radius (maximum image height) of 11.5 mm. You can see that Further, as apparent from the aberration diagram of FIG. 5, when the image-side numerical aperture is NA2 = 1.00, the aberration is well corrected in an image circle having a radius (maximum image height) of 13.4 mm. I understand.

[Second Embodiment]
FIG. 6 is a diagram showing a lens configuration of the projection optical system according to the second example of the present embodiment. Referring to FIG. 6, in the projection optical system PL of the second embodiment, in order from the reticle side, a plane parallel plate P1, a biconcave lens L1 with an aspherical concave surface facing the wafer side, and a concave surface facing the reticle side. Negative meniscus lens L2, positive meniscus lens L3 having an aspheric concave surface on the reticle side, positive meniscus lens L4 having a concave surface on the reticle side, biconvex lens L5, and positive surface having a convex surface on the reticle side A meniscus lens L6, a positive meniscus lens L7 having a convex surface on the reticle side, a negative meniscus lens L8 having a convex surface on the reticle side, a negative meniscus lens L9 having a convex surface on the reticle side, and an aspheric shape on the reticle side A biconcave lens L10 with the concave surface facing the lens, a biconcave lens L11 with the aspherical concave surface facing the wafer side, and a positive with the aspherical concave surface facing the reticle side Niscus lens L12, positive meniscus lens L13 having an aspherical concave surface facing the reticle side, planoconvex lens L14 having a flat surface facing the reticle side, positive meniscus lens L15 having a convex surface facing the reticle side, and convex surface facing the reticle side Negative meniscus lens L16 with a concave surface, positive meniscus lens L17 with a concave surface facing the reticle, biconvex lens L18, biconvex lens L19, positive meniscus lens L20 with an aspherical concave surface facing the wafer, and wafer A positive meniscus lens L21 having an aspherical concave surface on the side, a positive meniscus lens L22 having a convex surface on the reticle side, and a plano-convex lens L23 (boundary lens Lb) having a flat surface on the wafer side. .

  In the second embodiment, the optical path between the plano-convex lens L23 as the boundary lens Lb and the wafer W is filled with a medium Lm made of pure water. The positive meniscus lens L22 and the plano-convex lens L23 are made of fluorite, and the other lens components are made of quartz. The following table (2) lists the values of the specifications of the projection optical system PL according to the second example.

Table (2)
(Main specifications)
λ = 193.306 nm
β = 1/4
NA1 = 1.07
Y1 = 11.5mm
NA2 = 1.00
Y2 = 13.4mm
TL = 1250mm

(Optical member specifications)
Surface number r dn Optical member (reticle surface) 50.000
1 ∞ 8.000 1.5603261 (P1)
2 ∞ 5.852
3 -2113.365 13.000 1.5603261 (L1)
4 * 185.888 47.615
5 -97.794 50.000 1.5603261 (L2)
6 -275.265 1.000
7 * -1036.501 52.524 1.5603261 (L3)
8 -198.574 1.000
9 -2093.835 52.770 1.5603261 (L4)
10 -287.226 1.000
11 403.759 46.727 1.5603261 (L5)
12 -31743139.730 1.000
13 284.993 45.645 1.5603261 (L6)
14 939.519 1.000
15 221.118 38.701 1.5603261 (L7)
16 426.452 1.000
17 212.879 50.000 1.5603261 (L8)
18 109.684 38.666
19 5071.658 13.000 1.5603261 (L9)
20 187.059 38.611
21 * -157.590 13.000 1.5603261 (L10)
22 201.219 17.763
23 -50220.286 13.000 1.5603261 (L11)
24 * 264.845 37.753
25 * -180.106 50.000 1.5603261 (L12)
26 -181.462 1.000
27 * -2209.915 56.621 1.5603261 (L13)
28 -205.364 1.000
29 ∞ 28.964 1.5603261 (L14)
30 -740.060 1.000
31 588.166 33.442 1.5603261 (L15)
32 7128.859 70.809
33 1084.671 25.000 1.5603261 (L16)
34 384.974 47.258
35 -1746.086 38.201 1.5603261 (L17)
36 -415.336 1.000
37 452.017 56.871 1.5603261 (L18)
38 -943.687 1.000
39 571.441 44.135 1.5603261 (L19)
40 -950.000 1.000
41 151.067 37.579 1.5603261 (L20)
42 * 206.077 1.000
43 108.158 33.260 1.5603261 (L21)
44 * 126.289 1.000
45 112.121 36.044 1.5014548 (L22)
46 116.878 5.162
47 154.951 37.038 1.5014548 (L23: Lb)
48 ∞ 3.000 1.436640 (Lm)
(Wafer surface)

