An aspheric reduction objective has a catadioptric partial objective (L1), an intermediate image (IMI) and a refractive partial objective (L2). The catadioptric partial objective has an assembly centered to the optical axis and this assembly includes two mutually facing concave mirrors (M1, M2). The cutouts in the mirrors (B1, B2) lead to an aperture obscuration which can be held to be very small by utilizing lenses close to the mirrors and having a high negative refractive power and aspheric lens surfaces (27, 33). The position of the entry and exit pupils can be corrected with aspherical lens surfaces (12, 48, 53) in the field lens groups. The number of spherical lenses in the refractive partial objective can be reduced with aspherical lens surfaces (66, 78) arranged symmetrically to the diaphragm plane. Neighboring aspheric lens surfaces (172, 173) form additional correction possibilities.
|
0. 61. A catadioptric objective wherein a light beam is transmitted along a light path and said catadioptric objective comprising:
a first partial objective defining an intermediate image plane;
a second partial objective mounted downstream or upstream of said first partial objective;
said first and second partial objectives conjointly defining a common optical axis and being centered thereon;
said first partial objective being a catadioptric objective according to claim 52 and said second partial objective being a purely refractive objective.
0. 73. A catadioptric objective wherein a light beam is transmitted along a light path from an object plane to an image plane and said catadioptric objective defining an optical axis, said catadioptric objective comprising:
a first concave mirror being arranged concavely to the object plane;
a second concave mirror being arranged concavely to the image plane;
and a plurality of lenses, having two mutually adjacent aspheric surfaces,
wherein said two mutually adjacent aspheric lens surfaces conjointly define a space therebetween filled with a medium having a refractive index <1.1.
0. 82. A catadioptric objective wherein a light beam is transmitted along a light path from an object plane to an image plane and said catadioptric objective defining an optical axis, said catadioptric objective comprising in sequence of travel of said light beam:
a first lens group being arranged centered on said optical axis;
a first concave mirror being arranged centered on said optical axis downstream of said first lens group and being arranged concavely to the object plane;
a second concave mirror being arranged centered on said optical axis downstream of said first concave mirror and being arranged concavely to the image plane;
a second lens group being arranged centered on said optical axis downstream of said second concave mirror;
wherein said optical axis is a straight optical axis;
wherein the catadioptric objective is arranged to define an intermediate image plane downstream from said second concave mirror.
0. 52. A catadioptric objective wherein a light beam is transmitted along a light path and said catadioptric objective defining an optical axis, said catadioptric objective comprising in sequence of travel of said light beam:
a first lens group arranged centered on said optical axis;
a first concave mirror being arranged downstream of said first lens group;
a second concave mirror being arranged downstream of said first concave mirror;
said first and second concave mirrors being disposed so as to face each other;
a second lens group being arranged centered on said optical axis downstream of said second concave mirror;
said first lens group having a first plurality of lenses;
said second lens group having a second plurality of lenses; and,
one of said first and second plurality of lenses having at least one aspheric lens surface,
wherein said catadioptric objective has an object end region and an image end region and said catadioptric objective comprising a field lens group disposed in one of said object end region and said image end region, said field lens group having said aspheric lens surface.
0. 74. A catadioptric objective wherein a light beam is transmitted along a light path from an object plane to an image plane and said catadioptric objective defining an optical axis, said catadioptric objective comprising in sequence of travel of said light beam:
a first lens group being arranged centered on said optical axis;
a first concave mirror being arranged downstream of said first lens group and being arranged concavely to the object plane;
a second concave mirror being arranged downstream of said first concave mirror and being arranged concavely to the image plane;
a second lens group being arranged centered on said optical axis downstream of said second concave mirror;
said first lens group having a first plurality of lenses;
said second lens group having a second plurality of lenses; and,
one of said first and second plurality of lenses having at least one aspheric lens surface,
wherein said catadioptric objective has an object end region and an image end region and said catadioptric objective comprising a field lens group disposed in one of said object end region and said image end region, said field lens group having said aspheric lens surface.
1. A catadioptric objective wherein a light beam is transmitted along a light path and said catadioptric objective defining an optical axis, said catadioptric objective comprising in sequence of travel of said light beam:
a first lens group having a negative refractive power and arranged centered on said optical axis;
a first concave mirror having a central cutout and being arranged centered on said optical axis downstream of said first lens group;
a second concave mirror having a central cutout and being arranged centered on said optical axis downstream of said first concave mirror;
said first and second concave mirrors being disposed so as to face each other;
a second lens group having a negative refractive power and being arranged centered on said optical axis downstream of said second concave mirror;
said first lens group having a first plurality of lenses arranged upstream of said first concave mirror;
said second lens group having a second plurality of lenses arranged downstream of said second concave mirror; and,
one of said first and second plurality of lenses having at least one aspheric lens surface,
wherein said catadioptric objective has an object end region and an image end region and said catadioptric objective further comprising a field lens group disposed in one of said object end region and said image end region, said field lens group having said aspheric lens surface.
34. A catadioptric reduction objective wherein a light beam is transmitted along a light path and said catadioptric reduction objective comprising:
a first partial objective defining an intermediate image plane;
a second partial objective mounted downstream or upstream of said first partial objective;
said first and second partial objectives conjointly defining a common optical axis and being centered thereon;
said first partial objective being a catadioptric objective and said second partial objective being a purely refractive objective; and,
said catadioptric objective including also in sequence of the travel of said light beam:
a first lens group having a negative refractive power and arranged on said optical axis;
a first concave mirror having a central cutout and being arranged on said optical axis downstream of said first lens group;
a second concave mirror having a central cutout and being arranged on said optical axis downstream of said first concave mirror;
said first and second concave mirrors being disposed so as to face each other;
a second lens group having a negative refractive power and being arranged on said optical axis downstream of said second concave mirror;
said first lens group having a first plurality of lenses arranged upstream of said first concave mirror;
said second lens group having a second plurality of lenses arranged downstream of said second concave mirror; and,
one of said first and second plurality of lenses having at least one aspheric lens surface.
49. A microscope for imaging an object into an image plane and wherein a light beam is transmitted along a light path, said microscope defining an optical axis and comprising in sequence of travel of said light beam:
a dioptric objective arranged centered on said optical axis and defining an intermediate image plane;
a catadioptric objective centered on said axis;
said dioptric objective being disposed downstream of said object to image said object into said intermediate image plane;
said catadioptric objective imaging the image of said object in said intermediate image plane into said image plane; and,
said catadioptric objective including also in sequence of travel of said light beam:
a first lens group having a negative refractive power and arranged centered on said optical axis;
a first concave mirror having a central cutout and being arranged centered on said optical axis downstream of said first lens group;
a second concave mirror having a central cutout and being arranged centered on said optical axis downstream of said first concave mirror;
said first and second concave mirrors being disposed so as to face each other;
a second lens group having a negative refractive power and being arranged centered on said optical axis downstream of said second concave mirror;
said first lens group having a first plurality of lenses arranged upstream of said first concave mirror;
said second lens group having a second plurality of lenses arranged downstream of said second concave mirror; and,
one of said first and second plurality of lenses having at least one aspheric lens surface.
