Optical: systems and elements – Single channel simultaneously to or from plural channels – By surface composed of lenticular elements
Reexamination Certificate
1999-11-29
2001-06-05
Ben, Loha (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By surface composed of lenticular elements
C359S623000, C359S710000, C355S053000, C355S067000, C362S268000
Reexamination Certificate
active
06243206
ABSTRACT:
BACKGROUND OF THE INVENTION
The 157 nm technology on the basis of the F
2
excimer laser proceeds from the development of the microlithographic projection illumination apparatus for using ever lower light wavelengths. This 157 nm technology has been under development for some time.
In the deep ultraviolet range, experience with suitable illuminating systems is already present with different components and functions which are also necessary for the 157 nm technology in order to illuminate a sufficiently large field homogeneously, telecentrically and with a selectable degree of coherence &sgr;.
A problem associated therewith is that the availability of transmitting materials is greatly limited. Only CaF
2
is already established as an optical material and is adequately permeable. Other fluorides are also known as being useable. However, attention has to be paid to minimalization of glass paths because the absorption is significantly higher compared to known deep ultraviolet systems and the resistance to radiation is reduced.
SUMMARY OF THE INVENTION
In view of the above, it is an object of the invention to provide an illuminating system which satisfies these various requirements in the vacuum ultraviolet range.
The illuminating system for vacuum ultraviolet microlithography of the invention includes: a vacuum ultraviolet light source; at least one refractive optical element of a fluoride; at least one microlens array defining a light-conductance value increasing unit; and, at least one honeycomb condenser.
German patent publication 195 20 563 A1 corresponds to United States patent application Ser. No. 08/658,605, filed on Jun. 5, 1996, and abandoned in favor of continuation application Ser. No. 09/315,267, filed May 20, 1999, and discloses an illuminating arrangement for a projection microlithographic apparatus in the deep ultraviolet range and is incorporated herein by reference. The present invention builds upon the teaching in this application but departs therefrom for the light mixing element because the glass rod is long and therefore has high absorption. Instead of the glass rod preferred in the above application, the invention utilizes the honeycomb condenser known in other conventional illuminating systems.
REFERENCES:
patent: 5798866 (1998-08-01), De Vaan
patent: 5844727 (1998-12-01), Partlo
patent: 5959779 (1999-09-01), Yamazaki et al.
patent: 6061179 (2000-05-01), Inoguchi et al.
patent: 6100961 (2000-08-01), Shiraishi et al.
“Cylindrical lens arrays homogenize excimer beam” by Y. A. Carts, Laser Focus World, Nov. 1991.
Ben Loha
Carl-Zeiss-Stiftung
Ottesen Walter
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