Cleaning and liquid contact with solids – Processes – Including application of electrical radiant or wave energy...
Reexamination Certificate
1999-01-27
2001-02-27
Markoff, Alexander (Department: 1746)
Cleaning and liquid contact with solids
Processes
Including application of electrical radiant or wave energy...
C134S001100, C134S902000
Reexamination Certificate
active
06192897
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to lithography systems, particularly to removing hydrocarbon contamination emanating from a resist coated wafer under radiation exposure, and more particularly to an apparatus and method for cleaning resist outgassing windows.
In lithography systems involving radiation (photons, electrons) of resist coated wafers, resist outgassing would contaminate lithographic optical components with highly absorbing carbonaceous material, unless such contamination is intercepted. One means for physically intercepting hydrocarbon contamination emanating from a resist coated wafer under radiation exposure is to provide a resist outgassing window which is capable of transmitting the lithographic radiation while physically intercepting the hydrocarbon contamination. The problem associated with the use of resist outgassing windows is that as hydrocarbon contamination from resist outgassing builds up on the window, the window's transmission becomes degraded, eventually to an unacceptable level. This resist-outgassing problem will become more acute with the next generation lithography systems, such as the extreme ultraviolet (EUV), Scattering with Anguler Limitation Projection Electron Lithography (SCALPEL), and the 193 nm lithography systems. Thus, there is a need in the art for an effective means to clean the contamination from the window without physically removing the window from the lithographic tool. An ideal method would continuously clean the window during lithographic operation. A less ideal, but still desirable, method would permit in-situ cleaning of the window in a maintenance period (not during lithographic operation) without removal of the window.
The present invention is directed to a solution of the hydrocarbon contamination problem, and involves an apparatus and method which enables in-situ cleaning of resist outgassing windows during lithographic operation or during a maintenance period without removing the window. The present invention permits removal of hydrocarbon contamination from resist outgassing windows in a highly flexible manner, and is compatible with windows made of any material.
SUMMARY OF THE INVENTION
It is an object of the present invention to prevent contamination of lithographic optical components with highly absorbing carbonaceous material.
A further object of the invention is to physically intercept hydrocarbon contamination emanating from a resist coated wafer under radiation exposure.
A further object of the invention is to provide a resist outgassing window for a lithographic system that can be cleaned without removal.
Another object of the invention is to provide an apparatus for cleaning hydrocarbon contamination from a resist outgassing window.
Another object of the invention is to provide a method for cleaning resist outgassing windows.
Another object of the invention is to provide a method for removing hydrocarbon contamination from a resist outgassing window during operation or non-operation of the lithographic tool.
Other objects and advantages of the present invention will become apparent from the following description and accompanying drawing. The invention involves an apparatus and method for intercepting hydrocarbon contamination emanating from a resist coated wafer under radiation exposure and for removing the intercepted contamination. The apparatus and method of this invention involves the use of a resist outgassing window located in a chamber having electrodes mounted therein and being supplied with a gas, whereby contamination can be removed from the window during transmission of lithographic radiation therethrough or during time periods of no radiation transmission though the window. The apparatus and method of the present invention is described with respect to cleaning a resist outgassing window for EUV lithography, but the approach can be used for other lithographic systems, such as the next-generation 193 nm and SCALPEL systems. The apparatus, located in a lithographic tool, utilizes a chamber in which the resist outgassing window is mounted on a slot in the chamber opposite the window to enable transmission of radiation through the window, chamber, and onto a resist-coated wafer. The chamber includes spaced electrodes, a filament, and a gas inlet whereby the voltage across the chamber and the gas type in the chamber can be changed or controlled, which enables cleaning of the window to be carried out during operation or non-operation of the lithographic tool without removal of the window. The chamber may be surrounded by conductance-limiting structures that prevent gas transport from the slot in the chamber to the region above the window.
REFERENCES:
patent: 5003178 (1991-03-01), Livesay
patent: 5714306 (1998-02-01), Komatsu et al.
patent: 5863706 (1999-01-01), Komatsu et al.
patent: 5932966 (1999-08-01), Schneider et al.
patent: 6031598 (2000-02-01), Tichenor et al.
Haney Steven J.
Klebanoff Leonard E.
Carnahan L. E.
EUV LLC
Markoff Alexander
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