(Aspheric data)
4 sides κ = 0
C ₄ = −1.50234 × 10 ⁻⁷ C ₆ = 5.45100 × 10 ⁻¹²
C ₈ = −3.08813 × 10 ⁻¹⁶ C ₁₀ = 1.80412 × 10 ⁻²⁰
C ₁₂ = −3.626148 × 10 ⁻²⁵ C ₁₄ = 2.80704 × 10 ⁻²⁹

7 surfaces κ = 0
C ₄ = −1.773193 × 10 ⁻⁸ C ₆ = 2.885809 × 10 ⁻¹³
C ₈ = −7.27773 × 10 ⁻¹⁸ C ₁₀ = 2.15819 × 10 ⁻²²
C ₁₂ = −4.000450 × 10 ⁻²⁷ C ₁₄ = 9.55827 × 10 ⁻³²

21 surface κ = 0
C ₄ = −8.772460 × 10 ⁻⁸ C ₆ = 6.385553 × 10 ⁻¹²
C ₈ = −8.35734 × 10 ⁻¹⁶ C ₁₀ = 7.19803 × 10 ⁻²⁰
C ₁₂ = -1.97435 × 10 ⁻²⁴ C ₁₄ = −2.445042 × 10 ⁻³¹

24 surfaces κ = 0
C ₄ = −4.05044 × 10 ⁻⁸ C ₆ = 3.4426 × 10 ^{−12
_{C 8 = -5.31546 × 10 -16 C}} 10 = 4.31521 × 10 -20
C ₁₂ = −1.96913 × 10 ⁻²⁴ C ₁₄ = 3.35677 × 10 ⁻²⁹

25 faces κ = 0
C ₄ = 8.54373 × 10 ⁻⁹ C ₆ = 7.774254 × 10 ⁻¹³
C ₈ = 8.77699 × 10 ⁻¹⁷ C ₁₀ = 1.73712 × 10 ⁻²¹
C ₁₂ = 2.13724 × 10 ⁻²⁵ C ₁₄ = 1.16879 × 10 ⁻²⁹

27 faces κ = 0
C ₄ = −2.020319 × 10 ⁻⁸ C ₆ = 2.37157 × 10 ⁻¹³
C ₈ = −8.05081 × 10 ⁻¹⁸ C ₁₀ = 3.83242 × 10 ⁻²²
C ₁₂ = -1.39947 × 10 ⁻²⁶ C ₁₄ = 4.05989 × 10 ⁻³¹

42 plane κ = 0
C ₄ = -3.183183 × 10 ⁻⁸ C ₆ = 5.337362 × 10 ⁻¹³
C ₈ = 5.000269 × 10 ⁻¹⁷ C ₁₀ = −2.88861 × 10 ^{−21
_{C 12 = 8.12920 × 10 -26 C}} 14 = 5.20919 × 10 -31

44 faces κ = 0
C ₄ = 7.1127 × 10 ⁻⁹ C ₆ = −4.74144 × 10 ⁻¹²
C ₈ = −4.332394 × 10 ⁻¹⁶ C ₁₀ = −1.08738 × 10 ⁻²⁰
C ₁₂ = −3.01652 × 10 ⁻²⁵ C ₁₄ = 1.16955 × 10 ⁻²⁸

(Values for conditional expressions)
sinA = 0.870 (A = 0.46 degrees)
(1): (1.07-1.00) × 1250 / (13.4-11.5) = 46.05
(2): 13.4 / 11.5 = 1.165
(3): (1.07-1.00) = 0.07
(4): 0.870 / 1.07 = 0.814
(4): 0.870 / 1.07 = 0.870