50. A microlithographic projection exposure apparatus for exposing an object including a photosensitive layer on a substrate and wherein a light beam is transmitted along a light path, comprising in sequence of travel of said light beam:
a light source;
an illuminating system downstream of said light source;
a mask holder for holding a structure mask in said light path downstream of said illuminating system;
a catadioptric objective mounted downstream of said first dioptric component objective;
a holder downstream of said catadioptric objective for holding said object in said light path;
wherein said catadioptric objective defines an optical axis, said catadioptric objective comprising in sequence of travel of said light beam:
a first lens group having a negative refractive power and arranged centered on said optical axis;
a first concave mirror having a central cutout and being arranged centered on said optical axis downstream of said first lens group;
a second concave mirror having a central cutout and being arranged centered on said optical axis downstream of said first concave mirror;
said first and second concave mirrors being disposed so as to face each other;
a second lens group having a negative refractive power and being arranged centered on said optical axis downstream of said second concave mirror;
said first lens group having a first plurality of lenses arranged upstream of said first concave mirror;
said second lens group having a second plurality of lenses arranged downstream of said second concave mirror; and,
one of said first and second plurality of lenses having at least one aspheric lens surface,
wherein said catadioptric objective has an object end region and an image end region and said catadioptric objective comprising a field lens group disposed in one of said object end region and said image end region, said field lens group having said aspheric lens surface.
2. The catadioptric objective of
said first negative lens and any lenses between said first negative lens and said first concave mirror having an overall negative refractive power;
said second plurality of lenses including at least a second negative lens and said second lens group being devoid of any additional negative lenses between said second concave mirror and said second negative lens;
said second negative lens and any lenses between said second concave mirror and said second negative lens having an overall negative refractive power; and,
said first plurality of lenses including a lens adjacent said first negative lens and said second plurality of lenses including a lens adjacent said second negative lens; and,
at least one of the following lenses having at least one aspheric lens surface: said first negative lens, said lens adjacent said first negative lens, said second negative lens and said lens adjacent said second negative lens.
0. 3. The catadioptric objective of
4. The catadioptric objective of
5. The catadioptric objective of
6. The catadioptric objective of
7. The catadioptric objective of
8. The catadioptric objective of
9. The catadioptric objective of
10. The catadioptric objective of
11. The catadioptric objective of
12. The catadioptric objective of
13. The catadioptric objective of
14. The catadioptric objective of
17. The catadioptric objective of
18. The catadioptric objective of
0.8<hG11/hG12<1.2. 19. The catadioptric objective of
wherein the aperture expansion
is at least 2.0.
21. The catadioptric objective of
22. The catadioptric objective of
25. The catadioptric objective of
27. The catadioptric objective of
29. The catadioptric objective of
30. The catadioptric objective of
31. The catadioptric objective of
32. The catadioptric objective of
35. The catadioptric reduction objective of
36. The catadioptric reduction objective of
37. The catadioptric reduction objective of
39. The catadioptric reduction objective of
40. The catadioptric reduction objective of
41. The catadioptric reduction objective of
43. The catadioptric reduction objective of
44. The catadioptric reduction objective of
46. The catadioptric reduction objective of
47. The catadioptric reduction objective of
48. The catadioptric reduction objective of
51. The microlithographic projection exposure apparatus of
a first partial objective defining an intermediate image plane;
a second partial objective mounted downstream or upstream of said first partial objective;
said first and second partial objectives conjointly defining a common optical axis and being centered thereon;
said first partial objective being a catadioptric objective and said second partial objective being a purely refractive objective; and,
said catadioptric objective including in sequence of travel of said light beam:
a first lens group having a negative refractive power and arranged on said optical axis;
a first concave mirror having a central cutout and being arranged on said optical axis downstream of said first lens group;
a second concave mirror having a central cutout and being arranged on said optical axis downstream of said first concave mirror;
said first and second concave mirrors being disposed so as to face each other;
a second lens group having a negative refractive power and being arranged on said optical axis downstream of said second concave mirror;
said first lens group having a first plurality of lenses arranged upstream of said first concave mirror;
said second lens group having a second plurality of lenses arranged downstream of said second concave mirror; and,
one of said first and second plurality of lenses having at least one aspheric lens surface.
0. 53. The catadioptric objective of claim 52, wherein said catadioptric objective has an object end region and an image end region; and,
said catadioptric objective further comprising a field lens group disposed in one of said object end region and said image end region; and,
said field lens group having said aspheric lens surface.
0. 54. The catadioptric objective of claim 52, wherein light rays pass through said first and second lens groups in only one direction.
0. 55. The catadioptric objective of claim 52, wherein a first pupil plane is disposed in said light path between said first concave mirror and said second concave mirror.
0. 56. The catadioptric objective of claim 52, wherein said catadioptric objective has an object end region; and,
the maximum deviation of the real pupil function of said object end region from a line fit through said real pupil function is less than ±10 mrad.
0. 57. The catadioptric objective of claim 56, wherein said maximum deviation is less than ±5 mrad.
0. 58. The catadioptric objective of claim 52, wherein all of said lenses are made of the same material.
0. 59. The catadioptric objective of claim 52, wherein said first and second concave mirrors conjointly define a space therebetween containing a gas having a pressure and temperature dependency on its refractive index less than nitrogen.
0. 60. The catadioptric objective of claim 59, wherein said gas is helium.
0. 62. The catadioptric objective of claim 61, wherein the absolute value of the magnification ratio of said catadioptric reduction objective lies in the range from 0.1 to 0.5.
0. 63. The catadioptric objective of claim 62, wherein the absolute value of the magnification ratio of said first partial objective lies in a range from 0.7 to 1.3.
0. 64. The catadioptric objective of claim 61, wherein said refractive objective having at least one lens having an aspheric surface.
0. 65. The catadioptric objective of claim 63, wherein a first pupil plane is disposed in said light path between said first concave mirror and said second mirror; said refractive objective containing a second pupil plane;
said refractive objective includes a third plurality of lenses defining a first aspheric surface upstream of said second pupil plane and a second aspheric surface downstream of said second pupil plane; and,
wherein ha1 is the height of a chief ray at said first aspheric surface and ha2 is the height of a chief ray at said second aspheric surface; and, the following relationship applies:
0. 66. The catadioptric reduction objective of claim 65, wherein said relationship is:
0. 67. The catadioptric objective of claim 61, said catadioptric reduction objective having two mutually adjacent aspheric lens surfaces.
