Projection objective having a high aperture and a planar end surface
View Patent ↗A projection objective for imaging a pattern provided in an object plane of the projection objective onto an image plane of the projection objective suitable for microlithography projection exposure machines has a plurality of optical elements transparent for radiation at an operating wavelength of the projection objective. At least one optical element is a high-index optical element made from a high-index material with a refractive index n≧1.6 at the operating wavelength.
1. A projection objective comprising:
a plurality of optical elements transparent to radiation at an operating wavelength of the projection objective and including a lens starting from which a convergent beam path begins to converge and remains convergent up to an image plane, and
an aperture diaphragm arranged at a distance of at least 10 mm from the lens and on the image side of the lens,
wherein the operating wavelength is a deep ultraviolet wavelength λ≧193 nm, and
wherein at least one of the optical elements has a refractive index n≧1.6 at the operating wavelength.
2. The projection objective according to claim 1 , having an object-side numerical aperture NA Obj greater than 0.3.
3. The projection objective according to claim 1 , wherein the plurality of optical elements comprises a last optical element arranged closest to the image plane and made at least partly of a high-index material having a refractive index n>1.6 at the operating wavelength.
4. The projection objective according to claim 3 , wherein the last optical element is a monolithic piano-convex lens made of a high-index material having a refractive index n>1.6 at the operating wavelength.
5. The projection objective according to claim 1 , having an image-side numerical aperture NA greater than 1.3.
6. The projection objective according to claim 1 , having an image-side numerical aperture 1.7≦NA≦1.8.
7. The projection objective according to claim 1 , wherein the plurality of optical elements form:
a first objective part for imaging a pattern provided in an object plane of the projection objective into a first intermediate image;
a second objective part including at least one concave mirror for imaging the first intermediate image into a second intermediate image; and
a third objective part for imaging the second intermediate image onto the image plane.
8. The projection objective according to claim 7 , wherein each of the first and third objective parts is a refractive objective part.
9. A projection objective comprising:
a plurality of optical elements transparent to radiation at an operating wavelength of the projection objective and including a lens starting from which a convergent beam path begins to converge and remains convergent up to an image plane, and
a pupil plane arranged at a distance of at least 10 mm from the lens and on the image side of the lens,
wherein the operating wavelength is a deep ultraviolet wavelength λ≧193 nm, and
wherein at least one of the optical elements has a refractive index n≧1.6 at the operating wavelength.