  FIG. 7 is a diagram showing lateral aberration when the image-side numerical aperture is NA1 = 1.07 in the second embodiment. On the other hand, FIG. 8 is a diagram showing lateral aberration when the image-side numerical aperture is NA2 = 1.00 in the second embodiment. In each aberration diagram, Y represents the image height. In the second embodiment, as is apparent from the aberration diagram of FIG. 7, when the image-side numerical aperture is NA1 = 1.07, the aberration is corrected well in an image circle having a radius (maximum image height) of 11.5 mm. You can see that Further, as is apparent from the aberration diagram of FIG. 8, when the image-side numerical aperture is NA2 = 1.00, the aberration is corrected well in the image circle having a radius (maximum image height) of 13.4 mm. I understand.

  Thus, in each embodiment, the largest image-side numerical aperture NA1 = 1.07 is secured for the 193.306 nm ArF excimer laser beam, and the radius (maximum image height) is within an image circle of 11.5 mm. By securing a 22.0 mm × 5.0 mm rectangular still exposure region, for example, a reticle pattern can be scanned and exposed with the highest resolution in a 22 mm × 26 mm (or 22 mm × 33 mm) rectangular exposure region. .

  In each example, the image-side numerical aperture NA2 = 1.00 is secured for the ArF excimer laser light of 193.306 nm, and the radius (maximum image height) is within the largest image circle having 13.4 mm. A rectangular stationary exposure area of 26.0 mm × 5.0 mm can be secured, and for example, a reticle pattern can be scanned and exposed at a relatively high resolution in a rectangular exposure area of 26 mm × 33 mm.

  As described above, in the projection optical system PL of the present embodiment, a combination of a relatively large numerical aperture (NA1 = 1.07) and a relatively small image field (image circle corresponding to Y1 = 11.5 mm); It is possible to selectively use between a combination of a relatively small numerical aperture (NA2 = 1.00) and a relatively large image field (image circle corresponding to Y2 = 13.4 mm). Therefore, in the exposure apparatus of the present embodiment, projection exposure is performed with a relatively large resolution (resolution corresponding to NA1 = 1.07) in a relatively small exposure area (for example, 22 mm × 26 mm), and a relatively large exposure area (for example, Projection exposure can be performed at a relatively small resolution (resolution corresponding to NA2 = 1.00) to 26 mm × 33 mm.

  By the way, in each example of the present embodiment, the RMS value of the wavefront aberration on the image plane when the first maximum numerical aperture NA1 = 1.07, which is the largest on the image side, is set. The difference from the RMS value of the wavefront aberration on the image plane when the second maximum numerical aperture NA2 = 1.00 where the maximum numerical aperture is the smallest is suppressed to 2 mλ or less. Specifically, in the first embodiment, the difference in RMS value is 0.2 mλ, and in the second embodiment, the difference in RMS value is 0.1 mλ. Here, the RMS value of the wavefront aberration is a value on the axis, which is a design level value.

  In the present embodiment, projection exposure is performed using a combination of an exposure area and a resolution, but when exposure of a fine mask pattern is performed with emphasis on OPE (Optical Proximity Effect) characteristics and the like. In addition, when light rays exceeding the numerical aperture allowable for the projection optical system reach the exposure region, it is preferable to perform a non-execution process in which the controller CR outputs an error message and no exposure is performed. On the other hand, when a relatively rough mask pattern is exposed, the exposure can be continued only by outputting a warning from the control unit CR even if a light beam exceeding the numerical aperture allowable for the projection optical system reaches the exposure area. It is preferable to adopt a simple configuration.

  That is, in the present embodiment, when the image-side numerical aperture of the projection optical system is set to be larger than the allowable maximum image-side numerical aperture corresponding to the size of each exposure area on the photosensitive substrate. It is preferable that the control unit outputs an error message for non-execution processing of exposure or a warning prior to execution processing of exposure according to the characteristics of the pattern on the mask.