0. 68. The catadioptric objective of claim 67, said two mutually adjacent aspheric lens surfaces conjointly defining a space therebetween filled with a medium having a refractive index<1.1.
0. 69. The catadioptric objective of claim 67, wherein said refractive objective includes an aperture stop (AS2′);
ha3 is the maximum ray height of chief rays at said mutually adjacent lens surfaces; and,
hAS is the height of said aperture stop (AS2′); and, wherein the following relationship applies:
0. 70. The catadioptric objective of claim 69, wherein:
0. 71. The catadioptric objective of claim 61, wherein said refractive objective includes an object end region and an image end region; and,
said refractive objective includes a field lens group in said object end region and said field lens group including an aspheric lens surface.
0. 72. The catadioptric objective of claim 61, wherein all of said lenses are made of the same material.
0. 75. The catadioptric objective of claim 74, wherein light rays pass through said first and second lens groups in only one direction.
0. 76. The catadioptric objective of claim 74, wherein the light path between said first concave mirror and said second concave mirror is free of lenses.
0. 77. The catadioptric objective of claim 74, wherein a first pupil plane is disposed in said light path between said first concave mirror and said second concave mirror.
0. 78. The catadioptric objective of claim 74, wherein said optical axis is a straight optical axis.
0. 79. The catadioptric objective of claim 74, wherein said first concave mirror and said second concave mirror are arranged outside of said optical axis.
0. 80. The catadioptric objective of claim 74, wherein said first concave mirror and said second concave mirror have a cutout.
0. 81. The catadioptric objective of claim 74, wherein all of said lenses are made of the same material.
0. 83. The catadioptric objective of claim 82, wherein light rays pass through said first and second lens groups in only one direction.
0. 84. The catadioptric objective of claim 82, wherein the light path between said first concave mirror and said second concave mirror is free of lenses.
0. 85. The catadioptric objective of claim 82, wherein a first pupil plane is disposed in said light path between said first concave mirror and said second concave mirror.
0. 86. The catadioptric objective of claim 82, wherein said first concave mirror and said second concave mirror are arranged outside of said optical axis.
0. 87. The catadioptric objective of claim 82, wherein said first concave mirror and said second concave mirror have a cutout.
0. 88. The catadioptric objective of claim 82, wherein all of said lenses are made of the same material.
|
This application is
wherein: P is the sagitta as a function of the radius h (elevation to the optical axis) with the aspheric constants c1 to cn presented in Table 1. R is the vertex radius from Table 1. The deviations of the mirror surfaces from the spherical are moderate and can be controlled during manufacture. The type of glass listed in Table 1 is SUPRA1 or quartz.
The manufacture of such aspherical mirrors in the diameter range of 0.5 to 1 meter is known from the area of astronomic instruments. For assembly-line manufacture, shaping techniques such as galvano forming can be applied. The manufacturing accuracy does not have to be too great because conjugated corrective surfaces are available on the above-mentioned planar plate (50′/51′) or on one of the adjacent meniscus lens surfaces 48′, 49′, 53′ or 54′.
An optical element (50′, 51′) is arranged in the region of the pupil (P) following the intermediate image (Z). This optical element (50′, 51′) has non-spherical corrective surfaces.
It is also possible to provide elastic mirrors. As a departure from the known alignment cementing, these mirrors can be adjusted in an assembly phase utilizing actuators and can then be fixed on a rigid carrier. On the other hand, these mirrors can be controlled in optimal form during operation on line with, for example, piezoelectric actuators in order to compensate, for example, for thermal lens effects.
A projection exposure system is shown in
The object is identified by reference numeral 205 and can be, for example, a semiconductor wafer or LCD panel. The object 205 is held by an object holder and operating system 250.
The catadioptric reduction objective shown in
To correct residual errors, non-spherical corrective surfaces are provided in the vicinity of the diaphragm plane following the intermediate image plane. The form of the corrective surfaces is dependent upon the residual errors of the individual sample so that the aspherical corrective surfaces are not part of the objective design.
At wavelengths less than 200 nm, normal quartz glass is not suitable; however, fluoride crystals (for example, CaF2) can be used but these materials are available only to a limited extent in the required quality and size. For this reason, it is desirable to provide a design wherein the lens diameters are still further reduced so that a lesser amount of expensive fluoride material need be used.
Finally, it is better for the size of the aperture obscuration to omit the lenses of the first lens group located between the two concave mirrors.
The catadioptric reduction objective includes a catadioptric first partial objective L1 having surfaces 2 to 48 and a refractive second partial objective L2 having the surfaces 50 to 84. The catadioptric first partial objective L1 images the object plane OB slightly demagnified on the intermediate image plane IMI with a magnification ratio βL1=−0.76. The intermediate image plane IMI is imaged by the refractive second partial objective L2 on the image plane IM significantly demagnified with a magnification ratio of βL2=−0.33. In this way, the total magnification ratio β of the object plane OB in the image plane IM is β=−0.25. The circularly-shaped object field OB has a diameter of 91.2 mm and the corresponding image field IM has a diameter of 22.8 mm. If the catadioptric reduction objective is used in lithography, then object field and image field are rectangularly shaped. For example, a rectangularly-shaped field having the X-Y dimensions 22 mm×6 mm can be placed in the circular-shaped image field as would be suitable for a wafer scanner. The image end numerical aperture is NA=0.8 in the first embodiment. A numerical aperture this high in combination with a large image field has only recently been presented for projection objectives.
All lenses of this catadioptric reduction objective are made of the same material, in this case, CaF2. CaF2 has a refractive index of 1.55841 at the working wavelength of λ=157.3 nm. If one has the possibility in the wavelength region less than 250 nm to use a second material having higher dispersion in lenses having negative refractive power, then the color correction can be further improved. For example, sodium fluoride NaF as a counterpart to CaF2 is, for example, conceivable.
At wavelengths λ<200 nm, oxygen O2 is absorbent so that a gas charge with N2 or a suitable rare gas is provided. In the first embodiment, the lens intermediate spaces are filled with N2.
