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Matched Legal Cases: ['art 100', 'art 200', 'art 300', 'art 200', 'art 200', 'art 100', 'art 200', 'art 300', 'art 100', 'art 200', 'art 200', 'art 300', 'art 2', 'art 1', 'art 3', 'art 2', 'art 1', 'art 3']

Patent US6424471 - Catadioptric objective with physical beam splitter - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA catadioptric projection objective comprises an object plane, a physical beam splitter, a concave mirror, an image plane, a first objective part, a second objective part, and a third objective part. The first objective part is located between the object plane and the physical beam splitter. The second...http://www.google.com/patents/US6424471?utm_source=gb-gplus-sharePatent US6424471 - Catadioptric objective with physical beam splitterAdvanced Patent SearchPublication numberUS6424471 B1Publication typeGrantApplication numberUS 09/711,256Publication dateJul 23, 2002Filing dateNov 10, 2000Priority dateNov 12, 1999Fee statusLapsedAlso published asEP1102100A2, EP1102100A3Publication number09711256, 711256, US 6424471 B1, US 6424471B1, US-B1-6424471, US6424471 B1, US6424471B1InventorsWilli Ulrich, Helmut BeierlOriginal AssigneeCarl-Zeiss-StiftungExport CitationBiBTeX, EndNote, RefManPatent Citations (17), Referenced by (10), Classifications (13), Legal Events (5) External Links: USPTO, USPTO Assignment, EspacenetCatadioptric objective with physical beam splitterUS 6424471 B1Abstract A catadioptric projection objective comprises an object plane, a physical beam splitter, a concave mirror, an image plane, a first objective part, a second objective part, and a third objective part. The first objective part is located between the object plane and the physical beam splitter. The second objective part is located between the physical beam splitter and the concave mirror, and includes at least two divergent lenses. The third objective part is located between the physical beam splitter and the image plane.
What is claimed is: 1. A catadioptric projection objective comprising:
an object plane; a physical beam splitter; a concave mirror; an image plane; a first objective part being located between said object plane and said physical beam splitter; a second objective part being located between said physical beam splitter and said concave mirror, and including at least two divergent lenses; and a third objective part being located between said physical beam splitter and said image plane. 2. The catadioptric projection objective according to claim 1, wherein said at least two divergent lenses are spatially separated in said second objective part.
an object plane; a physical beam splitter; a concave mirror; an image plane; a first objective part being located between said object plane and said physical beam splitter; a second objective part, being located between said physical beam splitter and said concave mirror; and a third objective part being located between said physical beam splitter and said image plane, wherein the catadioptric projection objective has a chromatic length aberration (CHL); wherein said second objective part is over-corrected with regard to said CHL, wherein said first and third objective parts are under-corrected with regard to said CHL, and wherein said over-correction of said second objective part, in double passage of a beam of light, compensates for at least 70% of said under-correction of said first and third objective parts. 4. The catadioptric projection objective according to claim 3, wherein said second objective part has a negative refractive power.
wherein said concave mirror has a refractive power, and wherein said refractive power of said second objective part is in a range of about 40% to about 80% of said refractive power of said concave mirror. 6. The catadioptric projection objective according to claim 3, wherein said second objective part comprises at least one positive lens.
wherein said seconds objective part includes a first negative lens and a second negative lens, and wherein said at least one positive lens is located between said first negative lens and staid second negative lens. 8. The catadioptric projection objectives according to claim 3, wherein said second objective part includes a diaphragm plane located therein.
