Photocopying – Projection printing and copying cameras – Illumination systems or details
Reexamination Certificate
1999-03-05
2001-09-25
Metjahic, Safet (Department: 2858)
Photocopying
Projection printing and copying cameras
Illumination systems or details
C355S053000
Reexamination Certificate
active
06295122
ABSTRACT:
CROSS-REFERENCES TO RELATED APPLICATIONS
Not Applicable.
Statement Regarding Federally sponsored Research or Development
Not applicable.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an illumination system for a microlithographic projection equipment, a REMA objective, and a process for the operation of a REMA objective.
2. Discussion of Relevant Prior Act
An illumination system for a microlithographic projection illumination equipment is known from U.S. Pat. No. 4,851,882, with a simple REMA objective which has a field diaphragm, namely the reticle mask (REMA), on which the reticle with the structured lithographic mask is imaged. A zoom system is provided, mounted in front, in order to insure optimum illumination of the whole REMA diaphragm surface with little loss of light, in the case of reticles with different mask dimensions and correspondingly different aperture measurements of the REMA diaphragm. There are no specific embodiment examples.
Highly developed REMA objectives are described in German Patent Application DE-A 195 48 805 and in the German Patent Application DE 196 53 983.8 of Carl Zeiss. They are suitable for cooperating with zoom-axicon illumination objectives according to European Patent EP-A 0 687 956 of Carl Zeiss, and for an arrangement of the REMA diaphragm at the exit of a glass rod according to U.S. Pat. No. 5,646,715. The cited applications of Carl Zeiss are incorporated by reference into the present application. These all have in common, with the present application, the co-inventor Wangler.
European Patent 0 500 393 B1 describes a microlithographic projection illumination system with variable quadrupole illumination, in which there is provided, between a honeycomb condenser and the reticle mask, an optics with the possibility of adjustment in order to adjust the uniformity of illumination. Since the skilled person is given in this patent only functional optical groups in the nature of block diagrams, but not a specific embodiment example, this disclosure has more of a functional character.
U.S. Pat. No. 5,311,362 describes a microlithographic projection illumination system with variable numerical aperture of the illumination system, in which the numerical aperture of the projection objective is also variable and an optical path length between lenses of the projection objective can be varied in dependence on the two numerical apertures, whereby aberrations, primarily the vertical spherical aberration, are corrected.
In general, various embodiments of projection objectives with adjusting means for the correction of variable imaging errors are known.
SUMMARY OF THE PRESENT INVENTION
The present invention has as its object to improve an illumination system such that optimum uniformity, i.e. regularity of the illumination over the whole surface of the wafer, is attained. This is to hold for the most diverse disturbing influences which can also arise with variable aperture of the illumination as regards numerical aperture and shape of aperture such a circle, ring, or quadrupole.
This object is attained by means of an illumination system in which a secondary light source is imaged on a reticle and distortion of the image of the secondary light source is adjusted by adjusting at least one variable optical path between optical elements or by a REMA objective. This object is also achieved by a REMA objective comprising optical elements, in which the optical path between two optical elements is adjustable. The object of the invention is also achieved by an operating process comprising changing at least one optical path between two optical elements and the REMA objective in dependence on the variable aperture of the illumination system.
For the first time, the distortion of the illumination is thus adjustably provided, and hence control and regulation of the uniformity of the illumination is derived.
Likewise for the first time, adjustment is provided in a REMA objective.
REFERENCES:
patent: 4851882 (1989-07-01), Takahashi et al.
patent: 5666206 (1997-09-01), Uchiyama
patent: 5739899 (1998-04-01), Nishi et al.
patent: 5982558 (1999-11-01), Furter et al.
patent: 6028660 (2000-02-01), Van Der Laan et al.
patent: 0 811 865 A2 (1997-10-01), None
patent: 8-316123 (1996-11-01), None
Schultz Jörg
Wangler Johannes
LeRoux E.
Metjahic Safet
Zeiss Carl
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