Optical: systems and elements – Lens – With reflecting element
Patent
1996-01-19
1998-04-21
Nelms, David C.
Optical: systems and elements
Lens
With reflecting element
359631, 359663, 359732, 359739, G02B 1700, G02B 2714, G02B 1322, G02B 900
Patent
active
057424365
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a catadioptric reduction objective having a concave mirror, a beam splitting surface and several lens groups.
BACKGROUND OF THE INVENTION
For an objective of this kind in accordance with U.S. Pat. No. 5,402,267, the system diaphragm is arranged at: the location of the concave mirror, on the input and output surface of the beam splitter facing the concave mirror or in the space between the concave mirror and the beam splitter. The same applies to EP 0,341,385; EP 0,350,955; EP 0,465,882; and, EP 0,554,994. In such arrangements, the highest attainable numerical aperture for usable image quality is 0.60.
In the arrangement of the same class according to DE 4,110,296, the diaphragm is mounted on the beam splitting surface of the beam splitter. The beam splitter is used in transmission on the reticle side and is used in reflection on the wafer side. The consequences are: the diaphragm is no longer variable; and, the elliptically formed diaphragm is positioned greatly inclined (approximately 45.degree.) to the optical axis. Different image heights with varying main ray angles at the diaphragm utilize diaphragm apertures which are of different size which leads to contrast variations, telecentric variations and intensity variations.
A catadioptric reduction projection objective is known from U.S. Pat. No. 5,289,312. This catadioptric reduction projection objective has: a first lens group; a partially transmitting mirror (disposed so as to be inclined) on a plane-parallel plate or in a beam splitter; a concave mirror; a scattering second lens group between the two mirrors; a third lens group having a positive refractive index at the end of the light path for image generation; and, a diaphragm between the partially transmitting mirror and the third lens group.
The embodiment having the beam splitter is given only in claim 11 and is otherwise not described. The numerical aperture of the single example is only 0.45. Quartz and fluorite are alternately combined for achromatization. The partially transmitting mirror is used first in reflection and thereafter in transmission.
A beam splitter in the sense of this application has a beam splitter surface arranged between two prisms like a beam splitter cube. The beam splitter surface is therefore a partially transmitting mirror.
SUMMARY OF THE INVENTION
The object of the invention is to realize a catadioptric reduction objective having a possible numerical aperture of significantly greater than 0.60 wherein the system diaphragm is intended to lie rearward of the beam splitter surface.
Preferably, the main ray and peripheral ray angles at the beam splitter should be sufficiently small in order to make possible a polarization beam splitter. Furthermore, the objective should preferably be telecentric at the image side. In addition, the beam splitter should be as small as possible under these conditions.
Such an objective is used for microlithographic projection with image end structures in the submicron range and is built into a microlithographic projection apparatus for this purpose.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described with reference to the drawings wherein:
FIG. 1a is a lens section of a catadioptric reduction objective;
FIG. 1b is an enlarged detail of FIG. 1a but with an exchanged sequence of reflection and transmission at the beam splitter;
FIG. 2 is a schematic of a microlithographic projection apparatus; and,
FIG. 3 is a lens section of a catadioptric reduction objective having a system diaphragm within the third lens group.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
FIG. 1a is an example of a 4:1 reduction objective according to the invention for microlithography with the three lens groups (100, 200), 300, 400, the beam splitter surface 15 in the beam splitter 150 and with the concave mirror 19. The object plane (for the reticle) lies at 0, the image plane for the wafer is at 36. A deflection mirror 5 between the first part 100 and second part 200 of the first
REFERENCES:
patent: 4953960 (1990-09-01), Williamson
patent: 5052763 (1991-10-01), Singh et al.
patent: 5212593 (1993-05-01), Williamson et al.
patent: 5289312 (1994-02-01), Hashimoto et al.
patent: 5402267 (1995-03-01), Furter et al.
Carl-Zeiss-Stiftung
Nelms David C.
Ottesen Walter
Schwartz Jordan M.
LandOfFree
Maximum aperture catadioptric reduction objective for microlitho does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Maximum aperture catadioptric reduction objective for microlitho, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Maximum aperture catadioptric reduction objective for microlitho will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2063997