The catadioptric partial objective L1 comprises a first lens group G11 having surfaces 2 to 27, a first concave mirror M1 having a central cutout B1, a first pupil plane AS1, a second concave mirror M2 having a central cutout B2 and a second lens group G12 having surfaces 33 to 48. These optical components are passed through by the light rays in the sequence indicated. In
The two concave mirrors M1 and M2 facing each other fulfill two significant tasks in the catadioptric partial objective L1: the concave mirrors together with the neighboring lenses of negative refractive power generate the overcorrection of the axial chromatic aberration and the field curvature. As concave mirrors, they have a large positive refractive power but do not introduce any chromatic image errors. For chromatic overcorrection in the intermediate image plane IMI, the first lens group G11 and the second lens group G12 have a high negative refractive power whose diverging action is again compensated by the concave mirrors so that the first partial objective L1 generates a real image. Simultaneously, the lenses having negative refractive power with low marginal ray heights in combination with mirrors of positive refractive power with high marginal ray heights are the ideal correction means for field flattening. With the catadioptric partial objective L1, the field curvature in the intermediate image plane IMI can be overcorrected so that a planar image field results in the image plane IM after the imaging with the refractive partial objective L2 without additional corrective means for field flattening being needed in the refractive partial objective 12.
The mirror hole B1 of the concave mirror M1 and the mirror hole B2 of the concave mirror M2 lead to an obscuration in the pupil illumination. Specific aperture regions cannot be transmitted with this class of objectives. In the first embodiment, for an object point on the optical axis, the sine of the marginal ray angle is sine(iMax)=0.2 and the sine of the minimum possible aperture angle is sine (iMin)=0.0369. The aperture obscuration is computed at 18.5%.
A corresponding masking device is provided in the pupil plane AS1 in order to shade the rays which would impinge on the cutout B1 of the first concave mirror M1 and have an aperture angle of less than iMin. This masking device is so selected that the aperture obscuration is of the same size for all object points and lies centered to the chief ray. The minimally possible aperture obscuration of 18.5% for a point on the optical axis is increased to 20% when considering all object points. This masking device can, for example, be a circular absorbing disc which is arranged centered to the optical axis. A rod can serve as a holder which extends along the optical axis and is attached to the lens surfaces 27 and 33. In both lens surfaces, a recess can be machined (for example, with a diamond) in which the holding rod can be seated. The region about the optical axis in the vicinity of the pupil plane AS1 is not in the imaging beam path. For this reason, the holding device can be so designed that there is no effect on the imaging. A holder of the masking device having spokes or the like extending from the lens holder or mirror holder would lead to diffraction and thereby lead to a reduction of the resolution capacity.
The aperture obscuration affects the contrast transmission function of this class of objectives. For this reason, it is advantageous when the aperture obscuration is held as small as possible. All optical components of the catadioptric partial objective L1 are therefore so designed that the aperture obscuration remains limited to a minimum possible value.
It is necessary that the lenses next to the concave mirror have a large negative refractive power in order to hold the aperture obscuration small. In the embodiment, these are the lenses having the surface number 24/25, 26/27 and 33/34, 35/36. In the first lens group G11, the lenses contain concave surfaces 24 and 26, which are concave to the object plane OB and, in the second lens group G12, the lenses have concave surfaces 34 and 36 concave to the intermediate image plane IMI with very high values for the aperture ratio of lens height hmax to lens radius R. Thus, for surface 24, h24max/R24=0.72 and for surface 36, h36 max/R36=0.75. The aperture ratio of the concave surfaces for these negative lenses close to the mirrors is therefore significantly greater than 0.7.
The last lens 26/27 of the first lens group G11 is designed as a biconcave lens in order to obtain the maximum expansion of the aperture rays after the lens group G11. The angles of incidence of the aperture rays in the optically thinner medium (that is, with a refractive index less than 1.1) on the lens side 27, which faces toward the concave mirror M1, assume the largest possible values. In the present example, the sine of the incident angle with respect to the surface normal in the optically thinner medium for the marginal ray on the surface 27 for an object point on the optical axis is sine(i27RD)=0.779. Correspondingly, the first lens 33/34 of the second lens group G12 is a biconcave lens and the lens surface 33 is a surface where high angles of incidence are present. Accordingly, the sine of the angle of incidence in the optically thinner medium with respect to the surface normal for the same marginal ray is sine(i33RD)=0.722.
It is possible to greatly expand the aperture rays with the negative refractive power of the first lens group G11. Thus, the sine of the angle of the marginal ray of an object point on the optical axis is 0.200 forward of the first lens group G11 and 0.706 after the first lens group G11 with respect to the optical axis. The aperture expansion for this marginal ray therefore is 3.532. Because of the negative refractive power of the second lens group G12, the sine of the angle of the same marginal ray with respect to the optical axis reduces from 0.676 forward of the second lens group G12 to 0.304 after the second lens group G12, that is, by the factor 1/2.254.
The aperture expansion is dependent upon the magnitude of the aperture angle i1 forward of the first lens group G11. With a very great ray deflection with only a few spherical lens elements, an increase of the aperture expansion with an increasing aperture angle i1 would occur which, in the following, is identified as a positive distortion of the aperture expansion. This distortion is unwanted because it leads to an increase in the mirror diameters without being able to thereby reduce the aperture obscuration. In order to reduce the positive distortion of the aperture expansion with purely spherical lens surfaces, the negative refractive power of the lenses 24/26 and 26/27 would have to be distributed to additional lenses in order to reduce the angle of incidence of the diverging surfaces. Additional lenses would, however, lead to an increase of the structural length and to further transmission losses.
The distortion of the aperture expansion can be corrected without additional lens elements when an aspherical lens surface 27 is provided in the lens group having negative refractive power (surfaces 24 to 27). It is advantageous when the last lens surface 27 of the first lens group G11 is aspheric because, in this way, the dispersion of the ray angles directly forward of the first concave mirror M1 can be influenced. The object is to reduce the positive distortion of the aperture expansion and, in the ideal case, reverse into a negative distortion. With a reduction of the aperture expansion for increasing aperture angles i1, the mirror diameters can be reduced with the aperture obscuration remaining the same. In the present example, the aperture expansion mR=3.532 for a marginal ray having i1R=0.2. The aperture expansion mP=3.465 for a paraxial ray having i1P=0.002. The paraxial ray would not exhibit a throughgoing ray trace because of the aperture obscuration in the real system; however, it is viewed here as a fictitious system without mirror cutouts. The ratio of the aperture expansion mR for the marginal ray and mP for the paraxial ray is mR/mP=1.019. The positive distortion of the aperture expansion lies only at 2% with the aspherical lens surface 27. The first surface 33 of the second lens group G12 is likewise aspherical in order to compensate the distortion of the aperture expansion introduced by the aspherical surface 27. The surfaces 27 and 33 are next to the concave mirrors and are aspheric as are the concave mirrors M1 and M2. For this reason, the aperture rays between the first and second lens groups G11 and G12 are guided in such a manner that the mirror diameters can be reduced with aperture obscuration being constant.