wherein said first objective part directs a beam towards said physical beam splitter, and wherein said beam is at an angle of less than 10 degrees relative to ah optical axis at a surface of said physical beam splitter. 13. The catadioptric projection objective according to claim 3,
wherein said second objective part and said concave mirror cooperate to direct a beam towards said physical beam splitter, and wherein said beam is at an angle of less than 10 degrees relative to an optical axis at a surface of said physical beam splitter. 14. The catadioptric projection objective according to claim 3,
wherein said concave mirror has a usable diameter, and wherein said second objective part has a focal length that is at least triple said usable diameter. 15. The catadioptric projection objective according to claim 3,
wherein said first objective part has a Petzval sum (P1), wherein said second objective part has a Petzval sum (P2), wherein said third objective part has a Petzval sum (P3), wherein said concave mirror has a Petzval sum (Pc) and wherein P1, P2, P3 and Pc satisfy the equation: 2�(P 2)+P c=−(90 to 110)%�(P 1 +P 3). 16. The catadioptric projection objective according to claim 3,
wherein said second objective part has a Petzval sum in double passage, wherein said second objective part is over-corrected relative to said, Petzval sum, wherein said first and third objective parts are under-corrected relative to said Petzval sum, and wherein said over-correction of said second objective part compensates for at least 90% of said under-correction of said first and third objective parts. 17. The catadioptric projection objective according to claim 3,
wherein said third objective part has an image-side lens surface, and wherein said image-side lens surface and said image plane are separated by a distance of>5 mm. 18. The catadioptric projection objective according to claim 3, wherein said third objective part is refractive.
19. The catadioptric projection objective according to claim 3, wherein the catadioptric projection objective has a reduction β, in a range of about 4:1 through about 6:1.
23. The catadioptric projection objective according to claim 3, wherein said object plane is impinged by a chief ray at 0��20 mrad.
an object plane; a physical beam splitter; a concave mirror; an image plane; a first objective part being located between said object plane and said physical beam splitter; a second objective part being located between said physical beam splitter and said concave mirror; and a third objective part being located between said physical beam splitter and said image plane, and including an intermediate image. 34. The catadioptric projection objective according to claim 33,
wherein said third objective part includes a first lens and a second lens, and wherein said intermediate image is located between said first lens and said secondlens. 35. The catadioptric projection objective according to claim 33,
wherein the catadioptric projection objective has an image ratio between said object plane and said intermediate image, and wherein said image ratio is in the range of 1.0�0.7. 36. The catadioptric projection objective according to claim 33,
wherein said third objective part includes a lens having a positive refractive power, and wherein said lens is located between said physical beam splitter and said intermediate image. 37. The catadioptric projection objective according to claim 33,
wherein said third objective part includes a lens system located between said intermediate image and said image plane, and wherein said lens system has an image ratio of less than 1. 38. The catadioptric projection objective according to claim 33,
wherein said third objective part includes a lens system located between said intermediate image and said image plane, and wherein said lens system includes a lens having an aspherical surface. 39. The catadioptric projection objective according to claim 33,
wherein said second objective part includes a first diaphragm plane, wherein said third objective part includes a lens system located between said intermediate image and said image plane, and wherein said lens system includes a second diaphragm plane. 40. The catadioptric projection objective according to claim 39,
wherein said first and second diaphragm planes have different diameters, and wherein a greater of said different diameters is larger than a smaller of said different diameters by a factor of ≦1.5. 41. The catadioptric projection objective according to claim 33, wherein the catadioptric projection objective is telecentric in at least one of said object plane and said image plane.
wherein said catadioptric projection objective comprises a plurality of lenses, and wherein all of said plurality of lenses are comprised of a same material. 43. The catadioptric projection objective according to claim 33,
wherein said catadioptric projection objective comprises a lens that passes a beam of light having a wavelength (λ), and wherein said lens is comprised of a material based on said wavelength (λ) in accordance with the equations: for 180≦λ≦250 nm, use SiO2; for 150≦λ≦200 nm, use CaF2; for λ<160 nm, use alkali fluoride. 44. The catadioptric projection objective according to claim 33,
wherein said catadioptric projection objective comprises a lens that passes a beam of light having a wavelength (λ), wherein 150 nm≦λ≦250 nm, and wherein said lens is comprised of a material selected from the group consisting of SiO2, CaF2, BaF, and combinations thereof. 45. A projection exposure device for microlithography, comprising:
the catadioptric projection objective of claim 1, an illumination system having a light source illuminating said object plane of said catadioptric projection objective; and a mask being positioned on a first carrier system, said mask being positioned in said object plane of the catadioptric projection objective; wherein the catadioptric projecting objective projects said mask onto a light sensitive object on a second carrier system, which lies in said image plane of the catadioptric projection objective. 46. A process for producing a semiconductor comprising the step of employing the projection exposure device of claim 45.