  As the illumination optical system IL of the present embodiment, for example, an illumination optical device disclosed in WO2004 / 051717A can be used. As an illumination optical device, according to a large image field (image circle corresponding to Y2) under an illumination numerical aperture (NA1 × β) corresponding to the first maximum numerical aperture NA1 having the largest maximum numerical aperture on the image side. It is desirable that the illumination area (Y2 × β) can be illuminated. The size of the illumination area by the illumination optical device is preferably made variable using a reticle / blind or a zoom / condenser optical system. Note that a zoom condenser optical system for changing the size of the illumination area without substantial light loss is disclosed in, for example, Japanese Patent Application Laid-Open No. 2001-135560.

  Here, in the case of performing projection exposure with a combination of a relatively large numerical aperture (for example, NA1 = 1.07) and a relatively small image field (for example, an image field corresponding to Y1 = 11.5 mm), an illumination optical device The size of the illumination area is changed so as to correspond to a relatively small image field (for example, an image field corresponding to Y1 = 11.5 mm). Further, when projection exposure is performed with a combination of a relatively small numerical aperture (for example, NA1 = 1.00) and a relatively large image field (for example, an image field corresponding to Y2 = 13.4 mm), the illumination optical device is used. The size of the illumination area is changed so as to correspond to a relatively large image field (for example, an image field corresponding to Y2 = 13.4 mm). In both cases, since the maximum numerical aperture of the projection optical system PL is different, the value of the illumination σ (the maximum numerical aperture on the exit side of the illumination optical system / the maximum numerical aperture on the object side of the projection optical system) is also different. It is preferable to prepare an offset value of the illumination σ value according to the value of the maximum numerical aperture of the system PL, and to control the illumination σ value using this offset value.

  When only a combination of a relatively large numerical aperture (for example, NA1 = 1.07) and a relatively small image field (for example, an image field corresponding to Y1 = 11.5 mm) is used, illumination optimal for this combination is used. It is also conceivable to prepare a dedicated illumination optical system having a numerical aperture and an illumination area.

  In each of the above-described embodiments, the present invention is applied to an immersion type projection optical system in which a liquid is interposed in an optical path between the photosensitive substrate, but the present invention is not limited to this. The present invention can also be applied to a dry projection optical system in which a gas is interposed in the optical path between the photosensitive substrate and the photosensitive substrate.

  In the second embodiment described above, the positive meniscus lens L22 and the plano-convex lens L23 are formed of fluorite, so that the orientation relation of the crystal axes of the pair of fluorite lenses (L22, L23) is appropriately set. As a result, the influence of intrinsic birefringence of fluorite can be reduced. For example, WO2003 / 007045 (or US Patent Publication US2003 / 0053036A) discloses a technique for reducing the influence of intrinsic birefringence of fluorite by appropriately setting the orientation relation of crystal axes of a pair of fluorite lenses. Etc. can be referred to.

  In the exposure apparatus of the above-described embodiment, the reticle (mask) is illuminated by the illumination device (illumination process), and the transfer pattern formed on the mask is exposed to the photosensitive substrate using the projection optical system (exposure process). Thus, a micro device (semiconductor element, imaging element, liquid crystal display element, thin film magnetic head, etc.) can be manufactured. Hereinafter, referring to the flowchart of FIG. 9 for 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 this embodiment. I will explain.

  First, in step 301 of FIG. 9, 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 one lot of wafers. Thereafter, in step 303, using the exposure apparatus of the present embodiment, the image of the pattern on the mask is sequentially exposed and transferred to each shot area on the wafer of one lot via the projection optical system. Thereafter, in step 304, the photoresist on the one lot of wafers is developed, and in step 305, the resist pattern is etched on the one lot of wafers to form a pattern on the mask. Corresponding circuit patterns are formed in each shot area on each wafer.

  Thereafter, a device pattern such as a semiconductor element is manufactured by forming a circuit pattern of an upper layer. According to the semiconductor device manufacturing method described above, a semiconductor device having an extremely fine circuit pattern can be obtained with high throughput. In steps 301 to 305, a metal is deposited on the wafer, a resist is applied on the metal film, and exposure, development, and etching processes are performed. Prior to these processes, on the wafer. It is needless to say that after forming a silicon oxide film, a resist may be applied on the silicon oxide film, and steps such as exposure, development, and etching may be performed.