To minimize the aperture obscuration further, the two concave mirrors M1 and M2 and the lenses 26/27 and 33/34, which are close to the mirrors, are arranged almost symmetrically to the pupil plane AS1. The distances of the concave mirrors M1 and M2 as also of the lens surfaces 27 and 33 to the pupil plane AS1 each are 189.73 mm. The two mirrors are arranged concave to the diaphragm plane and have similar curvatures. The negative lenses 26/27 and 33/34 are biconcave lenses. The weaker curved surfaces each face the pupil plane AS1. With this assembly, a beam trace, which is substantially symmetrical to the pupil plane AS1 results between the surfaces 27 and 33. Accordingly, a marginal ray from an object point on the optical axis has approximately the same ray elevation at the last surface 27 of the first lens group G11 and at the first surface 33 of the second lens group G12. At surface 27, the beam height hG11=40.66 mm and at surface 33, the ray height hG12=40.56 mm. With this assembly, which is symmetric to the pupil plane AS1, the contribution of the mirror holes B1 and B2 to the aperture obscuration is almost the same.
In the first embodiment, at least the peripheral regions of the lens 26/27 and the lens 33/34 are disposed in the space between the concave mirrors M1 and M2. In this way, one achieves that, on the one hand, the spacing of the lens 26/27 to the concave mirror M1 and the spacing of the lens 33/34 to the concave mirror M2 is as small as possible. On the other hand, the beam path between the concave mirrors M1 and M2 may only be minimally vignetted because of the last lens 26/27 of the first lens group G11 and the first lens 33/34 of the second lens group.
It is advantageous when the catadioptric reduction objective has an approximately homocentric entrance pupil. That means that the chief rays, which extend up to the optical axis, should intersect at one point on the optical axis.
In
The object end field lens group FL1 having the surfaces 2 to 17 has an aspheric surface 12 in order to be able to influence the object end pupil function. To provide a pupil function having a dominant linear component with an object diameter of 91.2 mm and an object end numerical aperture of NAO=0.2 would, without the aspherical surface 12, require additional lenses.
To control the pupil function, the field lens group FL11 is assembled from a first subgroup G111 having the surfaces 2 to 5 and a second subgroup G112 having the surfaces 6 to 19. Here, the first subgroup G111 has a negative refractive power and the second subgroup G112 has a positive refractive power. To mount the aspheric surface 12 in the second subgroup G112 having positive refractive power has the advantage that the amounts of higher order of the aspheric surface do not operate directly on the pupil function because of the distance to the object plane. In addition, the splitting of the beams was increased by the negative refractive power of the first subgroup G111. The lenses having the surfaces 20 to 27 form a third subgroup G113 having negative refractive power which already serves to expand the beam.
The field lens groups FL12 (having the surfaces 41 to 48) and FL21 (having the surfaces 50 to 55) are next to the intermediate image plane IMI and likewise have aspheric surfaces 48 and 53 which, in this case, influence the image end pupil function and the distortion in the image plane IM. In the image plane IM, the distribution of the chief ray angle should be as telecentric as possible. Thus, the image end pupil function for the embodiment of Table 2 runs between ±3.6 mrad. For use in microlithography, it is adequate when the image end pupil function has values between ±10 mrad.
With the overcorrection of the image field curvature with the catadioptric partial objective L1, it is not necessary to provide a narrowed beam path for Petzval correction within the dioptric partial objective L2. In this way, the lens diameters remain limited. The maximum lens diameters in the partial objective L2 is 116.5 mm at surface 62. In the first partial objective L1 too, the lens diameters are low in order to reduce the aperture obscuration. The largest lens in the catadioptric partial objective L1 is in the lens group G112 with a diameter of 130.4 mm. The mirror diameters can be held to less than 700 mm via the aspheric surfaces 27 and 33, which are close to the mirror, with an aperture obscuration of 20%. In this way, the concave mirror M1 has a diameter of 691.5 mm and the concave mirror M2 has a diameter of 663.0 mm.
The lateral aberrations of the aperture rays are only inadequately corrected with the intermediate imaging of the catadioptric partial objective L1. The large inner coma is clearly visible in
For a small aperture obscuration, the image field can be very well corrected with the combination of the catadioptric partial objective L1 and the refractive partial objective L2 and with the targeted use of aspherical surfaces. As an index for the quality of the objective, the wavefront can be considered within the image field of 22.8 mm diameter and with the image end numerical aperture of NA=0.8 with the aid of a polychromatic simulation. The root mean square (RMS) values of the wavefront deviations for a light source at 157.63 nm with a bandwidth of 1.2 pm are less than 8 mλ within the entire image field. These slight wavefront deviations can, inter alia, be explained with the excellent correction of image focal surface and spherical aberration.
In
To achieve a field-independent aperture obscuration, it is advantageous to provide a masking device also in the refractive partial objective L2. The pupil plane AS2 in the refractive partial objective L2 has a positive curvature and the chief rays intersect the optical axis between surfaces 69 and 70. For this reason, the masking device should be placed between surfaces 69 and 70. The size of the masking device is to be so selected that the aperture obscuration, which is caused by the mirror holes, is increased only so far that, for each field point, an aperture obscuration results which is the same size and centered to the chief ray. A rod can serve as a holder for the masking device. The rod runs along the optical axis and is attached to the lens surfaces 69 and 70. It is also possible to apply the masking directly to a lens surface which is close to the intersect point of the chief rays with the optical axis such as surface 70.
The lens and mirror intermediate spaces are flushed with helium in the second embodiment. The gas charge with helium affords the advantage that the pressure and temperature dependency of the refractive index with helium in comparison to nitrogen is less by a factor of 10. Thus, the temperature coefficient of the refractive index dn/dT at λ=157.6 nm, T=0° C. and p=1013 mbar for nitrogen is −1.2·10−6/K and for helium is −0.14·10−6/K, the pressure coefficient of the refractive index dn/dp for nitrogen is −0.34·10−6/mbar and, for helium, is −0.036·10−6/mbar. In the large volumes between the concave mirrors M1′ and M2′, temperature gradients, which occur during the irradiation, lead to convection. For materials with temperature-dependent refractive indices, convection causes a time-dependent deformation of the wavefronts which cannot be corrected. It is therefore advantageous to fill the space between the mirrors with a gas having minimal temperature dependency of the refractive index.