the catadioptric projection objective of claim 3, an illumination system having a light source illuminating said object plane of said catadioptric projection objective; and mask being positioned on a first carrier system, said mask being positioned in said object plane of the catadioptric projection objective; wherein the catadioptric projecting objective projects said mask onto a light sensitive object on a second carrier system, which lies in said image plane of the catadioptric projection objective. 48. A process for producing a semiconductor comprising the step of employing the projection exposure device of claim 47.
the catadioptric projection objective of claim 33, an illumination system having a light source illuminating said object plane of said catadioptric projection objective; and a mask being positioned on a first carrier system, said mask being positioned in said object plane of the catadioptric projection objective; wherein the catadioptric projecting objective projects said mask onto a light sensitive object on a second carrier system, which lies in said image plane of the catadioptric projection objective. 50. A process for producing a semiconductor comprising the step of employing the projection exposure device of claim 49.
U.S. Pat. No. 4,896,952 shows a system with polarization-optical beam splitter, whereby the change of the direction of polarization in the catadioptric objective part is achieved by means of a λ/4 plate.
SUMMARY OF THE INVENTION A first object of the invention is thus to provide a catadioptric projection objective, which overcomes the disadvantages of DE-A 4,417,489, and particularly allows for a complete correction of the longitudinal chromatic aberration (CHL). According to the invention, this object is solved in a first embodiment by a projection system, in which more negative refraction power is arranged in the second objective part between beam splitter and concave mirror. A splitting of this high negative refraction power into at least two negative lenses is advantageous.
If the system is configured as a system with intermediate image, then advantageously the entire objective part has an imaging scale βintermediate of 1�0.7, preferably 1.5, from the object up to the intermediate image, thus the first as well as the second objective parts and concave mirror in double passage and the third objective part up to the intermediate image.
BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in the following on the basis of the figures, as an example. Here:
FIGS. 3a-3 c show the longitudinal spherical aberration, the astigmatic field course, and the distortion of the example of embodiment according to FIG. 2a; and
FIGS. 4a-4 c is a table of select characteristics of the catadioptric objective shown in FIG. 2a. DESCRIPTION OF THE INVENTION Part of the catadioptric projection objective completely shown in FIG. 2a is shown in FIG. 1 and in fact, this figure shows the first objective part 100 including convergent lenses 101, 102, with surfaces 2, 3, 4, 5; the beam-splitter prism 500; the second objective part 200 comprising three divergent lenses as well as two convergent lenses with surfaces 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 in the first passage as well as surfaces 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 in the second passage; the concave mirror 202 with surface 19, which does not belong to the second objective part as well as the convergent lens 302 of the third objective part 300 with surfaces 34, 35, arranged in front of the intermediate image.
The beam-splitter prism is preferably a polarization-optical beam-splitter prism 500, i.e., the incident light is p-polarized, for example. The light reflected by concave mirror 202 upon return passes a element for rotating the polarization, for example, a λ/4 plate, and then has, for example, s-polarization, which is not reflected, but is rather transmitted by the polarization-optical beam-splitter layer 504. The beams transmitted at the polarization-optical beam-splitter layer 504 arrive in the third objective part, of which only the convergent lens 302 in front of the intermediate image is shown in FIG. 1. The sequence of the reflecting, transmitting beam splitter layer can also be reversed. In order to compensate for the effect of the divergent group with lens surfaces 10, 15 and 17 in the second objective part upon return after reflection at concave mirror 202, at least one convergent lens 302 is provided in front of the intermediate image in the third objective part. By this configuration, the angle load on beam-splitter layer 504, i.e., the variation of the angle of incidence both in arriving from object 1 at concave mirror 202 as well as in the return from concave mirror 202 to image 1000 can be kept small. The absolute amount of the refractive power of second objective part 200 preferably amounts to 40-80% of the refractive power of concave mirror 202. The focal length of the second objective part 200 in double passage and of concave mirror 202 has at least triple the value of the free diameter of concave mirror 202.
Preferably, the angles of the chief rays as well as also of the rim rays relative to the optical axis are smaller than 10�, especially smaller than 5� at the beam splitter in air.