  In the exposure apparatus of this embodiment, a liquid crystal display element as a micro device can be obtained by forming a predetermined pattern (circuit pattern, 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 of FIG. In FIG. 10, in a pattern forming process 401, a so-called photolithography process is performed in which a mask pattern is transferred and exposed to a photosensitive substrate (such as a glass substrate coated with a resist) using the exposure apparatus of the present embodiment. 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 steps such as a developing step, an etching step, and a resist stripping step, whereby a predetermined pattern is formed on the substrate, and the process proceeds to the next color filter forming step 402.

  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 of R, G, and B A color filter is formed by arranging a plurality of stripe filter sets in the horizontal scanning line direction. Then, after the color filter forming step 402, a cell assembly step 403 is executed. 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 assembly step 403, for example, liquid crystal is injected between the substrate having the predetermined pattern obtained in the pattern formation step 401 and the color filter obtained in the color filter formation step 402, and a liquid crystal panel (liquid crystal cell) is obtained. ). 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 element, a liquid crystal display element having an extremely fine circuit pattern can be obtained with high throughput.

In the above-described embodiment, the ArF excimer laser light source is used. However, the present invention is not limited to this, and other appropriate light sources such as a KArF excimer laser light source and an F ₂ laser light source can also be used. Here, for example, when KrF excimer laser light is used as exposure light, pure water, deionized water, or the like can be used as a medium as in the case of ArF excimer laser light. In the case of using the F ₂ laser beam as the exposure light, it may be used a fluorine-based liquid such as permeable as fluorine-based oil and perfluoropolyether an F ₂ laser beam (PFPE) as a medium.

  In the above-described embodiment, the present invention is applied to the projection optical system mounted on the exposure apparatus. However, the present invention is not limited to this, and the present invention is applied to other general projection optical systems. Can also be applied.

  In the above-described embodiment, a pattern is scanned and exposed on each exposure region of the wafer according to a so-called step-and-scan method while moving the reticle and wafer relative to the projection optical system. However, the present invention is not limited to this, and by performing batch exposure while driving and controlling the wafer two-dimensionally, it is also possible to sequentially expose a pattern to the shot area of the wafer according to a so-called step-and-repeat method. .

It is a figure which shows schematically the structure of the exposure apparatus concerning embodiment of this invention. It is a figure which shows roughly the structure between the boundary lens and wafer in each Example of this embodiment. It is a figure which shows the lens structure of the projection optical system concerning the 1st Example of this embodiment. It is a figure which shows a lateral aberration when the image side numerical aperture is NA1 = 1.07 in 1st Example. It is a figure which shows a lateral aberration when the image side numerical aperture is NA2 = 1.00 in 1st Example. It is a figure which shows the lens structure of the projection optical system concerning 2nd Example of this embodiment. It is a figure which shows a lateral aberration when the image side numerical aperture is NA1 = 1.07 in 2nd Example. It is a figure which shows a lateral aberration when the image side numerical aperture is NA2 = 1.00 in 2nd Example. It is a flowchart of the method at the time of obtaining the semiconductor device as a microdevice. It is a flowchart of the method at the time of obtaining the liquid crystal display element as a microdevice.

Explanation of symbols

100 Laser light source IL Illumination optical system R Reticle RS Reticle stage W Wafer WS Wafer stage CR Control unit PL Projection optical system Li Each lens component Lb Boundary lens Lm Medium (pure water)

Claims (12)

