Experimental evaluation of an optimized radiation cooling geometry for ionprojection lithography masks

In this article, we study an optimized radiative cooling geometry for ion p rojection lithography masks. In this design, a polished infrared mirror gui des radiation from the mask to a high-emissivity cooled-cylinder positioned about 0.5 m away. Previous finite element modeling of this system predicts thermal distortion below I nm for practical mask designs. This is the firs t experimental study of the design. We show, by measuring the mean mask str ess as a function of cooled cylinder temperature, that radiative cooling ba lances beam heating, with a power density of 2.15 mW/cm(2), when the cooled cylinder is held at 15 degreesC and the temperature of the mirror and mask frame are at 25 degreesC. The results agree with finite element modeling. (C) 2000 American Vacuum Society. [S0734-211X(00)02306-4].