The number of lenses is to be held as low as possible in order to prevent transmission losses because of reflections at the lens surfaces. Thus, in the second embodiment, the two lenses of negative refractive power (24/25, 26/27, 33/34 and 35/36) before and after the concave mirrors of the first embodiment can be combined to one negative lens (126/127 and 133/134) each before and after the mirrors. The negative refractive power of these lenses (126/127 and 133/134) must be increased in order to obtain a ray expansion of 3.567 for the marginal ray and an aperture obscuration for an object point on the optical axis of 18%. This is, on the one hand, possible with a larger aperture ratio of lens height hmax to lens radius R. Thus, for surface 126, the quotient h126max/R126=0.814 and, for surface 134, the quotient is h134max/R134=0.800. On the other hand, the angle of incidence at the lens surfaces 127 and 133, which face toward the mirrors, was increased. In the second embodiment, the sine of the angle of incidence with respect to the surface normal in the optically thinner medium for the marginal ray for an object point on the optical axis on the surface 127 is sine(i127RD)=0.802 and, on the surface 133, sine(i133RD)=0.748.
It is advantageous in the refractive partial objective L2′ to provide a double asphere on the surfaces 172 and 173 in order to obtain a similarly good wavefront correction within the image field for the second embodiment as in the first embodiment. With the adjacent aspheric surfaces in proximity to the system pupil plane AS2′, the spherical aberration and the sine condition can be well corrected simultaneously. The double aspheres as a correction means can be used also in purely refractive and catadioptric objectives having a non-centered arrangement. The two aspheric surfaces can even form the forward side and the rear side of an individual lens. For manufacturing reasons, it is however advantageous to arrange two lenses each having an aspheric surface so that the aspheric surfaces are adjacent.
With the double asphere (172, 173) and the aspheric surfaces 164 and 176 arranged forward and rearward of the aperture stop AS2′, adequate correction means are available in order, with a modest use of material, to correct the wavefront deviation within an image field of 22.8 mm diameter and for an image end numerical aperture of NA=0.8 to less than 8 mλ. The polychromatic simulation was carried out with a light source at 157.6 nm and a bandwidth of 1.2 pm.
The examples show the combination of a coaxial catadioptric objective with a dioptric partial objective. Other combinations such as with two dioptric partial objectives forward and rearward of the catadioptric partial objective are also possible in the context of the invention.
The schematic representation of
A microlithographic projection exposure apparatus for producing microstructured components is shown schematically in
It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.
TABLE 1
SF
RADII
THICKESSES
GLASSES
0
Object
1
−152.31391
9.3670
SUPRA1
2
−934.28326
17.0479
3
−258.50662
17.9979
SUPRA1
4
−144.13579
1.5242
5
154.21865
34.9172
SUPRA1
6
−1044.16454
50.7402
7
−368.80081
10.1606
SUPRA1
Asphere on
Surface 21
8
238.39923
2.8591
9
138.64466
18.7404
SUPRA1
10
312.00878
44.3518
C 1 =
−.1984860500E−10
11
−122.26492
12.8011
SUPRA1
C 2 =
−.8471592100E−16
12
−126.81758
23.6934
C 3 =
−.1338734300E−21
13
177.47680
19.3377
SUPRA1
C 4 =
.1383973100E−27
14
11788.39412
15.9136
C 5 =
.1716228700E−32
15
−172.90112
7.5815
SUPRA1
C 6 =
.4845464500E−38
16
295.02570
40.3349
C 7 =
−.3305365300E−44
17
149.52872
16.3659
SUPRA1
18
134.69462
72.7792
19
−79.93868
10.3887
SUPRA1
20
−1129.04446
361.0000
21
−981.42317
AS
−295.0000
22
Infinity
−215.0000
Asphere on
Diaphragm
.0000
Surface 23
23
1113.03904
AS
500.6296
24
226.60310
8.2622
SUPRA1
C 1 =
.1686460500E−10
25
68.17289
114.8808
C 2 =
−.4430448700E−16
26
−91.66030
20.9850
SUPRA1
C 3 =
−.1503908600E−21
27
−111.26948
4.2440
C 4 =
.2530123600E−27
28
−1008.42184
16.6387
SUPRA1
C 5 =
−.7105016500E−35
29
−119.24333
127.0374
C 6 =
−.2345880200E−38
30
−105.29899
8.7290
SUPRA1
C 7 =
.3712453500E−43
31
−151.29067
.0532
32
6408.14692
13.0429
SUPRA1
33
−304.40400
26.5391
34
115.05002
19.9112
SUPRA1
35
113.02003
18.2856
36
480.50139
16.6611
SUPRA1
37
−425.21265
25.4688
38
−154.46333
14.1991
SUPRA1
39
−240.64362
8.7927
40
289.04838
24.5556
SUPRA1
41
−469.53160
22.0894
42
−127.91442
14.2424
SUPRA1
43
−179.26273
67.4834
44
4904.05552
29.6764
SUPRA1
45
−179.72857
8.1164
46
−152.96898
13.7764
SUPRA1
47
−203.54702
12.9619
48
−127.62811
14.1864
SUPRA1
49
−139.16594
.4118
50
Infinity
8.0000
SUPRA1
51
Infinity
4.0000
52
Infinity
.0001
53
121.70233
15.3662
SUPRA1
54
109.92284
36.1371
55
219.24113
30.1687
SUPRA1
56
−303.41760