In a projection optical system that is combined with an illumination optical system capable of changing the size of an illumination area and projects an image of a first surface illuminated by the illumination optical system on a second surface in a reduced scale,
When the size of the illumination area is the first size, the maximum numerical aperture which is the maximum numerical aperture on the second surface side is set to the first maximum numerical aperture, and the maximum on the second surface is set. Set the image height to the first image height,
When the size of the illumination area is a second size different from the first size, the maximum numerical aperture, which is the maximum value of the numerical aperture on the second surface side, is different from the first maximum numerical aperture. A projection optical system characterized in that the second maximum numerical aperture is set and the maximum image height on the second surface is set to a second image height different from the first image height.
The largest first maximum numerical aperture among the maximum numerical apertures on the second surface side is NA1, the maximum image height when the maximum numerical aperture on the second surface side is NA1, and the maximum image height on the second surface side is Y1. The smallest second maximum numerical aperture among the maximum numerical apertures is NA2, the maximum image height when the maximum numerical aperture on the second surface side is NA2 is Y2, and the distance between the first surface and the second surface Is TL,
35 <(NA1-NA2) .TL / (Y2-Y1) <150
The projection optical system according to claim 1, wherein the following condition is satisfied. The largest first maximum numerical aperture among the maximum numerical apertures on the second surface side is NA1, the maximum image height when the maximum numerical aperture on the second surface side is NA1, and the maximum image height on the second surface side is Y1. When the smallest second maximum numerical aperture among the maximum numerical apertures is NA2, and the maximum image height when the maximum numerical aperture on the second surface side is NA2 is Y2,
1.03 <Y2 / Y1 <1.5
0.02 <(NA1-NA2) <0.2
The projection optical system according to claim 1, wherein the following condition is satisfied. When the refractive index of the atmosphere in the optical path of the projection optical system is 1, the optical path between the projection optical system and the second surface is filled with a liquid having a refractive index greater than 1.1. The projection optical system according to claim 1, wherein: The largest first numerical aperture among the largest numerical apertures on the second surface side is NA1, the smallest second largest numerical aperture among the largest numerical apertures on the second surface side is NA2, and the second surface When the maximum numerical aperture on the side is NA1, the maximum value of the incident angle of the light beam incident on each optical surface and the output angle of the light beam emitted from each optical surface is A1, and the maximum numerical aperture on the second surface side is When the maximum value of the incident angle of the light beam incident on each optical surface and the exit angle of the light beam emitted from each optical surface at NA2 is A2,
0.52 <sinA1 /NA1<0.95
0.52 < sinA2 / NA2 <0.95
The projection optical system according to claim 1, wherein the following condition is satisfied. The maximum numerical aperture on the second surface side includes a first maximum numerical aperture and a second maximum numerical aperture,
When the operating wavelength of the projection optical system is λ, the RMS value of the wavefront aberration on the second surface when the maximum numerical aperture on the second surface side is set to the first maximum numerical aperture, The difference from the RMS value of the wavefront aberration on the second surface when the maximum numerical aperture on the second surface side is set to the second maximum numerical aperture is 3 mλ or less. 6. The projection optical system according to any one of items 1 to 5. In a projection optical system for reducing and projecting an image of a first surface onto a second surface,
When the maximum numerical aperture on the second surface side is NA and the maximum numerical aperture on the second surface side is NA, the incident angle of the light beam incident on each optical surface and the output angle of the light beam emitted from each optical surface When the maximum value of A is A,
0.52 <sinA / NA <0.95
A projection optical system characterized by satisfying the following conditions. The projection optical system according to any one of claims 1 to 7, wherein the projection optical system is substantially telecentric on both sides. 9. An illumination system for illuminating a mask set on the first surface, and an image of a pattern on the mask projected onto a photosensitive substrate set on the second surface. An exposure apparatus comprising the projection optical system according to item 1. The numerical aperture on the second surface side of the projection optical system is set to be larger than the maximum numerical aperture on the second surface side that is allowed corresponding to the size of each exposure region on the photosensitive substrate. In this case, a control unit for outputting an error message for non-execution processing of exposure or a warning prior to execution processing of exposure according to the characteristics of the pattern on the mask is further provided. Item 10. The exposure apparatus according to Item 9. An illumination process for illuminating the mask set on the first surface, and an image of the pattern on the mask is set on the second surface via the projection optical system according to any one of claims 1 to 8. And an exposure step of performing projection exposure on the photosensitive substrate. In the exposure step, the numerical aperture on the second surface side of the projection optical system is larger than the maximum numerical aperture on the second surface side that is allowed corresponding to the size of each exposure region on the photosensitive substrate. 12. The exposure method according to claim 11, wherein, when set, the non-execution process or the execution process is performed according to a characteristic of the pattern on the mask.

Images