The system according to FIG. 2a comprises a first objective part 100, a second objective part 200, a concave mirror 202 as well as a third objective part 300, in which the intermediate image Z comes to lie. In the above depicted case the projection objective, is a 4:1 reduction objective. Reduction objectives with an imaging scale other than a 4:1 are also possible. The object, e.g., reticle, lies at 1, and the image on the wafer lies at 84. FIGS. 4a-4 c gives the radii and the distances of all optically effective surfaces 2-83. Surfaces 2-5 lie in the first objective part 100, whereby surfaces 6-8 characterize the beam-splitter surfaces for forward passage, surfaces 9-18 denote the surfaces in the second objective part 200 in forward passage, surface 19 indicates the concave mirror, surfaces 20-29 denote the surfaces in second objective part 200 in return passage, surfaces 30-32 indicate the beam-splitter surfaces in return passage, and surfaces 34-35, 37-68 and 70-83 indicate the surfaces in the third objective part 300. 36 denotes the intermediate image and 69 indicates the conjugated diaphragm. The free working distance on the object side (0-1) amounts to more than 30 mm and on the wafer side (83-84) to more than 5 mm. The numerical aperture NA lies at 0.7.
2*(CHLobjective part 2)=−106%*(CHLobjective part 1+CHLobjective part 3) The second objective part in double passage is over-corrected relative to the Petzval sum and the first and third objective parts are under-corrected, whereby the following is valid:
The following results for the example of embodiment shown in FIG. 2a: 2*(Petzval sumobjective part 2)+Petzval sumconcave minor=0.025087 and
(Petzval sumobjective part 1+Petzval sumobjective part 3)=−0.025094 i.e., the under-correction of the first and third objective part is compensated to at least 90% by the over-correction of the second objective part and concave mirror.
The imaging scale of the projection objective up to the intermediate image amounts to βintermediate=1.5.
For easier correction of imaging errors, the entire projection objective is designed as a so-called on-axis system, i.e., the chief rays (CR) are symmetric to the principal axes (PA) of the system, as shown in FIG. 2a. In order to shorten the structural length of approximately 1.1 m of the objective, in another form of embodiment of the invention, a deflecting mirror after the beam splitter and in front of the intermediate image Z can be arranged. Introducing a deflecting mirror in front of the beam splitter would also be possible. By introducing a deflecting mirror, the reticle and wafer position can be made parallel.
FIGS. 4a-4 c gives the values of an example of an lens system according to the invention shown in FIG. 2a, wherein the consecutive numbers indicate the numbers of the system surface or lens surface, which correlate with the reference numbers in FIGS. 2a and 2 b; �radius� gives its radius; �thickness� gives its thickness; and �glass� is to be understood as the material used. SiO2 is quartz glass, CaF2 is calcium fluoride single crystal.
FIG. 3a shows the longitudinal spherical aberration that results for the example of embodiment according to FIGS. 4a-4 c; FIG. 3b gives the astigmatism as a function of the height of the object and FIG. 3c gives the distortion as a function of the object height.
The embodiment was corrected chromatically as described above by negative lenses with high beam height in front of the concave mirror as well as by the use of a second material. A broadband design for 193 nm was achieved in this way, i.e., with a bandwidth of Δλ=20 pm, the chromatic length deviation amounts to only 0.22 μm. A relatively large bandwidth can also be achieved with the use of only one material, e.g., CaF2 for 157 nm, by the negative lenses in front of the mirror, when compared with a purely refractive system alone.
The catadioptric projection objective can be constructed such that it comprises a lens that passes a beam of light having a wavelength (λ), and where the lens is comprised of a material based on the wavelength (λ) in accordance with the following guidelines.
(1) For 180≦λ≦250 nm, particularly for wavelengths of 193 nm and 248 nm, SiO2 is a suitable material for the lens.
(2) For 150≦λ≦200 nm, particularly for wavelengths of 157 nm and 193 nm, CaF2 is a suitable material for the lens.
(3) For λ<160 nm, particularly for a wavelength of 157 nm, alkali fluoride is a suitable material for the lens.
(4) For 150 nm≦λ≦250 nm, particularly for wavelengths of 157 nm, 193 nm, and 248 nm, the lens material can be any of SiO2, CaF2, or BaF, and combinations thereof.
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