31.5237
57
73.58279
65.3446
SUPRA1
SUPRA1 = Quartz
Glass
58
43.81552
3.1551
59
41.37557
28.5961
SUPRA1
60
604.77330
.6625
61
Image Plane
TABLE 2
Surface
Radius
Asphere
Mirror
Thickness
Material
Diameter
OB
INFINITE
26.122
N2
100.0
2
−226.258
4.000
CAF2
99.7
3
1694.910
7.361
N2
104.1
4
−210.020
4.023
CAF2
104.1
5
−4263.571
0.750
N2
110.8
6
353.550
30.488
CAF2
117.3
7
−137.865
0.750
N2
122.7
8
116.889
15.735
CAF2
130.4
9
177.655
5.923
N2
127.8
10
118.343
32.491
CAF2
126.6
11
−373.347
2.660
N2
122.1
12
−231.515
A
7.862
CAF2
122.1
13
88.994
0.864
N2
107.7
14
77.637
8.155
CAF2
108.4
15
81.208
20.608
N2
105.4
16
221.890
9.012
CAF2
105.5
17
163.578
2.429
N2
103.7
18
110.213
27.605
CAF2
104.6
19
−1324.253
9.444
N2
100.5
20
97.719
4.000
CAF2
89.4
21
64.603
14.158
N2
83.4
22
684.267
A
5.079
CAF2
83.4
23
216.155
24.074
N2
82.3
24
−57.188
2.000
CAF2
82.3
25
−92.747
5.064
N2
87.8
26
−72.557
2.000
CAF2
88.3
27
344.860
A
189.734
N2
105.0
M1
−813.737
A
S
−189.734
N2
691.5
AS1
INFINITE
−189.734
N2
677.8
M2
910.975
A
S
189.734
N2
663.0
33
−416.373
A
2.000
CAF2
106.4
34
65.887
4.948
N2
87.8
35
80.253
2.000
CAF2
87.3
36
54.610
31.217
N2
81.7
37
−84.333
7.747
CAF2
81.6
38
−75.708
0.750
N2
83.7
39
−1017.773
27.565
CAF2
81.7
40
−155.591
5.282
N2
79.9
41
−81.310
8.228
CAF2
79.9
42
−68.211
1.949
N2
80.7
43
−78.791
6.095
CAF2
77.1
44
−108.111
2.600
N2
77.2
45
−81.487
21.352
CAF2
77.2
46
−143.068
0.938
N2
80.4
47
199.620
40.095
CAF2
79.0
48
−145.642
A
20.000
N2
71.9
IM1
INFINITE
44.528
N2
67.0
50
−75.128
4.117
CAF2
69.0
51
−90.888
0.971
N2
72.4
52
−632.737
22.418
CAF2
76.6
53
408.536
A
0.900
N2
87.2
54
147.577
23.337
CAF2
91.9
55
−284.699
1.148
N2
94.9
56
544.076
28.648
CAF2
96.3
57
−917.060
10.169
N2
97.7
58
1123.355
15.459
CAF2
98.1
59
2847.866
22.266
N2
98.0
60
−84.178
4.000
CAF2
98.0
61
−351.550
0.750
N2
105.7
62
131.866
26.379
CAF2
116.5
63
−235.338
2.325
N2
116.4
64
222.992
31.521
CAF2
111.2
65
38305.126
9.715
N2
101.7
66
−2322.734
A
22.353
CAF2
96.4
67
1104.047
13.909
N2
88.6
68
−81.868
7.918
CAF2
88.6
69
−177.471
8.961
N2
91.5
70
−86.806
6.077
CAF2
91.5
71
−96.333
1.537
N2
94.4
AS2
INFINITE
0.750
N2
95.3
73
130.184
4.810
CAF2
103.5
74
97.753
2.761
N2
104.4
75
116.560
23.022
CAF2
104.4
76
−270.739
0.750
N2
105.5
77
194.680
18.881
CAF2
107.1
78
−210.640
A
0.750
142
106.4
79
55.466
43.620
CAF2
92.6
80
50.189
2.182
N2
59.6
81
37.769
13.715
CAF2
55.3
82
77.000
1.188
N2
47.9
83
60.105
8.895
CAF2
44.7
84
185.707
5.644
N2
36.9
IM
INFINITE
N2
22.8
Asphere Equation:
wherein:
ASPHERE AT SURFACE 12
RADIUS = 231.51455
MAXIMUM HEIGHT = 61.10
ASPHERIC PARAMETERS
EX = −2.3650089000
C 1 = .4794899400E−07
C 2 = .6604175100E−11
C 3 = −.7562978300E−15
C 4 = .6805192600E−19
C 5 = −.2666129900E−23
ASPHERE AT SURFACE 22
RADIUS = 684.26729
MAXIMUM HEIGHT = 41.80
ASPHERIC PARAMETERS
EX = .0000000000
C 1 = .1509596800E−06
C 2 = −.5120549400E−10
C 3 = −.5610431800E−14
C 4 = −.1117020200E−16
C 5 = .2518000300E−20
C 6 = −.1694764600E−23
ASPHERE AT SURFACE 27
RADIUS = 344.85984
MAXIMUM HEIGHT = 52.50
ASPHERIC PARAMETERS
EX = 7.0085930000
C 1 = −.5923208000E−07
C 2 = .1890459800E−10
C 3 = −.4378968800E−15
C 4 = −.5239005100E−18
C 5 = .1912278200E−21
ASPHERE AT SURFACE 29
RADIUS = −813.73677
MAXIMUM HEIGHT = 345.80
ASPHERIC PARAMETERS
EX = 1.0459455000
C 1 = −.4485550100E−10
C 2 = −.1176505800E−15
C 3 = −.1049527100E−20
C 4 = −.8619328500E−26
C 5 = −.2274167800E−31
C 6 = −.3345014000E−37
C 7 = −.3286498200E−43
ASPHERE AT SURFACE 31
RADIUS = 910.97468
MAXIMUM HEIGHT = 331.50
ASPHERIC PARAMETERS
EX = .9036275200
C 1 = .6193779100E−10
C 2 = −.1344616200E−15
C 3 = −.1509012800E−20
C 4 = −.7421992700E−26
C 5 = −.4535969900E−31
C 6 = .1986463200E−36
C 7 = −.1449901900E−41
ASPHERE AT SURFACE 33
RADIUS = −416.37282
MAXIMUM HEIGHT = 53.30
ASPHERIC PARAMETERS
EX = 13.3142580000
C 1 = .6027181300E−07
C 2 = .2450300200E−10
C 3 = −.4142498400E−14
C 4 = .3917454300E−18
C 5 = −.1088457000E−25
ASPHERE AT SURFACE 48
RADIUS = −145.64247
MAXIMUM HEIGHT = 36.00
ASPHERIC PARAMETERS
EX = −.4376678300
C 1 = −.2590488300E−07
C 2 = .4696937200E−12
C 3 = .7666469100E−16
C 4 = .8507764300E−21
C 5 = −.1186245400E−25
ASPHERE AT SURFACE 53
RADIUS = 408.53641
MAXIMUM HEIGHT = 43.60
ASPHERIC PARAMETERS
EX = −14.2359470000
C 1 = .9773912300E−07
C 2 = −.6627558800E−11
C 3 = −.2537861300E−15
C 4 = −.1281961700E−18
C 5 = −.1182417800E−25
ASPHERE AT SURFACE 66
RADIUS = −2322.73355
MAXIMUM HEIGHT = 48.20
ASPHERIC PARAMETERS
EX = −504.9485600000
C 1 = −.2616677600E−07
C 2 = −.3063442300E−10
C 3 = .3964984700E−14
C 4 = −.1714421100E−17
C 5 = −.1187390103E−25
ASPHERE AT SURFACE 78
RADIUS = −210.64008
MAXIMUM HEIGHTS = 53.20
ASPHERIC PARAMETERS
EX = 6.3257878000
C 1 = .4095943500E−07
C 2 = .1712273600E−12
C 3 = .9639448600E−15
C 4 = −.2847604400E−18
C 5 = .7274168800E−23
TABLE 3
