US 9,810,991 B2
System and method for cleaning EUV optical elements
Frank Chilese, San Ramon, CA (US); Gildardo Delgado, Livermore, CA (US); and Rudy F. Garcia, Union City, CA (US)
Assigned to KLA-Tencor Corporation, Milpitas, CA (US)
Filed by KLA-Tencor Corporation, Milpitas, CA (US)
Filed on Dec. 19, 2014, as Appl. No. 14/578,301.
Claims priority of provisional application 61/919,816, filed on Dec. 23, 2013.
Prior Publication US 2015/0253675 A1, Sep. 10, 2015
Int. Cl. G03B 27/52 (2006.01); G03F 7/20 (2006.01)
CPC G03F 7/70033 (2013.01) [G03F 7/70925 (2013.01); G03F 7/70933 (2013.01)] 21 Claims
OG exemplary drawing
 
1. An optical system comprising:
an illumination source configured to generate light;
a detector;
a first set of optical elements configured to direct at least a portion of the light to one or more specimens;
a second set of optical elements configured to receive illumination from the surface of the one or more specimens and direct the illumination from the one or more specimens to the detector; and
one or more vacuum chambers, wherein at least one of the first set of optical elements or the second set of optical elements are disposed in the one or more vacuum chambers, wherein the one or more vacuum chambers are configured to contain a selected purge gas ionizable by the light emitted by the illumination source,
wherein at least one of the first set of optical elements or the second set of optical elements comprises an electrically biased optical element including a negatively charged reflective surface to attract one or more positively charged ionic species of the selected purge gas to the negatively charged reflective surface in order to clean contaminants from the negatively charged reflective surface.