Surface
Radius
Asphere
Minor
Thickness
Material
Diameter
OB′
INFINITY
26.122
He
50.0
102
−204.364
4.000
CaF2
49.7
103
−13179.432
7.350
He
51.9
104
−184.672
4.011
CaF2
51.9
105
−1226.241
0.753
He
55.3
106
259.607
26.956
CaF2
60.1
107
−147.776
0.750
He
61.4
108
125.704
11.380
CaF2
63.6
109
178.234
0.750
He
62.7
110
111.880
29.403
CaF2
62.4
111
−380.095
3.030
He
60.9
112
−235.417
A
17.184
CaF2
60.9
113
82.808
0.750
He
51.7
114
67.123
8.979
CaF2
52.5
115
69.627
17.234
He
50.6
116
281.120
6.567
CaF2
50.6
117
272.393
0.758
He
50.2
118
115.088
36.934
CaF2
50.2
119
389.484
0.750
He
45.5
120
88.823
4.097
CaF2
43.6
121
73.172
15.989
He
41.7
122
−1528.771
10.066
CaF2
41.4
123
217.517
13.370
He
40.3
124
−89.601
7.977
CaF2
40.3
125
−76.531
9.154
He
41.2
126
−50.697
4.001
CaF2
41.2
127
259.195
A
189.734
He
52.7
M1′
−814.100
A
S
−189.734
He
349.3
AS1′
INFINITY
−189.734
He
342.6
M2′
911.247
A
S
189.734
He
335.0
133
−276.266
A
4.000
CaF2
54.0
134
52.152
32.685
He
41.7
135
−80.264
6.728
CaF2
41.7
136
−77.215
0.850
He
42.8
137
−1419.828
32.679
CaF2
41.9
138
−147.648
5.801
He
41.0
139
−78.453
7.489
CaF2
41.0
140
−70.298
0.750
He
41.5
141
−84.334
6.166
CaF2
40.2
142
−98.563
2.147
He
40.3
143
−80.891
21.397
CaF2
40.3
144
−151.520
0.750
He
42.0
145
242.014
45.863
CaF2
41.3
146
−145.419
A
22.791
He
37.5
IMI′
INFINITY
43.060
He
33.2
148
−77.276
4.000
CaF2
34.7
149
−95.689
0.751
He
36.4
150
−894.688
22.703
CaF2
38.6
151
427.406
A
0.750
He
43.9
152
143.694
24.676
CaF2
46.4
153
−346.670
2.353
He
47.9
154
347.126
29.393
CaF2
48.8
155
−10246.191
11340
He
49.1
156
479.165
15.800
CaF2
49.3
157
634.264
23.350
He
48.8
158
−81.257
4.000
CaF2
48.8
159
−299.826
0.750
He
52.8
160
128.827
26.561
CaF2
58.6
161
−250.110
0.783
He
58.5
162
213.461
33.162
CaF2
56.1
163
−4384.454
9.042
He
51.0
164
−1171.671
A
24.405
CaF2
48.4
165
1409.721
14.203
He
44.3
166
−79.418
7.954
CaF2
44.3
167
−174.125
8.406
He
45.9
168
−85.986
6.344
CaF2
45.9
169
−94.556
0.750
He
47.5
AS2′
INFINITY
0.750
He
48.0
171
128.150
4.001
CaF2
52.4
172
99.397
A
2.565
He
52.8
173
116.720
A
23.743
CaF2
52.8
174
−265.459
0.750
He
53.3
175
220.793
18.648
CaF2
53.8
176
−192.915
A
0.751
He
53.4
177
55.415
43.719
CaF2
46.3
178
48.232
2.666
He
29.6
179
37.843
13.583
CaF2
27.5
180
77.482
0.896
He
23.8
181
61.588
9.014
CaF2
22.5
182
233.027
5.544
He
18.7
IM′
INFINITY
He
11.6
Asphere Equation:
wherein:
Patent | Priority | Assignee | Title |
Patent | Priority | Assignee | Title |
3200253, | |||
3244073, | |||
3897133, | |||
4240702, | Sep 08 1978 | The Perkin-Elmer Corporation | Field corrector for two mirror objective systems |
4669810, | Feb 03 1984 | Flight Dynamics | Head up display system |
4714307, | Jul 13 1985 | Pilkington P.E. Limited | Catadioptric infrared lenses |
5004331, | May 03 1989 | HE HOLDINGS, INC , A DELAWARE CORP ; Raytheon Company | Catadioptric projector, catadioptric projection system and process |
5031976, | Sep 24 1990 | KLA Instruments, Corporation | Catadioptric imaging system |
5114238, | Jun 28 1990 | Lockheed Corporation; Lockheed Martin Corporation | Infrared catadioptric zoom relay telescope |
5323263, | Feb 01 1993 | Nikon Corporation | Off-axis catadioptric projection system |
5359388, | Apr 02 1993 | ULTRATECH STEPPER, INC ; ULTRATECH STEPPER EAST, INC | Microlithographic projection system |
5488229, | Oct 04 1994 | EXCIMER LASER SYSTEMS, INC | Deep ultraviolet microlithography system |
5636066, | Mar 12 1993 | Nikon Corporation | Optical apparatus |
6259508, | Jan 22 1998 | Nikon Corporation | Projection optical system and exposure apparatus and method |
DE29516768, | |||
EP267766, | |||
EP396128, | |||
EP581585, | |||
EP1059550, | |||
GB890451, | |||
RU124665, |
Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
Oct 07 2005 | Carl Zeiss SMT GmbH | (assignment on the face of the patent) | / | |||
Oct 14 2010 | Carl Zeiss SMT AG | Carl Zeiss SMT GmbH | A MODIFYING CONVERSION | 025763 | /0367 |
Date | Maintenance Fee Events |
Aug 17 2011 | ASPN: Payor Number Assigned. |
Apr 02 2015 | M1553: Payment of Maintenance Fee, 12th Year, Large Entity. |
Date | Maintenance Schedule |
Jul 26 2014 | 4 years fee payment window open |
Jan 26 2015 | 6 months grace period start (w surcharge) |
Jul 26 2015 | patent expiry (for year 4) |
Jul 26 2017 | 2 years to revive unintentionally abandoned end. (for year 4) |
Jul 26 2018 | 8 years fee payment window open |
Jan 26 2019 | 6 months grace period start (w surcharge) |
Jul 26 2019 | patent expiry (for year 8) |
Jul 26 2021 | 2 years to revive unintentionally abandoned end. (for year 8) |
Jul 26 2022 | 12 years fee payment window open |
Jan 26 2023 | 6 months grace period start (w surcharge) |
Jul 26 2023 | patent expiry (for year 12) |
Jul 26 2025 | 2 years to revive unintentionally abandoned end. (for year 12) |